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Nesse estudo foram realizadas análises de isótopos de carbono e nitrogênio de esmalte dentário e dentina de indivíduos sepultados em camadas sem e com cerâmica do sítio Forte Marechal Luz, localizado no litoral de Santa Catarina. Os resultados do colágeno da dentina sugerem que os indivíduos teriam uma dieta proteica rica em recursos marinhos durante o período de formação dos dentes analisados. No entanto, comparando períodos anteriores com posteriores à presença da cerâmica, observa-se uma leve tendência para resultados mais negativos no carbono nas camadas com cerâmica, indicando um maior consumo de recursos como plantas C3 e animais terrestres durante os períodos posteriores de ocupação do sítio e, consequentemente uma evidência de maior diversificação alimentar.

The age and stratigraphic subdivisions for the late Oligocene-Miocene, marine deposits of Patagonia (Patagoniense succession) have been largely debated. Most studies for the Comodoro Rivadavia region were focused on its biostratigraphy and stratigraphic relations with the underlying and overlying mammal-bearing terrestrial strata. We report here thirteen new 86Sr/87Sr ages obtained from wellpreserved oyster valves of the Chenque Formation in the classical Patagoniense outcrops around the city of Comodoro Rivadavia (Golfo San Jorge Basin, Argentina). According to these ages, the deposition of the unit in the region occurred between 19.69 and 15.37 Ma (Burdigalian-early Langhian). A lower interval of normal sedimentation rate (Sequences 1 and 2) and an upper interval of high sedimentation rate (Sequence 3) are defined according to these new ages of the Chenque Formation. Subsequently, the depositional age of the Chenque Formation is compared with other well-dated marine successions of southern Patagonia located within the Austral Basin. This analysis suggests that the Austral and Golfo San Jorge basins were flooded by the Atlantic sea at about the same time (~21-20 Ma), inundating what was before a vast continental region of southern Patagonia. A renewed phase of continentalization occurred at about 18 Ma in the Austral Basin and at about 15 Ma in the study region of the Golfo San Jorge Basin. This 3 my difference combined with the elevated sedimentation rate estimated for the upper part of the study interval, suggest that the Golfo San Jorge Basin may have locally experienced relatively high subsidence rates during the early Miocene, allowing prolonged marine sedimentation in the Comodoro Rivadavia area. Consequently, the accumulation of the terrestrial deposits assigned to the Santa Cruz Formation started at about 15 Ma in the study region, later than in other localities of southern Patagonia. This results clearly indicate a remarkable interdigitation between the Santa Cruz and Chenque formations in a west-east transect across central Patagonia.

The age and stratigraphic subdivisions for the late Oligocene-Miocene, marine deposits of Patagonia (Patagoniense succession) have been largely debated. Most studies for the Comodoro Rivadavia region were focused on its biostratigraphy and stratigraphic relations with the underlying and overlying mammal-bearing terrestrial strata. We report here thirteen new 86Sr/87Sr ages obtained from wellpreserved oyster valves of the Chenque Formation in the classical Patagoniense outcrops around the city of Comodoro Rivadavia (Golfo San Jorge Basin, Argentina). According to these ages, the deposition of the unit in the region occurred between 19.69 and 15.37 Ma (Burdigalian-early Langhian). A lower interval of normal sedimentation rate (Sequences 1 and 2) and an upper interval of high sedimentation rate (Sequence 3) are defined according to these new ages of the Chenque Formation. Subsequently, the depositional age of the Chenque Formation is compared with other well-dated marine successions of southern Patagonia located within the Austral Basin. This analysis suggests that the Austral and Golfo San Jorge basins were flooded by the Atlantic sea at about the same time (~21-20 Ma), inundating what was before a vast continental region of southern Patagonia. A renewed phase of continentalization occurred at about 18 Ma in the Austral Basin and at about 15 Ma in the study region of the Golfo San Jorge Basin. This 3 my difference combined with the elevated sedimentation rate estimated for the upper part of the study interval, suggest that the Golfo San Jorge Basin may have locally experienced relatively high subsidence rates during the early Miocene, allowing prolonged marine sedimentation in the Comodoro Rivadavia area. Consequently, the accumulation of the terrestrial deposits assigned to the Santa Cruz Formation started at about 15 Ma in the study region, later than in other localities of southern Patagonia. This results clearly indicate a remarkable interdigitation between the Santa Cruz and Chenque formations in a west-east transect across central Patagonia.

