Holocene foraminiferal assemblages from Firth of Tay, Antarctic Peninsula: Paleoclimate implications

Abstract

The 77 m sediment core from Firth of Tay provides complete record of glacial retreat and Holocene climate change on the Weddell Sea side of the Antarctic Peninsula that began ~ 9400 yr BP. Benthic foraminiferal data indicate significant environmental changes as recorded at ~ 600 m water depth at the drill site. Three foraminiferal assemblages (FAs): Globocassidulina spp.– Fursenkoina fusiformis FA, Miliammina arenacea FA, and Paratrochammina bartrami– Portatrochammina antarctica FA reflect increasingly glacier-distal conditions. They started with most glacier-proximal conditions that lasted until ~ 8800 yr BP, which is indicated by Cribroelphidium cf. webbi, and continued with elevated input of coarse glacial sediment until ~ 7750 yr BP. The Mid-Holocene Climatic Optimum between 7750 and 6000 yr BP appears to be the time of highest primary production, which led to higher corrosiveness of bottom waters, and biased species composition of the M. arenacea FA. It was terminated by minor cooling. The Neoglacial, that took place after ~ 3500 yr BP, is marked by an increase in P. bartrami and P. antarctica, the major constituents of the P. bartrami– P. antarctica FA. This FA became periodically dominant after ~ 900 yr BP indicating increasingly glacier-distal conditions due to cooling coinciding with increasing aridity, rising altitude of the glacial equilibrium line, and less glacial influence on marine biota. Episodic high-abundances of a fourth foraminiferal assemblage ( Globocassidulina biora FA) that occurs practically throughout the core is difficult to interpret explicitly. Although there are some concerns if G. biora FA represents in situ fauna, it appears to be an opportunistic fauna that dominated during periods of more glacial sediment input and sediment remobilization leading to better carbonate preservation.