La cuenca Neoproterozoica-Eocámbrica en el NOA: Sedimentología y ambientes de depósito de secuencias con icnofósiles, nuevas perspectivas.

LÓPEZ DE AZAREVICH, V., ACEÑOLAZA, F., ACEÑOLAZA, G.F., OMARINI, R. Y AZAREVICH, M.,

Relatorio de la XIII Reunión Argentina de Sedimentología

Asociación Asgentina de Sedimentología

Lugar: Salta; Año: 2012; p. 119 - 132

In NW Argentina, the Neoproterozoic-Eocambrian sequences that include an important ichnofossil record are filites, shales, quartzites and grauvackesof the Puncoviscana Formations.l., deposited in a shallow marine basin withtidal flats and foreshore to distal platforms (less than 200 meters-deep). Primary sedimentary structures such as linguoid, interference and double crested ripples, hummocky cross stratification, flasser and ondulitic stratification, rill marks, exposed surfaces, tidal rhythmites, as well as photic zone related microbial mats and algae activity, confirm an inter- to sub-tidal deposition influenced by tides, waves and storms. At the moment, no turbidite sequences were found in the studied localities of Rancagua, Palermo Oeste, Km 13, Bárcena, Purmamarca, Tilcara, Quebrada del Toro, Muñano, Tastil, San Antonio de los Cobres. They contain Nereites and Oldhamia ichnoassociations that suggest an Upper Ediacara to Early Cambrian (Terraneuvian - Series 2?) age of deposition. Earliest depositional age is also confirmed by U/Pb zircon age obtained from magmatic rocks that intrude or interlayered the sedimentary sequence (563 to 517 Ma).Analyses of astronomic periods obtained from tidal rhythmites allowed to adjust, from another point of view, the relation between astronomic, sedimentary and biologic processes occurred at global scale in the temporal range of deposition (Neoproterozoic-Eocambrian). It implies that an important decrement in the Moon retreat during the Neoproterozoic-Cambrian transition influenced in more stable and lowertides and benign conditions for the Cambrian Explotion. Geotectonic interpretations of the Puncoviscana basin developed at the present are based on petrologic, geochemical and geochronological data, but lack of the appropriate sedimentological context that allow an adjust evaluation the geodynamic configuration from the initial rifting occurred during Rodinia fragmentation.s.l., deposited in a shallow marine basin withtidal flats and foreshore to distal platforms (less than 200 meters-deep). Primary sedimentary structures such as linguoid, interference and double crested ripples, hummocky cross stratification, flasser and ondulitic stratification, rill marks, exposed surfaces, tidal rhythmites, as well as photic zone related microbial mats and algae activity, confirm an inter- to sub-tidal deposition influenced by tides, waves and storms. At the moment, no turbidite sequences were found in the studied localities of Rancagua, Palermo Oeste, Km 13, Bárcena, Purmamarca, Tilcara, Quebrada del Toro, Muñano, Tastil, San Antonio de los Cobres. They contain Nereites and Oldhamia ichnoassociations that suggest an Upper Ediacara to Early Cambrian (Terraneuvian - Series 2?) age of deposition. Earliest depositional age is also confirmed by U/Pb zircon age obtained from magmatic rocks that intrude or interlayered the sedimentary sequence (563 to 517 Ma).Analyses of astronomic periods obtained from tidal rhythmites allowed to adjust, from another point of view, the relation between astronomic, sedimentary and biologic processes occurred at global scale in the temporal range of deposition (Neoproterozoic-Eocambrian). It implies that an important decrement in the Moon retreat during the Neoproterozoic-Cambrian transition influenced in more stable and lowertides and benign conditions for the Cambrian Explotion. Geotectonic interpretations of the Puncoviscana basin developed at the present are based on petrologic, geochemical and geochronological data, but lack of the appropriate sedimentological context that allow an adjust evaluation the geodynamic configuration from the initial rifting occurred during Rodinia fragmentation.Nereites and Oldhamia ichnoassociations that suggest an Upper Ediacara to Early Cambrian (Terraneuvian - Series 2?) age of deposition. Earliest depositional age is also confirmed by U/Pb zircon age obtained from magmatic rocks that intrude or interlayered the sedimentary sequence (563 to 517 Ma).Analyses of astronomic periods obtained from tidal rhythmites allowed to adjust, from another point of view, the relation between astronomic, sedimentary and biologic processes occurred at global scale in the temporal range of deposition (Neoproterozoic-Eocambrian). It implies that an important decrement in the Moon retreat during the Neoproterozoic-Cambrian transition influenced in more stable and lowertides and benign conditions for the Cambrian Explotion. Geotectonic interpretations of the Puncoviscana basin developed at the present are based on petrologic, geochemical and geochronological data, but lack of the appropriate sedimentological context that allow an adjust evaluation the geodynamic configuration from the initial rifting occurred during Rodinia fragmentation.