Factors controlling the sedimentary evolution of the kimmeridgian ramp in the north Iberian Basin (NE Spain)

M Aurell,B Bádenas

doi:10.3989/egeol.94501-2310

Abstract

The aim of this paper is to summarize the present knowledge reached by the authors on the carbonate ramp which developed in the iberian basin during Kimmeridgian times. Our results were obtained from a combined field analysis and computer modelling carried out in the north Iberian Chain (NE Spain). Extensive field analysis in the Ricia area (Zaragoza, NE Spain), resulted in a detailed mapping of the transition from inner to outerramp facies on this carbonate rampo Three facies belts may be distinguished in this rampo The outer ramp facies consists of marls and mudstones rhythmic facies. The inner ramp facies, located aboye fair-weather wave base, are dominated by coral patch reef growing. The middle ramp facies are represented by marls and micrites bearing skeletal and oolitic tempestite levels which sharply grade into high-amplitude o'olitic sandwave. Factors such as resedimentation by storms, carbonate production and relative variation of sea level acting in the Kimmeridgian ramp are also quantiphied and discussed. Most of the mud accumulated in outer-ramp areas was produced in the coral «carbonate factory» located in inner areas. Off-shore resedimentation by storm was the main agent of basinward transport of this mudo The deduced accommodation curve consists of three elements: a linear rise which satisfactorily matches the normal subsidence figures observed in intracratonic basins; a third-order cycle, that may have a regional cause and higher order cycles in the Milanckovich band, that may be eustatic in origin.

Highlights

Shallow epeiric seas covered most of the central and south european intracratonic basins during late lurassic times
The Iberian basin (NE Spain) was an intracratonic basin covered by a shallow epeiric sea
Recent computer and outcrop modelling carried out in the Kimmeridgian of the north Iberian Chain provided sorne quantitative data on this carbonate rampo A cross-section 200 Km wide, extending from inner to distal outer of the ramp, has been recently modelled by Aurell et al (1994) with the aid of the computer program CARBONATE introduced by Bosence and Waltham (1990)

Summary

Introduction

Shallow epeiric seas covered most of the central and south european intracratonic basins during late lurassic times. The Iberian basin (NE Spain) was an intracratonic basin covered by a shallow epeiric sea. A very extensive carbonate ramp developed during Kimmeridgian times in the Iberian basin. The analysis of this ramp is constrained by two important features: excellent exposition, allowing accurate reconstruction of proximal to distal ramp sections, and time framework for correlation, provided by a well-defined ammonite biostratigraphy (Aurell, 1991). Recent computer and outcrop modelling carried out in the Kimmeridgian of the north Iberian Chain provided sorne quantitative data on this carbonate rampo A cross-section 200 Km wide, extending from inner to distal outer of the ramp, has been recently modelled by Aurell et al (1994) with the aid of the computer program CARBONATE introduced by Bosence and Waltham (1990). Extensive field analysis in the Riela area (Zaragoza, NE Spain) resulted in a detailed mapping on the transition from rhythmic outer-ramp facies to oolitic and coral-reef inner ramp facies (Bádenas et a!., 1993)

Objectives

Discussion

Conclusion