OVERSIZE 

(200) 

no INA 

c a 

Geomorphological Interpretations of Late 

Quaternary Terraces in Western 

Tennessee and Their Regional 

Tectonic Implications 

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1336-A 
90° 89° 

MISSOURI KENTUCKY 

New 

/1 Madrid\ I-

-11-N /

/ 

< < < 

Reelfoot 

Lake 

e,ez 

LIMIT OF 

? HOLOCENE 

UPLIFT ARKANSAS 

36° 

TENNESSEE 

0 30 km 

1 

Plan view of a hypothetical model relating patterns of seismicity, northeast-trendin g seismic zones: sawteeth indicate upthrown 

sense of fault movement, and the area of Holocene uplift in the side of inferred reverse faults: large solid-headed arrows indicate 

region of the New Madrid earthquakes of 1811-12. Barbed arrows direction of compression in region between northeast-trending en 

indicate a 1. the direction of maximum compressive stress: single echelon faults. Figure modified from Russ (1984). 

arrows indicate right-lateral displacement on faults of major 

COVER: Cypress trees along the shore of Reelfoot Lake in northwestern Tennessee. Reelfoot 

Lake. originally an oxbow lake in an abandoned Mississippi River meander, was substantially 

enlarged during the major New Madrid earthquake of February 7, 1812. 
		

		

Geomorphological Interpretations of Late 

Quaternary Terraces in Western 

Tennessee and Their Regional 

Tectonic Implications 

By ROGER T. SAUCIER 

THE NEW MADRID, MISSOURI, EARTHQUAKE REGION— 

GEOLOGICAL, SEISMOLOGICAL, AND GEOTECHNICAL STUDIES 

Edited by DAVID P. RUSS and ANTHONY J. CRONE 

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1336—A 

The morphology and gradients of four fluvial terraces 15:1fe !`\ ... 4 rs....... ' 

may indicate Quaternary uplift over a pluton in the 7 

. • ,•'..k \1;k /9// 1,, 0 New Madrid seismic zone ‘,X1 

' ,0 11371 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1987 
			

DEPARTMENT OF TH E I NTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas I.. Peck, Director 

Library of Congress Cataloging in Publication Data 

Saucier, Roger T. 

Geomorphological interpretations of late Quaternary terraces in western Tennessee and their regional tectonic implications. 

(The New Madrid, Missouri, earthquake region—geological, seismological, and geotechnical studies) (U.S. Geological Survey 

professional paper ; 1336—A) 

Bibliography: p. 

Supt. of Does. no.: I 19.16:1336—A 

1. Terraces (Geology)—Tennessee, West. 2. Geology, Stratigraphic—Quaternary. 3. Intrusions (Geology)—Tennessee, 

West. 4. Geology—Tennessee, West. I. Title. II. Series. III. Series: U.S. Geological Survey professional 

paper; 1336—A 

GB595.T2S28 1987 551.4'36'09768 87-600045 

For sale by the Rooks and Open-File Reports Section, U.S. Geological Survey, 

Federal Center, Box 25425, Denver, CO 80225 
FOREWORD 

The great New Madrid. Missouri, earthquakes of 

1811-12 and the extended series of aftershocks that 

followed have focused considerable U.S. attention on 

the geologic stability of the interior of the North 

American crustal plate. These and subsequent earthquakes have shown clearly that the mid-continent is 

capable of generating devastating earthquake ground 

motions and that study of these earthquakes is essential 

to reducing their associated hazards. This Professional 

Paper presents significant new contributions to fundamental knowledge about the seismicity, tectonic framework, and earthquake hazards of the New Madrid 

seismic zone. Some of the chapters refine the conclusions of earlier work, further clarifying the understanding of the seismotectonics of the region. 

As early as 1846, the eminent English geologist Sir 

Charles Lyell studied the effects of the earthquakes ul 

1811-12 and recognized the effects of recurrent earthquakes on the physiography and structure of the 

Mississippi Valley. The first comprehensive geologic 

investigation of the New Madrid earthquakes was 

made by Myron Fuller of the U.S. Geological Survey 

( S(;S). who published his findings in 1912. Fuller 

described the distribution and character of surface 

deformation and liquefaction features and compiled a 

detailed list of aftershocks and their effects. 

In 197.1. the USES began multidisciplinary studies 

to investigate the cause of the New Madrid earthquakes 

and to determine the hazards and risk associated with 

the continuing seismicity in the region. In the same 

year, the Department of Earth and Atmospheric 

Sciences of St. Louis University began installation of a 

16-station microearthquake-detection network in the 

Mississippi embayment (later expanded to 32 stations 

plus 8 additional stations in the Wabash Valley of 

Illinois and Indiana). The studies and seismograph 

network were designed to determine the temporal and 

spatial distribution of seismicity in the New Madrid 

seismic zone, to delineate the structural framework of 

the earthquake source zone, and to determine the 

recurrence rate of datnag- ing earthquakes in the New 

Madrid region by investigations of surficial sediments 

and structures. 

In 1977, the U.S. Nuclear Regulatory Commission 

initiated a multi-institutional seismotectonic study of 

the area within a 200-mile radius of New Madrid. The 

study was conducted by scientists from midwestern 

universities and State geological surveys, in coordination with Federal agencies conducting investigations 

in the area. The purpose of the study was to define the 

structural and tectonic setting of the New Madrid 

seismic zone in order to evaluate earthquake risks in 

the siting of nuclear facilities. Geological. engineering, 

and seismological studies for assessing earthquake 

hazards and risk associated with the Mississippi River 

and related waterways and manmade structures have 

been conducted independently by scientists and 

engineers of the U.S. Army Corps of Engineers. 

Results of many of the investigations corn pleted in 

t he first 8 years of study (197.1-82) in the northern 

Mississippi embaytnent were presented in US( ;S Professional Paper 1236. These studies revealed that 

earthquakes in the New Madrid area occur in linear 

zones that are spatially associated with structures in a 

buried continental rift that formed in the Precambrian. 

Reactivation of faults along the axis and flanks of the 

rift in a compressive stress field has produced uplift 

and many of the region's earthquakes. The buried 

Paleozoic surface has only minor structural relief, 

however. indicating that Cenozoic fault activity has 

been only modest or that most of the fault offset has 

been strike-slip. Earthquakes large enough to cause 

tectonic surface deformation and liquefaction features 

occur on the average of every 600-700 years in the New 

Madrid seismic zone. 

Geophysical. geological, and seismological investigations by scientists of the USGS. State geological 

surveys, academia, and the U.S. Army Corps of 

Engineers have continued in the New Madrid seismic 

zone since the publication of USES Professional Paper 

1236. Of particular importance have been seismicrefraction and seismic-reflection surveys: geomorphic 

analyses of river terraces and stream profiles in 

Tennessee, Kentucky, and Arkansas: and studies of 

earthquake-induced hazards such as liquefaction, 
IV FOREWORD 

landslides, and ground motion. Some of the new data 

and conclusions from these investigations are given in 

chapters published at irregular intervals as part of 

this Professional Paper 1336. These chapters provide a 

more complete understanding of the seismicity and 

tectonic evolution of the New Madrid region and the 

effects of hazards that the earthquakes produce; 

consequently, they will enhance the effort to implement 

loss-reduction measures in an economical and effective 

manner. 

David P.Russ 

Anthony J. Crone 

Editors 
CONTENTS 

Foreword 111 

Abstract 1 

Introduction 1 

Acknowledgments 2 

Regional setting 2 

Identification and delineation methods 4 

The terrace sequence 5 

Terrace morphology 5 

Finley terrace 5 

Hatchie terrace 11 

Humboldt terrace 12 

Henderson terrace 1:; 

Regional correlations 13 

Overview 18 

References cited 19 

ILLUSTRATIONS 

Pao 

FIGURE 1. Map showing locations of the five Mississippi River tributaries in western Tennessee whose terraces were studied for 

this report 3 

2-5. Maps showing the distribution of terraces along the: 

2. Obion River 6 

3. Forked Deer River 7 

4. Hatchie River 8 

5. Loosahatchie and Wolf Rivers 9 

6. Downvalley terrace and flood-plain profiles for the five rivers in western Tennessee whose terraces were studied for 

this report 10 

7. North-south Mississippi Valley profile A-A'—preferred interpretation 14 

8. North-south Mississippi Valley profile A-A'—alternate interpretation 15 

THE NEW MADRID, MISSOURI, EARTHQUAKE REGION— 

GEOLOGICAL, SEISMOLOGICAL, AND GEOTECHNICAL STUDIES 

GEOMORPHOLOGICAL INTERPRETATIONS OF LATE QUATERNARY 

TERRACES IN WESTERN TENNESSEE AND THEIR 

REGIONAL TECTONIC IMPLICATIONS 

B\ RO(;IIR 

ABS I R.1( 1 

By use of large-scale topographic maps and traditional techniques 

of geomorphology. a series of stream terraces was identified and 

delineated on the Obion, Forked Deer, Hatchie, Loosahatchie, and 

Wolf Rivers in western Tennessee. From lest and vnungeLA to 

highest and oldest, they are_des.iirnated the Finle.1.1.a v„ • chie_Hturi1:ioldt, and Benderson terraces. The areal extent and continuity of 

e3Frortt ese t r---qriMMa-rmtm are ample to permit reconstruction -'-

of former elevations and valley slopes. 

