OCS Study

BOEM 2020-034

U.S. Department of the Interior

Bureau of Ocean Energy Management

New Orleans Office

Investigation of an 

Ancient Bald Cypress Forest in

the Northern Gulf of Mexico
OCS Study

BOEM 2020-034

Published by

U.S. Department of the Interior

Bureau of Ocean Energy Management

New Orleans Office

New Orleans, LA

June 2020

Investigation of an 

Ancient Bald Cypress Forest in

the Northern Gulf of Mexico 

Authors

Kristine L. DeLong

Samuel J. Bentley, Sr.

Kehui Xu

Grant L. Harley

Carl Andy Reese

Jeffrey B. Obelcz

Suyapa Gonzalez

Jonathan T. Troung

Prepared under BOEM Award 

M15AC00016

by

Louisiana State University

227 Howe-Russell-Kniffen Geoscience Complex

Baton Rouge, LA 70803
i

DISCLAIMER

Study collaboration and funding were provided by the US Department of the Interior, Bureau of Ocean 

Energy Management (BOEM), Environmental Studies Program, Washington, DC, under Agreement 

Number M15AC00016. This report has been technically reviewed by BOEM, and it has been approved 

for publication. The views and conclusions contained in this document are those of the authors and should 

not be interpreted as representing the opinions or policies of BOEM, nor does mention of trade names or 

commercial products constitute endorsement or recommendation for use.

REPORT AVAILABILITY

To download a PDF file of this report, go to the US Department of the Interior, Bureau of Ocean Energy 

Management Data and Information Systems webpage (http://www.boem.gov/Environmental-StudiesEnvData/), click on the link for the Environmental Studies Program Information System (ESPIS) and 

search on 2020-034.

CITATION

DeLong KL, Bentley Sr SJ, Xu K, Harely GL, Reese CA, Obelcz J, Gonzalez S, Truong JT. 2020. 

Investigation of an ancient bald cypress forest in the Northern Gulf of Mexico. New Orleans 

(LA): US Department of the Interior, Bureau of Ocean Energy Management. 108 p. Agreement 

No.: M15AC00016. Report No.: 2020-034

ABOUT THE COVER

The cover photo is LeFleur's Bluff State Park in Mississippi on December 8, 2017 by Abby Braman of 

Peace Riverkeepers; used with permission.
ii

Acknowledgments

Funding for this study was provided by the US Department of the Interior, Bureau of Ocean Energy 

Management (BOEM), Washington, DC, under Coastal Marine Institute Cooperative Agreement Number 

M15AC00016. We are deeply thankful to BOEM Program Officer Alicia Caporaso for her guidance, 

insight, and participation in this project.

This project would not be possible without our wonderful students who participated in many aspects of 

this project. Jeffery Obelcz, Suyapa Gonzalez, and Jonathan Truong are acknowledged for their 

achievements in this project as part of the research program for their degrees at Louisiana State University

(LSU). We thank students Rodney Stieffel, Brianna Crenshaw, Jeff Duxbury, Haoran Liu, Patrick 

Robichaux, Johnny Ryu, and Robin Cobb for their help during fieldwork and Kaleb Robertson for his lab 

work with the seeds in the sediment cores. We thank Clay Tucker for his help with tree samples, his work 

on the modern flood analogs, and discussions on the bald cypress analyses.

We also like to thank the crew of the R/V Coastal Profiler, Captain Chris Cleaver and First Mate Charlie 

Sibley, as well as Bill Gibson and support staff of the Coastal Studies Institute at Louisiana State 

University. The LSU Museum of Natural History: Section of Fossil Protists and Invertebrates for the use 

of their foraminiferal collection.

This project benefited from the expertise of many colleagues on the different aspects of this project, and 

we thank them all. Tom Guilderson of the Center for Accelerator Mass Spectrometry, Lawrence 

Livermore National Laboratory for his help with radiocarbon dating analysis and interpretations. 

Zhixiong Shen of Coastal Carolina University for his help with OSL dating. Beth Middleton of the US 

Geological Survey in Lafayette, Louisiana. for her expertise with seed samples. James Flocks of the US 

Geological Survey in St. Petersburg, Florida is thanked for providing vintage seismic data that aided 

CHIRP data interpretation. We thank Mike Ewing for his help with the pollen diagram as well as for 

useful discussion on pollen results. We thank River Shen and Hsun Ming for their work on U-Th dating 

the wood samples. We thank the University of Southern Mississippi Department of Marine Science, in 

particular Davin Wallace, for his insights and knowledge of the study area, and David Dodd and Monty 

Graham for their initial geophysical survey of the site in 2012.

Last, we thank the people for whom this project would not have been possible. Ben Raines for his local 

expertise on the ancient tree site, for his public outreach efforts, and the “The Underwater Forest” 

documentary. Chas Broughton for his diving expertise and local knowledge on the site. We thank the 

Wallace Foundation for providing the initial seed money to start this project allowing us to conduct the 

first dives on the site, for the initial radiocarbon dating of the wood, and fieldwork with the R/V Coastal 

Profiler.
iii

Contents

Acknowledgments ...................................................................................................................................... ii

List of Figures ............................................................................................................................................. v

List of Tables ..............................................................................................................................................vi

Abbreviations and Acronyms ..................................................................................................................vii

1 Introduction .............................................................................................................................................. 9

1.1 The Location and Its History ..............................................................................................................................12

1.2 Biogeography of Bald Cypress ..........................................................................................................................16

1.3 An Archive of Past Environmental and Climatic Change ...................................................................................17

1.4 Project Goals .....................................................................................................................................................18

1.5 Study Approach .................................................................................................................................................19

1.6 Team Organization ............................................................................................................................................20

2. Field and Laboratory Methods.............................................................................................................21

2.1 Previous Fieldwork ............................................................................................................................................21

2.2 Field Methods ....................................................................................................................................................21

2.2.1 Geophysical Surveys..................................................................................................................................22

2.2.2 Vibracoring .................................................................................................................................................24

2.3 Laboratory Methods...........................................................................................................................................25

2.3.1 Geophysical Data Processing ....................................................................................................................25

2.3.2 Core, Sediment, and Microfossil Analyses .................................................................................................25

2.3.3 Macro Botanical Analysis ...........................................................................................................................28

2.3.4 Dating of Sediments and Wood..................................................................................................................29

3. Results ...................................................................................................................................................31

3.1 Geophysical.......................................................................................................................................................31

3.2 Physical Properties of the Sediments ................................................................................................................24

3.3 Dating ................................................................................................................................................................31

3.3.1 Radiocarbon Dating....................................................................................................................................31

3.3.2 Optically Stimulated Luminescence Dating ................................................................................................34

3.4 Micropaleontological Analyses...........................................................................................................................37

3.4.1 Pollen .........................................................................................................................................................37

3.4.2 Foraminifera ...............................................................................................................................................39

3.4.3 Seeds .........................................................................................................................................................41

3.5 Wood and Dendrochronology ............................................................................................................................42

3.6 Facies ................................................................................................................................................................45

3.7 Integrated Site Model.........................................................................................................................................49

4. Discussion .............................................................................................................................................52

4.1 Geophysics........................................................................................................................................................52

4.2 Paleoenvironmental Interpretation.....................................................................................................................54

4.2.1 Pollen .........................................................................................................................................................54
iv

4.3.2 Wood..........................................................................................................................................................55

4.3 Regional Stratigraphy ........................................................................................................................................58

4.3.1 Foraminiferal-Environment Interpretation ...................................................................................................58

4.3.2 Depth-Age Relations and Lateral Correlation.............................................................................................61

4.4 Site Characteristics for Preservation..................................................................................................................63

4.5 Role of Sea Level Change in Forest Preservation.............................................................................................67

4.6 Implications of Forest Model for Analogous Sites..............................................................................................75

5. Future Plans ..........................................................................................................................................77

Works Cited ...............................................................................................................................................80

Appendix A: Full foraminiferal counts from core 15DF1 ......................................................................92
v

List of Figures

Figure 1. Preliminary multi-beam bathymetry image of the site..................................................................10

Figure 2. Underwater tree stump exposed in the study site. ......................................................................10

Figure 3. Global sea-level variations for the last glacial interval.................................................................11

Figure 4. Northern Gulf continental shelf and study site location. ..............................................................13

Figure 5. Map of Alabama inner continental shelf. .....................................................................................15

Figure 6. Biogeography of Taxodium..........................................................................................................17

Figure 7. Fieldwork on the R/V Coastal Profiler..........................................................................................22

Figure 8. Field survey lines for 2016...........................................................................................................23

Figure 9. Micropaleontological and radiocarbon sample locations for core 15DF1....................................27

Figure 10. Three-dimensional digital elevation model of 2015 and 2016 bathymetric data. ......................20

Figure 11. Side-scan sonar mosaic illustrating seafloor sediment texture variation...................................21

Figure 12. The thickness of Holocene sand sheet in the study area..........................................................22

Figure 13. Three-dimensional fence diagrams of interpreted CHIRP data.................................................23

Figure 14. CHIRP sub-bottom profile along trough where wood was found...............................................24

Figure 15 Bathymetric map of study site with core locations......................................................................25

Figure 16. Grain size distributions for all cores...........................................................................................27

Figure 17. Comprehensive graphs for cores...............................................................................................30

Figure 18. Pollen assemblages for core 15DF1. ........................................................................................38

Figure 19. Foraminiferal assemblages for core 15DF1. .............................................................................40

Figure 20. Seeds preserved in peat section. ..............................................................................................41

Figure 21. Example of bald cypress thin section. .......................................................................................42

Figure 22. Wood collected by divers in 2013..............................................................................................43

Figure 23. Bald cypress sample with ring width measurements.................................................................44

Figure 24. Tree-ring index from wood collected at the study site. ..............................................................45

Figure 25. Examples of the five lithofacies. ................................................................................................46

Figure 26. Three-dimensional subsurface model of the study area............................................................50

Figure 27. The thickness of U2 in the study area. ......................................................................................51

Figure 28. CHIRP sub-bottom profile for B-B′.............................................................................................53

Figure 29. Gini coefficients for the glacial and modern bald cypress tree-ring indices. .............................56
vi

Figure 30. Spectral analyses of tree-ring indices........................................................................................57

Figure 31. An abbreviated chart of the foraminiferal and pollen assemblages for core 15DF1. ................60

Figure 32. Stratigraphic cross-section and map of study site.....................................................................62

Figure 33. East-West cross-section of the study area. ...............................................................................64

Figure 34. North-South cross-section of the study area. ............................................................................65

Figure 35. Forest growth conditions............................................................................................................67

Figure 36. Forest burial conditions..............................................................................................................68

Figure 37. Forest preservation conditions at the Last Glacial Maximum (LGM).........................................69

Figure 38. The working hypothesis of drowned forest current conditions. .................................................70

Figure 39. Profile synthesizing CHIRP and core data with forest facies and stratigraphy. ........................71

Figure 40. Geographical reconstruction of forest site evolution..................................................................73

Figure 41. Patterns of floodplain aggradation and degradation..................................................................75

Figure 42. Preliminary predictions of other locations with wood bearing sediments. .................................78

List of Tables

Table 1. Core Summary ..............................................................................................................................24

Table 2. Radiocarbon Results.....................................................................................................................32

Table 3. Optically Stimulated Luminescence Samples and Relevant Analytical Results...........................35

Table 4. U-Th Isotopic Compositions and 230Th Ages for Wood Samples..................................................36

Table 5. Preliminary Seeds Analysis in Core 15DF1..................................................................................41

Table 6. Facies Location and Depths for Sediment Cores .........................................................................47
vii

Abbreviations and Acronyms

Short Form Long Form

AMS accelerator mass spectrometry

~ approximately

BP Before Present (defined as 1950)

BOEM Bureau of Ocean Energy Management

cal calendar years

14C carbon-14 (radiocarbon) 

δ13C carbon stable isotopic ratio

CAMS Center for Accelerator Mass Spectrometry

cm centimeters

CE Common Era

DO Dansgaard Oeschger Event

DOG derivative of Gaussian

oC degrees Celsius

DEM digital elevation model

DF Drowned Forest

ENSO El Niño-Southern Oscillation

g grams

Gy Grays Equivalent dose of radiation

Gulf Gulf of Mexico

ha hectare

HE Heinrich Event

HS Holocene sand

HISM Holocene interbedded sand and mud

IGSN International Geo Sample Number

ITRDB International Tree-ring Data Bank

kHz kiloHertz

km kilometers

ka kiloannus

LGM Last Glacial Maximum

LPIMP Late Pleistocene Interbedded Mud and Peat

LPISM Late Pleistocene Interbedded Sand and Mud

LPP Late Pleistocene Paleosol

LOI loss on ignition

LSU Louisiana State University

MIS marine isotope stage

m meters

masl meters above sea level
viii

Short Form Long Form

mbsl meters below sea level

μm micrometers

mm millmeters

MS Mississippi

MAFLA Mississippi-Alabama-Florida

MSCL Multi-sensor core logger

MC-ICP-MS Multi-Collector Inductively Coupled Plasma Mass Spectrometer

NOAA National Oceanic and Atmospheric Administration

OSL Optically stimulated luminescence

OCS Outer continental shelf

PASC Pascagoula tree-ring chronology

% percentage

PI Principal Investigator

ppm parts per million

p probability

s second

sp. species

spp. multiple species

SFC Submerged Forest tree-ring chronology

SESAR System for Earth Sample Registration

3-D three-dimensional

2-D two-dimensional

U1 Unit 1

U2 Unit 2

USGS US Geological Survey

UI University of Idaho

USM University of Southern Mississippi

U-Th uranium-thorium
9

1 Introduction

In 2004, shortly after Hurricane Ivan had made landfall in Gulf Shores, Alabama, a fisherman found a 

location about 13 km offshore with abundant fish; he continued to fish at that location for the next several 

years. The fisherman asked a local dive shop owner to dive the site to see why so many fish were there. 

That diver descended to 18 m and discovered that the seafloor was covered with tree stumps rooted in 

their growth position (Raines 2017). Subsequently, in October 2012, an initial geophysical survey of the 

location was conducted by the University of Southern Mississippi (USM); it found an elongated 

depression in the seafloor (Figure 1). Members of this initial project dove the site in October 2013; they

found several previously buried logs and tree stumps emerging from a dark peat sediment ledge and

numerous fish swimming among the tree stumps. The divers counted more than 50 tree stumps, some up 

to 2 m in diameter, with visible buttresses and knees common to bald cypress trees (Figure 2a). The divers 

recovered several pieces of wood, and closer examination found the primary cellulose structure intact 

with no visible indications of permineralization or fossilization by replacement of cellulose with minerals, 

i.e., the first step in petrifying wood. The majority of the wood specimens retrieved by the divers in 2013 

were identified as bald cypress (Taxodium distichum [L.] Rich.), which is a long-lived tree species (up to 

2,624 years) (Stahle et al. 2019) that is commonly found in coastal and riparian ecosystems from Texas to 

Delaware.

In the marine and freshwater environments, wood rapidly decomposes due to bacteria, fungi, and woodboring organisms; finding a grove of tree stumps offshore was unexpected. Yet the preservation of woody 

material is possible in anoxic sediments and waters that limit biological organisms and so reduces

decomposition. Ancient wood has been found in anoxic peat bogs in freshwater environments (RamilRego et al. 1998, Stoll et al. 1994, Szumigalski and Bayley 1996, Wheeler and Proctor 2000) but wood is 

rarely preserved in the marine environment unless it is buried (e.g., Fojutowski et al. 2014) or in anoxic 

waters (e.g., Brennan et al. 2011). The pieces of wood recovered from the site have good preservation and 

smelled like freshly cut cypress when samples were removed for dating (see Figure 2b). Wood specimens 

that were fully exposed on the seafloor contain more marine boring organisms than those recovered from 

inside the sediment ledge. Some wood pieces recovered from the sediments still had bark and beetle 

chambers intact, suggesting quick burial and excellent preservation (Figure 2b). Initial radiocarbon dating 

of wood specimens collected by divers found that the trees were radiocarbon dead, that is, more than 

50,000 years old (i.e., the limit of radiocarbon dating). This suggests that these trees were alive when 

global sea level was lower than today, during the previous ice age 18,000 to 100,000 years ago when the 

northern Gulf of Mexico (Gulf) coastline was farther south than it is today (Figure 3).
10

Figure 1. Preliminary multi-beam bathymetry image of the site. 

Elevation scaled to 1:10.

Figure 2. Underwater tree stump exposed in the study site. 

(a) Underwater photograph of a bald cypress stump emerging from the sediments, taken by Ben Raines on October 

2013. (b) Well-preserved wood with bark intact recovered by divers in 2013.

a b Depth (m)
11

Figure 3. Global sea-level variations for the last glacial interval. 

Relative sea-level estimates below modern sea level (0 m) shown as a blue line with shaded area for minimum and 

maximum global sea level (Waelbroeck et al. 2002). Green circles and red squares are ages from radiocarbon and 

optically stimulated luminescence (OSL) dating (1σ error bars), respectively, for this study (Tables 2–3) with respect 

to dating sample depth below modern sea level. Marine Isotope Stage (MIS) numbers (Lisiecki and Raymo 2005)

appear along top.

Sedimentary strata exposed during long periods of lower sea level are commonly lost due to weathering 

and erosion. As a result, knowledge about glacial age sediments, geomorphology, climatic and 

environmental conditions, including sea-level fluctuations, are limited, particularly for the Gulf region 

because of the rarity of archives being preserved in such erosional settings. Therefore, preservation of this 

particular terrestrial deposit, preserved through a glacial cycle with more than 40,000 years of terrestrial 

erosive activity, represents a stratigraphic puzzle. Previous geological surveys of the area did not reveal 

any evidence of buried forests (Flocks et al. 2011), yet technological advances with geophysical data 

collection should provide evidence of the buried trees in the study area. Furthermore, geomorphology of 

the site and the sequence of events that needed to occur to preserve the wood and their coeval terrestrial 

sediments need to be defined and assessed. Also, this offshore forest discovery offers a unique 

opportunity to develop information on past environmental and climatic conditions in the Northern Gulf

region during the last glacial interval.
12

1.1 The Location and Its History

The study site is located 13.5 km south of Gulf Shores, Alabama; the area encompasses ~30,000 m2 of the 

northeastern Gulf continental shelf (Figure 4). The site is bounded to the north by the Alabama barrier 

islands, to the west by the St. Bernard Lobe of the Mississippi River Delta system and the Chandeleur 

Islands, to the east by the carbonate-ramp platform of the Florida Peninsula, and to the southeast by 

DeSoto Canyon. The width of the continental shelf thins from 200 km near the Chandeleur Islands to 50 

km near the Florida panhandle. The shelf south of Alabama receives a modest supply of terrigenous 

sediment mostly from nearby Mobile Bay and coastal barrier islands and spits (Otvos 1985). The site is 

located in water depths between 18 and 20 m and is near the transition between Transitional-Inner Shelf 

and Middle Shelf (Witrock et al. 2003) within the Mississippi-Alabama-Florida (MAFLA) sand sheet 

province of the Northern Gulf (Doyle and Sparks 1980; Mazzullo and Peterson 1989, McBride et al. 

1999). The MAFLA sand sheet was deposited over the seafloor in this area during the Holocene Epoch 

and exhibits a northwest-southeast shore-oblique ridge and trough morphology with relief up to 5 m 

(McBride et al. 1999). Below the MAFLA sand sheet is the Last Glacial Maximum (LGM) lowstand 

deeply incised valley carved out by the Mobile-Tensaw River system (Figure 5) (Anderson et al. 2004,

Bartek et al. 2004). The Northern Gulf Coast is microtidal with frequent tropical cyclones that can shift 

sediments on the shelf (Teague et al. 2006, Wang et al. 2005). In 2004, Hurricane Ivan was a Category 4 

hurricane in the Gulf producing extreme wave heights (largest was 27.7 m), resulting in substantial 

bottom scour (Teague et al. 2006; Wang et al. 2005) before making landfall in Gulf Shores (Figure 4). 

Because the study site was discovered soon after Ivan made landfall, it is assumed that the hurricane 

removed the overburden sand and exposed the Pleistocene Epoch sediments containing the stumps and 

wood.
13

Figure 4. Northern Gulf continental shelf and study site location. 

Location of the bald cypress stumps (red dot) is offshore of Alabama at ~18 m depth along the Northern Gulf of Mexico (Gulf); to protect the site, the exact location 

of stump exposure is not given. Bathymetric contours acquired from the Bureau of Ocean Energy Management (BOEM) with the path of Hurricane Ivan (red line) 

(Landsea and Franklin 2013) that passed within 10 km of the study site.
14

The Northern Gulf along the Alabama coast is described as a slowly subsiding, passive continental 

margin (Sydow and Roberts 1994). Glacio-isostatic uplift and subsidence rates are not known for the 

study site but are likely to be on the order of ±2 m during the last glacial interval (Blum et al. 2008). 

Global sea levels fell below the modern water depth of the study site during the interval from ~80 ka to 10 

ka (Figure 3), which is a much higher range (>100 m) than concurrent glacio-isostatic motions (Blum et 

al. 2008). This time interval represents a period when it was possible for the bald cypress forest to be 

alive as sea levels dropped (Figure 3), exposing the continental shelf as land, which is broad in the 

Northern Gulf, allowing terrestrial ecosystems to become established.

During the Pleistocene Epoch, the Gulf experienced multiple global glacioeustatic cycles driven by 

Milankovitch orbital modulations (Hays et al. 1976, Lobo and Ridente 2014) that caused global sea levels 

to fall by ~120 m compared to present (Donoghue 2011; Waelbroeck et al. 2002) (Figure 3). Extensive 

portions of the continental shelves were subaerially exposed at various times during the Pleistocene as sea 

levels responded to the growth of large continental ice sheets in North America, Europe, and Asia. Along 

the Northern Gulf coast, the combined effects of worldwide sea-level changes and collapse of the 

Laurentide ice sheet forebulge resulted in a series of marine shoreline advances and retreats. Offshore of 

Alabama, the most prominent geological features are the paleovalleys incised by the Pascagoula (west) 

and Mobile (east) rivers during glacial intervals (Figure 5) (Bartek et al. 2004). These valleys were 

initially carved during Marine Isotope Stage (MIS) 6 or 8 and were reoccupied by their respective rivers 

during the LGM (MIS 2) ~21,000 years ago (Bartek et al. 2004). The study site straddles the lateral 

boundary between the Mobile paleovalley and its western interfluve (Figure 5). There is no surficial 

expression of the paleovalleys today since they were infilled during and possibly after sea level 

transgression with a combination of deltaic, estuarine, and marine sediments (Kindinger et al. 1994). 

