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Influence of granitoid textural parameters on sediment composition: Implications for sediment generation

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Caracciolo, Luca and Tolosana Delgado, Raimon and Le Pera, Emilia and Eynatten, Hilmar von and Arribas Mocoroa, José and Tarquini, Simone (2012) Influence of granitoid textural parameters on sediment composition: Implications for sediment generation. Sedimentary Geology, 280 . pp. 93-197. ISSN 0037-0738

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Abstract

The aim of this study is to determine and characterise the control exerted by parent rock texture on sand
composition as a function of grain size. The sands investigated were generated from granitoid parent rocks
by the Rhone, Damma and Sidelen glaciers, which drain the Aar Massif in the Central Alps (Switzerland),
and were deposited in glacial and fluvio-glacial settings. Mechanical erosion, comminution (crystal breakdown
and abrasion) and hydraulic sorting are the most important processes controlling the generation of
sediments in this environment, whereas chemical and/or biochemical weathering plays a negligible role.
By using a GIS-based Microscopic Information System (MIS), five samples from the glacier-drained portions
of the Aar basement have been analysed to determine textural parameters such as modal composition, crystal
size distribution and mineral interfaces (types and lengths). Petrographic data of analysed sands include
traditional point counts (Gazzi-Dickinson method, minimum of 300 points) as well as textural counts to
determine interface types, frequency, and polycrystallinity in phaneritic rock fragments. According to
Pettijohn's classification, grain‐size dependent compositions vary from feldspathic litharenite (0φ fraction)
via lithic arkose (1φ and 2φ) to arkose (3φ and 4φ). Compositional differences among our data set were compared
to modern plutoniclastic sands from the Iberian Massif (Spain) and the St. Gabriel Mts. (California,
USA), which allowed us to assess the role exerted by glaciers in generating sediments. By combining data
from the MIS with those from petrographic analysis, we outlined the evolution of mineral interfaces from
the parent rocks to the sediments.


Item Type:Article
Uncontrolled Keywords:Textural parameters, Grain size, Mineral interfaces, Composition, Glacial environment, Sediment generation
Subjects:Sciences > Geology > Petrology
ID Code:17998
Deposited On:25 Jan 2013 12:21
Last Modified:07 Feb 2014 09:57

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