Architecture and processes of deep-marine sandbodies,udAinsa basin, Spanish Pyrenees

摘要

The integration of sedimentology, architectural element analysis andudstratigraphy has been applied to characterise the complex depositional history of theudAinsa basin fill, and document the evolution of the proximal parts of eight, channeliseduddeep-marine systems of the Hecho Group. The Eocene Ainsa basin provides anudopportunity to research three-dimensional organisation through an entire deep-marineudslope to proximal basin-floor fill, and records a range of depositional processes andudsedimentary environments in a spatio-temporal framework.udThe Hecho Group can be divided into two tectono-sequences, TS-I and TS-II.udTS-I accumulated during a period of strong flexural subsidence ahead of the main thrustudfront during a foredeep setting, whereas TS-II represents a more mature stage of basinuddevelopment, characterised by anticlinal uplift as the basin became detached andudevolved into a complex thrust-top basin. Four discrete systems and their constituentudsandy sequences compose each tectono-sequence. The sequences comprising TS-I showudvery little lateral migration due to high basin-scale accommodation; however, westwardudlateral offset stacking is observed in the sandy sequences of TS-II due to theuddevelopment of intrabasinal growth anticlines. These structurally controlled trendsuddemonstrate that the timing of tectonic processes operated at frequencies consistent withudthe accumulation of the depositional systems.udDepositional systems range between ~60–700 m thick, and were deposited in audnumber of deep-marine settings that include mid-slope canyons, lower-slope erosionaludchannels and proximal basin-floor channel systems. Temporal variation in depositionaludstyle and architecture between systems reflects the tectonic regimes operating during theudaccumulation of the tectono-sequences. Alternatively, the 22 sandy sequences wereudcontrolled by the ~400 kyr Milankovitch frequency with higher-frequency orbital bandsudinfluencing the accumulation of channel complexes and channel fill elements.udAn important outcome of this study is the recognition of a complex hierarchicaludinteraction between global climatic and tectonic drivers, operating at a variety of timeudscales to control the timing of coarse clastic sediment supply and the architectural stylesudof depositional systems.