Section
Physical Sciences
Abstract
The Lower Cretaceous sedimentary rocks of the Coastal Sedimentary Basin of Tanzania crop out in the Wami and Mandawa basins and are stratigraphically similar to the reservoir rocks hosting gas at Songo Songo. This study examines the relationship between facies and diagenetic processes in outcrops from the study area. Outcrop description and petrographic analysis by using optical and scanning electron microscopy (SEM) were used to identify facies and diagenetic alterations. Sixteen facies were identified, including siliciclastic facies: conglomerate (Gm), sandstones (St, Sp, Sm, Sh, Sr), siltstone and mudstone (Fm, Fl); and carbonate facies are packstone (Lsp, Lspc, Lspg, Lspo), grainstone (Lsg, Lsgf), wackestone and calcareous mudstone (Lsw, Lsm). Siliciclastics were deposited in fluvial–deltaic to marine settings, while carbonates display facies related to intertidal, shallow, and restricted marine environments. The main identified diagenetic components are compaction, cementation, replacement, and dissolution, occurring in eogenesis, mesogenesis, and telogenesis regimes. Diagenetic events were controlled by lithology, pore fluid composition, burial depth, and surface conditions. Siliciclastic porosity averages 5–15%, whereas carbonate facies exhibit 2–20% porosity, dominantly formed by alteration and dissolution of unstable minerals. In comparison to Songo Songo reservoir rocks with porosity >20%, the studied rocks display moderate reservoir quality.
Recommended Citation
Saroni, Justina James
(2026)
"Distribution of diagenetic alterations in Lower Cretaceous strata of the Tanzanian coastal sedimentary basin,"
Tanzania Journal of Science: Vol. 52:
Iss.
3, Article 22.
Available at:https://doi.org/10.65085/2507-7961.2381
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This work is licensed under a Creative Commons Attribution 4.0 License.
