Coupled productivity and carbon isotope records in the southwest Pacific Ocean during the late Miocene–early Pliocene biogenic bloom
Coupled productivity and carbon isotope records in the southwest Pacific Ocean during the late Miocene–early Pliocene biogenic bloom
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DOI：
10.1016/s0031-0182(02)00508-4
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发表时间：
2002-11
期刊：
影响因子：
--
通讯作者：
K. Grant;G. Dickens
中科院分区：
文献类型：
--
作者：
K. Grant;G. Dickens
在中新世晚期和上新世早期，印度洋和太平洋前缘带之下沉积的生物成因组分高速积累。在此期间，散体和有孔虫碳酸盐的δ13C也有所下降。尽管这两个观测结果可能是因果联系的，并表明全球生物地球化学循环发生了重大扰动，但前锋带下的任何地点都没有独立的出口生产记录和关键研究区间内多个碳酸盐相上的δ13C。深海钻探项目(DSDP)地点590位于塔斯曼前锋(Tf)之下，Tasman Front(Tf)是西南太平洋上产生涡流的急流。为了补充该地区浮游和底栖有孔虫的δ13C记录，在第590号站建立了晚第三纪CaCO3质量积累率(MAR)、Ca/Ti、Ba/Ti、Al/Ti以及块状碳酸盐和有孔虫δ13C的记录。δ的13C记录包括散装沉积物、散装沉积物组分(<；63μm和5-25μm)，以及浮游有孔虫、球囊有孔虫、球囊有孔虫(带和不带囊)和普通有孔虫。按照目前的时间尺度，上中新统和下中新统沉积的CaCO3MARs、Ca/Ti、Al/Ti和Ba/Ti比值相对于上覆和下伏单元高出2~3倍。所有δ13C记录也都出现了显著的下降。所有证据都表明，在大约9 Ma至3.8 Ma之间，出口产量的增加--“生物源水华”--延伸到了西南太平洋，而这一现象与δ13C--“Chron C3AR碳迁移”--的变化相结合。而CaCO3MARS峰值约5 Ma，元素比值最高约6.5 Ma，有孔虫δ13C开始下降约8 Ma，块状碳酸盐δ13C开始下降约5.6 Ma。这些记录之间的时间差异可以通过TF上升流制度的变化来解释，这可能意味着海洋-大气环流变化与广泛的初级生产力之间的联系。
Biogenic components of sediment accumulated at high rates beneath frontal zones of the Indian and Pacific oceans during the late Miocene and early Pliocene. The δ13C of bulk and foraminiferal carbonate also decreased during this time interval. Although the two observations may be causally linked, and signify a major perturbation in global biogeochemical cycling, no site beneath a frontal zone has independent records of export production and δ13C on multiple carbonate phases across the critical interval of interest. Deep Sea Drilling Project (DSDP) site 590 lies beneath the Tasman Front (TF), an eddy-generating jetstream in the southwest Pacific Ocean. To complement previous δ13C records of planktic and benthic foraminifera at this location, late Neogene records of CaCO3mass accumulation rate (MAR), Ca/Ti, Ba/Ti, Al/Ti, and of bulk carbonate and foraminiferal δ13C were constructed at site 590. The δ13C records include bulk sediment, bulk sediment fractions (<63 μm and 5–25 μm), and the planktic foraminifera Globigerina bulloides, Globigerinoides sacculifer (with and without sac), and Orbulina universa. Using current time scales, CaCO3MARs, Ca/Ti, Al/Ti and Ba/Ti ratios are two to three times higher in upper Miocene and lower Pliocene sediment relative to overlying and underlying units. A significant decrease also occurs in all δ13C records. All evidence indicates that enhanced export production – the ‘biogenic bloom’ – extended to the southwest Pacific Ocean between ca. 9 and 3.8 Ma, and this phenomenon is coupled with changes in δ13C – the ‘Chron C3AR carbon shift’. However, CaCO3MARs peak ca. 5 Ma whereas elemental ratios are highest ca. 6.5 Ma; foraminiferal δ13C starts to decrease ca. 8 Ma whereas bulk carbonate δ13C begins to drop ca. 5.6 Ma. Temporal discrepancies between the records can be explained by changes in the upwelling regime at the TF, perhaps signifying a link between changes in ocean–atmosphere circulation change and widespread primary productivity.