Correlation between the Warepan/Otapirian and the Norian/Rhaetian stage boundary: implications of a global negative δ13Corg perturbation
Correlation between the Warepan/Otapirian and the Norian/Rhaetian stage boundary: implications of a global negative δ13Corg perturbation
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DOI：
10.1080/00288306.2021.1896558
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发表时间：
2021-03
影响因子：
2.2
通讯作者：
M. Rigo;H. Campbell
中科院分区：
文献类型：
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作者：
M. Rigo;H. Campbell
摘要诺利期/雷期界线段（晚三叠世）的特征是生物的大量更替和剧烈的气候变化。然而，这一界限仍有待正式界定。本文研究了新西兰北岛Kiritehere剖面一个保存完好的海相层序中的δ~（13）Corg记录。该剖面位于三叠纪高纬度地区（60 ° S以上），被认为是代表新西兰瓦雷潘/奥塔皮里阶界线的最佳暴露剖面。这是一个属于冈瓦纳的西兰迪亚地区的区域边界;它被描述在新西兰地质时标（NZGT）中，并被认为与诺里安/雷蒂安边界相关。利用综合化学地层学和生物地层学方法，我们已经确定了一个负δ 13 Corg偏移接近消失的标准大小的单纲动物（化石双壳类）在Kiritehere部分。我们认为这种负位移与用来定义雷氏基底的δ 13 Corg负位移相同。而Kiritehere剖面δ~（13）Corg负移的位置约为1000 °，而δ~（13）Corg负移的位置约为1000 °。6.40根据生物地层学，低于公认的Warepan/Otapirian边界位置。这种δ 13 Corg同位素变化，最好被认为是一个化学地层事件，在这里被认为是一个全球性的现象。
ABSTRACT The Norian/Rhaetian boundary interval (Late Triassic) is characterised by significant biotic turnover and severe climatic changes. However, this boundary still awaits formal definition. We have investigated the δ13Corg record within a well-preserved marine sequence exposed in the Kiritehere section, North Island, New Zealand. This section was located at higher latitudes (above 60°S) during the Triassic, and is considered the best exposed section representative of the New Zealand Warepan/Otapirian stage boundary. This is a regional boundary pertaining to the Zealandia region of Gondwana; it is described in the New Zealand Geological Timescale (NZGT) and it has been recognised as being correlative with the Norian/Rhaetian boundary. Using an integrated chemo- and biostratigraphic approach, we have identified a negative δ13Corg shift close to the disappearance of the standard-sized monotids (fossil bivalves) in the Kiritehere section. We interpret this negative shift to be the same negative δ13Corg shift that has been proposed to define the base of the Rhaetian. However, the position of the negative δ13Corg shift in the Kiritehere section is ca. 6.40 m below the accepted position of the Warepan/Otapirian boundary, based on biostratigraphy. This δ13Corg isotopic shift, best thought of as a chemostratigraphic event, is regarded here as a global phenomenon.