38 BRI Bulletin

De Quincy Fault-Line Scarp, Beauregard and Calcasieu Parishes, Louisiana

Paul V. Heinrich 1

Abstract The De Quincy scarp is a 25-foot (8-m)-high and

25-mile ( 40-km)-long east-west trending scarp, which forms a prominent landform within southern Beauregard and northern Calcasieu parishes (T7S­R1 0-11 W). Although long recognized by geologists, the significance of this prominent scarp has remained unresolved. The analysis of evidence gathered from geologic mapping, topographic maps, soils surveys, shallow soil borings, and geophysical logs of oil and water wells demonstrate that the De Quincy scarp is a fault-line scarp associated with a regional east-west trending fault.

Two distinct periods of movement have occurred along this fault. The period of initial movement was contemporaneous with the deposition and growth faulting of the Upper Eocene strata. The fault was inactive for the Oligocene, all of the Miocene, and most of the Pliocene. During the Late Pliocene or Early Pleistocene, the fault became active again, and about 300ft (90 m) of vertical separation occurred. The amount of vertical separation increases with depth.

1Louisiana Geological Survey, Louisiana State University, Baton Rouge, Louisiana 70803

Introduction The De Quincy scarp is a prominent east-west,

coast-parallel scarp that lies within northern Calcasieu Parish and southern Beauregard Parish. Within the vicinity of the city of De Quincy, the De Quincy scarp has a relief of about 25ft (8 m) and a width of about 60 to 100ft (18 to 30m). This scarp has a total length of about 25 miles ( 40 km). In ad­dition, the De Quincy, East Perkins and Perkins oil fields, all of which parallel this scarp, lie 0. 7 to 0.9 mile (1.1 to 1.4 km) south of it (Heinrich, 1988; U.S. Geological Survey, 1956a, b, c). The De Quincy scarp is one of several recently mapped linear coast-paral­lel scarps within southwest Louisiana (Fig. 1).

The purpose of this study was to determine the origin of this well-defined scarp. Fisk (1939 and 1948) uses the De Quincy scarp as a major deposi­tional terrace scarp between his Montgomery and Bentley terraces. However, later mapping by Snead and McCulloh (1984) and Kesel (1987) shows that the depositional terrace boundary between their In­termediate and Prairie Complex consists of a lower and much more irregular scarp. This scarp lies 4 to 6 miles ( 6 to 10 km) south of the De Quincy scarp. As a result, Fisk's very prominent and regional bounding scarp lies within the Intermediate Com­plex and thus its origin remains unexplained (Aronow, 1986; Birdseye and Aronow, 1988). This study investigated the origin of this scarp because the regional extent and relief exhibited indicates a landform that represents a significant aspect of the geomorphology of southwest Louisiana.

An initial review of the existing literature con­cerning the regional geology of the De Quincy area and the Louisiana Coastal Plain resulted in a work­ing hypothesis that the De Quincy scarp is a fault­line scarp. Within East Baton Rouge Parish, Durham and Peeples (1956), Durham (1964), and Winz et al. (1970) and McCulloh (1996) demonstrate that scarps of identical morphology and similar relief are the surface expression of onshore, listric faults. In addi-

BRI Bulletin 39

tion, the De Quincy scarp is straighter, higher, and more distinct than the complexly embayed, 3 to 12 ft ( 1 to 4 m) high, and indistinct depositional scarp that separates the Prairie and Intermediate complexes (Birdseye and Aronow, 1988; Heinrich, 1988).

Also, structural rna ps of the De Quincy, East Perkins and Perkins oil fields by Autin (1952) and Holland et al. (1952) illustrate the presence of are­gional fault that precisely parallels the De Quincy scarp (Fig. 2). Tectonics associated with this fault created rollover structures containing the De Quincy, East Perkins, and Perkins oil fields, which lie along its downthrown side. The subsurface trace of this fault, at a depth of about 5100 ft (1550 m) below sea level, lies about 0.5 mile ( 800 m) gulfward of the scarp (Autin 1952). At this position, the fault would have an average dip of about 59° in order to crop

out as the scarp. This dip lies well within the 59° 30' to 64° 0' range of dips and 61 o 20' average dip cal­culated by Autin (1952) from well logs for subsur­face portions of this fault.

