Intermontane eolian sand sheet development, Upper Tulum Valley, central-western Argentina

Patrick Francisco Fuhr Dal' Bó,Giorgio Basilici

doi:10.1590/2317-4889201530140

Patrick Francisco Fuhr Dal' Bó, Giorgio Basilici

Open Access

https://doi.org/10.1590/2317-4889201530140

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Abstract

ABSTRACTThe intermontane Upper Tulum eolian sand sheet covers an area of ca. 125 km² at north of the San Juan Province, central-western Argentina. The sand sheet is currently an aggrading system where vegetation cover, surface cementation and periodic flooding withhold the development of dunes with slipfaces. The sand sheet surface is divided into three parts according to the distribution of sedimentary features, which reflects the variation in sediment budget, water table level and periodic flooding. The central sand sheet part is the main area of eolian deposition and is largely stabilized by vegetation. The sedimentary succession is 4 m thick and records the vertical interbedding of eolian and subaqueous deposits, which have been deposited for at least 3.6 ky with sedimentation rates of 86.1 cm/ky. The construction of the sand sheet is associated with deflation of the sand-graded debris sourced by San Juan alluvial fan, which is available mainly in drier fall-winter months where water table is lower and wind speeds are periodically above the threshold velocity for sand transport. The accumulation of sedimentary bodies occurs in a stabilized eolian system where vegetation cover, thin mud veneers and surface cementation are the main agents in promoting accumulation. The preservation of the sand sheet accumulations is enabled by the progressive creation of the accommodation space in a tectonically active basin and the continuous burial of geological bodies favored by high rates of sedimentation.

Highlights

Eolian sand sheets are extensive, flat to gently undulating sandy surfaces, covered predominantly with wind ripples and marked by the absence of dunes with slip faces (Fryberger et al 1979; Kocurek & Nielson 1986)
Stabilized and active dune fields are common across the Argentinian Pampas to the Andean Piedmont (Zárate & Tripaldi 2012) and sand sheet deposits appear to form a continuously succession that span most of the Holocene in the San Luis paleodune field (Forman et al 2014)
The Upper Tulum eolian sand sheet is an example of an intermontane eolian system where vegetation cover, surface cementation, and periodic flooding are the main controlling factors for sand sheet development

Summary

Introduction

Eolian sand sheets are extensive, flat to gently undulating sandy surfaces, covered predominantly with wind ripples and marked by the absence of dunes with slip faces (Fryberger et al 1979; Kocurek & Nielson 1986). Modern eolian sand sheets form significant part of desertic systems worldwide and, the well-known examples are in trailing and advancing margins of ergs (Fryberger et al 1979), there is a number of examples from coastal, alluvial fan, ephemeral river, and periglacial settings (Hummel & Kocurek 1984; Kocurek & Nielson 1986; Langford 1989; Mountney & Russell 2004) Observations from these modern areas suggest that a number of factors operate single or in conjunction to withhold dune development, including a high water table, surface cementation or binding, periodic or seasonal flooding, significant available population of coarsegrained sediment, and vegetation (Kocurek & Nielson 1986).

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