Skip to Main Content
GEOREF RECORD

Orocline formation at the core of Pangea; a structural study of the Cantabrian Orocline, NW Iberian Massif

J. Shaw, S. T. Johnston and G. Gutierrez-Alonso
Orocline formation at the core of Pangea; a structural study of the Cantabrian Orocline, NW Iberian Massif
Lithosphere (August 2015) 7 (6): 653-661

Abstract

The Variscan orogen provides the European record of the late Paleozoic continental collisions that culminated with formation of the supercontinent Pangea. An S-shaped pair of isoclinal coupled oroclines characterizes the Variscan orogen of the Iberian Massif. Though oroclines are common features of the world's orogenic belts, the mechanisms that drive oroclinal formation, and the manner in which these continental-scale vertical-axis folds of orogens are accommodated are poorly understood. The northerly Cantabrian and the southerly Central Iberian oroclines are structurally continuous and pericontemporaneous, suggesting that they formed in the same fashion. Exposures of the Ediacaran Narcea Slates within the so-called Narcea antiform trace a 150-km-long arcuate belt around the 180 degrees Cantabrian orocline. In the western flank of the Narcea antiform, the Narcea Slates are characterized by a penetrative steep to vertical, rough to slaty cleavage (S1) and subparallel 2-km-wide reverse shear zones with a penetrative fabric (S2) that are postdated by asymmetric meso- to outcrop-scale vertical-axis folds (plunge >65 degrees ) with a dominant vergence toward the oroclinal hinge; i.e., fold geometry is dominantly dextral (Z-shaped) in the southern limb of the Cantabrian orocline and dominantly sinistral (S-shaped) in its northern limb. Axial planes are consistently steeply dipping, but they are typically oriented at a high angle to S1/S2 and are therefore variable in strike about the orocline hinge. Vertical-axis folds affecting the Narcea Slates are of the appropriate scale and geometry to be interpreted as parasitic structures developed in response to a component of flexural shear within the limbs of the forming Cantabrian orocline. A model of formation of the Iberian coupled oroclines by buckling accommodating significant orogen-parallel shortening along an initially linear Iberian Variscan belt is therefore supported, providing new insight into the complexities associated with the final stages of Pangean amalgamation.


ISSN: 1941-8264
EISSN: 1947-4253
Serial Title: Lithosphere
Serial Volume: 7
Serial Issue: 6
Title: Orocline formation at the core of Pangea; a structural study of the Cantabrian Orocline, NW Iberian Massif
Affiliation: University of Victoria, School of Earth and Ocean Sciences, Victoria, BC, Canada
Pages: 653-661
Published: 20150824
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 58
Accession Number: 2015-089169
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: IGCP Project No. 597, 574
Illustration Description: illus. incl. geol. sketch maps
N42°30'00" - N43°45'00", W07°00'00" - W05°30'00"
Secondary Affiliation: Universidad de Salamanca, ESP, Spain
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201538
Program Name: IGCPInternational Geological Correlation Programme
Close Modal

or Create an Account

Close Modal
Close Modal