Sequence Stratigraphy of Continental Successions, Multi-Approach Insight From Source-to-Sink Studies in the South Pyrenean Foreland Basin, Spain

Abstract

In the intent to unravel Earth's sedimentary history, sequence stratigraphy has proven to be a powerful tool providing useful insights on the sedimentary record and its response to external forcing (Milankovitch cycles, eustasy variations, climate change and tectonics). Sequence stratigraphy provides theoretical models allowing to predict the nature and timing of surfaces and sedimentary packages from marine to continental environments, thus contributing to global source-to-sink comprehension of Earth's dynamic response to environmental change. In recent years, although classic sequence stratigraphy models have evolved thanks to ground-truthing studies and advances of subsurface imaging, correlations of marine and continental stratigraphies at high-resolution remain challenging to establish on the field. Consequently, the debate about the nature of the factors controling stratigraphic patterns fluvial successions are still debated (Sømme, 2009). To address this problem, a mapping and multi-proxy approach was undertaken in the Tremp-Graus and Ainsa basins in the South-Pyrenean foreland basin. We focused on the early Eocene Castissent formation, a major fluvial excursion and its deep marine time-equivalent; the turbiditic systems of Fosado, Arro and Gerbe with the intent to obtain a high resolution deposition timing of the fluvial and marine sand bodies. Based on fieldwork and previous mapping, we use carbon stable isotopes on bulk rock carbonates to trace a climatic signal in the sedimentary record on three sections representing the distal deep marine depositional system, the transitional shallow marine deltaic systems, and the fluvial feeder system at three different loci in the basin. This allows us to correlate environmental signals across the source-to-sink profile and discuss sequence stratigraphic models for the relative timing of deposition of sand in these different segments. Moreover, our high-resolution correlation permits us to provide a tentative budget of sediment volumes distributed in the different segments of the source-to-sink profile during deposition of the Castissent interval. The results and interpretations are supported by geochemistry of major and trace elements as well as clay analysis to constrain climatic factors. Finally, an analogy between the Eocene South Pyrenean δ13C record and modern carbon isotope distribution is made in order to compare and create a predicting tool for ancient source-to-sink systems.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017