Interplay of orbital forcing and tectonic pulses in the Cambrian Iberian platform, NE Spain |
| |
Authors: | J J Álvaro E Vennin A Muñoz B Sánchez-Valverde J L Ojeda |
| |
Institution: | (1) UPRESA 8014 CNRS. Cité Scientifique SN5, Université de Lille I, F-59655-Villeneuve d'Ascq. France e-mail: Jose-Javier.Alvaro@univ-lille1.fr Tel.: +33-32-0336392 Fax: +33-32-0436900, FR;(2) Laboratoire Géologie, Muséum National d'Histoire Naturelle, 43 rue Buffon, F-75007 Paris, France, FR;(3) Departamento de Ciencias de la Tierra, Universidad de Zaragoza, E-50009 Zaragoza, Spain, ES;(4) Departamento de Métodos Estadísticos, Universidad de Zaragoza, E-50009 Zaragoza, Spain, ES |
| |
Abstract: | The stratigraphy of carbonate/shale couplets, cycles and cycle-stacking patterns in a Cambrian shallow water platform (Iberian
Chains, NE Spain) are related to sea-level changes driven by orbital forcing and by tectonic pulses. The interplay of both
effects can be discriminated in the Iberian fault-controlled platform, in which the tectonic activity can be analysed by accurate
and detailed biostratigraphic correlations based on trilobite zonation. The stratigraphic hierarchy of rhythmically interbedded
limestones and shales, in two coeval but structurally separated geodynamic settings, yields cycle ratios of 1.44 :1. This
ratio is supported by time thickness and spectral analysis, which is based on a graphic method of analysis: the Map of Grey
Lines. The cycle ratio seems to be evidence for orbital forcing by obliquity and precession cycles predicted for early Paleozoic
time. Carbonate/shale couplets, the smallest rhythmic units recognisable in the field, represent short-term, periodic fluctuations
in supply of terrigenous sediments and carbonate productivity of uncertain origin, which could be associated with one of several
harmonics of the former orbital cycles. The pulsating tectonic activity was approximated by using a quantitative analysis
of tectonically induced subsidence (Shaw method). Recurrence frequencies of tectonic pulses were estimated and dated by biostratigraphy.
As a result, tectonic disturbances in the Cambrian Iberian platform show an episodic periodicity comparable to that of orbital
eccentricity cycles, which could mask their recognition.
Received: 15 November 1999 / Accepted: 9 February 2000 |
| |
Keywords: | Cyclicity Tectonism Palaeogeography Iberian Chains Cambrian |
本文献已被 SpringerLink 等数据库收录! |
|