Birth and death of the Late Cretaceous "La Luna Sea", and origin of the Tres Esquinas phosphorites
Birth and death of the Late Cretaceous "La Luna Sea", and origin of the Tres Esquinas phosphorites
复制标题
白垩纪晚期“月神海”的诞生和消亡，以及特雷斯奎纳斯磷矿的起源
DOI：
10.1016/s0895-9811(00)00016-x
复制
发表时间：
2000
影响因子：
1.8
通讯作者：
M. Lorente
中科院分区：
文献类型：
--
作者：
R. Erlich;A. Nederbragt;M. Lorente
委内瑞拉西北部拉卢纳和纳瓦伊地层富含有机碳层段的沉积受关键古水深障碍物（Santa玛尔塔和桑坦德山脉、科维纳地块和梅里达安第斯山脉）发育的控制。这些都加剧了“月球海”缺氧的发展，造成循环不良和通风有限。高蒸发率和低降水率（高盐度底层水）以及高水平的海藻生产力（高有机物通量）也促进了缺氧。不常见的河流来源增加了养分供应。从晚Santonian到白垩纪末，底层水含氧量增加。缺氧底层沃茨的通风可能由于更频繁或更强烈的季节性上涌（由更高的风应力引起）和灾难性的倾覆以及一个关键的古水深障碍的消除而得到加强。倾覆事件的常见副产品是大量浮游植物水华，从而产生赤潮。鱼类和海洋爬行动物的骨床内的特雷斯Esquinas成员（拉月神组）是由于在这些事件中的大规模死亡率，并在哥伦比亚东部类似的坎帕尼亚单位相关。在马斯特里赫特期，增加通风，结合silicicocarbons稀释，最终产生的沉积物总有机碳（TOC）含量较低。
Deposition of organic carbon-rich intervals of the La Luna and Navay formations of northwestern Venezuela was governed by the development of key paleobathymetric barriers (Santa Marta and Santander massifs, Paraguana Block, and ancestral Mérida Andes). These enhanced the development of anoxia in the “La Luna Sea” by causing poor circulation and limited ventilation. Anoxia was also promoted by high evaporation and low precipitation rates (high salinity bottom water), and high levels of marine algal productivity (high organic matter flux). Nutrient supply was augmented by infrequent fluvial sources. Bottom water oxygen levels increased from the Late Santonian through the end of the Cretaceous. Ventilation of anoxic bottom waters may have been enhanced by more frequent or intense seasonal upwelling (caused by higher wind stress) and catastrophic overturn, as well as the removal of a key paleobathymetric barrier. Common byproducts of overturn events were massive phytoplankton blooms, which produced red tides. Fish and marine reptile bone beds within the Tres Esquinas Member (La Luna Formation) are attributed to massive mortality during these events, and are correlative with similar Campanian units in eastern Colombia. During the Maastrichtian, increasing ventilation, combined with siliciclastic dilution, ultimately produced sediments with lower total organic carbon (TOC) content.