Browsing by Author "Raigemborn, MS"

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    Insights on the controls on floodplain-dominated fluvial successions: A perspective from the early–middle miocene santa cruz formation in río chalía (patagonia, argentina)
    (Journal of the Geological Society, 2021-01-01) Cuitiño, JI; Raigemborn, MS; Bargo, MS; Vizcaíno, SF; Muñoz, NA; Kohn, MJ; Kay, RF
    The Santa Cruz Formation (SCF) in Río Chalía (Austral Basin, Patagonia, Argentina) is a well-exposed fluvial succession with abundant and diverse fossil vertebrates accumulated during the Miocene Climatic Optimum (MCO). Using facies analysis, characterization of stratigraphic architecture, U–Pb geochronology and vertebrate palaeontology, we assess the timing and interplay of controlling factors on the sedimentation, including tectonics, global sea level, climate and sediment supply. Throughout the succession, there occurred a constant aggradation of the floodplain-dominated fluvial system. Seven zircon U–Pb ages constrain the time of accumulation between c. 18 and 15.2 Ma, under a relatively constant sedimentation rate of 150 ± 50 m myr–1 . The large number of fossil vertebrates indicates a Santacrucian fauna, showing no recognizable changes through the section. The basin-scale, low-gradient anastomosed fluvial system of the SCF records a period of about 3 myr of relatively constant environmental conditions controlled by continuous basin subsidence and high sediment supply conditioned by explosive volcanism together with weathering of uplifting terrains in the Andes. In addition, the system was influenced by a temperate to warm and subhumid climate favoured by the MCO before the onset of the Andean rain shadow, together to high global sea levels.
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    Paleoenvironmental reconstruction of the coastal Monte Léon and Santa Cruz formations (Early Miocene) at Rincón del Buque, Southern Patagonia: A revisited locality
    (Journal of South American Earth Sciences, 2015-07-01) Raigemborn, MS; Matheos, SD; Krapovickas, V; Vizcaíno, SF; Bargo, MS; Kay, RF; Fernicola, JC; Zapata, L
    © 2015 Elsevier Ltd.Sedimentological, ichnological and paleontological analyses of the Early Miocene uppermost Monte León Formation and the lower part of the Santa Cruz Formation were carried out in Rincón del Buque (RDB), a fossiliferous locality north of Río Coyle in Santa Cruz Province, Patagonia, Argentina. This locality is of special importance because it contains the basal contact between the Monte Léon (MLF) and the Santa Cruz (SCF) formations and because it preserves a rich fossil assemblage of marine invertebrates and marine trace fossils, and terrestrial vertebrates and plants, which has not been extensively studied. A ~90m-thick section of the MLF and the SCF that crops out at RDB was selected for this study. Eleven facies associations (FA) are described, which are, from base to top: subtidal-intertidal deposits with Crassotrea orbignyi and bioturbation of the Skolithos-Cruziana ichnofacies (FA1); tidal creek deposits with terrestrial fossil mammals and Ophiomorpha isp. burrows (FA2); tidal flat deposits with Glossifungites ichnofacies (FA3); deposits of tidal channels (FA4) and tidal sand flats (FA5) both with and impoverish Skolithos ichnofacies associated; marsh deposits (FA6); tidal point bar deposits recording a depauperate mixture of both the Skolithos and Cruziana ichnofacies (FA7); fluvial channel deposits (FA8); fluvial point bar deposits (FA9); floodplain deposits (FA10); and pyroclastic and volcaniclastic deposits of the floodplain where terrestrial fossil mammal remains occur (FA11).The transition of the MLF-SCF at RDB reflects a changing depositional environment from the outer part of an estuary (FA1) through the central (FA2-6) to inner part of a tide-dominated estuary (FA7). Finally a fluvial system occurs with single channels of relatively low energy and low sinuosity enclosed by a broad, low-energy floodplain dominated by partially edaphized ash-fall, sheet-flood, and overbank deposits (FA8-11). Pyroclastic and volcaniclastic materials throughout the succession must have been deposited as ash-fall distal facies in a fluvial setting and also were carried by fluvial streams and redeposited in both estuarine and fluvial settings. These materials preserve most of the analyzed terrestrial fossil mammals that characterize the Santacrucian age of the RDB's succession. Episodic sedimentation under volcanic influence, high sedimentation rates and a relatively warm and seasonal climate are inferred for the MLF and SCF section.Lateral continuity of the marker horizons at RDB serve for correlation with other coastal localities such as the lower part of the coastal SCF south of Río Coyle (~17.6-17.4Ma) belonging to the Estancia La Costa Member of the SCF.
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    The record of the typothere Pachyrukhos (Mammalia, Notoungulata) and the Chinchillid Prolagostomus (Mammalia, Rodentia) in the Santa Cruz Formation (early-middle Miocene) south to the Río Coyle, Patagonia, Argentina
    (Publicacion Electronica de la Asociacion Paleontologica Argentina, 2021-01-01) Vizcaíno, SF; Bargo, MS; Kay, RF; Raigemborn, MS
    The continental early-middle Miocene Santa Cruz Formation (SCF) from Patagonia is one of the most important stratigraphic units of southern South America in terms of the terrestrial Neogene record. Its fossil content was pivotal for establishing the succession of Cenozoic faunas from Patagonia and formed the basis of the Santacrucian South American Land Mammal Age. Despite the updated knowledge recently achieved, the stratigraphic distribution of many taxa within the SCF remains to be clarified. That is the case with the typothere notoungulate Pachyrukhos and the chinchillid rodent Prolagostomus. New information on the stratigraphy of the SCF along the north bank of the Río Gallegos and Cabo Buen Tiempo (Santa Cruz Province), together with a detailed analysis of the provenance information of the specimens in the principal old museum collections, sheds light on the record of these taxa south to Río Coyle. Our results show that the first recorded occurrence of both taxa in the area was between ~17 Ma and 17.41 Ma, restricted to the upper part of the SCF, including the upper part of the Estancia La Costa Member at Cañadón Las Totoras-Monte Tigre, and the superimposed Estancia La Angelina Member along the Río Gallegos and Cabo Buen Tiempo. Their presence suggests a trend to aridification in the upper part of the SCF south to the Río Coyle. These results are consistent with recent information obtained from other locations of the SCF north to the Río Coyle.