Mid-Cretaceous stratigraphy and micropalaeontology of the coastal basins of Tanzania

• Main Author: Mweneinda, Amina
• Format: Thesis
• Language: English
• Published: 2014
• Subjects: QE Geology; North Atlantic
• Online Access: https://orca.cardiff.ac.uk/id/eprint/59583/; https://orca.cardiff.ac.uk/id/eprint/59583/1/Amina%20Kerga%20Mweneinda%20thesis.pdf; https://orca.cardiff.ac.uk/id/eprint/59583/2/Electronic%20disertation%20forms-Amina.pdf

The aim of this study was to develop a stratigraphic framework for the ‘mid-Cretaceous’ (Aptian-Cenomanian) strata of the Tanzanian coastal basins and, in particular, attempt to identify and recover the Aptian/Albian boundary (the interval of ‘Oceanic Anoxic Event’ 1b) for detailed investigation. Six pre-existing industry boreholes were selected for detailed micropalaeontological study (planktonic and benthic foraminifera) using modern taxonomic and biostratigraphic concepts. These sites are arranged approximately along strike from one another, and their stratigraphy and palaeoenvironmental histories are established. Information from these boreholes and many additional surface outcrop samples was used to select a location for two new boreholes which were expected to penetrate through the Aptian/Albian boundary (Tanzania Drilling Project [TDP] Holes 40A and 40B). In total, twelve planktonic foraminiferal biozones and two subzones of the upper Aptian - upper Cenomanian from the coastal basin of Tanzania are illustrated and described for the first time. Intra- and inter-basinal correlations are achieved using a combination of lithostratigraphy, biostratigraphy and carbon isotope stratigraphy. The planktonic and benthic foraminiferal assemblages are found to be similar to those reported from the Atlantic and Europe, and hence can be correlated to global records. An assessment of relative sea level change is achieved through benthic foraminiferal biofacies and planktonic: benthic ratios. Biostratigraphy of TDP Holes 40A and 40B was developed from the foraminiferal assemblages. A tentative correlation of the carbon isotope stratigraphy is made to the isotope records from Ocean Drilling Program Site 1049 in the subtropical Western North Atlantic and Vocontian Basin, southeast France. These investigations show that lowermost part of the Albian is missing in TDP Holes 40A and 40B which may explain why no organic carbon-rich shales relating to Oceanic Anoxic Event 1b were encountered. More expanded and organic rich ...