Furthermore, the presence of fault-line scarps in adjacent portions of southeast Texas and theoretical considerations suggest that fault-line scarps should occur within southwest Louisiana despite the lack of mapped fault-line scarps. Within nearby Jasper County, Texas, between Buna and Kirbyville, Ber­nard (1950) illustrates well-defined fault-line scarps (Fig. 1). Nunn (1985) concludes that the same tec­tonic forces that produced fault-line scarps in the Florida Parishes of Louisiana and Jasper County, Texas, also affected southwest Louisiana. Although Snead and McCulloh (1984) illustrate a lack of faults within southwest Louisiana, the presence of fault-

94° 93° 92° 31°~--~----------~--------------------~----~--~~ ~~~~~----~------~ 31 °

Jasper >j Vernon

Newton ~ u '- -? r -o De Ridder

... Kirbyville

[ '

Orange

Orange

I • { • Merryville

J j { Beauregard ~t'ff

u - o·

r~~ "'--o , \ "'

"' Calcasieu

Sulphur t'

~-~--T T'' D

~-------· -·· D _.2- _\} ...

Re"ees D ' D

Lake Charles

...<---·~ D D

Oakdale •

Allen

. J.!- ----~--.. ~Oberlin

15"

Evangeline

u ___ _....,....._ D

Acadia

Crowley •

30 ° ~------L---------C~a~m~e~r~o~n __________ ~------------L-------------------~ 30• 94° 93° 92"

Key ____ ...

Dashed Where Probable

__ u_ Fault-Line Scarp D

T + T Fault Trace

Town or City

Miles 10 15 20 25

10 15

Kilometers

Figure 1- Map of fault-line scarps and traces in the Lake Charles 1:250,000 quadrangle (Texas data from Bernard, 1950).

40

+

1

~City or town

Alluvial fan

B • Cu-1038

• 64495

0

BRI Bulletin

Beauregard Parish Calcasieu Parish

De Quincy

42185

a= 40132 b 40347 & SWDW #1 c 40766

A

\. 71035

d = 90828 e = 72980 f= Cu-790

• 69619

1 2 3 4 Miles

1 0 1 2 3 4 5 Kilometers Kffi~ll===~====E===3===~===3

LEGEND ---Structural contour A A' Cross section -·-·-·-·-· Fault in subsurface • 42185 Oil or water well

-------Scarp

f:::<::<::<::-::1 Ponded flood plain ---------- Prominent saddle across interfluve

Figure 2-Relationship of subsurface structure to surface features in the De Quincy area. Structural contours and faults from Holland et al. ( 1952). Contour interval= 10ft.

BRI Bulletin 41

line scarps within that region would be consistent with the observations of Bernard (1950) and con­clusions of Nunn (1985). Therefore, it was hypoth­esized that the De Quincy scarp is a fault-line scarp.

The testing of this hypothesis demonstrates that a clear association exists between the De Quincy scarp and a major growth fault associated with rollover structures. Cross sections compiled from subsurface data showed that the fault associated with the nearby De Quincy, East Perkins, and Perkins oil fields could be traced up the base of the De Quincy scarp. Analysis of subsurface data together with the geomorphology of the study area clearly demon­strated that the De Quincy scarp is a fault-line scarp. This fault-line scarp exhibited a growth history simi­lar to that of the Baton Rouge fault within East Ba­ton Rouge Parish and the Tepetate fault zone within Pointe Coupee Parish (Durham and Peeples, 1956; Hanor, 1982). If the De Quincy scarp is a fault-line scarp, then other such scarps mapped within south­west Louisiana are likely fault-line scarps (Fig. 1).

Methodology The hypothesis that the De Quincy scarp is a

fault-line scarp was tested by using a study area con­sisting of 60 square miles, which straddles the bor­der between Calcasieu and Beauregard parishes near and including the city of De Quincy (Fig. 3). This study area consisted of parts of township T. 7 S., R. 11 W., T. 7 S., R 10 W., T. 8 S., R. 11 W. and T. 8 S., R 10 W. This area was chosen because of the avail­ability of different types of subsurface data, e.g., well logs of oil, water, and disposal wells; surface data, e.g., aerial photography and soils survey; and the presence of a well-defined segment of the De Quincy scarp.

The preexisting subsurface data consisted of elec­tric logs of water wells, saltwater disposal wells, and oil wells, and biostratigraphic data from the latter. The electric logs of water wells came from wells drilled by the city of De Quincy for municipal water supply (Appendix 1). They were found in the files of the U.S. Geological Survey in Baton Rouge, Louisi­ana. The electric logs of oil wells came from wildcat wells scattered about the study area and production wells associated with the De Quincy, East Perkins, and Perkins oil fields (Appendix 1). These well logs were found in the Log Files section in the Oil and Gas Division, Office of Conservation, Louisiana Department of Natural Resources. Biostratigraphic

data from various sources locating the top of the Heterostegina datum, Marginulina idomorpha da­tum, and Frio Formation were incorporated into elec­tric log correlations. This data was used to construct detailed north-south cross sections extending across the De Quincy scarp and several kilometers to the south (Fig. 2). Because of the overlapping well logs from oil wells and water and salt-water disposal wells, it was possible to construct cross sections from the surface down to depths of 5500 to 6400 ft (1800 to 2100 m) below sea level.

As part of geologic mapping done for the Snead et al (1997), a series of ten shallow holes were drilled as part of two transects crossing the De Quincy scarp (Fig. 2). Each transect consisted of five holes drilled as to straddle the scarp. The holes were cored with a Giddings Soil probe until either refusal or caving of the hole made additional coring impossible. The re­covered cores were described in the field.

This study used various types of surface data. The surface data consisted of the soil survey of Calcasieu Parish (Roy and Midkiff, 1988), 1:20,000-scale Agricultural Stabilization and Conservation Service aerial photography of Calcasieu and Beauregard parishes, dating from 1940 to 1953, field observations, and 7.5-minute U. S. Geological Sur­vey topographic maps made for this area. From this data, geomorphic surfaces, lineations, and relict and modern landforms were mapped on the 1:24,000-scale, 7.5-minute U.S. Geological Survey topographic maps.

Results Interpretation of the surficial and subsurface ge­

ology of the De Quincy scarp revealed evidence dem­onstrating that the De Quincy scarp is a fault-line scarp. Interpretation of subsurface data showed that the fault associated with the De Quincy, Perkins, and West Perkins oil fields extend up to the base of the De Quincy scarp. The surface of the project area exhibits geomorphic features, in addition to the scarp, which are commonly associated with faulting and indicate subsidence along the downthrown side of the scarp.

Subsurface Cross sections made from subsurface data show

that the fault associated with rollover structures con­taining the De Quincy, Perkins, and West Perkins oil fields extends to the base of the De Quincy scarp.

42 BRI Bulletin

First, the cross sections confirmed that a major, re­gional normal fault very closely parallels the De Quincy scarp as indicated by previous studies, e.g., Autin (1952) and Holland et al. (1952). Second, the cut points determined from the geophysical logs of water, oil, and gas wells within the study area define the depth and separation of the fault between 2440 to 6960 ft (700 to 2000 m) below sea level (Figs. 4 and 5). The cross sections clearly showed that the dip of this fault projects its plane to the base of the

___ B_:a_ur~g~~~a.:_isil __ _ Calcasieu Parish

De Quincy scarp. Finally, the changes in the eleva­tion of stratigraphic units across the projected up­ward plane of the fault clearly indicate that faulting along it has offset strata between 210 to 2440 ft ( 60 to 700 m) below sea level. Within this interval the relative separation is approximately 300 ft (90 m) (Fig. 6).

Above 700ft (200m) below sea level, the analy­sis of the subsurface data demonstrated that the amount of separation increases with depth (Fig. 6).

