The Phytoclast Group as a tracer of palaeoenvironmental changes in the early Toarcian

In this paper, we present a detailed review of upper Pliensbachian-lower Toarcian kerogen assemblages from the southern areas of the West Tethys shelf (between Morocco and northern Spain) and demonstrate the use of the Phytoclast Group as a tracer of palaeoenvironmental changes in the early Toarcian.The kerogen assemblages in the studied sections from the southern areas of the West Tethys shelf are dominated by the Phytoclast Group and terrestrial palynomorphs, although punctual increases in amorphous organic matter (AOM), freshwater (Botryococcus) and marine microplankton (dinoflagellate cysts, acritarchs, and prasinophyte algae) were observed at specific stratigraphic intervals. The opaque/non-opaque phytoclasts (OP/NOP) ratio was used to trace changes in palaeoclimate and other palaeoenvironmental parameters and reflect climate gradients associated with water availability during early Toarcian. During the Pliensbachian-Toarcian and Jenkyns events, changes in kerogen assemblages in the southern areas of the West Tethys shelf correlated with changes in the northern Tethys and Panthalassa shelf.The acceleration of the hydrological cycle associated with the aforementioned events was less intense in the northern Gondwana, southern and western Iberian basins, a reflection of the palaeogeographic position of these basins within the semi-arid climate belt when compared with the northern Iberian region and other northern areas of the West Tethys and Panthalassa shelf, inserted in winter-wet and warm temperate climate belts. AOM enrichment associated with the Pliensbachian-Toarcian and Jenkyns events reflects an increase in primary productivity linked with increased continental weathering, fluvial runoff and riverine OM, and nutrient input into marine areas, inducing water column stratification and promoting the preservation of OM.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5421485

NEW RADIOCARBON EVIDENCE FOR HUMAN OCCUPATION IN CENTRAL ARGENTINA DURING THE MIDDLE AND LATE HOLOCENE: THE ONGAMIRA VALLEY CASE

ABSTRACT The Ongamira Valley (Córdoba, Argentina) shows a persistent occupational history of its territory. Even one of the first Argentinian radiocarbon (14C) dates was calculated in this valley; for 70 years, the chronology was based on relative dates (stratigraphy and its cultural content). For this reason, since 2010 a 14C dating program has been developed focusing on the chronology of eight of the 60 sites identified so far for the valley. This work reports the outcomes of this program with 27 new dates. These data have been related to characteristics of the material culture, use of space and mobility of hunter-gatherer societies. The results have allowed us to bring new insights into a continuous occupation of the valley since the Middle Holocene according to the human peopling models proposed. It has also been possible to provide greater chronological precision to various activities related to feeding practices, use of space associated with rock-shelters, palaeoenvironmental changes and incorporation of new technologies into daily practices.