Wilcox Group

Last updated
Wilcox Group
Stratigraphic range: Selandian-Ypresian
~60–48  Ma
Type Geologic group
Unit of Gulf of Mexico Basin
Sub-units Calvert Bluff, Simsboro & Hooper Formations (Texas)
Nanafalia, Hatchetigbee Formation (Alabama)
Underlies Claiborne Group
Overlies Midway Group
Thicknessup to 1,800 ft (550 m)
Lithology
Primary Mudstone, sandstone, lignite
Other Siltstone
Location
Location Gulf Coast and Mississippi Embayment
Coordinates 30°25′N96°24′W / 30.417°N 96.400°W / 30.417; -96.400
Region Gulf Coast and Mississippi Embayment
Country United States and Mexico
Extent Florida to Tamaulipas
Type section
Named for Wilcox County, Alabama
Locationnot designated
Wilcox Group - stratigraphy Arkansas, Louisiana, Mississippian and Alabama stratigraphic column.png
Wilcox Group - stratigraphy

The Wilcox Group is an important geologic group in the Gulf of Mexico Basin and surrounding onshore areas from Mexico and Texas to Louisiana and Alabama. The group ranges in age from Paleocene to Eocene and is in Texas subdivided into the Calvert Bluff, Simsboro and Hooper Formations, [1] and in Alabama into the Nanafalia and Hatchetigbee Formations. [2] [3] Other subdivisions are the Lower, Middle and Upper Wilcox Subgroups, and the Carrizo and Indio Formations. [4]

Contents

Lithologies

The group comprises mostly mudstone with secondary sandstone and lignite beds, ironstone concretions, [1] as well as siltstones, conglomerates and limestones. [5] The total thickness is about 1,400 to 1,800 feet (430 to 550 m). [1]

Provenance of sandstones

Sandstone modal compositions and detrital zircon U‐Pb analyses of the Wilcox Group indicate long‐distance sediment transport from primarily volcanic and basement sources to the west, northwest, and southwest. The Wilcox Group represents the earliest series of major post‐Cretaceous pulses of sand deposition along the western margin of the Gulf of Mexico. Laramide basement uplifts have long been held to be the source of Wilcox sediments, implying that initiation of basement uplift was the driving factor for the transition from carbonate sedimentation to clastic deposition. Zircon age‐spectra for the sandstones of the Wilcox Group reveal a complex grain assemblage derived from Laramide uplifted crystalline blocks of the central and southern Rocky Mountains, the Cordilleran arc of western North America, and arc‐related extrusive and intrusive igneous rocks of northern Mexico.

Zircon ages also suggest possible recycling of older sediment through uplift related to accretion of arc terranes along the westernmost North America, but that recycling of Cordilleran foreland basin sediments was not a major contributor. Comparison of Upper and Lower Wilcox zircon age-spectra indicate that Lower Wilcox sediments are richer in arc and volcanic material, whereas Upper Wilcox sediments are richer in basement material. Regional trends in detrital zircon age‐spectra indicate that Upper Wilcox sediments are moderately homogeneous over the region studied, whereas the Lower Wilcox shows significant heterogeneity. The drainage area for the Gulf of Mexico during the Paleocene and Eocene was larger than previously thought, encompassing not only the Laramide basement uplifts, but the volcanic province of northern Mexico and possibly Cordilleran tectonic regions along the westernmost North America. [6]

Petroleum geology

The Wilcox Group comprises important source and reservoir rocks in the Gulf of Mexico Basin. [7] Structural and geochemical evidence indicates that hydrocarbons found in Wilcox reservoirs such as the Wilds sandstones were emplaced by vertical migration along wrench faults and associated fracture zones from underlying Cretaceous and Jurassic source rocks. [8]

See also

Related Research Articles

<span class="mw-page-title-main">Chinle Formation</span> Geological formation in the western US

The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In New Mexico, it is often raised to the status of a geological group, the Chinle Group. Some authors have controversially considered the Chinle to be synonymous to the Dockum Group of eastern Colorado and New Mexico, western Texas, the Oklahoma panhandle, and southwestern Kansas. The Chinle Formation is part of the Colorado Plateau, Basin and Range, and the southern section of the Interior Plains. A probable separate depositional basin within the Chinle is found in northwestern Colorado and northeastern Utah. The southern portion of the Chinle reaches a maximum thickness of a little over 520 meters (1,710 ft). Typically, the Chinle rests unconformably on the Moenkopi Formation.

<span class="mw-page-title-main">San Juan Basin</span> Structural basin in the Southwestern United States

The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah and Arizona. Specifically, the basin occupies space in the San Juan, Rio Arriba, Sandoval, and McKinley counties in New Mexico, and La Plata and Archuleta counties in Colorado. The basin extends roughly 100 miles (160 km) N-S and 90 miles (140 km) E-W.

<span class="mw-page-title-main">Haynesville Shale</span>

The Haynesville Shale is an informal, popular name for a Jurassic Period rock formation that underlies large parts of southwestern Arkansas, northwest Louisiana, and East Texas. It lies at depths of 10,500 to 13,000 feet below the land’s surface. It is part of a large rock formation which is known by geologists as the Haynesville Formation. The Haynesville Shale underlies an area of about 9,000 square miles and averages about 200 to 300 feet thick. The Haynesville Shale is overlain by sandstone of the Cotton Valley Group and underlain by limestone of the Smackover Formation.

