Relation between stratigraphic architecture and multi-scale heterogeneities in carbonate platforms: The Barremian–lower Aptian of the Monts de Vaucluse, SE France

Abstract

Understanding the relationship between multi-scale sedimentary heterogeneities and the stratigraphic architectures of carbonate platforms improves the interpretation of paleoenvironmental evolution in time and space. Such an approach improves the prediction of the spatial distribution of reservoir properties within carbonate stratigraphic units.The reservoir-scale stratigraphic anatomy and the growth history of a Barremian–Aptian carbonate platform (Monts de Vaucluse, SE France) was based on 1) high-resolution measured sections on outcrops, 2) detailed microfacies analyses, 3) paleoenvironmental interpretations, 4) biostratigraphy using rudist bivalves, foraminifera, calcareous algae, and locally echinoderm and ammonites, and 5) sequence stratigraphic interpretations with a special focus on the identification of discontinuity surfaces with a significant stratigraphic correlation potential and critical environmental meaning.The platform succession consists of subtidal (mainly infralittoral) with rare inter- to supratidal deposits. Thirty types of elementary facies, grouped in 12 facies associations, have been defined. The vertical and lateral changes in paleoenvironments together with the development of remarkable stratigraphic surfaces, such as subaerial exposures, marine erosional surfaces, and drowning surfaces, allow the definition of five stratigraphic sequences ranging from the late Barremian to the earliest Aptian.These depositional sequences can be grouped into two distinct carbonate sedimentary systems characterized by specific sedimentary profiles and skeletal and non-skeletal components: 1) a carbonate platform with stronger hydrodynamic gradients, rimmed by a narrow belt of high energy deposits with corals and rudistid rudstone facies and 2) a carbonate ramp dominated by orbitolinids fine-grained facies, including an elongated high energy oolitic shoal. The two-dimension architecture of the depositional sequences (dimensioned geometries, thickness and facies variations) and the morphology of the shelf reflect a strong interaction between tectonic (differential subsidence), sediment production and global environmental conditions. At the km-scale, the “Gorges de la Nesque” stratigraphic motif could represent a nested stratigraphic structure within the large-scale model, which could be implemented for up-scaling petrophysical properties from the well to a full-field model. The association of coral facies to the rudist-dominated system in the Provence platform is a very clear proxy of the polarity of the carbonate platform and is critical for subsurface facies-property modeling based on well data. Finally, at the global scale, the stratigraphic architecture and the step-wise drowning events of the Provence platform confirm and document the precursor events associated with environmental perturbations that affected the carbonate factory prior the Oceanic Anoxic Event 1a (OAE1a).