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STUDY TITLE: Response of Later Quaternary Valley Systems to Holocene Sea Level Rise on the 

Continental Shelf Offshore Louisiana: Preservation Potential of Paleolandscapes

REPORT TITLE: Response of Later Quaternary Valley systems to Holocene sea level rise on the 

continental shelf offshore Louisiana: preservation potential of paleolandscapes

CONTRACT NUMBER: M12AC00020

SPONSORING OCS REGION: Gulf of Mexico

APPLICABLE PLANNING AREA(S): Western Planning Area; Central Planning Area

FISCAL YEAR(S) OF PROJECT FUNDING: 2012–2015

COMPLETION DATE OF REPORT: August 2019

COSTS: $225,000

PROJECT MANAGER(S): Paul V. Heinrich; Robert Paulsell; Richard P. McCulloh

AFFILIATION of Project manager: Louisiana State University; Louisiana Geological Survey Energy 

Center

ADDRESS: 1201 Elmwood Park Blvd, New Orleans, LA, 70123

PRINCIPAL INVESTIGATOR(S)*

: Paul V. Heinrich; Robert Pausell; Richard P. McCulloh

KEY WORDS: Quaternary Geology; Paleolandforms; Sea Level; Incised Paleovalleys; Archaeological 

Resource Preservation; Sand Resource Identification; Texas; Louisiana, Subbottom Sonar

BRIEF ABSTRACT: Understanding the complex response of coastal landforms to sea level rise is 

important for evaluating preservation potential of paleolandscapes and identifying sand resources on the 

Outer Continental Shelf (OCS). There is little to no preservation potential of coastal lithosomes seaward 

of the modern shoreface; however, there may be unique situations associated with fluvial aggradation 

and subsequent estuarine deposition within paleovalleys that could potentially provide an opportunity for 

preservation of buried geomorphic surfaces and intact prehistoric landscapes. The fluvial sediments 

underlying these terraces are inferred to be locally sand-prone channel bed and point bar deposits. This 

study provides a methodology for managing conflicts between the preservation of prehistoric cultural 

resources and the extraction of mineral resources by providing a basis for identifying and eventually 

mapping paleosurfaces with which significant cultural resources might be associated. The same 

methodology also provides a basis for mapping potential sand resources for use in coastal restoration.

BACKGROUND: BOEM is tasked with making available OCS resources for expeditious and orderly 

development in a manner that safeguards environmental and cultural resources. A number of uses of Gulf 

of Mexico resources, such as fishing, energy development, recreation, and sand dredging, may affect 

underwater cultural resources, such as historic shipwrecks and submerged prehistoric sites. However, 

little is known about early human occupation on the continental shelf and the potential for site 

preservation.

OBJECTIVES: The objective of the study is to develop a conceptual model for the modification of the 

northern Gulf of Mexico coastal plain from the Late Pleistocene through the Holocene transgression. The 

purpose of this model is to evaluate the preservation potential of coastal plain paleosurfaces as sea level 

submerged the Late Pleistocene coastal plain and transformed it into the modern continental shelf. An 
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integral part of this project was development of a GIS geodatabase for visual representation, data 

inventory tracking, and computational support.

DESCRIPTION: The first phase of this study consisted of collecting the existing subsurface data for the 

Southwest Louisiana OCS study area (Figure 1). Since the early 1980s, the data were collected for this 

region by Louisiana Geological Survey (LGS), Texas A&M University (TAMU), BOEM, Louisiana 

Department of Natural Resources (LaDNR), Louisiana Coastal Protection and Restoration Authority 

(CPRA), and U.S. Geological Survey (USGS). It included LGS and LaDNR sand resource survey studies; 

CPRA data for site specific sand borrow area prospecting; GIS files from Heinrich et al. (2015); USGS 

seismic data collected in 1994 and 1995; 2010 TAMU/BOEM vibracore data from the Sabine incised 

valley area; Rice University data; block surveys conducted for geologic hazards and cultural resource 

surveys; and bathymetry, and offshore platform and onshore geotechnical borings. Key geologic data 

(sediment cores and geotechnical borings) were used to constrain two-way travel time compared to true 

depth relationships and in evaluating stratigraphic and other interpretations made from the seismic data.

In the second phase of this study, an intensive examination was made of published literature concerning 

the geoarchaeology of the Louisiana OCS region and adjacent coastal plain. This material included peerreviewed literature, theses, dissertations, gray literature cultural resource management reports, and 

BOEM Environmental Study Program reports. Where found, useful paleogeographic and isopach maps 

were copied and later digitized for use in this project. The information gained from these sources was 

used to interpret the paleogeography, depositional-erosional history, and sedimentary processes within 

the study areas. This information, along with available core and seismic data, was also used in the 

construction of cross-sections and correlation of allostratigraphic units from onshore to offshore, and to 

interpret depositional facies, potential for sand resources, and the nature of contacts between 

allostratigraphic units. 

Finally, conceptual models for paleosurface preservation potential and paleovalley sand resource 

occurrence on the northern Gulf of Mexico OCS were produced based on the available data and concepts 

of sequence stratigraphy.
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Figure 1: Southwest Louisiana OCS Study Area.

References:

Heinrich P, Pausell R, Milner R, Snead J, Peele H (Louisiana State University, Baton Rouge, LA). 2015. 

Investigation and GIS development of the buried Holocene–Pleistocene surface in the Louisiana 

coastal plain. 140 p. Baton Rouge (LA): Louisiana Geological Survey. Contract No.: CPRA-2013-

T011SB01-DR. 

