Paper No. 1
Presentation Time: 9:00 AM-6:00 PM
LATE PERMIAN PALEOENVIRONMENTAL FACTORS EXPOUNDED THROUGH ANALYSIS OF A FOREST-FLOOR PALEOSOL PROFILE, KAROO BASIN, SOUTH AFRICA
KNIGHT, Cassi1, GASTALDO, Robert A.
1 and NEVELING, Johann
2, (1)Department of Geology, Colby College, 5807 Mayflower Hill Drive, Waterville, ME 04901, (2)Council for Geosciences, Private Bag x112, Pretoria, 0001, South Africa, knight.cassi@gmail.com
Beaufort Group paleosols from the Karoo Basin, South Africa, record the paleoenvironmental conditions that existed prior to and after the Permian-Triassic extinction event. Paleosol exposures from Wapadsberg Pass, Eastern Cape Province, represent a well preserved forest-floor litter overlying an interpreted inceptisol, a condition unique to the basin. Vegetation that colonized this landscape included a canopy of the gymnosperm
Glossopteris and an understory of sphenopsids (
Phyllotheca and
Tryzygia). Wapadsberg Pass paleosol sites were sampled for petrographical and geochemical analyses to constrain interpretations of paleoenvironmental conditions that existed ~ 70 m below the Permian-Triassic Boundary (PTB). This project focuses on determining paleosol-nutrient quality to test a hypothesis that plant toxicity may be responsible for the reported decrease in
Glossopteris-leaf size prior to the PTB event.
The greenish-grey (5GY 6/1) paleosol is an iron-stained siltstone with intervals of bedded very-fine sand to silt. The paleosol has a maximum thickness of 70 cm, with a coarser interval at ~30 cm depth. The litter horizon is concentrated in the upper 20 cm of the profile, and includes remnants of poorly preserved Glossopteris leaves and Vertebraria roots. Rooting structures penetrate to ~70 cm depth. Tuffite is interspersed in and caps the paleosol.
Primary structures in petrographic section include ripples, parallel bedding, and small-scale soft-sediment deformation. These are partially destroyed due to phytoturbation and bioturbation. All paleosol sites examined contain an identifiable tuffite, characterized as a mix of well-rounded to angular, transparent clasts. These are distributed as irregular pockets cross-cutting bedding and as dispersed isolated clasts within the fine matrix. TOC:TON, in addition to geochemical data obtained using ICP, are pending. Analytical results will be presented and discussed.