Publication Date:
2019-03-27
Description:
Ground wedge structures of cryogenic origin are common in the Quaternary sediments along the coast
of the Patagonia, and their formation is related to climatic cold events experienced by this area in the Late Quaternary.
The infilling sediments of two wedges generations were analyzed in the area of Puerto Deseado. Bulk chemistry (major
elements), X-ray diffraction (XRD), morphoscopic observations with Scanning Electronic Microscope (SEM) and chemical analyses of volcanic glass shards were undertaken to provide indications about infilling sediment provenience,
along with chronological constraint for wedge formation. Bulk chemistry and XRD patterns indicate a significant SiO2-
enriched composition of the sediment infilling compared to the most of the loess deposits of the North Argentina and
the present day dust originated in Patagonia. This was interpreted as due to the nature of the bedrock present over the
Deseado Massif. SEM morphoscopic characteristics of glass shards evidence typical aeolian reworking features, with
impact structures and indented edges of the volcanic fragments. Chemical analyses of the glass shards indicate that
they were probably generated by the H0 eruption (17,300-17,400 cal yr BP) of the Hudson volcano. Volcanological data indicate that H0 eruption dispersed toward NE, but volcanic glasses were available for reworking due to a WNW component in the western wind direction. Over the Deseado Massif structural high the glass shards mixed with sediments
enriched in SiO2, and were eventually deflated further to SE reaching the present coastal area and infilling the frost
cracks. The age of the glass shards (17,300-17,400 cal yr BP) and that of the sandy layer affected by cryogenic structures (14,670±750 yr BP) well constrain to the Late Glacial both wedge generations.
Description:
Progetto Ateneo 2007, University of Pisa; PRIN2008, MIUR
Description:
Published
Description:
130-144
Description:
5A. Ricerche polari e paleoclima
Description:
JCR Journal
Keywords:
Wedge structure
;
geochemistry
;
Quaternary sediments
;
Patagonia
;
Paleoclima
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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