Three‐dimensional modelling and sequence stratigraphy of a carbonate ramp‐to‐shelf transition, Permian Upper San Andres Formation
Three‐dimensional modelling and sequence stratigraphy of a carbonate ramp‐to‐shelf transition, Permian Upper San Andres Formation
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二叠纪上圣安德烈斯组碳酸盐岩斜坡到陆架过渡的三维建模和层序地层学
DOI：
10.1111/j.1365-3091.2008.00967.x
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发表时间：
2008
期刊：
影响因子：
3.5
通讯作者：
J. A. Bellian
中科院分区：
文献类型：
--
作者：
R. Phelps;C. Kerans;Samuel Z. Scott;X. Janson;J. A. Bellian
本研究强调了二叠系圣安德烈斯组碳酸-硅-碎屑混合斜形斜坡峰至盆地地层几何形状的三维变异性。标准的现场技术和使用地面激光雷达的测绘揭示了通道化、冲刷和丘状外斜坡地层的高度建筑复杂性。这些地物的发展是沿斜坡剖面的位置和相对海平面波动的函数。外斜坡远端粗粒和细粒浊积岩的沉积是通过稀浊流和高密度浊积流发生的，是单个旋回内高位碳酸盐脱落的结果。在这种情况下，相对海平面的高频旋回是根据浊积岩频率、横向范围和组成来解释的。在低水位旋回期间，海底的硅屑沉积物绕道导致了不同程度的硅屑保存。在盆地和远外斜坡处，以点源低位楔和线源早期海侵毯子的形式保存了大量的硅塑性物质。在外斜坡的丘状地形中，硅质碎屑保存很少或不存在，并且罕见的切割河道为识别层序边界提供了最好的机会。外坡道丘状地形的生长开始于冲刷，随后是生物篱建设、黄柳丘建设和等径垂造的结合。然后，土丘之间的区域被沉积物填满，土丘的继续生长被可容纳限度所阻止。土丘生长与相对海平面的高频周期无关，但依赖于低频周期所决定的可调节性。在复合层序的海侵阶段，形成了低角斜坡斜形，外斜坡为丘状地形。在复合层序的高点，斜坡转变为具有斜斜几何形状的陆架，土丘生长终止。这个例子代表了斜坡到陆架的转变，这是由相对海平面波动而不是生态或构造控制的强迫的结果。
This study highlights three‐dimensional variability of stratigraphic geometries in the ramp crest to basin of mixed carbonate–siliciclastic clinoforms in the Permian San Andres Formation. Standard field techniques and mapping using ground‐based lidar reveal a high degree of architectural complexity in channellized, scoured and mounded outer ramp stratigraphy. Development of these features was a function of location along the ramp profile and fluctuations in relative sea‐level. Deposition of coarse‐grained and fine‐grained turbidites in the distal outer ramp occurred through dilute and high‐density turbidity flows and was the result of highstand carbonate shedding within individual cycles. In this setting, high‐frequency cycles of relative sea‐level are interpreted on the basis of turbidite frequency, lateral extent and composition. Submarine siliciclastic sediment bypass during lowstand cycles resulted in variable degrees of siliciclastic preservation. Abundant siliciclastic material is preserved in the basin and distal outer ramp as point‐sourced lowstand wedges and line‐sourced early transgressive blankets. In mounded topography of the outer ramp, siliciclastic preservation is minimal to absent, and rare incised channels offer the best opportunity for recognition of a sequence boundary. Growth of mounded topography in the outer ramp began with scouring, followed by a combination of bioherm construction, fusulinid mound construction and isopachous draping. Intermound areas were then filled with sediment and continued mound growth was prevented by an accommodation limit. Mound growth was independent of high‐frequency cycles in relative sea‐level but was dependent on available accommodation dictated by low‐frequency cyclicity. Low‐angle ramp clinoforms with mounded topography in the outer ramp developed during the transgressive part of a composite sequence. Mound growth terminated as the ramp transformed into a shelf with oblique clinoform geometries during the highstand of the composite sequence. This example represents a ramp‐to‐shelf transition that is the result of forcing by relative sea‐level fluctuations rather than ecologic or tectonic controls.