Skip to Main Content
GEOREF RECORD

Microtexture and genesis of clay minerals from a turbiditic sequence in a southern Pyrenees foreland basin (Jaca Basin, Eocene)

B. Bauluz, A. Yuste, M. J. Mayayo, A. B. Rodriguez-Navarro and J. M. Gonzalez-Lopez
Microtexture and genesis of clay minerals from a turbiditic sequence in a southern Pyrenees foreland basin (Jaca Basin, Eocene)
Clay Minerals (September 2012) 47 (3): 303-318

Abstract

A set of fine-grained samples from a turbiditic sequence in a Southern Pyrenees foreland basin (Jaca Basin, Eocene) were studied to determine the influence of tectonics (Pyrenean Orogeny) on phyllosilicate recrystallization and infer the grade and basin maturity. The samples from four different outcrops were examined by X-ray diffraction (XRD) and by scanning (SEM) and transmission electron microscopy (TEM) with special emphasis on clay-mineral characterization (e.g. illitic phases). The analysed samples have simple mineral assemblages and consist of detrital quartz, albite and calcite, scarce clay matrix (mainly illite with chlorite), and calcite and dolomite cement. The lack of other phyllosilicates such as mixed-layer illite-smectite (I-S), pyrophyllite, Na-micas, or kaolin minerals is quite remarkable. On the SEM scale, samples (with marl composition) have poorly sorted textures and high detrital contents. In many cases they show bedding and/or cleavage, and in some cases neither is observed. Most of the clay-sized illites show very similar crystallinity and b (sub 0) values (determined by XRD) and distributions of crystallite thickness (measured by TEM) in all the outcrops, which is typical of late-diagenesis illites forming under low-pressure conditions. These illites are parallel (or subparallel) to bedding or randomly orientated. They are also characterized by disordered polytypes and low K contents. In some TEM images, a second type of illite has been observed. This secondary illite occurs parallel to cleavage, with thicker crystals (25-35 layers), K contents in the interlayer, and a 2M (sub 1) polytype. The pole figure analysis shows that most of the clays have (00l) planes parallel (or subparallel) to bedding although there are abundant clays with random orientation. There is no trend in the clay orientation/disorientation from the south to the north of the basin. All the data indicate that the strain rate associated with the Pyrenean Orogeny has not been recorded in the turbidite sequence controlling the relative orientation of clays, although anchizonal clay crystallization is favoured as a minor process.


ISSN: 0009-8558
EISSN: 1471-8030
Coden: CLMIAF
Serial Title: Clay Minerals
Serial Volume: 47
Serial Issue: 3
Title: Microtexture and genesis of clay minerals from a turbiditic sequence in a southern Pyrenees foreland basin (Jaca Basin, Eocene)
Affiliation: Universidad de Zaragoza, Departamento de Ciencias de la Tierra, Zaragoza, Spain
Pages: 303-318
Published: 201209
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 28
Accession Number: 2013-010921
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., 3 plates, 2 tables, geol. sketch map
N42°34'08" - N42°34'08", W00°33'00" - W00°33'00"
Secondary Affiliation: Universidad de Granada, ESP, Spain
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201308
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal