Sedimentary evolution and depositional architecture of a lowstand sequence set: the Lower Cretaceous Mulichinco Formation, Neuquén Basin, Argentina
Sedimentary evolution and depositional architecture of a lowstand sequence set: the Lower Cretaceous Mulichinco Formation, Neuquén Basin, Argentina
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低位层序组的沉积演化和沉积构造：阿根廷内乌肯盆地下白垩统 Mulichinco 组
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发表时间：
2005
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影响因子：
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通讯作者：
J. Howell
中科院分区：
文献类型：
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作者：
E. Schwarz;J. Howell
摘要Valanginian时代的Mulichinco组沉积在内乌肯盆地（阿根廷中西部）期间和之后的海平面大幅下降，部分由构造反转脉冲触发。该地层代表一个低位楔，在那里有极好的露头，加上精细的生物地层覆盖，允许对同期的非海相和海相沉积物进行详细的研究。在Mulichinco组中确定了14个相组合。它们代表了从砾石河流辫状平原到外大陆架海洋环境的各种环境中的堆积。沉积环境的分布，以及关键表面和地层模式的识别，导致了早期和晚期低位，海侵和高位体系域的识别。因此，Mulichinco低位楔包括一个三级层序，持续约2Ma，代表一个低位层序组。在Mulichinco沉积区内，海岸线沉积特征沿走向沿着变化很大，下切河谷内不发育冲积矿床。构造派生的地形，盆地自然地理和断层控制的沉降被解释为Mulichinco低位楔演化的主要控制因素。这项研究的结果有重要的意义，了解内乌肯盆地的历史，并说明以前没有记录的建筑复杂性，可能存在于低位楔。
Abstract The Valanginian-aged Mulichinco Formation was deposited in the Neuquén Basin (west-central Argentina) during and immediately after a major fall in sea level, partially triggered by a tectonic inversion pulse. The formation represents a lowstand wedge where excellent outcrops, together with refined biostratigraphic coverage, have permitted the detailed examination of contemporaneous non-marine and marine deposits. Fourteen facies associations were identified in the Mulichinco Formation. They represent accumulation in a variety of environments ranging from gravelly fluvial braidplains to outer-shelf marine settings. Distribution of depositional environments, together with the identification of key surfaces and stratal patterns, has resulted in the identification of early and late lowstand, transgressive and highstand systems tracts. Accordingly, the Mulichinco lowstand wedge comprises one third-order sequence that lasted about 2 Ma and represents a lowstand sequence set. The character of shoreline sedimentation was highly variable along strike within the Mulichinco depositional area and alluvial deposits were not developed within incised valleys. Tectonically derived topography, basin physiography and fault-controlled subsidence are interpreted to have been the main controls on the evolution of the Mulichinco lowstand wedge. The results of this study have important implications for understanding both the history of Neuquén Basin and illustrating the previously undocumented architectural complexity that may exist within lowstand wedges.