How to make a 350-m-thick lowstand systems tract in 17,000 years: The Late Pleistocene Po River (Italy) lowstand wedge
How to make a 350-m-thick lowstand systems tract in 17,000 years: The Late Pleistocene Po River (Italy) lowstand wedge
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DOI：
10.1130/g38848.1
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发表时间：
2017-04
期刊：
影响因子：
5.8
通讯作者：
C. Pellegrini;V. Maselli;F. Gamberi;A. Asioli;K. Bohacs;T. Drexler;F. Trincardi
中科院分区：
文献类型：
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作者：
C. Pellegrini;V. Maselli;F. Gamberi;A. Asioli;K. Bohacs;T. Drexler;F. Trincardi
与末次盛冰期相关的波河低洼楔（意大利）350米厚的序列（沉积时间超过17ky）包含物理尺度上的地层结构，通常归因于更长的时间尺度，具有复杂的、系统变化的内部斜层特征。本研究通过将地震反射数据与沉积属性、微古生物学、区域气候、海平面变化以及仅在第四纪层序中才可能实现的高分辨率年龄控制相结合，研究了斜层叠加模式和控制因素。根据顶集几何形状、陆架边缘和上覆点轨迹、内部地震相和解释底底沉积，将其划分为3种类型：A型为中度顶集沉积、陆架边缘上升轨迹和块体搬运型底底沉积；B型为侵蚀顶集、下降陆架边缘轨迹和底集分流河道—叶状杂岩；C型具有最大的顶集叠加、上升的陆架边缘轨迹和一致的底集。A型和C型环流表现出沉积物旁路和向盆地输送的减少，而B型环流则与沉积物从陆架向较深水域输出的增加有关。古大陆边缘尺度系统对可容纳性和沉积物供应的高频变化的响应时间可能短至几个世纪，这表明古大陆边缘尺度系统对可容纳性和沉积物供应的响应时间可能短至几个世纪。(2)即使是千禧年至百年尺度的地层单元也能记录到同种异体控制的实质性影响；(3)即使在短时间的低水位体系域，砂质沉积也可以被划分。
The 350-m-thick succession of the Po River lowstand wedge (Italy) associated with the Last Glacial Maximum (deposited over ∼17 k.y) contains stratal architecture at a physical scale commonly attributed to much longer time scales, with complex, systematically varying internal clinothem characteristics. This study investigated clinothem stacking patterns and controls through the integration of seismic reflection data with sediment attributes, micropaleontology, regional climate, eustacy, and high-resolution age control possible only in Quaternary sequences. Three clinothem types are differentiated based on topset geometry, shelf-edge and onlap-point trajectory, internal seismic facies, and interpreted bottomset deposits: type A has moderate topset aggradation, ascending shelf-edge trajectory, and mass-transport bottomset deposits; type B has eroded topset, descending shelf-edge trajectory, and bottomset distributary channel-lobe complexes; and type C has maximal topset aggradation, ascending shelf-edge trajectory, and concordant bottomsets. Type A and C clinothems exhibit reduced sediment bypass and delivery to the basin, whereas type B clinothems are associated with short intervals of increased sediment export from the shelf to deeper water. Clinothems individually span a range of 0.4–4.7 k.y., contemporaneous with significant eustatic and climate changes, but their stacking patterns resemble those found in ancient successions and ascribed to significantly longer durations, indicating that (1) the response time of ancient continental margin–scale systems to high-frequency variations in accommodation and sediment supply could be as short as centuries, (2) even millennial- to centennial-scale stratal units can record substantial influence of allogenic controls, and (3) sandy deposits can be compartmentalized even in a short-duration lowstand systems tract.