ABSTRACT: The present work investigates the relationship between whole-rock geochemistry and stable isotope composition from carbonatites belonging to the Tapira, Araxá, Salitre, Serra Negra, Catalão I, and Catalão II alkaline-carbonatite complexes of the Alto Paranaiba Igneous Province (APIP), central Brazil and from the Jacupiranga Complex, of the Ponta Grossa Province, southeast Brazil. The APIP complexes are ultrapotassic, comprising bebedourites, phoscorites, nelsonites, and carbonatites, whereas Jacupiranga is a sodic complex composed of ijolite-series rocks, syenites, carbonatites, and alkaline gabbros. The geochemistry data allied to mineralogical constraints allowed us to classify the carbonatites into five groups, and to devise a chemical index (BaO/(BaO+SrO)) to gauge the magmatic evolution of the studied carbonatites.The APIP carbonatites evolve from apatite-rich calciocarbonatites toward Ba-, Sr-, and rare earth element (REE)-rich magnesiocarbonatites. This evolution is mostly driven by apatite, phlogopite, dolomite, and calcite fractionation and consequent enrichment in monazite, norsethite, and strontianite. Stable isotope data show a wide diversity of petrogenetic processes in play at the APIP, relatively to the Jacupiranga Complex, which is interpreted as a result of the shallower intrusion levels of the APIP complexes. Such shallower emplacement, at low lithostatic pressure, allowed for a complex interplay of fractional crystallization, liquid immiscibility, degassing, and interaction with hydrothermal and carbohydrothermal systems.

The age and stratigraphic subdivisions for the late Oligocene-Miocene, marine deposits of Patagonia (Patagoniense succession) have been largely debated. Most studies for the Comodoro Rivadavia region were focused on its biostratigraphy and stratigraphic relations with the underlying and overlying mammal-bearing terrestrial strata. We report here thirteen new 86Sr/87Sr ages obtained from wellpreserved oyster valves of the Chenque Formation in the classical Patagoniense outcrops around the city of Comodoro Rivadavia (Golfo San Jorge Basin, Argentina). According to these ages, the deposition of the unit in the region occurred between 19.69 and 15.37 Ma (Burdigalian-early Langhian). A lower interval of normal sedimentation rate (Sequences 1 and 2) and an upper interval of high sedimentation rate (Sequence 3) are defined according to these new ages of the Chenque Formation. Subsequently, the depositional age of the Chenque Formation is compared with other well-dated marine successions of southern Patagonia located within the Austral Basin. This analysis suggests that the Austral and Golfo San Jorge basins were flooded by the Atlantic sea at about the same time (~21-20 Ma), inundating what was before a vast continental region of southern Patagonia. A renewed phase of continentalization occurred at about 18 Ma in the Austral Basin and at about 15 Ma in the study region of the Golfo San Jorge Basin. This 3 my difference combined with the elevated sedimentation rate estimated for the upper part of the study interval, suggest that the Golfo San Jorge Basin may have locally experienced relatively high subsidence rates during the early Miocene, allowing prolonged marine sedimentation in the Comodoro Rivadavia area. Consequently, the accumulation of the terrestrial deposits assigned to the Santa Cruz Formation started at about 15 Ma in the study region, later than in other localities of southern Patagonia. This results clearly indicate a remarkable interdigitation between the Santa Cruz and Chenque formations in a west-east transect across central Patagonia.