8::::a:=;ca:::lo~=========3======2E=::====:=====i'::=====i4 Miles

B::e:a:a::a:io====:====i===2i====~==='4=======35 Kilometers

LEGEND

Holocene Deposits ~ Unnamed alluvial deposits

Unnamed alluvium fan deposits

Pleistocene Deposits

~ Deweyville allogroup

D Prairie Allogroup, Beaumont Formation

Cultural Features

18881 City or town

--Highway ---- Parish boundary • n9so Oil or water well a LC4 Shallow boring

Structural Feature

D Intermediate Allogroup, Lissie Formation --J-- Fault-line scarp

Figure 3-Geologic sketch map of the De Quincy area covering both the De Quincy and Gordon 7.5-minute quadrangles.

BRI Bulletin

A North

(1 --...} = Ut -...} 0\ I ........ Ut N -...} 0 - 0 N ..j:::.

69619 w Ut De Quincy Ut 0\ 0\ Ut w N 0\ 0

+ + + Scarp + + +

I

Shdl

TD 10046 TD 10510 y 0 1 000 2000 3000 feet TD 7115

0 500 1 000 meters EcE3::B:::S::E3:::E~====~3 TD 7010

LEGEND Sand

Shale

\0 0 00 N 00

+

-...} N \0 00 0 +

m- 25~~ !!l. 500~

750

A' South

Cu-790 +

-1000 ft

----2000

1 ~00~ 200~ en

300

-4000

~~-5000

-6000

Vertical Exaggeration 20X

Het. =Top of Heterostegina texana Frio= Top of Frio Formation N = N Sand of Autin (1952)

Sa, Sb, Sc, Sd = Sandstone marker beds; Sh = Shale marker beds

Figure 4-Cross section A -A' across De Quincy scarp.

43

44 BRI Bulletin

(1 B De Quincy

0 ......... 0 00 l;..) 00 0\ .j:::.. 00 lll 0\ 00

B' .j:::.. ~.j:::.. South 0 ::lO ......... P,..l;..l l;..)

r.j:::.. 40766 N

!. North t!3 e;/Scarp ::5

+-O~i ~ = --=--~ = ~:~-= = =-~ = ~ r .. ~-:-:-~':"""+-:"""""-,-,-~~~~.........,..-+--:-..--.-,._,..,._,........,._I 00-..l

+ l;..)+ +

6000 ft omitted

~-1000 ft

16' 25~~ !2. 500~

750

·--4000 ft

-5000 ft

~'-6000 ft

0

100 3 CD

200~ (/)

300

0 1 000 2000 3000 feet

0 500 1 000 meters

D Sand

Shale

Vertical Exaggeration 20X

LEGEND

Het. =Top of Heterostegina texana Frio= Top of Frio Formation N = N Sand of Autin (1952)

Sa, Sb, Sc, Sd = Sandstone marker beds; Sh = Shale marker beds

Figure 5-Cross section B-B' across De Quincy scarp.

BRI Bulletin 45

For example, the base of the Alta Lorna Sand is off­set by 94ft (27m) at its base and by 42ft (12m) at its top. Sedimentation clearly was contemporaneous with faulting within this interval. This upward de-

-.surface of Intermediate Allogroup -..... _ Top of 500 - ._!3ase of 500-foot sand

-foot sand -- _ ------- 1•• Sb15 I I

• I Sci• 1

I I • Shdl • • , I

Top Heterosteginae : Top Frio• I

I I I eTop N Sand I I I

Figure 6-Plot of separation versus depth for marker beds in Cross Section A -A'.

crease in separation is consistent with the 24ft ( 8 m) of offset exhibited by the De Quincy scarp.

Analysis of subsurface data from the shallow Giddings holes provided evidence of offset across the scarp within Pleistocene alluvial strata underlying the Intermediate Complex. In the borings, about 7 m (20 ft) of light grayish-brown to light gray clay silt, silty clay, and clay lies on top of a red to strong brown clayey silts and clays (Figs. 7 and 8). In one boring, about 9ft (3m) of loose, wet, silty sand was present at the base of the upper unit. In cross section C-C', the offset of the contact between the two units ap­pears to be about 40 ft ( 12 m) across the fault-line scarp (Fig. 7). In cross section D-D', the offset is about 30ft (9 m) across the fault-line scarp (Fig. 8).

