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In recent decades, Miocene marine transgressions in South America have sparked ongoing debates concerning their boundaries, number of events, regional connectivity, and the existence of an epicontinental sea formed during the Andean orogeny. The bed-by-bed analysis of the Late Miocene Paraná Formation deposits in Entre Ríos Province (Argentina) allow defining six facies associations: (i) beach ridge, (ii) tidal inlet channel and washover fan, (iii) outer estuarine bioherms, (iv) central estuary, (v) tidal bar and sandflat, and (vi) tidal mudflat and creek deposits. Architectural and stacking pattern analyses reveal transgressive-regressive sequences typical of the coastal strip, encompassing shallow marine to estuarine sub-environments. The analysis identified diverse ecological guilds, including bivalve and gastropod assemblages in bioherms, and crustacean traces in tidal flats. Regressive units are characterized by wave-dominated shoreface deposits, while transgressive units comprise fine-grained estuarine deposits interbedded with bioclastic sandstones and storm deposits. The paleoenvironmental and paleoecological data indicate normal salinity marine environments with macroinvertebrates and estuarine components and suggesting tropical brackish conditions. Plant remains point to a range of vegetative communities, including mangroves, palm forests, grasslands, humid riparian forests, and dry upland forests, reflecting tropical to subtropical and humid to semiarid environments. This study concludes that the Paraná Formation correspond to a third-order transgressive system tract influenced by the Miocene Paranaense Sea. The basin-scale implications suggest that the distal Chaco-Paraná basin was affected by eustatic changes due to its low accommodation and topographic relief. The Chaco-Paraná foreland basin's evolution was driven by interactions between tectonic, climatic, and eustatic processes. The comprehensive analysis of sedimentary and fossil records provides a detailed paleogeographic reconstruction of the Miocene marine transgression in southern South America. • Estuarine to shallow marine depositional environments identified in the Paraná Formation. • Integrated stratigraphic, depositional and paleoecological data for the reconstruction of the Paraná Formation. • Proposal of a sequential stratigraphic model for the beginning of the Chaco-Paraná foreland basin during the Cenozoic. • Tectonic, eustatic and climatic influences on the regional development of the Central Andes of South America are discussed. [ABSTRACT FROM AUTHOR]

We present the first taphonomic analysis on basal sauropodomorph dinosaur remains from the Los Colorados Formation. We analyzed 22 bone samples with X-ray diffractometry, three of these in petrographic sections and one of them in SEM. In this article we recognize the taphonomic processes (biostratinomic and fossil-diagenetic) involved in the genesis of the 'La Esquina Local Fauna'. Regarding fossil diagenesis, it was possible to recognize the different processes that acted on the bone remains. In this sense, we analyzed different types of fracture present in the bones and their relationship with expansion generated by changes in the volume of minerals (for example, carbonates, gypsum and anhydrite). Finally, the importance of more taphonomic studies throughout the Los Colorados Formation is highlighted in order to better understand the vertebrate fossil record it contains. • Sauropodomorph bones were affected by different taphonomic processes. • At least three types of fractures associated with volume changes of minerals. • The fractures analyzed in the bones are of fossil-diagenetic origin. • The fossil record of vertebrate remains is found in well-developed overbank/floodplain deposits and rarely within fluvial channel facies. • Major bone loss can be explained by actual exhumation. [ABSTRACT FROM AUTHOR]

The Cueva del Milodón (CdM, southern Chile), has been explored repeatedly since the end of the 19th century. Many institutions in the world house specimens from CdM, standing out the mylodontid sloths. Until now, 36 14C measurements were performed on these remains using equivalent methodologies, Gas Proportional Counter (GPC), Liquid Scintillation Counting (LSC) and Accelerator Mass Spectrometry (AMS). The goals of this work are to review published dates, report two new radiocarbon dates made by us, and discuss the occurrence of the mylodonts in southernmost South America in a glacial context and its possible coexistence with humans. Among the published 16 direct (hair, skin, bone) and 20 indirect (excrement) 14C dates, 13 and 18 are considered here as reliable, respectively. Dates considered unreliable presented several issues (transcription errors, duplicate dates, misidentified samples, etc.), being excluded from the analysis to avoid further misunderstandings. Two new 14C dates performed by us on pieces housed in the Museo de La Plata (skin - AMS) and (bone - LSC) were added, making a total of 33 valid dates. A remarkable amplitude in the radiocarbon ages of the mylodont remains in CdM is evidenced, showing a range of values from ∼14,000 BP to ∼9800 BP, since upper Pleistocene ("Tarantian") to early Holocene (Greenlandian). However, the direct dates of maximum confidence available show a strong modal representation in the Upper Pleistocene. Climate evidence available for this period indicates a complex interplay of deglaciation and brief cold reversals, but suggests that mylodonts could take advantage of their dense fur and thick skin, large body mass and suitability to live in caves to prosper in such cold and humid environments. Finally, evidence supporting coexistence of mylodonts and humans is briefly discussed. Image 1 • Mylodontid ground sloth mummified skin from Cueva del Milodón, Chile, was analized. • Two new radiocarbonic dates were performed on this remain. • Previous dates of ground sloth remains from the same place were reviewed. • More reliable dates suggest ground sloth presence around upper Pleistocene. • Paleoclimatic context was reviewed, as well as potential coexistence with humans. [ABSTRACT FROM AUTHOR]

