The distribution of Haentzschelinia ottoi (Geinitz) is studied from the Lajas Formation (Middle Jurassic) of the Neuquén Basin in Arroyo Carreri. For this work were considered more than 200 specimens and their relation with the facies and other trace fossils, as well as the ichnofabric index (ii) and the bedding plane bioturbation index (bpbi) were determined. H. ottoi appears in fluvio-dominated delta front (FA2) and fluvio-dominated delta front to delta plain with tidal influence (FA3). In general, trace fossils correspond to deposit-feeders (H. ottoi, Planolites, ?Taenidium, ?Parahaentzschelinia), suggesting the development of an impoverished Cruziana ichnofacies. In particular, H. ottoi constitutes monoichnospecific associations with ii/bpbi = 2-3 (in FA2 and FA3) or more diverse associations with other trace fossils and ii/bpbi = 3-4 (only in FA3). The development of one association or another depends on the interplay between sediment discharge and salinity conditions. More diverse associations with ii/bpbi = 3-4 would be favoured by a rise in salinity under the influence of tides and enough time for substrate colonisation by other deposit-feeders. Lower salinity conditions or high frequency of sediment discharge would have given rise to monoichnospecific associations of H. ottoi with ii/bpbi = 2-3.

The Yalguaraz gondwanic porphyry-type deposit is located at the eastern margin of the Frontal Cordillera in the Andes of Argentina. In this deposit, two alteration-mineralization stages (early and late) were recognized. The early stage is linked to the intrusion of a dacitic porphyry that produced pervasive potassic alteration (biotite - K–feldspar - quartz - andalusite) along with EB, A, and B veins. Mineralization occurs mainly disseminated in the dacitic porphyry and minor in A and B veins and consists of pyrrhotite, chalcopyrite, pyrite, and minor molybdenite. The late stage led to pervasive phyllic alteration (sericite + quartz + pyrite ± chlorite ± rutile ± chalcopyrite) along d-type veinlets and subsequent tourmalinization. The presence of hypogenic pyrrhotite and the scarce magnetite could indicate that it would be genetically associated with reducing magmas although the lack of ilmenite series oxides in the precursor magmatic rocks suggest that the reducing character of the mineralizing magmas was acquired during the magma evolution. δ18O and the Pb isotopic composition of the mineralizing magma confirm continental crust assimilation processes in its genesis whereas whole rock geochemistry suggests the involvement of marine sediment which would support the change in the redox conditions of the magma precursor of the porphyry-type mineralization.

In this work, specimens of the genus Didemnoides Bonet and Benveniste-Velásquez are described from different sections of the Tithonian-Berriasian interval of the Neuquén Basin (Vaca Muerta Formation). Didemnoides has been interpreted as spicules of ascidians related to the family Didemnidae Giard, so this record represents the first documentation of tunicates for the Tithonian – Berriasian of the Neuquén Basin. The presence of spicules of didemnid ascidians allow to infer the development of hard substrates, high availability of nutrients, low water turbidity and low fresh water influx. The location of the Didemnoides-bearing levels within the sequence stratigraphic framework of the Vaca Muerta Formation evidences its development during transgressive system tracts, where these conditions prevail.

Se analizaron aspectos paleoambientales y paleoecológicos de la Formación Río Loro (Paleógeno, noroeste argentino). Se reconocieron cuatro facies sedimentarias. La Facies 1 (areniscas gruesas a guijarrosas amalgamadas) registran sedimentación en canales entrelazados. La Facies 2 (fangolitas masivas o débilmente laminadas) y la Facies 3 (fangolitas intercaladas con areniscas) reflejan depositación en planicies de inundación distales a proximales, respectivamente. La Facies 4 (areniscas gruesas a medias) documenta depositación en canales meandriformes. Trazas fósiles de insectos atribuibles a estructuras de nidificación fueron reconocidas en las facies 1 y 4. Las facies fueron agrupadas en una asociación de facies principal que refleja sedimentación en un sistema fluvial multicanalizado complejo con áreas de planicie de inundación fangosa relativamente estables, donde condiciones estacionales húmedas a más secas favorecieron la colonización del sustrato por parte de la biota y procesos de formación de suelo. Se reconocieron restos de mamíferos y reptiles bien conservados en depósitos de la Facies 3, con estadios bajos de meteorización (principalmente etapas 1 y 2) y ausencia de signos de abrasión. Asimismo, la presencia de restos articulados y su integración con el marco paleoambiental, sugieren desarticulación parcial y enterramiento temprano, posiblemente a partir de desbordes durante inundaciones. Los hábitos inferidos para los taxones registrados muestran consistencia con la proximidad a fuentes de agua dulce y áreas vegetadas, así como estacionalidad. Este enfoque multidisciplinario contribuye a la comprensión de los atributos paleoambientales y paleontológicos de la Formación Río Loro y representa una base para futuros estudios sobre esta unidad y su notable registro fósil.

The Pikimachay cave in south-eastern Peru had an important role in archaeological discussions concerning the first peopling of South America, and the Southern Andes in particular. The excavations by Richard MacNeish in 1969-1970 identified a sequence of possible but controversial Late Pleistocene human occupations up to historical times. As a part of a research programme aiming to re-assess the Late Pleistocene remains from this site, we made taphonomic observations on a sample of bones (n=40) from the lower strata (layers h to k) as follows: h (n=17), h1 (n=6), i (n=4), i1 (n=7), j (n=5), and k (n=1). The conventional uncalibrated radiocarbon dates initially obtained suggest that these layers span a period of ~14.0 to 25.0 thousand years before present (kybp). Each bone was thoroughly examined to determine the nature of modifications to them, and to describe alterations and the general condition of the specimens in order to identify possible anthropic intervention. For this purpose, we examined the surface modifications indicating fresh or post-depositional fractures, the different kinds of marks, weathering, and the presence of manganese staining. We concluded that several bones (n=8) from layer h showed various human-made modifications. We can therefore suggest that this new information justifies the assumption that the bones and lithic materials from layer h would have been produced during the Early Holocene/Late Pleistocene between ~≥9.0/10.0 and ~14.1, probably at ~14.1 kybp; an assumption that can also be considered for the stone remains from the underlying strata h1 that yielded a similar date. The bone remains from strata j to k do not show any human modifications. Furthermore, if the reported chronology and its association with the anthropic remains are true, the Pikimachay cave could still be relevant to the debate over the human colonisation of western South America that occurred within a similar timeframe during the postglacial era.