Volcanism, CO2 and palaeoclimate: a Late Jurassic–Early Cretaceous carbon and oxygen isotope record
Volcanism, CO2 and palaeoclimate: a Late Jurassic–Early Cretaceous carbon and oxygen isotope record
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DOI：
10.1144/0016-764903-087
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发表时间：
2004-07
影响因子：
2.7
通讯作者：
H. Weissert;E. Erba
中科院分区：
文献类型：
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作者：
H. Weissert;E. Erba
提出了一条特提斯晚侏罗世-早白垩世复合碳氧同位素曲线。碳同位素数据提供了有关全球碳循环演变和扰动的信息。氧同位素数据与古生物信息相结合，作为古温度的代用品。将由此产生的气候和古海洋学趋势与生物钙化趋势和有利于或抑制生物钙化的海洋条件进行比较。瓦兰吉尼亚和阿普提安的碳同位素正异常与火山活动增加有关，火山活动被认为是大气中二氧化碳过量的来源。主要的增温脉冲伴随着阿普提安事件，而不是瓦兰吉尼亚碳同位素事件。观察到的阿普提亚早期温度的变化可能引发了沉积气体水合物的不稳定和甲烷向生物圈的突然释放，记录为正漂移之前明显的负碳同位素脉冲。这两种碳同位素异常都伴随着生物钙化危机，这可能是由二氧化碳引起的气候和地表水化学变化引发的。受河流影响的沿海水域和上升区的营养水平升高，进一步削弱了海洋钙化作用。这些条件与最晚侏罗纪盛行的“正常”营养条件形成对比，有利于生物钙化。碳和氧同位素曲线记录了稳定的碳循环模式和稳定的温度。我们得出结论，在大气-海洋系统中，生物钙化主要是由二氧化碳条件触发(和抑制)的。
A composite Tethyan Late Jurassic–Early Cretaceous carbon and oxygen isotope curve is presented. C-isotope data provide information on the evolution and perturbation of the global carbon cycle. O-isotope data are used as a palaeotemperature proxy in combination with palaeontological information. The resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification. Positive C-isotope anomalies in the Valanginian and Aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide. A major warming pulse accompanies the Aptian but not the Valanginian C-isotope event. The observed change in Early Aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion. Both C-isotope anomalies are accompanied by biocalcification crises that may have been triggered by pCO2-induced changes in climate and in surface water chemistry. Elevated nutrient levels in river-influenced coastal waters and in upwelling regions further weakened marine calcification. These conditions contrast with ‘normal’ trophic conditions prevailing in the latest Jurassic and favouring biocalcification. The C- and O-isotope curves record a stable mode of carbon cycling and stable temperatures. We conclude that biocalcification is mostly triggered (and inhibited) by CO2 conditions in the atmosphere–ocean system.