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Monsoon controls on sediment generation and transport: Mass budget and provenance constraints from the Indus River catchment, delta and submarine fan over tectonic and multimillennial timescales
Earth-Science Reviews ( IF 10.8 ) Pub Date : 2021-05-23 , DOI: 10.1016/j.earscirev.2021.103682
Peter D. Clift , Tara N. Jonell

How well do deep-sea sedimentary archives track erosion in upland sources, driven by climatic change or tectonic forcing? Located on the western edge of South Asian monsoon influence, the Indus River system is particularly sensitive to variations in monsoon rainfall and thus provides a unique opportunity to estimate the nature of sedimentary signal propagation (i.e., recognizable pulses of sediment) through a large river basin under different climatic conditions. In this review we examine the impact that changing monsoon rainfall has had on NW Himalayan landscapes and its foreland since the middle Miocene. Rates of erosion are linked to summer monsoon rains over tectonic timescales but patterns of erosion are more explicitly linked to tectonically-driven rock uplift. Positive feedback between rock uplift and orographic precipitation drives increased erosion and transport from the Lesser Himalaya since the Miocene. After 2 Ma, erosion increasingly shifts to the Inner Lesser Himalaya. As defined multiproxy evidence, strong monsoon rainfall intervals broadly result in increased erosion and faster sediment transport together with increased chemical weathering, although the latter is further linked with global temperature and to the magnitude of sediment recycling within the routing system. We estimate that during the Holocene, most sediment (67–89% of the total ~6000 km3 or 16.3 x 1012 t) delivered to the ocean was sourced either from direct bedrock erosion through channel incision linked to higher discharge or from remobilized, recycled glacial sediment initially deposited during the Last Glacial Maximum (LGM). Post-LGM sediment is primarily stored within the delta plain and shelf clinoform systems. Over the last 14 kyr, average mass delivery rates (936–1404 Mt/y) are much higher than pre-damming estimates (pre-1940s; 250–300 Mt/y). To reconcile observations with pre-damming estimates, high sediment supply rates, probably during strong monsoon intervals over the early Holocene, are required. Long-term rates were high (182273 Mt/y) during a middle Miocene strong monsoon interval. Quaternary Indus submarine fan sedimentation is limited to sea level lowstands, at which times shelf and delta sediment is eroded and reworked into deep water. As a result, and for at least the past 2–3 m.y., most sediment delivered to the Indus submarine fan was initially eroded from bedrock during strong summer monsoon intervals but deposited into the fan under weak monsoon intervals. During the most recent sea level lowstand, only ~24% of sediment deposited in the fan was derived from synchronous onshore bedrock erosion, with the remaining accounted for by recycled terrace, floodplain and shelf clinoform system sediment. Variations in monsoon intensity over the last glacial cycle strongly impact the locus of onshore erosion, with increased relative Himalayan bedrock erosion during times of strong, wet monsoon intervals and increased Karakoram bedrock erosion during drier glacial intervals.



中文翻译:

