Early Paleogene climate and productivity of the Eastern Equatorial Atlantic, off the western coast of Ghana

摘要

Early Paleogene warmth is consistent with global observation, although temperature reconstructions were characterized by some degree of uncertainty. In spite of applied corrections, the suggested epifaunal benthic foraminifera maximum temperature range (23.65-30.36℃) was still above the proposed maximum tropical sea surface temperature of ～27℃, confirming that foraminiferally derived temperatures are strongly dependent on assumptions. Paleoclimate and paleoproductivity of the Eastern Equatorial Atlantic were poorly correlated (R~2 < 0) due to major anomalies. δ~(13)C isotopic signatures have been largely and independently used to resolve discrepancies in eight anomalous depths identified in this study, in view of overlapping δ~(18)C isotopic signatures. The last three anomalies are consistent with the dramatic onset of global cooling which occurred during this interval. The first five still remain anomalous, challenging the conventional view that glacial oceans are more productive than interglacial oceans. Discrepancies in these anomalous depths could have been due to artifacts, preservation biases related to dissolution, and/or shell thickening or encrustation. However, this study suggests extratropical variability and climate dynamics, reflecting regional anomalies due to upwelling or feedback mechanisms of poleward heat transport, which are prevalent in the Eastern Equatorial Atlantic.