Cotton Valley (Upper Jurassic)And Hosston(Lower Cretaceous) Depositional Systemsand Their Influence Onsalt Tectonics Intheeast Texasbasin by Mary K

Cotton Valley (Upper Jurassic)and Hosston(Lower Cretaceous) Depositional Systemsand Their Influence onSalt Tectonics intheEast TexasBasin By Mary K. McGowen and David W. Harris

Reprintedfrom The Jurassic of the Gulf Rim: Proceedingsofthe ThirdAnnualResearch Conference, Gulf Coast Section, Society of Economic Paleontologists and Mineralogists Foundation,1984

1984 BUREAUOFECONOMIC GEOLOGY W. L.Fisher, Director The University of Texas at Austin Austin, Texas 78713 Geological Circular 84-5 Cotton Valley (Upper Jurassic)and Hosston(Lower Cretaceous) Depositional Systemsand Their Influence onSalt Tectonics intheEast TexasBasin By Mary K. McGowen and David W. Harris

Assisted by Cynthia Lopez andKeith Pollman

Reprintedfrom The Jurassicof the GulfRim,edited by WilliamP.S. Ventress,Don G.Bebout,Bob F.Perkins,and Clyde H.Moore:Proceedingsof the ThirdAnnualResearchConference, GulfCoast Section,SocietyofEconomic Paleontologists and Mineralogists Foundation,1984

Fundingprovided by the U.S. Department of Energyunder Contract No. DE-AC97-80ET46617

1984 BUREAUOFECONOMIC GEOLOGY W. L.Fisher,Director The University of Texas at Austin Austin, Texas 78713 Cotton Valley (Upper Jurassic)and Hosston (Lower Cretaceous) Depositional Systemsand

Theirin theInfluenceEast TexasonBasinSalt Tectonics Mary K.McGowen ARCO Oil and Gas Company P.O. Box 2819 Dallas, Texas 75221 David W. Harris Marathon Oil Company P.O. Box 2659 Casper, Wyoming 82602

Abstract mature drainage system had not yet formed. The Cotton Valley Group, which is Correct interpretation of the effect of basin thought to be a fan-delta system, can be sub- infilling on salt mobilization is critical to divided into three types of facies: prodelta understanding salt dome growth and stability. deposits, delta-front deposits, and braided The size of salt structures in the East Texas fluvial deposits. Fan deltas, supplied by Basin is determined by the original thick- braided streams, prograded from the north, ness of the underlying Louann Salt (Middle northwest, and west. Dip-oriented sandstone "Jurassic): that is, salt structures distinct- trends dominate in the northwestern part of ly increase in size toward the interior of the basin and change basinward to northeast the basin. Initial movement of salt appar- to southwest strike-oriented trends. ently occurred in the marginal areas of the During Hosston time, sedimentation in basin during Smackover (Late Jurassic) depo- the northwestern part of the basin was domi- sition. This movement seems to have resulted nantly fluvial. The depositional character- from downward creep that was induced by lead- istics of sediments in this area are typical ing of carbonate units and was enhanced oy of braided streams. In the study area, par- basinward tilting. allel net-sandstone and sediment thicks are During a major shift from carbonate to clearly defined in the distal part of the clastic sedimentation in the Late Jurassic, Cotton Valley but are not as well defined in salt movement became more extensive. This the Hosston. This suggests that ioost deltaic salt migration was caused by uneven sediment sedimentation during Hosston time occurred loading of fluvial-deltaic systems in the basinward of the study area. A major trans- Cotton Valley Group (Upper Jurassic) and the gression at the end of Hosston time resulted Hosston Formation (Lower Cretaceous). Terri- in deposition of the Pettet Limestone. genous source areas to the west and north Apparently, the location of salt domes persisted throughout Cotton Valley and Hoss- and salt anticlines was controlled by the po- ton time. elastics v/ere delivered to the sition of the Smackover-Giimer carbonate East Texas Basin by many small streams, platform. This platform impeded local subsi- rather than by one major stream, because a dence to the extent that fan-delta sediments

GCSSEPM Foundation Third Annual Research Conference Proceedings, March 1984 213 214 The Jurassic of the Gulf Rim

of the Cotton Valley Group spread laterally west and north into the basin (McGowen and across the shelf rather than stacked verti- Harris, 1981) and second, because deep-well- cally. Sediment depocenters formed prefer- control, seismic, and gravity data were entially basinward of the platform, resulting available. in migration of the underlying salt into Salt movement began at different times ridges that fronted the prograding sediment in different parts of the basin. The earli- wedge. As the salt was depleted under these est movement occurred around the margins of depocenters, subsidence slowed and thereby the basin during Smackover deposition (Jack- allowed the fan deltas to override the salt son and Harris, 1981). At that time, in- ridges. This resulted in a basinward progra- creased subsidence toward the center of the dation of deltaic depocenters and produced basin caused basinward tilting that, induced younger depocenters toward the interior of by downward creep, mobilized salt. the basin. Further salt migration and dif- More extensive salt movement occurred ferentiation of salt ridges produced the after the influx of Cotton Valley clastic present complex array of salt domes and anti- sediment during the Late Jurassic (Fig. 1). clines of the East Texas Basin. Seismic and Before that time, deposition in the East Tex- gravity data clearly demonstrate the exis- as Basin was dominated by carbonates, evapor- tence of these salt ridges and intervening ites, and marine mudstones and claystones. sediment thicks. Salt movement apparently was controlled by differential loading of Upper Jurassic and Lower Cretaceous fluvial-deltaic systems, as Introduction well as by the position of the subjacent Smackover-Gilmer carbonate shelf complex The Cotton Valley Group (Upper Jurassic) (Jackson and Harris, 1981; McGowen and Har- and Hosston Formation (Lower Cretaceous) were ris, 1981) . studied as part of the East Texas Waste Iso- lation project being conducted by the Bureau Data Base of Economic Geology for the U. S. Department of Energy. The purpose of the project is to Electric logs from 232 wells (Fig. 2) , assess the suitability of salt domes in the supplemented by Bouguer residual gravity maps East Texas Basin as potential repositories and two dip-oriented, six-fold conventional for nuclear waste; this suitability is con- CDP seismic profiles, served as a data base tingent on the tectonic stability of the for this study. When possible, well data domes. The objective of the present analysis were integrated with seismic data by using was to investigate the effect of early basin velocity conversion tables. Five seismic re- infilling on salt mobilization in the East flectors within the Mesozoic were used, in- Texas Basin. Understanding the mechanisms cluding the base of the Louann Salt, the top responsible for early salt movement is essen- of the Louann Salt, the top of the Gilmer tial to predicting domal growth evolution and Limestone (Cotton Valley Limestone) (Forgotson ultimate stability. and Forgotson, 1976), and the top of the Pet- An area in the northwestern part of the tet Limestone (Table 1). The fifth reflect- East — Texas Basin consisting of seven coun- or, which we believe is the top of the Mas- ties Hunt, Hopkins, Wood,— Rains, Kaufman, sive Anhydrite, was used in the northern part Van Zandt, and Henderson was selected for of the basin, where the Pettet Formation the study of the relationship between salt changes lithologically from a limestone fa- movement and the influx of Upper Jurassic cies to a sandy facies and thereby loses its terrigenous clastic sediment. The study area character as a distinct seismic reflector. was chosen for two reasons: first, because The Louann Salt is characterized by prominent preliminary studies indicated the presence of boundary reflections (Jackson and Harris, a fan-delta system prograding from the north- 1981). Its inferred thickness, based on McGowen and Harris/Depositional Systems in the East Texas Basin 215

Table 1. Seismic reflectors and seismic units in the northwestern part of the East Texas Basin

SEISMIC REFLECTOR SEISMIC UNIT Upper Navarro Marl Top of the Pecan Gap Chalk Top of the Austin Chalk Top of the Buda Limestone *Top of the Massive Anhydrite?- — — — >

*Top of the Pettet Limestone ■ D —" *Top of the Gilmer Limestone — C | *Top of the Louann Salt ______B ~" *Base of the Louann Salt A *Seismic reflectors used in this study.

gravity data. Zones of thicker salt generally coincide with gravity lows, whereas areas of thinner salt correspond to gravity highs (Jackson and Harris, 1981) (Fig. 3). Isopach, net-sandstone, and sandstone- percent maps of the Cotton Valley Group and the Hosston Formation were prepared. The boundary between the two was based on scout card information and regional correlations within the East Texas Basin. Using the Pet- tet Limestone as a datum, nine stratigraphic cross sections were constructed within the study area; selected sections are included in this report (Fig. 2). Limitations of this data base include the following: First, although well spacing within individual oil and gas fields is good, overall spacing is poor, precluding detailed mapping of the Cotton Valley Group and Hos- ston Formation on a regional scale. Second, because conventional-core data were not available to verify environmental interpretations, facies designations were based entire- ly on electric log response and on sand-body geometry determined from net-sandstone maps, sandstone-percent maps, and textural and com- Figure 1. Stratigraphic succession and no- positional features observed in well cut- menclature in the East Texas Basin (Wood, tings. And third, because Jurassic forma- 1981). tions in northeast Texas are restricted to the subsurface, facies relationships of sur- seismic interpretation, was correlated with face exposures could not be examined. 216 The Jurassic of the Gulf Rim

Figure 2. Index map showing well control, well cuttings, and location of stratigraphic cross sections

