Provenance analysis of IODP Expedition 355 cores in the Laxmi Basin sheds new light on the erosional evolution of the Himalayan belt and its western syntaxis during the Neogene and on large-scale mass-wasting and magmatic events that affected the western continental margin of India in the mid-Miocene and early Paleocene. In the cored Laxmi Basin succession, heavy minerals are far less affected by selective diagenetic dissolution than in foreland-basin sandstones exposed along the Himalayan front. Occurrence of euhedral aegirine and apatite in lower Paleocene mudrocks can be tied to alkaline volcanism affecting the adjacent western Indian margin during the late stage of Deccan activity. In the mid-Miocene Nataraja Slide (the second-largest mass-transport deposit reported from passive margins worldwide), dominant carbonate detritus and depleted heavy-mineral suites (including apatite, garnet, and locally augite or rare aegirine) reveal gravitational failure and sliding of the entire succession of carbonate and siliciclastic Paleogene to lower Neogene strata originally accumulated offshore of the Saurashtra margin of western India. Contrary to previous inferences, reworking of Indus-derived detritus by the slide was negligible. The overlying upper Miocene to lower Pleistocene turbidite package has the same feldspatho-litho-quartzose to litho-feldspatho-quartzose signature of modern Indus fluvio-deltaic sand, indicating that amphibolite-facies metamorphic rocks have been widely exposed in the Himalaya–Karakorum orogen since at least the mid-Miocene. Pleistocene nannofossil oozes with planktonic foraminifera at the top of the fan contain a very subordinate litho-feldspatho-quartzose terrigenous fraction including augitic clinopyroxene, suggesting mixing of dominant biogenic debris with minor detritus contributed both by the Indus River and by a river draining western peninsular India, possibly the paleo-Narmada or the paleo-Tapti.

中文翻译：

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新生代印度洋扇沉积物的来源（IODP站点U1456和U1457）

对拉克西米盆地IODP远征355岩心的物源分析为新近纪期间喜马拉雅带及其西部语法的侵蚀演化以及影响印度西部大陆边缘的大规模大规模浪费和岩浆事件提供了新的线索。中新世中期和古新世早期。在有芯Laxmi盆地演替中，重金属矿物受选择性成岩作用的影响远小于沿喜马拉雅山锋暴露的前陆盆地砂岩。在德肯活动的后期，古新世下层泥岩中的真面目eg庚氨酸和磷灰石的发生可能与碱性火山作用有关，碱性火山作用影响了相邻的西印度边缘。在中新世中期的Nataraja滑坡（据全球被动边缘报道的第二大大规模运输矿床）中，占主导地位的碳酸盐碎屑和贫化的重矿物组合（包括磷灰石，石榴石和局部的辉石或稀有的正丁胺）显示出重力破坏和整个碳酸盐和硅质碎屑古近系的滑动，以降低最初聚集在印度西部索拉什特拉边缘附近的新近纪地层。与先前的推论相反，由载玻片对源自印度河的碎屑的返工可以忽略不计。上层中新世至下更新世浊质包裹体具有与现代印度河藻-三角洲砂岩相同的长石-锂-石英-石英-长石-石英-石英特征，表明自喜马拉雅山-喀喇昆仑造山带以来，斜长岩变质岩已广泛暴露至少是中新世中期。