Downvalley gradients of the terraces and morphology are strongly 

indicative of the processes and events that influenced terrace 

formation. Nil gradients for several tens of kilometers upstream 

from the Mississippi alluvial valley on the Finley and Hatchie 

terraces and shoreline features on the Finley terrace are interpreted 

as evidence that backwater flooding from the Mississippi Valley 

produced extensive seasonal or permanent lakes in the tributary 

valleys. Therefore, in part. these terraces are relict la,2ustrine 

plains. The Humboldt and Henderson terraces do not have any of 

these characteristics and are interpreted as being entirely of fluvial 

origin. All terraces are capped by a veneer of loess representingone 

or more episodes of deposition. 

Interstream terrace correlations made by using only geomorphic 

evidence are not definitive, and two interpretations are nearly 

equally viable. One of these has potentially significant regional 

tectonic implications because it suggests Quaternary uplift in the 

vicinity of a known pluton along the flank of the major rift in the 

New Madrid seismic zone. However, the preferred interpretation 

suggests that no appreciable regional structural deformation has 

I • I .S. Army Engineer %Valet was Experiment Station, k,burg. NIS 39180. 

. FR I 

taken place. Neither interpretation indicates Quaternary deformation in the upland area relative to the Mississippi alluvial valley. 

Topographic relationships of the terraces to features resulting 

from the sequence of Pleistocene aggradation and degradation in 

the Mississippi Valley indicate correlation of the Finley terrace 

with the early Wisconsinan episode of outwash deposition. Several 

lines of evidence suggest correlation of the Hatchie terrace with the 

Prairie terrace of the lower Mississippi Valley, which is Sangamonian in age. By inference, the Humboldt terrace could be of 

Yarmouth ian age. 

INTRODUCTION 

In 1970, Saucier and Fleetwood called attention to 

the status of knowledge about Quaternary depositional 

terraces of fluvial origin in the Gulf of Mexico Coast 

and lower Mississippi Valley regions. At the time, 

problems were recognized in nomenclature, chronology, and regional correlations with the interpretations 

of Fisk (1939), but no alternatives to Fisk's work were 

widely accepted. Since then, the problems have increased to the point where some people are reluctant to 

accept the basic Fiskian terrace sequence. Studies of 

terraces (largely site specific) are continuing to produce 

information on details of lithology, sand and gravel 

source areas, faunal content, and absolute age, and 

this new information requires new concepts of terrace 

formation and chronology. 
2 THE NEW MADRID, MISSOURI, EARTI1Q[AKE REGION 

Ironically, although investigators are scrutinizing 

certain terraces and applying new techniques to 

squeeze more evidence from them, entire sequences in 

parts of the lower Mississippi Valley either have gone 

essentially unnoticed or have been ignored. For 

example, terraces in the Ouachita River area were 

first studied in the late 1960's (Fleetwood, 1969; 

Saucier and Fleetwood, 1970), and terraces along the 

Arkansas River and several other Mississippi River 

tributaries are still unstudied. Because all terraces 

were controlled by the same factors (for example, sealevel variations and base-level changes in the Mississippi alluvial valley related to glaciation and deglaciation), sound terrace concepts must be based on an 

appreciation of the nature and distribution of the 

entire terrace system. 

This paper is an initial attempt to reduce the basic 

knowledge deficit in one more part of the lower 

Mississippi Valley—western Tennessee. With only one 

exception (Smith, 1979), terraces in this area have 

received only passing mention in the technical literature (Saucier, 1964, 1974), and they have not been 

accurately delineated or recognized even on the latest 

and most detailed geologic map available (Miller and 

othcm 1966). To date, students of the Quaternary of 

wesrTennessee have focused almost exclusively on the 

origin of the upland gravel blanket (Potter, 1955; 

Roberts, 1928) and have not considered lower units 

that are more closely associated with present drainage. 

The information in this paper was obtained only by 

geomorphological analysis of the terraces based on a 

detailed examination of maps and aerial photographs 

and a general knowledge of the area. No field work 

was done, and no effort was made to collect subsurface 

information. No attempt was made to interpret terrace 

occurrence or characteristics in terms of variations in 

the hydrology of the drainage basins. Thus, field work 

and studies of hydrology and terrace lithology, petrology, paleontology, and other characteristics are desirable future endeavors that I hope will be encouraged 

by this initial paper. Such investigations would be 

relevant and timely in view of the recent resurgence of 

interest in Quaternary tectonism in the New Madrid 

earthquake zone immediately adjacent to the area 

considered in this paper (Russ, 1979). Terrace distribution and morphology and interstream correlations are 

valuable clues for deciphering the influences of external controls such as base-level changes, climatic 

change, and regional deformation. 

The rest of this paper contains descriptions of (1) the 

regional setting of the rivers whose terraces were 

studied, (2) the methods used to identify the terraces, 

and (3) the terraces themselves. These descriptions are 

followed by two possible interpretations of interstream 

terrace correlations and a discussion of how such 

terrace correlations may provide information on 

Quaternary events in the Mississippi alluvial valley 

and on Quaternary tectonism in the New Madrid 

seismic zone. 

ACKNOWLEDGMENTS 

I am grateful for the critical reviews of this paper 

and assistance in its publication provided by A.J. 

Crone, E.H. Grissinger, J.T. Hack, M.D. Harvey, D.P. 

Russ, S.A. Schumm, and B.R. Winkley. I also appreciate assistance in the preparation of the manuscript 

rendered by personnel of the Publications and Graphic 

Arts Division and the Environmental Information 

Analysis Center of the U.S. Army Engineer Waterways 

Experiment Station, Vicksburg, Miss. Approval by 

the Office, Chief of Engineers, for publication is 

acknowledged. 

REGIONAL SETTING 

Terraces along five westward-flowing rivers and 

their principal tributaries (called forks) in western 

Tennessee are the focus of this paper (fig. 1). Each 

river rises in hilly terrain in outcropping Tertiary and 

Cretaceous formations just west of the Tennessee 

River and crosses the eastern part of the Mississippi 

embayment to become tributary to the Mississippi 

River at the eastern edge of its Holocene alluvial valley 

(Cushing and others, 1964). These rivers have formed 

valleys of significant size in a westward-thickening 

sequence of poorly consolidated post-Paleozoic em bayment sediments that attains a thickness of about 700 m 

along the embayment axis near the Mississippi River 

(Zoback, 1979). 

In the eastern part of the area shown-in figure 1, 

north-northeast-trending Tertiary formations composed of sand, silt, clay, and lignite deposited in 

terrestrial to nearshore-marine environments compose 

the interfluves and are the source of the stream 

alluvium (Miller and others, 1966; Parks, 1971). Discontinuous deposits of fluvial sand, silt, and gravel of 

early Quaternary and late Tertiary age are present 

locally as remnants of once more continuous formations. 

In the western part of the area, west of a northnortheast-trending line through Jackson, Tenn. (fig. 

1), virtually the entire landscape is mantled with loess 

(Wascher and others, 1948; Miller and others, 1966). 

At least three episodes of deposition (Leighton and 

Willman, 1950) are represented in this westwardthickening loess layer. It reaches an average maximum 

thickness of more than 5 m at the edge of the Mississippi 

alluvial valley, and it has measured maximum thick-
		

LATE QUATERNARY TERRACES IN WESTERN TENNESSEE 

MISSOURI 

We • 

INDIANA

7 ILLINOIS 

KENTUCKY 

1 

TENNESSEE 

AREA SHOWN 

IN FIG. 1 Paducah • 

TEXAS 

MISSISSIPPI 

E MBA YMEN T 

LOUISIANA Poplar Bluff 

Of 

100 • 00 KM 

For k North 

Reelfoot Creek 

KENTUCKY 

TENNESSEE 

—1 

0 

Jackson 

LOOSahatChie R. 

