The Late Cretaceous-Cenozoic transgressions in Patagonia and the Fuegian Andes: foraminifera, palaeoecology, and palaeogeography

Abstract

In southernmost South America, several ephemeral Atlantic transgressions flooded the Patagonian Platform: in the Maastrichtian‐Danian, late Mid‐Eocene, Late Oligocene‐Early Miocene, and Middle Miocene; only in the Fuegian Andes did marine conditions remain continuously from the Maastrichtian up to the Middle Miocene. In the Maastrichtian, the calcareous foraminiferal benthic assemblages contain endemic species, and most of them disappear in the Cretaceous–Palaeogene transition. The Palaeocene carries the extinct cosmopolitan Midway type assemblage with few endemic taxa such as Buliminella isabelleana, and the genera Antarcticella and Boltovskoyella. The Palaeocene/Eocene turnover gives room to assemblages of modern and marked Austral aspect: Elphidiidae dominates in shallow environments, including genera endemic to high and mid‐high southern latitudes such as Cribrorotalia. The Late Middle Eocene transgression is characterized by large nodosarids in the Fuegian area and the spreading of Elphidium saginatum. The Late Oligocene transgression is of limited extension and shallow waters, with abundant Buccella and the conspicuous genus Discorotalia. The Early Miocene transgression carries the extinct and typical Antarctic genus Ammoelphidiella and witnesses the origin of the modern Patagonian coastal assemblage, characterized by its pauperism and the dominance of the genus Buccella. The Middle Miocene transgression covers mainly northern Argentina. Considering that the late Middle Eocene and Middle Miocene transgressions are coeval with relative climatic optima, and in comparison with assemblages at similar palaeolatitudes elsewhere in the Southern Hemisphere, the absence of larger foraminifera or thermophilic forms in the Patagonian and Fuegian assemblages is outstanding. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 269–288. En el extremo austral de América del Sur, varias transgresiones efímeras inundaron la Plataforma Patagónica: en el Maastrichtiano‐Daniano, Eoceno Medio Tardío, Oligoceno Tardío‐Mioceno Temprano, y en el Mioceno Medio; sólo en los Andes Fueguinos las condiciones marinas permanecieron desde el Maastrichtiano hasta el Mioceno Medio. En el Maastrichtiano, las asociaciones de foraminíferos bentónicos contienen especies calcáreas endémicas, que en su mayoría desaparecen en la transición Cretácico/Paleógeno. El Paleoceno porta la asociación cosmopolita extinta del tipo Midway, con pocos taxones endémicos tales como Buliminella isabelleana, y los géneros Antarcticella y Boltovskoyella. El recambio del límite Paleoceno/Eoceno da lugar a asociaciones de aspecto moderno y marcadamente austral: los Elphidiidae dominan en los ambientes someros, incluyendo géneros endémicos de altas y medias altas latitudes australes tales como Cribrorotalia. La transgresión del Eoceno Medio Tardío está caracterizada por grandes nodosáridos en el área fueguina y por la dispersión de Elphidium saginatum. La transgresión del Oligoceno Tardío, de limitada extensión y de aguas someras...

Paleogene calcareous nannofossil biostratigraphy for two boreholes in the eastern Austral Basin, Patagonia, Argentina

“…Discoasters are well known warm-water indicators, common in the low to middle paleolatitudes. The presence of these forms only in those samples is consistent with the proposal of the end of the warm period at 39 Ma (Malumián, 1999;Malumián and Jannou, 2010;Malumián and Náñez, 2011;Ronchi and Angelozzi, 1994). The lithology of this succession in the three boreholes starts with conglomerate-sandstones or sandstones that in the upper levels yield some intercalated silty-sandstones and grey to black claystones.…”

“…Malumián (1990) found Campo Bola Formation to be lithologically and micropaleontologically equivalent to Man Aike Formation (Furque, 1973) and he proposed that the latter is the senior synonym of Campo Bola Formation. In subsequent studies (Malumián, 1999;Malumián and Náñez, 2011) retained Campo Bola Formation only for the Late Cretaceous-Paleocene subsurface rocks in the eastern Santa Cruz Province. However, two disconformities observed between the Late Cretaceous-Early Paleocene and the Middle Paleocene-Early to Middle Eocene (Concheyro and Angelozzi, 2002;Pérez Panera, 2009;Ronchi and Angelozzi, 1994) suggests that if the name Campo Bola Formation should be retained it must be restricted to the Paleocene.…”

“…After an erosional continental interval characterized by a marine regression and magmatic activity during the Early and Middle Eocene (Malumián, 1999), a new transgression occurred during late Middle Eocene to Late Eocene (Malumián and Náñez, 2011). In the Cordilleran region, thick sequences representing a shallow-interior-marine to estuarine environment were deposited (Malumián, 1999): in Lago Cardiel to Lago Argentino area, these rocks are Eocene in age and assigned to the Man Aike Formation (Concheyro, 1991(Concheyro, , 1995Malumián, 1990Malumián, , 1999Casadío et al, 2009), whereas in the Río Turbio area, they belong to Río Turbio Formation.…”

“…Marine sedimentation during this cycle is highly reduced and restricted to the Cabo Peña and San Julián formations that crop out in Isla Tierra del Fuego and in eastern Santa Cruz Province respectively. These rocks yielded a cold-water, Early Oligocene microfauna (Náñez, 1990), although the San Julián Formation is now considered to be Late Oligocene (Malumián and Náñez, 2011). In most parts of the basin this cycle consists of continental conglomerates known as the Río Guillermo Formation in the Río Turbio area and the Tchat-Chii Formation in Isla Tierra del Fuego (Malumián, 1999).…”

Depósitos burdigalianos de la Formación Santa Cruz en Sierra Baguales, Cuenca Austral (Magallanes): Edad, ambiente de deposición y vertebrados fósiles.

“…Important climate changes related to an increase in the global temperature (Zachos et al, 2008), eustatic sea-level fluctuations (Miller et al, 2005), and large scale geotectonic events leading to the main uplift of the Andes (Ramos and Alemán, 2000), left a strong imprint on the southern biota Odreman Rivas, 1971, Pascual et al, 1996;Ortiz-Jaureguizar and Cladera, 2006). General information of this epoch largely comes from Argentinian Patagonia, where widespread marine and continental sedimentary deposits represent the main component of the Neogene stratigraphic succession (Feruglio, 1938(Feruglio, , 1944(Feruglio, , 1949a(Feruglio, , 1949b(Feruglio, , 1950Hatcher, 1900;Pascual et al, 1996;Nullo and Combina, 2002;Malumián and Náñez, 2011). Outcrops of contemporaneous Early Miocene rocks in southern Chubut and the Santa Cruz Province of Argentina have yielded a wealth of beautifully preserved fossils, making this epoch also a cornerstone of the many evolutionary hypotheses proposed since the pioneering work of the well-known Argentinean palaeontologists Florentino and Carlos Ameghino at the end of the 19 th century (Ameghino, 1887(Ameghino, , 1889(Ameghino, , 1900(Ameghino, -1902(Ameghino, , 1902(Ameghino, , 1904(Ameghino, , 1906.…”