From MIS 5 to 2, sea level fell and allowed the ancestral Mobile-Tensaw River system to further incise 

and shape valley complexes (Bartek et al. 2004) (Figures 3, 5). As incision occurred during falling sea 

levels, the interfluve vegetation established on the newly exposed continental shelf landward from the 

basinward-shifting shoreline. This floodplain environment and its associated peat accumulations 

responded directly to base level change (Anderson et al. 2016, Fisk 1960, Shen et al. 2012). Modern 

swamps found in the southeastern US are dominated by T. distichum and Nyssa aquatica (tupelo-gum 

tree), and these wetlands frequently inhabit inland freshwater floodplains behind levees of distributary 

systems (Middleton and McKee 2004, Reese and Liu 2001).
15

Figure 5. Map of Alabama inner continental shelf. 

Bathymetry shown (shaded area) is a modern seafloor with northwest-southeast trending ridge and trough 

complexes. White contours are isopachs, modified from Bartek et al. (2004), showing the acoustic two-way travel 

time (in milliseconds) to the erosional base of the MIS 2 low stand that reveals the location of the Pascagoula and 

Mobile paleovalleys that crossed the shelf during the Last Glacial Maximum (LGM). Yellow line shows the path of 

Hurricane Ivan, which passed within 10 km west of the study site (red square).

Many Northern Gulf stratigraphic studies have focused on the Holocene evolution of Mobile Bay (e.g., 

Mars et al. 1992, Osterman and Smith 2012) but only a few have studied the Pleistocene-Holocene 

evolution of the MAFLA area (Bartek et al. 2004, McBride et al. 1999). Regional stratigraphy of the 

northeastern Gulf outer continental shelf (OCS) consists of Holocene sands with abundant shells, 

underlain by estuarine and other coastal deposits from the Holocene to Pleistocene (Bartek et al. 2004,

McBride et al. 1999, McBride and Byrnes 1995, McBride et al. 1996). Those studies described seven 

environmental facies (sand sheet, lower shoreface, central estuary or open bay, bay beach, lower bay 

shoreface, and two Pleistocene soil horizons) alongside two local erosional unconformities due to bay and 
16

shoreface ravinement. The study of McBride et al. (1999) identified four primary and eight secondary 

foraminiferal assemblages and interpreted environmental affiliations through multivariate analysis for the 

MAFLA region (see Table 1 in McBride et al. [1999]). The sand facies become finer (medium to fine) 

upwards in the sediments and westward across the MAFLA sand sheet (McBride et al. 1999). The 

Quaternary evolution of the MAFLA is largely tied to retention of sandy sediment discharged by small 

rivers, including the Pearl, Mobile, and Apalachicola rivers (Anderson et al. 2004). During sea-level high 

stands, these rivers’ sediment discharge was mostly confined to bays and the inner continental shelf. 

During glacial intervals, the depocenters shifted seaward with falling sea levels.

Preliminary analysis of a sediment core and geophysical data collected in 2012 and 2013 shows that the 

local stratigraphy is consistent with previous regional shelf-stratigraphic studies, consisting of a surface 

layer of Holocene sands overlying Pleistocene terrestrial and coastal deposits. However, the Pleistoceneaged, wood-bearing section of the cores recovered from the ancient forest site is composed of riverderived, back swamp, and deltaic plain muds, which differ considerably in both depositional environment 

and degree of environmental preservation, compared to previous studies (Bartek et al. 2004, McBride et 

al. 1999). Previous geological surveys of the general site area did not reveal any evidence of this buried 

bald cypress forest or any other types of buried forest (Bartek et al. 2004, McBride et al. 1999). This 

study examined and reconstructed the series of events that took place to allow the preservation of this 

unique Pleistocene-aged deposit and remnant forest.

1.2 Biogeography of Bald Cypress

Bald cypress (T. distichum) is found in riverine and swamp environments in seasonally inundated 

floodplains of the humid subtropics in the southeastern US where there is high precipitation (Conner and 

Toliver 1990, Doyle et al. 2015, Kennedy 1972, Little 1971, Wilhite and Toliver 1990). Bald cypress is 

an indicator species for coastal wetlands and swamps. It generally grows in areas less than 50 m above 

sea level (Doyle et al. 2015, Little 1971) but does occur at elevations up to 120 m in Texas and the along 

the Mississippi River (Figure 6). Bald cypress is not found in brackish or saline waters but is able to 

withstand modest short pulses of saltwater, thus these trees are subject to the effects of sea-level rise and 

increases in coastal flooding and salinity (Conner and Toliver 1990, Hook 1984, Middleton and McKee 

2004). Pond cypress (Taxodium ascendens) is considered a variety of T. distichum by some botanists; it

grows at altitudes up to 30 m in still blackwater rivers, ponds, and swamps without silt-rich flood deposits 

(Figure 6).

Based on the preferred habitats for bald cypress (low elevation freshwater floodplains), time frames can 

be identified for when this forest may have been alive by examining Holocene and Pleistocene global sealevel variations (Figure 2). Glacio-isostatic subsidence and uplift rates are not known for the study site but 

are likely to be on the order of ±2 m during the last glacial interval (Blum et al. 2008). Global sea levels 

fell below the modern water depth of the study site (18 m) during the interval from ~115 ka to 82 ka, and 

~80 ka to 10 ka, which has a range much greater (>100 m) than concurrent glacio-isostatic motions (Blum 

et al. 2008). Thus, these time intervals are possible intervals during which the glacial bald cypress forest 

may have been alive.

Bald cypress has been used for climate and environmental reconstructions through dendrochronology, the 

study of the annual growth rings in trees (Keim and Amos 2012, Stahle et al. 2012). Wood samples 

collected from exposed stumps by divers in 2013 have good preservation with cellular structure intact and 

smell like freshly cut cypress when sanded. The excellent condition of the recovered wood suggests that 

the forest was buried quickly and preserved in oxygen-free sediments for millennia, before the recent 

exhumation. These wood samples provide useful information about the climate and environment these 

trees lived in during the last glacial interval.
17

Figure 6. Biogeography of Taxodium

(a) Modern T. distichum tree distribution, modified from Doyle et al. (2015) based on Little (1971). Locations of MIS 

1–5 pollen and foraminifer reconstructions from NOAA Paleoclimate and Neotoma databases noted. The study site is 

13 km off the Alabama coast (black star). (b) Modern pond cypress (T. ascendens) distribution is 0–30 m in elevation 

in the southeastern range of T. distichum from Watson (1985) and Flora of North America Editorial Committee (1982).

1.3 An Archive of Past Environmental and Climatic Change

Trees, plants, plankton, and other organisms have specific temperatures, precipitation, and salinity 

requirements that are useful in biostratigraphy and paleontology, as well as for providing information 

about past environmental and climatic conditions. This information about the past is usually conveyed 

through pollen and planktonic remains because some combination of aerobic-anaerobic decomposition, 

early diagenesis, subaerial erosion, and sea-level transgressions generally result in the physical and 

chemical degradation of organic material. Pollen-based records and climate models conflict with each 

other with regard to the type of trees growing in the southeastern US during the last glacial interval 

(Webb et al. 1998). Preliminary wood, pollen, and sediment analyses of a sediment core collected at the 

site by divers in 2013 revealed that the site was once a wetland habitat with a vegetation community 

consisting of T. distichum and tupelo (Nyssa aquatic) trees, similar to current wetlands in the southeastern 

US.

There are few paleoclimatic and paleoenvironmental records preceding the LGM (MIS 3–5) for the 

northern Gulf coastal region and the southeastern US. This limits our understanding of glacial oceanicatmospheric interactions in this region during colder glacial conditions and how they may have shaped the 

past coastal environments. A climate model study of the MIS 4 found winter atmospheric circulation 

remained unchanged, but summers were influenced by the topography of the ice-sheets (Lofverstrom et 

al. 2014). Climatic shifts are known as Dansgaard-Oeschger (DO) events (Dansgaard et al. 1993); these

are abrupt and repeated warming climate shifts occurring during colder glacial intervals. Some of the 

colder glacial intervals are associated with ice-rafted debris in the North Atlantic known as Heinrich 

Events (HE) (Heinrich 1988), which caused extensive amounts of freshwater to be released from the 

a b
18

continental ice sheets into the North Atlantic. There is limited knowledge of DO-HE events in the 

southeastern US and how these fluctuations influenced coastal Gulf landscapes and climate because proxy 

records for the recent glacial interval are rare (e.g., Donders et al. 2011, Montero‐Serrano et al. 2011,

Nürnberg et al. 2008, Ziegler et al. 2008).

1.4 Project Goals

In recent decades, the Bureau of Ocean Energy Management (BOEM) has devoted considerable resources 

to carrying out its responsibilities to protect the nation’s natural, cultural, and heritage resources from 

bureau-permitted activities as per the National Historic Preservation Act of 1966 and the National 

Environmental Policy Act of 1969. However, there is a gap in understanding how the presence of 

preserved landscapes–such as buried wetland forests and marshlands, which contain valuable information 

of past ecosystems, climate, and physical geology and geography–fit within this realm and how the 

geological and geophysical characteristics of these formerly terrestrial habitats interplay with BOEM’s

OCS management needs and objectives. Information that the project gathered and refined about the 

geological, geophysical, ecological, and paleo-environmental characteristics of this glacial-age forest 

preserved on the OCS is valuable to BOEM for making responsible environmental decisions for proposed 

oil, gas, and other activities on the OCS (e.g., Research Planning Inc. 2004). The project’s overarching 

goal was to document the well-preserved bald cypress forest buried in the sediments in the Northern Gulf

continental shelf and to develop a model for other potential sites that could contain preserved wood on 

millennial and longer time scales. This study aimed to provide valuable information on Northern Gulf

coastal geomorphology, sediment preservation of macro- and micro botanicals, and the glacial age 

environment. By placing the site within the sedimentological context of the Northern Gulf, the main goals 

of this study included:

(1) Determine the preservation characteristics of the site;

(2) Provide a better understanding of the depositional and geomorphic layout of the site; and

(3) Develop a model to predict other preserved paleo-forest sites in the Northern Gulf and OCS.

To address these goals and further explore this unique site, we pursued the following objectives:

Objective 1: Establish a method for identifying buried tree stumps in submerged sediments;

Objective 2: Map the exposed submerged tree site and adjacent areas;

Objective 3: Document and characterize the sediment and depositional environment encompassing 

the tree remains;

Objective 4: Establish a chronology for the age and formation of the site;

Objective 5: Provide information on the depositional history and geomorphology of the site;

Objective 6: Develop a model to predict other buried forest sites on the OCS;

Objective 7: Catalog and determine the potential for ecological and archaeological resource 

preservation at this site type; and

Objective 8: Place the submerged forest landscape in the context of the Northern Gulf shelf evolution 

with changes in sea level.
19

1.5 Study Approach

The research was conducted by an interdisciplinary team consisting of two geological oceanographers 

(Kehui Xu and Samuel Bentley) with expertise in geoacoustics, coastal geological oceanography, and 

coastal sediment dynamics, three paleoclimatologists (Kristine DeLong, Grant Harley, and Andy Reese) 

with expertise in the coastal Gulf region, tree-rings, and pollen used to reconstruct past vegetation and 

climate, and one marine archaeologist (Alicia Caporaso). The Principal Investigator (PI) team supervised 

graduate and undergraduate students working on different aspects of the project, including Jeffrey Obelcz, 

Suyapa Gonzalez, Jonathan Truong, Johnny Ryu, Clay Tucker, and Caroline Miles. The project resulted 

in one undergraduate honors thesis, two master’s theses, and one doctoral dissertation by the students 

working on the project. Zhixiong Shen of Coastal Carolina University performed the OSL dating. Beth 

Middleton of the US Geological Survey (USGS) in Lafayette, Louisiana aided with seed samples found in 

the sediments. Ben Raines, a local reporter and diver with extensive knowledge on the site and has led the 

site conservation efforts for the past nine years, provided additional local expertise.

Previous geological surveys of the Northern Gulf of Mexico OCS did not reveal any evidence of buried 

forests (Flocks et al. 2011). This may have been due to the survey methods and technology used. 

However, technological advances with geophysical instrumentation could provide the technology needed 

to map the buried trees in the study area. The study of Plets et al. (2009) used a sub-bottom profiler to 

successfully image buried wooden shipwrecks using a 1.5 to 13 kHz linearly swept acoustic pulse, which 

is similar to the frequency of the Edgetech 2000 system used in this study. Field methods included

conducting geophysical surveys and collecting new sediment cores from the site area. Field operations 

were conducted in August 2015 and July 2016. The 2015 fieldwork concentrated at the main site where 

trees were exposed in the depression while the 2016 fieldwork focused on the finer scale geophysical 

surveys at the main site and areas to the east and south of the tree exposure site. Sediment cores were 

collected in and adjacent to the main site area in 2015, and replicate cores for OSL dating were collected 

in 2016. The cores were analyzed to characterize the sediments at the site, build stratigraphic relationships 

with the samples dating using radiometric and OSL methods, and to understand paleoenvironmental 

conditions.

Laboratory methods included core logging and descriptions, organic content determinations (loss on 

ignition), and pollen, and microfossil analyses. Wood samples collected from the site were shared 

between Louisiana State University (LSU), USM, and the University of Idaho (UI) for analysis. 

Geophysical data collected during field operations were processed and analyzed by PIs Xu and Bentley 

and their students. Sediment cores were analyzed by PIs Bentley, Xu, DeLong, and Reese and their 

students for core logging, and analysis of sediment, pollen, seeds, and microfossils.

The project resulted in two publications submitted to peer-reviewed journals for publication. The first 

publication described the longest sediment core collected in 2015 that contains the wood-bearing 

sediments (Gonzalez et al. 2017) and the second paper described the pollen results from that core (Reese 

et al. 2018). A paper detailing the dendrochronology results is in preparation. A second paper combining 

the theses and dissertation work from the three students (Obelcz; Truong; Gonzalez) on the microfossil 

assemblages, the stratigraphy of cores 15DF1 and 15DF3, dating results, the sedimentological analysis of 

the other 17 sediment cores collected, and a hypothesis for the site’s evolution is also in preparation. The 

results from these papers are summarized in this final report. Additional data analyses and information not 

included in one of the above publications are presented and discussed in this report.
20

1.6 Team Organization

The organization of the study team from LSU, USM, and UI consisted of the following key personnel 

fulfilling the listed roles:

Kristine L. DeLong, Department of Geography and Anthropology and Coastal Studies Institute, LSU. 

Principal investigator with expertise in the coastal Gulf paleoclimate, and lead author of the final report.

Kehui Xu, Department of Oceanography and Coastal Sciences, and Coastal Studies Institute, LSU. CoPrincipal investigator leading geophysical data collection and processing, and co-author of the final 

report.

Samuel J. Bentley, Sr., Vice President, Office of Research and Economic Development, Department of 

Geology and Geophysics and Coastal Studies Institute, LSU. Co-Principal investigator leading coring, 

grain size analysis, core logging, and stratigraphy, and co-author of the final report.

Grant L. Harley, Department of Geography and Geology, USM, now at the UI Department of 

Geography. Co-Principal investigator leading dendrochronology, paleoclimate, and biogeography, and 

co-author of the final report.

Carl Andy Reese, Department of Geography and Geology, USM. Co-Principal investigator leading 

palynology, paleoclimate, and paleoenvironments, and co-author of the final report.

Jeffrey B. Obelcz, PhD student, Department of Oceanography and Coastal Sciences, advised by Xu, now 

at the US Naval Research Laboratory, Stennis Space Center, Mississippi. Collaborator with expertise in 

geophysical methods and coastal geology, and co-author of the final report.

Suyapa Gonzalez, Undergraduate and Master’s degree student, Department of Geology and Geophysics, 

advised by Bentley. Collaborator with expertise in sediment core descriptions and coastal geology, and 

co-author of the final report.

Jonathan T. Truong, Master’s degree student, Department of Geology and Geophysics, advised by 

Bentley and DeLong. Collaborator with expertise in microfossils, Petrel software, and co-author of the 

final report.
21

2. Field and Laboratory Methods

2.1 Previous Fieldwork

In November 2012, initial survey with multi-beam and side-scan sonar were arranged by Ben Raines and 

conducted by the University of Southern Mississippi (USM) Department of Marine Science with DeLong 

on board (Figure 1). That survey revealed that the site contained a 1.2 m deep depression and a 408-mlong channel. The initial side-scan sonar and multi-beam survey provided a view of the site bathymetry, 

but individual tree stumps were difficult to identify.

In October 2013, DeLong and Harley conducted diving operations for two days. This fieldwork was 

funded by a private grant from the Wallace Research Foundation. The Weeks Bay Foundation, Ben 

Raines, and Chas Broughton provided diver expertise at the site and additional divers to support 

fieldwork efforts. This fieldwork was documented by Ben Raines and appeared in his documentary “The 

Underwater Forest” (Raines 2017).

During the 2013 fieldwork, DeLong and Harley recovered 23 specimens of wood from the site and a push 

core near the ledge where the wood was exposed. That core contained grayish-brown clays with remnant 

wood. The sediment ledge was not consolidated and was easily eroded. The divers who found the site 

have reported some shifts in the ledge to the east, indicating ongoing erosion. The outlines of several bald 

cypress stumps were observed in the flat portion of the seafloor adjacent to the ledge and are neither

exposed vertically nor resolved in the 2012 geophysical survey. These stumps are assumed to be well 

preserved because only the tops of the stumps are partially exposed and covered with a thin layer of sand. 

One tree core was recovered using an increment borer on a stump partially exposed from the sediment 

ledge in its original growth position. This core was bagged on the boat to prevent contamination. To 

ensure the acquisition of intact subfossil segments, specimens were collected that exhibited the least 

amount of visible degradation. Wood specimens were sent to the surface in buckets with air-lift bags,

tagged with a unique identification number, submerged in deionized water to prohibit desiccation and 

subsequent degradation, and transported back to the laboratory at USM. Some wood specimens were cut 

into smaller pieces and those subsections were transported to Louisiana State University (LSU). Unburied 

wood recovered from the base of the hole contained numerous marine wood-boring organisms whereas 

buried wood extracted from the sediment ledge had little evidence of marine decomposition and woodboring organisms. Some wood specimens recovered from the sediments still had intact bark (Figure 2b) 

with clear branching nodes and evidence of beetle chambers, suggesting quick burial and preservation in 

anoxic sediments. The large wood specimens were cut, producing the characteristic odor of fresh-cut 

cypress—a sensory confirmation of well-preserved and unaltered wood. The Lawrence Livermore 

National Laboratory Center for Accelerator Mass Spectrometer conducted radiocarbon analysis in August 

2014 of 12 wood subsamples including the tree core recovered from the in situ stump.

2.2 Field Methods

The primary objective of the fieldwork was to collect geophysical data and sediment cores from the stump 

exposure depression and adjacent areas. All fieldwork was conducted in 2015 and 2016 from the R/V 

Coastal Profiler, owned by LSU’s Coastal Studies Institute. In both years, geophysical surveys were 

completed on the first day, and coring operations on the second day after review of the geophysical 

survey’s preliminary results. Ben Raines filmed the 2015 fieldwork for his documentary.
22

2.2.1 Geophysical Surveys

Geophysical data collected during fieldwork used an Edgetech 512i CHIRP sub-bottom sonar, side-scan 

sonar, and sub-bottom profiler (~0.3 m vertical resolution, 1–2 m horizontal resolution), Edgetech 4600 

multibeam and side-scan sonar (~2.5 mm vertical resolution, 1 m2 horizontal resolution with a 540-kHz 

transducer), Edgetech DS2000 combined CHIRP sub-bottom and side-scan unit (in 2016 only), Valeport 

sound velocity profiler, Hemisphere Differential GPS/SMC motion compensation system, and a 

Geometrics G882 magnetometer (Figure 7). The Edgetech 4600 produces high-resolution threedimensional (3-D) maps of the seafloor while providing co-registered simultaneous side-scan 

(backscatter) data. The vertical sub-bottom resolution of the Edgetech DS2000 is approximately 0.1 m, 

more than ten times smaller than the 2-m x 1-m tree stumps. A magnetometer was used to detect any 

potential metal or ferrous objects in the area. Ultimately, neither the Edgetech DS2000 data nor the 

magnetometer data was used in this study, but a pipeline and a metal object were detected by 

magnetometer and side-scan sonar in the eastern survey area.

Figure 7. Fieldwork on the R/V Coastal Profiler. 

The Edgetech DS2000 being deployed (a) and the submersible vibracorer during transit (b).

Survey line of 75 m and 100 m in strike and dip orientation, respectively, provided ~50 to 100% swath 

overlap of the bathymetric data. This survey methodology yielded continuously generated bathymetric 

digital elevation models (DEMs), backscatter maps, and a dense grid of two-dimensional (2-D) seismic 

reflection profiles imaging the top 10 to 20 m of the seafloor subsurface. Perpendicular survey lines 

a b

b
23

provided different approach directions, which is helpful in buried object identification. In 2016, three sites 

were surveyed: a return to the trough (2015 site) with tighter grid spacing for high resolution imagery, and 

two separate grids were surveyed to expand the surveying area further to the south and the east (Figure 8). 

The resurvey of the 2015 area used tighter line spacing, slower boat speed (<5 knots), and a high ping rate 

to maximize horizontal resolution of the trough.

