Central Argentina from the Pampean flat-slab segment to northern Patagonia (27°–41°S) represents a classic example of a broken retroarc basin with strong tectonic and climatic control on fluvial sediment transport. Combined with previous research focused on coastal sediments, this actualistic provenance study uses framework petrography and heavy-mineral data to trace multistep dispersal of volcaniclastic detritus first eastwards across central Argentina for up to ca. 1,500 km and next northwards for another 760 km along the Atlantic coast. Although detritus generated in the Andes is largely derived from mesosilicic volcanic rocks of the cordillera, its compositional signatures reflect different tectono-stratigraphic levels of the orogen uplifted along strike in response to varying subduction geometry as well as different character and crystallization condition of arc magmas through time and space. River sand, thus, changes from feldspatho-litho-quartzose or litho-feldspatho-quartzose in the north, where sedimentary detritus is more common, to mostly quartzo-feldspatho-lithic in the centre and to feldspatho-lithic in the south, where volcanic detritus is dominant. The transparent-heavy-mineral suite changes markedly from amphibole ≫ clinopyroxene > orthopyroxene in the north, to amphibole ≈ clinopyroxene ≈ orthopyroxene in the centre and to orthopyroxene ≥ clinopyroxene ≫ amphibole in the south. In the presently dry climate, fluvial discharge is drastically reduced to the point that even the Desaguadero trunk river has become endorheic and orogenic detritus is dumped in the retroarc basin, reworked by winds and temporarily accumulated in dune fields. During the Quaternary, instead, much larger amounts of water were released by melting of the Cordilleran ice sheet or during pluvial events. The sediment-laden waters of the Desaguadero and Colorado rivers then rushed from the tract of the Andes with greatest topographic and structural elevation, fostering alluvial fans inland and flowing in much larger valleys than today towards the Atlantic Ocean. Sand and gravel supply to the coast was high enough not only to promote rapid progradation of large deltaic lobes but also to feed a cell of littoral sediment transport extending as far north as the Río de la Plata estuary.

中文翻译：

---

受俯冲几何和气候变化控制的跨大陆弧后沉积物路径（阿根廷安第斯山脉中部和南部）

阿根廷中部从 Pampean 平板段到巴塔哥尼亚北部 (27°–41°S) 代表了一个典型的弧后盆地破碎的例子，该盆地对河流沉积物的输送具有强烈的构造和气候控制。结合之前对沿海沉积物的研究，这项现实的物源研究使用框架岩相学和重矿物数据来追踪火山碎屑碎屑的多步扩散，首先向东穿过阿根廷中部长达约 20 年。1,500 公里，然后再向北行驶 760 公里，沿着大西洋沿岸。尽管安第斯山脉产生的碎屑主要来自于山脉的中硅质火山岩，其成分特征反映了造山带沿走向抬升的不同构造地层水平，以响应不同的俯冲几何形状以及弧形岩浆随时间和空间的不同特征和结晶条件。因此，河砂从北部的长石-岩质石英或岩质-长石-石英岩（沉积碎屑更常见）转变为中心的大部分石英-长石-岩屑和南部的长石-石屑，其中火山岩碎屑占主导地位。透明重矿物组从北部的角闪石≫单斜辉石>斜方辉石到中部的角闪石≈单斜辉石≈斜方辉石和南部的斜方辉石≥单斜辉石≫角闪石。在现在干燥的气候下，河流流量急剧减少，以至于连 Desaguadero 干河都变成内流，造山碎屑被倾倒在弧后盆地，被风重新加工并暂时堆积在沙丘中。相反，在第四纪期间，科迪勒拉冰盖融化或雨洪事件释放了大量的水。德萨瓜德罗河和科罗拉多河中富含沉积物的水域随后从地形和结构海拔最高的安第斯山脉中涌出，催生了内陆冲积扇，并在比今天更大的山谷中流向大西洋。海岸的沙子和砾石供应量足够高，不仅可以促进大型三角洲裂片的快速进积，而且还可以为向北延伸至拉普拉塔河口的沿海沉积物输送单元提供养料。