Time and Mechanism(s) of Accretion of the Laurentia-Derived Argentine Precordillera to Western Gondwana: the Record in the Foreland

阿根廷西北部的Precordillera是一个奇异的Laurentian（北美）地体，它与Gondwana（南美）西部碰撞并被吸积。普遍的共识是，普雷科迪勒拉是从劳伦西亚南部的瓦希托隆起而来的，普雷科迪勒拉可以说是所有已知的外来大陆地体中最受约束的原始位置。因此，前科迪勒拉提供了一个地方来研究大陆板块从一个大陆向另一个大陆转移的机制和速率等基本问题。此外，前科迪勒拉可以作为表征微大陆（小板块）与大陆碰撞的过程和反应的模型。最后，前科迪勒拉从Laurentia向Gondwana转移的历史是全球古地理重建的重要制约因素。即使对阿根廷前科迪勒拉在瓦希托盆地的原始位置和前科迪勒拉与冈瓦纳西部的碰撞达成共识，对碰撞时间的解释也从中晚奥陶世到志留纪-泥盆纪有所不同。每一种解释都承认中晚奥陶世的事件，但这些事件在一些解释中被认为是与冈瓦纳的碰撞，在另一些解释中被认为是与劳伦西亚的断裂。在这项研究中收集的新数据有助于限制前科迪勒拉与冈瓦纳碰撞的时间和机制。本研究整合了前科迪勒拉前陆盆地的沉降和沉积充填历史，并将其与法马蒂纳火山弧和冈瓦纳西部与东部前科迪勒拉岩石之间的大陆缝合带进行了时间和机械联系。具体而言，研究了盆地的沉降史、高起伏断块作为碳酸盐岩浆岩来源的作用、可能的断块对伸展或张拉的意义、火成岩和变质碎屑的物源、碎屑沉积在前科迪勒拉台地上的扩散模式、法玛蒂纳拱和缝合带与盆地沉降和台地沉积的关系以及与南劳伦蒂亚的演替关系。

The Precordillera in northwestern Argentina is an exotic Laurentian (North American) terrane that collided with and was accreted to western Gondwana (South America). General consensus holds that the Precordillera was rifted from the Ouachita embayment of southern Laurentia, and the Precordillera arguably has the best-constrained original location of any known exotic continental terrane. For that reason, the Precordillera provides a place to address fundamental questions of mechanisms and rates of transfer of a continental terrane from one continent to another. In addition, the Precordillera may serve as model for processes and responses that characterize the collision of a microcontinent (small plate) with a continent. Finally, the history of the transfer of the Precordillera from Laurentia to Gondwana is an important constraint on global paleogeographic reconstructions.Even with the consensus both for the original location of the Argentine Precordillera in the Ouachita embayment and for collision of the Precordillera with western Gondwana, interpretations of the time of collision differ from Middle-Late Ordovician to Silurian-Devonian. Middle-Late Ordovician events are recognized in each of the interpretations, but those events are considered to represent collision with Gondwana in some interpretations and to represent rifting from Laurentia in others. New data gathered in this research help to constrain both the timing and mechanism(s) of collision of the Precordillera with Gondwana. This research integrates the history of subsidence and sedimentary filling of the Precordillera foreland basin in the context of temporal and mechanical links to the Famatina volcanic arc and a continental suture zone between the rocks of western Gondwana and the eastern Precordillera. Specifically, the research is examining the subsidence history of the basin, role of high-relief fault blocks as sources of carbonate olistoliths, significance of possible fault blocks for extension or transpression/transtension, provenance of igneous and metamorphic clasts, patterns of clastic sediment dispersal on Precordillera platform, relation of Famatina arch and suture zone to basin subsidence and sediment progradation on platform, and relation of succession to southern Laurentia.