Data were collected using Edgetech Discover software (side-scan and CHIRP) and Hypack Hysweep 

software (swath bathymetry). Surficial data (bathymetry, backscatter) were processed with Caris HIPS 

and SIPS version 9.0 and imported into ESRI ArcGIS® for analysis; sub-bottom data were processed

using SIOSEIS version 2014.2.1 and imported into IHS Kingdom Suite and QPS Fledermaus for analysis 

and interpretation.

Figure 8. Field survey lines for 2016. 

Red lines are actual survey lines shown on top of bathymetry and site map. Circles note locations of cores collected 

in 2016.
24

2.2.2 Vibracoring

Vibracores were collected using 6-m-long, 75-mm-diameter aluminum tubing attached to a vibrating head 

encapsulated within a steel tripod deployed from the R/V Coastal Profiler (Figure 7). The submersible 

vibracoring system was lowered onto the seafloor in water depths ranging from 14 m to 18 m and 

operated until subsurface penetration ceased. Sediment cores were collected at locations around the 

sediment ledge, inside the depression, and to the east and south of the ledge where modern sediments are 

present. Core sediment samples were collected to target specific features of interest (e.g., peat, stumps, 

and sediment ledge) while avoiding any identified stumps, wood, or pipelines. Locations for coring 

operations were determined in the field using real-time evaluation of geophysical data from the previous 

day and the USM multi-beam survey (Figure 1). Sediment cores were cut into up to 1.5-mm-long sections 

onboard, labeled, and sealed with tape for transport to LSU. In 2016, two cores were collected at each 

location (five locations in total), one core for the core scanner and the other core for optically stimulated 

luminescence (OSL) dating. All 2016 cores were wrapped in black plastic bags to limit sunlight 

penetration, which could affect OSL dating. Sediment trapped in core catchers was stored in Whirl Pak 

bags and retained for botanical and microfossil analysis. Field notes recorded core location, core length, 

and field observation of core sediments. Cores were transported back to LSU in the vertical position to 

preserve core integrity. All cores were registered in System for Earth Sample Registration (SESAR) and 

given an International Geo Sample Number (IGSN) (Table 1).

Table 1. Core Summary

Core ID 1 Alternate

core ID

Year

collected

IGSN 2 Depth

(mbsl) 3

Length

(m)

Dating # of 

sections

16DF1B 16DF-1-b 2016 IEADF161B 15.3 0.925 1

16DF1C 16DF-1-c 2016 IEADF161C 15.3 1.71 1

16DF1D 16DF1-d 2016 IEADF161D 15.3 3.97 4

16DF3A 16DF-3-a 2016 IEADF163A 16.8 2.32 OSL 2

16DF3B 16DF-3-b 2016 IEADF163B 16.8 1.03 1

16DF7A DF-7-a 2016 IEADF167A 15.7 4.69 OSL 3

16DF7B DF-7-b 2016 IEADF167B 15.7 4.78 OSL 4

16DF8A DF-8-a 2016 IEADF168A 16.2 0.87 OSL 1

16DF8B DF-8-b 2016 IEADF168B 16.2 0.75 1

16DF9A DF-9-a 2016 IEADF169A 14.4 2.73 OSL 2

16DF9B DF-9-b 2016 IEADF169B 14.4 2.39 2

15DF1 DF-1 2015 IEADF151A 15.3 4.90 14C 4

15DF2 DF-2 2015 IEADF152A 15.8 3.30 3

15DF3A DF-3-a 2015 IEADF153A 15.8 1.41 1

15DF3B DF-3-b 2015 IEADF153B 15.8 4.53 14C 4

15DF4 DF-4 2015 IEADF154A 16.3 1.99 2

15DF5 DF-5 2015 IEADF155A 17.1 1.23 1

15DF6 DF-6 2015 IEADF156A 16.7 0.94 1

1 The first two numbers are for the year collected, DF is for drowned forest1, and the number after DF is the core 

number in the order collected. Additional cores at the approximate same station have a letter following the core 

number.

2 IGSN is International GeoSample Numbers cataloged in the SESAR (http://www.geosamples.org/).

3 mbsl is meters below sea level.

Note: latitude and longitude for each core are not given to protect the site.

1 “Drowned Forest” was the term used to describe the project site during the fieldwork.
25

2.3 Laboratory Methods

2.3.1 Geophysical Data Processing

Raw bathymetric and side-scan data were imported into Caris HIPS and SIPS, and SonarWiz software, 

respectively. Bathymetric data were cleaned for spurious pings, corrected for motion and sound velocity 

variations, and referenced to mean sea level of the closest National Oceanic and Atmospheric 

Administration (NOAA) tidal station (Dauphin Island, ID 8735180). The 2015 and 2016 point clouds 

were gridded into digital elevation models (DEM) at 25 m2 resolution and merged into a single surface. 

The side-scan data were corrected for geometry (beam angle) and mosaicked at 0.2 m2

-resolution. Digital 

elevation models and side-scan mosaics were exported from processing programs as ASCII files and 

converted into rasters within the project Esri ArcGIS® geodatabase. Sub-bottom profiler data were

converted from Edgetech JSF format to industry-standard *.sgy format, an open standard file format

developed by the Society of Exploration Geophysicists for storing geophysical data. Processing, including 

swell filtering, water column muting, and secondary predictive deconvolution, were conducted in Sioseis

software. Processed sub-bottom profiles were then loaded into IHS Kingdom Suite software for 

interpretation and Fledermaus software for 3-D visualization and analysis. The DEM, two seismically 

resolvable surfaces from 2-D sub-bottom surveys (interpreted in IHS Kingdom and exported as XYZ 

points), core imagery, and physical measurements were imported into Schlumberger’s Petrel software. 

Acoustic impedance from density and p-wave velocities were used to create a time-depth relationship 

between core and seismic data. Interpretation of the geophysical data was aided by seismic data collected 

in the 1990s by the USGS for the MAFLA inner shelf region (Sanford et al. 2016).

2.3.2 Core, Sediment, and Microfossil Analyses

At LSU, the cores were stored in the refrigeration unit in the Department of Geology and Geophysics at 

4oC. The cores were logged using a Geotek Multi-Sensor Core Logger (MSCL) at LSU’s Department of 

Geology and Geophysics for whole-core gamma density of sediments. All cores from 2015 were logged. 

For the 2016 cores, one of the cores from each location were logged while the other 2016 cores were 

retained for OSL dating. Next, cores were split in half longitudinally, and each section was placed inside 

plastic tubes for storage and further analyses. One half of each core was retained as an archive in the 

refrigeration unit in LSU Department of Geology and Geophysics. High-resolution images for each 

archive half was generated using the Geotek MSCL-XZ digital imaging system. The cores used for OSL 

dating were logged, scanned, and analyzed after OSL dating was complete if enough of the core 

remained.

Samples for grain size and organic analyses were collected at intervals of 20 mm for all cores. 

Granulometric analyses were conducted using a Beckman Coulter LS 13-320 Laser Diffraction Particle 

Analyzer, using methods specified in Hülse and Bentley (2012). Subsamples were wet-sieved at 850 μm 

to remove large particles, mostly shell debris that was not re-incorporated into size distribution, 

deflocculated in a 0.05% sodium metaphosphate solution to which 30% H2O2 was added to remove 

organic particulates and then samples were further diluted with sodium metaphosphate for analysis. 

Organic content was determined using loss on ignition (LOI) analysis using the methods of Heiri et al. 

(2001). Subsamples for core 15DF1were collected every 50 mm (Gonzalez 2017), later reduced to 20-mm

intervals, for the remaining cores and 15DF1.

The micropaleontological analysis consisted of 28 samples from core 15DF1 (Figure 9) and three samples 

from cores 15DF3B, 16DF7B, and 16DF9B. Core 15DF1 is the longest of the cores and was collected 

approximately 420 m to the north-east of the trough with the exposed tree stumps on a slight ridge that is 

elevated roughly 3 m from the trough. A coarse sampling scheme was utilized through the Holocene sand 

facies in the upper part of core 15DF1. Samples from the transitional interbedded sand and mud facies 

were originally sampled at 100-mm intervals and then resampled at 50-mm intervals due to lithological 
26

variability. A 100-mm sampling scheme was employed through the forest-swamp facies for freshwater or 

terrestrial microfossils. Standard micropaleontological processing techniques outlined in Scott et al. 

(2001) were followed. Approximately 15000 mm3 of sediment was collected for each sampling interval. 

Sediment was wet sieved with deionized water over 1 mm, 125 μm, and 63 μm sieves. The residue was 

transferred to a drying plate and left to dry at 50oC in a lab oven. The residue was thinly spread over a 

picking tray, and >300 foraminifera were picked from the 1 mm to 125 μm fraction under a binocular 

stereo microscope, identified, and stored on micropaleontological assemblage slides. The >1 mm fraction 

was screened for Soritids and Peneroplids on a presence basis only. The >125 μm fraction was used to 

eliminate small, hard to identify foraminifera. Foraminiferal abundance (counted foraminifera per weight 

of dry sediment picked) was calculated for all samples.

Samples used for micropaleontology were collected directly above and below inferred erosional surfaces 

in three other cores (15DF3, 16DF7B, and 16DF9B) to improve stratigraphic interpretations. The 

previously mentioned methods were used for processing. Residue dispersed over one picking tray was 

examined from each core on a presence basis only. In the context of stratigraphy, foraminifera are

essential for determining the chronological development of the site. Coastal foraminifera could have only 

occupied the site during the late Holocene or previous highstands due to the bathymetric depth of the site 

(18 m) and sea-level elevations (Figure 3). This study used the framework of McBride et al. (1999),

alongside other Gulf foraminifera ecology studies to interpret the results.
27

Figure 9. Micropaleontological and radiocarbon sample locations for core 15DF1. 

Core images with expanded section (3.0–4.78 m) to the right. Pollen, microfossil (including seeds), and radiocarbon 

sampling locations are noted on the left (m) and radiocarbon ages (BP) (Table 2) are shown on the right. Seeds were 

also recovered from the core catcher sample from this core.
28

Pollen analysis focused on the lower 0.7 m of core 15DF1 where interbedded mud and terrestrial peat 

were found consisting of dark gray and tan brown to dark brown muds. This section had higher 

percentages of organic material, and lower bulk density and woody macrofossils are present. Samples 

were collected for pollen analysis every 50 mm in core 15DF1 (4.05–4.75 m) (Figure 9). One sample was 

also collected from a small disjunct layer of peat at the 3.23 m level in the core. At each sample location, 

600 mm3 of the material was extracted for pollen analysis. Before processing began, 1 Lycopodium tablet 

(Lund University, batch 483216, count 18,583) was added to the sample to aid in the calculation of pollen 

concentration (Stockmarr 1971). Standard pollen processing procedures were followed (Faegri and 

Iversen 1989). Each sample was subjected to HCl (removal of carbonates), KOH (deflocculates the 

sample and breaks down organics), HF (removal of clays), and acetolysis solution (removal of cellulose). 

The residue was stained with safranin, suspended in silicone oil, and mounted onto slides.

All pollen and spores were counted under a light microscope (400x magnification) until minimums of 300 

were obtained (including indeterminable grains). North American pollen references (McAndrews et al. 

1973, McAndrews and King 1976) were used to help with identification. Tilia software was used to 

calculate pollen percentages and concentrations, and to present the results graphically (Grimm 1991). The 

percentage of indeterminable grains was calculated as a proxy for preservation (condition). 

Indeterminable grains were defined as grains that were degraded, folded, compressed, or damaged to the 

point that identification was impossible. Samples with over 10% indeterminable grains were interpreted 

as having poor preservation.

2.3.3 Macro Botanical Analysis

In the laboratory, wood specimens collected by divers in 2013 were placed in a fume hood and allowed to 

dry slowly to reduce cracking and checking. The dried wood was sliced using a microtome to make the 

thin sections and to view cellular structure. Harley and paleobotanist Renee Breedlovestrout at UI 

identified the species of the wood collected by divers in 2013. The identification of wood in the sediment 

cores is saved for future analysis.

After drying, samples were mounted and sanded using progressively finer sandpaper and processed using 

standard dendrochronological methods (Speer 2010, Stokes and Smiley 1968). These laboratory methods 

ensured that all wood surfaces were prepared so that cellular features can be discerned under a light 

microscope. Because the exact calendar year of growth rings within the wood specimens was unknown, 

the innermost complete ring on each sample was assigned the relative year “1” and each subsequent 10th

ring was marked with an “X” under the microscope. Each sample was scanned with an EPSON 

Expression 10000XL scanner, and all tree-ring widths were measured to 0.001 mm accuracy using 

coupled WinDendro (Regents, Inc., ver. 2016c) software. The computer program COFECHA was used, 

which uses segmented time-series correlation techniques to assist in crossdating of undated tree-ring time 

series (Holmes 1983), to help match and cross date each sample relative to one other. Forty-year time 

segments lagged by 20 years were tested to suggest possible temporal placements of all samples and used 

a minimum correlation value of 0.40 (typically p < 0.001) as a statistical standard of convincing 

agreement between measured series. After considering the suggested temporal placement made by 

COFECHA, each series was visually compared. Internal cross-dating (or crossmatching) resulted in a set 

of measured series that were aligned temporally with each other “floating” in time but were not absolutely 

dated. The computer ARSTAN program was used to standardize each tree-ring series with a smoothing 

spline with a 50% frequency response cutoff equal to two-thirds the length of each series. This level of 

detrending preserves low-frequency variance in each series suitable for analysis of multidecadal climate 

trends. Interactive detrending on each measured series was used to ensure that the applied standardization 

spline was accurately capturing the ends of the series and not over- or under-predicting the raw values.
29

To understand how the trees at the offshore glacial-age site responded to the climate before becoming 

inundated by sea-level rise and subsequent marine burial, the floating chronology was compared with the 

closest tree-ring chronology within the Gulf Coast region. A T. distichum (TADI) collection was located 

from Pascagoula, Mississippi (30.58oN, 88.02oW) available on the International Tree-Ring Data Bank

(IRTDB) (MS002 contributed by D.W. Stahle, M.D. Therrell, and M.K. Cleaveland). The Pascagoula 

River T. distichum chronology spanned 484 calendar years from 1466 to 1992 CE. To update the existing 

MS002 chronology, Harley and others relocated the cypress stand from which the original cores were 

collected and collected new increment cores in October 2015 (referred to here as PASC). Two cores were 

extracted from 23 T. distichum trees following standard dendrochronology field methods (Stokes and 

Smiley 1968). Telescoping ladders were used to get above the lower buttress swell of individual trees. 

Tree cores were prepared and cross dated using methods standard to the field of dendrochronology 

(Stokes and Smiley 1968).

A suite of techniques and analyses were used to compare the floating Submerged Forest tree-ring 

Chronology (SFC) with other bald cypress chronologies that are anchored in time. To assess the 

inequality in the paleo record (SFC) compared to reference chronologies, the Gini coefficient (Biondi and 

Qeadan 2008)—an all-lag measure of ring-width variability within each time series—was calculated

using all bald cypress tree-ring chronologies within the species geographic range available on the ITRDB 

(n = 39, including Pascagoula River). The redfit function in dplR software package in R (Bunn 2008) was 

used to investigate the frequency domain and spectral aspects of the SFC and PASC. Spectral analysis 

was complemented with wavelet analysis using a Morlet and derivative of Gaussian (DOG) mother 

wavelets to examine how the modes of variability change over time within the reconstruction time series 

(Torrence and Compo 1998).

An examination of sediments in the core catchers by Beth Middleton of the USGS, an expert of botanicals 

in the Southeast US, found several well-preserved seeds. Middleton provided DeLong with seed type 

samples of common seeds in the Lower Mississippi Valley for seed identification. During microfossil 

analysis of core 15DF1, seeds and seed fragments were separated from the sediments and identified to 

genus and/or species level using a dissecting microscope. Seeds were saved for future analysis.

2.3.4 Dating of Sediments and Wood

Stratigraphy and radiometric dating methods were used to establish the relative age range for the site with 

previously buried trees. Smaller samples were cut from the larger diver-collected wood specimens for 

radiocarbon (14C) dating at the Center for Accelerator Mass Spectrometry (CAMS) at Lawrence 

Livermore National Laboratory in 2013 and 2014. In 2016 and 2017, additional samples were sent to the

Beta Analytic Testing Laboratory for radiocarbon dating 14C dating, including eight bulk sediment 

samples extracted from the floodplain facies in core 15DF1 (Figure 9) and one sample from core 

15DF3B. Samples were pretreated, rinsed over a 150-μm sieve and examined under a microscope to 

ensure the residue was woody debris. Only this woody debris was used for 14C dating. No marine 

reservoir correction was used for woody samples because they had initially been terrestrial. In 2017, a 

4.0-mg sample made up of mixed genera benthic foraminifera was collected from the deepest section of 

core 15DF1 (3.30 m), where there was sufficient carbonate material for 14C dating (Figure 9), and sent to 

Beta Analytic. The date for the foraminifera was corrected for the marine reservoir effect using MARINE 

13 (Reimer et al. 2013). Measured radiocarbon ages were corrected for isotope fractionation to 

conventional radiocarbon ages based on separate determinations or assumed values for δ13C.

Because many of the 14C dates were radiocarbon dead, OSL dating was used to obtain the age of the 

sediment in the cores. Cores collected in 2015 were analyzed using MSCL and were “reset” by the 

cesium-137 radiation, so OSL dating was not advised on these cores. New cores were collected in 2016,

with two cores extracted from each location, one for stratigraphy and one for OSL dating, (Table 1). 

Zhixiong Shen, an OSL expert at Coastal Carolina University, performed OSL dating of five core sections 
30

collected in 2016 following the method of Shen Z et al. (2012). Technology and methods have drastically 

improved the reliability and precision of OSL dating with reliable age measurements up to 200 ka 

(Murray and Wintle 2003, Rhodes 2011). To help refine the chronology of the site, all 2016 cores were 

examined for their potential for OSL dating. Five sections (0.2–0.43 m in length) from cores 16DF3A, 

16DF9A, 16DF7B, 16DF7A, and 16DF8A were selected for OSL dating at the Luminescence Dating 

Laboratory at the University of Liverpool. Cores were sampled at the deepest depth identified below a 

prominent erosional surface in each core. Silt-sized quartz (4–15 μm) were the dominant datable particles 

in all OSL samples. They have been used to date coastal deposits in the northern Gulf back to ~200 ka 

(Shen Z et al. 2012). OSL ages were obtained for all the five samples. Sand-sized quartz (180–250 μm) 

extracted from the sample from core 16DF7B was also dated to corroborate the silt-sized ages. OSL 

measurement was done using the single-aliquot regenerative-dose protocol of Murray and Wintle (2003) 

with a preheat at 240oC for 10 s, a cut-heat at 180oC, and a blue light stimulation at 280oC for 40 s at the 

end of each single-aliquot regenerative-dose run. The equivalent dose (De) of each aliquot was calculated 

using an early background subtraction method (Ballarini et al. 2007). Dose recovery tests with a given 

dose ranging between 100 and 200 Gy on 16 aliquots produced a recovered/given dose ratio of 1.02 

±0.06.

Natural radioactivity of all the samples was measured using a high-resolution, low background gamma 

spectrometer at the University of Liverpool and converted to natural dose rate using the conversion 

factors by Guérin et al. (2011). Water content measured in the lab for each sample, an a-value of 0.03 

(Mauz et al. 2006) for silt-sized quartz, an internal dose rate of 0.03 ±0.02 Gy/ka for sand-sized quartz, 

and the attenuation of beta irradiation following Mejdahl (1979) were also used for natural dose rate 

calculation. For cosmogenic radiation calculations, it was assumed that the samples were underneath 20 m 

of water for 15% of their burial time and subaerially exposed for the remainder. An uncertainty of 10% is 

introduced to cosmogenic radiation calculations. The samples from cores 16DF3A and 16DF9A were 

collected from close to major lithologic boundaries, and their gamma radiation heterogeneity was 

accounted for following Aitken (1985).

Wood is not typically dated with uranium-thorium (U-Th) methods, but because the wood was too old to 

be dated using radiocarbon methods, it was decided to try U-Th dating. Previous studies have 

demonstrated that trees can uptake uranium (Edmands et al. 2001, Ma et al. 2000), so U-Th dating may be 

feasible, as demonstrated in buried wood from Hudson Bay (Allard et al. 2012) and tested in western 

Siberia (Maksimov et al. 2015). DeLong contacted a colleague at National Taiwan University, River 

Shen, an expert with U-Th dating in carbonates. DeLong’s student, who worked in Shen’s lab for a 

semester in 2015, transported wood samples from three core catchers and diver-collected wood to Taiwan 

for dating in September 2015. U-Th chemistry (Shen et al. 2003, Shen et al. 2008) was performed in 

October 2017 on a Thermo Electron Neptune multi-collector inductively coupled plasma mass 

spectrometer (MC-ICP-MS) (Frohlich et al. 2009, Shen et al. 2012) at the High-Precision Mass 

Spectrometry and Environment Change Laboratory in the Department of Geosciences, National Taiwan 

University. Replicate U-Th analyses were performed on all samples. The coral U-Th dating method (Shen 

et al. 2008) was modified for the analysis of wood samples dissolved in 5% nitric acid.
31

3. Results

3.1 Geophysical

Bathymetry around the exposed forest region is similar to that described in previous regional studies 

(Dufrene et al. 2003, McBride et al. 1999); the most prominent features are a series of northwestsoutheast trending ridges and troughs with 2–5 m vertical relief and ~0.5 km wavelength (Figure 10). The 

tree stumps are located within and around a hole in the seafloor (~1 m relief, ~100 m long, <10o walls) 

nested in a trough (Figure 10). Seafloor backscatter is uniformly lower within the troughs compared to the 

ridges (Figure 11a) and particularly low within the hole where tree stumps are exposed. Individual tree 

stumps can be identified by side-scan sonar and appear to have lower reflectivity than the surrounding 

seafloor (Figure 11b). Buried stumps could not be confidently identified in the subsurface through CHIRP 

sub-bottom profiling, even with tighter line spacing (Figure 8) and slower surveying speeds (<5 knots) in 

the 2016 survey.
20

Figure 10. Three-dimensional digital elevation model of 2015 and 2016 bathymetric data. 