季风对沉积物产生和输送的控制:在构造和多年以来的时间尺度上,来自印度河集水区,三角洲和海底扇的大量预算和物源限制

在气候变化或构造强迫的驱动下,深海沉积档案追踪陆地资源侵蚀的情况如何?印度河系统位于南亚季风影响的西部边缘,对季风降雨的变化特别敏感,因此提供了一个独特的机会来估算通过大河流域的沉积信号传播的性质(即可识别的沉积物脉动)。在不同的气候条件下。在这篇综述中,我们研究了自中新世中期以来,季风降雨变化对喜马拉雅西北部景观及其前陆的影响。侵蚀速率与构造时间尺度上的夏季季风降雨有关,但侵蚀方式与构造驱动的岩石隆升更为明确地相关。自中新世以来,岩石的隆升与地形降水之间的正反馈推动了小喜马拉雅山的侵蚀和运移增加。2 Ma之后,侵蚀越来越多地转移到喜马拉雅山内。根据确定的多代理证据,强季风降雨间隔广泛地导致侵蚀加剧和更快的泥沙输送以及化学风化的增加,尽管后者与全球温度和路由系统内泥沙循环的程度进一步相关。我们估计,在全新世期间,大部分沉积物(约6000 km占总沉积量的67–89%强烈的季风降雨间隔广泛地导致侵蚀加剧和更快的泥沙输送以及化学风化,尽管后者与全球温度和路线系统内的泥沙循环量进一步相关。我们估计,在全新世期间,大部分沉积物(约6000 km占总沉积量的67–89%强烈的季风降雨间隔广泛地导致侵蚀加剧和更快的泥沙输送以及化学风化,尽管后者与全球温度和路线系统内的泥沙循环量进一步相关。我们估计,在全新世期间,大部分沉积物(约6000 km占总沉积量的67–89%3或16.3 x 10 12t)输送到海洋的来源是直接基岩侵蚀,通过与更高排放量相关的河道切口或最初在上次冰河最高期(LGM)期间沉积的可移动,回收的冰川沉积物。LGM后的沉积物主要存储在三角洲平原和陆架斜形系统中。在过去的14年里,平均质量输送速度(936-1404吨/年)远高于筑坝前的估算值(1940年代前; 250-300吨/年)。为了使观测结果与大坝前的估计值相吻合,可能需要在全新世早期强烈的季风间隔期间提供较高的沉积物供应速率。在中新世强季风间隔期间,长期率很高(182273 Mt / y)。第四纪印度洋海底扇沉积仅限于海平面低位,在这段时间,陆架和三角洲的沉积物被侵蚀并重新加工成深水。结果,至少在过去的2-3 my内,输送到印度河海底扇的大部分沉积物最初在夏季风强时间隔期间从基岩上被侵蚀,但在弱季风间隔时被沉积到风扇中。在最近的海平面低位期间,仅约24%的沉积在扇中的沉积物来自同步陆上基岩侵蚀,其余部分由可回收的阶地,洪泛平原和陆架斜状系统沉积物构成。在最后一个冰川周期,季风强度的变化强烈影响了陆上侵蚀的轨迹,在强烈的湿季风间隔期间,喜马拉雅基岩的相对侵蚀增加,而在较干燥的冰川间隔期间,喀喇昆仑基岩的侵蚀增加。至少在过去的2-3年间,输送到印度河海底扇的大部分沉积物最初在强夏季风间隔期间从基岩中侵蚀,但在弱季风间隔期间沉积到风扇中。在最近的海平面低位期间,仅约24%的沉积在扇中的沉积物来自同步陆上基岩侵蚀,其余部分由可回收的阶地,洪泛平原和陆架斜状系统沉积物构成。在最后一个冰川周期,季风强度的变化强烈影响了陆上侵蚀的轨迹,在强烈的湿季风间隔期间,喜马拉雅基岩的相对侵蚀增加,而在较干燥的冰川间隔期间,喀喇昆仑基岩的侵蚀增加。至少在过去的2-3年间,输送到印度河海底扇的大部分沉积物最初在强夏季风间隔期间从基岩中侵蚀,但在弱季风间隔期间沉积到风扇中。在最近的海平面低位期间,仅约24%的沉积在扇中的沉积物来自同步陆上基岩侵蚀,其余部分由可回收的阶地,洪泛平原和陆架斜状系统沉积物构成。在最后一个冰川周期,季风强度的变化强烈影响了陆上侵蚀的轨迹,在强烈的湿季风间隔期间,喜马拉雅基岩的相对侵蚀增加,而在较干燥的冰川间隔期间,喀喇昆仑基岩的侵蚀增加。输送到印度河海底扇的大多数沉积物最初在夏季风强时间隔从基岩上被侵蚀,但在弱季风间隔时被沉积到风扇中。在最近的海平面低位期间,仅约24%的沉积在扇中的沉积物来自同步陆上基岩侵蚀,其余部分由可回收的阶地,洪泛平原和陆架斜状系统沉积物构成。在最后一个冰川周期,季风强度的变化强烈影响了陆上侵蚀的轨迹,在强烈的湿季风间隔期间,喜马拉雅基岩的相对侵蚀增加,而在较干燥的冰川间隔期间,喀喇昆仑基岩的侵蚀增加。输送到印度河海底扇的大多数沉积物最初在夏季风强时间隔从基岩上被侵蚀,但在弱季风间隔时被沉积到风扇中。在最近的海平面低位期间,仅约24%的沉积在扇中的沉积物来自同步陆上基岩侵蚀,其余部分由可回收的阶地,洪泛平原和陆架斜状系统沉积物构成。在最后一个冰川周期,季风强度的变化强烈影响了陆上侵蚀的轨迹,在强烈的湿季风间隔期间,喜马拉雅基岩的相对侵蚀增加,而在较干燥的冰川间隔期间,喀喇昆仑基岩的侵蚀增加。风机中只有约24%的沉积物来自同步陆上基岩侵蚀,其余的则来自可回收的阶地,洪泛区和陆架斜状系统沉积物。在最后一个冰川周期,季风强度的变化强烈影响了陆上侵蚀的轨迹,在强烈的湿季风间隔期间,喜马拉雅基岩的相对侵蚀增加,而在较干燥的冰川间隔期间,喀喇昆仑基岩的侵蚀增加。风机中只有约24%的沉积物来自同步陆上基岩侵蚀,其余的则来自可回收的阶地,洪泛区和陆架斜状系统沉积物。在最后一个冰川周期,季风强度的变化强烈影响了陆上侵蚀的轨迹,在强烈的湿季风间隔期间,喜马拉雅基岩的相对侵蚀增加,而在较干燥的冰川间隔期间,喀喇昆仑基岩的侵蚀增加。

更新日期:2021-05-27
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