69-2 Microfacies and Foraminiferal Biostratigraphy as Proxies for Eocene Depositional Dynamics along the Western Indian Plate, Balochistan, Pakistan

Session: Joint SGD-SEPM-IAS Focus on the Sedimentary Record of Climate Change (Posters)

Presenting Author:

Authors:

Abstract:

This study provides a concise biostratigraphic framework for the Middle Eocene Ghazij Group (Shaheed-Ghat, Toi, and Drug formations) in Nosham, Baluchistan, Pakistan. Detailed field logging and petrographic analysis of 57 samples from these formations reveal diverse microfacies and well-preserved foraminiferal assemblages crucial for stratigraphic correlation. The Shaheed-Ghat, Toi, and Drug formations, with thicknesses of 540m, 210m, and 400m respectively, display a range of lithologies including shales, sandstones, limestones, and coal seams.

The samples collected along the stratigraphic succession were analyzed petrographically to identify microfacies and unravel diagenetic overprints. The diversity of identified microfacies, particularly those dominated by foraminiferal assemblages, provides key biostratigraphic markers. The Shaheed-Ghat Formation comprises ten sub-microfacies including Miliolid and Planktonic mudstones and Wackestones, Nummulitic facies, and Alveolinidae-bearing lithologies. The Toi Formation features both Wackstone and Packstone microfacies, notably with abundant nummulitic and miliolid foraminifera, while the Drug Formation is distinguished by benthic foraminiferal packstones and nummulitic wackestones.

Biostratigraphic analysis is anchored by the rich foraminiferal content across the formations. Key taxa such as Nummulites sp., Lockhartia sp., Miscellanea sp., Discocyclina sp., Assilina sp., miliolids, and planktonic genera including Subbotina sp., Globotruncana, Globigerina sp., and Morozovella allow precise correlation and age assignment. The identified assemblages indicate an early to middle Eocene age for the Ghazij Group and facilitate subdivision of the successions into biostratigraphic zones, supporting their regional correlation within the western Indian Plate margin.

Integration of microfacies and foraminiferal biostratigraphy reveals that the Shaheed-Ghat Formation was deposited in inner ramp lagoon to middle ramp settings, the Toi Formation in high-energy proximal inner ramp environments, and the Drug Formation from lagoon to outer ramp conditions. Diagenetic processes, including micritization, cementation, compaction, dissolution, and stylolitization, have variably overprinted the primary fabrics but do not obscure the biostratigraphic utility of the foraminiferal assemblages. Porosity estimates, particularly in the Drug Formation, reflect post-depositional alterations and indicate limited reservoir potential.

Sequence stratigraphic analysis, informed by biostratigraphic and microfacies data, identifies multiple transgressive-regressive (T-R) cycles within the Toi and Drug formations, further refining the temporal and environmental evolution of the Ghazij Group. This biostratigraphic framework enhances our understanding of the dynamic Eocene depositional systems along the western Indian Plate margin.

Key Words: Biostratigraphy, Foraminifera, Eocene, Ghazij Group, Western Indian Plate, Microfacies, Sequence Stratigraphy

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7968

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.