Previous Work rial include Imlay (1943), Swain (1949), For- gotson (1954), Bushaw (1968), Dickinson Early work on the Cotton Valley Group (1968), Nichols et al., (1968), and Newkirk (Upper Jurassic) and the Hosston Formation (1971). Todd and Mitchuro (1977) were the (Lower Cretaceous) in the East Texas Basin first to present seismic data on the Jurassic emphasized regional stratigraphic and envi- section in East Texas and identified several ronmental synthesis; the limited number of distinct seismic sequences within the section wells penetrating the Jurassic section pre- by integrating seismic data witn lithologic, cluded more detailed studies. Regional stud- environmental fecies, biostratigraphic, radi- ies that provide excellent background mate- oiitetric, and well-log information. McGowen and Harr is/Depositional Systems in the East Texas Basin 217

Figure 3. Generalized residual gravity map (modified from map done by Exploration Techniques, Inc.). 218 The Jurassic of the Gulf Rim

Tectonic Framework away from the incipient rift, allowing large quantities of terrigenous elastics to enter The East Texas Basin is recognized as a the basin only when the dip of the rift mar- subbasin, or reentrant, of the larger Gulf gin reverses. The major influx of terrigen- Coast Basin (Wood and Walper, 1974; Walper, ous elastics into the East Texas Basin during 1980). Most researchers agree that the East the Late Jurassic (Cotton Valley) and Early Texas Basin was formed from one of either the Cretaceous (Hosston) may reflect this dip re- megashear zones, the rift grabens, or the au- versal. lacogens that formed along the margins of the Gulf of Mexico, probably coincident with the Salt Tectonics breakup of Pangea and the separationof North and South America during the Triassic (Kehle, Two general observations about salt 1971; Burke and Dewey, 1973; Moore and Del structures in the East Texas Basin can be Castillo, 1974; Wood and Walper, 1974; Beall, made: First, the size and type of salt-re- 1975; Salvador and Green, 1980). Kehle lated structures seem to be directly control- (1971) suggested that the interior salt ba- led by the thickness of the underlying salt. sins of Mississippi and northern Louisiana This relationship was also observed in the also are foundered grabens that are marginal interior Mississippi salt basin by Hughes to the ancestral Gulf Coast Basin. Major (1968). Second, salt apparently migrated at tectonic elements in and around the East Tex- different times in different parts of the as Basin are shown in Figure 4. East Texas Basin through several mechanisms: faulting (common in the marginal areas of the Tectonic History basin) (Parker and McDowell, 1955; Rosenkrans and Marr, 1967; Hughes, 1968); gravity glid- Kehle (1971) and Wood and Walper (1974) ing of post-Louann strata, which was caused maintained that the development of the inter- by basinward tilting (Kehle, 1971; Jackson ior salt basins resulted from the opening of and Harris, 1981); and mass imbalance caused the Gulf of Mexico. They described the his- by uneven sediment loading (Rogers, 1967; tory of these interior salt basins as fol- Turk, Kehle, and Associates, 1978; McGowen lows: The interior salt basins (Mississippi, and Harris, 1981). North Louisiana, East Texas, and Salinas Ba- sins) represent the most marginal grabens Dome growth mechanisms Kehle (1971) main- that are associated with continental rifting. tained that uneven sediment loading is the These grabens were initially filled with al- dominant mechanism responsible for salt dome luvial-fan deposits of the Eagle Mills Forma- initiation. He observed that the density in- tion. With prolonged spreading, however, the version caused by uneven sediment loading is interior grabens continued to founder. The accentuated in the resulting salt flow be- southern margin of the East Texas Basin may cause the viscosity of salt is highly sensi- have been elevated, thereby restricting cir- tive to shear stress. Kehle concluded that culation of sea water between the basin and the unequal pressure gradient set up within a the Gulf of Mexico. Evaporites of the Werner salt mass because of uneven sediment loading Anhydrite and Louann Salt were precipitated, is dependent on the slope of the overlying possibly by the brine-mixing process (Fig. 7 sediment, which in the present study is a of Raup, 1970). deltaic lobe. Continued subsidence resulted in open Loocke (1978) applied this principle to marine conditions; this is evidenced in the the East Texas Basin, suggesting that the widespread occurrence of carbonates in the growth of the Hainesville salt dome (south- Smackover and Gilmer Formations. One of the central Wood County) was initiated by mass characteristics of rifting is that during the imbalance caused by the progradation of Cot- early stages the bounding crustal blocks tilt ton Valley deltas into that part of the ba- McGowen and Harris/Depositional Systems in the East Texas Basin 219

Figure 4. Tectonic elements in and around the East Texas Basin sin. By the end of Hosston (Early Creta- derlying salt, which controls the supply of ceous) sedimentation, the structure had grown salt for continued growth. into a topographically high salt pillow, or anticline (Loocke, 1978). The evolution of Timing of initial salt movement Two seis- initial salt anticlines into salt domes de- mic profiles available in the study area doc- pends on continued sediment loading (Kehle, ument the timing of salt mobilization (Figs. 1971) as well as on the thickness of the un- 5 and 6). Profile S-1 extends northwest to 220 The Jurassic of the Gulf Rim

Figure 5. Time-to-depth conversion section S-1. Seismic units A, B, and C refer to Table 1. Southeastern end of line shows salt- withdrawal feature associated with Mount Sylvan salt dome.

southeast through Kaufman, Van Zandt, north- central Henderson Counties (Figs. 5 and 6). eastern Henderson, and western Smith Coun- Time-thickness variations are apparent be- ties; profile S-2 trends north to south tween reflections at the top of the Louann through Delta, Hopkins, Wood, and Smith Coun- Salt and the top of the Gilmer Limestone ties. (seismic unit B, Table 1). No thickness var- Seismic data suggest that salt movement iations caused by salt movement were observed was both pre-Gilmer and coeval with Cotton in the seismic interval between the top of Valley-Hosston deposition (Jackson and Har- the Gilmer Limestone and the top of the Pet- ris, 1981; McGowen and Harris, 1981). Pre- tet Limestone (seismic Unit C, Fig. 5) or be- Gilmer salt migration occurred in an area tween the top of the Gilmer Limestone and the north and west of a line through central top of the Massive Anhydrite (seismic unit D, Wood, eastern Rains, central Van Zandt, and Fig. 6). Thus, it can be concluded that salt McGowen and Harris/Depositional Systems in the East Texas Basin 221

Figure 6. Time-to-depth conversion section S-2. Seismic units A, B, C, and D refer to Table 1. Fault traces projected to surface on the basis of Barnes (1965, 1966). Seismic picks by D.W. Harris and C.D. Winker. Time-to-depth conversion by R.E. Anderson and T.E. Ewing based on electric logs and seismic velocity analysis. 222 The Jurassic of the Gulf Rim

moved during Smackover deposition, which pre- (1978) maintained that major displacement a- ceded Cotton Valley-Hosston deposition. long the fault zone was largely caused by During Cotton Valley-Hosston deposition, downdip creep of the Louann Salt. Jackson salt moved south and east of a line through and Harris (1981) suggested that fault dis- central Wood, eastern Rains, central Van placement was also caused, in part, by basin- Zandt, and central Henderson Counties. The ward creep of clastic strata above the Louann seismic interval between the top of the Gil- decollement zone. Movement along the fault mer Limestone and the top of the Pettet Lime- affected strata of Mesozoic through early stone (seismic unit C, Fig. 5) apparently Tertiary age. thins over salt structures and thickens with- Basinward of the Mexia-Talco fault zone, in synclines caused by salt withdrawal. In a second graben system (the Edgewood Graben) contrast, the seismic interval between the developed parallel to the Mexia-Talco trend reflections at the top of the Louann Salt and (Rosenkrans and Marr, 1967) (Fig. 7). These top of the Gilmer Limestone (seismic unit B, faults were active during the Jurassic and Fig. 5) appears to be planar. This relation- became inactive during the Early Cretaceous ship is not as discernible on profile S-1 before deposition of the Pettet Limestone (Fig. 5) as on profile S-2 (Fig. 6) because (Fig. 6). These faults and related struc- seismic resolution is poor on the deep strat- tures are discussed in more detail in the igraphic horizons in southern Wood County. section titled "Low- to Intermediate-Ampli- tude Salt Structures." Structural Styles Deformation-free zone On both seismic pro- Structural styles within the East Texas files S-1 and S-2, a deformation-free zone Basin can be grouped into four general cate- between the peripheral graben system and the gories: a peripheral graben system; a defor- first occurrence of low-amplitude salt swells mation-free zone; low- to intermediate-ampli- (Figs. 5 and 6) underlies Delta and Hopkins tude salt structures, which show pre-Cotton Counties to the north and Kaufman and western Valley salt movement; and salt anticlines and Van Zandt Counties to the west. The Louann domes, which show movement coincident with Salt is recognized by prominent boundary re- Cotton Valley-Hosston deposition. These fea- flections and lack of internal reflections tures have been discussed by Kehle (1971) and (Jackson and Harris, 1981). Within the de- Jackson and Harris (1981), and similar struc- formation-free zone, boundary reflections are tures have been observed in the Mississippi planar and diverge basinward, indicating a (Hughes, 1968) and the North Louisiana (Keh- thickening of the salt wedge (approximately le, 1971) salt basins. 1,020 to 1,920 feet, or 340 to 640 m) (Jack- son et al., 1982). Existence of the deforma- Peripheral graben system The Mexia-Talco tion-free zone suggests that a critical fault zone bounds the study area on the north thickness of salt (approximately 1,500 feet, and west. The position of the fault system or 500 m) must be present to initiate flow marks the updip depositional limit of the (Jackson et al., 1982). Kehle (1971) main- Louann Salt (Kehle, 1971; Agagu et al., 1980; tained that the deformation-free zone is dis- Jackson and Harris, 1981). The fault zone is continuous along the full length of the basin a series of en echelon normal faults and margin. grabens that formed early in the history of the basin. However, there is no evidence on Low- to intermediate-amplitude salt struc- seismic lines observed during this study tures Low-amplitude salt structures oc- that the peripheral faults extend into the cur basinward of the deformation-free zone in basement. Rather, evidence suggests that southern Hopkins, southern Rains, and western the grabens are based in the Louann Salt Van Zandt Counties. Amplitudes, indicated by (Jackson, 1982). Turk, Kehle, and Associates relief on the top of the salt anticlines, in- McGowen and Harris/Depositional Systems in the East Texas Basin 223

