Correlation of Early Cretaceous carbon isotope stratigraphy and platform drowning events: a possible link?
Correlation of Early Cretaceous carbon isotope stratigraphy and platform drowning events: a possible link?
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DOI：
10.1016/s0031-0182(97)00109-0
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发表时间：
1998-03
期刊：
影响因子：
--
通讯作者：
H. Weissert;A. Lini;K. Föllmi;O. Kuhn
中科院分区：
文献类型：
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作者：
H. Weissert;A. Lini;K. Föllmi;O. Kuhn
早白垩世碳酸盐碳同位素记录以三次正高振幅（> 1.5‰）漂移为标志，每次覆盖的时间跨度超过106年。它们的年龄为Valanginian-Hauterivian晚期和Aptian早期和晚期。在一个沿着西特提斯洋断面的案例研究中，我们发现δ 13 C漂移、黑色页岩形成和广泛的碳酸盐台地淹没事件之间存在巧合。我们的结论是，δ 13 C的波动反映了在有机和碳酸盐碳汇之间的碳分配的变化，这是由气候引起的生态变化在白垩纪远洋和浅海环境中触发。温室气候条件的加剧导致风化、侵蚀和径流速度加快，并导致营养物质从大陆向海洋转移的速度加快。由此造成的海洋营养水平的增加有利于海洋浮游植物的生产和黑色页岩的沉积，而碳酸盐生产生物的条件变得不利。在Valanginian和Aptian海平面上升期间，受河流影响的海岸沿着碳酸盐生产的部分阻塞导致广泛的碳酸盐台地淹没。因此，广泛的同生黑色页岩沉积和淹没碳酸盐台地反映了海洋有机碳泵和碳酸盐碳泵对营养增强的浮游植物生产力的对比反应。海洋碳分配的变化反映在δ 13 C记录向更正值的转变。δ 13 C峰值的转变持续了几十万年。漂移的峰值，也涵盖了长达几十万年的时间跨度，反映了碳酸盐和有机碳汇之间碳分配的新稳定。一个新的加强碳酸盐沉积在中营养条件下，促进稳定的海平面上升在一个高的水平。δ 13 C值的降低表明，在有机碳积累速率不变或降低的情况下，碳酸盐碳埋藏速率增加。这些变化有助于海洋碳收支和全球碳循环在最初扰动后长达数百万年的稳定。
The Early Cretaceous carbonate carbon isotope record is marked by three positive high-amplitude (> 1.5‰) excursions each covering time spans of more than 106years. They are of late Valanginian-Hauterivian and early and late Aptian age. In a case study along a transect across the western Tethys Ocean we identified a coincidence between δ13C excursions, black shale formation, and widespread carbonate platform drowning events. We conclude that the δ13C excursions reflect a change in partitioning of carbon between the organic and carbonate carbon sinks which was triggered by climate induced ecological changes in Cretaceous pelagic and neritic environments. Episodes of intensified greenhouse climate conditions led to an increase in weathering, erosion and runoff rates and to elevated nutrient transfer rates from continents into oceans. The resulting increase in oceanic nutrient levels favoured marine phytoplankton production and black shale deposition while conditions for carbonate producing biotas became unfavourable. Partial choking of carbonate production along river influenced coasts resulted in widespread carbonate platform drowning during times of sea-level rise in the Valanginian and Aptian. Widespread contemporaneous black shale deposits and drowned carbonate platforms therefore reflect the contrasting response of the marine organic and carbonate carbon pumps to nutrient-enhanced phytoplankton productivity. The change in marine carbon partitioning is mirrored in a shift of the δ13C record towards more positive values. The transition to the δ13C peak values lasted up to several hundred thousand years. The peaks of the excursions, also covering a time span of up to several hundred thousand years, reflect a new stabilisation of the carbon partitioning between carbonate and organic carbon sinks. A renewed intensification of carbonate sedimentation under mesotrophic conditions was facilitated by stabilisation of the sea-level rise at a high level. Decreasing δ13C values record increasing carbonate carbon burial rates at constant or decreasing organic carbon accumulation rates. These changes contributed to the stabilisation of the marine carbon budget and the global carbon cycle up to millions of years after its initial perturbation.