The Arcadia Park Shale is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

within the

Eagle Ford Group The Eagle Ford Group (also called the Eagle Ford Shale) is a Sedimentary rock, sedimentary rock formation deposited during the Cenomanian and Turonian ages of the Late Cretaceous over much of the modern-day state of Texas. The Eagle Ford is pr ...

that

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial ...

s in the northern portion of

East Texas East Texas is a broadly defined cultural, geographic, and ecological region in the eastern part of the U.S. state of Texas that comprises most of 41 counties. It is primarily divided into Northeast and Southeast Texas. Most of the region consi ...

. It was deposited during the Middle to Late

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by t ...

of the Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

.Denne, R. A., Breyer, J. A., Callender, A. D., Hinote, R. E., Kariminia, M., Kosanke, T. H., Kita, Z., Lees, J. A., Rowe, H., Spaw, J. M., and Tur, N. (2016) Biostratigraphic and geochemical constraints on the stratigraphy and depositional environments of the Eagle Ford and Woodbine Groups of Texas: ''in'' Breyer, J. A. (ed.), The Eagle Ford Shale: A renaissance in U.S. oil production, AAPG Memoir 110, p. 1-86. It was originally described by W. L. Moreman from

s near the former Arcadia Park railway station west of downtown

Dallas Dallas () is the List of municipalities in Texas, third largest city in Texas and the largest city in the Dallas–Fort Worth metroplex, the List of metropolitan statistical areas, fourth-largest metropolitan area in the United States at 7.5 ...

, where it is 100 ft (30 m) thick. In the type area there is an

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

between the Arcadia Park and the underlying

Britton Formation The Britton Formation is a geologic formation deposited during the Middle Cenomanian to the Early Turonian ages of the Late Cretaceous in modern-day East Texas. It forms the lower half of the Eagle Ford Group in the northern portion of East Texa ...

. The base of the Arcadia Park is a thin

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

termed the

Kamp Ranch Limestone The Kamp Ranch Limestone is a geologic formation in Dallas County, Texas. It preserves fossils dating back to the Cretaceous period. The most notable is ''Dallasaurus'', a squamate that was the first of the aquatic mosasaurs. See also * List of ...

. The

is made up of broken pieces (prisms) of ''

Inoceramus ''Inoceramus'' (Greek: translation "strong pot") is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus '' Pteria''. They lived from the Early Jurassic ...

'' clams, and also contains

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

's teeth. The remainder of the Arcadia Park in the

area is

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

with

concretion A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular ...

Sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s are found within the Arcadia Park north of

. The

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s have been termed the Bells Sandstone Member for

s in Grayson County, and the Sub-Clarksville Sandstone in the subsurface. The shale overlying the Bells Sandstone has been named the Maribel Shale

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s that occur in the Arcadia Park include

's teeth and other

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

remains,

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

inoceramid The Inoceramidae are an extinct family of bivalves ("clams") in the Class Mollusca. Fossils of inoceramids are found in marine sediments of Permian to latest Cretaceous in age. Inoceramids tended to live in upper bathyal and neritic environment ...

clams,

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not al ...

s, and

foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular Ectoplasm (cell biology), ectoplasm for catching food and ot ...

. The Sub-Clarksville Sandstone is a conventional source of

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

production in

.Wood, D. H., and A. B Giles (1982) Hydrocarbon accumulation patterns in the East Texas salt dome province: Bureau of Economic Geology Geological Circular 82-6, 36 p.

References

{{Clear Shale formations of the United States Cretaceous geology of Texas Turonian Stage