We examine three avian remains from the Última Esperanza cave complex. This site is a Natural Monument situated along the flanks of Cerro Benítez, Magallanes Region of Chile. A tarsometatarsus (MLP 94-VIII-10-12) is assigned to Rhea pennata, and a humerus (MLP 94-VIII-10-111) to Phalacrocorax brasilianus. Both, R. pennata and P. brasilianu s, are currently distributed in the Magallanes Region, and their presence within the cave can be easily explained by the cut marks found on the tarsometatarsus, that evidence human consumption. The absence of traces on the humerus is not decisive in this regard, because the wings are not the most fleshy parts of the body and therefore, not the preferred piece by predators. It can represent the waste. A small bill (MLP 94-VIII-10-140) of a passerine bird belongs to a fresh bone and should be treated as contamination. • This contribution presents the first study of the Cueva del Milodón avian fossil record. • A humerus assigned to Phalacrocorax brasilianus and a tarsometatarsus of Rhea pennata, belong to species that occur in the area today. • The cut marks observed in Rhea pennata evidence anthropic interaction. • A bill from Cueva del Milodón belongs to a recent passerine bird and is considered contamination. [ABSTRACT FROM AUTHOR]

A Sr-isotope chronostratigraphy is presented for Miocene sediments deposited by the “Paranense” Sea along 1200 km of the southwestern Atlantic coast of Argentina and Uruguay. Numerical ages were obtained for shells of Aequipecten paranensis from the Argentinean Puerto Madryn Formation, Facies Balneario La Lobería, “Entrerriense Beds” of the Salado Basin, and Paraná Formation, and from the Camacho Formation (Uruguay). The 87 Sr/ 86 Sr ages fall into five age-groups that encompass the “Paranense” flooding in the latest Serravalian-Messinian interval. For the Puerto Madryn Formation, the ages span the latest Serravalian to the Tortonian and are stratigraphically coherent with the transgressive phase (11.9–10.4 Ma) and the regressive phase (10.2–9.82 Ma and 9.40–9.05 Ma) of that unit. Ages of 8.85–7.95 Ma for the “Entrerriense Beds” show them to be Tortonian while the Facies Balneario La Lobería, and the Paraná and Camacho formations span the age-range 7.50–6.00 Ma, comprising the Tortonian-Messinian interval. The regressive phase of the Puerto Madryn Formation, and the Facies Balneario La Lobería are respectively correlated with the basal and middle beds of the cliffs at Barranca Final, where the uppermost horizons of the Barranca Final Formation are exposed. The “Entrerriense Beds” are correlated with the “Cape Fairwheater Beds”. Dating the “Paranense” marine incursion permits a reappraisal of its paleogeography and differentiation of its deposits from those of the “Patagoniense” Sea. The flooding area was smaller than previously thought, with its northwestern-most boundary in the surroundings of the Santa Fe Province and its southernmost boundary in southern Santa Cruz Province. Moreover, the Paranaian Molluscan Bioprovince was coeval with the Valdesian Molluscan Bioprovince for 2.35 Ma and species included in the Aequipecten paranensis Zone lived for at least 5.90 Ma. [ABSTRACT FROM AUTHOR]

This paper describes an integrated field, petrographic and geochemical study of the Puesto del Museo Formation, a poorly known unit that evidences a Cenozoic transgression at the southernmost Golfo San Jorge Basin. The most striking features of the Puesto del Museo Formation is its occurrence as restricted ~20 m-thick-outcrops composed exclusively of friable cross-stratified grainstones. We analyzed the sedimentary facies and facies associations in order to reconstruct the depositional setting. The petrographic characterization allows assessing the composition as a very homogeneous lithological succession dominated by skeletal grainstones. Geochemistry of trace elements (Mn, Sr, Rb, rare earth elements plus yttrium = REY), and stable isotopes (C and O) were used to characterize the grainstones compositionally, and to constrain environmental and climate conditions that controlled its deposition. The diagenetic environmental comprehension helped to the interpretations of the syn- and post-depositional conditions related to the grainstones. Finally, the stratigraphic position of the Puesto del Museo grainstones into the context of the basin is discussed. This succession can be correlated with the Patagonian marine event (i.e., Golfo San Jorge and Austral basins) that took place during the late Oligocene–early Miocene, related to an elevated global sea level controlled by glacio-eustatic conditions. • Puesto del Museo Fm can represent the southernmost mid-Cenozoic carbonates at the GSJB. • These grainstones deposits flooded a rocky shore composed of the Jurassic volcanites. • The cementation begun at the seafloor followed by vadose conditions. • Trace elements supported by facies analysis reveal shallow open marine environment. • Bioclasts and C-isotope may suggest it as part of the Patagoniense transgression. [ABSTRACT FROM AUTHOR]