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Recognizing tide- and wave-dominated compound deltaic clinothems in the rock record
Geology ( IF 4.8 ) Pub Date : 2020-12-01 , DOI: 10.1130/g47767.1
Yang Peng 1, 2 , Cornel Olariu 1, 3 , Ronald J. Steel 1
Affiliation  

Many modern deltas exhibit a compound geometry that consists of a shoreline clinoform and a larger subaqueous clinoform connected through a subaqueous platform. Despite the ubiquity of compound clinoforms in modern deltas, very few examples have been documented from the ancient sedimentary record. We present recognition criteria for shelf compound-clinoform systems in both tide- and wave-dominated deltas by integration of ancient and modern examples from multiple types of data. The compound clinothem can be identified by using a combination of: (1) the three-dimensional (3-D) configuration identified in bathymetric or seismic data, (2) bipartite stacked regressive units, consisting of a lower muddy coarsening-to-fining-upward (CUFU) or coarsening-upward (CU) unit (30–100 m thick) and an overlying sandier CU unit (5–30 m thick) (together they represent the subaqueous and shoreline clinoform pair), and (3) distinct facies described herein, though both types of delta have highly bioturbated mudstone and siltstone bottomsets. Tide-dominated deltas have muddy foresets with tidal scours containing tidal rhythmites or inclined heterolithic strata in the subaqueous clinothem overlain by river and tidal deposits of the shoreline clinothem. Wave-dominated deltas show mainly wave-enhanced sediment-gravity-flow (WSGF) beds and some thin hummocky/swaley cross-stratified (HCS/SCS) sandstones toward the top in the subaqueous muddy foreset, and upward-thickening HCS/SCS and trough/planar cross-bedded sandstones interbedded with siltstones in the shoreline clinothem. The subaqueous platform, which links the clinoform couplet, shows evidence of frequent tidal or wave reworking and redeposition. The platform in tide-dominated deltas is characterized by tide-generated heterolithic strata (e.g., bidirectional current-rippled and cross-stratified sandstones, spring and neap tidal bundles, tidal rhythmites) with occasional storm-wave–influenced strata. In contrast, the wave-dominated platform comprises small-scale swales with scours and mud clasts and some WSGF deposits. The proposed criteria can aid in the recognition of compound deltaic clinothems in other basins, particularly those with limited amounts and/or types of data.

中文翻译:

在岩石记录中识别潮汐和波浪为主的复合三角洲倾斜

许多现代三角洲展现出一种复合的几何形状,该几何形状由海岸线的斜形和通过水下平台连接的较大的水下斜形组成。尽管现代三角洲中普遍存在复合斜成岩形式,但从古代沉积记录中却很少记录到这样的例子。通过整合来自多种类型数据的古代和现代实例,我们提出了潮汐和波浪主导三角洲中陆架复合斜体系统的识别标准。可以通过使用以下组合来识别复合的clinothem:(1)在测深或地震数据中确定的三维(3-D)构造,(2)两部分堆叠的回归单元,由下部泥泞的向上粗化至粗化(CUFU)或向上粗化(CU)单元(30–100 m厚)和上覆的桑迪尔CU单元(5–30 m厚)(共同代表水下水体和(3)本文所述的不同相,尽管两种类型的三角洲都具有高度生物扰动的泥岩和粉砂岩底部。潮汐主导型三角洲的泥滩前部充满潮汐冲刷,潮汐冲刷或潮汐节律或倾斜的异质地层位于水下clinothem中,河流和海岸线clinothem的潮汐沉积物覆盖了该地区。波浪主导的三角洲主要表现为波浪强化的沉积物重力流(WSGF)床层,以及在水下浑浊的前部顶部向顶部的一些薄薄的丘陵/带状交叉层状(HCS / SCS)砂岩,在海岸线气候变化中,HCS / SCS和槽/平面交叉层砂岩与粉砂岩互层。连接斜形对联的水下平台显示出经常出现潮汐或波浪返修和再沉积的迹象。潮汐为主的三角洲中的平台的特征是潮汐产生的异质岩性地层(例如,双向潮流波纹状和交叉分层的砂岩,春季潮汐带和潮汐潮汐带,潮汐节律)以及受风暴波影响的地层。相比之下,波浪主导的平台包括带有冲刷,泥屑和一些WSGF沉积物的小鳞片。拟议的标准可以帮助识别其他盆地中的复合三角洲斜面,特别是那些数量和/或数据类型有限的斜面。连接斜对联,显示出经常出现潮汐或波浪返修和再沉积的迹象。潮汐为主的三角洲中的平台的特征是潮汐产生的异质岩层(例如,双向潮流波纹状和交叉分层的砂岩,春季潮汐层和潮汐潮汐层,潮汐节律)以及偶尔受到风暴波影响的地层。相比之下,波浪主导的平台包括带有冲刷,泥屑和一些WSGF沉积物的小鳞片。拟议的标准可以帮助识别其他盆地中的复合三角洲斜面,特别是那些数量有限和/或数据类型有限的三角洲斜面。连接斜对联,显示出经常出现潮汐或波浪返修和再沉积的迹象。潮汐为主的三角洲中的平台的特征是潮汐产生的异质岩性地层(例如,双向潮流波纹状和交叉分层的砂岩,春季潮汐带和潮汐潮汐带,潮汐节律)以及受风暴波影响的地层。相比之下,波浪主导的平台包括带有冲刷,泥屑和一些WSGF沉积物的小鳞片。拟议的标准可以帮助识别其他盆地中的复合三角洲斜面,特别是那些数量有限和/或数据类型有限的三角洲斜面。双向波纹状和交叉分层的砂岩,春季潮汐带和潮汐潮汐带,潮汐节律),偶尔受到风暴波影响的地层。相比之下,波浪主导的平台包括带有冲刷,泥屑和一些WSGF沉积物的小鳞片。拟议的标准可以帮助识别其他盆地中的复合三角洲斜面,特别是那些数量有限和/或数据类型有限的三角洲斜面。双向波纹状和交叉分层的砂岩,春季潮汐带和潮汐潮汐带,潮汐节律),偶尔受到风暴波影响的地层。相比之下,波浪主导的平台包括带有冲刷,泥屑和一些WSGF沉积物的小鳞片。拟议的标准可以帮助识别其他盆地中的复合三角洲斜面,特别是那些数量有限和/或数据类型有限的三角洲斜面。
更新日期:2020-12-20
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