CARBONATE DEPOSITIONAL SEQUENCES IN SHALLOW TO HEMIPELAGIC PLATFORM DEPOSITS - APTIAN, PREBETIC OF ALICANTE (SE SPAIN)

The Aptian deposits of the easternmost part of the Betic Cordillera in the Iberian peninsula are represented by shallow carbonate platform l imestones and outer platform hemipelagic marry sediments deposited at a inner platform-to-outer platform transition zone. The lithostratigra phic and sedimentologic study of eight Aptian sections, and their corr elation based on datations using ammonites, planktonic and benthic for aminifera, has allowed the establishment of a detailed stratigraphy of the Aptian deposits. Three formations: Llopis Formation, Almadich For mation and Seguili Formation, with notable lateral changes among them are described. The Aptian sedimentary evolution of the studied platfor ms consists of a succession of sedimentary processes, such as platform progradation, aggradation and drowning, bounded by discontinuities. T he biostratigraphic study carried out demonstrate that the present res olution of biostratigraphy is not enough to make a precise time strati graphic charr and fine dating of the sedimentary processes at the scal e of 3rd or higher order sequences. The sequential analysis have]ed us to define six depositional sequences, which make up a second order tr ansgressive-regressive cycle. The common features to these sequences a re: rare development of lowstand deposits; poorly developed transgress ive deposits; and well developed inner carbonate platforms during high stand conditions. Sequential correlation with other Aptian platforms a nd the Exxon cycle chart shows in general a good coincidence of the se quence boundaries, which would point to global or supra-regional facto rs as the cause of the sequences. Nevertheless, the internal configura tion of each sequence, and events such as the main terrigenous input a nd the platform drowning seems to be controlled mainly by local tecton ic.