Memphis 

TENNESSEE 

MISSISSIPPI 

Helena 

EXPLANATION 

C 

Pocono MISSISSIPPI ALLUVIAL 

VALLEY 

HOLOCENE MEANDER-BELT 

DEPOSITS WITHIN 

MISSISSIPPI ALLUVIAL 

VALLEY 

R. 

LATE WISCONSINAN 

STAGE GLACIAL OUTWASH 

EARLY WISCONSINAN 

STAGE GLACIAL OUTWASH 

Greenville 

• 

Greenwood 

PRAIRIE TERRACE OF 

FISK (1931, 1931) 

(SANGAMONIAN STAGE) 

MONTGOMERY TERRACE 

OF FISK (1931. 1939) 

(YARMOUTHIAN STAGE?) 

0 20 40 . 50 

KILOMETERS 

. 80 

e:* 

IGI'RE 1.--Locati0lsef the five rivers in western Tennessee whose terraces were studied for this report: the rivers heroine 

tributary to the Mississippi River near the eastern edge of its I lolocene alluvial valley. Also shown is the distribution 

of terrace, glacial-outwash, and 11010Cene Meander-heft depOSitS in part of the alluvial valley. 
4 THENEW MADRID. MISSOURI. EARTHQUAKE REGION 

nesses in outcrops of as much as 17 m (Wascher and 

others, 1948). 

The highest elevations'' (165 to 180 m) and the most 

maturely dissected terrain, in the form of a moderately 

hilly landscape, occur in the easternmost part of the 

area. Elevations and relief decline to the west. In a belt 

10 to 15 km wide a similar distance east of the 

Mississippi alluvial valley, elevations do not exceed 

120 m and the landscape is more gently rolling. 

However, immediately east of the alluvial valley, 

elevations are slightly higher (150 m or more), and the 

terrain is strongly hilly and steeply gullied. This 

terrain is a reflection both of the loess veneer, which is 

easily eroded, and of an inversion of topography 

caused by differential weathering of the Tertiary and 

Cretaceous deposits (Russ, 1982). 

All present drainage is well incised into the landscape, and major interfluves are 30 to 50 m above the 

flood plains of the major rivers. Average flood-plain 

gradients of the larger rivers range generally from 30 

to 45 cm/km; however, actual stream gradients are 

appreciably lower because the streams have tightly 

meandering patterns. The modern flood plains of the 

five rivers discussed in this paper are conspicuously 

wide and flat, so that the present rivers appear to be 

grossly underfit. However, the degree of fit is a 

complex matter subject to definition, age, stream 

behavior, and other factors discussed below. 

Of the five river systems examined, the Hatchie, 

Obion, and Forked Deer are the largest; each has a 

drainage-basin area of between 5,000 and 7,000 km2. 

The Loosahatchie and Wolf Rivers are considerably 

smaller, and each drains about 2,000 km2 (Lower 

Mississippi Region Comprehensive Coordinating Study 

Committee, 1974). Hydrologically, the five rivers are 

similar to other streams in this humid subtropical 

climatic zone, having a pronounced late winter-early 

spring discharge maximum that may be several 

hundred times the low-flow discharge. The mean 

annual flows of the streams range from 30 to 136 m3/s. 

IDENTIFICATION AND DELINEATION METHODS 

Large-scale (1:24,000) topographic maps published 

by the U.S. Geological Survey were the primary data 

source used to identify and delineate the terraces. In 

all, 105 maps were used, most of which had 10-ft (3.3-

m) contour intervals and supplemental half-interval 

contours for low-relief areas. A few maps of the more 

rugged eastern part of the area had 20-ft (6.6-m) 

contour intervals. Additional data of limited value 

were obtained from 1:62,500-scale mosaics of U.S. 

All elevations in this report are given in meters above sea level; that is, 

the National Geodetic Vertical Datum of 1929. 

Department of Agriculture air photographs taken at 

various times during the past several decades. 

Traditional techniques of geomorphology were used 

in terrace recognition. In the only previous mapping of 

note, Smith (1979) identified terraces solely by the 

construction of crossvalley profiles on which terrace 

position relative to the present river was determined. 

In my study, terraces were recognized from crossvalley 

profiles too, but additional recognition criteria included 

plan form, locations and configurations of escarpments 

and topographic breaks, degree of dissection, uniformity of elevations, relative height above flood 

plains, and drainage patterns. Modern county soil 

surveys, a normally valuable tool, exist for only a small 

part of the area. Consequently, they were of no appreciable value in this study. Another common criterion, land use, was not helpful because in this region, 

the physical landscape is not an important control on 

man's activities such as agriculture, road location, and 

settlement. 

An initial stage of map interpretation established 

the presence of terraces, their basic distribution, and 

topographic relationships. This stage included constructing preliminary downvalley profiles to determine 

slopes and elevations of mapped terrace segments. A 

subsequent stage was thereby possible in which the 

profiles were used to verify correlations and to reexamine the topographic maps for smaller or more 

obscure remnants not detected in the initial stage. The 

additional map data, in turn, were used to refine the 

profiles and fill data gaps. In questionable situations, 

this process was repeated several more times. To avoid 

undesirable bias in interpretations, each stage was 

completed for all five rivers before the next stage was 

initiated. 

The downvalley profiles represent an attempt to 

reconstruct original relict flood-plain elevations; thus, 

the elevations determined for given terrace segments 

may or may not precisely match present prevailing 

elevations. On the inner terrace margins (toward the 

upland interfluves), present average elevations usually 

exceed the determined original elevations because of 

the presence of well-developed alluvial fans and aprons. 

Along the outer terrace margins, erosion and stream 

dissection have resulted in present average elevations 

being lower than original elevations. I made subjective 

allowances for these conditions, and possible errors 

attributable to them are probably minor. A more 

important factor is the thickness of the loess veneer. 

The extent of loess on the terraces has not been 

determined; we do not know even whether the deposits 

are thicker on the older terraces or whether their 

thickness varies longitudinally along the valleys. 

Errors on the high side by an estimated 1 to 3 m in the 
LATE QUATERNARY TERRACES IN WESTERN TENNESSEE 5 

downvalley profiles may be present because of this 

ignorance about loess thickness. 

THE TERRACE SEQUENCE 

After the large-scale maps and downvalley profiles 

were completed, composite maps at a scale of 1:250,000 

were prepared for each river system. This synoptic 

view affirmed the presence of terraces of sufficient 

areal extent and continuity to warrant the designation 

of from two to four discrete terrace units or formations 

on each river system. On the basis of relative elevations 

and morphological characteristics (which are discussed 

more fully below), interriver correlations were apparent in this early stage of the investigation. I 

concluded that these correlations (although they have 

problems as discussed below) are sufficiently sound to 

justify the use of proper names for the terraces rather 

than the more tenuous and confusing alternative of 

alphabetic or numeric designations by river system 

(Smith, 1979). The four terraces named are, from 

youngest to oldest, the Finley, Hatchie, Humboldt, and 

Henderson. The Hatchie terrace was named for the 

Hatchie River, along which the terrace forms wide 

continuous outcrops. The Finley, Humboldt, and 

Henderson terraces were named for towns on the 

terraces (fig. 3). The terraces at the three towns and 

along the Hatchie River should not be considered type 

localities in the geological sense because I have no 

specific knowledge of the stratigraphy of the terraces 

at these or other localities. 

The composite mapping results are shown in figures 

2 through 5. Although the scale of presentation is 

small, the reader can feel safe in enlarging these maps 

to a more usable scale as they were compiled through 

photographic reduction and were carefully and accurately drafted. Because of limitations imposed by 

both the scale of the maps used for interpretation and 

the scale of the maps used herein for presentation, 

terrace remnants less than 1 km2 in area were not 

delineated. 

Some significant characteristics of these terraces 

are apparent from just their geographic distribution. 

All are paired terraces, indicating episodic responses 

to base-level control rather than continuous adjustment. 