<span class="mw-page-title-main">Coyote Mountains</span> Mountain range in California, United States

The Coyote Mountains are a small mountain range in San Diego and Imperial Counties in southern California. The Coyotes form a narrow ESE trending 2 mi (3.2 km) wide range with a length of about 12 mi (19 km). The southeast end turns and forms a 2 mi (3.2 km) north trending "hook". The highest point is Carrizo Mountain on the northeast end with an elevation of 2,408 feet (734 m). Mine Peak at the northwest end of the range has an elevation of 1,850 ft (560 m). Coyote Wash along I-8 along the southeast margin of the range is 100 to 300 feet in elevation. Plaster City lies in the Yuha Desert about 5.5 mi (8.9 km) east of the east end of the range.

<span class="mw-page-title-main">Paleontology in Louisiana</span>

Paleontology in Louisiana refers to paleontological research occurring within or conducted by people from the U.S. state of Louisiana. Outcrops of fossil-bearing sediments and sedimentary rocks within Louisiana are quite rare. In part, this is because Louisiana’s semi-humid climate results in the rapid weathering and erosion of any exposures and the growth of thick vegetation that conceal any fossil-bearing strata. In addition, Holocene alluvial sediments left behind by rivers like the Mississippi, Red, and Ouachita, as well as marsh deposits, cover about 55% of Louisiana and deeply bury local fossiliferous strata.

The Hatchetigbee Bluff Formation is a geologic formation in Alabama, Georgia, Louisiana and Mississippi. The youngest unit of the Wilcox Group preserves fossils dating back to the Ypresian stage of the Eocene period, or Wasatchian in the NALMA classification. The formation is named for Hatchetigbee Bluff on the Tombigbee River, Washington County, Alabama.

<span class="mw-page-title-main">Wasatch Formation</span> Geologic formation in the western United States

The Wasatch Formation (Tw) is an extensive highly fossiliferous geologic formation stretching across several basins in Idaho, Montana Wyoming, Utah and western Colorado. It preserves fossils dating back to the Early Eocene period. The formation defines the Wasatchian or Lostcabinian, a period of time used within the NALMA classification, but the formation ranges in age from the Clarkforkian to Bridgerian.

The Hoback Formation is a geologic formation in west-central Wyoming, located within the Hoback Basin. It formed as a result of increased sedimentation rates from the Laramide Orogeny and preserves fossils dating back to the late Paleogene period, through the early Eocene.

The Poison Canyon Formation is a geologic formation in the Raton Basin of Colorado and New Mexico. The formation was deposited from the late Cretaceous through the Paleocene.

The Cub Mountain Formation is a geologic formation in southern New Mexico. It preserves fossils dating back to the Eocene epoch. The formation also records the progressive unroofing of nearby mountainous uplifts during the Laramide orogeny.

<span class="mw-page-title-main">Galisteo Formation</span> A geologic formation in New Mexico

The Galisteo Formation is a geologic formation in New Mexico. It contains fossils characteristic of the Bartonian stage of the Eocene epoch, Duchesnean in the NALMA classification.

The Palm Park Formation is a geologic formation in southern New Mexico. It preserves fossils dating back to the Eocene epoch.

The Bisbee Group is a geologic group in Arizona, Mexico, and New Mexico. It preserves fossils dating back to the early Cretaceous period.

The geology of Mississippi includes some deep igneous and metamorphic crystalline basement rocks from the Precambrian known only from boreholes in the north, as well as sedimentary sequences from the Paleozoic. The region long experienced shallow marine conditions during the tectonic evolutions of the Mesozoic and Cenozoic, as coastal plain sediments accumulated up to 45,000 feet thick, including limestone, dolomite, marl, anhydrite and sandstone layers, with some oil and gas occurrences and the remnants of Cretaceous volcanic activity in some locations.

<span class="mw-page-title-main">Geology of Wyoming</span> Overview of the geology of Wyoming

The geology of Wyoming includes some of the oldest Archean rocks in North America, overlain by thick marine and terrestrial sediments formed during the Paleozoic, Mesozoic and Cenozoic, including oil, gas and coal deposits. Throughout its geologic history, Wyoming has been uplifted several times during the formation of the Rocky Mountains, which produced complicated faulting that traps hydrocarbons.

<span class="mw-page-title-main">Geology of Colorado</span> Geology of the U.S. State of Colorado

The bedrock under the U.S. State of Colorado was assembled from island arcs accreted onto the edge of the ancient Wyoming Craton. The Sonoma orogeny uplifted the ancestral Rocky Mountains in parallel with the diversification of multicellular life. Shallow seas covered the regions, followed by the uplift current Rocky Mountains and intense volcanic activity. Colorado has thick sedimentary sequences with oil, gas and coal deposits, as well as base metals and other minerals.

<span class="mw-page-title-main">Diamond Tail Formation</span> A geologic formation in New Mexico

The Diamond Tail Formation is a geologic formation in New Mexico. It contains fossils characteristic of the late Paleocene or early Eocene.

<span class="mw-page-title-main">El Rito Formation</span> A geologic formation in New Mexico

The El Rito Formation is a geologic formation in New Mexico dating to the Eocene epoch. It records a time when sediments were trapped in deep basins in western North America rather than being carried downstream to the Gulf of Mexico, so that sediments of this age in the western Gulf are mostly from the Appalachian Mountains.

The Love Ranch Formation is a geologic formation in southern New Mexico. It was likely deposited during the late Paleocene and early Eocene epochs.

California River is the name of a northeastward flowing river system that existed in the Cretaceous-Eocene in the western United States. It is so named because it flowed from the Mojave region of California to the Uinta Basin of Utah, transporting sediments along this track towards Lake Uinta.

References

Further reading