Seismic-Scale Geometries and Sequence-Stratigraphic Architecture of Early Cretaceous Syn-Post Rift Lacustrine Carbonate Systems, Pre-Salt Section, South Atlantic Margins

2019 ◽  
Author(s):  
Marcello Minzoni ◽  
Alessandro Cantelli ◽  
John Thornton
Keyword(s):  
Early Cretaceous ◽  
South Atlantic ◽  
Sequence Stratigraphic ◽  
Stratigraphic Architecture ◽  
Lacustrine Carbonate ◽  
Seismic Scale

Seismic-Scale Geometries and Sequence-Stratigraphic Architecture of Early Cretaceous Syn-Post Rift Carbonate Systems, Presalt Section, Brazil

2020 ◽  
pp. SP509-2019-78
Author(s):  
M. Minzoni ◽  
A. Cantelli ◽  
J. Thornton ◽  
B. Wignall
Keyword(s):  
Early Cretaceous ◽  
Bottom Topography ◽  
Seismic Facies ◽  
Carbonate Production ◽  
Sequence Stratigraphic ◽  
Stratigraphic Architecture ◽  
Platform Margin ◽  
Lacustrine Carbonate ◽  
Sequence Boundaries ◽  
The Impact

AbstractRegional and detailed seismic stratigraphic analyses of Early Cretaceous (Aptian) presalt carbonate sections from offshore Brazil reveal the complex stratigraphic architecture of late- and post-rift lacustrine carbonate systems. The lateral and vertical distribution of calibrated seismic facies within this framework highlights the evolution through time of the carbonate system and bathymetry of the host lacustrine basin. Despite the simple, largely abiotic and microbial components, lacustrine carbonate accumulations formed complex geometries that closely resemble those observed from marine systems, suggesting that a downward tapering carbonate production profile must have occurred. The complexity of the stratigraphic architecture reflects lateral variations in subsidence patterns combined with the interference of the basement topography, palaeo-wind directions, and basinal filling patterns. Well-imaged clinoforms several hundred meters high attest to both the existence of significant lake-bottom topography, locally in excess of 800 meters, and the occurrence of deep water at time of deposition. Platform margin trajectory and vertical and lateral architecture of clinoform packages through time reveal distinct sequence boundaries that can be correlated in detail only locally, demonstrating the impact of syndepositional tectonics, and possibly recurrent isolation of smaller lakes during lowstands. Depositional models from this study fill a gap in current understanding of lacustrine carbonate systems and offer a template for exploration and appraisal of the presalt play.

scholarly journals Palaeoecological analysis of maximum flooding zones from the Tithonian (Upper Jurassic) of the Kachchh Basin, western India

Facies ◽  
2020 ◽  
Vol 67 (1) ◽  
Author(s):  
Franz T. Fürsich ◽  
Matthias Alberti ◽  
Dhirendra K. Pandey
Keyword(s):  
Upper Jurassic ◽  
Carbonate Content ◽  
Western India ◽  
Rift Basin ◽  
Benthic Assemblages ◽  
Depositional Sequence ◽  
Sequence Stratigraphic ◽  
Stratigraphic Architecture ◽  
Kachchh Basin ◽  
Rich Fauna

AbstractThe siliciclastic Jhuran Formation of the Kachchh Basin, a rift basin bordering the Malagasy Seaway, documents the filling of the basin during the late syn-rift stage. The marine, more than 700-m-thick Tithonian part of the succession in the western part of the basin is composed of highly asymmetric transgressive–regressive cycles and is nearly unfossiliferous except for two intervals, the Lower Tithonian Hildoglochiceras Bed (HB) and the upper Lower Tithonian to lowermost Cretaceous Green Ammonite Beds (GAB). Both horizons represent maximum flooding zones (MFZ) and contain a rich fauna composed of ammonites and benthic macroinvertebrates. Within the HB the benthic assemblages change, concomitant with an increase in the carbonate content, from the predominantly infaunal “Lucina” rotundata to the epifaunal Actinostreon marshii and finally to the partly epifaunal, partly infaunal Eoseebachia sowerbyana assemblage. The Green Ammonite Beds are composed of three highly ferruginous beds, which are the MFZ of transgressive–regressive cycles forming the MFZ of a 3rd-order depositional sequence. The GAB are highly ferruginous, containing berthieroid ooids and grains. GAB I is characterized by the reworked Gryphaea moondanensis assemblage, GAB II by an autochthonous high-diversity assemblage dominated by the brachiopods Acanthorhynchia multistriata and Somalithyris lakhaparensis, whereas GAB III is devoid of fossils except for scarce ammonites. The GAB are interpreted to occupy different positions along an onshore–offshore transect with increasing condensation offshore. Integrated analyses of sedimentological, taphonomic, and palaeoecological data allow to reconstruct, in detail, the sequence stratigraphic architecture of sedimentary successions and to evaluate their degree of faunal condensation.

Control of Precambrian-to-Paleozoic orogenic trends on along-strike variations in Early Cretaceous continental rifts of the South Atlantic Ocean

2019 ◽  
Vol 7 (4) ◽  
pp. SH45-SH69 ◽  
Author(s):  
Kyle Reuber ◽  
Paul Mann
Keyword(s):  
Early Cretaceous ◽  
South Atlantic ◽  
Orogenic Belt ◽  
Deep Penetration ◽  
The South ◽  
The North ◽  
Continental Rifts ◽  
Rift Zones ◽  
Seismic Reflection Profiles ◽  
Orogenic Belts

The Early Cretaceous (135–130 Ma) continental rupture of Western Gondwana to form the South American and African plates closely paralleled the elongate trends of Precambrian and Paleozoic orogenic belts. These orogenic belts were produced as a result of the Neoproterozoic convergent and strike-slip assembly of Gondwana that redeformed during later, Paleozoic orogenic events. Continued continental rifting led to the formation of conjugate, South Atlantic volcanic passive margins whose widths vary from 55 to 180 km. Along-strike variations in crustal stretching, as measured from deep-penetration seismic reflection profiles, correlate with parallel and oblique orientations of rifts relative to the trend of the orogenic, basement fabric. Where orogenic fabric trends parallel to the north–south South Atlantic rift direction such as in the Dom Feliciano orogenic belt of Uruguay and Brazil and the Kaoko Uruguay/Brazil and Kaoko orogenic belt of Namibia, we observe narrow (55–90 km) rift zones with modest continental beta factors of 2.5–3.5 because smaller amounts of rifting were needed to stretch the weaker and parallel, orogenic, basement fabric. Where the basement fabric trends near-orthogonally to the north–south South Atlantic rift direction such as in the Salado suture of Southern Uruguay and the Damara Belt of Namibia, we observe wider (185–220 km) rift zones with higher beta factors of 4.3–5 because greater amounts of stretching were needed to rupture the orthogonal, orogenic, basement fabric. The rift-oblique Gariep Belt intersects the South Atlantic continental rupture at an intermediate angle (30°) and exhibits a predicted intermediate beta factor of 4.0. A compilation of published beta factors from 36 other rifted margins worldwide supports the same basement-trend-degree of stretching relationship that we have developed — with rift-parallel margins having lower beta factors in a range of 1.3–3.5 and rift-orthogonal or oblique margins having higher beta factors in a range of 4–8.

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