Facies analysis and correlation of high‐order sequences in middle–outer ramp successions: variations in exported carbonate on basin‐wide δ13Ccarb (Kimmeridgian, NE Spain)

Abstract

AbstractCarbonate mud that accumulated in the deep parts of a late Kimmeridgian carbonate ramp (Iberian Basin, NE Spain) was partly derived by resedimentation from shallow water production areas. High‐frequency sea‐level changes, probably driven by climatic changes in tune with precession and short‐eccentricity cycles, affected carbonate production and the amount of exported sediment. Facies analysis and correlation of three outcrops located in middle and outer ramp settings allows a comparison of high‐order sequences (bundles of beds and sets of bundles) across a ramp transect and an assessment of the carbonate factory. Analysis of the storm deposits found in middle ramp settings identifies deepening to shallowing high‐frequency cycles based on the level of exported carbonate. In outer ramp areas, many of the bundles exhibit a thinning trend, indicating a progressive decrease of carbonate production and hence, carbonate export during periods of high‐frequency sea‐level rise. δ13Ccarb values show a gradual increase through the studied long‐term transgressive interval ranging from 1·5‰ to 2·8‰. Within this long‐term evolutionary trend, short‐term δ13Ccarb fluctuations occur that correspond with some of the high‐order cycles defined from sedimentary facies analysis. These short‐term δ13Ccarb shifts are interpreted as shifts in carbonate export from shallow reef regions to the outer ramp. A consequence of this study is that variation in δ13Ccarb can be used for correlation in outer ramp successions, at least on a basin‐wide scale.