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GEOREF RECORD

Palaeomagnetism of Permo-Triassic rocks in the Iberian Cordillera, Spain; acquisition of secondary and characteristic remanence

P. Turner, A. Turner, A. Ramos and A. Sopena
Palaeomagnetism of Permo-Triassic rocks in the Iberian Cordillera, Spain; acquisition of secondary and characteristic remanence
Journal of the Geological Society of London (January 1989) 146 (1): 61-76

Abstract

Magnetostratigraphy is widely used as a tool for stratigraphical correlation but there are problems in its application to rocks which have suffered complex diagenesis, particularly sandy, continental red beds. In such cases the complete magnetic record should be studied in relation to its depositional, diagenetic and structural history. To this end a detailed palaeomagnetic study has been made of Permian and Triassic rocks in the northern Iberian Cordillera, Spain. Four stratigraphical units comprising the Autunian, 'Saxonian', Buntsandstein and Muschelkalk have been studied in a single section near Molina de Aragon which is well-documented sedimentologically. Autunian rocks have a characteristic remanence which is exclusively reversed and corresponds to the Kiaman Interval of Lower Permian age. A pole position (49 N, 167 W) is consistent with previous studies which indicate the rotation of Iberia in post-Triassic times relative to the stable European plate. The Saxonian facies show complex, multicomponent magnetizations; no polarity zonation can be resolved but individual components were acquired prior to the rotation of Iberia. The Buntsandstein is remarkable in that much of it is completely remagnetized in a direction similar to the present local geomagnetic direction. This secondary remanence is carried by fine grained hematite which has been formed as a result of carbonate dissolution and other diagenetic reactions. Initially, these iron oxides were probably superparamagnetic and remanence was only blocked-in by structural inversion of the Iberian Cordillera in Tertiary times and after rotation of the Iberian plate. Some of the primary remanence is preserved in some fine grained lithologies of the Buntsandstein, indicating that normal and reversed zones of magnetization were originally present. The magnetization of the Muschelkalk carbonates is also complex; secondary components similar to those of the Buntsandstein are present but there is evidence that primary components were mainly normal during Karnian times.


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 146
Serial Issue: 1
Title: Palaeomagnetism of Permo-Triassic rocks in the Iberian Cordillera, Spain; acquisition of secondary and characteristic remanence
Affiliation: Aston Univ., Dep. Geol. Sci., Birmingham, United Kingdom
Pages: 61-76
Published: 198901
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 31
Accession Number: 1989-062423
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
N39°40'00" - N42°30'00", W03°40'00" - W00°19'60"
Secondary Affiliation: Univ. Birmingham, GBR, United KingdomUniv. Complutense, ESP, Spain
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute.
Update Code: 1989
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