Also, the younger (lower) terraces are generally better 

developed and better preserved along the lower reaches 

of the rivers. This preservation pattern suggests that a 

major base-level control was localized at the lower end 

of the rivers and was not uniformly regional. As is 

shown below, downstream divergence of terrace 

gradients supports the idea of localized base-level 

control. The active river flood plains have narrowed 

with time. This narrowing is particularly evident on 

the Hatchie River (fig. 4) where the modern (Holocene) 

flood plain is in places one-half to one-third the width 

of the oldest one as marked by the extent of the 

terraces. The Hatchie River terrace sequence is unique 

in several respects, one of the more obvious being the 

extent and continuity of the Hatchie terrace. 

TERRACE MORPHOLOCY 

The reconstructed downvalley profiles are critical 

to an understanding of terrace origin and well illustrate 

aspects of terrace morphology. Figure 6 is a compilation 

of profiles for each river system or major fork of a river 

system. Profile distances are measured along smoothed 

valley lines and are shown in plan in figures 2-5. For 

each river, kilometer 0 represents the extreme eastern 

edge of the Mississippi alluvial valley. In general, the 

profiles agree well with my interpretations of the 

crossvalley profiles constructed by Smith (1979); differences in detail are due to different methods used 

both in determining elevations and in correlating 

terraces. 

FINLEY TERRACE 

On all rivers, the Finley terrace is the youngest and 

the easiest to recognize and delineate because of its 

well-preserved flat surface and distinctive scarps 

separating it from both the Holocene flood plain and 

adjacent uplands or older terraces. At the valley 

mouths, the terrace surface is 3 to 7 m above the 

Holocene flood-plain level (fig. 6). From these points, 

the terrace extends upstream, at first with a characteristic nil gradient and thence, on all but the 

Loosahatchie and Wolf Rivers, with a very low gradient. 

Because this low gradient is less than that of the 

Holocene flood plain, the two eventually merge. Careful 

interpretations of maps and aerial photographs of the 

merger locations leave no doubt that the "terrace" 

extends further upstream, but thereafter it is buried 

(and locally reworked) beneath a progressively thickening veneer of Holocene alluvium. The greatest 

longitudinal extent of the Finley terrace as a topographic feature is on the South Fork of Forked Deer 

River, where it can be traced for more than 50 km (fig. 

3). 

One conspicuous aspect of the morphology of this 

terrace is the presence on the Forked Deer River, and, 

to a lesser extent, on the Obion River, of an actual 

reversal in gradient for several kilometers upstream 

from the Mississippi alluvial valley. Even with the 

limitations of the 10-ft (3.3-m) contour interval, the 

topographic maps show that the average terrace 

elevations at the immediate valley mouths are 1 to 2 m 
EXPLANATION 

HUMBOLDT TERRACE 

Fulton 

S Fulton \ 

• 

KENT VGKV 

TENNESSEE 1.511.MM1 

HATCHIE TERRACE 

FINLEY TERRACE 

30 .0 PROFILE DISTANCE. 

IN KILOMETERS 

1111BEACH-RIDGE COMPLEXES 

15' 

Utley 0Olon 

Dresden 

Gleason 

oiu 

u z 

al0 

6.1.0 

Ol! McKenzie 

Nee/been 

IS' 

0 

10 K dom.. * 

10 Stolid. Mies 

30. 00' 69°00' 30' 

THE NEW 

M ADRID, MISSOURI, EARTHQUAKE REGION 

FiGuRE 2.—Terraces along the Obion River. Downvalley profiles of terraces and flood plains for the North and South Forks are shown in figure 6. 
EXPLANATION 

HENDERSON TERRACE 1111111111 

F.]HUMBOLDT TERRACE 

HATCHIE TERRACE 

in 40 PROFILE DISTANCE. 

IN KILOMETERS 

*S' 

Bemis 

— 

10 Statute Wet 

5 0 

F-1 10 15 Kiwinetert Brownsville 

WOO' 

FIG FRE 3.—Terraces along the Forked Deer River. I)ownvalley profiles of terraces and flood plains for the North, Middle, and South Forks are shown in figure 6. 

LATE QUATERNARY TE

RRACES IN WESTERN TENNESSEE 
WOG' 

EXPLANATION 

HUMBOLDT TERRACE 

HATCHIE TERRACE 

0 10 Statute Mdse 1:11. FINLEY TERRACE 

5 0 10 15 

: 

Kolominers 30 4° PROFILE DISTANCE. 

IN KILOMETERS 

E NEW MADRID, MISSO

U RI, EART

HQUAKE REGION 

FIGURE,: 4.—Terraces along the Hatchie River. I)ownvalley profile for the terraces and flood plain is shown in figure 6. 
EXPLANATION 

[77-1 HATCHIE (OR HUMBOLDT') TERRACE 

FINLEY (OR HATCHIE") TERRACE I MA es 

IIII BEACH-RIDGE COMPLEXES 

as 41, PROFILE DISTANCE. 

IN KILOMETERS Cr: 

NOTE TO IMPROVE LEGIBILITY. 

THE CROSS-HATCHED PATTERN 

DENOTING THE EXTENT OF THE 

CITY OF MEMPHIS HAS BEEN 

OMITTED WHERE IT COINCIDES 

WITH A TERRACE SURFACE, 

ESPECIALLY ALONG THE WOLF 

RIVER 

RRA(' E S IN W E STERN TENNESSEE 

1110•30. 0 10 Statute MIN 110.00' 

10 15 Kilconsten 

F-1 1-1 1-1 

IGI;RE 5.—Terraces along the Loosahatchie and Wolf Rivers. Downvalley profiles of terraces and flood plains for both rivers are shown in figure 6. 

CD 
		

		

			

								 				

		

					

				

		

		

		 						

					

				

			 								 				

		

		

		

				

		

THE NEW MADRID, MISSOURI, EARTHQUAKE REGION 

C 

./ • 130 — 

120- 120— 

co 110 • ci110 — 

• 

Fs 100 — 

•- • -or • • 

a 

• 00 2 

100_,•.-. v • 

ps i 

". 0 o O

90- 0 0 

NORTH FORK 

> 90 0 0 0 ------

SOUTH FORK — 

OBION RIVER OBION RIVER so— — so— — 

I.... 

O 101 20 

I I 

30 

i 

40 I 

50 

I 

60 

I 

70 

I 

80 

I 

90 

I 

100 I 110 _J 120 L.. 0 

I 

10 I 20 I 

30 

I 

40 

I 

50 

I 

60 

I 

70 

I 

80 I 90 _J 100 

PROFILE DISTANCE, KILOMETERS PROFILE DISTANCE, KILOMETERS 

140- 140 — 

130— NORTH AND MIDDLE FORKS 130 a— 

FORKED DEER RIVER 

C 2 120 — rf: 120 A 

i ,,c

O 110 — ... 110— PAN .- ZO 

P ...-11"-. 06) ( 0, ....-- a; 100— . C •--ii ,

.„.

e.•°' 100 — . .4o- • irr vs" L7 .....-• a NO -4r •—11 ...40 • • e- - - 90— SOUTH FORK A 7— -- — —•- — A x---x-4.- — 

90_ 

x FORKED DEER RIVER so — eo — — 

L I I I I I I I J L I I I I I I I I I I I 1 O 10 20 30 40 50 80 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 110 120 

PROFILE DISTANCE, KILOMETERS PROFILE DISTANCE, KILOMETERS 

130 — 

B 

120 — 

LOOSAHATCHIE RIVER IN 100 —

• 

eo— HATCHIE RIVER A 7 

ELEVATION, METERS

90 — 

eo — 

." 

70 — 

ELEVATION. METERS 

I J eo L I I I I I J 10 20 30 40 50 60 70 80 90 100 110 120 130 140 0 10 20 30 40 50 80 

PROFILE DISTANCE, KILOMETERS PROFILE DISTANCE, KILOMETERS 

EXPLANATION 

OLDEST AND HIGHEST ••—••—••— D HENDERSON TERRACE 

•—•—•— C HUMBOLDT TERRACE 

B HATCHIE TERRACE 

YOUNGEST AND LOWEST --- — A FINLEY TERRACE 

CrGr 

—*7°E WOLF RIVER 

eoL I I I I I J O 10 20 30 40 50 60 

PROFILE DISTANCE, KILOMETERS 

H6I . RE 1)1) wIlvalleY Profiles of terraces and flo"(1 Plains fur the five rivers in Western Tennessee whose terraces were studied for 

this report. Elevations in meters above mean sea level. 

70 
LATE QUATERNARY TERRACES IN WESTERN TENNESSEE 11 

higher than those a short distance upvalley; hence, a 

slight "lip" is present at the edge of the Mississippi 

alluvial valley. Morphologically, this could be cited as 

evidence of Mississippi Valley alluvium:3 that was 

introduced into the mouths of the tributary valleys. 

however, at least some of the sediments in this area 

have been identified as loess (D.P. Russ, 1983, written 

commun.). 

Along the Obion and Loosahatchie Rivers (figs. 2, 5), 

features tentatively identified as beach-ridge complexes have been delineated. These are linear zones 

characterized by parallel ridges and swales that occur 

at the upland scarps. They have reasonably accordant 

crest elevations about 6 m above the average Finley 

terrace surface elevation. In all morphological aspects, 

they resemble the lake beaches and bars that have 

been described from along the Ohio, Tennessee, and 

Clark Rivers in Kentucky and Illinois (Finch and 

others, 1964) and the Ouachita River in Louisiana 

(Saucier and Fleetwood, 1970). 

The terrace topography, nil gradient, and probable 

beach ridges indicate that the downstream parts of the 

Finley terrace are primarily of lacustrine-plain origin. 

The lakes that produced the terrace resulted from the 

damming effect of an episode of rapid sedimentation 

(outwash deposition) and high flood stages in the 

Mississippi alluvial valley. The lakes probably were 

perennial, representing a mixture of local runoff and 

Mississippi Valley backwater flooding. As outwash 

deposition in the Mississippi Valley likely was highly 

variable and episodic, the lake stage must have 

fluctuated appreciably. Both living and drowned floodplain swamp forests must have been present periodically to varying extents. 

As indicated above, this region has a loess veneer. 

Therefore, lacustrine sediments probably do not occur 

at the present terrace land surface except locally 

where the loess has been eroded. 

In 1979, Smith mapped the Finley terrace as two 

units, his T1 and T91, levels. This recognition of two 

levels is easy to understand because of the abovementioned features (for example, beach ridges) that 

occur at different elevations and because he did not use 

continuous delineation techniques. 

At scattered localities along each river, both the 

upland terrace margin and the margin adjacent to the 

Holocene flood plain have the form of smooth arcuate 

scallops. The size and configuration of the scallops, the 

';"Mississippi Valley alluvium" is used intentionally rather than "Mississippi 

River alluvium." The Mississippi River probably remained west of Crowleys 

Ridge in the Western low lands until late Wisconsinan time. Prior to this time. 

the part of the Mississippi Valley east of ('rowleys Ridge (the St. Francis 

Basin) was occupied by the Ohio River and local drainage. 

occasional presence on the lower level of faint traces of 

point-bar accretion, and several relict abandoned 

channels clearly indicate that these features resulted 

from lateral migration by a meandering stream. The 

radii of these features suggest that the relict streams 

may have had discharges significantly larger than 

those of the present rivers. 

As is discussed below, a widely distributed terrace 

in the Gulf of Mexico and Atlantic Coastal Plains was 

formed by streams carrying appreciably higher flows 

than those carried during the Holocene. Designated 

the Deweyville terrace (Gagliano and Thom, 1967; 

Saucier and Fleetwood, 1970), it attests that the fluvial 

systems showed at least one major regional response to 

effectively increased precipitation during the late 

Quaternary. In the western Tennessee area, the scallops 

at the lower and upper Finley terrace margins indicate 

that two such episodes may be in evidence, one necessarily predating the formation of the lakes and one 

postdating them. 

HATCHIE TERRACE 

In the five river systems studied, the Hatchie terrace 

areal ly is the best preserved. On the river of the same 

name, its extent is dramatic (fig. 4). This terrace most 

closely corresponds to the Tal level as identified by 

Smith (1979). It is restricted to the more downstream 

parts of the Obion River (fig. 2) and the North and 

Middle Forks of Forked Deer River (fig. 3), but on 

other rivers, it can be traced well upstream toward the 

headwaters (figs. 4, 5). 

Along the Hatchie River, one contiguous segment of 

this terrace extends for more than 45 km along the 

valley and averages 3 to 4 km in width (fig. 4). The 

surface in this area is flat to slightly undulating, and 

extensive swampy tracts are interrupted by low, 

irregular knolls and ridges. Drainage from the uplands 

crosses the terrace in numerous tortuous channels in a 

chaotic pattern. The morphology alone does not provide 

enough evidence for speculation about the origin or 

origins of the irregular topography. However, as 

suggested by Smith (1979), excessive sedimentation 

resulting from 19th century land clearing and development may be at least in part a causal factor. Postsettlement alluvium has been documented as a major 

flood-plain element in other drainage systems in the 

Mississippi Valley area (Grissinger and others, 1982). 

On the other rivers in Tennessee, the topography on 

the Hatchie terrace is strongly influenced by the 

presence of alluvial fans and aprons, and local drainage 

is better developed. 

The Hatchie terrace is similar to the Finley terrace 

in most other morphologic aspects. On all but the 
12 TIiE NEW MADRID. MISSOURI. EARTHQUAKE REGION 

Loosahatchie and Wolf Rivers, it also exhibits distinctive nil gradients in its lower reaches (fig. 6). However, 

although the Hatchie terrace does approach floodplain levels because of the convergence of the gradients, 

it always remains at least a few meters above floodplain levels and nowhere is a buried feature. At the 

mouths of the rivers, the terrace elevations are between 

10 and 15 m above the present flood plains. As can be 

seen in figure 6, the Hatchie terrace has slightly lower 

average elevations upstream from the immediate 

mouths of the Obion, Hatchie, and Forked Deer Rivers 

and, thus, has "lip" features like the Finley terrace. 

No beach-ridge features have been identified in 

association with the Hatchie terrace. Nevertheless, it 

is reasonable to interpret the downstream segments of 

this terrace on the Obion, Forked Deer, and Hatchie 

Rivers to be of lacustrine-plain origin like the downstream parts of the Finley terrace. Upstream where it 

has positive downstream gradients, the Hatchie terrace 

represents the relict flood plains of an earlier phase of 

the respective rivers. 

On the Loosahatchie and Wolf Rivers, the Hatchie 

terrace lacks the evidence for lacustrine-plain origin 

as indicated above (fig. 6). A possible explanation for 

this lack involves the locus of rapid outwash deposition 

in the Mississippi alluvial valley responsible for the 

damming effect. Perhaps it was farther west in the 

valley some distance from the mouths of these rivers 

rather than right along the valley margin. Hence, 

backwater flooding and impoundment may have been 

absent along these rivers or less pronounced than 

impoundment along the Obion, Forked Deer, and 

Hatchie Rivers. Supporting this view is the observation 

that on the next four river systems south of Wolf River 

(the southernmost of which is 100 km from Wolf 

River), the lowest terrace has a positive downstream 

slope rather than a nil slope or reverse gradient. On 

the other hand, however, another explanation is that 

the terrace identified as the Hatchie terrace on the 

Loosahatchie and Wolf Rivers is actually a higher and 

older terrace that does not correlate with it. This 

problem is explored more fully in the next section of 

this paper. 

The distribution of the Hatchie terrace within river 

systems is variable. Although it is evenly distributed 

along both sides of the Forked Deer and Wolf Rivers 

(figs. 3, 5), its distribution along the Obion, Hatchie, 

and Loosahatchie Rivers (figs. 2, 4, 5) is highly asymmetrical. The reason for this asymmetry is not 

apparent. Structural control or uneven distribution of 

sediment-contributing tributaries sometimes can cause 

these conditions (Saucier and Fleetwood, 1970), but 

these factors do not appear to be influential in this area 

except locally. 

Characteristics of the Hatchie terrace, especially its 

areal extent, suggest that the terrace formed during 

an unusually long period of geomorphological stability. 

If we exclude unlikely increases in the rates of fluvial 

activity or basin sediment yield, the inferred volume of 

sediments contained in the terrace suggests that it 

formed during a period considerably longer than that 

required for formation of the present (Holocene) flood 

plain. 

An area of uncertain terrace identification involving 

the Hatchie terrace occurs between profile stations at 

40 and 55 km along the North Fork of the Obion River 

(figs. 2, 6). Two areas of terrace, one on each side of the 

river, have been mapped as Hatchie terrace; however, 

their reconstructed elevations are anomalously high in 

view of the trend of more downstream segments. The 

present most tenable explanation for this anomaly is 

local structural control. Shortly after the terrace 

mapping was completed, I learned that a pronounced 

scarp, oriented along a northeast-trending lineament, 

has been noted in this area and tentatively identified 

as a late Pleistocene fault (Tennessee University, 

Martin, 1981). The scarp is coincident with the 

northeast-trending Hatch ie-Humboldt terrace contact 

south of Tennessee Highway 22 about 7.2 km southeast 

of Union City, Tenn. (fig. 2). Until more study is done, 

we can only speculate about the influence of this likely 

fault; however, it may have resulted in the downward 

displacement of a segment of this terrace on the order 

of 4 or 5 m. 

