--> Geochemistry of Unusual Carbonate Facies: Is the Precambrian the Key to the Cretaceous Pre-Salt Carbonates? Part 2

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Geochemistry of Unusual Carbonate Facies: Is the Precambrian the Key to the Cretaceous Pre-Salt Carbonates? Part 2

Abstract

Many analogs have been proposed for the unusual Brazilian Pre-Salt Petroleum System from lacustrine environments to high temperature travertines. There are multiple aspects of the Brazilian Petroleum System that are difficult to reconcile with many analogs including: [1] the lateral extent and thickness of both the entire system and of individual facies belts, [2] the limited yet unusual observed carbonate textures from shrubs to spherulites to laminites, without appreciable stromatolites, and [3] the lack of carbonate skeletal fossils.

We will explore aspects of the Precambrian that make it uniquely suited to explain some of the more puzzling aspects of the Brazilian Pre-Salt Petroleum System including key controls on Precambrian facies including carbonate and evaporite chemistry in a low sulfate, high dissolved inorganic carbon (DIC) ocean system.

Successful techniques that aid in understanding the genesis and correlation of Precambrian carbonates have the potential to also unravel a carbonate system without appreciable biostratigraphy like the Barra Velha Formation. Research of Precambrian carbonates has significantly benefited from innovative methods and approaches including high-resolution chemostratigraphic analyses and detailed micro-scale textural and geochemical analyses. We will leverage geochemical data from both the Precambrian and the Pre-Salt Barra Velha Formation as well as a global Precambrian facies database. Geochemical data will include carbonate clumped-isotope thermometry and microanalytical techniques. Specific comparisons will be made between the rocks capturing the latest Precambrian from the Sultanate of Oman and the Pre-Salt Barra Velha Formation. Clumped-isotope data suggests there are clear differences between populations that follow open versus closed system behavior during diagenesis that can aide in understanding other geochemical datasets.