Carbon and oxygen isotope stratigraphy of the Lower Mississippian (Kinderhookian-lower Osagean), western United States: Implications for seawater chemistry and glaciation
Carbon and oxygen isotope stratigraphy of the Lower Mississippian (Kinderhookian-lower Osagean), western United States: Implications for seawater chemistry and glaciation
复制标题
DOI：
10.1130/0016-7606(2002)114
复制
发表时间：
2002
影响因子：
4.9
通讯作者：
M. Saltzman
中科院分区：
文献类型：
--
作者：
M. Saltzman
在爱达荷州东南部和内华达州的三个剖面的金德胡克阶上部和奥萨吉阶早期碳酸盐中，发现了正碳同位素（δ 1 3 C）漂移。最古老的δ 13 C峰（+7‰）出现在等时牙形刺带，而较年轻的峰出现在典型带。这些变化记录在一系列碳酸盐岩岩相中，这些岩相代表着沿着陆架的不同水深。在爱达荷州东南部的撒马利亚山剖面进行的δ 1 3 C和δ 1 8 O岩相采样记录了最浅的水条件，由交错层状的骨骼和泥质颗粒岩指示。最深的水条件出现在内华达州东部的Pahranagat山脉部分，主要由生物扰动石灰泥岩和骨架杂砂岩组成。这些分布较广的沉积盆地的δ 1 3 C值显示出一致的趋势，与西欧和北美中部大陆的腕足类方解石以及犹他州和怀俄明州的碳酸盐岩生成的早密西西比期曲线相关。δ 18 O值在剖面上逐渐变正，与Kinderhookian晚期δ 13 C值的正趋势基本一致。在爱达荷州东南部和内华达州的剖面中，没有发现陆上暴露面，至少δ 1 3 C趋势被解释为主要海水波动。海平面变化发生在Kinderhookian晚期δ 1 3 C偏移开始附近（等势带的早期到中部）和δ 1 3 C偏移的峰值（Kinderhookian-Osagean边界），尽管与Antler造山带相关的构造变化可能改变了海平面变化特征。
A positive carbon isotope (δ 1 3 C) excursion has been recognized in upper Kinderhookian and early Osagean carbonates in three sections in southeast Idaho and Nevada. The oldest δ 1 3 C peak (+7‰) is dated to the isostichaconodont zone, and a younger peak occurs in the typicus Zone. The shifts are recorded in a range of carbonate lithofacies representing various water depths along the shelf. Lithofacies sampled for δ 1 3 C and δ 1 8 O at the Samaria Mountain section in southeast Idaho record the shallowest-water conditions, indicated by cross-bedded skeletal and peloidal grainstones. The deepest water conditions are present in the Pahranagat Range section in eastern Nevada, which consists mainly of bioturbated lime mudstone and skeletal wackestone. The δ 1 3 C values from these widely separated sedimentary basins show a consistent trend that correlates with Early Mississippian curves generated from brachiopod calcite in western Europe and the Midcontinent of North America, as well as dolomites in Utah and Wyoming. δ 1 8 O values become more positive up section, generally paralleling the positive trend in δ 1 3 C during the late Kinderhookian. No subaerial exposure surfaces are recognized in the sections examined in southeast Idaho and Nevada, and at least the δ 1 3 C trends are interpreted as primary seawater fluctuations. Sea-level changes occurred near the beginning of the late Kinderhookian δ 1 3 C shift (early to middle parts of the isosticha Zone) and within the peak of the δ 1 3 C excursion (Kinderhookian-Osagean boundary), although tectonic changes associated with the Antler orogeny have likely modified the eustatic signature.