Influence of subaqueous processes on the construction and accumulation of an aeolian sand sheet

Autor(es)

Basilici, Giorgio ^[1] ; Fuehr Dal' Bo, Patrick Francisco ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Dept Geol & Nat Resources, Inst Geosci, BR-13083870 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: EARTH SURFACE PROCESSES AND LANDFORMS; v. 39, n. 8, p. 1014-1029, JUN 30 2014.
• Citações Web of Science: 3

Resumo

In aeolian sand sheets the interaction between aeolian and subaqueous processes is considered one of the principal factors that controls this depositional environment. To examine the role played by the subaqueous processes on the construction and accumulation of sand sheets, surface deposits and subsurface sedimentary sections of a currently active aeolian sand sheet, located in the Upper Tulum Valley (Argentina), have been examined. On the sand sheet surface, airflows enable the construction of nabkhas, wind-rippled mantles (flattened accumulations of sand forming wind ripples), megaripples, and small transverse dunes. Subaqueous deposits consist of sandy current ripples covered by muddy laminae. The latter are generated by annual widespread but low-energy floods that emanate from the nearby mountains in the aftermath of episodes of heavy precipitations. Deposits of subaqueous origin constitute 5% of the accumulated sand sheet thickness.The construction of the sand sheet is controlled by meteorological seasonal changes: the source area, the San Juan river alluvial fan, receives sediment by thaw-waters in spring-summer; in fall-winter, when the water table lowers in the alluvial fan, the sediment is available for aeolian transport and construction of the sand sheet area. The flood events play an important role in enabling sand sheet accumulation: the muddy laminae serve to protect the underlying deposits from aeolian winnowing. Incipient cement of gypsum on the sand and vegetation cover acts as an additional stabilizing agent that promotes accumulation. Episodic and alternating events of erosion and sedimentation are considered the main reason for the absence of soils and palaeosols. Results from this study have enabled the development of a generic model with which to account for: (i) the influence of contemporaneous subaqueous processes on the construction and accumulation in recent and ancient sand sheets; and (ii) the absence of developed soils in this unstable topographic surface. Copyright (c) 2013 John Wiley \& Sons, Ltd. (AU)

• Processo FAPESP: 07/00140-6 - Relações entre depósitos e paleossolos de ambiente semi-árido: um exemplo antigo (Bacia de Bauru, estados de GO, MG e MS) e um análogo atual (Vale do rio Bermejo, W de Argentina)
• Beneficiário: Giorgio Basilici
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 07/02079-2 - Paleossolos de ambiente semi-árido: um análogo antigo (Formação Marília, Bacia Bauru, estados de GO, MS e SP)
• Beneficiário: Patrick Francisco Führ Dal' Bó
• Modalidade de apoio: Bolsas no Brasil - Mestrado