Sedimentology and Stratigraphic Evolution of the Early Eocene Nammal Formation, Salt Range, Pakistan

The Early Eocene succession of the Salt Range belongs to Tethys regime and comprises of the Nammal Formation, the Sakesar Limestone and the Chor Gali Formation. The Nammal Formation (Ypresian age) 30m to 32m thick is well exposed throughout the Salt Range. Detailed sedimentological analysis was carried out, based on data from six stratigraphically important sections in the Salt Range. Lithologically, the formation is predominantly composed of interbedded nodular limestone, marl and shale. The microfacies are identified as the wackestone, wackestone to packstone, packstone, dolomitic limestone and grainstone in a fine-grained matrix with abundant biolclasts of larger benthic foraminifera. Stable carbon and oxygen isotopic signatures of the Nammal Formation indicate the shallow marine environment. During Eocene a carbonate sequence developed in the Salt Range, lower boundary of which is marked as SB II at the base of the Nammal Formation overlying the Palaeocene Patala Formation. The Nammal Formation presents the retrogradational facies suggesting the Transgressive System Tracts (TST). The Sakesar Limestone shows agradational to progradational pattern of facies, which developed in Highstand System Tracts (HST). The Chor Gali Formation possesses shallowing-upward trend by forming progradational shift of facies, and represents the Falling Stage System Tracts (FSST). The Early Eocene carbonate sequence is terminated by a regional sub-aerial unconformity SBI due to Himalayas Orogeny and termination of the Early Eocene marine carbonate sequence that is capped by Miocene non-marine the Kamlial Formation. Overall, the Nammal Formation presents shallow water neritic carbonate deposits containing larger benthic foraminifers.

کلیدواژه ها:

Early Eocene ، Nammal Formation ، Salt Range ، Sedimentology ، Shallow water