page_title: Colorado Basin, Argentina
section_title: Basin evolution
hierarchical_section_title: Colorado Basin, Argentina / Description / Basin evolution
caption_attribution_description: English: Paleogeographic reconstruction of the Pangea supercontinent at the Permo-Triassic Boundary (250 Ma). Top panel: Synthetic APWP for Africa (the south paleomagnetic poles are shown with their 95% uncertainty ovals). The red dot highlights the 250 Ma paleomagnetic pole. APWP data are from Torsvik et al. (2012). Middle panel: All continents are assembled in the Pangea configuration at 250 Ma using the estimates of their relative motions, with Africa kept fixed in its present position. The red triangle shows the position of the Euler pole and the red arrow indicates the rotation that would reconstruct the paleomagnetic pole to the south geographic pole. Bottom panel: The Euler rotation has been applied to Pangea, which is now reconstructed paleogeographically. The longitude is arbitrary set to minimize the longitudinal motion of Africa since 250 Ma.
context_page_description: The Colorado Basin is a sedimentary basin located in northeastern Argentina. The basin stretches across an area of approximately 180,000 square kilometres, of which 37,000 square kilometres onshore in the southern Buenos Aires Province and the easternmost Río Negro Province extending offshore in the South Atlantic Ocean.
  The basin comprises a sedimentary succession dating from the Permian and Early Cretaceous to the Quaternary, representing the passive margin tectonic phase of the basin history. The Mesozoic rifting in the basin resulted from the break-up of Pangea and the formation of the South Atlantic. Long hiatuses exist in the succession.
  The basin is of paleontological significance for hosting fossiliferous stratigraphic units dating to the Late Miocene. The Arroyo Chasicó Formation defines the Chasicoan South American land mammal age and contains a rich mammal and other vertebrate fauna. The contemporaneous Cerro Azul Formation has provided fossil rodents, armadillos and opossums. The Middle to Late Miocene Gran Bajo del Gualicho Formation contains vertebrate fossils of the cetacean Preaulophyseter gualichensis.
context_section_description: The basin started forming in the Middle to Late Jurassic with the break-up of Pangea and the formation of the Southern Atlantic. The main rifting took place in the Early Cretaceous. The pre-rift sequence of the basin comprises the Pennsylvanian Lolén Formation of the Ventana Group, and the Sauce Grande, Piedra Azul, Bonete and Tunas Formations of the Pillahuincó Group, dating to the Permian. During the late Paleozoic, the Colorado Basin was located in the south polar region, causing a sequence of glacial deposits in the basin. These deposits were mostly sourced from the African basin, the Karoo and Kalahari Basins. The Early Permian sediments are characterized by the presence of diamictites. A transgression in the Permian led to the deposition of the Piedra Azul Formation. The succession contains several hiatuses, dating to the Triassic and Early Jurassic, Albian and Paleogene.
  The early Mesozoic succession is missing, and the main rifting phase happened in the Barremian and Aptian, around 120 million years ago, represented in the Fortín Formation. The post-rift sag stage dates to the early Late Cretaceous leading to the deposition of the alluvial and fluvial sediments of the Colorado Formation. The drift stage is represented by the Pedro Luro Formation. The later Cenozoic succession is characteristic of a terrestrial passive margin setting and comprises the Paleocene Elvira, Middle Miocene Barranca Final Formation, and the Middle to Late Miocene Gran Bajo de Gualicho Formation. This formation in most of the basin is overlain by the Río Negro Formation. The Late Miocene succession in the westernmost area of the basin is represented by the Arroyo Chasicó and eolian Cerro Azul Formations, cropping out in the northern onshore part of the basin. This sequence is covered by the Late Miocene to Early Pliocene eolian and fluvial Río Negro Formation, outcropping in a thin band along the eponymous river.
caption: Pangea in the Permian (~250 Ma). The Colorado Basin experiences glaciations and a marine transgressive phase in the south polar region.
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