Deformação neógena e suas implicações na estruturação dos campos de petróleo na região de Icapuí-Ponta Grossa (CE), Bacia Potiguar emersa

Abstract

Resumo Em falésias costeiras no extremo oeste da Bacia Potiguar (Plataforma de Aracati), a Formação Barreiras, de idade miocênica, exibe estruturas que caracterizam uma deformação de expressiva magnitude. O levantamento em detalhe da geometria das falhas e dobras que afetam a Formação Barreiras conduziu ao reconhecimento de estruturas distensionais (na localidade Ponta Grossa) e oblíquas contracionais (localidade Vila Nova, próxima a Icapuí), associadas a um sistema de transcorrências com direções NE (nestas localidades) e NW (Falha de Afonso Bezerra, na porção central da bacia). Os dados obtidos permitem caracterizar um campo de tensões de idade neógena, que gerou falhas, dobras e estruturas hidroplásticas, incluindo trama SL e zonas de cisalhamento, e reativou estruturas mais antigas, presentes na seção sedimentar neocretácea, subjacente. A reinterpretação de seções sísmicas desta região e outros dados geológicos em várias localidades da Bacia Potiguar, permitiram delinear estruturas correlatas (em estilo e regime cinemático) afetando as rochas siliciclásticas da Formação Açu e carbonáticas da Formação Jandaíra, bem como basaltos da Formação Macau, cuja idade situa-se no limite Oligoceno-Mioceno. O reconhecimento desse arcabouço estrutural demanda compatibilizar a deformação em superfície com aquela observada nas seções sísmicas, que inclui pulsos/eventos cuja idade pode ser mais antiga (intervalo Neocretáceo a Paleógeno). Este modelo traz implicações importantes para a estruturação (geometria, cinemática, idade de trapas) dos reservatórios de petróleo (especialmente os arenitos da Formação Açu, no Campo de Fazenda Belém) e dos processos de migração e armadilhamento de hidrocarbonetos neste setor da Bacia Potiguar.Palavras-chave: Bacia Potiguar, Neógeno, Formação Barreiras, campos de petróleo, Fazenda Belém. Abstract Neogene deformation and its implications for the structural framework of the oil fields in the Icapuí-Ponta Grossa (CE) region, onshore Potiguar Basin.In coastal cliffs at the western portion of the Potiguar Basin (so-called Aracati Platform), the Barreiras Formation, of miocene age, displays structures pointing to high strain deformation. Detailed mapping of faults and folds geometry in the Barreiras Formation leds to recognition of extensional structures (at Ponta Grossa village) and contractional oblique structures (Vila Nova, next to Icapuí town), both of them related to a transcurrent system bearing NE (at these locations) and NW trends (Afonso Bezerra Fault, in the central portion of the basin). These data point to a neogene stress field which generated faults, folds and hydroplastics structures, including SL fabrics and shear zones, as well as reactivated older structures in the underlying neocretaceus sedimentary section. Reinterpretation of seismic sections from this region and other geological data at several places in the Potiguar Basin outline structures which are correlated (in style and kinematic regime) throughout the siliciclastic rocks of the Açu Formation, limestones of the Janda...

Landforms and Landscape Evolution of the Equatorial Margin of Northeast Brazil

“…As observed in the Recôncavo-Tucano-Jatoba basin ), a regional unconformity (ca 20 Myear) shows that widespread erosion of rift shoulders and syn-rift sediments had taken place soon after rifting or during its last stages, before *114 Myear, followed by thermal subsidence which allowed deposition of sediments in vast lake systems beyond the limits of the syn-rift deposition, especially to the south of the Araripe basin (Socorro, Cedro, and São José de Belmonte outliers; Valença et al 2003). However, in the Potiguar basin, a few basement residual ridges locally controlled the post-rift sedimentation and still participate in the formation of oil traps in these clastic sediments (Açu sandstones: Sousa et al 2008a). …”

“…The onshore basin corresponds to a broad (100 km wide or more) and shallow synform with a NE-SW axis which is also that of secondary compressive undulations deforming the post-rift cover (Maia and Bezerra 2014b). It is filled with a thick transgressive sequence whose lower layers, the 400-800-m thick Açu sandstones (Albian-Cenomanian) rest unconformably on syn-rift or transitional deposits and incompletely beveled basement highs (Sousa et al 2008a), extending up to 30-40 km beyond the border fault of the buried rifts, on the planated Aracati Platform and Touros High Araripe and Feijó 1994;see Fig. 3.3).…”

Geological Setting: The Borborema Province

“…The onshore basin corresponds to a broad (100 km wide or more) and shallow synform with a NE-SW axis which is also that of secondary compressive undulations deforming the post-rift cover (Maia and Bezerra 2014b). It is filled with a thick transgressive sequence whose lower layers, the 400-800-m thick Açu sandstones (Albian-Cenomanian) rest unconformably on syn-rift or transitional deposits and incompletely beveled basement highs (Sousa et al 2008a), extending up to 30-40 km beyond the border fault of the buried rifts, on the planated Aracati Platform and Touros High (Castro et al 1981;Araripe and Feijó 1994;see Fig. 3.3).…”

“…As observed in the Recôncavo-TucanoJatoba basin (Magnavita et al 1994), a regional unconformity (ca 20 Myear) shows that widespread erosion of rift shoulders and syn-rift sediments had taken place soon after rifting or during its last stages, before *114 Myear, followed by thermal subsidence which allowed deposition of sediments in vast lake systems beyond the limits of the syn-rift deposition, especially to the south of the Araripe basin (Socorro, Cedro, and São José de Belmonte outliers; Assine 1994;Hegarty et al 2002;Valença et al 2003). However, in the Potiguar basin, a few basement residual ridges locally controlled the post-rift sedimentation and still participate in the formation of oil traps in these clastic sediments (Açu sandstones: Sousa et al 2008a). …”

Stepped Surfaces, Palaeolandforms and Morphostratigraphy: Reconstructing the Long-Term Landscape Evolution Since the Mesozoic

“…4.5) suggests that parts of this surface record a complex erosional history, whose last stages have been controlled by neotectonics (Bezerra et al 2001;Sousa et al 2008a) and Late-Cenozoic sea-level falls (Shimabukuro and Arai 2001;see Chap. 5).…”