Earth:Blackwater Draw Formation
| Blackwater Draw Formation Stratigraphic range: Pleistocene 1.8–0.3 Ma | |
|---|---|
| Type | Formation |
| Overlies | Ogallala Formation |
| Area | Over 100,000 km2 |
| Thickness | 27 meters (89 ft) |
| Lithology | |
| Primary | Sandstone |
| Location | |
| Coordinates | [ ⚑ ] 33°35′38″N 101°50′28″W / 33.594°N 101.841°W |
| Region | New Mexico Texas |
| Country | United States |
| Type section | |
| Named for | Blackwater Draw |
| Named by | C.C. Reeves |
| Year defined | 1976 |
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The Blackwater Draw Formation is a geologic formation in the southern High Plains of eastern New Mexico and Texas .[1] The formation was deposited between 1.8 million (Ma) and 300,000 years ago, corresponding to the early to middle Pleistocene epoch.[2]
Description
The formation is a very fine to fine red aeolian sandstone that rests on the resistant caprock calcrete of the Ogallala Formation. The formation is highly variable, but has a maximum thickness of 27 meters (89 ft).[2] The sediments generally are less coarse to the northeast, indicating that they had their source in the Pecos River valley.[3]
The formation is interpreted as loess deposition on a grassland.[2] Deposition was likely episodic, with peak deposition at times of more arid climate and soil formation during moister periods.[3][4]
The lower part of the formation contains an ash bed of the Toledo eruption in the Jemez Mountains[3] 1.61 million years ago (Ma). The formation also contains the 0.62 Ma Lava Creek B ash bed.[3] The upper part of the formation has an infrared stimulated luminescence (IRSL) age of 300 to 350 thousand years (ka), corresponding to the middle Pleistocene epoch.[2]
Fossils
Rhizoliths are locally abundant in paleosol beds and show features characteristic of small plants such as grasses.[4]
History of investigation
The unit was first investigated by John C. Frye and A. Byron Leonard in 1957, who named it the "Cover Sands".[1] The unit was formally named the Blackwater Draw Formation by C.C. Reeves, Jr., in 1976.[5]
See also
- List of fossiliferous stratigraphic units in New Mexico
- Paleontology in New Mexico
Footnotes
- ↑ 1.0 1.1 Frye & Leonard 1957, pp. 28-31.
- ↑ 2.0 2.1 2.2 2.3 Hall & Goble 2020, p. 31.
- ↑ 3.0 3.1 3.2 3.3 Holliday 1989.
- ↑ 4.0 4.1 Gustavson & Holliday 1999.
- ↑ Reeves 1976.
References
- Frye, John C.; Leonard, A. Byron (November 1957). "Studies of Cenozoic geology along eastern margins of Texas High Plains, Armstrong to Howard Counties". Texas Bureau of Economic Geology Report of Investigations 32: 28–31. https://scholar.google.com/scholar_url?url=https://repositories.lib.utexas.edu/bitstream/handle/2152/77828/txu-oclc-2582525.pdf%3Fsequence%3D1&hl=en&sa=T&oi=gsb-ggp&ct=res&cd=0&d=4027618880112333460&ei=RmlOX9vtJc20ywS74YjQDw&scisig=AAGBfm1wwDijKsGRMpRNPoUTL-W1nDlFqA. Retrieved 1 September 2020.
- Gustavson, T. C.; Holliday, V. T. (1 May 1999). "Eolian sedimentation and soil development on a semiarid to subhumid grassland, Tertiary Ogallala and Quaternary Blackwater Draw formations, Texas and New Mexico High Plains". Journal of Sedimentary Research 69 (3): 622–634. doi:10.2110/jsr.69.622.
- Hall, Stephen A.; Goble, Ronald J. (Spring 2020). "Middle Pleistocene IRSL age of the upper Blackwater Draw Formation, Southern High Plains, Texas and New Mexico, USA". New Mexico Geology 42 (1): 31–38. https://geoinfo.nmt.edu/publications/periodicals/nmg/42/n1/nmg_v42_n1.pdf. Retrieved 1 September 2020.
- Holliday, Vance T. (1 June 1988). "Mt. Blanco revisited: Soil-geomorphic implications for the ages of the upper Cenozoic Blanco and Blackwater Draw Formations". Geology 16 (6): 505–508. doi:10.1130/0091-7613(1988)016<0505:MBRSGI>2.3.CO;2.
- Holliday, Vance T. (1 December 1989). "The Blackwater Draw Formation (Quaternary): A 1-4-plus-m.y. record of eolian sedimentation and soil formation on the Southern High Plains". GSA Bulletin 101 (12): 1598–1607. doi:10.1130/0016-7606(1989)101<1598:TBDFQA>2.3.CO;2.
- Reeves, C.C. Jr. (1976). "Quaternary stratigraphy and geologic history of the southern High Plains, Texas and New Mexico". in Mahaney, W.C.. Quaternary stratigraphy of North America. Stroudsburg, Pennsylvania: Dowden, Hutchinson, and Ross, Inc.. pp. 213–234.
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