HUMBOLDT TERRACE 

The Humboldt terrace is more difficult to map than 

the Hatchie and Finley terraces are because the 

exposures are smaller and less continuous and the 

surface is more dissected. Nevertheless, it has been 

identified on all but the Loosahatchie and Wolf Rivers 

(figs. 2-4). Its best exposure regionally is farthest to the 

north (Obion River) and declines southward. Geologists 

working in the region think that subsurface evidence 

indicates the presence of a higher terrace in the 

Memphis, Tenn., area that could be the Humboldt 

terrace (I).P. Russ, 1982, oral commun.). However, I 

could not map it on the basis only of physiographic 

evidence although I intuitively feel that it is there. In 

contrast, this terrace was not identified by Smith 

(1979), who did not extend his crossvalley profiles to 

elevations high enough to detect this terrace. 

Morphologically, this terrace lacks any clues as to its 

mode of origin; it has no discernible features such as 

relict channels or meander-belt ridges or lake-shoreline 

features. Reasons for the lack of clues are postdepositional erosion, significant alluvial-apron development 
LATE QUATERNARY TERRACES IN WESTERN TENNESSEE 13 

where the terrace abuts the uplands, and a loess 

veneer of unknown thickness. 

As in the study of the other terraces, in this study, 

downvalley profiles present the most useful information. Figure 6 reveals that the reconstructed surfaces 

of the Humboldt terrace generally parallel the Holocene flood plains at a height of 10 to 20 m. Downstream 

reduction in gradients occurs on the Obion and Forked 

Deer Rivers; however, nowhere does the terrace have a 

nil gradient. This lack of a nil gradient is interpreted 

to mean that lacustrine conditions due to backwater 

flooding from the Mississippi Valley did not exist or at 

least did not influence this terrace as it influenced the 

lower terraces. The Humboldt terrace is considered to 

be strictly a relict fluvial depositional feature. 

Within any river system, the Humboldt terrace 

exposures are not noticeably asymmetrical. They occur 

on both sides of the present rivers, and their distribution indicates that the valleys were two to three times 

wider than at present when the Humboldt terrace was 

the active flood plain. 

HENDERSON TERRACE 

The Henderson terrace is limited to the upstream 

parts of the three forks of Forked Deer River (fig. 3). 

Its exposures are sufficient to make its identification 

as a terrace certain, and its relationship to the 

Humboldt terrace as a separate higher level is reasonably well established (fig. 6). Otherwise it provides 

more questions than answers. 

Because it is the most highly dissected terrace, its 

restriction to the Forked Deer River may be only an 

artifact of the mapping procedure. On the other hand, 

as it is the oldest terrace, much of its original distribution may have been destroyed during subsequent 

cycles of valley degradation and aggradation and 

flood-plain formation. 

REGIONAL CORRELATIONS 

Construction of a generalized profile along the axis 

of the Mississippi alluvial valley, profile A-A' as 

located i n figure 1, was necessary to correlate terraces 

among the tributaries and to establish relationships 

between these terraces and features in the alluvial 

valley resulting from major depositional events there. 

Two separate interpretations were derived from the 

data, each of which is plausible enough to warrant 

discussion. Figures 7 and 8 present the preferred and 

alternate interpretations of interstream correlations 

of terraces as they relate to the features in profile A-A'. 

Individual terrace and depositional-level profiles 

for the alluvial valley shown in these interpretations 

were constructed by projecting elevations on these 

surfaces to profile A-A' normal to the trend of this line 

(fig. 1). As was done in constructing the terrace 

profiles along the tributaries (fig. 6), judgment was 

used to reconstruct probable original maximum elevations. Such reconstruction was done for all the levels or 

terraces east of Crowleys Ridge that represent 

maximum levels of aggradation for various intervals 

during the Wisconsinan Stage as taken from Saucier 

(1974). 

The part of the alluvial valley for which profile A-A' 

was constructed received large volumes of glacial 

outwash from braided streams during the early waning 

stages of both the early Wisconsin (Altonian Substage) 

and late Wisconsin (Woodfordian Substage) glaciations 

(Saucier, 1974). Maximum valley aggradation occurred 

relatively early in each phase of waning glaciation 

when sediment loads were high, and degradation 

occurred subsequently as the ratio of sediment to 

meltwater declined as the ice front receded northward. 

This cycle produced the several recognizable levels of 

outwash or braided-stream terraces that characterize 

the pre-Holocene parts of the St. Francis Basin (fig. 1). 

Flood plains or deposits older than the Wisconsinan 

Stage (for example, the Prairie terrace of the Sangamonian Stage) are absent in this area except for small 

erosional remnants at the mouths of small creeks on 

Crowleys Ridge. These are too few and too small to 

allow a profile to be constructed. 

Profiles for the Finley, Hatchie, and Humboldt 

terraces shown in figures 7 and 8 represent interstream 

correlations of the elevations of these relict flood plains 

where they joined the Mississippi alluvial valley. The 

length of profile A-A' was chosen to permit consideration of terraces and levels upvalley and downvalley 

beyond the mouths of the five rivers discussed. Southward, the profile extends 100 km beyond the mouth of 

the Wolf River so that the Little Tallahatchie River is 

included; northward, it extends about 25 km beyond 

the mouth of the Obion River so that Reelfoot Creek is 

included. I did not delineate any terraces on the 

several Mississippi River tributaries north of Reelfoot 

Creek in Kentucky, although some are reported to be 

present (D.P. Russ, 1982, oral commun.). 

Figure 7 presents the terrace correlation I prefer as 

being relatively more consistent with the observed 

geomorphic evidence. However, this interpretation 

does pose possible problems as discussed below. This 

preferred interpretation was the basis for the designations of the terraces used in the mapping shown in 

figures 2 to 5 and the profiles shown in figure 6. 

As shown in figure 7, the lowest terrace on each of 

the five river systems is identified as the Finley 

terrace and the next highest one as the Hatchie 
NONCONNAH CR 

COLDWATE

RR -

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o ti,, -J I:I 

I 

U 

A 

REELFOOT CR 

HATCHIER

I- 2

W A' Ia ca :1-, 4 4 < ZO CC >t N J . _, 4 0 8 2 II 

110 - — 110 

• 0 a ELEVATIONS OF DOWNSTREAMMOST REMNANTS OF 

TERRACES, ON INDICATED STREAMS, PROJECTED 

TO PROFILE. 

100 — 99 

98 LEVELS OF EARLY WISCONSIN GLACIAL OUTWASH 

(BRAIDED-STREAM TERRACE I) IN THE ST FRANCIS 

—100 

BASIN (FROM SAUCIER, 1974). 

LEVELS OF LATE WISCONSIN GLACIAL OUTWASH 

90 — 

_ 90 (BRAIDED-STREAM TERRACE 2) IN THE ST FRANCIS 

BASIN (FROM SAUCIER, 1974). —90 

0- 16 

, 

• .Z‘ e 

80 — C...A.C 

11- "" "1" • 7 

x 

6 

E 

7S 

—80 

69 — 70 

W 

mow'R - - .41,4-.9-40( &fro/44 

60 — e;VCC A44,11( CREST-.44,4-se:V1-4e/SS —60 

— 50 50 — 

—40 40 — 

0 20 40 60 80 i00 120 140 160 180 200 220 240 260 

PROFILE DISTANCE, KILOMETERS 

FIGURE 7.—North-south Mississippi Valley profile A-A'—preferred interpretation. Elevations in meters above mean sea level. For location of profile, see figure 1. 

NOIDHII HX

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HVziflOSSIlk 'CIIIICIVIN MINIH H,L 
		

		

		

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I 

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MEMPHIS 

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— 110 110 — 

• 0 x ELEVATIONS OF DOWNSTREAMMOST REMNANTS OF TERRACES, ON INDICATED STREAMS, PROJECTED 

TO PROFILE. —100 100 — 99 00--- LEVELS OF EARLY WISCONSIN GLACIAL OUTWASH (BRAIDED-STREAM TERRACE 1) IN THE ST. FRANCIS 

BASIN (FROM SAUCIER, 1974). 