The red dashed line outlines the depression where tree stumps are exposed. Black dashed lines bracket an artifact of merging the 2015 and 2016 data sets. Data 

were smoothed to a 1 m grid. A-A’ is referred to in Figure 13 and B-B’ in Figure 26.
21

Figure 11. Side-scan sonar mosaic illustrating seafloor sediment texture variation. 

(A) Light and dark colors indicate higher (coarser sediment) and lower (finer sediment) backscatter, respectively. Backscatter is lowest between ridges (dashed 

black lines) and particularly where trees and Pleistocene swamp sediments are exposed (purple box). (B) Side-scan sonographs of trees exposed to the seafloor 

(purple boxes). Left and right panels are from the same approximate area (purple box in A) but acquired on adjacent track lines.
22

The uppermost stratigraphic layer present across the entire survey site is a sand sheet, except where the 

tree stumps are exposed. Lithology indicates this layer is a predominantly well-sorted medium to fine 

sand and shell hash (Gonzalez et al. 2017). The sand varies in thickness between 0 and 5 m, is thickest on 

ridges, and thinnest or absent in troughs (Figure 12). Bathymetry and sand sheet thickness generally 

correlate well. This indicates that strata underneath the sand sheet are relatively flat, and sand distribution 

is not controlled by precedent stratigraphy.

Figure 12. The thickness of Holocene sand sheet in the study area. 

(a) Isopach map of sand sheet thickness derived from CHIRP seismic data. Reds indicate a relatively thin or absent 

layer; blues indicate thickest sand deposits. The thickness of the sand sheet scales with relief from the seafloor, 

where seafloor depressions have thin or absent sand cover, and seafloor ridges have thick (~5 m) deposits. (b)

2015–16 bathymetry, which demonstrates that the Holocene sand sheet is not primarily influenced by precedent 

stratigraphy. (c) Sub-bottom profile of transect A-A’ (upper left and right); the green line indicates the base of the 

Holocene sand sheet; red lines indicate Pleistocene surfaces. Vertical exaggeration 10x.

The dense CHIRP sub-bottom grid can be projected into three-dimensional space and viewed as a fence 

diagram to aid analysis and interpretation (Figure 13). The CHIRP data, in general, provides higher 

vertical resolution than previous surveys but does not resolve strata >30 m below the seabed surface, 

likely due to the acoustically reflective surficial sand sheet (Figure 11). Based on seismic facies and 

stratal geometry, the subsurface is divided into two units, Unit 1 and Unit 2, from deepest to shallowest.

a b

c
23

Figure 13. Three-dimensional fence diagrams of interpreted CHIRP data. 

(a) Aspect is looking north, and (b) Aspect is looking south. Vertical exaggeration is ten times. The gold ellipse 

represents an area where tree stumps are subaqueously exposed. Annotated reflectors are water bottom (yellow), 

base of Holocene sand sheet (green), paleochannels (blue) and Pleistocene surfaces (red). Pleistocene strata 

generally dip to the south-southeast with dip angle decreasing both east-west (reflectors in the stump area are 

relatively flat-lying) and deep-shallow. (a) Pleistocene reflectors are incised by paleochannels and are truncated by 

the base of the Holocene sand sheet. (b) Steeply dipping clinoform geometry of Pleistocene reflectors in the 

northeast quadrant of the survey area, as compared to relatively flat-lying western reflectors in the stump area.

Unit 1 (red annotation, upper bounded by green horizon in Figure 13) extends from the deepest resolvable 

reflectors to 0–5 m below the seafloor, and is characterized by concordant, subparallel reflectors that dip 

south-southwest. The dip angle of these reflectors generally decreases from east to west (particularly flatlying reflectors underlying the exposed trees), with deepest resolvable reflectors in the east displaying 

sigmoidal geometry. Localized crosscutting is apparent within Unit 1 (blue annotation in Figure 13) and 

regional but discontinuous unconformities truncate dipping strata from overlying flat-lying reflectors. 

Unit 2 (bounded below by green horizon and above by yellow horizon in Figure 13) varies in thickness 

between 0 and 5 m and overlies a strong and laterally continuous reflector. Unit 2 has no internal 

reflectors and is acoustically homogeneous.

The geophysical results (Obelcz 2017) aid in the interpretation of the core stratigraphy and define the 

paleo-geomorphology of the region around the exposed stumps. Figure 14 displays the CHIRP subbottom profile (both interpreted and uninterpreted) crossing over the trough where stumps are exposed, 

with the surficial sandy unit found on either side of the trough (near A–A′ in Figure 15), along with a 

gamma-density profile of core 15DF6 illustrating the physical properties that are related to the acoustic 

properties. In this profile, four seismic units are identified: (top, pink) a surficial sand sheet separated 

a

b
24

from subjacent deposits by a reflector that occurs near the same depth as the sand-mud boundary in the 

density profile of core 15DF6 and is likely the Holocene ravinement surface also identified by Kindinger 

et al. (1994) and McBride et al. (1999); (laterally contiguous, yellow) undifferentiated deposits below the 

sand sheet with horizontal reflectors; (adjacent, green) more strongly reflective deposits below the trough; 

and (deepest, blue) deposits with steeply dipping reflectors. This deepest unit is comparable to seismic 

strata interpreted by Kindinger et al. (1994) to be bay-head deltas of late Pleistocene age.

Figure 14. CHIRP sub-bottom profile along trough where wood was found. 

Uninterpreted (a) and interpreted (b) CHIRP sub-bottom profile dip-oriented across the subaqueously exposed tree

stumps (see Figure 10 for location of A-A′). Holocene sand (red) is thin or absent near the late Pleistocene 

interbedded mud and peat (green) where the stumps are located. The stump area presents as a negative amplitude 

anomaly, but individual trees cannot be identified likely due to being at or below the horizontal resolution threshold of 

the system. Below the sand sheet is undifferentiated late Pleistocene terrestrial deposits, which may include swamp, 

paleosol, or floodplain facies (yellow), and below that bay-head delta facies with clinoform dipping directions (solid 

black lines). (c) Gamma density profile of core 15DF6, which was acquired in the vicinity of the trough (see Figure 15

for core location).

3.2 Physical Properties of the Sediments

A total of 18 vibracores were collected in 2015 and 2016, spanning multiple sediment types, both inside 

and outside of the depression that contains exposed stumps (Figure 15 and Table 1). In August 2015, a

linear total of 17.08 m of cores were collected, and on July 2016, 26.16 m were collected. Excellent 

preservation of organic materials was observed in the peat sections of the cores including large pieces of 

wood, roots, seeds, pollen, and insects. The sand and mud sections directly above the peat sections 

yielded marine microfossils (foraminifera) with good preservation. The Holocene sand section contained 

whole and shell fragments including several olive shells (Oliva sp.) with glossy surfaces intact. Core and 

sediment analysis results were reported in Gonzalez et al. (2017) for core 15DF1 and the remaining cores 

in Gonzalez et al. (in review).
25

Figure 15 Bathymetric map of study site with core locations. 

Red dashed line encircles the trough where stumps are exposed. Core locations are gray circles with core labels 

(Table 1). Exact latitude and longitude are not shown to protect the site. A-A′ is the cross-section shown in Figure 14.

Grain size-frequency contour plots were generated using the results obtained from the laser-diffraction 

analysis of the cores (Figure 16). Distinct grain size changes and distribution are evident in the down 

section in each core. Surficial units of each core (up to ~3 m thick) are generally >95% sand. Core 

16DF1C is dominantly sand of uniform grain size throughout. Core 16DF3B is also sandy, but fines 

gradually downward, with some depth intervals of siltier sediment. Core 16DF8B has a sandy uppermost 

0.10 m, below which grain size is primarily silt, except for an additional sandy interval at 0.45–0.55 m 

depth. Below the surficial sandy unit, interbedded sand and mud are evident in some cores (0.30–0.405 

mm in core 15DF1 and 0.60–2.96 m in 15DF3B). Below units of interbedded sand and mud, the dominant 

modal grain size is in the silt range.
26
27

Figure 16. Grain size distributions for all cores. 

Core grain size is shown as a color contour plot of % volume versus depth. Frequency contour plots with warm colors 

indicate the dominant grain size for that depth in microns.

Soon after collection, cores were logged using a Geotek MSCL for whole core gamma density of 

sediments. The combined loss on ignition (LOI), gamma density, and grain size were compiled into core 

comprehensive graphs (Figure 17), and these properties together define distinct lithologies for each core 

profile. The uppermost sandy unit in each core contains up to ~1% organic content (Figure 17). A slight 

increase in organic content is found in the interbedded sand and mud unit (1.3–2.6%). In the interbedded 

mud and peat unit, organic content was as high as 20.3%. A paleosol was found only in the base of cores 

16DF8A and 16DF8B and displayed low organic content (0.6–3.8%). Overall, sandy units contained the 

lowest organic content, peaty units the highest, with intermediate values in muddy units.
28
29
30

Figure 17. Comprehensive graphs for cores. 

Percent organic content, mean grain size, and gamma density compared to depth profile are shown. Note: % organic 

content (horizontal axis) numbers were adjusted to show organic content variably throughout the core. Disturbed 

units are noted in red.
31

Gamma density profiles reveal distinctive variations down core that generally correspond to grain size 

and organic content: sandy units have the highest gamma density, peaty units the lowest, with muddy 

units having intermediate densities. Uppermost sands have high and relatively constant densities (~2.3–

2.5 g/cm3

). Underlying interbedded mud and sand have intermediate densities (e.g., ~1.8–2.3 g/cm3 for 

3.1–4.05 m in core 15DF1). Interbedded muds and peaty muds have low and variable densities (e.g., 1.2–

1.9 g/cm3 for 4.05–4.78 m in core 15DF1). The last lithological unit was identified as a paleosol in one 

core (~0.1–0.6 m in 16DF8B), which showed gamma density readings of 1.9–2.4 g/cm3

. Some sandy 

sections were found to have settled during transport and storage creating gaps and disturbed units of 

sediment in cores and are thus noted in core profiles.

3.3 Dating

3.3.1 Radiocarbon Dating

Radiocarbon (

14C) ages (Table 2) for 18 out of 20 wood and sediment samples were inconclusive due to 

radiocarbon dating detection limits, i.e., radiocarbon dead (measured 14C was not discernible from 

background levels thus older than ~50 ka) (Stuiver and Polach 1977). Woody debris samples collected 

from 4.05 m and 4.14 m downcore in core 15DF1 yielded conventional radiocarbon ages of 41,830 ±880 

BP (calibrated age of 45,210 calendar years (cal) before present (BP), i.e., calendar years before 1950) 

and 37,350 ±330 BP (41,830 cal BP), respectively. Calibrated ages were calculated using IntCal13 

(Reimer et al. 2013). A replicate sample (DF1-414-2 dup) had an infinite age; all of these radiocarbon 

dates should be interpreted with caution since they are close to the limitations of the radiocarbon dating 

method. Stratigraphic inversion, bulk dating methodology, and the limitations of radiocarbon dating have 

caused these ages from core 15DF1 to be cautiously treated as a minimum estimate of the forest’s age. 

The sample of mixed genera benthic foraminifera had a conventional radiocarbon date of 3,940 ±30 BP 

(3,920 cal BP) thus providing a depositional age on the top of the interbedded sand and mud facies in core 

15DF1.
32

Table 2. Radiocarbon Results

Sample 1 Type 2 Sample

depth (m)

Facies Lab analysis # 3 δ13C 4 14C age 5 ± Cal BP 6 Cal BP range 6

ALAF C1 Wood Seafloor CAMS-160062 –25 51,700 2600

ALAF C1 dup Wood Seafloor CAMS-160064 –25 >52,500

ALAF B1 Wood Seafloor CAMS-160063 –25 >49,600

ALAF-B1 dup Wood Seafloor CAMS-160128 –25 >51,200

GOM 1A Wood Seafloor CAMS-167083 –25 50,700 3100

GOM 1B Wood Seafloor CAMS-167084 –25 51,200 3400

GOM 2A Wood Seafloor CAMS-167085 –25 >51,400

GOM 2B Wood Seafloor CAMS-167086 –25 >52,600

GOM 013A #1 Wood Seafloor CAMS-167087 –25 >48,600

GOM #2 Wood Seafloor CAMS-167088 –25 52,400 3900

GOM 005A Wood Seafloor CAMS-167089 –25 >49,100

15DF1-322 BWD 3.22 LPISM Beta-433024 –30.1 >43,500

15DF1-330 Foraminifera 7 3.30 LPISM Beta-483831 –0.1 3,940 30 3,920 4,045–3,830

15DF1-405 BWD 4.05 LPIMP Beta-433025 –28.8 41,830 880 45,210 46,690–43,625

15DF1-414 BWD 4.14 LPIMP Beta-429909 –23.0 37,350 330 41,830 42,235–41,350

15DF1-414-2 

dup

BWD 4.14 LPIMP Beta-433026 –28.9 >43,500

15DF1-419 BWD 4.19 LPIMP Beta-433027 –28.7 >43,500

15DF1-424 BWD 4.24 LPIMP Beta-433028 –31.0 >43,500

15DF1-456 BWD 4.56 LPIMP Beta-433029 –27.4 >43,500

15DF1-466 BWD 4.66 LPIMP Beta-433030 –28.5 >43,500

15DF3B-310 BWD 3.10 LPIMP Beta-488002 –26.7 >43,500

1 “dup” is duplicate.

2 BWD = Bulk woody debris

3 CAMS samples were analyzed at the CAMS at Lawrence Livermore National Laboratory in California and samples labeled Beta were analyzed at Beta Analytic 

Radiocarbon Dating Laboratory in Miami, Florida. CAMS samples are wood samples collected by divers in 2013. Beta samples are from cores 15DF1, and 
33

15DF3B collected in August 2015. CAMS sample preparation backgrounds were subtracted based on measurements of samples of 14C-free wood. Backgrounds 

were scaled relative to sample size. 

4 CAMS carbon stable isotopic ratio (δ13C) values are the assumed values according to Stuiver and Polach (1977) when given without decimal places. Beta 

reported δ13C values were measured separately in an isotope ratio mass spectrometer. They are not the AMS δ13C, which would include fractionation effects from 

natural, chemistry, and AMS induced sources. δ13C values were calculated relative to the PDB-1 standard as per mil (‰).

5 Quoted age is in radiocarbon years using the Libby half-life of 5568 years and following the conventions of Stuiver and Polach (1977). CAMS samples ALAF B, 

ALAF C1 dup, GOM 2A, GOM 2B, GOM 013A#1, and GOM 005A are reported as two sigma limits as per Stuiver and Polach (1977). Carbon-14 ages with an > 

before age are infinite ages and samples are radiocarbon dead, i.e., extremely low 14C activity that is almost identical to the background signal.

6 Calendar Years Before Present (cal BP; Present = AD 1950) determined using INTCAL13 (Reimer et al. 2013) with 2σ ranges given when appropriate. A 

calendar age is not reported for infinite dates (>) since calendar ages may imply a higher level of confidence than is appropriate.

7 Foraminifera sample age determined using MARINE13 (Reimer et al. 2013) with no local reservoir correction.

LPIMP = late Pleistocene Interbedded Mud and Peat, LPISM = late Pleistocene Interbedded Sand and Mud.
34

3.3.2 Optically Stimulated Luminescence Dating

Four samples for optically stimulated luminescence (OSL) dating were collected from core depths with 

possibly undisturbed sediment overlying the forest-swamp facies, and one sample was collected from the 

paleosol found in the eastern section of the survey grid (Figure 15). The OSL dates range from 56 ka 

(16DF-8A-1) to 73 ka (16DF-7A-1) (Table 3) suggesting the forest age is between 56 and 74 ka or MIS 

3–5 (Figure 3). The core with the paleosol (16DF-8A-1) dated to a younger OSL age than the other 

samples. This difference in age could be due to core 16DF-8A-1’s location within a higher relief area 

(Figure 15). The age is still consistent with the hypothesis that the area exhibited variable relief. Some of 

the OSL cores penetrated more deeply than their duplicates, so there is incomplete stratigraphy of the area 

(see section 3.2).

3.3.3 Uranium-Thorium Dating of Wood

Initially, the wood cellulose did not dissolve in the nitric acid as quickly as desired, and it was decided to 

let it digest for a longer period before conducting U-Th dating and making further adjustments to the 

methodology. The age of the wood samples was all younger than the OSL and radiocarbon ages (Table 

4). They are interpreted as apparent dates. Two different initial values were used for 230/232Th, 4 ±2 ppm 

(blue color, Table 4) and 2 ±2 ppm (green color, Table 4). The uncorrected ages should be the maxima 

age of these wood samples based on U-Th dates. The 230/232Th value of the soil surrounding the wood may 

be helpful for age correction. These ages are all deglacial and may represent a resetting of the U and Th

concentrations in the wood as the terrestrial site became inundated by seawater as sea level rose.
35

Table 3. Optically Stimulated Luminescence Samples and Relevant Analytical Results

Core Water/sample 

depth (m)

Facies 238U±1σ 

(μg g–1)

232Th±1σ 

(μg g–1)

K2O±1σ 

(μg g–1)

Water 

content (%)

dcosmic 

(Gy ka–1)

1

Size fraction 

(μm)

dnatural ±1σ 

(Gy ka–1)

De ±1σ 

(Gy)

OSL age

±1σ (ka)

16DF3A 15.8/2.12 LPIMP 2.96±0.09 11.61±0.34 1.37±0.04 0.57±0.10 0.15 4–15 1.48±0.17 106±3 72±8

16DF9A 14.4/2.57 LPISM 4.18±0.11 12.43±0.27 1.33±0.03 0.25±0.10 0.14 4–15 2.89±0.21 182±6 63±5

16DF7A 15.7/4.30 LPISM 3.52±0.09 12.63±0.28 1.34±0.03 0.27±0.10 0.12 4–15 2.64±0.22 193±5 73±6

16DF8A 16.2/0.60 Paleosol 4.96±0.13 17.02±0.35 1.52±0.04 0.20±0.10 0.18 4–15 3.81±0.29 214±10 56±5

16DF7B 15.7/4.58 LPISM 3.50±0.10 12.01±0.28 1.16±0.03 0.24±0.10 0.12 4–15 2.60±0.21 193±6 74±6

180–250 2.25±0.20 138±10 61±7

16DF7B weighted mean 70±5

1 Cosmic dose rates were calculated with and without seawater at the coring site. The cosmic dose rates for age calculation were derived by assuming ~15% 

burial history with seawater of present-day depth at the coring sites, considering sample ages, water depth at the sites, and sea-level history.

LPIMP = late Pleistocene Interbedded Mud and Peat, LPISM = late Pleistocene Interbedded Sand and Mud.
36

Table 4. U-Th Isotopic Compositions and 230Th Ages for Wood Samples

Sample

ID

Weight

(g)

238U 

(ppb) 1

232Th

(ppt)

δ234U

Measured 1

[230Th/238U

Activity 2

230Th/232Th

atomic (x 10–6)

Age (year ago)

uncorrected

Age (year ago)

corrected 3, 4

Age (year BP)

relative to 1950 

δ234Uinitial

corrected4

W1 0.0154 41.42 ± 0.50 11244 ± 64 232 ± 14 0.2025 ± 0.0093 12.30 ± 0.55 19,475 ± 999 13,537 ± 3193 13,471 ± 3193 241 ± 14

16,549 ± 3120 16,482 ± 3120

W2 0.0176 203.3 ± 1.5 49006 ± 462 194.8 ± 9.2 0.1858 ± 0.0097 12.71 ± 0.67 18,344 ± 1046 12,913 ± 2959 12,846 ± 2959 202.0 ± 9.7

15,664 ± 2900 15,597 ± 2900

W3 0.0116 139.0 ± 1.0 32578 ± 257 238 ± 11 0.1516 ± 0.0070 10.66 ± 0.49 14,188 ± 707 9,090 ± 2697 9,024 ± 2697 244 ± 12

11,671 ± 2639 11,604 ± 2639

W4 0.0171 116.72 ± 0.38 15495 ± 114 192.1 ± 6.3 0.2035 ± 0.0080 25.3 ± 1.0 20,315 ± 883 17,354 ± 1730 17,288 ± 1730 201.7 ± 6.7

18,845 ± 1717 18,778 ± 1717

Analysis by MC-ICP-MS Thermo Electron Neptune at National Taiwan University. Analytical errors are 2σ of the mean.

1 [238U] = [235U] x 137.818 (±0.65‰) (Hiess et al. 2012); δ234U = ([234U/238U]activity – 1) x 1000.

2 [230Th/238U]activity = 1 – e–λ230T + (δ234Umeasured/1000)[λ230/(λ230 – λ234)](1 – e–(λ230 – λ234)T), where T is the age.

Decay constants are 9.1705x10–6 year–1 for 230Th, 2.8221x10–6 year

–1 for 234U (Cheng et al. 2013), and 1.55125x10–10 year–1 for 238U (Jaffey et al. 1971).

3 Age corrections, relative to chemistry date in October 2017, were calculated using an estimated atomic 230Th/232Th ratio of 4 (±2)x10–6.

Those are the values for a material at secular equilibrium, with the crustal 232Th/238U value of 3.8. The errors are arbitrarily assumed to be 50%.

4 δ234Uinitial corrected was calculated based on 230Th age (T), i.e., δ234Uinitial = δ234Umeasured X e λ234*T, and T is corrected age.
37

3.4 Micropaleontological Analyses

3.4.1 Pollen

Pollen results from core 15DF1 are reported in Reese et al. (2018) (Figure 18). Lowermost samples within 

the core (4.75–4.55 m) show high percentages of Taxodium, Nyssa (tupelo), and the family Cyperaceae 

(sedges). Minor components include typical bottomland hardwood species such as Quercus (oak), Carya

(hickory), Betula (birch), Ulmus (elm), Fraxinus (ash), and Liquidambar (sweetgum). Pinus (pine) pollen 

is also prevalent, but < 20%, and is probably representative of the regional pollen rain transported from 

more upland sites. This pollen assemblage indicates a cypress-tupelo, backwater environment. At the 4.5-

m level, however, a dramatic change is observed in the pollen assemblage. Percentages of cypress and 

tupelo decrease while Poaceae (grass) pollen is dominant in all but a few samples up to the top of the

mud/peat section (at 4.05 m). Coeval with this change is the appearance of Typha (cattail) and the 

emergence of Alnus (alder). However, from 4.3 to 4.2 m, the grass percentage declines briefly. At this 

depth range, cypress spikes again, this time without tupelo. Alder remains a prominent pollen type and 

birch re-emergences. Above 4.2 m, cypress, birch, and alder decline, and grass again resume dominance 

up to the top of the mud-peat section.

