Upper Cretaceous carbon- and oxygen-isotope stratigraphy of hemipelagic carbonate facies from southern Tibet, China
Upper Cretaceous carbon- and oxygen-isotope stratigraphy of hemipelagic carbonate facies from southern Tibet, China
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DOI：
10.1144/0016-764905-046
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发表时间：
2006-03-01
影响因子：
2.7
通讯作者：
Cui, J
中科院分区：
文献类型：
--
作者：
Li, XH;Jenkyns, HC;Cui, J
从西藏南部定日上白垩纪半远洋沉积物中获得的高分辨率碳同位素曲线显示出与其他大陆上建立的模式相似，特别是在Cenomanian-Turonian边界上存在明确的正偏移，其中三角洲（13）C值超过千分之3.5。从上Turonian到下Campanian，三角洲（13）C值普遍下降，除了在中Coniacian一个小的正偏移：从欧洲记录的趋势。相对较低的delta（13）C值（c.在西藏Santonian-Campanian和Campanian-Maastrichtian边界的1000 ppm（千分之一）的沉积物定义了一个显著的广泛的正偏移，该偏移集中在Campanian中期，并以向该阶段结束时的突然下降而终止。与欧洲和北非的数据相比，西藏剖面的δ（13）C值普遍低c。1.5千分之一，除了中部坎帕尼亚正偏移值（δ（13）C c。2份/千）与欧洲和北非的记录相当。这些差异被解释为反映了携带不同碳同位素特征的水团的可变混合，例如，靠近海洋有机碳主要汇的地区记录的三角洲（13）C值高于位于更远区域的地区。氧同位素比值虽然受成岩作用的影响，但可能记录古温度信号。
A high-resolution carbon-isotope curve derived from Upper Cretaceous hemipelagic sediments cropping out at Tingri, southern Tibet, shows similarities to patterns established on other continents, notably in the presence of a well-defined positive excursion across the Cenomanian-Turonian boundary where delta(13)C values exceed 3.5 parts per thousand. From the upper Turonian to the lower Campanian, delta(13)C values generally decline, apart from a minor positive excursion in the middle Coniacian: a trend that departs from that recorded from Europe. Relatively low delta(13)C values (c. 1 parts per thousand) at the Santonian-Campanian and Campanian-Maastrichtian boundaries in Tibet define a prominent broad positive excursion centred in the middle Campanian and terminated by an abrupt fall towards the close of the stage. When compared with data from Europe and North Africa, the delta(13)C values of the Tibetan section are generally lower by c. 1.5 parts per thousand, except for the middle Campanian positive excursion where values (delta(13)C c. 2 parts per thousand) are comparable with those documented from Europe and North Africa. These differences are interpreted as reflecting variable mixing of water masses carrying different carbon-isotope signatures, such that areas close to the major sinks of marine organic carbon recorded higher delta(13)C values than those located in more distal regions. Oxygen-isotope ratios, albeit affected by diagenesis, may record a palaeotemperature signal.