0 0-- LEVELS OF LATE WISCONSIN GLACIAL OUTWASH (BRAIDED-STREAM TERRACE 2) IN THE ST FRANCIS —90 BASIN (FROM SAUCIER, 1974). 

— so 

69 — 70 67 

63 OW 104 4fre'94°':1:1?:(11o?esr 

PENCE ~DG „ gESE —60 60 

........... ... ..... 

..... ....... — 50 50 --

—40 40 — 

1 oo 120 140 160 180 200 220 2401 1 

PROFILE DISTANCE, KILOMETERS O 20 40 60 80 l 260 

FIGURE 8.—North-south Mississippi Valley profile A-A'—alternate interpretation. Elevations in meters above mean sea level. For location of profile, see figure 1. 

LATE QUATERNARY TERRACES IN 

WESTERN TENNESSEE 
16 THE NEW MADRID. MISSOURI. EARTHQUAKE REGION 

terrace. Lines connecting the farthest downstream 

points on the terraces on each of the rivers produce 

smooth profiles that are comparable in configuration 

and slope to the braided-stream terraces and depositional levels in the Mississippi alluvial valley. This 

similarity is to be expected if the assumption is correct 

that events in the alluvial valley established the base 

levels to which the tributaries responded. 

According to the interpretation in figure 7, the 

Humboldt terrace is absent along all rivers south of 

the Hatchie River. Possible explanations for its absence 

are that the terrace never existed in this area, that it 

has been destroyed by erosion, or that it was unidentifiable by the mapping techniques discussed above. I 

believe that remnants of the Humboldt terrace are 

present south of the Hatchie River, but that because of 

the decreasing interfluve elevations and other factors, 

they are not recognizable on topographic maps and 

aerial photographs. Supporting this view is the opinion 

of others, based on field evidence, that remnants of this 

terrace may be present on both the Loosahatchie and 

Wolf Rivers (G.P. Smith and D.P. Russ, 1982, oral 

communs.). 

In my opinion, another possible unresolved problem 

with, or weak point in, this interpretation (fig. 7) is the 

correlation, as the Hatchie terrace, of terraces on the 

Obion, Forked Deer, and Hatchie Rivers that have a 

nil gradient with ones on the Loosahatchie and Wolf 

Rivers that have a positive gradient in their lower 

reaches. It could be argued that all rivers should have 

responded similarly to sedimentation and flooding in 

the Mississippi alluvial valley. On the other hand, as 

discussed above, lakes may not have formed in the 

Loosahatchie and Wolf River valleys because they may 

have been too far from the locus of outwash deposition 

in the alluvial valley. 

The alternate interpretation, depicted by the terrace 

correlations shown in figure 8, alleviates these possible 

problems but presents others. The alternate interpretation differs from the preferred one primarily in 

the correlation of terraces along the Loosahatchie and 

Wolf Rivers. In the alternate interpretation, the higher 

terrace along these rivers (and along others to the 

south) is correlated with the Humboldt terrace rather 

than the Hatchie terrace, and the lower terrace along 

these rivers is correlated with the Hatchie terrace 

rather than the Finley terrace. What this alternate 

interpretation does is shift the need for an explanation 

of terrace absence from the Humboldt terrace to the 

Finley terrace, and a logical explanation is present. 

Figure 8 illustrates that, south of the Hatchie River, 

alluviation by the Mississippi River (within its present 

meander belt) and corresponding tributary-stream 

Holocene flood-plain aggradation have resulted in the 

lower terrace now being below present flood-plain 

level. Hence, the Finley terrace may be present but 

buried by Holocene alluvium. 

A significant unexplained aspect of this alternate 

interpretation is the conspicuous upward deflection in 

the Humboldt and Hatchie terrace profiles at the 

Hatchie River (fig. 8). For both terraces, the elevations 

at this river are 5 to 6 m higher than what they would 

be if a smoother downvalley profile were assumed, as 

it was in the preferred interpretation (fig. 7). 

Although a smoother profile would be the expected 

"normal" situation, an upward displacement near the 

Hatchie River is not without an explanation. It could 

be considered as evidence for continued or renewed 

structural uplift over an igneous intrusion (pluton) of 

Mesozoic age located beneath the Covington, Tenn., 

area (fig. 4). This and other plutons have been identified 

by gravity and magnetic surveys conducted as part of 

recent investigations of the origin and nature of the 

New Madrid seismic zone (Kane and others, 1981; 

Hildenbrand and others, 1977). They flank a northeasttrending graben or rift that is the locus of the appreciable seismic activity in the region. 

With the hypothesis of post-Mesozoic uplift in mind, 

we can discern apparently supporting evidence. For 

example, the course of the Hatchie River, which 

curves in a broad arc around the Covington area (fig. 

4), is suspicious, as is the asymmetrical location of the 

Holocene flood plain along the northern flank of the 

overall Quaternary valley (farthest from the pluton). 

Moreover, the profile of the Humboldt terrace along 

the Hatchie River (fig. 6) has a constant downvalley 

slope rather than the more characteristic and normal 

concave-upward slope. This slope could be interpreted 

as evidence for uplift along the lower part of the 

Hatchie River. 

Attention is now directed to the correlation of the 

terraces with events and features in the Mississippi 

alluvial valley. If the hypothesis is correct that extensive backwater flooding was a major factor in the 

formation of certain of the terraces, a close relationship 

should exist between farthest downstream terrace 

elevations and elevations of the braided-stream terraces 

in the St. Francis Basin area of the alluvial valley. 

Major periods of outwash deposition should have been 

coincident with times of maximum flood levels and 

also highest flood frequencies. Because of the relatively 

young geologic age of the braided-stream terraces and 

minimal postdepositional erosion or deposition, equivalency of elevation is considered to be a satisfactory 

basis for correlations. 

According to either terrace interpretation, farthest 

downstream elevations on the Finley terrace closely 

approximate the elevations of the highest (early 
LATE QUATERNARY TERRACES IN WESTERN TENNESSEE 17 

Wisconsinan Stage) braided-stream terrace (levels 1 

and 2 in figures 7 and 8). That the Finley terrace may 

be a meter or two higher is not considered significant 

and may reflect only the loess veneer known to be 

present. Thus, the Finley terrace probably correlates 

in time with the early Wisconsinan Stage outwash. 

If this correlation is valid, a late Wisconsinan Stage 

terrace should be present along the studied rivers as 

valley flooding and alluviation must have also accompanied this latest period of waning glaciation and 

outwash deposition. Such a terrace has not been 

recognized, but its apparent absence is not unexpected 

because, as can be seen in figures 7 and 8, the levels of 

the late Wisconsinan Stage outwash (levels 3 and 4) lie 

below the average elevations of natural levee crests of 

the present Mississippi River meander belt. As this 

meander belt dominates the alluvial valley landscape 

near or at the mouths of all the upland streams under 

consideration, the average flood-plain surface in the 

tributaries is at or above that of a possible late 

Wisconsinan Stage terrace. Hence, if it is present, it is 

likely buried by a thin veneer of Holocene alluvium. 

As mentioned in the section on terrace morphology, 

the Deweyville terrace is a widespread and distinctive 

physiographic feature on most streams in the Gulf of 

Mexico and Atlantic Coastal Plains. Few absolute 

dates are available to establish its chronological range, 

but evidence does indicate that it is definitely younger 

than mid-Wisconsinan (Farmdalian Substage) and 

older than Holocene (Saucier and Fleetwood, 1970; 

Saucier, 1974). More significantly, it formed during 

that part of the glacial-interglacial cycle in which the 

interaction of climate, landforms, and vegetation 

produced greatly increased stream discharges and 

sediment yields. This part of the cycle is believed to be 

coincident with waxing glaciation to near full glacial 

conditions and a time of widespread stream incision 

and valley degradation (Saucier, 1974; Grissinger and 

others, 1982). 

A Deweyville terrace is not recognized on the rivers 

in western Tennessee. Nevertheless, the scallops 

formed along the Holocene flood-plain margin of the 

Finley terrace subsequent to terrace formation are 

thought to be a product of the climatic conditions 

prevailing when the Deweyville terrace formed. The 

absence of a Deweyville terrace is not unusual in that it 

could have been destroyed by subsequent stream 

meandering or veneered by a thin layer of Holocene 

alluvium as it was in other stream valleys (Gagliano 

and Thom, 1967; Saucier and Fleetwood, 1970). 