We also examined pollen in a peat layer at 3.23 m separated from the lowermost mud/peat layer by a zone 

of interbedded sand and mud (Figure 9). Pollen preservation in this sample was particularly poor, with 

nearly 20% of the grains indeterminable. Pine, oak, hickory, and cypress are the prominent taxa, with 

birch, elm, and Carpinus (hornbeam) as minor components. The stratigraphic integrity of this layer does 

not appear to have been preserved. This section is probably reworked based on the foraminifera dating 

results at 3.3 m (Section 3.3.1), and the particularly poor preservation that is likely to be an artifact of 

bioturbation or mechanical mixing. A radiocarbon date for this material came back “dead.” In general, the 

pollen concentration shows an inverse relationship with the percentage of indeterminable pollen grains. 

Concentrations are highest in the lowermost zones, then decrease up the core, coeval with increased 

percentages of indeterminable pollen. It is important to note that throughout this section of the core, 

percentages of the organic matter remain constant, and do not decrease up the core. Thus, one hypothesis 

is that concentration is driven, at least in part, by pollen preservation and caution should be exercised 

against interpreting these changes in concentration with changes in actual pollen rain.
38

Figure 18. Pollen assemblages for core 15DF1. 

Pollen results are shown as percentages. Four pollen zones were identified below 4.0 m. Above that is Holocene marine interbedded sand and mud.
39

3.4.2 Foraminifera

Marine microfossil results are reported in Troung et al. (in review) (Figure 19). Foraminifera 

identification to the genus level followed Loeblich and Tappan (1988), and to the species level, when 

possible, using Phleger and Parker (1951), Bandy (1954, 1956), Andersen (1961), Puckett (1992), and 

Poag (2015). Specimens were compared to samples housed at the LSU Natural Science Museum’s 

Collection of Fossil Protists and Invertebrates. Paleoenvironmental interpretations were applied using 

foraminiferal distribution and environmental associations outlined in Phleger and Parker (1951), Bandy 

(1954, 1956), Murray (1991), Puckett (1992), Gangopadhyay et al. (1996), McBride et al. (1999), Scott et 

al. (2001), Kohl et al. (2004), and Poag (2015). Triloculina spp., Nodobaculariella sp., Spiroloculina sp., 

and Miliolinella sp. were grouped into “Other Miliolids.” Indeterminate specimens were defined as being 

too small, degraded, or broken for positive identification. It is assumed that coastal foraminifera equate to 

Holocene sediments based on the depth of the site (18 m) and sea level elevations.

Foraminifera results from core 15DF1 (Figures 9, 19) indicate that Rosalina spp., Hanzawaia 

concentrica, Elphidium spp., Cibicidoides spp., and miliolid taxa account for >70% of all the genera in 

the top 3.30 m of core 15DF1 and are similar to the miliolid, Rosalina, and Asterigerina carinata 

assemblages from McBride et al. (1999). Soritids and Peneroplids are present in assemblages down to 3.2 

m. Foraminiferal abundance in the core from 0.40 to 2.75 m is between 134 and 285 specimens/g and 

then significantly increases to 1625 specimens/g at 3.1 m. Organic content determined by LOI displays a

subtle downwards increase within the top two facies (Gonzalez et al. 2017). The presence of preserved 

foraminifera is only found within the sandy sediments in the interbedded sand and mud facies. The 

number of shell fragments in samples decreases down the core, and no foraminifera was present from 

3.35 to 3.55 m except one Oolina sp. at 3.5 m. A unit of coarser grain size and increased shell fragments 

corresponds with increase foraminiferal abundances similar to that observe within the Holocene sand 

assemblages at 3.6 m and 3.8 m. A distinguishing feature from the interbedded sand and mud facies is 

that porcelaneous taxa represent a much smaller percentage (<2%) of the assemblage from 3.6 to 3.8 m. 

An interval of no foraminifera is noted from 3.85 to 3.95 m with few shell fragments. Two broken and 

poorly preserved Textulariida tests were recovered from 4.0 m. Foraminiferal abundances from the 

interbedded sand and mud facies are much lower than throughout the Holocene sand and range from 0.7 

to 73.10 specimens/g. Indeterminate specimens account for <2% of each sample. Samples from the 

interbedded mud and peat facies in core 15DF1 (4.05–4.78 m) are characterized by relatively high 

percentages of organic material (>4%), and no foraminifera or ostracoda were present (Figure 19).

Micropaleontological analysis of samples from cores 15DF3B, 16DF7B, and 16DF9B found Ammonia 

parkinsoniana, Quinqueloculina spp., Rosalina spp., Elphidium spp., Asterigerina carinata, and 

Cibicidoides spp. present in all samples that contained foraminifera. Microfossils are absent from sample 

depths of 2.25 m and 4.00 m in 16DF7B. From the detailed investigation of core 15DF1 age constraints, 

environmental associations, the depth of samples (16–20 mbsl), and sea-level reconstructions, these 

foraminiferal assemblages are determined to be Holocene in age and lie above the MIS 2 sequence 

boundary (Figures 3, 19).
40

Figure 19. Foraminiferal assemblages for core 15DF1. 

Foraminiferal percentages (%) for core 15DF1. Gamma density, mean grain size, and LOI analyses completed by Gonzalez et al. (2017).
41

3.4.3 Seeds

Intact preserved seeds (T. distichum, Hibiscus lasiocarpas, Carex, Triadenum, Cephalanthus occidentalis, 

Liquidambar styraciflua, and Nyssa) were found in peat and mud samples in core 15DF1 and identified 

using modern type samples (Figure 20). The preliminary analysis of seeds in core 15DF1 for presence 

only was completed (Table 5). Additionally, a small insect identified as a mite was found in the peat 

section; another example of the excellent preservation in the peat section of this core. The seeds were 

saved for future analysis.

Figure 20. Seeds preserved in peat section. 

Examples of seeds found in sediment core 15DF1 from 4.2 to 4.3 m shown with modern seeds for comparison. 

Clockwise from top left is bald cypress (T. distichum), marsh St. John’s-wort (Triadenum), rose mallow (Hibiscus 

lasiocarpos), sweet gum (Liquidambar styraciflua), and button bush (Cephalanthus accidentalis).

Table 5. Preliminary Seeds Analysis in Core 15DF1

Core depth 

(m)

Nyssa 

aquatic

(tupulo)

T. distichum

(bald cypress)

Cephalanthus 

occidentalis

(button bush)

Carex 

(Sedges)

Grass Misc 

seeds

Notes

4.10–4.20 X X X X X Poa

4.30–4.40 None

4.40–4.50 X X X Sedge Many 

seeds

4.53 X X Juncus?

4.60 X Insect

4.70 X

a b c

d e
42

3.5 Wood and Dendrochronology

Dendrochronological and wood analyses results are summarized in Harley et al. (in review) and included 

here. Five of the diver-collected wood samples were sectioned with a microtome for microscopic analysis. 

All five were identified as bald cypress (T. distichum) (Figure 21). Not all of the wood specimens 

collected were microscopically identified since many of them were large enough to be visually identified 

as bald cypress. The wood samples were stored in deionized water for five years before thin sections were 

cut. As the wood had softened, it was difficult to make thin sections using the microtome, even when an 

epoxy was used to stabilize the wood. A change in cells and density from latewood and early wood 

boundaries can be observed. It is difficult to differentiate between Atlantic white cedar and bald cypress

microscopically, but an indicator of bald cypress is the pinching of the annual rings that was observed in 

all wood specimens examined. Therefore, based on the ring anatomy and growth form, the specimens

examined are most likely bald cypress. Additionally, these samples appear similar to modern bald cypress 

samples from Pascagoula, Mississippi. There are no observable differences at the cellular level between 

bald cypress and pond cypress (T. ascendens). No minerals deposition was observed; however,

dissolution was observed in the wood some specimens. This could be due to storage of the specimens in 

deionized water for five years. Of the 23 wood specimens collected in 2013, one was identified in the 

field as a palm (Figure 22) and the another was very degraded, and both were discarded since they could 

not be used for dendroclimatology.

Figure 21. Example of bald cypress thin section. 

Wood thin section (a); magnified view of (b); example of an annual growth ring in a bald cypress thin section (c).

a

b c
43

Figure 22. Wood collected by divers in 2013. 

Twenty-three wood specimens were recovered by divers (a-c) and processed on land for transportation (d–l) by 

cutting into smaller pieces to check for annual rings and preservation state. One was identified as palm (j–k) due to it 

fibrous texture and was discarded.
44

Of the 21 wood specimens extracted from the site by divers in 2013 and transported back to the 

laboratory, 12 were retained for dendrochronological processing and analysis (Figure 23). Samples that 

appeared to derive from roots or branches were excluded; only wood specimens collected from in situ

stumps or large sections of stumps lying on the surface sands and sediments were retained. Two of the 12 

specimens retained for dendrochronology could not be successfully cross dated due to issues with circuit 

uniformity and disturbance from wood-boring organisms.

Figure 23. Bald cypress sample with ring width measurements. 

This sample (ID: GOM100) was included in the tree-ring chronology. The full sample image is shown (a) with a 

zoomed inset displayed with the width measurement path (b). Large circular holes in wood are from shipworms and 

bivalves boring into the wood after being exposed to seawater.

A total of 10 samples were successfully crossdated against each other to develop a Submerged Forest

tree-ring chronology (SFC) that was not anchored in time (e.g., “floating”). The SFC spans 489 years in 

length with an interseries correlation of 0.58 (p < 0.001) and mean tree age of 206 years (Figure 24). This 

chronology is floating in time because a confident radiocarbon date could not be attained for any of the 

wood specimens collected from the stumps (section 3.3.1), and the time series could not be crossdated 

against the Pascagoula T. distichum reference chronology (MS002; ITRDB) from the Gulf Coast region, 

which starts in 1466 CE. The radiocarbon and OSL results (section 3.3) suggest the age of the forest and 

the wood recovered from that site is between 41.8 and 74 ka.

The index of tree growth at the beginning of the SFC exhibited a high level of variability (years 0–97), 

but this is common in many tree-ring indices and is attributed to a low number of samples (<3) (Figure 

24). Sample depth was low (n = 1) during the first 76 years of the chronology, but increases to four at 

year 98. This low sample depth precluded any growth trend interpretations until year 100. Years 100 to 

350 are characterized by high-frequency growth variability until after which trees demonstrated a gradual 

decline in growth trend and year-to-year variability to year 430. A release (i.e., increase) in growth 

occurred during the period from year 430 to 482, after which is followed by a marked decline in growth to 

year 489. Year 489, the last complete ring in the chronology, is characterized by the narrowest growth 

ring in the entire time series. Further, eight of the ten samples contained the same outermost growth ring, 

which was characterized by a partial growth ring during year 490 of 6–10 rows of earlywood tracheids. 

Bark was not present on two of the samples, and this is evident in the drop in index growth about year 

450 towards the end of the index chronology.

a b

bivalve
45

Figure 24. Tree-ring index from wood collected at the study site. 

The master index chronology of tree-ring growth normalized to one (black) shown with the number of samples for 

each year (gray). The index is floating in time with the oldest year as 0 and the youngest as 489.

3.6 Facies

Based on gamma density, grain size, organic content, and sediment observations, five different lithologic 

units (i.e., lithofacies) characterize the sedimentary deposits found in the study area (Figure 25, Table 6). 

Lithofacies’ names are generally considered to be age-independent (North American Commission on 

Stratigraphic Nomenclature 2005). Here, in order to provide more concise and practical litho- and chronostratigraphic descriptions, age and facies of strata identified in the cores are described together. Facies 

descriptions were initially derived for core 15DF1 in Gonzalez et al. (2017), which includes a highresolution image of core 15DF1, and then applied to comparable lithologic units in the other 17 cores in 

this report. Two new facies classifications are added, a late Pleistocene interbedded sand and mud and a 

paleosol, which are found in five cores collected in 2016: 16DF8A and 16DF8B for the paleosol facies, 

and 16DF7A, 16DF7B, and 16DF9A for the late Pleistocene interbedded sand and mud facies. Facies'

physical characteristics are consistent in all of the cores, but facies depth ranges are different for each 

core. Four of the facies (facies 1, 2, 3, and 5) are consistent with the lithologic descriptions of McBride et 

al. (1999).
46

Figure 25. Examples of the five lithofacies. 

Numbers indicate facies. Facies 1 is Holocene Sand (HS), facies 2 is Holocene Interbedded Sand and Mud (HISM), 

facies 3 is late Pleistocene Interbedded Mud and Peat (LPIMP), facies 4 is late Pleistocene Interbedded Sand and 

Mud (LPISM), and facies 5 is late Pleistocene Paleosol (LPP). See Table 6 for facies intervals.
47

Table 6. Facies Location and Depths for Sediment Cores

Core ID Interval (m) Facies Date2

15DF1 0–3.10 HS

3.10–4.05 HISM 3,920 14C

4.05–4.78 LPIMP 45,210 and 41,830 14C

15DF2 0–2.75 HS

2.75–3.30 LPIMP

15DF3A 0–1.06 HS

15DF3B 0–0.60 HS

0.60–2.96 HISM

2.96–4.53 LPIMP

15DF4 0–1.20 HS

1.20–1.67 HISM

1.67–1.94 LPIMP

15DF5 0–0.14 HS

0.14–1.12 LPIMP

15DF6 0–0.47 HS

0.47–0.93 LPIMP

16DF1B 0–0.94 HS

16DF1C 0–1.66 HS

16DF1D 0–3.64 HS

3.64–3.92 LPIMP

16DF3A 0–0.62 HS

0.62–1.77 HISM

1.77–2.20 LPIMP 72 ±8 ka OSL

16DF3B 0–0.96 HS

16DF7A 0–1.00 no sediments 3

1.00–1.50 HS

1.50–1.93 no sediments 3

1.93–3.0 HS

3.0–3.70 no sediments

3.70–4.05 HS

4.05–4.64 LPISM 73 ±6 ka OSL

16DF7B 0–2.06 HS

2.06–4.44 LPISM

4.50–4.72 3 LPISM 70 ±5 ka OSL

16DF8A 0–0.10 HS

0.10–0.80 LPP 56 ±5 ka OSL

16DF8B 0–0.10 HS

0.10–0.62 LPP

16DF9A 0–1.86 HS

1.86–2.67 LPISM 63 ±5 ka OSL

16DF9B 0–1.75 HS

1 HS = Holocene Sand (facies 1), HISM = Holocene Interbedded Sand and Mud (facies 2), LPIMP = late Pleistocene 

Interbedded Mud and Peat (facies 3), LPISM = late Pleistocene Interbedded Sand and Mud (facies 4), and LPP = late 

Pleistocene Paleosol (facies 5). Facies examples are shown in Figure 24.

2 Full dating results appear in Table 3. Radiocarbon dates are cal BP

3 This core section was not imaged.

Facies 1: Holocene Sand. Facies 1 is characterized by light, beige to grey, fine- to medium-grained quartz 

sand containing abundant bioclasts and shell fragments (Figure 25, Table 6). Color becomes progressively 

lighter up section with some intervals slightly darker than others. Sediments are moderate to well-sorted,

and minor planar bedding is present. The foraminiferal assemblage in cores 15DF1 and 15DF3 are 

consistent with a shallow marine environment (see section 3.4.2). Most of the bioclasts are highly 
48

fragmented and vary in size. A prominent shell bed, 50 to 150 mm thick, is also found within this facies 

in some cores, typically at the base of the sand bed. This facies is consistent with facies five and six

described by McBride et al. (1999) as primarily sand and shelly sand. These sand sheet deposits are 

thickest in the cores recovered from the ridges and thinnest or utterly absent in the cores recovered in the 

trough of the study site (Figures 12, 15–17). These facies are present in all cores.

Facies 2: Holocene Interbedded Sand and Mud. Facies 2 is characterized by light to medium-dark gray 

mud interbedded with very fine-grained sub-bioclastic sand and to some extent, shell fragments (Figure 

25, Table 6). Fine-grained sand occurs in beds that are well-sorted and have no sedimentary structures 

present other than prominent sand-mud interbedding. Beds are mostly 10 to 30 mm thick where 

individual layers have relatively uniform thickness. At some intervals, the mud is more abundant than 

sand. This unit is present in cores 15DF1, 15DF3B, 15DF4, and 16DF3A. Bedding patterns are 

comparable to estuarine and middle-to-inner shelf interbedded mud and sand described by Bentley et al. 

(2002) and Keen et al. (2004) for the modern shelf and Mississippi Sound estuary 75 to 150 km west of 

the study area. Evaluation of microfossils suggests a shallow marine assemblage (see section 3.4.2).

Foraminifera extracted from core 15DF1 at 3.3 m were radiocarbon dated to 3.9 ka cal BP. Global sea 

levels estimates for the Holocene puts this date at roughly 3 mbsl (Figure 3) or 0 to 1 mbsl from northern 

Gulf sea levels (Donoghue 2011). Collectively, these observations suggest that this facies is marine in 

origin and formed as coastal deposits during the Holocene transgression, but could likely be estuarine 

based on possible water depth. However, conditions on the lower shoreface of the shelf could also 

produce similar bedding. In addition, late Pleistocene ages have been determined for all units underlying 

this lithology, suggesting that the base of these facies (boundary between facies 2 and 3) defines a 

substantial unconformity.

Facies 3: Late Pleistocene Interbedded Mud and Peat. This facies is characterized by dark grey, tan to 

dark brown muds, and peats or peaty mud (Figure 25, Table 6). Some intervals are darker than others, 

especially where woody debris is found. Organic material and woody debris are abundant in this facies. 

Wood fragments are light brown in color and roughly 10 to 20 mm thick in the cores. No sedimentary 

structures are evident other than prominent bedding consisting of peat and mud layers. Woody debris 

visible in the cores correlate stratigraphically to the bald cypress stumps exposed in the scoured trough 

(Figures 15–17). This facies was not identified by McBride et al. (1999) but is present in nine cores in our 

study area (15DF1, 15DF2, 15DF3B, 15DF4, 15DF4, 15DF5, 15DF6, 16DF1D, and 16DF3A). This 

facies was sampled for radiocarbon dating in cores 15DF1 and15DF3B and for OSL dating in core 

16DF3A (Tables 2–3). Radiocarbon dates from core 15DF1 ranged from ~41 ka to >50 ka (i.e., 

radiocarbon dead) suggesting an approximate time of MIS 3 or older (Figure 3). OSL dating results for 

this facies in core 16DF3A dated to 72 ±8 ka near the boundary between MIS 4 and 5.

Marine macro- and microfossils are absent in the samples studied from this facies (see section 3.4.2), but 

pollen is present and detailed for core 15DF1 (see section 3.4.1). Pollen assemblages are consistent with 

modern bald cypress-tupelo gum forest in the basal portion of this facies in core 15DF1 (4.45–4.75 m).

This assemblage changes between 4.35 and 4.50 m where percentages of cypress and tupelo gum pollen 

decline sharply and are replaced by grass and sedge pollen. Reese et al. (2018) suggest this change is 

likely associated with a more open, possibly brackish environment as sea level increased during the 

transition out of marine isotope stage (MIS) 3 (Figure 3). However, from 4.30 to 4.20 m, the percentages 

of cypress increase again and are codominant with alder (Alnus). Furthermore, seeds were also found in 

this facies, and they generally align with pollen results (see section 3.4.3). Sediment properties of this unit 

are consistent with deposition in a bald cypress swamp producing peat and woody debris in a river 

floodplain that provides mud beds from episodic flooding (Heitmuller et al. 2017; Smith and Bentley 

2015). Overall, there is a coarsening upwards in core 15DF1 where all three facies (Holocene sand, 

Holocene interbedded sand and mud, and late Pleistocene interbedded mud and peat) show some evidence 

of bioturbation such as mottling and truncated beds.
49

Facies 4: Late Pleistocene Interbedded Sand and Mud. This facies displays similar grain size and bedding 

patterns to facies 2 (Holocene interbedded sand and mud) although this unit contains more fine sand than 

facies 2, in which coarse grains are mostly fine sand (Figure 25, Table 6). Facies 4 also tends to be more 

consolidated (higher density), darker in color, has higher organic content (2–4% sometimes evident as 

woody fragments) than facies 2 (0–2%) (Figures 17–18), and generally contains no marine microfossils 

(only cores 15DF1 and 16DF7B were examined in detail [see section 3.4.2]). OSL dates from this facies 

are late Pleistocene in age when the study area would have been located well above sea level. Based on 

this information, this facies was likely deposited by a terrestrial, freshwater system during late MIS 4 to 

MIS 3. Such stratigraphy of interbedded sand and mud with woody organic debris produced by a 

terrestrial fluvial source has been observed in inland fluvial overbank deposits of the northern Gulf Coast, 

such as in the Atchafalaya Basin in Louisiana (Roberts et al. 1997).

Facies 5: Late Pleistocene Paleosol. This facies is characterized by light gray, yellowish, and orangecolored silt and clay-sized sediments and are only present in two cores: 16DF8A and 16DF8B (Figure 25, 

Table 6). This unit is identified by McBride et al. (1999) as their facies 1. Evidence of near subaerial 

exposure is confirmed by the clear traces of oxidation found in these sediments. Organic content 

determinations were low for this facies. The OSL age obtained from core 16DF8A is 56 ±5 ka (Table 3), 

which places this paleosol in the late Pleistocene near the boundary of MIS 3 and 4. Such a relatively 

young age for this core compared to the other cores dated using OSL suggests that this core location may 

have been elevated topographically, and unburied or exposed for a longer time than other core locations. 