Surface Geomorphic features within the study area also

indicate a fault-line scarp. The De Quincy scarp ex­hibits distinctive tonal and topographic lineaments that are often associated with faulting. The topo-

graphic lineament not only includes the scarp itself, but also saddles that cross the crest of interfluves and ridges where they join the scarp. Finally, the scarp offsets the surface of the Intermediate Complex by 24ft (8 m) (Figs. 3, 4, and 5).

Evidence of subsidence along the edge of the De Quincy scarp is present within the study area. On the Prairie Complex, an ancient channel of Beckwith Creek abruptly turns 90° and flows westward along the base of the scarp before turning 90° to again re­sume a southward course. Holocene subsidence is indicated by the presence of a large swamp that ter­minates within the flood plain of Cowards Gully, where it crosses the projected fault trace. The abrupt change in channel course and termination of swamp may reflect the effects of subsidence along the edge of the fault. Subsidence adjacent to a fault-line scarp is commonly associated with active Gulf Coast nor­mal faults. The subsidence results from either the formation of a small half graben or other types of deformation as a result of active fault movement (Van Siclen, 1981).

Discussion Analysis of the above data demonstrated that the

De Quincy scarp is a fault-line scarp. This suggests that similar scarps mapped within southwestern Louisiana and other parts of the Gulf Coastal Plains are also fault-line scarps. The presence of fault-line scarps within southwestern Louisiana support and contradict current models of neotectonics. Finally, these fault-line scarps demonstrate the likely pres­ence of a here-to-fore unrecognized form of geologi­cal hazard within this region.

Other Scarps Within southwest Louisiana, other similar scarps

have been mapped (Fig. 1). Many of these scarps are considered fault-line scarps because they exhibit many of the characteristics of the De Quincy scarp. The China and Reeves scarps exhibit these charac­teristics.

For example, the China scarp, which is named for the China Cemetery within Sec. 19, T. 7 S., R. 5 W., clearly represents a fault-line scarp (U.S. Geo­logical Survey, 1960). The China scarp consists of a 13-mile (21-km) scarp having a relief of 6 to 10ft (2 to 3 m) and a width of 400 to 800 ft ( 122 m to 243 m). It starts within Sec. 22, T. 7 S., R. 5 W. and ex­tends to Sec. 22, T. 7 S., R. 4 W., Jefferson Davis Parish, Louisiana (Fig. 1). Two additional scarp frag-

46 BRI Bulletin

ments occur 5 miles ( 8 km) farther east within Acadia Parish. The China scarp lies on the north, upthrown side and parallel to a regional fault called the Seven­South fault zone by Paine (1962). This scarp has truncated the valley wall of an ancient Red River channel, vertically displaced the same relict chan­nel, and caused a short east-west deflection in an associated relict river course segment. Holocene n1ovement of the fault associated with this scarp is indicated by the presence of swamp within the flood plain of Serpent Bayou, immediately downstream of where the fault trace is projected to cross it.

About 7 miles ( 11 km) west of the west end of the China scarp along the strike of the Seven-South fault zone, Paine (1962) illustrates a fault within flu­vial deposits of the Prairie Allogroup. This fault was exposed within the sides of the Wolfe gravel pits within Sec. 29, T. 7 S., R. 6 W. The fault dies out before it reaches the surface of the Prairie Allogroup.

c North

0· 1.0

LCl +

The exposed fault lies about 4000 ft ( 1220 m) north of the Hawkins and Cummings, King Corp. No. 2 well, which cuts the Seven-South fault zone at a depth of 64 77ft (1974 m) (Paine 1962). Thus, the dip re­quired for the surface faulting to be connected with the Seven-South fault zone would be 52°, which is low, but still possible, for a Gulf Coast growth fault.

