Conferencia. Secciones condensadas y máximos transgresivos.Una relación equívoca.

Abstract

Sequence stratigraphy allows to elucidate the time-space organization of the deposits in the sedimentary basins. However, the relative distribution of the unconformities as well as of the condensed sections can neither be used as a diagnostic criteria for a particular paleogeographic setting, nor as an indicator of eustatic changes towards deeper conditions related to maximum regional transgressions. Condensation processes can occur during maximum transgressive stages in the distal portion of the basins, but condensation processes are also present along maximum regression stages in the shallowest portions of the platforms. Condensed sections are not only related to the maximum flooding surfaces but also to the systems tracts generated under low sea level conditions. The stratigraphic, sedimentary and taphonomic condensation concepts are useful to analyze the sediments distribution patterns in the sedimentary basins, and also to estimate the lateral and vertical variations in rates (VTS) and sedimentation velocities (VVS). Against the most usual interpretation about the development of the shallowing-upward sequences or parasequences, the maximum rate, velocity, and amount of accommodation values, as well as the highest relative depth, correspond to the lowest levels of these sequences, and are decreasing towards the top. The distinction between processes of each one of the three categories of condensation allows to make the prediction that sedimentary and stratigraphic condensation degrees Will be higher towards the distal portions of the platforms, whilst the stratigraphic condensation processes without sedimentary condensation Will show the maximum intensity and frequency in the shallowest portions of the platforms. Condensed sections can serve to evidence eustatic cycles and the establishment of temporal correlations. However, if the condensed sections from the middle and distal portions of the basins, generated during maximum transgressions, are correlated with the condensed sections ofthe proximal zones, due to regressive maximums, the temporal correlations can be as diachronous as the most retrogradational or progradational facies developed in the shelves