The Austral-Magallanes Basin covers the southernmost region of Patagonia, South America. South of Lago Argentino, the Calafate Formation documents part of the foreland stage of the evolution of this basin. Here, sandstones from the Calafate Formation were characterized using petrographical, X-ray diffraction (XRD) and geochemical data in order to establish their tectonic setting and sediment source areas. Based on our results, three intervals (lower, middle, and upper) were distinguished according to their composition. The lower and upper intervals are composed of felsic volcanic lithics, abundant quartz and orthoclase. A shift in the composition was observed in the middle interval, with an increase in the modal abundance of plagioclase as well as other accessory minerals such as pyroxene. In addition, XRD data reveal that the middle interval is dominated by smectite in the clay-fraction, whereas the lower and upper intervals present mixed-layer chlorite-smectite and chlorite assemblages. Similar differences are observed using major and trace elements: data from the lower and upper intervals point to source rocks of intermediate to acid composition, while the middle interval had source rocks of intermediate composition and a lower degree of weathering. With regard to the provenance studies, the three intervals have a strong affinity to intermediate compositions of the Tobífera Formation (El Quemado Complex) and with the diorite/andesite of the Patagonian Batholith, which implies an exclusive contribution from the western edge of the basin. However, the shift in the composition towards the middle interval indicates a sediment supply from the juvenile Andean arc, suggesting contemporaneous magmatic activity during the deposition of the Calafate Formation sandstones. This peak of magmatic activity may have been caused by an eastward migration of the arc, driven by a switch in the tectonic setting south of 48°S.

Austral-Magallanes 盆地覆盖了南美洲巴塔哥尼亚的最南端地区。在阿根廷湖以南，卡拉法特组记录了该盆地演化的前陆阶段的一部分。在这里，来自 Calafate 组的砂岩使用岩相学、X 射线衍射 (XRD) 和地球化学数据进行了表征，以确定它们的构造环境和沉积物源区。根据我们的结果，根据它们的组成区分了三个区间（下、中和上）。下、上层段由长英质火山岩屑、丰富的石英和正长石组成。在中间区间观察到成分发生变化，斜长石以及辉石等其他副矿物的模态丰度增加。此外，XRD 数据显示，中层段以粘土组分中的蒙脱石为主，而下层和上层层呈现绿泥石-蒙脱石和绿泥石组合的混合层。使用主量元素和微量元素观察到类似的差异：来自下层和上层的数据指向中酸性成分的烃源岩，而中层具有中等成分和较低风化程度的烃源岩。关于物源研究，这三个层段与 Tobífera 组（El Quemado Complex）的中间成分和巴塔哥尼亚基石的闪长岩/安山岩具有很强的亲和力，这意味着盆地西部边缘的独特贡献。然而，成分向中间层段的转变表明来自幼年安第斯弧的沉积物供应，表明在卡拉法特组砂岩沉积期间存在同期岩浆活动。这种岩浆活动的高峰可能是由弧向东迁移引起的，由 48°S 以南的构造环境中的转换驱动。