Figure 7. Salt domes and major fault systems, northwestern part of the East Texas Basin crease basinward as the salt wedge thickens. deposition of the Smackover Formation; this Basinward, folds are commonly tighter and is evidenced by time-thickness variations be- salt has pierced some anticlines (Hughes, tween reflections on the top of the Louann 1968; Kehle, 1971). Seismic profiles indi- Salt and the top of the Gilmer Limestone cate that these low- to intermediate-ampli- (Figs. 5 and 6). Salt migration was probably tude structures formed early in the develop- initiated by downward creep that was induced ment of the basin. Salt movement began during by sedimentary loading of carbonate deposits 224 The Jurassic of the Gulf Rim

(Rogers, 1967) and was enhanced by basinward most of the movement occurred after deposi- tilting. Residual gravity maps suggest that tion of the Gilmer Limestone. And third, these initial salt structures are aligned seismic unit D thickens on the downthrown roughly parallel to the Mexia-Talco fault side of the fault, not on the upthrown side, zone (Figs. 3 and 4). Hughes (1968) deduced indicating that movement along the fault was that salt movement occurred as early as depo- contemporaneous with deposition of the Cotton sition of the Norphlet in the Mississippi Valley Group. The fault terminates within salt basin. He also observed that low-ampli- seismic unit D (Hosston Formation). tude salt structures in marginal areas of the Evidence of faults that were active basin are commonly arranged in ridges that northwest of Van Dome during Cotton Valley- parallel the peripheral faults. Hosston deposition is shown on seismic pro- Most growth of low-amplitude salt struc- files S-1 (top structure, Fig. 5). First, tures apparently occurred before deposition updip of the fault, seismic unit A (Table 1) of Cotton Valley clastic sediment. This is is distorted, and the configuration of the evidenced on seismic profiles, which show Louann Salt cannot be discerned. Second, little variation in time-thickness between seismic unit B thickens slightly basinward of the reflections at the top of the Gilmer the fault, suggesting that salt movement oc- Limestone and the top of the overlying Pettet curred during Smackover deposition. Third, Limestone. The low-amplitude salt features the Gilmer Limestone reflection is clearly exhibit little to no structural expression offset at the fault. Fourth, seismic unit C above the Gilmer Limestone. The thin under- thickens appreciably on the downthrown side lying salt wedge appears to have largely con- of the fault, indicating movement contempor- trolled the size of the structures that form- aneous with deposition of Cotton Valley clas- ed in this part of the basin. tic sediment. And fifth, the fault termi- Near the Edgewood Graben (Fig. 7), salt nates either in the upper part of the Cotton structures of intermediate size are truncated Valley or in the Hosston below the Pettet re- by the fault system. Rosenkrans and Marr flection, which is planar. (1967) maintained that the salt structures were generated by faulting, and Jackson and Salt anticlines and domes. Within the study Harris (1981) concluded that salt withdrawal area, salt anticlines and domes occur south by downdip creep, coincident with sediment and east of a line through southern Hopkins, loading within the graben, may have caused eastern Rains, central Van Zandt, and central the faults. Fault movement along the system Henderson Counties (Fig. 8). The location of displaced strata of Late Jurassic and Early salt anticlines and domes in the basin ap- Cretaceous age but ended in the Early Creta- pears to have been controlled largely by the ceous. Seismic profile S-2(Fig. 6) indicates location of the Smackover-Gilmer carbonate that faulting was contemporaneous with depo- platform, particularly where Gilmer carbonate sition of Cotton Valley clastic sediment. shelf-edge strata overlie Smackover deposits. Seismic profile S-2 (Fig. 6) also shows Rogers (1967) maintained that a carbonate evidence of displaced reflections along the shelf-edge facies began to form during Smack- Edgewood graben during deposition of the Cot- over deposition and continued in some areas ton Valley-Hosston strata. The following re- during Gilmer deposition, reaching a maximum lationships were observed: First, a salt combined thickness of 3,500 feet (1,166 m) structure underlies the Edgewood fault, but (Fig. 9). A carbonate shelf of this thick- the exact relationship of the structure to ness could provide a stable platform, upon the fault is not clear on the seismic pro- which fan-delta sediments of the Cotton Val- file. Second, reflection of the Gilmer Lime- ley Formation would tend to spread laterally stone is offset down to the basin without ap- rather than to stack vertically. The isopach preciable time-thickness variations within map of the Cotton Valley Group indicates a seismic unit B (Table 1), indicating that close correlation between the position of the McGowen and Harris/Depositional Systems in the East Texas Basin 225

Figure 8. Structure map of the top of the Pettet Formation and the top of the Hosston Formation (Hunt County only). 226 The Jurassic of the Gulf Rim

modified by continued salt flow, which resulted from uneven sediment loading by younger sedimentary units. Johnson (1980) showed that a preexisting salt ridge on the outer continental shelf and upper slope of the Gulf Basin evolved into individual salt domes when buried by an influx of fluvial-deltaic sediments during the Pliocene. A residual gravity map of the study area indicates a parallel arrangement of lows and highs (Fig. 3). A comparison of the Cotton Valley isopach map (Fig. 10) with the residual gravity map shows that sediment thicks generally coincide with gravity highs and salt thins, whereas sediment thins coincide with gravity lows and areas of thicker salt. The approximate parallel alignment of residual gravity lows again suggests that the Figure 9. Isopach map of Smackover-Gilmer original salt structures may have been a ser- carbonate shelf facies (Rogers, 1967). Iso- ies of parallel salt ridges that evolved pach of Smackover northwest of dashed line, through time into salt anticlines and domes. combined isopach of Smackover and Gilmer Seismic lines across the salt anticlines southeast of dashed line. and domes in the study area indicate that in most cases, salt moved after deposition of Smackover carbonate shelf edge, as mapped by the Gilmer Limestone, whereas low-amplitude Eaton (1961) and Rogers (1967), and the oc- structures located in the marginal areas in- currence of Cotton Valley deltaic depocenters dicate pre-Gilmer movement. Deeper seismic (Fig. 10). Superposition of deltaic sedi- reflections near Quitman Dome (Wood County) ments occurred in synclines that were located are distorted, and thus obscure the relation- between salt ridges and were immediately ba- ship between the salt structure and the over- sinward of the older carbonate wedge. Salt lying sedimentary units. However, a seismic mobilization was initiated by basinward mi- survey profile across Mount Sylvan Dome gration of the salt into ridges that fronted (Smith County) shows virtually no evidence of the progradational fan-delta system. The pre-Cotton Valley salt movement (Fig. 6). salt ridges probably were bathymetric highs West Tyler, to the southeast of Mount Sylvan that acted as effective sediment dams to per- Dome, and Boynton Field, to the northwest, petuate the synclines as depocenters until are turtle structures created by early salt either the underlying salt was depleted or withdrawal that started coeval with Cotton the rate of sedimentation was greater than Valley deposition (Jackson et al., 1982). the rate of subsidence. This allowed the Turtle structures are anticlinal structures delta to overrun the salt ridge. without salt cores that were created by sedi- During continued progradation, the fan- ment thicks in primary withdrawal basins delta complex probably overran the initial formed by early salt withdrawal (Trusheim, syncline and salt ridge and established a new 1960; Kehle, 1971; Wood, 1981). Turtle depocenter basinward of and parallel to the structures probably were depocenters during original salt ridges. Consequently, sedi- deltaic sedimentation of the Late Jurassic. ments in depocenters should be progressively Seismic profile S-1 passes to the south younger toward the center of the basin. Ini- of Grand Saline and Van Domes but crosses two itial salt ridges that developed during the parallel, lateral salt ridges that extend Late Jurassic and Early Cretaceous were later southeastward from Van Dome (Figs. 3 and 5) McGowen and Harris/Depositional Systems in the East Texas Basin 227

Figure 10. Isopach map of the Cotton Valley Group

(Jackson and Harris, 1981). The seismic sur- ever, was coincident with deposition of Cot- vey across the western ridge indicates that ton Valley deltaic sediments (seismic unit C, some pre-Gilmer salt movement occurred (seis- Fig. 5). Basinward of the western ridge, no mic unit B, Fig. 5). Major movement, how- pre-Gilmer salt movement apparently occurred. 228 The Jurassic of the Gulf Rim

