Foraminifera And Coccolithophorid Assemblage Changes In The Panama Basin During The Last Deglaciation: Response To Sea-Surface Productivity Induced By A Transient Climate Change

HR: 1340h
AN: PP23B-1411 [Abstracts]
TI: Foraminifera And Coccolithophorid Assemblage Changes In The Panama Basin During The Last Deglaciation: Response To Sea-Surface Productivity Induced By A Transient Climate Change
AU: * Martinez, I
EM: jimartin@eafit.edu.co
AF: Universidad EAFIT, Marine Sciences Group, Crr. 49 # 7 sur 50 Av. Las Vegas, Medellin, A.A. 3300 Colombia
AU: Rincon, D
EM: drincon@eafit.edu.co
AF: Universidad EAFIT, Marine Sciences Group, Crr. 49 # 7 sur 50 Av. Las Vegas, Medellin, A.A. 3300 Colombia
AU: Yokoyama, Y
EM: yokoyama@eps.s.u-tokyo.ac.jp
AF: University of Tokyo, Department of Earth and Planetary Sciences, Department of Earth and Planetary Sciences, Dept. Earth & Planetary Sciences, Bldg#1, 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: Barrows, T
EM: Tim.Barrows@anu.edu.au
AF: The Australian National University, Dept. Nuclear Sciences, Canberra ACT, Canberra, ACT 0200 Australia
AB: The response of community assemblages of planktonic and benthonic foraminifera and coccolithophorids to transient climate change are explored for the uppermost 2m of cores ODP677B (1.2鑞; 83.74鱒, 3461m) and TR163-38 (1.34驙; 81.58鱒, 2200m), for the last ~40ka. Results suggest that the deglaciation interval was a time of increased productivity and a major reorganization of planktonic trophic webs. The succession in dominance of planktonic foraminifera species Globorotalia inflata, Globigerina bulloides, and Neogloboquadrina pachyderma denote four periods of oceanographic change: (1) advection (24 to 20ka), (2) strong upwelling (20 to 15ka), (3) weak upwelling (14 to 8ka) and (4) oligotrophy (8ka to Present). Strong upwelling for the deglaciation interval is supported by the low Florisphaera profunda / other coccolithophorids ratio and the high percentage abundance of Gephyrocapsa oceanica. Benthonic foraminifera assemblage changes are different in both cores and suggest significant regional variations in surface productivity and/or oxygen content at the seafloor, and a decoupling between surface productivity and export production to the seafloor. This decoupling is evidenced by the inverse relationship between the percentage abundance of infaunal benthonic foraminifera and the percentage abundance of N. pachyderma. The terrigenous input of the Colombian Pacific rivers, particularly the San Juan River, is suggested as a possible mechanism. Finally, the Globorotalia cultrata /Neogloboquadrina dutertrei ratio, is used to reconstruct the past influence of the Costa Rica Dome - Panama Bight and cold tongue upwelling systems in the Panama Basin. A northern influence is suggested for the late Holocene (after 5ka), and the last glacial (before 20ka), whereas a southern influence is suggested for the 20 to 5ka interval. There is a correspondence between our reconstructed northern and southern influences and previously proposed positions of the Intertropical Convergence Zone (ITCZ) after the Last Glacial Maximum (LGM).
DE: 9355 Pacific Ocean
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 4279 Upwelling and convergences
DE: 3030 Micropaleontology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting