--> Characterization of the Ladybirds Domain and Its Relationship with the Albian Hinge Line, Campos Basin – Brazil, Theodoro, Raquel; Souza Cruz, Carlos Emanoel D., #90100 (2009)

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Characterization of the Ladybirds Domain and Its Relationship with the Albian Hinge Line, Campos BasinBrazil

Theodoro, Raquel1
 Souza Cruz, Carlos Emanoel D.2

1EXP, Petrobras, Macaé, Brazil.
2
EXP, Petrobras,
Rio de Janeiro, Brazil.

The depositional history of the Quissamã Formation begins with a carbonate ramp, later modified to isolated mounded floor forms, bordered by mini-basins. The geometry of isolated mounded form is observed as much in the area of shallow carbonate ramp as in deep waters areas of
Campos Basin. It can be associated to a transitional period between tectonic processes - lithospheric extension and thermal subsidence. The carbonate ramp displacement would be related, in this model, to the reactivation of NW-SE-trending strike-slip faults associated to the differential gravitational sliding of the carbonate section on the salt. Rectilinear NE-SW-trending growth faults were generated during this phase. It is also observed that concave growth faults affected some areas of the carbonate platform. This event seems to be subsequent and it segmented the blocks again.

The imposition of a hinge line area during the Albian generated two distinct structural domains denominated as: Ladybirds Domain (LD) and Turtlebacks Domain (TD). The fundamental difference between them is the magnitude of the displacement among blocks and the abrupt drowning verified by the deposition of organic shale in the Turtles Domain. LD is characterized by salt pillows of small thickness associated to small offset growth faults. The common structures in TD are turtlebacks bordered by salt domes of great dimensions and large displacement growth faults.

The seismic-stratigraphic analysis integrated with the tectonic analysis allowed to split the Alpha Member in four 3rd order tectono-sequences in the Ladybirds Domain. Sequence 1 is characterized by isolated mounded forms with chaotic seismic facies and the top is marked by an unconformity reflector. This geometry controlled the sedimentation of the other sequences, mainly Sequence 2, which is imposed on the isolated mounded floor as prograding structures that fill out the contiguous mini-basins. Sequence 3 is marked by downlap in the contact with the growth faults and toplap on the mounded forms. It can also present concordant or onlaping facies. Sequence 4 shows concordant seismic facies and growth section close to the fault. The facies differentiation between Sequence 2 and Sequence 3 can be related to the subtle steepness towards the basin due to imposition of the Albian hinge line, associated to a progressive sea level elevation that finally drowned the whole carbonate system.

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil