Neumann, Virgínio Henrique1, Agnelo Leite Silva1
(1) Federal University Pernambuco, Recife, Brazil
ABSTRACT: Physic Stratigraphy and Deformations of the Carbonate Lacustrine System (Aptian-Albian) Outcrops of the Araripe Basin, NE Brazil
The present work studied the physical stratigraphy and deformation structures of the carbonate deposits of the Araripe Basin. Field works consisted of stratigraphical and sedimentological descriptions, collected samples and acquisition of 3D data using Ground Penetrating Radar (GPR). The identification and measurement of the deformational structures (faults and fractures) were also made. The Crato Formation presents typical facies of lakes with margin of low energy ramp type, deposited in a lacustrine transgressive system track. Two deformational events affected these rocks. The first (D1) - distensive character, generate normal microfaults (ENE and NW), loop beddings and slumps, caused by small seismic pulses. These microstructures were observed in some levels of the carbonate units. The second event (D2), of compressive character, generate thrust faults (verging SW and NE) that cut the superior part of the carbonate unit C6, representing a tectonic inversion in the basin, that resulted in a regional uplift, provoking the lowering of the level of the lake and the deposition of the evaporates of the Ipubi Formation. They also show fractures (closed and/or open, many of them filled out by calcita). The main porosity types found in the carbonate levels are fracture and vug tipes. The GPR data have very good quality, favoring the delimiting of the boundary between the marl and the laminated limestone. The interpretation of GPR data for the limestones allow the interpretation of the D1 event in this rocks.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.