Facies architecture of Miocene subaqueous clinothems of the New Jersey passive margin: Results from IODP-ICDP Expedition 313
Facies architecture of Miocene subaqueous clinothems of the New Jersey passive margin: Results from IODP-ICDP Expedition 313
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DOI：
10.1130/ges01545.1
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发表时间：
2018-04
期刊：
影响因子：
2.5
通讯作者：
J. Proust;H. Pouderoux;H. Ando;S. Hesselbo;D. Hodgson;J. Lofi;M. Rabineau;P. Sugarman
中科院分区：
文献类型：
--
作者：
J. Proust;H. Pouderoux;H. Ando;S. Hesselbo;D. Hodgson;J. Lofi;M. Rabineau;P. Sugarman
在被动边缘保存的大陆侵蚀的横向相关沉积记录被用来重建过去的海平面变化。然而，在许多这些边缘观察到的基本临床发展模式的详细性质仍然知之甚少。本文通过对纽泽西陆架沉积相的描述，对陆架沉积环境和陆架构造的解释，描绘了陆架边缘沉积的成因和分布控制。我们分析了在美国新泽西州大西洋城60公里外的三个地点收集的612个岩心，总长度为1311 m，是在IODP-ICDP第313次探险期间。这三个地点采集了新泽西陆架表层下至中中新世被动边缘沉积物。我们还在三个地点收集了电缆测井资料，并将沉积结构与地震剖面上观察到的几何形状联系起来。观测到的斜形复合体沉积物分布与目前基于地震资料的模型不同，目前的模型预测泥沙含量在向海方向逐渐增加，砂含量逐渐减少。相比之下，我们观察到斜形主要由泥沙和较粗的物质组成，这些物质集中在斜坡的翻转、底部和脚趾处。陆架斜斜顶套是受风暴影响的泥质，而前倾坡是由泥楔组成，主要由低密度浊积岩和碎屑组成。斜层复合体的结构包括一个约30 m厚的斜层单元的复合堆栈，每个斜层单元由四个体系域（TST、HST、FRWST、LST）组成，形成单独的T-R序列。在离易砂的滨面沉积（在新泽西州陆上三角洲平原观察到）40至60公里的海陆构造顶部高地，富泥相的存在以及缺乏陆上侵蚀（和大陆沉积环境）表明，沉积模式涉及陆上三角洲（陆上）为远处的水下三角洲提供食物。在强迫回归期间，陆架边缘三角洲周期性地超越受洪水影响的堆积，新泽西水下三角洲的近海泥楔将沙子带入翻滚，形成大规模的陆架棱柱状环流。斜层复合体发育在平均风暴波基底以下的缓倾平台上，呈斜坡状形态（视倾角为0.75-0.5），水深30-50米，向海40-60公里。它的形状取决于调节和沉积速率之间的平衡。水下三角洲的积累速度比陆上三角洲高，其推进距离和速度是同时期海岸线的三倍。波浪强度（高度、复发间隔）的增加有利于水下三角洲和陆上三角洲的分离，因此，形成了一个平坦的顶部几何形状，洪水事件和河流流量的减少，沉积物粒度的总体递进减小（从序列m5.45开始，大约17.8-17.7 Ma），以及在斜形坡前的沉积速率的增加。所有这些都被认为是可能表征新近纪冰窖世界进入的初步信号。
The preserved, laterally correlative sedimentary record of continental erosion on passive margins has been used to reconstruct past sea level changes. However, the detailed nature of a basic clinothem progradational pattern observed on many of these margins is still poorly known. This paper describes the sedimentary facies and interprets the depositional environments and the architecture of the clinothems of the New Jersey shelf to depict the origin and controls of the distribution of the sediment on the margin. We analyze 612 cores totaling 1311 m in length collected at three sites 60 km offshore Atlantic City, New Jersey, USA during IODP-ICDP Expedition 313. The three sites sampled the Lower to Middle Miocene passive margin sediments of the New Jersey shelf clinothems. We also collected wireline logs at the three sites and tied the sedimentary architecture to the geometry observed on seismic profiles. The observed sediment distribution in the clinoform complex differs from current models based on seismic data, which predict a progressive increase in mud and decrease in sand contents in a seaward direction. In contrast, we observe that the clinoforms are largely composed of muds with sands and coarser material concentrated at the rollover, the bottomset and the toe of the slope. The shelf clinothem topsets are storm-influenced mud whereas the foreset slope is composed of a mud wedge largely dominated by low density turbidites and debrites. The architecture of the clinothem complex includes a composite stack of approximately 30 m thick clinothem units each composed of four systems tracts (TST, HST, FRWST, LST) building individual T-R sequences. The presence of mud-rich facies during highstands on the topset of the clinoform, 40 to 60 km offshore from the sand-prone shoreface deposit (observed in the New Jersey onshore delta plain) and the lack of subaerial erosion (and continental depositional environments) points to a depositional model involving a subaerial delta (onshore) feeding a distant subaqueous delta. During forced regressions, shelf edge deltas periodically overstep the stacks of flood-influenced, offshore-marine mud wedges of the New Jersey subaqueous delta bringing sand to the rollover building up the large-scale shelf-prism clinothems. The clinothem complex develops on a gently dipping platform with a ramp-like morphology (apparent dip of 0.75-0.5) below mean storm wave base, in 30-50 m of water depth, 40-60 km seaward of the coastal area. Its shape depends on the balance between accommodation and sedimentation rates. Subaqueous deltas show higher accumulation rates than their subaerial counterparts and prograde three times further and faster than their contemporaneous shoreline. The increase in the intensity of waves (height, recurrence intervals) favors the separation between subaqueous and subaerial deltas, and as a consequence, the formation of a flat topset geometry, the decrease in flood events, and fluvial discharge, the overall progressive decrease in sediment grain size (from sequence m5.45, approximately 17.8-17.7 Ma, onwards) as well as the increase in sedimentation rates on the foresets of the clinoforms. All of these are recognized as preliminary signals that might characterize the entry in the Neogene icehouse world.