Louisiana Coastal Neotectonics

Nunn (1985) and Lopez (1991) propose two con­tradictory models concerning how the Louisiana coastal plain and continental shelf are reacting to stress generated by the sedimentary load imposed on them during the last 2 million years. According to Nunn (1985), this tension results from extremely high sedimentation rates, about 4.7 to 7.1 in (12 to 18 em) per 100 years, since the start of the Pleis­tocene Epoch. This high rate of sedimentation cre­ated a zone of horizontal extension within the un­derlying crust, which resulted in the reactivation of

LC2 +

LC3 +

2.0

LC4 LC5 + +

2.4

C'

South

Distance (miles) LEGEND I < I Holocene alluvium and Prairie Allogroup c=J Unnamed pedisediment ~§ Upper unnamed alluvium, Intermediate Allogroup ...___......__..... Lower unnamed alluvium, Intermediate Allogroup

Figure 7-Surficial cross section C-C' across De Quincy scarp.

\ f Fault

\ LC4

+

1 Boring

BRI Bulletin 47

Tertiary growth faults within overlying Tertiary sedi­ments. Nunn (1985) indicates that the current state of stress within the coastal plain is uniformly ten­sional across the entire Louisiana coastal plain. Thus, this model predicts that evidence for the reactiva­tion of Late Tertiary faults should be found across the entire Louisiana coastal plain along the proposed hinge line, rather than just in the Florida Parishes alone.

In contrast, Lopez (1991) proposes that the cur­rent subsidence is restricted to a wedge-shaped sec­tion of the Louisiana Coastal Plain and continental shelf. This section is bounded to the north by the Comachean Shelf Edge and to the east by :a gener­ally north to south trending hinge line. Within the Florida Parishes, the Denham Springs Baton Rouge fault zone lies south of the Comachean Shelf Edge.

D

North

100

LC6 +

Vertical Exaggeration = 40X -50

0 1.0

The subsidence presumably results from the loading of the continental margin, starting in the Miocene Epoch and continued into modern times (Lopez, 1991). The hinge line, which forms the western edge of the subsiding block, lies along the western valley wall of the Mississippi Alluvial Valley or within the Atchafalaya Basin (Lopez, 1991, personal commu­nications 1992).

The confirmation of the De Quincy scarp as be­ing a fault-line scarp and the presence of similar scarps within southwestern Louisiana strongly sup­ports the model ofNunn (1985) and contradicts the model of Lopez (1991). The presence of identified and potential fault-line scarps within southwestern Louisiana clearly supports the conclusion of Nunn (1985) that a belt along the entire Louisiana Coastal Plain is being subjected to tensional stress that has

LC7 LC8 + +

f

2.0

LC9 +

D'

South LClO +

30 ,..-.., 00 1-< il)

-+-' il)

s '-'

a:> >

15 ~ ~ il)

C/)

il)

> 0

~ 0 ~

.9 ~ > il)

~

-15

2.6

Distance (miles)

LEGEND 1:: >: : :1 Holocene alluvium and Prairie Allogroup 1· I Unnamed pedisediment t=::=::=::=::=::==~==~ Upper unnamed alluvium, Intermediate Allogroup I~~"@ Lower unnamed alluvium, Intermediate Allogroup

Figure 8-Surficial cross section D-D' across De Quincy scarp.

\ f Fault

\

LC4 + 1 Boring

48 BRI Bulletin

reactivated older Tertiary growth faults during the Pleistocene. In contrast, the observed distribution of these scarps contradict the model of Lopez (1991), which has the tensional stress and the faulting along the Tepetate and other growth fault zones terminat­ing at his north to south trending hingeline, either along the western edge of or within the Mississippi Alluvial Valley. Finally, the timing and magnitude of both the Baton Rouge fault and the fault associated with the De Quincy scarp are similar enough to in­dicate that they have a common history of move­ment. The similarity in the history of movement along both faults would not exist if subsidence of the Loui­siana shelf and coastal plain was limited to the area lying east of Lopez's (1991) hypothetical hingeline.

