A Regional Geological and Geophysical Study of the Delaware Basin, New Mexico and West Texas G
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New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/31 A regional geological and geophysical study of the Delaware Basin, New Mexico and west Texas G. Randy Keller, J. M. Hills, and Rabah Djeddi, 1980, pp. 105-111 in: Trans Pecos Region (West Texas), Dickerson, P. W.; Hoffer, J. M.; Callender, J. F.; [eds.], New Mexico Geological Society 31st Annual Fall Field Conference Guidebook, 308 p. This is one of many related papers that were included in the 1980 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. 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The rifting extended north- The Permian Basin (fig. 1) is one of the major hydrocarbon pro- ward to northern Lea County, New Mexico and was accompanied ducing regions of North America. In addition, it is a tectonic by right-lateral faulting along a north-northwest trend. Some ver- feature which has played a key role in the geologic history of the tical movements also may have taken place at this time as the southwest. In this study, regional geological and geophysical data western part of the basin probably formed an aulacogen. have been collected and synthesized in the hope of obtaining a However, most of the history just given is highly speculative. The better understanding of the geologic history and deep structure of real evidence is the nearly vertical attitude of many of the deep- the Permian Basin area. Our main area of interest was the Dela- seated faults on the west side of the basin pointing to a strike-slip ware Basin and its boundary with the Central Basin Platform. origin, the gravity and magnetic evidence for a major upper crustal anomaly, and the sparse data from well borings to the Precam- GEOLOGIC SETTING AND TECTONIC HISTORY brian which show extensive volcanic terranes overlying plutonic The Permian Basin of West Texas and New Mexico seems to and metamorphic rocks. have originated in late Proterozoic time as a low spot on the Following a long interval of uplift and erosion during latest Pre- southwestern edge of the North American craton. At this time, a cambrian and Early Cambrian time, a thin veneer of Upper Cam- portion of the province may have been affected by crustal rifting brian and basal Ordovician clastics were deposited in the shallow originating in a triple junction spreading center located con- Tobosa Basin of Galley (1958). Throughout early and middle Paleozoic time, this basin, which covered the study area, was the site of shallow-water deposition, largely limestones and shales. • ,Ea MALL This sedimentation was interrupted frequently by intervals of MEP • CASTRO widespread emergence and subaerial erosion. F1.0 0 0 In Mississippian time mild tectonic activity began, accompanied by vertical movement along the zones of weakness inherited from _11■1■00 OR late Precambrian lateral faulting. By Middle Pennsylvanian time, these forces had intensified and deformed the central part of the CAvE S Tobosa Basin into a low folded and faulted mountainous tract. N This feature divided the province into two sub-basins, the Dela- ware on the west and the Midland on the east (fig. 1). As these basins were forming, broad limestone shelves grew around them. They were cut by stream channels through which fine sands and shales were carried into the basins. By late Early Per- mian (Wolfcamp) time these limestones had not only covered the shelves but also the eroded roots of the central mountains, thus forming the Central Basin Platform. At the same time, clastic sedi- mentation continued in the basins on either side of the platform. Vertical movement continued along the faulted Precambrian line of weakness which now formed the eastern side of the rapidly RoOSP deepening Delaware Basin. Similar deepening occurred on a lesser PABLO PLATFORM scale in the Midland Basin. By Middle Permian time the growth of shelf-edge carbonates and a slight eustatic lowering of sea level led to the formation of back-reef evaporites. This process con- tinued throughout the Permian with increased intensity, inter- rupted only by a marine flood in San Andres time. By Late Permian time, carbonate deposition was limited to a nar- row band around the Delaware Basin formed by the high barrier of vs, the Capitan reef complex. The central part of the basin continued to receive limited amounts of fine clastic material which was deposited in a reducing environment. By the end of the period, continuing retreat of the seas resulted in deposition of evaporites and continental red beds over the entire basin. During Middle and Late Permian time, tectonic activity was minimal, being limited to Figure 1. Index map of the study area showing location of the geo- gradual deepening of the Delaware Basin with slight tilting to the logic cross-section. east. 106 KELLER, HILLS and DJEDDI After an interval, continental deposition resumed in the Late Tri- Density Delaware Density Density entral Basin Density Value assic in much the same location as in the Permian. However, fol- System Series :asin Gr./F Unit Value Pltfm. GriF Unit QUATERNARY Holocene Holocene Sand Holocene Sand lowing a hiatus representing Jurassic time, Cretaceous deposition TERTIARY Pliocene Ogallala Ogallala Gultion began on a different pattern, with shallow seas advancing from the CRETACEOUS COmanchean VII 2.55 southeast and depositing marine sandstones and limestones over JURASSIC Absent //// //// TRIASSIC Doc kurn °oakum the area. The Cretaceous beds which have survived erosion are e . Rustler Rustler Ochoa largely all of Comanchean age. VII 2.4 Salado The Laramide orogeny seems to have strongly affected only the Castile VI 277 VI 2.77 Tansill western edge of the basin where Permian shelf-edge carbonates Bell Conyon votes merry Seven PERMIAN and adjacent basinal rocks were uplifted. Downfaulting, both con- Guadalupe V 2.69 temporaneous and later, formed the Salt Basin graben. These V 2.55 movements tilted the Delaware Basin even more strongly to the Victoria Pe k Leonard Bone Spring s. east and formed the Guadalupe and Delaware Mountains. An IV 2.73 Woltcamp woltcamp 2.58 important side effect of this renewed tilting was the opening of 0 .. • , joints about the zone of weakness along the eastern side of the Vi • I A Missouri Con on r A Delaware Basin. This greatly facilitated the solution of large PENNSYLVANIAN D., m.,.. MOM amounts of Permian salt during the Pliocene and Pleistocene. Atoka Atoka Morrow Morro ENIPME III 2.52 Late Cenozoic sediments in the basin are generally thin except mum III 2.52 r A Chester for those filling the Salt Basin graben, solution trenches along the Merornec Pecos River, and the east side of the Delaware Basin. Tectonic MISSISSIPPI AN 0,09. Kinderhook movement during this time has been minimal although slight seis- Upper Mil DEVONIAN Middle mic activity continues. Lower Devonian Lower Deyoni Silurianuan Sh. Sllu on Sh SILURIAN Middle Fus m•n Fu m II 2.70 GEOLOGICAL STUDIES Upper Montoya Montoya Middle Sim son I son ORDOVICIAN The Permian Basin area has been the focus of geological investi- Lower El enburger I 2BI Ellenburger I 281 gation since G. G. Shumard first collected Permian fossils at the CAMBRIAN Upper Cambrian Cambrian 5 base of El Capitan nearly 130 years ago. The discovery of oil in the PRE - CAMBRIAN Pre-Cambrian Pre Cambrian basin in the 1920s intensified the interest in the geology of the Figure 2. Generalized stratigraphic column of West Texas and province and led to the drilling of thousands of wells in the basin. southeastern New Mexico. After T. Jones (1965) and I. M. Hills Records have been kept of most of these borings and each has J.