Furthermore, age constraints from this facies and the overlying Holocene sand indicate the presence of an 

erosional unconformity between these two deposits (McBride et al. 1999). No macrofossils are evident in 

the archived core half or sieved samples in this facies (microfossil analysis was not performed).

3.7 Integrated Site Model

Bathymetry data captured characteristic ridge and trough morphology of the modern MAFLA province 

(Figure 15). Guided by background literature and core data from this project, Obelcz (2017) identified 

three seismically resolvable surfaces including the seafloor, a transgressive surface, and a basal surface 

truncating steeply dipping clinoform packages (Figure 26). Two seismic units are resolved from the three 

surfaces: Unit 1 (U1) is bounded above by the seafloor and below by a relatively flat-lying shoreface 

ravinement contact consisting of amalgamated shell hash and sand produced by Holocene marine 

transgression; Unit 2 (U2) is truncated above by the transgressive surface and below by the basal surface. 

U1 is interpreted to be the Holocene sand sheet (0–5 m thick) with age confirmed by the radiocarbon 

dating of foraminifera in core 15DF1 (Table 2). U2 is defined to be undifferentiated Pleistocene alluvial 

plain deposits (swamp/paleosol in the interbedded mud and peat facies) and interbedded sand and mud 

facies estimated to be 1 to 8 m thick. OSL and radiocarbon dating of these facies confirm the Pleistocene 

age between 42 and 73 ka (Tables 2–3). The dipping layers below U2 maybe point bar deposits, but 

Obelcz (2017) interprets them to be Pleistocene bayhead deltaic deposits due to geometry, literature, and 

constraint by the overlying swamp/terrestrial facies. These sequences are prograding, and generally, dip 

southwest with the incline increasing towards the east and with channel crosscutting apparent to the south.
50

Figure 26. Three-dimensional subsurface model of the study area. 

a) White dashed circle represents where stumps are exposed on the surface. b) Core data (15DF1) was imported to 

aid interpretations with grain size (red) and LOI (green) shown. The transgressive surface is relatively flat-lying while 

the basal surface geometry exhibits topographical highs. No cores penetrated the basal surface. Vertical 

exaggeration (V.E.) is 50x.

The base of U2 exhibits variable topography (Figures 26–27), and the presence of a paleosol (16DF8A) 

on top of one of these paleohighs suggests that there was paleorelief, which may have contributed to the 

preservation of the forest in a topographic depression. The thickness of the alluvial fill package (U2) is 

thickest in the central area of the study site and thinnest in the northeastern and southeastern corners 

where paleosols are present. The analysis shows that there was enough accommodation to allow at least 8 

m of sediment accumulation (possibly in pulses) (Figure 27) before being eroded during lowstands and 

Holocene transgression.
51

Figure 27. The thickness of U2 in the study area. 

U2 is thickest in the central area of the study site. At least 8 m of sediment accumulated before being partially eroded 

during the sea level lowstand and Holocene transgression. U2 is thinnest in the northeast and southeast corners 

where paleosols formed (cores 16DF8A and 16DF8B)). The dashed line represents approximate area where peat 

and wood were observed in cores.
52

4. Discussion

Bartek et al. (2004) reconstructed the Mississippi and Alabama coastline from the marine isotope stage

(MIS) 2–3 highstand approximately 35,000 years ago to the Holocene. The MIS 3–4 highstand may be 

similar to the interval when the ancient forest was growing; however, further dating and core analysis are 

needed to determine the geomorphological character of the leading study site. This provides a beginning 

context for interpretation of the results from this study. The discussion of results is summarized here 

including geophysics in Obelcz (2017), regional stratigraphy in Truong et al. (in review) and Gonzalez et 

al. (in review), and paleoenvironmental interpretation in Reese et al. (2018) and Harley et al. (in revision).

4.1 Geophysics

Based on previous research (Kindinger 1988, Bartek et al. 2004) and new CHIRP data (Figure 13), the 

dipping reflectors underlying the entire survey area are interpreted to be bay-head delta deposits, although 

the geometry could also indicate fluvial lateral accretion deposits. This interpretation was not ground--

truthed because no cores penetrated this sequence but is based on sigmoidal reflector geometry and 

overlying terrestrial facies. These deposits are associated with sea-level transgression, wherein valleys 

incised across the shelf during sea-level lowstands become deltaic depocenters as the coastal zone (and 

locus of deposition) moves landward with rising sea level. The steeper-dipping reflectors to the east are 

logical given the site’s location on the western edge of the Mobile paleovalley; steeper gradients would be 

expected as the axis of the paleovalley (greatest accommodation space) is approached.

Bay-head facies are overlain by terrestrial facies. These include the swamp facies (Late Pleistocene 

Interbedded Mud and Peat [LPIMP]) in which the drowned forest is situated and paleosol (Late 

Pleistocene Paleosol [LPP]) in the eastern survey area. There is an erosive unconformity, which forms a 

reflector of variable amplitude, at the base of the swamp-paleosol strata (LPIMP-LPP) that truncates the 

bay-head facies; this is interpreted as the transition between marine-estuarine (bay-head delta) and 

terrestrial (swamp-paleosol) environments. The swamp and paleosol lithofacies (LPIMP-LPP) are 

stratigraphically coeval; the lateral boundary between them is not apparent in the seismic data.

The penultimate stratigraphic layer is a transitional facies, which is not ubiquitous throughout the survey 

area. Where it is present, it lies in between swamp-paleosol (LPIMP-LPP) and sand sheet facies 

(Holocene sand [HS] and Holocene interbedded sand and mud [HISM]) and is lithologically a mix of 

interbedded muds and sands. The transitional layer is seismically indistinguishable from the underlying 

terrestrial facies. This layer is interpreted to be a transition between terrestrial or potentially estuarine and 

marine environments, hence the nomenclature. The bay-head, swamp, paleosol, and transitional facies 

combine to compose Seismic Unit 1 (Figure 13).

The uppermost layer is the transgressive/marine Mississippi-Alabama-Florida (MAFLA) sand sheet, or 

Seismic Unit 2. Previous studies have speculated whether the MAFLA sand sheet was entirely formed 

during and after sea level transgression, or whether bathymetric ridges (Figure 10) are partially or entirely 

relict Pleistocene barrier island complexes (McBride et al. 1999). Due to the lack of internal stratigraphy 

(Figure 28), characteristic of barrier islands (washover fans, seaward progradation), the sand sheet in this 

region is interpreted to be a syn or post-transgressive feature.

Buried tree stumps were not confidently resolvable within the subsurface using CHIRP sub-bottom 

profiling. This is hypothesized to be due to one of the following two factors, or both: 1) individual tree 

stumps are at or below the horizontal resolution of the CHIRP sonars used, which is a function of Fresnel 

zone geometry that is controlled by a number of factors including trace offset, source-receiver geometry, 

and others; or 2) the acoustic impedance contrast between wood and the sediments they are buried in and

between wood-bearing sediments and the surficial sand sheet are similar enough to be indistinguishable.
53

A sub-bottom system with a smaller ensonifying seafloor footprint, such as an ROV-mounted CHIRP 

deployed a few meters above the seafloor, would address factor 1. Resolving factor 2, however, would be 

challenging when using acoustic methods.

Figure 28. CHIRP sub-bottom profile for B-B′. 

Uninterpreted (a) and interpreted (b) strike-oriented CHIRP sub-bottom profile taken across the largest sand ridge in 

the survey area (see Figure 10). Note the lack of internal stratigraphy within the sand sheet (red), which indicates that

these features are entirely reworked during or after transgression, as opposed to relict Pleistocene beach ridges or 

barrier islands. The yellow layer is undifferentiated terrestrial Pleistocene deposits, which may include swamp, 

paleosol, or floodplain facies. Below that are bay-head delta facies (blue) with diagnostic clinoform geometry. The red 

line “M” is a seafloor multiple. (c) Gamma density profile of core 15DF1 acquired in the vicinity of the CHIRP profile

where tan indicates sand sheet facies, gray indicates transitional facies, and green indicates swamp facies.

a

b

c
54

4.2 Paleoenvironmental Interpretation

4.2.1 Pollen

Although a high-resolution chronology for core 15DF1 has not been established, dating places the 

samples analyzed herein MIS 3–4, during a period of rapid sea-level fluctuations with amplitudes much 

higher than 10 m (Figure 3). DiMichele and Falcon-Lang (2011) proposed that rapid sea-level rise and 

corresponding floodplain aggradation are effective methods both to bury and to preserve autochthonous 

forests. Anderson et al. (2016) documented rapid Pleistocene floodplain aggradation for rivers of the 

north-western Gulf in a setting similar to the study site, where they found that floodplain aggradation 

rates tracked sea-level rise 1:1 up to >100 km inland. These observations suggest that the study area was 

buried deeply, after which glacial sea-level fall and marine transgression removed most of the 

overburden, allowing the forest strata to be exposed by recent energetic marine processes.

Pollen results from the lowermost section of the mud–peat layer shows a pollen assemblage typical of 

southeastern US cypress-tupelo backwater (Reese and Liu 2001), with high concentrations of cypress and 

tupelo and minor components standard in bottomland hardwood environments, which include the sedge 

family. Typically, bald cypress has biogeographical limits of 50 m in elevation but can occur up to 150 m 

(Little 1971), which agrees with previously discussed estimates for forest age, global sea level, and pale 

elevation. These conditions probably existed for some time while the site was exposed and, further inland,

separated hydrologically from the littoral zone.

At 4.50 m in core 15DF1 there is a change in the pollen assemblage to a more open, grass-dominated 

environment. This shift in the pollen assemblage probably corresponds to the impacts of a marine 

transgression that occurred in later MIS 3 or MIS 4 (Figure 18). It is hypothesized that as sea level rose, 

floodplain aggradation occurred far inland (Anderson et al. 2016), which may have resulted in an 

increased water table and an altered flood regime that drove this vegetation change (Schumm 2005,

Johnson et al. 2012). The first appearance of both cattail and Sparganium (bur-reed), along with the 

abundance of grass, helps to support this interpretation. However, the establishment of a more open 

environment was not a static change. In this depth range, from 4.30 to 4.20 m in core 15DF1, results show 

an interesting change in pollen assemblage. Percentages of grass pollen drop below 10%, while cypress 

and alder become prominent. This environment may represent a no-modern analog cypress–alder 

community. However, note that this assemblage has some commonalities to the modern-day Atlantic 

Coastal Plain Blackwater Levee/Bar Forest (Schafale 2009). This plant association occurs in coastal 

portions of North and South Carolina along relatively young sand bars or natural levees on blackwater 

streams. The association is described as having a different structure, with the canopy dominated by Betula 

nigra (river birch), bald cypress, and oaks. Shrubs and herbs are generally sparse, although patches of 

Alnus serrulata (hazel alder), Cyrilla racemiflora (swamp titi), and Vaccinium elliottii (blueberry) may 

exist (Schafale 2009). 

During this cypress–alder event, Betula and oak pollen is still very low, and therefore, this may not be a 

true analog. However, at the end of this event, as grass pollen begins to increase back to 50–60%, birch 

pollen does show a slight increase to roughly 10% of the pollen total. It is possible that the formation of 

bars and new natural levees could have hosted this cypress–alder assemblage, resulting from floodplain 

aggradation driven by sea-level rise (Gonzalez et al. 2017). In addition, floodplain aggradation and the 

accompanying sea-level rise may have been the mechanisms that rapidly buried and preserved the 

terrestrial sediments at this site (DiMichele and Falcon-Lang 2011, Gonzalez et al. 2017). Above 4.20 m, 

the grass-dominated assemblage returns to the top of the peat section at 4.05 m where the layer of 

interbedded sand and mud begins.
55

In summary, pollen assemblages have been determined for core 15DF1 recovered near a unique preserved 

forest site in the northern Gulf. The peat and mud deposits in this core have been dated to MIS 3–4 during 

a period of rapid global sea-level variations, providing a glimpse into the response of late Pleistocene 

plants to climate change and sea-level rise. Based on the radiocarbon dates obtained in the upper section 

of the peat, the marine transgression that probably caused the final burial of the peat occurred around 40 

ka BP near the end of MIS 3. Pollen results within the peat suggest a transition from a cypress-tupelo gum 

backwater to a more open community dominated by grasses and sedges. During this transition, there may 

be evidence of a no-modern analog cypress–alder community although additional pollen work is needed, 

over a wide variety of cores, to enable a more comprehensive explanation of the MIS 3–4 vegetation 

dynamics at the site.

4.3.2 Wood

The rapid decline in growth towards the end of the chronology (Figure 24) combined with the finding that 

8 of 10 samples contained the same outermost partial growth ring inside bark suggests that some event 

resulted in synchronous tree mortality, at least for most of the individuals included in the submerged 

forest chronology. Unfortunately, the study design and the nature of the data allow only speculation as to

the causal mechanism responsible for such a widespread mortality event. Some of the potential 

disturbance agents in the region that could have resulted in widespread mortality include fire, insect 

outbreak, drought, sea-level rise, and tropical cyclone. After careful inspection of the macrofossil wood 

specimens, no evidence (e.g., insect galleries, fire scars, or mechanical wound scars) was found that 

provided clues to a mortality agent. Modern bald cypress is not known for being susceptible to pests, and 

a widespread fire or tropical cyclone would have likely caused immediate mortality of trees, which does 

not align with the growth trends in the Submerged Forest tree-ring Chronology (SFC) during the last ~140 

years of the record. Bald cypress along the Gulf Coast are thought to be a tropical cyclone resilient 

species along with Quercus viginiana (live oak). Certain characteristics such as tree morphology and 

architecture and rooting structure are considered adaptations to high wind events (Doyle et al. 1995).

Studies of coastal bald cypress growth patterns within tidal freshwater swamps show salinity to be a 

limiting factor (e.g., Thomas et al. 2015). Abrupt climatic shifts known as the Dansgaard Oeschger Event

(DO) and Heinrich Event (HE) occurred during the glacial and are characterized by rapid and repeated 

climate shifts. At only 489 years in length, the SFC time series is too short to analyze for DO and HE 

events if they are the cause of the tree death. However, additional tree ring samples extending the floating 

chronology could capture this climate variability. The two most likely disturbances that could have led to 

the growth trends expressed in the SFC are: (1) long term drought conditions during the period years 

~350–430, then a switch to pluvial conditions causing the growth release during the period years ~430–

480, or (2) a rapid variation in localized marine transgression and regression.

Mapping the Gini coefficients for the 39 bald cypress tree-ring chronologies distributed throughout its 

modern geographic range revealed unique patterns concerning tree ring diversity (Figure 29). First, bald

cypress individuals located at the southwestern range limit in Texas, the southern range limit in Florida, 

and the northern latitudinal range limit in North Carolina and Virginia were characterized by the least 

diversity as shown by the Gini coefficients. Trees that exhibited the highest diversity were located along 

the Mississippi River Valley, Atlantic Coastal Plain, and the Gulf Coast, which included the Pascagoula 

River (PASC) chronology. More specifically, the tree ring diversity of the submerged forest chronology 

(Gini = 0.24) was most similar to a collection from South Carolina (SC006; difference = 0.002), Arkansas 

(AR052; difference = 0.003), Georgia (GA003; difference = 0.004), North Carolina (NC026; difference = 

0.008), and Mississippi (Pascagoula River; difference = 0.01). To investigate the temporal variability of 

ring width diversity throughout the SFC record, the Gini coefficient was calculated in 100-year intervals. 

Tree ring diversity (e.g., sensitivity) steadily declines during the first 400 years of the record, then 

increases sharply from year 400 to the end of the record in year 489. This change in temporal tree ring 
56

diversity is interpreted to represent an event, or series of events, that likely caused physiological stress to 

individual trees.

Figure 29. Gini coefficients for the glacial and modern bald cypress tree-ring indices. 

Map showing the distributions of Gini coefficients of the available T. distichum chronologies throughout its geographic 

range and locations relative to the submerged forest chronology in the northern Gulf.

Spectral analysis of the SFC over the period year 100–489 identified frequencies in the time series that 

are significantly different from a red-noise assumption in the interannual (2–3 year; p <0.05–0.01) and at 

low, multidecadal frequencies (p <0.01) (Figure 30). The same analysis revealed similar frequency 

patterns for the PASC chronology spanning the period 1466–2014 CE for interannual and lower 

frequencies (p <0.01). Morlet wavelet analysis indicated that the interannual frequency in the SFC was 

present throughout most of the time series, from year 100 to year 350 (Figure 30). After year 350, the 

interannual frequency fades coeval with the gradual decline in growth, most likely associated with growth 

conditions that were slowly becoming more adverse. The derivative of Gaussian (DOG) wavelet analysis, 

which is more appropriate for capturing events but not oscillations, reveals single events the span either 

16-years, 60-years, and 250-years exist throughout most of the SFC record. Modern-day bald cypress 

growth rings are known for having a consistent and robust sensitivity to moisture availability and 

precipitation (e.g., Stahle et al. 1998, Stahle et al. 2012, Cleaveland 2000). The Pascsgoula tree-ring 

chronology (PASC) reference chronology was found to be strongly correlated with regional precipitation 

from April to June for the period 1901 to 2014 (r >0.6; p <0.01). The 2–3-year periodicities identified in 

the spectral analysis fall within the range of variability often associated with El Niño-Southern Oscillation 

(ENSO), which is known to influence precipitation and river discharge in the southeastern US (Schmidt et 

al. 2001). However, the correlation between the PASC chronology and (1) a reconstruction of sea surface 

temperature (SST; HadISST 1o; Rayner et al. 2003) and (2) SST anomalies from the NINO3.4 region 

masked from the National Oceanic and Atmospheric Administration (NOAA) ERSSTv5 (Huang et al. 
57

2017) was tested and did not yield any significant associations between the PASC chronology and either 

version of ENSO.

Figure 30. Spectral analyses of tree-ring indices. 

Lomb-Scargle spectrum (a–b and wavelet spectra (e–h) of (left) SFC and (right) PASC chronologies. Respective 

chronologies (c–d) appear above wavelet spectra for reference. The top wavelet is the Morlet mother wavelet (e–f),

and the bottom is a DOG mother wavelet (g–h).

The most notable aspect of the SFC record is the changing growth trends from year 350 to the end of the 

chronology at year 489 marked by synchronous mortality in year 490. Bald cypress is known to have the 

ability to survive prolonged periods of flooding. In addition, previous research has found the 

establishment (e.g., Chabreck 1972) and survival of seedlings to be somewhat salt-tolerant. In a controlled 

experiment, Pezeshki (1990) watered bald cypress seedlings with a saltwater solution for 60 days and 

found no significant effects on the treatment on height growth, stomatal conductance, or net 

photosynthetic rate compared to seedlings treated with freshwater. However, Connor (1994) found 100% 

mortality of seedlings subjected to treatments of regular saltwater flooding. Hence, the combined 

disturbance of saltwater and flooding (e.g., saltwater inundation) is considered to be detrimental to the 

survival of bald cypress (e.g., Pezeshki 1990; Javanshir and Ewel 1993; Conner 1994). Coastal wetland 
58

areas along the southeastern coastal plain and more specifically, the northern Gulf have been subjected 

recently to increases in flooding and saltwater intrusion due to the combined effect of land subsidence and 

human-induced climate change and sea-level rise (e.g., Krauss et al. 2009; Thomas et al. 2015).

Krauss et al. (2009) found a robust negative relationship between site salinity and tree height, basal area 

and individual tree basal area increment within bald cypress forests in South Carolina, Georgia, and 

Louisiana. Given the nature of the submerged forest study site in the Northern Gulf and the subfossil 

material found there, precisely the causal disturbance mechanism that resulted in synchronous tree 

mortality and subsequent burial of trees cannot be determined. Yet, study results indicate that based on (1) 

the previously established relationship between increased salinity and basal area increment and (2) the 

growth trends during the last ~140 years of the SFC chronology that trees were responding negatively to 

gradual increase in saltwater intrusion that ultimately leads to the rapid decline in growth and mortality of 

trees.

Accelerated sea-level rise under current conditions of global climate change continues to impose stress on 

coastal forests. Along the northern Gulf, the combination of natural processes (e.g., land subsidence) and 

sea-level rise is causing the progression of saltwater mixing and flooding events upslope and inland. 

Observations along coastal forest margins report that various tidal freshwater forests of the Gulf and 

southern Atlantic coasts are undergoing dieback reportedly related to saltwater intrusion and tropical 

cyclone-induced surge events (Brinson et al. 1985, Brinson et al.1995, Gardner et al. 1991, Ross et al. 

1994; Williams et al. 1999, Williams et al. 2003, Williams et al. 2007, Doyle et al. 2003, Doyle et al. 

2010, Conner et al. 2007, Krauss et al. 2009, Saha et al. 2011). Despite an increase in research focused on 

predicting coastal species responses to rising ocean levels, ecological models are needed for regionalscale predictions of how coastal forests will adapt under changing climate and sea-level rise could benefit 

from dendrochronological data.

Although with this tree-ring study a confident causal mechanism for the synchronous mortality and rapid 

growth variability at the end of the SFC record could not be identified, the most likely causes were either 

singular or combined events of drought and saltwater intrusion from sea-level rise or storm surge. The 

489-year SFC record presented here provides a baseline on which to build future research at the site. 

Future work and subsequent sampling trips will be focused on extending the length of the SFC 

chronology and investigating additional sites with preserved macrofossil wood that were recently 

discovered at various shallower depths leading inland. These paleoenvironmental records will provide a 

better understanding of the dynamics of rapid sea-level rise that likely occurred in the past, which can be 

used to inform coastal communities of what to expect in the near future.

4.3 Regional Stratigraphy

The depositional environments and regional stratigraphy of the study area during the Pleistocene and the 

Holocene have been greatly impacted by changes in sea level in the northern Gulf. Consequently, events 

of marine transgression and regression have played a significant role in shaping the stratigraphy observed 

at this site today. The discussion summarized here is from Gonzalez et al. (in review) and Truong et al. (in 

review).

4.3.1 Foraminiferal-Environment Interpretation

The surficial sediments in core 15DF1 are dominated by massive, medium-fine sand (Gonzalez et al. 

