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首页> 外文期刊>Geological Society of America Bulletin >Cenozoic provenance history of synorogenic conglomerates in western Argentina (Famatina belt):Implications for Central Andean foreland development
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Cenozoic provenance history of synorogenic conglomerates in western Argentina (Famatina belt):Implications for Central Andean foreland development

机译：阿根廷西部（法马蒂纳带）同生砾岩的新生代起源史：对中安第斯前陆发展的启示

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In Famatina,at the modern northern flat-slab segment of the Central Andean belt,synorogenic conglomerate f acies provide a unique opportunity to reconstruct paleogeography and tectonic setting.Stratigraphically constrained provenance analyses record a multi-event history of the Andean foreland and a complex pattern of exhumed uplands,which,in turn,controlled the depocenter history.Western and eastern sources can be differentiated.The western domain was composed of equigranular granitoids and lower and upper Paleozoic volcano-sedimentary and sedimentary units,whereas the eastern domain was mainly formed by porphyrytic granitoids and minor slightly metamorphosed lower Paleozoic clastic rocks.The surrounding regions expose medium- to high-grade metamorphic rocks,which are not recorded in any Cenozoic conglomerate of Famatina.Unroofing sequences can be deduced from the compositional trends.Conglomerate composition and paleocurrent data show input from intraba-sinal sources and important participation of basement since the beginning of the Neogene.We infer an early Miocene broken foreland during deposition of the Del Creston Formation.A significant source inversion,with clasts supplied from the eastern basement domain,is recorded ~2000m from the base,within the middle Miocene Del Abra Formation;reactivation of western granitic thrust sheets occurred by the late middle Miocene and late Miocene,as indicated by provenance studies of the Santo Domingo and El Durazno Formations.In contrast to simple asymmetric foreland models,provenance analysis documents early participation of crystalline rocks,suggesting early development of intrafore-land basement highs within the southern Central Andes.At a regional scale,basement thrusting and associated intermontane basin development were diachronous.This interpretation is supported by broad propagation of basement thrusting from the northern Sierras Pampeanas (and Famatina) toward the central and eastern Sierras Pampeanas between early-middle Miocene and late Miocene-Pliocene time.Early Miocene reconstructions of the Juan Fernandez Ridge position on the Central Andean margin suggest that during this interval,shallow subduction was likely unrelated to oceanic plateau subduction under the Sierras Pampeanas.
机译：在法马蒂纳（Famatina），在安第斯山脉中部现代北部板块部分，成岩砾岩相为重建古地理和构造环境提供了独特的机会。战略上的物源分析记录了安第斯前陆的多事件历史和复杂的格局。西部地区是由等粒花岗岩，上，下古生代火山沉积和沉积单元组成的，而东部地区主要是由斑状花岗岩和次要的轻度变质的下古生界碎屑岩。周围地区暴露出中至高级变质岩，在Famatina的任何新生代砾岩中均未记录。显示基础内和重要因素的输入自新近纪开始以来基底的剥离。我们推断德尔克雷斯顿组沉积期间中新世破碎的前陆。据记录，一个重要的震源反转，由东部基底区域提供了碎屑，距基底约2000m。中新世-德尔阿布拉组;中新世中期和中新世晚期发生了西部花岗岩逆冲片的再活化，如圣多明各和埃尔杜拉兹诺地层的物源研究表明。与简单的不对称前陆模型相反，物源分析证明了晶体的早期参与岩石，表明安第斯中部南部地区陆前地下高点的早期发育。在区域范围内，基底冲断作用和相关的山间盆地发育是逆时针的。这一解释得到了北部塞拉山脉Pampeanas（和Famatina）基底冲断作用的广泛传播的支持。 ）朝早期之间的中东部山脉Pampeanas中新世中期至上新世末期。安第斯中部边缘的胡安·费尔南德斯山脊位置的中新世早期重建表明，在此间隔内，浅俯冲作用可能与山脉中的俯冲作用无关。

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