Summary evolved to describe these deposits. Because this study deals primarily with sedimentation Seismic profiles indicate that salt during the Late Jurassic and Early Creta- movement occurred at different times in dif- ceous, a rock-stratigraphic classification ferent parts of the East Texas Basin and dem- restricted to those times has been used. No onstrate that more than one mechanism caused attempt has been made to classify the Cotton movement. Within marginal parts of the ba- Valley Group in the northwestern part of the sin, low-amplitude salt structures formed basin using the stratigraphic nomenclature during Smackover (pre-Gilmer) time. Salt mi- that has been applied to the eastern part of gration was caused by loading of the Smack- the basin and to Louisiana. over carbonate deposits in conjunction with In this study, the boundary between the basinward tilting. Time-thickness variations Cotton Valley Group and the Hosston Formation caused by low-amplitude salt structures are is arbitrary, based on regional correlations not indicated on Cotton Valley-Hosston iso- and information of geologic picks from scout pach maps. The sizes of salt structures in- cards. In the northwestern part of the East crease basinward, coincident with thickening Texas Basin, the top of the upper Cotton Val- of the underlying salt wedge. ley Group is difficult to pick on electric Basinward of a line running through cen- logs and seismic profiles because Hosston tral Henderson, Van Zandt, and Wood Counties, sandstones overlie upper Cotton Valley sand- salt movement occurred later than it did in stones. Nichols et al. (1968) maintained the marginal parts of the basin. Salt migra- that deposition was continuous through Late ted during deposition of Cotton Valley-Hos- Jurassic and Early Cretaceous time except ston strata as a result of mass imbalance, around the western and northern margins of which was caused by uneven sediment loading. the basin, where an erosional contact was Time-thickness variations (divergence) are recognized. In these marginal areas, a basal evident between seismic reflections at the Hosston conglomerate, ranging in thickness top of the Gilmer Limestone and the top of from 50 to 100 feet (16 to 33 m) , separates the Pettet Limestone. In contrast, reflec- the two formations (Nichols et al., 1968). tions at the top of the Louann Salt and the It has not been determined whether this con- top of the Gilmer Limestone are parallel, glomerate bed occurs regionally or whether it suggesting that salt did not move in this consists of unrelated local facies, such as part of the basin until Cotton Valley time. proximal alluvial-fan deposits or braided- stream channel-fill deposits. On the basis of seismic interpretations, Todd and Mitchem Sedimentologic Framework (1977) recognized a major unconformity between the Cotton Valley Group (Upper Juras- Methodology sic) and the Hosston Formation (Lower Creta- ceous) in the East Texas Basin. However, we Early Jurassic sedimentation was domi- did not recognize a major unconformity on nated by the deposition of carbonate, evapor- seismic sections in the nort'iwostern part of ite, and mudstone facies. The first major the basin. The depositional sequence be- influx of terrigenous clastic sediment into tween either the Gilmer Limestone (Cotton the East Texas Basin occurred during the Late Valley Limestone) or the base of the Buckner Jurassic (Cotton Valley) and continued into Anhydrite and the top of the Hosston Forma- the Early Cretaceous (Hosston). tion is thought to represent one regressive Basin infilling during the Late Jurassic sequence with minor interruptions. The re- and Early Cretaceous produced a variety of gression was terminated by & major trans- complexly distributed facies in the East Tex- gression, which is evidenced by the transi- as Basin and the adjacent North Louisiana Ba- tion of the uppermost Hosstc i formation into sin. As a result, a complex nomenlature has the Pettet Limestone. McGowen and Harris/Depositional Systems in the East Texas Basin 229

The volume, texture, and composition of system in Louisiana and Mississippi, where an sediment, the nature of the sediment-disper- ancestral Mississippi River was the principal sal system, and the geometry of sands of the fluvial system entering the North Louisiana Cotton Valley Group and Hosston Formation Basin (Thomas and Mann, 1966). were studied using sandstone-percent and net- Tongues of quartz conglomerate along the sandstone maps. These were supplemented by northwestern and northern margins of the ba- regional stratigraphic cross sections, elec- sin in the Cotton Valley Group and throughout tric logs, isopach maps, and well cuttings. the Hosston Formation were probably derived A sandstone-percent map is an effective way from the Ouachita, Arbuckle, and Wichita to reveal sand-body geometry because it mini- highlands. Textural maturity and the domi- mizes the effect of thickness variations nance of very fine grained to fine-grained within a mappable unit (Krumbien and Sloss, sandstone suggest that older sedimentary rock 1959; Kaiser et al., 1978). Stratigraphic surrounding the basin during the Late Juras- markers are virtually absent in the Cotton sic and Early Cretaceous was also an impor- Valley Group and Hosston Formation within the tant source of terrigenous clastic sediment northwestern part of the basin; therefore, for the East Texas Basin. Most of the sand- sandstone maps represent the composite sandstone is quartzarenite and subarkose. stone thickness of superposed facies. The cumulative values do not reflect the geometry Depositional Systems of individual sand bodies, so interpretation of individual depositional systems from these Fan-delta processes and environments. The maps should be done cautiously. Brown (1969) Cotton Valley Group and the Hosston Formation observed that some depositional systems ap- are thought to be a large fan-delta deposi- pear to remain in approximately the same geo- tional system. A fan delta is an alluvial graphic position through time; when this oc- fan that progrades into a body of water from curs, similar systems would tend to stack an adjacent highland (Holmes, 1965; McGowen, vertically and thus be revealed in a gross 1970). Fan-delta deposits exhibit a higher lithologic map. ratio of coarse-grained to fine-grained sediment than either lobate or elongate deltas Source Area (Erxleben, 1975). Characteristically, fan deltas have relatively small drainage areas The same source area supplied terrige- and flashy runoff, and they are supplied by nous elastics to the East Texas Basin during bed-load streams braided to the toe of the both the Late Jurassic (Cotton Valley) and delta (McGowen, 1970). Aggradation and pro- the Early Cretaceous (Hosston). Deposition gradation occur only during periods of high of Cotton Valley terrigenous elastics in the discharge (McGowen, 1970). East Texas Basin suggests that a reactivation Rates of progradation are controlled by of this source area along the northern and sediment supply, by discharge rates of the western margins of the basin began as early fluvial system supplying the fan delta with as the Late Jurassic. The Central Mineral sediment, by intensity of marine processes Region and the Ouachita, Arbuckle, and Wichi- (whether the fan delta is debouching into a ta Mountains were all highlands during the low-energy or high-energy marine environ- Late Jurassic and Early Cretaceous (Imlay, ment), and by depth of water. Heavy seasonal 1943) (Fig. 4). rains or floods are essential to providing Patterns of the net-sandstone and sand- discharge rates capable of transporting large stone-percent maps (Figs. 19 and 20) suggest quantities of sand-size sediment to the toe that during the Late Jurassic, terrigenous of the fan delta. Sediment is stored in elastics were delivered to the East Texas Ba- channels during periods of low rainfall, sin by many small streams and rivers. This whereas sediment is entrained during floods, differs from the major river and tributary when rapid progradation occurs (Casey, 1980). 230 The Jurassic of the Gulf Rim

Figure 11. Gum Hollow fan-delta model (McGowen, 1970).

McGowen (1970) attributed major growth of the of bed-load streams with rapid discharge Gum Hollow fan delta to three principal depo- fluctuations. Finer sediment is transported sitional events: The heavy spring rains of through the system without accumulating; con- 1966 and the heavy rains associated with Hur- structional features include both longitudin- ricane Beulah in 1967 and with Tropical Storm al and transverse bars. With the absence of Candy in 1968. During periods of low fluvial muddy levees and top strata, the channel discharge, distal parts of the active fan banks are easily eroded; thus, bars tend to deltas are modified by marine processes. In- laterally coalesce, forming continuous and active lobes are subject to destructional extensive sand sheets (Walker and Cant, processes year round. The greatest rates of 1979) (Fig. 12). progradation occur when fan deltas debouch The distal fan includes the transitional into shallow-water low-energy environments. zone between the subaerial fan plain and the Progration is accomplished by lateral shifts subaqueous part of the fan delta (McGowen, in sites of deposition, resulting in a com- 1970). Fluvial and marine interaction pro- plex overlapping of fan-delta lobes (Casey, duces a complex environment. Marine pro- 1980) . cesses dominate this part of the fan delta McGowen (1970) subdivided— fan deltas in- except during periods of high discharge, when to two— subenvironments fan plains and distal fluvial influence is evident. During periods fans based on their dominant sedimentary of low discharge, delta-front sediments are process (Fig. 11). The fan plain includes reworked into bars, spits, and shoals (Lucchi the subaerial part of the fan delta and is et al., 1981) (Fig. 13). Inactive fan delta dominated by braided-stream fluvial proces- lobes are continuously modified. Character- ses. A braided stream is defined by Leopold istic environments include marshes, destruc- et al. (1964) as a channel divided into sev- tional bars, intertidal zones, and eolian eral channels that successively meet and re- mounds (McGowen, 1970). Benthic fauna may divide. A braided-stream system is composed migrate into the delta front and the aban- McGowen and Harris/Depositional Systems in the East Texas Basin 231