2017) with a relatively homogeneous Rosalina-Hanzawaia-Elphidium-miliolid assemblage (Figure 19). 

Amphistegina, Archaias, Asterigerina, Nodobaculariella, Peneroplids, and Soritids, often termed 

calcareous-bank microfauna (CBF), are present in core 15DF1 (Figure 19, Appendix A). Modern CBF 

can be found in Cedar Key, Florida (a low-energy siliciclastic coastal setting on the northwest Florida 
59

coast) and on carbonate banks situated on salt domes, and therefore CBF occurrence in modern 

foraminiferal assemblages are a relict product of shoreface ravinement (Kohl et al. 2004). The surficial 

foraminiferal assemblages are interpreted as being derived from normal marine conditions (Culver 1988,

McBride et al. 1999, Kohl et al. 2004) and deposited in an inner neritic open marine environment similar 

to the present; this facies is congruent to facies 6 described by McBride et al. (1999). The present seafloor 

surface will be the future maximum flooding surface marking the boundary between the transgressive 

systems tract and the highstand systems tract (McBride et al. 1999, Gonzalez et al. in review). A shell bed 

located from 2.60 to 2.75 m and 3.15 m in core 15DF1 (Figure 9) was produced from shoreface 

ravinement and continued to be reworked by oceanographic processes (Anderson et al. 1997).

Below the lowermost shell bed (3.15 m), a zone of interbedded sands and muds persists in core 15DF1 

(Figures 9, 19). Lithologic variability within the interbedded sand and mud facies is congruent with 

assemblage variability (Figure 9). Silty sediments correlate with little-to-no preservation of tests (Figure 

9). Beds of sandy sediments at 3.60 m and 3.80 m yielded foraminiferal assemblages that are similar to 

the sand sheet communities with the exception of a sharp decline in miliolids (Figure 9). Foraminifera are 

present in low abundances and combined with observed test discoloration suggest taphonomic alteration 

for this core section rather than poor living conditions (Scott et al. 2001, Berkeley et al. 2007). The lack 

of CBF in the interbedded sand and mud facies provides additional evidence of a pre-shoreface 

ravinement environment (Anderson et al. 1997). The dark grey interbedded sand, and mud facies 

(Gonzalez et al. 2017, Gonzalez et al. in review) is lithologically similar to facies four described by 

McBride et al. (1999) with a slightly different foraminiferal assemblage (Figure 9). McBride et al. 

(1999)’s facies 4 exhibits an Elphidium-Haynesina assemblage that can also be found in many modern 

bays across the northern Gulf (Bandy 1956, Gangopadhyay et al. 1996, Osterman et al. 2009, Poag 2015), 

whereas interbedded facies at the study site host more neritic genera (Rosalina, Asterigerina, Cibicides, 

and Hanzawaia) (Figure 9). Radiocarbon dating reveals that sandy portions of the interbedded sand and 

mud facies were deposited before 3,920 cal BP whereas peaty portions in these facies (e.g., 3.22 m) are 

older Pleistocene peats reworked in this facies (Figure 9, Table 2). Sea level was ~2 to 4 m lower than 

present at 3,920 cal BP when sea-level rise started to decline from ~1 to 1.4 mm/year to 0.6 mm/year 

(Figure 3) (Balsillie and Donoghue 2004). A change in depositional style within Mobile Bay, possibly 

from rapid retreat of the bay-head delta (4.3–3.0 ka) or from increased storm activity (Twichell et al. 

2012), is coeval. Additional evidence for increased storm activity is provided by lithologically similar 

marine interbedded sand and mud facies, which were preserved as hurricane event horizons in the 

Mississippi Sound (Bentley et al. 2002, Keen et al. 2004). Alternatively, the possibility exists that the 

interbedded sand and mud facies is coeval with facies 4 of McBride et al. (1999) but in a more seaward 

position of the estuary indicating increased marine influence. Sequences of open bay muds overlying preHolocene deposits suggest that a barrier island system existed pre-inundation (Mars et al. 1992). This

introduces the scenario that these foraminiferal assemblages could be relict barrier island over-wash 

deposits, and hence, poor preservation. The integration of these results advocates that the interbedded 

sand and mud facies in core 15DF1 was deposited in a lower shoreface or marine dominated estuarine 

environment of the Holocene and was not a result of Pleistocene floodplain deposition.

The cessation of foraminiferal assemblages, in combination with pollen (Reese et al. 2018) and sediment 

core results (Gonzalez et al. in review), suggests the interbedded mud and peat facies as terrestrial in 

origin and associated with a peat accumulation sequence (Fisk 1960). A floodplain facies sample from 

core 16DF3A and optically stimulated luminescence (OSL) dating (72 ±8 ka; Table 3) provides an age for 

the earliest possible forest growth and constrains floodplain deposition to the falling stage systems tract 

(Figure 3). The succession of cypress assemblages to marsh environments (Figure 31) in the peat layers 

may be attributed to floodplain aggradation that accompanied pulses of sea-level rise during MIS 3 and 4 

(Figure 3).
60

Figure 31. An abbreviated chart of the foraminiferal and pollen assemblages for core 15DF1. 

Gamma density, mean grain size, and LOI analysis was completed by Gonzalez et al. (2017). Pollen analysis is summarized in section (4.2.1). TCT (TaxaceaeCupressaceae-Taxodiaceae) pollen is interpreted as T. distichum.
61

4.3.2 Depth-Age Relations and Lateral Correlation

The stratigraphy and facies of the study area are characterized by substantial geological and 

chronostratigraphic variability over short lateral and vertical distances (Figure 32). A roughly east-west 

cross-section (Figure 32) across the trough and ridge shows depth and age relations among facies in cores 

(all cores are georeferenced to their respective seabed depth and location) and the stratigraphic correlation 

in the study area. The depth of the Holocene ravinement surface is noted (also shown in Figure 10 but 

without detailed core data). The cross-section shows that both Holocene interbedded sand and mud and 

Pleistocene interbedded mud and peat occur in topographic lows and in some core locations have been 

eroded or are missing from the sedimentary record. Additionally, both of these facies are missing from the 

topographic high (sand ridge) in the easternmost core locations where the Holocene sand sheet lies 

directly upon the Pleistocene paleosol and on Pleistocene interbedded mud and sand at slightly deeper 

depths in cores 16DF9A and 16DF8A. The Holocene interbedded sand and mud is discontinuous, and it is 

missing from core 15DF6 inside the trough where stumps are exposed.

These observations suggest that paleo-topography (Figure 32) played a role in both the deposition and 

preservation of the muddy wood-bearing deposits. Holocene interbedded sand and mud were likely 

deposited in paleo-topographic lows on the Holocene ravinement surface and may have been eroded at 

the location of core 15DF6 at or near the time the trough was eroded, and the stumps were exposed 

(Figures 15, 32). Similarly, the Pleistocene interbedded mud and peat appears to have been deposited, or 

at least preserved, in a topographic low with respect to the elevation of Pleistocene interbedded sand and 

mud found in cores to the east.

If all of the radiocarbon and OSL dates (Tables 2–3) are reliable, and the actual ages are within the 

uncertainty estimates (2σ) for each date and are representative of depositional age, then both of the 

muddy Pleistocene deposits may have been deposited at or near the same time (Figure 3, Figure 32). 

Concomitant with that deposition scenario, the peaty deposits may have been forming in topographic lows 

while paleosols were developing on slightly higher ground to the east. These conditions are consistent 

with the geology and geomorphology of the nearby modern coastal plain where Pleistocene coastal and 

fluvial deposits (from MIS 5 and earlier) deposited at or uplifted to higher elevations are being eroded, 

incised, and weathered to form soils, and where many topographic lows are being filled with modern finegrained sediments and wetland vegetation.

Paleo-topography may have also influenced the time of burial. For example, the bottom of the Pleistocene 

interbedded sand and mud in core 16DF7B has an OSL age of 73 ±6 ka (Table 3), and it is the deepest 

core in the study site in terms of absolute elevation (Figure 32). In contrast, the bottom of core 16DF8A 

has the youngest OSL age of 56 ±5 ka (Table 3), and it is the shallowest core. Generally, older ages are 

stratigraphically and topographically located below younger ages. This finding is confirmed by the 

presence of highly oxidized paleosols found in two cores (16DF8A and 16DF8B; Table 6) indicating that 

the paleo-topographic highs in the study site were subaerially exposed before the Holocene transgression 

that further eroded and flooded the area (Figures 15, 32).
62

Figure 32. Stratigraphic cross-section and map of study site. 

The correlation of facies can be observed with all five units. OSL and radiocarbon dates are also plotted at their respective depths. Cores are georeferenced to 

their respective depths and locations. Stratigraphic cross-section A-A’ shown on map. mbsl
63

One working hypothesis has been developed that could explain forest preservation based on radiocarbon 

dates in the range of ~42–45 ka cal BP (Table 2), regional stratigraphy and geomorphology (McBride et 

al. 1999, Bartek et al. 2004) and the published range of sea-level estimates for MIS 1–4 (Waelbroeck et 

al. 2002). If organic-rich sediments in core 15DF1 were deposited ~42–74 ka cal BP, then elevation and 

sea level estimates combined with OSL dates (Table 3) suggest that the forest location was well inland 

from the coast at the time of forest growth ~30 to 50 m above the paleoshoreline (Figure 3), which is 

consistent with bald cypress biogeographical distribution (Figure 6). A short pulse of sea-level rise (~65 

ka, Figure 3) could potentially have caused floodplain aggradation at the forest site, burying and 

preserving the forest through subsequent sea-level fall, transgression, and ravinement. An alternative 

hypothesis is that forest burial was not associated with allogenic forcing and was instead caused by an 

autogenic process such as crevasse splay of the river channel proximal to the forest. This may be 

evaluated by more detailed stratigraphic analysis, and geomorphological reconstructions from seismic and 

core data as well as OSL and other dates as those results become available. Results from pollen and 

microfossil analysis are included to help interpret the evolution of the ancient forest as sea level changed.

4.4 Site Characteristics for Preservation

A consequence of the interbedded sand and mud facies in core 15DF1 being deposited in a coastal 

environment (Figure 33) constrains the chronology of the site and bounds the Holocene-Pleistocene 

unconformity (sequence boundary) above by the interbedded sand and mud facies and below by the 

floodplain facies (Figure 33 and Figure 34). At this location, the sequence boundary and bay-ravinement 

surfaces become amalgamated (Figure 31, Figure 33, Figure 34). Peat is assumed to mark the base of the 

sequence boundary, and terminations of coastal foraminifera deposition (Culver 1988, Kohl et al. 2004) 

are assumed to mark the top of the sequence boundary (Figures 33–34).

Mapping of the sequence boundary reveals an eastern high and a central western low in the study area 

(Figure 33 and Figure 34) displaying ~1 to 2 m of negative relief dating to MIS 2 (assuming differential 

compaction is negligible) (Table 2 and Table 3). Evidence of topography before MIS 2 is provided in 

geophysical data where U2 thins in the northeastern and southeastern extents of the study area (Figure 26

and Figure 27). Geophysical interpretation is supported by the presence of paleosols at the location of 

paleohighs (Figure 26, Figure 33, Table 6). Peats are preserved in the western portion of the study area 

(Figure 33) with 15DF3B hosting the longest section of recovered peat (1.57 m). Higher elevation 

Pleistocene interbedded sands and muds (16DF7 and 16DF9; Figure 34) in the southern extent could have 

been deposited as part of a fluvial system (Obelcz 2017). Observations are similar to elevation and 

morphology in modern-day floodplain channel-levee complexes (Lewin and Ashworth 2014).

The accommodation space provided by paleorelief with peats being preserved in the lower-lying areas 

(Figure 27, Figure 33, Figure 34) is conducive for forest preservation as sediment generally infills the 

lower-lying areas under the control of gravity first, and higher relief areas are either preferentially eroded 

or deposited later. Paleosols (56 ±5 (1σ) ka; Table 3) and a low-lying sequence boundary (MIS 2) suggest 

paleorelief was present and is a contributing factor in forest preservation in the western area of the study 

site (Figure 26, Figure 27, Figure 33, Figure 34). Core interpretations combined with seismic 

interpretations and chronology suggest paleorelief was established before 56 ka and existed until 

Holocene transgression.
64

Figure 33. East-West cross-section of the study area.

Core images are shown alongside mean grain size, loss on ignition (LOI) data, and dating results (cal BP are radiocarbon dates and ka are OSL dates) (Tables 2–

3). Inset displays site bathymetry (red and yellow are shallow depths, and blue and purple are deep) with cross section and core locations. Red dots indicate 

possible stump contacts imaged via side-scan sonar (Obelcz 2017). Duplicate cores from the same location (A and B) were collected for OSL dating first and then 

analyzed for micropaleontological data. The hatched areas in core images are void areas.
65

Figure 34. North-South cross-section of the study area. 

This figure is similar to Figure 33 with different direction across the study area. Peats are preserved in the north where relief was lower. The southern region did 

not preserve any peats and was populated instead by interbedded sand and mud, and paleosol facies.
66

A key requirement for the preservation of organic materials in sediments is anoxic conditions suppressing 

aerobic decomposition (DiMichele and Falcon-Lang 2011). Swamp environments, such as those in which 

bald cypress grow, commonly have stagnant waters with a low oxygen content that provide favorable 

conditions for preservation (Conner and Buford 1998). Ancient kauri (Agathis australis) stumps from 

New Zealand (Lorrey et al. 2018), and bald cypress stumps (early Holocene) of the Trinity-Sabine 

complex (Pearson et al. 1986) are preserved in similar peaty swamp sediments as the study site. Another 

possibility is rapid burial of a large volume of sediment from either river overbank flooding or sea-level 

transgression.

Whereas natural subsidence can account for the stumps being buried, subsidence of the study area is 

suggested to be minimal for the last glacial interval (Anderson et al. 2004, Bartek et al. 2004). The treering results found dendrochronological evidence that the stumps were buried rapidly. The tree-ring index 

ends in a single year, suggesting these trees experienced a rapid stress event that resulted in synchronous 

tree mortality (see section 3.5). These wood specimens provide evidence that the trees were presumably 

buried rapidly after this stress event because bark is generally shed first while the snag is still standing 

(Mobley et al. 2013). Such an event could be a hurricane causing tree death from saltwater intrusion 

(Middleton 2016).

If other locations on northern Gulf had similar geomorphology and environmental conditions, then other 

sites located within Gulf incised valleys at similar elevations may also contain preserved glacial age 

forests. Although younger in age, Pearson et al. (1986) demonstrated that the Trinity-Sabine complex on 

the Texas coast hosts preserved swamp deposits and wood that were possibly preserved in a similar way

to the stumps detailed in this study. Pearson et al. (1986) found bald cypress stumps located within the 

incised valley that were buried and preserved through Holocene transgression. They describe the 

landforms of the area, and they created a conceptual riverine model to associate landform types and 

preservation potential of deposits. They found pre-transgressive marsh deposits overlain by estuarine and 

marine sediments below the marine transgressive zone, in addition to the slopes of the Prairie/Beaumont 

terrace, such that there is a chance of site preservation due to the powerful wave erosion of the 

transgressive zone. Pearson et al. (1986) concluded that topography was the most important factor in site 

preservation, and subsidence and compaction were secondary. The Trinity-Sabine complex provides 

evidence that preservation processes at the study site are not localized but occur all along the northern 

Gulf Coast.

This study site provides a unique opportunity to examine changes within a subtropical environment 

during an interglacial-glacial cycle and the conditions that allowed for wood, pollen, seeds, and other 

organic materials to be preserved for more than 50,000 years. The forest was located within an area 

containing paleo-topographic lows that provided accommodation space for forest growth and sediment 

capping to preserve the forest from erosional processes of eustatic cycles during the last glacial cycle. The 

highest chance of finding additional stumps is to the west and northwest of the study area where peats are 

currently preserved based on analysis of reconstructed cross-sections of subseafloor stratigraphy. It is 

likely that a “bathtub ring” of other sites located within Gulf incised valleys at similar elevations were 

also preserved. Such locations may contain other well-preserved sediments, wood, and other artifacts that 

may provide further insights into paleo-oceanographic and paleoenvironmental studies of continental 

margins around the world.
67

4.5 Role of Sea Level Change in Forest Preservation

Radiocarbon and OSL results suggest the forest wood-bearing facies are between 74 and 42 ka occurring 

during MIS 3 and 4 (Table 2, Table 3). The eastern MAFLA has been interpreted as tectonically stable 

(~2.3 m subsidence/10 ka) (Bartek et al. 2004), but recent studies indicate that the entire northern Gulf

margin may deviate from the eustatic sea-level estimates due to continental levering associated with the 

Laurentide ice sheet (Love et al. 2016). However, these deviations are less than the potential elevation of 

the bald cypress when they were alive. Based on analogous contemporary environments and core 

lithology, the forest likely grew in a freshwater swamp within a low-lying river floodplain (Figure 35) 

(Conner and Toliver 1990). This floodplain could have been adjacent to a tributary river feeding into the 

main paleo-Mobile River, or the Mobile River itself. Either way, the relatively low elevation of a 

floodplain and a proximal fluvial source would provide the accommodation space and sediment supply

(Figure 26, Figure 27), respectively, necessary for the observed forest preservation state (Damsté et al.

2002).

Figure 35. Forest growth conditions. 

The approximate time period of forest growth is hypothesized to be 74–45 ka, based on a combination of eustatic sea 

level (inset modified from Waelbroeck et al. 2002), radiocarbon and OSL dates, cypress biogeography, and 

stratigraphy derived from cores and seismic data. In this diagram, D-D’ represents a vertical cross-section of arbitrary 

shallow depth, and a plan-view of lateral facies distribution is shown below. The forest is hypothesized to have grown 

in a relatively low-lying swamp in the floodplain of a Mobile valley tributary river; all of the topmost facies shown are 

hypothesized to have been deposited on top of bay-head facies formed during an older transgressive phase.
68

Assuming the postulated growth setting (Figure 35), forest burial could be associated with autogenic or 

allogenic events. An example of an autogenic burial would be a river crevasse splay that rapidly deposited 

a large mass of sediment on top of the forest (Shen et al. 2015), preventing degradation through aerobic 

respiration and/or exposure by erosion. Allogenic burial would involve external forces, such as rapid sealevel rise raising upstream river stage and promoting overbanking and associated floodplain aggradation 

(Shen Z et al. 2012). The relatively rapid sea-level rise of ~15 m over ~3000 years (~5 mm/year) between 

43 and 40 ka is a plausible driver of allogenic burial and is therefore favored in the working hypothesis. 

Regardless of mechanism, the net outcome is rapid and deep burial of the forest beneath a relatively 

impermeable sediment cap (Figure 36).

Figure 36. Forest burial conditions. 

The approximate time period of forest burial is hypothesized to be 40 ka or 62 ka, based on a combination of eustatic 

sea level (inset modified from Waelbroeck et al. 2002), radiocarbon and OSL dates, cypress biogeography, and 

stratigraphy derived from cores and seismic data. In this diagram, E-E’ represents a vertical cross-section of arbitrary 

shallow depth, and a plan-view of lateral facies distribution is shown below. The forest is hypothesized to have been 

rapidly buried by floodplain aggradation associated with the short sea level rise interval around 40 ka or 62 ka.

The forest survived the falling and lowstand sequence stratigraphic stages that favor the destruction of 

preexisting sedimentary strata (Van Wagoner et al. 1988). Assuming the forest was buried ~40 ka, the site 

would have been subaerially exposed for another ~30 ka. This includes the Last Glacial Maximum

(LGM) during which the climate was cooler and drier, i.e., conducive to eolian erosion and paleosol 

formation (Figure 37) (Rutter et al. 2017).
69

Figure 37. Forest preservation conditions at the Last Glacial Maximum (LGM). 

The forest was preserved in the buried sediments during the LGM when sea level was ~120 m below sea level, and 

the entire continental shelf was subaerially exposed to cooler, drier conditions (inset modified from Waelbroeck et al. 

2002) In this diagram, F-F’ represents a vertical cross-section of arbitrary shallow depth, and a plan-view of lateral 

facies distribution is shown below. The forest is hypothesized to have been sufficiently buried so as not to be 

subaerially exposed during lowstand erosion and paleosol formation.

After the LGM, deglaciation drove sea level rise and marine transgression. Sea level fluctuation is rarely 

linear, and high-frequency rises and falls in sea level are often superimposed on a larger-scale rising and 

falling trend (Siddall et al. 2003). This “transgressive belt sander” (D. Swift, pers. comm. 2017) moves 

the high-energy shoreline environment back and forth across preexisting strata. The MAFLA sand sheet is 

formed largely by transgressive processes (McBride et al. 1999), and the drowned forest must have been 

sufficiently buried and/or rapidly bypassed by the nearshore environment to avoid being integrated into 

the MAFLA sheet (Figure 38). After transitioning to a fully marine environment ~8 ka, the forest was 

evidently unperturbed until exposure coincident with the passage of Hurricane Ivan in 2004 (Figures 5, 

38). Now that the forest is exposed to the water column, degradation is apparent, and preservation is not 

expected. A synthesis of seismic and lithological data with the forest preservation hypothesis is presented 

in Figure 39.
70

Figure 38. The working hypothesis of drowned forest current conditions. 

The forest survived marine transgression and was subaqueously exposed by Hurricane Ivan in 2004. In this diagram, 

G-G’ represents a vertical cross-section of arbitrary shallow depth, and a plan-view of lateral facies distribution is 

shown below. The modern facies distribution is almost uniform sand sheet, with a small forest section exposed to the 

water column. Inset modified from Waelbroeck et al. 2002.
71

Figure 39. Profile synthesizing CHIRP and core data with forest facies and stratigraphy. 

A-A’ corresponds to the base map location in Figure 34 through Figure 37. CHIRP profile is shaded to correspond with major conceptual diagram facie groups: 

pink for Holocene sand sheet, green for Pleistocene swamp, yellow for all other Pleistocene facies, and blue for bayhead delta. White areas are locations of cores. 

