Changes in floral composition with depositional environment in Texas Eocene Manning Formation lignites
The floral composition of palynomorph assemblages of Jacksonian Texas lignites is closely linked to depositional systems. Localities on the eastern Gulf coastal plain are included in the late Eocene Fayette delta system, and lignite formation is considered to have occurred in lower deltaic environments. Samples are commonly dominated by grains of Caprifoliipites/Salixpollenites, Momites, or Nyssa, indicating dicotyledonous tree-dominated swamps. Some samples contain abundant Cicatricosspories spores, suggesting marshy, fern-dominated areas. The San Miguel lignite deposit in McMullen County is located on the eastern margin of the south Texas strand-plain/barrier-bar system. Caprifoliipites/Salixpollenites pollen is rare in the San Miguel, and most of the levels are dominated by small tricolporates such as cupuliferoipollenites and Sapotaceae. Nyssa is locally important. The lignite is considered to have been deposited in a nondeltaic freshwater swamp behind a barrier island. The Miguel Alleman deposit, across the Mexican border in Tamaulipas, is thought to have developed in a lagoonal-estuarine environment. Dinoflagellates such as Wetzeliella are common at some levels, indicating marine conditions. As with San Miguel, small tricolporates and Momipites are common. These assemblages contrast with Sabinian floras. Wilcox Group east Texas lignites were formed in fluvial environments. Betulaceous pollen is common in these coals. Sabinian south Texas lignites formed in marine environments yield dinoflagellates and Chenopodium-type pollen. Chenopods are common in present-day Gulf Coast salt marshes but seem to have been absent from Jackson-age seacoasts.
- Research Organization:
- Texas A and M Univ., College Station
- OSTI ID:
- 6889683
- Report Number(s):
- CONF-8610199-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 70:9; Conference: 36. annual meeting of the Gulf Coast Association Geological Societies and the Gulf Coast Section of SEPM, Baton Rouge, LA, USA, 22 Oct 1986
- Country of Publication:
- United States
- Language:
- English
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