Early to middle Eocene magneto-biochronology of the southwest Pacific Ocean and climate influence on sedimentation: Insights from the Mead Stream section, New Zealand
Early to middle Eocene magneto-biochronology of the southwest Pacific Ocean and climate influence on sedimentation: Insights from the Mead Stream section, New Zealand
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DOI：
10.1130/b31147.1
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发表时间：
2015-05-01
影响因子：
4.9
通讯作者：
Slotnick, Benjamin S.
中科院分区：
文献类型：
--
作者：
Dallanave, Edoardo;Agnini, Claudia;Slotnick, Benjamin S.
米德溪剖面（新西兰南岛）由一系列650米厚的连续、暴露良好的地层组成，这些地层从晚白垩世到始新世中期沉积在南太平洋大陆斜坡上。我们研究了最上面的古新世-中始新世部分的部分，其中包括类似360米的石灰岩和泥灰岩，详细的磁极性地层和钙质超微化石和有孔虫生物地层。磁性生物地层学数据表明，该剖面跨越了从C24 r到C18 n的磁极性年代，从NP 9a到NP 17（CNP 11-CNE 15，根据最近修订的古近纪分带）的钙质超微化石带，以及从怀帕湾到新西兰的Bortonian阶段（即，从伊普雷西亚的基地到巴顿的国际舞台）。因此，米德河段长17米。y.（56-39 Ma）西南太平洋历史。钙质超微化石生物层位的年龄与文献中的低中纬度数据一致，表明在始新世早期-中期，低中纬度钙质超微化石区至少延伸到南纬50度-55度。从米德河部分与地磁极性时间尺度的磁极性地层的相关性，使我们能够推导出沉积物积累率（SAR），范围在8和44米/米之间。y.对比SAR与古温度代用记录，我们发现，两个时间间隔的增加SAR发生在始新世早期的气候最佳（52-50马），并在短暂的变暖事件峰值与始新世中期的气候最佳（40.5马）。这种相关性表明，在米德河，早中始新世的气候演变记录在一个沉积模式，即在百万年的时间尺度上，温暖的气候促进大陆风化，运输和陆源沉积物的积累。
The Mead Stream section (South Island, New Zealand) consists of a 650-m-thick series of continuous, well-exposed strata deposited on a South Pacific continental slope from the Late Cretaceous to the middle Eocene. We examined the uppermost Paleocene-middle Eocene part of the section, which consists of similar to 360 m of limestone and marl, for detailed magnetic polarity stratigraphy and calcareous nannofossil and foraminifera biostratigraphy. Magneto-biostratigraphic data indicate that the section straddles magnetic polarity chrons from C24r to C18n, calcareous nannofossil zones from NP9a to NP17 (CNP11-CNE15, following a recently revised Paleogene zonation), and from the Waipawan to the Bortonian New Zealand stages (i.e., from the base of the Ypresian to the Bartonian international stages). The Mead Stream section thus encompasses 17 m. y. (56-39 Ma) of southwest Pacific Ocean history. The ages of calcareous nannofossil biohorizons are consistent with low-to midlatitude data from the literature, indicating that during the early-middle Eocene, the low-to midlatitude calcareous nannofossil domain extended at least to similar to 50 degrees S-55 degrees S in the South Pacific. Correlation of the magnetic polarity stratigraphy from the Mead Stream section with the geomagnetic polarity time scale allows us to derive sediment accumulation rates (SAR), which range between 8 and 44 m/m. y. Comparing the SAR with paleotemperature proxy records, we found that two intervals of increased SAR occurred during the early Eocene climatic optimum (52-50 Ma) and during the transient warming event peaking with the middle Eocene climatic optimum (40.5 Ma). This correlation indicates that, at Mead Stream, the climate evolution of the early-middle Eocene is recorded in a sedimentation pattern whereby, on a million-year time scale, warmer climate promoted continental weathering, transportation, and accumulation of terrigenous sediments.