Geologic Hazards

Despite the lack of seismicity on the fault associ­ated within the De Quincy scarp, this and the other faults associated with scarps within southwest Loui­siana constitute a potential geological hazard to struc­tures, pipelines, and roads crossing the traces of these scarps. Movement along these faults could inflict sig­nificant damage to structures straddling their traces. Any such movements would tilt and deform, and ultimately break and pull apart the foundations and superstructures of houses, pavement of roads and highways, and water and sewer lines built across them (Roland et al., 1981). Movement along faults also results in subsidiary faulting on both the downthrown and upthrown sides of a fault and sub­sidence adjacent to the fault trace on its downthrown side. This subsidiary faulting and subsidence can extend the zone of structural damage associated with a fault as much as 20 to 100ft (6 to 30m) on either side of its trace (Verbeek and Clanton, 1981; McCulloh, 1991 ).

Further Research

At this ti1ne, additional research ren1ains to be done concerning the De Quincy and other scarps within southwest Louisiana. In case of the De Quincy scarp, the precise position of the fault trace relative to the De Quincy scarp remains uncertain. Similarly, the precise location of other fault traces relative to their associated scarps within southwestern Louisi­ana are undetermined. In addition, the identification of other southwest Louisiana scarps as fault-line scarps remains to be clearly demonstrated. Finally, the history of faulting is known only for the fault associated with the De Quincy scarp.

Acknowledgments I thank John Anderson of the National Carto­

graphic Information Center, Department of Geogra­phy and Anthropology, Louisiana State University (LSU), and Joyce Nelson, formerly of the same, for access to their aerial photocopy and map collections that made this research possible. I also thank the staff of the Well Log Files of the Louisiana Depart­ment of Natural Resources (DNR) for their help and cooperation. Finally, I thank Whitney Autin of the State University of New York at Brockton, Bill Marsalis of the DNR Office of Mineral Resources, and Richard McCulloh of the Louisiana Geological Survey, LSU, and Dr. Michael Simms for their en­couragement and comments.

Engineering Research Associates of Baytown, Texas, provided grants and logistical support for the research conducted prior to my employment with the Louisiana Geological Survey. In addition, sub­surface investigations of the De Quincy fault-line scarp was supported by the U.S. Geological Survey, Department of Interiot; under Assistance Award No. 1434-HQ-96-AG01490, as part of research con­ducted for Snead et al. (1997).

References Aronow, S., 1986, Surface Geology of Calcasieu

Parish: report on file with the USDA, Soil Conservation Service, Lake Charles, Louisiana, field office, 19 p.

Autin, L.J., 1952, Subsurface Study of De Quincy and Perkins Fields, Calcasieu Parish, Louisiana: unpublished master's thesis, Department of Geology, Louisiana State University, Baton Rouge, 33 p.

Bernard, H.A. 1950. Quaternary Geology of Southeast Texas: unpublished Ph.D. disserta­tion, Department of Geology, Louisiana State University, Baton Rouge, 165 p.

Birdseye, R.U., and Aronow, S., 1988, Possible faulting south of De Quincy, in Late Quaternary Geology of Southwestern Louisiana and South­eastern Texas, Part 1, South-Central Friends of The Pleistocene Sixth Field Conference, March 25-27, 1988: Lamar University, Beaumont, Texas, p. 50-51.

Durham, C.O., 1964, Flood plain and terrace geomorphology, Baton Rouge fault zone, in Guidebooks for Field Trips, Southeastern Section, Geological Society of America, 1964

BRI Bulletin 49

Annual Meeting, Baton Rouge, Louisiana, April 9-12, 1964: Geological Society of America, p. 38-54.

Durham, C.O., and Peeples, E.M. III, 1956, Pleistocene fault zone in southeastern Louisiana: Gulf Coast Association of Geological Societies Transactions, v. 6, p. 65-66.

Fisk, H.N., 1939, Depositional terrace slopes in Louisiana: Journal of Geography, v. 2, p. 181-200.

