BrasCretOst II

BrasCretOst^(*) II: Interactive Visual Identification Tool for Pre-Salt Ostracods (Local Stages from Buracica to Alagoas) – VITO

*Brazilian Cretaceous Ostracods

Duration. 11/2025–10/2027

Project Type. Service contract research project funded by PETROBRAS (Petróleo Brasileiro S.A.), research center Centro de Pesquisas Leopoldo Américo Miguez de Mello (CENPES), Rio de Janeiro, Brazil.

The so-called “Pre-Salt” successions comprise a series of geological formations having formed in ancient lakes during Early Cretaceous times between eastern South America and West Africa due to the early successive breakup of Gondwanaland (between ca. 143–115 millions of years ago). During the time interval between ca. 115–110 million years ago, as the rifting continued, marine waters of the – then separated – South Atlantic and Central Atlantic oceans successively advanced towards equatorial regions. Resulting from a combination of factors including the position at – or proximal to – equatorial regions, a global greenhouse climate, generally low water depths and continuing continental drift and subsidence, much of the sea water evaporated resulting in major successions of evaporite (salt deposits) of up to 2000 m. The organic-rich deposits of these ancient long-term lakes, having developed before the evaporite deposition are therefore summarized under the term “pre-Salt” deposits. Today, they comprise a significant proportion of the world’s hydrocarbon reserves and are, thus, of interest for hydrocarbon exploration and exploitation – particularly since they contain light oil of high quality, of high commercial value and of fundamental economic importance for eastern and northeastern South American countries such as Brazil.

Since the respective deposits are located 100–150 km offshore Brazil in ultra-deep waters of the Atlantic Ocean (~ 2000 m) as well as under ca. 1000 m of “post-Salt” deposits and ca. 2000 m of salt deposits, target depths for exploration and exploitation range between 5000 m to 7000 m. Therefore, exploration and exploitation of the oil face several technical, environmental and economic challenges. The Brazilian majority state-owned Oil Company Petrobras leading in this field worldwide.

Ostracods are mainly aquatic microcrustacean, typically around 1 mm in size, with a calcified bivalved shell, the carapace, that today inhabit virtually all aquatic environments, both marine and non-marine.

Video 1. Living ostracods of an asexual, all-female population of Heterocypris incongruens kept in an aquarium for several years – here feeding on chicken meat (© B. Sames). The original sample derived from quarry Kerschenbachtal, north of Sankt Veit an der Gölsen, Lower Austria.

They have an excellent fossil record and their small size, morphological variability, high diversity and wide distribution renders them excellent candidates for a wide array of applications. In non-marine to transitional/marginal marine sedimentary rocks, such as those of the Pre-Salt interval, ostracods are very common (see example in Fig. 1) and among the most useful group for biostratigraphic application (relative age determination and correlation with contemporaneous deposits) and paleoenvironmental reconstruction of respective non-marine aquatic ecosystems. These applications are of major interest for hydrocarbon exploration, i.e., to reduce costs by supporting risk assessment of the suitability of rock successions and areas to be explored and age/correct depth estimation during the drilling of exploration wells.

Since any application of organisms can only be as good as the taxonomy (classification) it is based on, and the fact that many comprehensive taxonomic studies of pre-Salt ostracods of Brazil and West Africa are dated, an essential up-to-date detailed taxonomic revision of ostracods of the younger pre-Salt interval based on modern integrated paleobiology and high-quality pictorial and graphic documentation has been conducted in the preceding project BrasCretOst I (2020–2024).

Fig. 1. Petrobrasia diversicostata Krömmelbein (© Petrobras, picture by B. Sames). Scanning electron microscopy picture of a well-preserved fossil carapace in right lateral view, anterior end to the right. The genus has been named after Petrobras.

Now that a lot of data has been and is continuously created, the current project BrasCretOst II now approaches further essential aspects towards the better utility of the ostracods: The management as well as the efficient communication and utilization of the available and future data in a practical and modern way – without neglecting high scientific standards. Within this project, a modern, easily accessible graphic database will be developed that is intended to be used as interactive visual identification tool for the respective ostracods (VITO). Considering that practical work during exploration on drilling platforms or ships is often conducted by non-specialists, this application will be designed for a broader audience, comprising different levels with top-down increasing scientific complexity that build upon each other, all accessible via the intuitive graphic user interface. This means that a visual approach and low complexity have priority, but full detailed scientific information is integrated and can be accessed if desired. The web-based database shall be complemented by an easily intelligible editor for data input as well as by an interactive training tool. The integration of artificial intelligence is to be considered and tested, particularly during the data input process via the editor such as for data quality and redundancy survey during data input.

The ultimate goal of project BrasCretOst II is to combine maximum scientific quality with optimal utilization of pre-Salt ostracods accessible to a broad variety of users which in turn facilitates an optimization of the application of these ostracods in exploration as well as the optimization in both quality of the respective ostracod’s taxonomy and scientific further education in the field of ostracod taxonomy and application.