BayCEER Workshop 2008

Obtaining the basic accretional unit of a carbonate platform: an Early Aptian example from the western Maestrat Basin (E- Iberian Chain; E- Spain)

Abstract: A detailed study of a lower Aptian shallow-water marine sedimentary succession in the western Maestrat Basin (E- Iberian Chain; E- Spain) has served as an example in order to present a procedure to characterize the stratigraphic architecture of a basic accretional unit of a carbonate platform. The steps taken are based in field work, sedimentary analysis, interpretation of panoramic photos of outcrops displaying platform margin geometries, line drawing and lithofacies identification. The basic building block obtained corresponds to a high order depositional sequence bounded by maximum regressive surfaces, and develops during three different sea-level pulses: early transgressive, late transgressive and regressive. During these eustatic fluctuations, deposition of six different lithofacies assemblages occurs along four specific sedimentary environments: platform, platform margin, slope and basin. The early transgressive pulse stage is mainly represented by an orbitoline-bloom. The late transgressive pulse stage is characterized by a building-up episode dominated by rudists, corals, orbitolines and ammonites. The increase in energy in hydrodynamics conditions associated with the subsequent regression results in debris flows deposits. The carbonate platform studied is interpreted as a flat topped non rimmed shelf. The methods used could be of interest for other field work related disciplines implying detailed cartography, field mapping and panoramic views.