Paul R Clarke1, Peter Turner2
(1) The University of Birmingham, Birmingham, United Kingdom
(2) The University of Birmingham, Birmingham
ABSTRACT: The High Resolution Facies Architecture And Sequence Stratigraphy Of Lower To Middle Triassic Red Beds From Central Spain: An Outcrop Analogue For The Triassic Fluvio-lacustrine Deposits Of The UK North Sea
It is of paramount importance that the architecture of reservoir quality lithologies is comprehensively understood. Nowhere is this more important than in the exploration and development of fluvio-lacustrine reservoirs where determining sandstone width, thickness, interconnectedness and reservoir compartmentalisation are fundamental for assessing how a system will charge, and ultimately, drain.
The Lower to Middle Triassic (Buntsandstein) succession of Central Spain is selected as an outcrop analogue for the varied facies architectures inherent to the Triassic of the UK North Sea. This well exposed red bed succession records the evolution in fluvial style from low-sinuosity 'braided' to high-sinuosity 'meandering' channelisation. This transition was a function of rising base-level, generated by transgressive Tethyan waters that culminated in the Muschelkalk.
A basin-scale magnetostratigraphic correlation has enabled the construction of chrono- and lithostratigraphic sequences; this detailed 'time-stratigraphic' framework allows sequence stratigraphic principles to be applied.
Sequence stratigraphy, utilising base-level as an equilibrium profile, indicates that the amalgamated, low sinuosity, multi-storey sand bodies resulted from lowstand conditions, while transgressive conditions produced fluvial aggradation and an isolated, single-storey, compartmentalised sequence. Highstand systems tracts produced high sinuosity, multi-lateral sand bodies of basin-wide extent. Sand body geometry is a process-based response to the depositional style; however the stacking patterns that produce basin-scale facies architecture are allostratigraphically controlled.
Magnetostratigraphy is recognised here as a valuable tool for time correlation, a fundamental prerequisite of sequence stratigraphy often lacking in non-marine strata. It is now suggested that a new nomenclature be devised to reflect the differing needs of non-marine sequence stratigraphy.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado