US Gulf Coast vegetation dynamics during the latest Palaeocene

Pollen and spore floras from the Bear Creek section in western Alabama (US Gulf Coast) record vegetation events from the lower to middle Tuscahoma For mation (late Palaeocene mid NP9). Sporomorphs are abundant and well preserv ed in these sediments and are used as a proxy to record vegetation change o ver time. We present results from both palynofloral and clay mineral analys es in the interval approximately 0.4-0.1 my before the Paleocene/Eocene the rmal maximum (PETM); a period of transient and intense global warming that had a profound effect on animal and plant groups in high latitudes. An impo rtant factor that has a significant bearing on our understanding of turnove r across the PETM is that of climate/environmental stability prior to the P ETM in terrestrial ecosystems. Palynological analysis with a between sample resolution of <10 ky suggests that the vegetation type characterising the US Gulf Coastal plains was highly stable with no significant changes in com position and diversity that can be successfully correlated with orbital osc illations. Our results indicate considerable stability of the vegetation ty pe on time-scales of 10(4)-10(5) yr. Clay mineral suites show the dominance of smectite and illite throughout the studied section with minor fluctuati ons in the abundance of kaolinite (ranging from 2 to 10%) that indicates a high seasonality of precipitation throughout our studied section. The exact stratigraphic position of the PETM is unknown on the US Gulf Coast but dat a from existing publications suggests there is little change in the vegetat ion type across the Palaeocene/Eocene boundary with no major immigration or turnover events. Dinocysts art: restricted in both diversity and occurrenc e but Apectodinium homomorphum is present with <similar to>30% abundance th roughout the studied section and provides some evidence that the Apectodini um acme is not correlative with the PETM at middle latitudes. (C) 2001 Else vier Science B.V. All rights reserved.