Fisk, H.N., 1948, Geological investigation of the Lower Mermentau River Basin and adjacent areas in coastal Louisiana: Mississippi River Commission, Vicksburg, Mississippi, 40 p.

Hanor, J.S., 1982, Reactivation of fault move­ments, Tepetate fault zone, south central Louisi­ana: Gulf Coast Association of Geological Societies Transactions, v. 32, p. 237-245.

Heinrich, P.V., 1988, Tectonic origin of Montgom­ery Terrace scarp of southwestern Louisiana: Gulf Coast Association of Geological Societies Transactions, v. 38, p. 582.

Holland, W.C., Leo, W.H., and Grover, E.M., 1952, Geology of Beauregard and Allen Par­ishes: Louisiana Department of Conservation, Geological Bulletin No. 27, 224 p.

Kesel, R.H., 1987, Quaternary depositional surfaces of western Louisiana: Louisiana Geological Survey, Open-File Series No. 87-02, 16 p.

Lopez, ].A., 1991. Origin of Lake Pontchartrain and the 1987 Irish Bayou Earthquake, in Coastal Depositional Systems in the Gulf of Mexico, Twelfth Annual Research Conference, Gulf Coast Section, Society of Economic Paleon­tologists and Mineralogists Foundation, Decem­ber 1991, Houston, Texas, p. 103-110.

McCulloh, R.P., 1996, Topographic criteria bear­ing on the interpreted placement of the traces of faults of the Baton Rouge system in relation to their fault-line scarps: Louisiana Geological Survey, Open-File Series 96-01, 13 p.

Nunn, ].A., 1985, State of stress in the northern Gulf Coast: Geology. v. 13, p. 429-432.

Paine, W.R., 1962, Geology of Acadia and Jefferson Davis Parishes: Louisiana Department of Conservation, Geological Bulletin No. 36, 277 p.

Roland, H.L., Hill, T.F., Autin, P., Durham, C.O., and Smith, C.G. 1981. The Baton Rouge and

Denham Springs Scotlandville faults: mapping and damage assessment: Report prepared for the Louisiana Department of Natural Resources, contract no. 21576-80-01. Louisiana Geological Survey and Durham Geological Associates Consultants, Baton Rouge, Louisiana. 26 p. plus maps. Scale: 1 in.=400 ft.

Roy, A.]., and Midkiff, C.T., 1988, Soil Survey of Calcasieu Parish, Louisiana: U.S. Dept. of Agriculture, Soil Conservation Service, Washing­ton D.C., 161 p.

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Appendix A -Well logs Used in Cross Sections

Cross Section A Well No. Well Name Company Top Log TD (ft)

69619 Edgewood Land Shell Oil Co. 120 10704 & Logging B-1

71035 Edgewood Land Beck Oil Co. 1805 10513 & Logging #1

CU-1163 Calcasieu Parish Calcasieu Parish 20 808 Water Works District #7, Test Well #1

155052 Owens-Illinois #1 M. R. Johnson 1049 7128

172266 Owens-Illinois # Delta Energy 800 6997

167460 Owens-Illinois #1 Lea Exploration 1019 7119

90828 Edgewood Land General American 832 6138 & Logging #21 Oil Company

72980 Edgewood Land Temple Hargrove 394 7192 & Logging #1 & Cypress Oil Co.

Cu-790 Well No. Cu-790 U. S. Geol. Survey 42 424

Cross Section B Well No. Well Name Company Top Log TD

Cu-1038 De Quincy Industrial Calcasieu Parish 20 762 Air Park Well #1

42185 Lutcher-Moore D-1 Niloco Co. 1019 7002

45066 Lutcher-Moore C-1 Niloco Co. 521 6402

87848 Industrial Lumber #1 F. E. Jameson 820 7052

40132 A. C. McPatter #B-1 Niloco Co. 833 7370

40347 Sun Fee #1 Sun Oil Company 2004 6900

L-83 Saltwater Disposal Sun Oil Company 90 3340 Well #1

40766 Sun Fee #1 Sun Oil Company 2020 6750