Paleozoic Carbonates in Foreland Basin Settings: Northern Pricaspian Basin (Kazakhstan) and Cantabrian Zone (Spain)
Jeroen A. M. Kenter and Paul (Mitch) Harris
Chevron Energy and Technology Company, 6001 Bollinger Canyon Road, San Ramon, CA 94583-2324, USA
Tengiz field is an isolated carbonate buildup in the southeastern Pricaspian basin, containing a complete Late Famennian to Early Bashkirian platform succession that was deposited in a relatively stable but rapidly subsiding fore land basin setting facing a thrust belt to the south. Since the Famennian, the platform aggraded and periodically back stepped resulting in approximately 800 m (2625 ft) of relief above the Famennian platform, followed by up to 2 km (1.2 miles) of Serpukhovian progradation. Vertical trends in relative shoaling and deepening, recorded exposure and/or erosional events and biostratigraphy provide a relative sea level record of punctuated sea level falls and rises that is made up of 2nd and 3rd order sequences which are superimposed by higher (4-5th order) frequency platform cycles.
Though several of the observed sea level low stands correspond to 3rd order eustatic sequences on the EPR curve, the influence of rapid changes in the paleobathymetry of the fore land basin, which caused significant thickening of sequences and drowning in the late Devonian elsewhere in the basin, appears to have a strong influence on the regional sequence stratigraphic framework. This paper will address the interplay between subsidence and recorded sequences in such fore land basin settings and compares the Pricaspian Basin evolution with that of a – nearly - age-equivalent foreland basin in Northern Spain.
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