Study details a glance
Biostratigraphy
Review
New
Biostratigraphy
Analyses
Palaeoenvironments
& Facies
Provenance
25
Wells
Eocene
Palaeocene
Key points
- Palynology a previously neglected stratigraphic and palaeoenvironmental tool across the GoM.
- Quantitative new palynological analysis of >2,500 samples, integrated with foram and nannofossil data to generate an integrated biostratigraphic framework from base Paleocene to the basal Oligocene
- Palynology-led correlation helps identify spatial variations in vegetation along the Paleocene-Eocene paleo-coastline, that will help to determine sedimentary provenance within the inboard and outboard areas of the deepwater GoM.
Background
The Lower Tertiary play has become a key focus for exploration in the deep water Gulf of Mexico. The thick clastic Paleocene to Early Eocene succession comprises deep water turbidite fan systems derived from a paleo-shelf that extended across the modern day Gulf Coast. Time equivalent fluvial, deltaic and shallow marine sandstones of the Wilcox have long been recognized as important petroleum plays across the Gulf Coast. Biostratigraphic studies of the Lower Tertiary have traditionally been carried out using forams and nannofossils and yet calcareous fossils are generally quite scarce, especially within the basal Eocene and Paleocene succession where terrigenous fossils overwhelm the restricted marine fossil assemblages. Additionally, published references concerning palynology tend to focus more upon the terrigenous spores and pollen. Only limited reference has been made to the autochthonous marine microplankton component of palynofloras, especially dinocysts, and there is only limited integration between the marine and non-marine palynofloral datasets.
Project
The main objective of the project is to build an extensive biostratigraphic database for wells and key outcrops across the Gulf Coast in order to refine the biostratigraphic breakdown of the Eocene to Paleocene interval. Emphasis will be placed on the previously underutilized tool of palynology, with quantitative analyses to be carried out on over 2500 samples. The results will be integrated with foram and nannofossil data (including selected new analyses and published data) in order to produce a fully integrated biostratigraphic framework from the base of the Paleocene to the basal Oligocene. A reevaluation of the lithologic characteristics of the formations will also be carried out to help gain a greater understanding of their sedimentology, thickness and facies distribution.
Well and Outcrop sampling & analysis
The project will involve analyzing the EocenePaleocene intervals of 25+ wells samples and a selection of key outcrops of known age / stratigraphic position. Companies that agree to pre-commitment to the project will be offered the chance to include up to three wells of their choosing (conditional upon providing both samples and logs). Fully quantitative palynological analysis will be undertaken using processing and counting techniques developed specifically to capture both the marine and non-marine components of the palynofloral assemblages. Quantitative foram and nannofossil analyses will also be undertaken on suitable horizons to help constrain the palynology to absolute ages. Existing data will also be used where ever this is made available.
Provenance
Attention will be given to the paleobotanic characteristics of the spores and pollen recorded from the outcrops and wells analyzed for the study since these largely reflect the parent plant communities. The variations that exist in modern day vegetation across the study area from west to east are likely to be observed in some fashion within the Early Tertiary. Mapping out the distribution of paleo-plant communities from west to east will aid recognition of sedimentary provenance in the offshore deep water GoM.
Palynology
- The PetroStrat Wilcox Palynological Zonation uses allochthonous terrestrially derived pollen & spores and autochthonous marine dinocysts.
- Important to utilize non-marine and marine palynomorphs. Counting techniques cater for both.
- Palynology provides the best stratigraphic tool when the ocean chemistry is calcite deficient. Restricted circulation in a basin will often actually benefit the discipline as dyserobic or anoxic bottom conditions precludes the establishment of benthic communities that eat accumulated organic matter (palynomorphs).
- Palynology integrated with the forams and nannoplankton will provide the highest resolution Biostratigraphic framework.
Integration and modelling
Biostratigraphic results will be tied back to lithologic, log and sedimentologic data where these can be obtained or determined. A series of cross-sections and maps will be generated.