Cores 15DF1 shown to the left with example facies and core gamma density profile (see Figure 17) and a picture core 16DF8B shown to the right with paleosols.
72

To better evaluate geographic relationships between the study area and the late Pleistocene shoreline 

locations, simple reconstructions of the coastal plain and continental shelf at various intervals for the 

dated sediments illustrating sea-level change, shoreline locations, and transgression-regression (Figure 

40). First, the time of glacial high and lowstands is identified using the Waelbroeck et al. (2002) global 

sea level estimates (Figure 3) that bracket the ages of sediments that have been dated. The relevant points 

in time are 80.0 ka, 65.0 ka, 60.5 ka, 44.0 ka, 39.5 ka, and 4.0 ka (for Holocene facies 2). Then, a regional 

digital elevation model (Love et al. 2018) was trimmed to highlight study area location and demark the 

land-sea boundary at each of those time points. This approach ignores topographic change by uplift, 

subsidence, sedimentation, and erosion from the last glacial to present, and also assumes that the 

Waelbroeck et al. (2002) global sea level record applies to the northern Gulf for this period, which is not 

well understood or documented (Donoghue 2011). Nevertheless, these illustrations schematically show 

the relative magnitudes of distances, elevations, and topographic gradients relating the study area to the 

location of the coastline for these past periods in time.

From 80 ka (Figure 40a) to 65 ka (Figure 40b), sea level fell from 20 mbsl (close to the study area) to 85 

mbsl exposing a new coastal plain >100 km wide measured at the shortest distance from the study area. 

During this time, the oldest floodplain deposits of facies 4 and the swamp deposits of facies 3, the late 

Pleistocene interbedded mud and peat, were deposited (Table 6). From 65 ka (Figure 40b) to 60.5 ka 

(Figure 40c), sea level rose to 48 mbsl, but because of the steep gradient of the outer shelf, the shoreline 

transgressed <15 km. During this time, the youngest dated deposits of facies 4 accumulated (Table 6). 

The period of 60.5 ka (Figure 40c) to 44 ka (Figure 40d) encompasses a sea-level rise of ~7 m near 54 ka, 

falling to ~76 mbsl near 44 ka. This produced an overall coastal regression on the order of 10 km from 

this elevation model. During this period, the younger (56 ka) paleosol (facies 5) developed and some of 

the dated swamp deposits of facies 3 accumulated (45 ka) in a topographic low west of the sampled 

paleosol. From 44 ka (Figure 40d) to 39.5 ka (Figure 40e), sea level rose ~14 m producing a transgression 

of <10 km during which time the peaty deposits of facies 3 continued to deposit. After 39.5 ka, sea level 

fell, with a pause near 32 ka, and then continue to fall until the LGM lowstand was attained. During the 

deglacial interval (18–10 ka), sea levels rose, and marine facies 2 was deposited and then covered by sand 

of facies 1 during the Holocene, thus preserving the forest remnants.
73

Figure 40. Geographical reconstruction of forest site evolution. 

Sea level model reconstructing the coastal plain and continental shelf at times during changes of sea level from the 

late Pleistocene to the Holocene. Regional data obtained from Love et al. (2018).
74

These reconstructions suggest that sediment deposition and accumulation in the study area could have 

occurred during five-time intervals recorded by the site’s geochronology. Three depositional intervals 

coincided with short pulses of sea-level rise at 42 ka, 56 ka, and 63 ka (Figure 3). One depositional 

interval coincided with a still-stand at 45 ka and one with falling stage 70 ka to 74 ka. The data are

insufficient to conclusively identify mechanisms for each case, but previous studies yield some 

suggestions. The first scenario, where deposition occurred shortly after pulses in sea level rise, has been 

extensively studied by Anderson et al. (2016) and Shen Z et al. (2012). Those studies showed that such 

rapid aggradation had been observed many kilometers inland in other coastal-plain alluvial valleys, where 

rivers aggrade rapidly in order to “keep up” with pulses in sea level rise. During MIS 5, an aggradation 

event occurred along the northern Gulf (Shen et al. 2015). Anderson et al. (2016) also observed congruent 

floodplain aggradation to rise in local sea level for small-to-medium-sized rivers along the northwestern 

Gulf Coast in Texas during the Late Pleistocene (MIS 5–3).

For the second and third scenarios, where deposition occurs during still-stands and falling stages, river

avulsion driven by regional gradients (Aslan et al. 2005) could produce autogenic burial, which could 

have been augmented by subsequent regional aggradation. For the third case, OSL ages clustered (Table 

3) at the start of a relatively short period of sea-level fall (late MIS 5 to early MIS 4, between Figure 40a 

and 40b), which was followed by another pulse of sea-level rise ~60 ka (Figure 3). In this case, floodplain 

aggradation due to sea-level rise soon after the dated sediments were deposited is not a plausible 

explanation. If the sediment ages are correct and immediate sediment burial did occur, then another 

mechanism needs to be involved other than immediate response to sea-level rise. The apparent elevation 

of the location above sea level ~60 ka (well below the elevation of the study area at that time) suggests 

that delta progradation is not a likely explanation. Autogenic avulsion driven by local river gradients 

could also enhance floodplain sedimentation, as occurs in low-gradient river systems (Aslan et al. 2005,

Bentley et al. 2016).

Swenson and Muto (2007) examined the response of coastal plain rivers to sea level and found that both 

degradation and aggradation can occur in one river system simultaneously during sea-level fall. This can 

occur when and where intrinsic timescale of sediment delivery matches the timescale of sea-level fall. In 

this case, sediment supply can be sufficient to produce aggradation in upper reaches of a catchment for 

the duration of the sea-level fall, but the seaward portion of the catchment experiences degradation 

(Figure 41). The rates of sea-level change addressed by Swenson and Muto (2007) (<1 mm/year) are 

much lower than rates evident in Figure 3 around the time of MIS 4 (rises and falls at rates of 4–5 

mm/year), but the relatively small spatial size of rivers feeding the study area suggests that they should 

have rapid response times as described by Swenson and Muto (2007). One final consideration is that the 

actual record of northern Gulf sea level change could differ from that of Waelbroeck et al. (2002) or the 

authors’ age models are incorrect or uncertainty too large, in which case the mechanisms for forest burial 

and preservation remain unknown.

Another key component of this hypothesis is that some accommodation spaces had to exist in order for 

thick packages of sediments to be deposited and therefore allow for forest preservation. This assumption 

is supported by the integrative digital elevation model (DEM) developed for the study site and the two 

underlying surfaces (Figure 26) where an accommodation surface is being created by the bottom surface 

dipping southwest.
75

Figure 41. Patterns of floodplain aggradation and degradation. 

Patterns identified by Swenson and Muto (2007) if the timescale of sediment supply approaches the timescale of sealevel change in a fluvial system, producing aggradation in upper reaches of the catchment, and degradation in 

seaward reaches of the catchment. Adapted from Swenson and Muto (2007).

In summary, the swamp sediments found in cores 15DF1, 15DF2, 15DF3B, 15DF4, 15DF4, 15DF5, 

15DF6, 16DF1D, and 16DF3A that are located in topographic lows are hypothesized to have been 

preserved and buried by fluvial/floodplain sediment accumulation. Accommodation for this sediment 

accumulation and preservation is indicated in the local divergence of the two lower seismic surfaces in 

Figure 26. Finally, as sea level rose and transgression occurred during the Late Pleistocene, sediments 

within the incised valleys were first eroded by transgression of the coastline and associated wave energy 

and later covered by Holocene shelf sands as sea level rose, thus causing the coastline position to retreat. 

Coastal wave erosion during transgression likely eroded high ground, but enough sediment layers 

remained to keep the cypress forest blanketed, therefore fortuitously favoring preservation.

4.6 Implications of Forest Model for Analogous Sites

This unique scenario where cypress tree stumps have been preserved for up to 70 ka represents a puzzling 

geologic setting that is possibly explained by relatively rapid and deep burial by floodplain aggradation 

that occurred for different reasons at different times. In three plausible cases, aggradation likely occurred 

as rivers responded to the pulsed sea level rise. In two additional cases, floodplain aggradation may have 

been out of phase with sea-level rise, and local sediment supply likely played a role in burying floodplains 

in inland portions of the coastal plain, while seaward portions of river valleys incised. Overall, these 

mechanisms for fluvial sediment accumulation prevented exposure by channel incision and coastal 

erosion during the latest Pleistocene regression and Pleistocene-Holocene transgression, thus preserving 

the tree stumps and wood debris.

Partial preservation of forests following sea-level transgression via wood debris, seeds, and pollen is 

fairly common and can provide paleoenvironmental and climatic information including species 

assemblage, aridity, temperature, and radiocarbon age (Hautevelle et al. 2006). However, preservation of 

an entire forest in growth position post-transgression is rare and provides information that fragments, 

seeds, and pollen cannot, such as dendrochronological records of interseasonal climate variation 

(Schongart et al. 2006). The hypothesis of forest growth setting, burial, and preservation conditions can 

serve as a model for discovering analogous environments, both along the northern Gulf and on other 

passive margins around the world.
76

The conjecture that the forest grew in a floodplain setting proximal to a river is based on analogous 

contemporary environments (Conner and Toliver 1990). Major river paleochannels are resolvable in 

seismic data, and well-mapped for many passive continental margins (Shaw and Courtney 1997, Schwab 

et al. 2014, van Heteren et al. 2014), therefore potential forest growth locations can be identified in many 

cases with preexisting maps. The other two major factors expected to dictate the abundance of analogous 

preserved forests are burial and post-burial erosion and disturbance.

If the forest detailed in this study was buried by widespread overbank flooding associated with eustatic 

sea-level rise, other still-buried preserved forests might exist as a “bathtub ring” proximal to 

paleochannels. If an autogenic process with smaller spatial extent, such as a river crevasse splay, buried 

the forest, the number of analogous sites may be lower.

Regardless of autogenic or allogenic forcing leading to forest burial, the existence of similar sites is also 

heavily dependent on surviving conditions unfavorable for stratigraphic preservation, including sea-level 

lowstand and transgression (Figure 37, Figure 38). The proximity of the drowned forest to the current 

shoreline may have aided its preservation, since sea-level rise rapidly accelerated 11,000 years before 

present (Love et al. 2016), reducing the amount of time the forest area was exposed to the “transgressive 

band saw.” For this reason, high-resolution constraints on sea-level fluctuation history should assist in 

identifying areas conducive to forest preservation.

This research suggests an approach that could help identify locations of other similar preserved forests of 

contemporaneous age around the Gulf. Due to the depth range of such forest preservation caused by the 

regional impact of sea-level rise and associated floodplain transgression, similar to the study area, a sort 

of “bathtub ring” could have formed around the Gulf at common age and depth. If this hypothesis is 

correct, each time a pulse in sea-level rise occurs there should be a backwater effect and floodplain 

aggradation event that occurs in response to that rise in sea level. These preserved sites should be 

concentrated offshore of modern river systems that would have incised the shelf at lower sea levels and 

deposited sediments during the phases of floodplain aggradation, such as the sediment accumulation that 

likely preserved the glacial-age forest.
77

5. Future Plans

The study used an Edgetech 4600 swath bathymetry and side-scan sonar system. The seabed bathymetry 

was measured, and large exposed tree stumps were identified by side-scan at the seabed surface. 

However, the CHIRP sub-bottom acoustic data collected using both Edgetech 0512i and 216 systems 

proved that neither the exposed nor buried tree features could be uniquely resolved using these systems. 

These instruments, operating in the range of 0.5 to 16 kHz, are capable of imaging largely buried 

structures, but they collapse responses from a 3-D environment into 2-D vertical slices and therefore 

provide no cross-dip information. To resolve this issue, the use of a 3-D CHIRP system is proposed for 

future work to resolve the tree stumps still buried at the site. Furthermore, this study recovered several 

cores with ~1 m of Pleistocene terrestrial sediments with peat that contain wood yet the digital elevation 

model (Figure 26) suggests there is more accommodation space that could contain more of these 

sediments, possibly up to 9 m in thickness. The recovery of long cores from the site would allow a better 

characterization of the paleoenvironment and provide a basement age control for the peat and woody 

sediments. Lastly, collection of seismic data from the northern Gulf region is proposed for marine isotope 

stage (MIS) 2 and 6 surfaces along with core data where wood was found. This information would be 

used to develop a prediction model of encountering wood at any depth within a core at a given location to 

quantitatively test the hypothesis that forest location is related to paleo-relief. This site represents a rare 

opportunity to study an easily accessible Pleistocene landform and develop a model to identify other 

possible outer continental shelf (OCS) locations with still buried forests.

Future fieldwork would enhance seabed survey methods and provide recommendations on survey tools 

and methods that might increase the chances of detecting such features. This information could be used 

by Bureau of Ocean Energy Management (BOEM) to (1) develop more effective survey methods for 

detecting and characterizing such seabed features, and (2) determine if environmental impact statements 

are necessary for such sites when relevant to proposed oil, gas, and dredging activities, or if categorical 

exclusion reviews are more appropriate.

Additionally, other sites have been identified in the northern Gulf. Buried wood was found in sediment 

cores south of Petit Bois, Mississippi. Stumps were found by Florida Fish and Wildlife south of Mexico 

Beach, Florida near one of the sites they monitor on a regular basis after Hurricane Michael made landfall 

in 2018. Pearson et al. (1986) examined the Trinity-Sabine complex on the Texas coast and found

preserved swamp deposits and bald cypress wood similar to this study but were Holocene in age. 

Investigating these other sites is the next logical step towards developing a research program focused on 

finding, identifying, and modeling where similar sites may occur on the OCS.

Obelcz is currently developing a geospatial prediction model for subsurface wood-bearing sediments 

using machine learning. (Figure 42). He is focusing on the Mississippi Sound area where he is cataloging 

seismic and core data with Rob Hollis of the US Naval Research Laboratory and Davin Wallace of the 

University of Southern Mississippi (USM) Department of Marine Science. They developed isopach maps

of the MIS 2 and MIS 6 surfaces underneath Mississippi Sound. They have the locations of other cores 

collected by USM and others that they analyzed for presence or absence of wood. The predictions made 

over the entire area shown in Figure 42 were trained and validated using observations in a relatively small 

area. Obelcz predicted encountering wood at any depth within a core at a given location, with the 

assumption that wood in core equals a higher probability for the preservation of buried forests. The 

predictors were depth to MIS 2 and MIS 6 surfaces, which is a way of quantitatively testing the study’s

hypothesis that forest location is related to paleo-relief. The prediction probability increases in areas of 

deeper MIS 2 and 6 surfaces as could be expected. The prediction is very inaccurate; it only made a 

correct prediction on 1 out of every 10 observations during 10-fold cross-validation, but he found the 

predictions that are inaccurate in bulk can still have instructive spatial trends. Overall, preliminary results 

are: 1) Different machine learning algorithms predict similar spatial trends, but differ in 
78

generalization/magnitude; 2) The probability of encountering wood is highest around fringes of paleoriver channels—this matches the location of the only preserved forest found in the northern Gulf to date; 

and 3) Paleo-slope curvature better correlates with wood presence than paleo-topography.

Figure 42. Preliminary predictions of other locations with wood bearing sediments. 

a) Isopach map of the MIS 2 surface and b) isopach map of MIS 6 surface for the Mississippi Sound area. c) 

Locations of the cores analyzed for the presence or absence of wood. d) Prediction of encountering wood at any 

depth within a core at a given location.

The primary objectives of a “phase 2” project are to refine the characterization of the study area located 

just off the coast of Alabama that contains well-preserved glacial-age bald cypress stumps in order to 

generate more precise information about its geological, geophysical, ecological, and paleoenvironmental 

characteristics. By placing the cypress forest site within the sedimentological context of the northern Gulf, 

this continued research would (1) determine the characteristics of the site that led to preservation, (2) 

provide a better understanding of depositional and geomorphic layout of the site, and (3) provide the 

opportunity to develop a model to predict other paleo-forest sites within the northern Gulf.

Hypothesis 1: High-resolution 3-D CHIRP geophysical surveys will be able to resolve exposed and 

buried tree stumps and logs not previously revealed in earlier surveys using different 

acoustic systems.

Hypothesis 2: Well-preserved woody remains in the sediments at the site suggest that similar 

depositional environments may contain potential archaeological sites even though this 

a b

c d
79

site is too old to contain archaeological materials. In the current study, the environment 

during the time when the trees were alive is hypothesized to have been slow to still 

waters with anoxic sediments that prevented decomposition thus preserving organic 

material.

Hypothesis 3: Previous pollen-based studies suggest the southeastern US was colder and drier during 

the glacial intervals yet none of these studies were conducted in regions that were 

coastal during the glacial intervals. Bald cypress stands can grow in swamps with slowmoving water thus lessening the potential transportation of pollen from other locations. 

In the current study, the northern Gulf Coast supported a robust subtropical bald 

cypress forest during the early glacial interval since the last interglacial.

Objective 1: Refine the methodology for identifying buried tree stumps and logs in the sediments.

Objective 2: Ground-truth geophysical survey targets using divers.

Objective 3: Collect cores at locations in the main site to obtain a deeper, continuous sedimentary 

record of Pleistocene sediments than was previously obtained and for new sites.

Objective 4: Expand the geophysical survey area to other known nearby buried tree sites.

Objective 5: Use established dating methods to compare the age of sediments and the subsequent 

sedimentation rates to estimate the ages of the in situ tree stumps.

Objective 6: Refine the paleoenvironmental setting of the preserved Pleistocene wetland forest using 

microfossils, pollen, seed, and wood analysis.

Objective 7: Develop a model to predict other buried forest sites on the northern Gulf OCS.

An additional project on shipworms in the exposed wood is planned by Dan Distel of the Marine Science 

Center at Northeastern University. Distel studies wood-associated marine organisms and their symbiotic 

bacteria. Distel was funded by the National Oceanic and Atmospheric Administration (NOAA) in 

September 2019 to conduct research on the wood and the shipworms. The project title is “Bioprospecting 

for industrial enzymes and drug lead compounds in an ancient submarine forest.” This study has the 

potential to inform this ongoing project on how long the wood has been exposed to the marine 

environment and if it has been previously exposed in the past ~15,000 years. DeLong will work with on 

the NOAA project as an advisor.
80

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Appendix A: Full foraminiferal counts from core 15DF1

Depth (m) 0.40 1.20 2.00 2.75 3.10 3.20 3.30 3.35 3.40 3.45

Soritids and Peneroplids Present Present Present Present Present Present 0 0 0 0

Quinqueloculina spp. 43 36 43 36 33 28 37 0 0 0

Other Miliolids 11 12 11 8 22 8 4 0 0 0

Rosalina spp. 83 83 60 67 103 63 70 0 0 0

Hanzawaia concentrica 41 47 43 39 27 64 30 0 0 0

Asterigerina carinata 21 13 39 27 15 18 23 0 0 0

Cibicidoides spp. 33 37 33 29 18 27 24 0 0 0

Nonionella spp. 11 10 11 11 19 7 16 0 0 0

Guttulina sp. 3 2 2 8 6 5 4 0 0 0

Bulimina spp. 1 0 2 2 13 1 2 0 0 0

Reussella atlantica 1 0 1 4 0 1 1 0 0 0

Buccella hannai 4 4 3 6 4 6 9 0 0 0

Haynesina germanica 6 10 1 3 1 3 3 0 0 0

Elphidium spp. 33 28 47 43 39 49 56 0 0 0

Ammonia parkinsoniana 3 6 5 6 4 5 5 0 0 0

Indeterminate 1 6 3 3 3 5 2 0 0 0

Textulariida 3 4 4 6 4 6 5 0 0 0

Planktonic 0 0 1 4 12 4 9 0 0 0

Planulina sp. 0 1 0 1 0 0 0 0 0 0

Fursenkoina sp. 0 1 0 0 1 0 0 0 0 0

Bolivina sp. 0 0 0 0 0 0 0 0 0 0

Oolina sp. 0 0 0 1 0 1 0 0 0 0

Cassidulina sp. 0 0 0 0 0 0 0 0 0 0

Eponides sp. 0 1 0 0 0 0 0 0 0 0

Amphistegina gibbosa 0 0 1 0 0 0 0 0 0 0
93

Depth (m) 0.401.202.002.753.103.203.303.353.403.45

Virgulina sp.0

0

10000000

Islandiella sp.1

0

00000000

Uvigerina sp.0

0

21000000

Total 300 302 314 306 325 302 300000

Abundance (individuals/g) 134.35 136.47 138.39 284.92 1625.00 144.15 185.30 0.00 0.00 0.00

Depth (m)3.50

3.55

3.603.653.703.753.803.853.904.00

Soritids and Peneroplids0

0

00000000

Quinqueloculina spp.0

0

40001000

Other Miliolids0

0

20000000

Rosalina spp.0

0 73

000 61000

Hanzawaia concentrica0

0 39

000 58000

Asterigerina carinata0

0 34

000 21000

Cibicidoides spp.0

0 41

000 26000

Nonionella spp.0

0 13

000 11000

Guttulina sp.0

0

50004000

Bulimina spp.0

0

20001000

Reussella atlantica0

0

20003000

Buccella hannai0

0

40009000

Haynesina germanica0

0

00000000

Elphidium spp.0

0 55

000 41000

Ammonia parkinsoniana0

0 10

000 11000

Indeterminate0

0

20003000

Textulariida0

0

50000002

Planktonic0

0

70005000

Planulina sp.0

0

00000000

Fursenkoina sp.0

0

00001000

Bolivina sp.0

0

00000000

Oolina sp.1

0

10000000

Cassidulina sp.0

0

10000000
94

Depth (m) 0.40 1.20 2.00 2.75 3.10 3.20 3.30 3.35 3.40 3.45

Eponides sp. 0 0 0 0 0 0 0 0 0 0

Amphistegina gibbosa 0 0 0 0 0 0 0 0 0 0

Virgulina sp. 0 0 0 0 0 0 0 0 0 0

Islandiella sp. 0 0 0 0 0 0 0 0 0 0

Uvigerina sp. 0 0 0 0 0 0 0 0 0 0

Total 1 0 300 0 0 0 256 0 0 2

Abundance (individuals/g) 0.70 0.00 73.10 0.00 0.00 0.00 44.82 0.00 0.00 3.05
95

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