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The gravel mantels known as 'Rodados Patagónicos' of Eastern Patagonia are one of the most distinctive features of the regional landscape. Their significant roundness, along with additional sedimentary and geomorphological evidence, indicates their origin is linked to fluvial action. Currently, no natural processes exist on Earth potentially generating equivalent deposits, either in Patagonia or elsewhere around the world. The hydrological conditions responsible for the gravel formation were thus likely very different from those currently prevailing in Argentine Patagonia, suggesting the gravel mantels formed during the Late Cenozoic, when surface drainage networks of relatively high energy existed in the region. Such high energy was induced by powerful flow rates and/or strong water gradients, attributable to tectonism, epirogenesis and/or lowering of sea level. Periods with water flow regimes significantly higher than at present characterized the full glacial phases lasting several thousands of years, corresponding to each of the many glaciations of the Pliocene and Pleistocene. The capacity for erosion and water transport would have been increased by the sea level drop characteristic of each full glacial phase. There were also much shorter periods, known as 'terminations', representing the abrupt ending of the main glacial events during which large amounts of water were released as a result of the intensive melting of the Cordilleran ice sheet. During interglacial periods, in the absence of large masses of ice in the mountains and with average temperatures similar to or higher than at present, layers of gravel were deposited as a result of tectonic or epirogenic movement or by reactivation of drainage networks produced by sea level lowering (glacio-eustatism). These endogenous landscape reactivations were also independent of and longer than the climatic fluctuations and therefore overlapped with both interglacial and glacial periods. Finally, some units of the 'Rodados Patagónicos' may also have been deposited during major pluvial events, characterized by higher mean annual precipitation over sufficiently long periods. The current evidence suggests that, at various times since the Late Miocene, varied climatic conditions have allowed the production and accumulation of large gravel beds covering much of extra-Andean Patagonia.Los mantos de gravas de Patagonia oriental, conocidos como 'Rodados Patagónicos', constituyen por su extensión y homogeneidad uno de los elementos del paisaje más distintivos de la Patagonia oriental. El marcado redondeamiento de estos sedimentos, junto con otras evidencias sedimentológicas y geomorfológicas, indica que su origen se vincula inexorablemente con el escurrimiento superficial (acción fluvial). Puesto que en la actualidad no existen procesos que estén generando depósitos o geoformas equivalentes (en Patagonia o en otro sitio de la superficie terrestre), debe asumirse que las condiciones hídricas que permitieron su formación fueron muy distintas a las que imperan actualmente en ...

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The pollen content of 58 honey samples of Apis mellifera L. from the Andean region of Chubut (Argentinian Patagonia) was analyzed. The samples were provided by beekeepers between 1999 and 2004. Eighty-eight pollen types were identified, 30 of them are not reported in Argentinian honeys. Identified types belong to 47 families, of which the most diverse were Asteraceae (15 pollen types), Fabaceae (13 pollen types), and Rosaceae (four pollen types). From the samples analyzed, 47% were monofloral and corresponded to the following taxa: Trifolium spp. (16%), Rosaceae (10%), Aristotelia chilensis (Molina) Stuntz (7%), Discaria-Colletia (5%), Escallonia spp. (3%), Schinus patagonica (Phil.) I. M. Johnst. (2%), Phacelia secunda J. F. Gmel. (2%), Myrtaceae (2%). The results of this study show a high level of utilization of native flora by Apis mellifera. Four new types of monofloral honey were recognized: Aristotelia chilensis, Discaria-Colletia, Phacelia secunda, and Schinus patagonica. The high representation of native flora distinguishes these honeys geographically.