Palaeoecology of the biserial planktonic foraminifer Heterohelix moremani (Cushman) in the late Albian to middle Turonian Circum-North Atlantic

详细信息	查看全文 | 推荐本文 |

• 作者：Nederbragt ; Alexandra J. ; Erlich ; Robert N. ; Fouke ; Bruce W. ; et. al.
• 关键词：palaeoecology ; middle Cretaceous ; Heterohelicidae ; planktonic foraminifera ; carbon isotope stratigraphy ; Circum-North Atlantic
• 刊名：Palaeogeography ; Palaeoclimatology ; Palaeoecology
• 出版年：1998
• 期刊代码：68_00310182
• 类别：ear
• 出版时间：November 15, 1998
• 卷：144
• 期：1-2
• 页码：115-133
• 文件大小：2.45 M

摘要

The Cretaceous Heterohelix moremani (Cushman) was the only biserial planktonic foraminiferal species from its first appearance in the late Albian up to the Cenomanian/Turonian boundary. Within that time, it increased gradually in abundance relative to other planktonic foraminifera in five Circum-North Atlantic sections. It is generally rare in upper Albian sediments, common in most of the Cenomanian and very abundant in sediments representing the latest Cenomanian Oceanic Anoxic Event. Short-term variations on the overall abundance trend correlate with positive excursions in the bulk carbonate δ¹³C record. Maximum rain rates of H. moremani during OAE2 show that this species was an opportunist that did well in extreme conditions, but its overall distribution indicates that it is not necessarily a marker for very high palaeoproductivity environments. Stable oxygen and carbon isotope measurements on foraminiferal species indicate that H. moremani was a surface water dweller at least in part of its geographic range, but incorporated ¹³C out of equilibrium with ambient seawater. It is depleted in δ¹³C relative to other planktonic foraminifera, which is attributed to vital effects related to its opportunistic character.