Figure 12. Braided-stream model (Rust, 1978). doned channel areas (Casey, 1980). fan deltas also varies. However, many of the Wescott and Ethridge (1980) presented an processes controlling sedimentation are simi- excellent synopsis of modern and ancient de- lar. For example, the fan deltas are fed by posits that are thought to be fan delta sys- braided-stream fluvial systems that exhibit tems. Examples of modern fan deltas that de- rapidly fluctuating discharge rates, which bouch into marine environments include the are controlled by seasonal events; most of Gum Hollow fan delta (McGowen, 1970), the the fans prograde into relatively shallow Yallahs fan delta (Wescott and Ethridge, water (the width of the shelf varies with 1980), and the fan deltas associated with each geographic location). glacial outwash along the coast of Iceland (Ward et al., 1976; Boothroyd and Nummendal, Cotton Valley-Hosston fan-delta system 1978) and the coast of Alaska (Boothroyd and Deposits of the Cotton Valley Group and Hos- Ashley, 1975; Boothroyd, 1976; Galloway, ston Formation are thought to be a system of 1976; Boothroyd and Nummedal, 1978). Temper- coalescing fan deltas that prograded from the atures vary considerably between these geo- west, northwest, and north. Facies interpre- graphic areas; the intensity of marine pro- tations are based on sandstone-percent val- cesses affecting the distal margins of the ues, sandstone distribution, electric log re-

Figure 13. Diagrammatic cross section of fan-delta subenvironments (after Lucchi et al., 1981). 232 The Jurassic of the Gulf Rim

sponse patterns, descriptions of well cut- Higher sandstone-percent values are restrict- tings (appendix A) , and lithologic descrip- ed to the basin margin, and values decrease tions from other studies. Lack of core data basinward. Many dip-oriented sandstone-rich precludes the study both of sedimentary belts extend across Kaufman, Hunt, Hopkins, structures and of detailed relationships and northwestern Van Zandt Counties, suggest- among vertical sequences of facies within the ing the presence of many smaller streams in Cotton Valley Group and Hosston Formation. this part of the study area. Basinward, the — dip-oriented sandstone geometry appears to Cotton Valley Group. Facies. Facies of the change into a northeast to southwest strike- Cotton Valley Group can be divided into three oriented trend. The change in orientation of general categories: prodelta deposits, delta- sandstone trends marks the fluvial-marine in- front deposits, and braided stream deposits, terface. Seaward of this area, dominant ma- all components of a fan-delta system (Figs. rine processes had reworked sandstones into 2, 14 through 18). Prodelta deposits compose strike-oriented facies. This change in ori- a thin subordinate facies in the study area; entation seems to coincide with the position however, the facies thickens basinward. It of an older Smackover-Gilmer carbonate shelf consists of black or green calcareous, fos- described by Eaton (1961) and Rogers (1967) siliferous mudstone interbedded with light- (Fig 9). gray to light-brown crystalline limestone and The Cotton Valley Group gradually thick- shelly, sandy limestone. Minor amounts of ens basinward toward a line that runs through very fine-grained sandstone and siltstone oc- central Henderson, central Van Zandt, and cur within the facies. north-central Wood Counties (Fig. 10). Ba- Delta-front deposits consist of alter- sinward of this line, the isopach contours nating beds of sandstone and mudstone and a outline parallel-aligned, strike-oriented few thin beds of sandy limestone. Sandstone, thicks and thins. When compared with the re- the dominant lithology, is white to light sidual gravity map (Fig. 3) , sediment thicks gray and very fine-grained to fine-grained, correspond to salt-poor (gravity highs) , and containing glauconite, shells, and finely sediment thins overlie salt structures (grav- disseminated carbonized plant fragments. In- ity lows). Parallel sandstone thicks indi- terbedded mudstone is dark gray to black to cate successive seaward depocenters of pro- green. Thick beds of conglomeratic sandstone grading fan deltas. occur in the proximal areas. The area where the Cotton Valley Group Braided-stream fluvial deposits consist gradually thickens basinward is coincident of white to light red, very fine-grained to with subjacent Smackover-Gilmer carbonate fine-grained sandstone, conglomeratic sand- shelf facies. The combined thickness of the stone, and chert-gravel quartz and conglomer- Smackover-Gilmer deposits is approximately ate. Thin beds of red and green mudstone oc- 3,500 feet (1,067 m). The isopach map of the cur as a subordinate lithology. Conglomerate Cotton Valley suggests that the Smackover- is more common updip, extending basinward as Gilmer shelf was a stable platform over which tongues (Newkirk, 1971). This facies exhib- the advancing Cotton Valley fan deltas pro- its blocky electric log patterns with sharp graded both laterally and basinward. Super- (erosional) bases and tops, characteristic of position of deltaic sediments occurred in braided-stream deposits (Erxleben, 1975; Gal- synclines that were located between salt loway et al., 1979). Well-developed upward- ridges immediately basinward of the Smack- coarsening or upward-fining sections are rare over-Gilmer carbonate shelf edge. The thick- to absent. ness of the Louann Salt, which directly de- — termined the amount of salt available for the Sandstone Distribution. Sandstone distribu- formation of salt structures, also controlled tion in the Cotton Valley Group is indicated the rate and amount of subsidence that occur- on the sandstone-percent map (Fig. 19). red coeval with sedimentation. McGowen and Harris/Depositional Systems in the East Texas Basin 233

Counties Wood and Hopkins through A-A' section cross Stratigraphic 14. Figure 234 The Jurassic of the Gulf Rim

Counties Wood and Rains, Hunt, through B-B' section cross Stratigraphic 15. Figure McGowen and Harris/Depositional Systems in the East Texas Basin 235

The net-sandstone map indicates that Electric log patterns of individual sand beds sandstone-rich belts coincide with thick iso- are blocky and have sharp (erosional) lower pach trends of the Cotton Valley Group (Fig. and upper boundaries. Upward-fining and up- 20). Net-sandstone values increase gradually ward-coarsening log responses are rare. Su- across the Smackover-Gilmer shelf; beyond the perposition of braided-stream deposits, oc- shelf edge, net-sandstone highs correspond to curring contemporaneous with faulting, is not sediment thicks indicated on the Cotton Val- as apparent here as it is in the Cotton Val- ley isopach map (Fig. 10). Net-sandstone ley Group. thicks coincide with salt-poor areas (Fig. The upper 100 to 200 feet (33 to 67 m) 3). of the Hosston Formation consists of inter- Sediment accumulation around the north- bedded white to light-red, very fine-grained ern and western margins of the basin appears to fine-grained sandstone; gray mudstone; and to have been controlled, in part, by contem- gray to light-tan sandy, fossiliferous, oo- poraneous faulting in the Mexia-Talco fault litic limestone. Uppermost Hosston deposits zone. In Kaufman County, for example, mas- reflect a decrease in the sediment supply to sive sandstone units in the upper Cotton Val- the East Texas Basin because of a shift from ley Group are up to 600 feet (183 m) thick. dominantly fluvial deposits to dominantly ma- These units are thought to be superposed rine deposits. braided-stream deposits that accumulated ear- — ly in grabens of the Mexia-Talco fault zone. Sandstone Distribution. Sandstone distribu- Subsidence was accelerated by accumulation of tion within the Hosston Formation is charac- thick braided-stream deposits composed of terized by dip-oriented sandstone-rich belts quartz and pebble conglomerate and fine- to in proximal areas (Fig. 21). There is, how- medium-grained sandstone. ever, a change from many dip-oriented high- — sandstone-percent trends in the Cotton Val- Hosston Formation.Fades. Two facies con- ley to a single dominant dip-oriented sand- stitute the Hosston Formation: a braided- stone trend in the Hosston centered in Hunt stream facies, which is dominant, and a tran- County (Figs. 19 and 21). Narrower sand- sitional shallow marine facies, which is sub- stone-percent trends in the Hosston occur ordinate. The braided-stream deposits repre- around the northern margin of the basin (Fig. sent the subaerial fan-plain facies, a compo- 22). The sandstone-percent map suggests that nent facies of the larger fan-delta system the Cotton Valley drainage system had (Figs. 11 through 13). Fluvial sedimentation evolved, by Hosston time, from an immature ended with a major transgression reflected by fluvial complex made up of many smaller a transitional shallow marine facies re- streams into a more mature system, the prin- stricted to the upper 100 to 200 feet (33 to cipal drainage system being located in the 67 m) of the Hosston Formation. The transi- northwestern part of the study area. tional deposits grade into the overlying Pet- In general, net-sandstone and isopach tet Formation (Limestone). trends in the Hosston Formation (Figs. 22 and The fluvial facies is composed of con- 23) resemble those of the Cotton Valley glomeratic sandstone and white to light-red, Group. Thickness and net-sandstone values of fine- to medium-grained sandstone; light-gray the Hosston Formation gradually increase ba- to red muddy sandstone; white to pale-red sinward across the subjacent Smackover-Gilmer siltstone; and thin beds of red and grayish- stable carbonate platform. Basinward of the green mudstone. Carbonaceous and lignitic platform, the parallel high-net-sandstone material occurs in some sandstone units. trends and sediment thicks in the Cotton Val- Quartz and pebble conglomerate beds occur ley Group coincide with those of the Hosston throughout the section but are more common Formation. Thickness variations, however, in the lower part of the formation (Bushaw, are not as great within the Hosston, suggest- 1968; Nichols et al., 1968) (Appendix A). ing that most of the Hosston deltaic sedimen- 236 The Jurassic of the Gulf Rim

Figure 16. Stratigraphic cross section C-C' McGowen and Harris/Depositional Systems in the East Texas Basin 237

through Kaufman and Van Zandt Counties 238 The Jurassic of the Gulf Rim 17.D-D'FigureKaufmancrossStratigraphicCountiessectionandthroughZandtVan McGowen and Harris/Depositional Systems in the East Texas Basin 239

Figure 18. Stratigraphic cross section E-E' through Henderson County

tation was basinward of the study area. A flat salt surface. Kehle suggested that mass map showing depositional environments during imbalance, resulting from uneven sediment middle Hosston time indicates a similar trend loading, has greater impact on initial salt (Fig. 8 of Bushaw, 1968). Basinward, the migration than any other mechanism. He at- Hosston Formation increases in thickness from tributed uneven sediment loading to several 800 to 1,350 feet (244 to 412 m) ; the Cotton sedimentary processes, such as reef develop- Valley Group exhibits a similar increase, ment, formation of submarine fans at the base from 1,400 to 5,800 feet (427 to 1,700 m). of a continental slope, and progradation of deltaic and strandline systems. According to Depositional And Structural Model this model, the underlying salt flows laterally away from the sedimentary anomaly, The model selected for use in this study thereby forming an initial withdrawal basin. was proposed by Kehle (1971) to explain the With continued accumulation of sediment, the initiation of salt movement on an originally withdrawal basin enlarges so that salt ridges 240 The Jurassic of the Gulf Rim

Figure 19. Sandstone-percent map of the Cotton Valley Group are formed basinward of the sediment thicks. Bishop (1978) proposed a similar model Lehner (1969) and Martin (1973) documented to explain the emplacement of piercement dia- the presence of analogous features on the pirs. His model emphasized the importance of abyssal plain and lower continental slope in uneven sediment loading but also suggested the northern Gulf of Mexico. additional factors that might contribute to McGowen and Harris/Depositional Systems in the East Texas Basin 241

Figure 20. Net-sandstone map of the Cotton Valley Group

the formation of incipient salt structures; tionship between sedimentation and salt tec- these include regional dip, sedimentation tonics in the western Gulf Basin. He distin- rate, progradation rate, sediment density, guished two main types of sedimentation thickness of overburden, and thickness of the styles and their related salt structures. In underlying salt. the first type, high-constructive lobate del- Fisher (1973) proposed a direct rela- taic systems initiate mobilization of salt 242 The Jurassic of the Gulf Rim

Figure 21. Sandstone-percent map of the Hosston Formation and the salt migrates laterally into inter- ient stages. The second type is closer than deltaic areas, resulting in the formation of the first to the salt structures that are diapirs between the major deltaic lobes. In thought to have formed during deposition of the second type, strike depositional systems the Late Jurassic fan delta system. generally induce broad salt ridges, rather In using these two models to explain how than discrete salt structures, in the incip- Late Jurassic depositional systems effected McGowen and Harris/Depositional Systems in the East Texas Basin 243

Figure 22. Isopach map of the Hosston Formation salt migration, the following sequence of Triassic basins to the west. The Ouachita events is suggested: Reversal of dip along Mountains to the north were low-lying and the rift margin allowed an influx of terrige- thus supplied only a small quantity of terri- nous elastics into the East Texas Basin dur- genous clastic sediment, which was limited ing the Late Jurassic and Early Cretaceous. mostly to the northern periphery of the ba- Before that time, main drainage along the sin. western margins of the basin flowed into the As the supply of terrigenous clastic 244 The Jurassic of the Gulf Rim

Figure 23. Net-sandstone map of the Hosston Formation sediment increased, Cotton Valley and Hosston was a stable platform, and although regional fan-delta systems, which were advancing subsidence occurred, it impeded the formation southward and eastward and were supplied by a of local depocenters. Most likely, the seas braided-stream complex, began prograding over the carbonate platform were shallow and across the Smackover-Gilmer carbonate shelf the rate of progradation of the advancing in the East Texas Basin (Fig. 24) . The shelf deltaic complex was rapid. Low-amplitude McGowen and Harris/Depositional Systems in the East Texas Basin 245

Figure 24. Structural and depositionalmodel of salt migration in the northwestern part of the East Texas Basin during Late Jurassic and Early Cretaceous time salt structures occur under the Smackover- This ridge acted as a dam and thereby en- Gilmer shelf complex, apparently the result hanced the effectiveness of the syncline as a of downward creep that was caused by loading sediment trap. As the Louann Salt became de- of carbonate deposits (Rogers, 1967; Jackson pleted through basinward migration, subsi- and Harris, 1981). These low-amplitude salt dence slowed and allowed aggradation to sur- swells are not evident in the overlying Cot- pass it. Consequently, each subsequent depo- ton Valley-Hosston sediments. center and associated salt ridge shifted ba- Basinward of the ancient Jurassic shelf sinward, resulting in a series of parallel edge, the rate of progradation slowed, while salt ridges and sediment thicks. As the old- subsidence caused by salt migration and in- er salt ridges became buried, continued salt creased water depth allowed the fan delta migration evolved the original salt ridges complex to stack up, forming elongate depo- into separate salt structures, such as salt centers. Salt migrated basinward, forming a anticlines and domes. salt ridge in front of the sediment wedge. Toward the end of Early Cretaceous time, 246 The Jurassic of the Gulf Rim

the volume of terrigenous clastic sediment Therefore, advancing Cotton Valley-Hosston entering the East Texas Basin decreased. The fan deltas spread laterally and basinward, transitional nature of the uppermost Hosston depositing a fairly uniform wedge of sedi- and marine deposits in overlying units indi- ments that gradually thickened basinward. cate that a marine transgression occurred. Mass imbalance became a viable mechanism to initiate salt movement only when the advancing fan deltas prograded basinward of the Conclusions stable carbonate platform. Salt migrated basinward of the prograding sediment wedge, Subsurface mapping of the Cotton Valley forming a proximal incipient withdrawal basin and Hosston depositional systems and subja- and distal salt ridge. Subsequent depocen- cent salt structures leads to four major con- ters and salt ridges shifted basinward, form- clusions regarding the role of basin infil- ing parallel sediment thicks and salt ridges. ling in the initiation of salt movement with- Fourth, parallel salt ridges that formed in the northwestern part of the East Texas during deposition of the Cotton Valley and Basin. Absence of data in the central part Hosston apparently were the initial stage in of the basin, however, precludes delineation the development of salt anticlines and domes. of the basinward extent of the proposed depo- Through continued loading, the salt ridges sitional systems. evolved into discrete salt structures. Domal First, a prograding fan delta system growth appears to depend directly on contin- comprises the Cotton Valley-Hosston strati- ued sediment loading, which occurs during graphic units. The strata between the Gilmer periods of major deltaic deposition where the and Pettet Limestones were deposited during a underlying salt wedge is adequately thick. period of regression that was ended by a major post-Hosston transgression. The transgression is evidenced by transitional shallow marine strata in the upper 100 to 200 feet Acknowledgments (33 to 66 m) of the Hosston Formation and by upward gradation into the overlying Pettet Funding for this study was provided by Limestone. the U. S. Department of Energy under Contract Second, the initial movement of salt No. DE-AC97-80ET46617. Discussions with M. that occurred in the proximal parts of the P. A. Jackson, C. W. Kreitler, J. H. McGowen East Texas Basin during Smackover deposition and S. J. Seni were very helpful. L. F. was the result of downward creep that was in- Brown, Jr., R. J. Finley, W. E. Galloway, M. duced by loading of carbonates and was en- P. A. Jackson, C. W. Kreitler, S. J. Seni, hanced by basinward tilting (Jackson and Har- and Noel Tyler reviewed the manuscript and ris, 1981). The resulting salt movement pro- made many helpful suggestions. Cynthia Lopez duced small salt structures. Relief on the and Keith Pollman served as research assis- salt structures increased basinward, coinci- tants. The report was edited by Jean Trim- dent with thickening of the salt wedge. ble. Word processing was by Dottie Johnson Third, salt mobilized by mass imbalance and Margaret Chastain under the direction of was induced by Cotton Valley and Hosston del- Lucille C. Harrell. Figures were drafted un- taic deposition. Uneven sediment loading was der the direction of Dan F. Scranton by John controlled by the position of the underlying T. Ames, Thomas M. Byrd, Micheline R. Davis, Smackover -Gilmer carbonate shelf. The Smack- Margaret L. Evans, Richard P. Flores, Byron over-Gilmer carbonate shelf comprised a sta- P. Holbert, Jeffrey Horowitz, and Jamie Mc- ble platform that impeded local subsidence Clelland. Camerawork for illustrations was and vertical aggradation of deltaic deposits. by James A. Morgan. McGowen and Harris/Depositional Systems in the East Texas Basin 247