If the terrace-margin scallops are the same age as 

the Deweyville terrace, they provide further evidence 

for the Finley terrace being pre-late Wisconsinan in 

age. Possibly the scallops and related features along 

the upland margin of the Finley terrace (which predate 

the terrace) are indicative of an unrecognized but not 

unexpected earlier episode of similar climatic response 

that occurred during waxing early Wisconsin glaciation. If these features did form then, they help substantiate that the Finley terrace formed during waning 

of the early Wisconsin glaciation. 

Additional evidence for an early Wisconsinan Stage 

assignment of the Finley terrace occurs along Nonconnah Creek. Situated in the extreme southwest 

corner of Tennessee south of Memphis (figs. 1, 5), this 

small stream, having a watershed of less than 500 km2, 

was not included in this terrace mapping effort because 

of its smallness and disturbance due to urbanization 

and channelization. However, as described by Delcourt 

and others (1980), a well-documented and dated 

measured section and fossil locality is present in the 

bank of the creek about 16 km upstream from the 

Mississippi alluvial valley. The 2.5-m-thick deposit, 

representing a sedimentary sequence extending from 

the Altonian Substage through the Woodfordian Substage, is below the average level of the present creek 

flood plain. Extrapolation based on the Finley terrace 

profile in figure 7 indicates that this terrace at the 

fossil locality on Nonconnah Creek should be at or 

slightly below flood-plain level because of the amount 

of Holocene sedimentation in this area. Hence, there is 

excellent stratigraphic agreement between the Finley 

terrace and the recorded section. 

According to the latest published views on lower 

Mississippi Valley Quaternary stratigraphy (Saucier, 

1974), the next oldest (pre-Wisconsinan) and highest 

widespread interglacial-stage depositional unit is the 

Prairie terrace. Of Sangamonian age (Saucier, 1977), 

this terrace is areally significant in the valley south of 

the latitude of Memphis and shows evidence of a long 

period of regional stability in which thick sequences of 

meander-belt and backswamp deposits accumulated. 

Slow flood-plain aggradation must have persisted for 

thousands of years. No remnants of the Prairie terrace 

have been identified in the Mississippi alluvial valley 

north of Memphis. However, as mentioned above, 

small isolated areas of probable Prairie terrace survive 

in sheltered locations near the mouths of small creeks 

on Crowleys Ridge. In this area, they lie a few meters 

above the highest level of early Wisconsin outwash. 

I postulate herein that the Hatchie terrace is a 

stratigraphic equivalent of the Prairie terrace and 

hence Sangamonian in age. The nil gradients and 

large extent of this terrace are certainly compatible 

with a long period of flood-plain aggradation in the 

Mississippi alluvial valley. However, it is quite possible 

that the downstream parts of the terrace exhibiting 

the nil gradient are not actually of lacustrine-plain 
18 THE NEW MADRID, MISSOURI, EARTHQUAKE REGION 

origin as the downstream parts of the Finley terrace 

are. Prolonged flood-plain aggradation in the alluvial 

valley, acting as a slowly rising base level for a long 

period, could have produced a nil gradient in the 

tributaries. An absence of discernible shoreline 

features associated with the Hatchie terrace supports 

this view. 

If the Hatchie terrace correlates with the Prairie 

terrace, the Humboldt terrace could be the equivalent 

of the Montgomery terrace. The Montgomery terrace 

is the next highest and most widespread interglacialstage fluvial terrace of the lower Mississippi Valley 

region (Fisk, 1939). Although concern is growing 

about the precise mode of origin and age of this 

terrace, it is still believed to be assignable to the 

Yarmouthian Stage (Saucier, 1974). Northernmost 

remnants of the Montgomery terrace occur north of 

the Grand Prairie region in eastern Arkansas (fig. 1); 

however, these are too far from the streams in western 

Tennessee to permit correlation based on elevations. 

Fisk (1939) identified the Bentley and Williana 

terraces of the lower Mississippi Valley as major 

interglacial-stage depositional formations older than 

the Montgomery terrace. However, many workers in 

the area now seriously question the existence of these 

formations as Pleistocene depositional units (Saucier, 

1974) or at least find correlations and age assignments 

to be impossible on the basis of existing evidence. 

Consequently, because of this uncertainty, it is not 

advisable to make any interpretation of the age of the 

Henderson terrace. In fact, I think that the geomorphic 

evidence alone is not sufficient to indicate that it is a 

Quaternary depositional formation. 

OVERVIEW 

This paper is the first attempt to systematically 

delineate and differentiate the late Quaternary deposits 

of western Tennessee associated with the present 

major upland drainage. Sound geomorphic evidence 

exists for a series of depositional terraces that have 

regional continuity and significance, although field 

verification and analyses of subsurface data have riot 

been accomplished. Two interpretations of interstream 

correlations are presented, both of which indicate 

similar responses to external controls. 

The most significant control affecting terrace formation processes and patterns along the lowermost several 

tens of kilometers of the streams studied was the 

deposition of glacial outwash in the Mississippi alluvial 

valley, which resulted in base-level changes. Understanding the direct and indirect responses of streams 

such as these to events in the alluvial valley is extremely 

important in refining interpretations of events within 

the alluvial valley itself. Because the alluvial valley 

has been an exceptionally dynamic environment 

characterized by repeated episodes of widespread 

scour and fill, major gaps must exist in the sedimentary 

record. Hence, one must look elsewhere for chronostratigraphic evidence. Detailed investigations of 

tributaries to the alluvial valley probably will contribute valuable information because the responses of 

the tributaries to scour and fill, although comparable 

in character to responses of the alluvial valley, probably 

were not of similar magnitude or duration. 

Geologists have long recognized that the upper part 

of the Mississippi alluvial valley is an area of active 

Quaternary tectonism and seismicity (Fuller, 1912). 

However, almost all past geological studies of the area 

have focused on glacial- and interglacial-stage stratigraphy and chronology, depositional processes, and 

landform evolution and have contributed little to a 

needed understanding of earthquake causes and 

patterns (McKeown, 1982). Only within the last decade 

have significant and definitive contributions been 

made to knowledge of the origin, patterns, and rates of 

localized deformation involving faulting, upwarping, 

and tilting of Pleistocene and Holocene deposits in the 

New Madrid region (Russ, 1982). Nevertheless, the 

relationship of this deformation to regional Pleistocene 

uplift in terms of processes and timing is not well 

understood. Compounding the problem is the strikingly 

low rate of tectonic deformation as compared to rates 

in other regions (McKeown, 1982). 

Information presented in this paper contributes in 

two respects toward an enhanced understanding of the 

regional aspects of Quaternary tectonism. First, it 

calls attention to a means of stratigraphic correlation 

that, in western Tennessee, has extended the range of 

possible indicators of regional deformation across a 

major physiographic boundary and well beyond the 

limits of the alluvial valley. Neither of the interpretations of terrace correlations indicates detectable 

Quaternary deformation in the upland area relative to 

the alluvial valley in the area studied. Similar terrace 

investigations and correlations need to be conducted 

elsewhere in the several-State area adjacent to the 

alluvial valley surrounding the New Madrid region...._ 

Second, the information in this paper is relevant to 

detecting possible Quaternary deformation within the 

upland area itself. Detecting such deformation is 

important because of the presence of several plutons in 

the New Madrid region (McKeown, 1982), at least one 

of which has been studied in detail and found to have 

experienced active uplift at least as recent as the end of 

the Paleocene (Glick, 1982). The alternate interpretation of terrace correlations presented in this paper is 

suggestive of progressive uplift in the upland area in 
LATE QUATERNARY TERRACES IN WESTERN TENNESSEE 19 

the vicinity of the Covington pluton; however, the 

preferred interpretation does not suggest uplift. 

Although I conclude, like Russ (1982), that the present 

upland physiography is primarily the result of normal 

erosional processes and not tectonism, further terrace 

investigations are necessary to arrive at a single viable 

interpretation, which may or may not suggest 

Quaternary deformation. Similar investigations in the 

vicinity of other plutons are necessary to better define 

their role in regional tectonism. 

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US GOVERNMENT PRINTING OFFICE 1987 - 201-933 - 226/60060 

Saucier—GEOMORPHOLOGICAL INTERPRETATIONS OF LATE QUATERNARY TERRACES IN WESTERN TENNESSEE—U.S. Geological Survey 

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