2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 13
Presentation Time: 11:30 AM

A Latest Holocene (4500 yr B.P. to Present) Paleovegetational Record (Pollen and Phytolith) from Catahoula Lake, Louisiana

TEDFORD, Rebecca Ann, Department of Geology and Geophysics, Louisiana State University, Howe-Russell Geoscience Complex, Baton Rouge, LA 70803 and WARNY, Sophie, Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, rtedfo1@lsu.edu

Two radiocarbon-dated sediment cores from Catahoula Lake, located along the western edge of the Lower Mississippi River valley of central Louisiana, provide sedimentological and palynological evidences for dynamic changes in lacustrine hydrology and vegetation during the last ~4,500 years B.P.

The transitional period from the end of the Hypsithermal into the establishment of modern cooler, moist conditions (~4,500 to 3,700 yrs B.P.) is documented in Catahoula Lake with pollen assemblages that are characteristic of mixed bottomland hardwood forest (i.e. Quercus spp., Carya aquatica and Pinus sp.) and swamp forest (i.e. Nyssa aquatica, Liquidambar stryaciflua, and Taxodium distichium).

At 3,500 to 2,000 years B.P., pollen assemblages are indicative of relatively stable lake conditions as evidenced by increases in flood-tolerant taxa such as Taxodium distichium, Nyssa aquatica, and Planera aquatica. Periods of lower, fluctuating lake levels much like the present-day hydrology, existed throughout the remaining history of the lake (2,000 yrs B.P. to present) and are evidence of the changing influence from the surrounding drainage basin. During these periods of lowered lake levels, pollen and phytoliths assemblages display an overall increase in wetland taxa, most notably Cyperaceae and Sagittaria sp. and species that tolerate moderately flooded environments such as Quercus spp., Salix sp. and Carya aquatica.

In addition, archaeological settlement patterns documented around the lakebed are strongly associated with changes in the lake hydrology and vegetation. Increases in grasses and herbs often parallel these periods of increased site habitation in and around the lakebed. The first documentation of Zea maize in the Catahoula Lake area was documented at 1,600 years B.P. indicating small-scale agriculture during this period.