References

Agagu, 0. K., McGowen, M. K., Wood, D. H., generated triple junctions: key indicators Basciano, J. M., and Harris, D. W. , 1980, in applying plate tectonics to old rocks: Regional tectonic framework of the East Journal of Geology, v. 81, no. 4, p. Texas Basin, in Kreitler, C. W. , and oth- 406-433. ers, Geology— and geohydrology of the East Bushaw, D. J., 1968, Environmental synthesis Texas Basin a report on the progress of of the East Texas Lower Cretaceous: Gulf nuclear waste isolation feasibility stud- Coast Association of Geological Societies ies (1979): The University of Texas at Transactions, v. 18, p. 416-438. Austin, Bureau of Economic Geology Geolog- Casey, J. M., 1980, Depositional systems and ical Circular 80-12, p. 11-19. basin evolution of the late Paleozoic Taos Barnes, V. E., 1965, Tyler sheet: University Trough, northern New Mexico: The Univer- of Texas, Austin, Bureau of Economic Geol- sity of Texas at Austin, Texas Petroleum ogy, Geologic Atlas of Texas, scale Research Committee Report No. UT 80-1, 1:250,000. 236 p. 1966, Texarkana sheet: University Dickinson, K. A., 1968, Upper Jurassic strat- of Texas, Austin, Bureau of Economic Geol- igraphy of some adjacent parts of Texas, ogy, Geologic Atlas of Texas, scale Louisiana, and Arkansas: United States 1:250,000. Geological Survey Professional Paper 1972, Dallas sheet: The University 594-E, p. El-E25. of Texas at Austin, Bureau of Economic Eaton, R. W. , 1961, Development and future Geology, Geologic Atlas of Texas, scale possibilities of the Jurassic in northeast 1:250,000. Texas: South Texas Geological Society Pub- Beall, Robert, 1975, Plate tectonics and the lication, 15 p., reprinted in 1964, South origin of the Gulf of Mexico: Gulf Coast Texas Geological Society Bulletin, v. 4, Association of Geological Societies Trans- no. 13, p. 4-13. actions, v. 23, p. 109-114. Erxleben, A. W. , 1975, Depositional systems Bishop, R. S., 1978, Mechanism for emplace- in Canyon Group (Pennsylvania System) , ment of piercement diapirs: American Asso- North-Central Texas: The University of ciation of Geological Societies Bulletin, Texas at Austin, Bureau of Economic Geol- v. 62, no. 9, p. 1561-1583. ogy Report of Investigations No. 82, Boothroyd,- J. C. , 1976, A model for alluvial 75 p. fan fan delta sedimentation in cold-tem- Fisher, W. L., 1973, Deltaic sedimentation, perate environments, in Recent and ancient salt mobilization, and growth faulting in sedimentary environments in Alaska: Alaska Gulf Coast Basin (abs.): American Associa- Geological Society Symposium Proceedings, tion of Petroleum Geologists Bulletin, v. Nl-N3. 54, no. 4, p. 779. , and Ashley, G. M., 1975, Forgotson, J. M., Jr., 1954, Regional strati- Processes, bar morphology, and sedimentary graphic analysis of Cotton Valley Group of structures on braided outwash fans, north- upper Gulf Coastal Plain: American Associ- eastern Gulf of Alaska, in Jopling, A. V. , ation of Petroleum Geologists Bulletin, v. and McDonald, B. C., cd., Glaciofluvial 38, no. 12, p. 2476-2499. and glaciolacustr ine sedimentation: Soci- , and Forgotson, J. M., Jr., ety of Economic Paleontologists and Miner- 1976, Definition of Gilmer Limestone, Up- alogists Special Publication 23, p. 193- per Jurassic formation: American Associa- -222. tion of Petroleum Geologists Bulletin, v. , and Nummedal, Dag, 1978, 60, no. 7, p. 1119-1123. Proglacial braided outwash: a model for Galloway, W. E., 1976, Sediments and strati- humid alluvial-fan deposits, in Miall, A. graphic framework of the Copper River fan D., cd., Fluvial sedimentology: Canadian delta, Alaska: Journal of Sedimentary Pe- Society of Petroleum Geologists Memoir 5, trology, v.46, no. 3, p. 726-737. p. 641-688. , Kreitler, W. W. , and Brown, L. F. , Jr., 1969, Geometry and distri- McGowen, J. H., 1979, Depositional and bution of fluvial and deltaic sandstones ground-water flow systems in the explora- (Pennsylvanian and Permian), North-Central tion for uranium: The University of Texas Texas: Gulf Coast Association of Geologi- at Austin, Bureau of Economic Geology cal Societies Transactions, v. 19, p. 23- Research Colloquium, 1978, 267 p. -47. reprinted in 1969, The University of Hobday, D. K., Woodruff, C. M., Jr., and Texas at Austin, Bureau of Economic Mcßride, M. W. , 1981, Paleotopographic and Geology Geological Circular 69-4, 15 p. structural controls on nonmarine sedimen- Burke, Kevin, and Dewey, J. F., 1973, Plume- tation of the Lower Cretaceous Antlers 248 The Jurassic of the Gulf Rim

Formation and correlatives, north Texas ogy: San Francisco, W. H. Freeman and Co., and southeastern Oklahoma, in Recent and 522 p. ancient nonmarine depositional environ- Loocke, J. E., 1978, Growth history of the ments: models for exploration: Society of Hainesville salt dome, Wood County, Texas: Economic Paleontologists and Mineralogists The University of Texas at Austin, Mas- Special Publication 31, p. 71-87. ter 's thesis, 95 p. Holmes, Arthur, 1965, Principles of physical Lucchi, F. R., Colella, A., Ori, G. G. , and geology (2nd cd.): New York, Roland Press, Oglian, F. , 1981, Pliocene fan deltas of 1288 p. the Intra-Apenninic Basin, Bologna, in Hughes, D. J., 1968, Salt tectonics as relat- Lucchi, F. R. , cd., International Associa- ed to several Smackover fields along the tion of Sedimentologists Excursion Guide- northeast rim of the Gulf of Mexico Basin: book 4, 162 p. Gulf Coast Association of Geological Soci- Lyons, P. L., 1957, Geology and geophysics of eties Transactions, v. 18, p. 320-330. the Gulf of Mexico: Gulf Coast Association Imlay, R. W. , 1943, Jurassic formations of of Geological Societies Transactions, v. the Gulf region: American Association of 7, p. 1-9. Petroleum Geologists Bulletin, v. 27, no. Martin, R. G. , 1973, Salt structure and sedi- 11, p. 1407-1533. ment thickness, Texas-Louisiana continen- Jackson, M. P. A., 1982, Fault tectonics of tal slope, northwestern Gulf of Mexico: the East Texas Basin: The University of U.S. Geological Survey Open-File Report, Texas at Austin, Bureau of Economic Geol- 21 p. ogy Geological Circular 82-4, 31 p. McGowen, J. H. , 1970, Gun Hollow fan delta, , and Harris, D. W. , 1981, Nueces Bay, Texas: The University of Texas ___^ Seismic stratigraphy and salt mobilization at Austin, Bureau of Economic Geology Re- along the northwestern margin of the East port of Investigations No. 69, 91 p. Texas Basin, in Kreitler, C. W. , and oth- , Granata, G. E., and Seni, S. ers, Geology and geohydrology of the East J., 1979, Depositional framework of the Texas Basin: a report of the progress of Lower Dockum Group (Triassic) , Texas Pan- nuclear waste isolation feasibility stud- handle: The University of Texas at Austin, ies. (1980): The University of Texas at Bureau of Economic Geology Report of In- Austin, Bureau of Economic Geology Geolog- vestigations No. 97, 60 p. ical Circular 81-7, p. 28-32. , and Harris, D. W., 1981, Pre- , Seni, S. J., and McGowen, liminary study of the Upper Jurassic (Cot- M~. kT", 1982, initiation of salt flow in ton Valley) and Lower Cretaceous (Hosston- the East Texas Basin (abs.): American /Travis Peak) Formations of the East Texas Association of Petroleum Geologists Bulle- Basin, in Kreitler, C. W. , and others, Ge- tin, v. 66, no. 5, p. 584-585. ology—and geohydrology of the East Texas Johnson, L. C, 1980, Structure and stratig- Basin a report on the progress of nuclear raphy of an evolving salt ridge and basin waste isolation feasibility studies complex, Louisiana continental shelf: The (1980): The University of Texas at Austin, Univ. Tex. at Austin, Mast. Thesis, 120 p. Bureau of Economic Geology Geological Cir- Kaiser, W. R., Johnston, J. E., and Bach, W. cular 81-7, p. 43-47. N., 1978, Sand-body geometry and the oc- Miall, A. D., 1977, A review of the braided- currence of lignite in the Eocene of Tex- river depositional environment, in Earth as: The University of Texas at Austin, Bu- Science Reviews No. 13: Amsterdam, Elsev- reau of Economic Geology Geological Circu- ier Scientific Publishing Co., p. 1-62. lar 78-4, 19 p. Moore, R. W. , and Del Castillo, Luis, 1974, Kehle, R. O., 1971, Origin of the Gulf of Tectonic evolution of the southern Gulf of Mexico: The University of Texas at Austin, Mexico: Geological Society of America Bul- Geology Library, call no. q557K260, unpub- letin, v. 85, no. 4, p. 607-618. lished report, unpaginated. Newkirk, T. F. , 1971, Possible future petro- Krumbein, , Sloss, , 1959, provinces Jurassic, W. C. and L. L. leum of , western Gulf Principles of stratigraphy and sedimenta- Basin, in Cram, I. H. cd., Future—petro- tion: San Francisco, W. H. Freeman and leum provinces of the United States their Co., 497 p. geology and potential: American Associa- Lehner, Peter, 1969, Salt tectonics and tion of Petroleum Geologists Memoir 15, p. Pleistocene stratigraphy on continental 927-953. slope of northern Gulf of Mexico: American Nichols, P. H. , Peterson, G. E., and Wuest- Association of Petroleum Geologists Bulle- ner, C. E., 1968, Summary of subsurface tin, v. 53, no. 12, p. 2431-2482. geology of northeast Texas: American Asso- Leopold, L. 8., Wolman, M. G. , and Miller, J. ciation of Petroleum Geologists Memoir 9, P., 1964, Fluvial Processes in geomorphol- v. 1, p. 982-1004. McGowen and Harris/Depositional Systems in the East Texas Basin 249