SIGNIFICANT CONCLUSIONS: Current offshore hazard and cultural resources survey requirements 

have significant shortcomings in terms of data collection (Figure 2). They focus on a “postage stamp size” 

(lease block) view that lacks integration into a regional framework. As a result, the absolute age of 

mapped fluvial and coastal landforms is determined by what is best described as the “count from the top” 

method, which is often inaccurate. If their ages were established with confidence, such fluvial features 

could be considered as potential sources of sand for coastal restoration.

There is inconsistency in the interpretation of seismic data regarding the identification of and 

nomenclature used to designate paleovalleys, channel belts, and paleochannels. This is an important 

distinction, because the expected distribution of cultural resources associated with a fluvial landform will 

vary greatly as to the type of feature. As a result, the accurate determination of the type of fluvial landform

is an essential step in evaluating the potential presence of cultural resources within a lease block.

The limited size of offshore hazard and cultural resources surveys and lack of an accessible regional 

seismic survey presented limitations to regional analysis. The lack of a usable regional overview creates 

large data gaps that prevent correlation of mapping from one group of lease blocks to another and the 

confident and detailed reconstruction of drainage patterns. Focusing on a single lease block or group of

lease blocks often overlooks or misinterprets the geomorphic context of the area.
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An overall lack of consistency was found in the interpretation of data, manner in which they were mapped,

and stratigraphic and geomorphic nomenclature used to designate features. In hazard and cultural 

resources survey reports, the specific criteria used to map the boundaries of fluvial landforms rarely were 

stated.

It was difficult to access and replicate previous interpretations of offshore hazard and cultural resources 

surveys because many of those surveys did not use a standardized method of drawing/labeling the 

seismic signature of each of the landforms mapped. There was no access to the original seismic data.

Figure 2: Distribution of paleolandforms in southwest Louisiana OCS Study Area, as mapped by 

OSC Hazard studies and Pearson et al. (1986).

References:

Pearson CE, Kelley DE, Weinsteing RA, Gagliano SM (Coastal Environments, Inc, Baton Rouge, LA). 

1986. Archaeological investigations on the outer continental shelf: a study within the Sabine River 

valley, offshore Louisiana and Texas. New Orleans (LA): US Department of the Interior, Mineral 

Management Service. 314 p. OCS Study MMS 86-0119. Contract No.: DI-14-12-0001-30072. 

Peltier WR. 2004. Global glacial isostasy and the surface of the ice-age Earth: the ICE-5G (VM2) model 

and GRACE. Annu Rev Earth Planet Sci. 32:111-149. 

STUDY RESULTS: Preliminary generalizations can be made about where paleosurfaces that might be 

associated with preserved cultural resources can be found. The important surface that is associated with 

preserved cultural resources is the Holocene-Pleistocene surface. The extent to which it is preserved and 

unmodified by relative sea level rise will be a major control on the preservation of cultural resources 

during the last and ongoing transgression. The primary location where this surface will be preserved is 

within deeply entrenched paleovalleys. The preservation of paleosurfaces within paleovalleys will depend 

on the rate and corresponding degree of modification that they experience from the transgressing bayline. 

Within the Pleistocene coast-parallel surfaces and associated Pleistocene and Holocene channel belts, 

shoreface erosion and ravinement surface formation may have extensively modified the HolocenePleistocene surface and any cultural deposits associated with it.
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It is theoretically possible that periods of very rapid sea level rise might have preserved strips of the 

Holocene-Pleistocene surface by the in situ drowning of existing barrier islands or chenier plains by a 

process known as step-wise retreat. In such cases, erosion of the beach ridges during the initial drowning 

and by later tidal action would have likely heavily reworked these beach ridges and destroyed any 

associated cultural deposits. However, as the shoreface jumps to its new location, lagoonal deposits and 

a strip of the Holocene-Pleistocene surface and any associated cultural resources underlying them might 

survive the transgression.

STUDY PRODUCT(S):

Heinrich, PV, Paulsell R, McCulloh RP (Louisiana State University, Baton Rouge). 2020. Response of 

Late Quaternary Valley systems to Holocene sea level rise on continental shelf offshore Louisiana: 

preservation potential of paleolandscapes. 104 p. New Orleans (LA): US Department of the Interior, 

Bureau of Ocean Energy Management. Report No.: BOEM 2020-004. Agreement No.: 

M12AC000020. 

Presentations and/or Posters:

Heinrich PV, McCulloh RP, Miner M, Paulsell R, Milner R. 2015 Mapping of Late Quaternary Paleovalleys 

on the outer continental shelf offshore Louisiana. Presented at: 31st Annual Louisiana Remote 

Sensing and GIS Workshop; May 12–13, 2015; Baton Rouge, Louisiana.

Heinrich P, Miner M, Pausell R, McCulloh RP. 2015. Late Quaternary stratigraphic evolution of the 

southwestern Louisiana inner continental shelf: paleo-landscape preservation potential and 

implications for offshore sand resources. In: Levine, S, editor. Transactions: Gulf Coast 

Association of Geological Studies. Vol. 65. Austin (TX): Gulf Coast Association of Geological 

Societies. p. 633.

Forthcoming: 

Geomorphology and Stratigraphy of the Ville Platte 30 x 60 Minute Geologic Quadrangle, southwest 

Louisiana

Geomorphology and Stratigraphy of the Port Arthur 30 x 60 Minute Geologic Quadrangle, onshore and 

offshore, southwest Louisiana

Stratigraphy and Geoarchaeology of St. Bernard Delta Lobe, Including Chandeleur Island, St. Bernard 

Parish, Louisiana.

*

P.I.’s affiliation may be different than that listed for Project Manager(s).