Discontinuity Surfaces, Clinoforms, and Facies Architecture in a Wave-Dominated, Shoreface-Shelf Parasequence
Discontinuity Surfaces, Clinoforms, and Facies Architecture in a Wave-Dominated, Shoreface-Shelf Parasequence
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波浪主导的岸面陆架准层序中的不连续面、斜面和相结构
DOI：
10.1306/2dc40914-0e47-11d7-8643000102c1865d
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发表时间：
2000
影响因子：
2
通讯作者：
G. Hampson
中科院分区：
文献类型：
--
作者：
G. Hampson
摘要：对犹他州布克悬崖出露的一个以波浪作用为主的滨面 - 陆架准层序进行详细的露头分析，揭示了一些小型地层不连续面，这些不连续面界定了斜层理。识别出两种类型的不连续面，每种都具有独特的岩性特征和几何形态。无沉积作用的不连续面表现为风暴成因的事件层厚度突然减小以及合并程度降低，被解释为记录了沉积间断。这些不连续面所界定的斜层理具有上凹的几何形状，在沉积倾向方向上延伸800 - 6000米，倾角平缓（0.02 - 0.58°）。侵蚀不连续面表现为事件层合并程度、粒度和砂含量突然增加，被解释为增强的风暴浪冲刷作用。这些不连续面界定了更陡倾（0.22 - 0.95°）、上凹的斜层理，在沉积倾向方向上延伸100 - 1600米，在沉积走向方向上延伸500 - 1500米。小型地层不连续面的分布和合并界定了独特的相结构线性带，其方向与古海岸线走向平行。利用一个简单的假设，即滨面 - 陆架平衡剖面在滨面迁移过程中对于每种类型的不连续面大致保持不变（“布鲁恩法则”），准层序内部的相结构可以推测性地根据海岸线轨迹来解释，海岸线轨迹反映了沉积物供给和可容纳空间之间的平衡。由此得出的解释支持这样一种观点，即海岸线轨迹对准层序内部的相结构以及滨面 - 陆架剖面的保存具有强烈的控制作用。
ABSTRACT Detailed outcrop analysis of a wave-dominated, shoreface-shelf parasequence exposed in the Book Cliffs, Utah reveals minor stratigraphic discontinuities, which define clinoforms. Two types of discontinuity are recognized, each with a distinctive lithologic character and geometry. Nondepositional discontinuities are marked by an abrupt decrease in the thickness and amalgamation of storm-generated event beds, and are interpreted to record hiatuses in sedimentation. These discontinuities define clinoforms with a concave-upward geometry that dip gently (0.02-0.58°) over distances of 800-6000 m down depositional dip. Erosional discontinuities are marked by an abrupt increase in event-bed amalgamation, grain size, and sand content, and are interpreted as enhanced storm-wave scours. These discontinuities define more steeply dipping (0.22-0.95°), concave-upward clinoforms that extend over 100-1600 m down depositional dip and 500-1500 m along depositional strike. The distribution and amalgamation of minor stratigraphic discontinuities defines linear zones of distinctive facies architecture that are oriented parallel to the paleoshoreline trend. Using the simple assumption that the shoreface-shelf equilibrium profile remained approximately constant for each type of discontinuity throughout shoreface migration (the "Bruun rule"), intra-parasequence facies architecture can be speculatively interpreted in terms of shoreline trajectory, which reflects the balance between sediment supply and accommodation. The resulting interpretations support the notion that shoreline trajectory exerts a strong control on intra-parasequence facies architecture and preservation of the shoreface-shelf profile.