Parker, T. J. , and McDowell, A. M., 1955, tion of Petroleum Geologists Memoir 26, p. Model studies of salt dome tectonics: 145-163. American Association of Petroleum Geolo- Trusheim, F. , 1960, Mechanisms of salt migra- gists Bulletin, v. 39, no. 12, p. 2384- tion in northern Germany: American Associ- -2470. — ation of Petroleum Geologists Bulletin, v. Raup, O. 8., 1970, Brine mixing an addition- 44, no. 9, p. 1519-1540. al mechanism for formation of basin evap- Turk, Kehle, and Associates, 1978, Tectonic orites: American Association of Petroleum framework and history, Gulf of Mexico re- Geologists Bulletin, v. 54, no. 12, p. gion: Report for Law Engineering Testing 2246-2259. Co., Marietta, Georgia, 28 p. Rogers, J. X., 1967, Comparison of some Gulf Walker, R. G., and Cant, D. J., 1979, Sandy Coast Mesozoic carbonate shelves: Gulf fluvial systems, in Walker, R. G., cd., Coast Association of Geological Societies Facies models: Geological Association of Transactions, v. 17, p. 49-60. Canada, Geoscience Canada Reprint Series Rosenkrans, R. R., and Marr. J. D., 1967, 1, p. 23-32. Modern seismic exploration of the Gulf Walper, J. L., 1980, Tectonic evolution of Coast Smackover trend: Geophysics, v. 32, the Gulf of Mexico, in Pilger, R. H. , Jr., no. 2, p. 184-206. - cd., The origin of the Gulf of Mexico and Rust, B. R., 1978, Depositional models for the early opening of the central North At- braided alluvium, in Miall, A. D. , cd., es lantic Ocean: Louisiana State University Fluvial sedimentology: Canadian Society of Symposium Proceedings, Baton Rouge, 1980, Petroleum Geologists Memoir 5, p. 605- p. 87-98. -626. Ward, L. G., Stephen, M. F. , and Nummedal, Salvador, Amos, and Green, A. R. , 1980, Open- Dag, 1976, Hydraulics and morphology of ing of the Caribbean Tethys (origin and glacial outwash distributaries, Skeidarar- development of the Caribbean and the Gulf isandur, Iceland: Journal of Sedimentary of Mexico), in Collogue C5: Geologic de Petrology, v. 46, no. 4, p. 770-777. chaines alpines issues de la Tethys: Bu- Wescott, W. A., and Ethridge, F. G., 1980, reau de Recherches Geologiques et Minieres Fan-delta— sedimentology and tectonic set- Memoire 115, p. 224-229. ting Yallahs fan delta, southeast Jamai- Swain, F. M., 1949, Upper Jurassic of north- ca: American Association of Petroleum Ge- eastern Texas: American Association of Pe- ologists Bulletin, v. 64, no. 3, p. 374- troleum Geologists Bulletin, v. 33, no. -400. 7, p. 1206-1250. Wood, D. H., 1981, Structural effects of salt Thomas, W. A., and Mann, C. J., 1966, Late movement in the East Texas Basin, in Jurassic depositional environments, Lou- Kreitler, C. W. , and others, Geology —and isiana and Arkansas: American Association geohydrology of the East Texas Basin a of Petroleum Geologists Bulletin, v. 50, report on the progress of nuclear waste no. 1, p. 178-182. isolation feasibility studies: The Univer- Todd, R. G., and Mitchum, R. M., Jr., 1977, sity of Texas at Austin, Bureau of Eco- Seismic stratigraphy and global changes of nomic Geology Geological Circular 81-7, p. sea level, part 8: identification of Upper 21-27. Triassic, Jurassic, and Lower Cretaceous Wood, M. L., and Walper, J. L., 1974, The sequences seismic in Gulf of Mexico and, evolution of the interior western basins offshore West Africa, in— Payton, C. E. and the Gulf of Mexico: Gulf Coast Associ- cd. , Seismic stratigraphy applications to ation of Geological Societies Transac- hydrocarbon exploration: American Associa- tions, v. 24, p. 31-41. 250 The Jurassic of the Gulf Rim

Appendix A

Electric log tracings and descriptions of rotary well cuttings (refer to Fig. 2 for location). McGowen and Harris/Depositional Systems in the East Texas Basin 251

- Appendix A Continued 252 The Jurassic of the Gulf Rim

- APPENDIX A Continued McGowen and Harris/Depositional Systems in the East Texas Basin 253

Appendix B

Cross-section wells

Well No. Well Name County

Line A-A1 A-1 LZ 17-43-701 Humble Oil & Refining Co. No. 1 Dunham Hopkins A-2 LZ 17-59-201 Sunray Dx Oil Co. No. 1 Seaman Hopkins A-3 LZ 17-59-301 North Central Oil Co. No. 1 Moseley Hopkins A-4 LZ 17-59-901 Hinton No. 1 Walker Hopkins A-5 ZS 34-04-203 Forest Oil Corp. No. 1 Asher Hopkins A-6 ZS 34-04-502 Hughley Operating Co. and No. Am. Expl. Co. Wood A-7 ZS 34-04-601 Humble Oil & Refining Co. No. 1 Allen Wood A-8 ZS 34-12-301 Getty Oil No. 1 Blalock Wood A-9 ZS 34-12-303 Shell Oil Co. No. 1 Wright Wood

Line B-B1 B-1 PH 33-08-204 Ohio Oil Co. No. 1 Popper Hunt B-2 UK 34-10-302 Texaco, Inc. Irvine Gas Unit No. 1 Rains B-3 UK 34-10-601 Delta Drilling No. 1 Hare Rains B-4 UK 34-11-905 Caraway & Smith No. 1 Gilley Rains B-5 ZS 34-12-701 Samedan Oil Corp. Buchanan No. 1 Wood B-6 ZS 34-23-701 Humble Oil & Refining Co. NW Hawkin No. 1 Wood

Line C-C C-1 RA 33-15-603 Schneider and Murray No. 1 Jones Estate Kaufman C-2 RA 33-16-106 Santa Fe Minerals, Inc. No. 1 Barrow Estate Kaufman C-3 YS 34-09-802 E. C. Johnston Co. No. 1 Martin Gas Unit Van Zandt C-4 YS 34-18-408 Pan American Petr. Corp. Brown Gas Unit B-1 Van Zandt C-5 YS 34-18-406 Pan American Petr. Corp. No.l Nichols Gas U. Van Zandt C-6 YS 34-18-202 Caraway and Smith Parker Gas Unit No. 2 Van Zandt C-7 YS 34-18-522 R. J. Caraway No. 1 Stone (Fruitvale GU) Van Zandt C-8 YS 34-18-623 Continental Oil Co. No. 1 Elliot Van Zandt C-9 YS 34-27-501 Halbouty No. 1 Rowan Van Zandt C-10 YS 34-27-602 Midwest et al. No. 1 Clark Van Zandt C-11 YS 34-27-903 Pure Oil Co. D-8 Swain No. 11 Van Zandt

Line D-D 1 D-1 RA 33-14-801 Rockwall Exploration Co. No. 1 Wallace Kaufman D-2 RA 33-23-702 W. M. Hughes No. 1 Billings Kaufman D-3 RA 33-23-502 The T x 1 Oil Corp. No. 1 Liston Kaufman D-4 RA 33-23-902 Southland Royalty Co. No. 1 Frosch Unit Kaufman D-5 RA 33-32-104 Union Tex. Pet.-Lacal Pet. No. 1 Phillips Kaufman D-6 YS 34-25-501 R. J. Caraway No. 1 Yates Van Zandt D-7 YS 34-25-302 Superior Oil Co. No. 1 Porter Van Zandt D-8 YS 34-25-601 R. J. Caraway No. 1 Parker Van Zandt D-9 YS 34-26-801 R. J. Caraway No. 1 Gilmore Van Zandt D-10 YS 34-36-402 Pan American Petr. Corp. No. 1 Hobbs Van Zandt

Line E-E 1 E-1 TV 33-55-101 Humble Oil & Refining Co. Navarro E-2 LT 33-47-0-1 Max Pray No. 1 Carter Henderson E-3 LT 33-48-801 Pan American Petr. Corp. No. 1 Sorrell Henderson E-4 LT 33-48-803 Rudman Resources, Inc. No. 1 Hammock Henderson E-5 LT 34-41-702 Lake Ronel Oil Co.-Bill Ross No. 1 Shaver Henderson E-6 LT 34-42-702 B. Smith, G. Lehnertz, W. Perryman No. 1 Lee Henderson E-7 LT 34-43-801 Lone Star Producing Co. 1-B Allyn Henderson E-8 LT 3 4-57-301 Texas Interstate Oil & Gas Co. No. 1 Cotton Henderson