Neumann, Virgínio Henrique¹, Lluis Cabrera² 
(1) Federal University Pernambuco, Recife, Brazil 
(2) Barcelona University, Barcelona, Spain

ABSTRACT: Sequential Organization of the Aptian-Albian Lacustrine System of the Araripe Basin, Northeastern Brazil

The Aptian-Albian lacustrine sequence of the Araripe Basin was defined as an interfingering set between carbonate and siliciclastic bodies. Six main episodes of lacustrine carbonate sedimentation were registered in this sequence. The mixed siliciclastic-carbonate successions were grouped into expansive-retractive sequences of different order and hierarchy. The higher order-higher frequency lacustrine cycles were developed by successive minor expansive-retractive pulses (higher frequency sequences). These main lacustrine expansive pulses, considered significant for the sequential subdivision of the lacustrine record, overflowed the depositional area, occuppying successively larger basin zones. Therefore, the last lacustrine episodes (immediately before the end of the lacustrine system evolution) reached the maximum area spread. Each intermediate order expansive-retractive sequence occurred related with small extensive-retractive pulses, which produced periods of relative stabilisation. In this turn, the whole sequence that embraced these cycles recorded a lower order lacustrine expansion. The whole stratigraphic record of expansive-retractive pulses lasted approximately 1 to 3 millions years and was divided into six episodes. Each one of these episodes were related to a significant transgression and had a duration varying from 200,000 to 500,000 years. In conclusion, it was possible to define the hierarchy of the lacustrine system record whose order resulted probably from a combination of climatic and tectonic factors that controlled the evolution of the Aptian-Albian lacustrine system of the Araripe basin. Further studies (e.g. a high-resolution analysis of the siliciclastic and carbonate lacustrine sequences) will enable one to advance in a proposal of genetic-sequential model.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.