Paleoenvironmental and Bio-Sequence Stratigraphic Analysis of the Cretaceous Pelagic Carbonates of Eastern Tethys, Sulaiman Range, Pakistan

Abstract

The Cretaceous pelagic carbonate succession, i.e., Goru Formation was studied in the Chutair Section, Sulaiman Range, representing part of the eastern Tethys for the paleoenvironment and bio-sequence stratigraphy. Eight planktonic foraminiferal biozones are identified which include: 1. Muricohedbergella planispira Interval Zone; 2. Ticinella primula Interval Zone; 3. Biticinella breggiensis Interval Zone; 4. Rotalipora appenninica Interval Zone; 5. Rotalipora cushmani Total Range Zone; 6. Whiteinella archeocretacea Partial Range Zone; 7. Helvetoglobotruncana helvetica Total Range Zone; and 8. Marginotruncana sigali Partial Range Zone representing Albian-Turonian age. The petrographic studies revealed five microfacies: 1. Radiolarians-rich wacke-packestone microfacies; 2. Radiolarians-rich wackestone microfacies; 3. Planktonic foraminiferal wacke-packestone microfacies; 4. Planktonic foraminiferal wackestone microfacies; and 5. Planktonic foraminiferal packestone microfacies; indicating deposition of the Goru Formation in outer-ramp to deep basinal settings. Based on the facies variations and planktonic foraminiferal biozones, the 2nd and 3rd order cycles are identified, which further include six transgressive and five regressive system tracts. The sea level curve of the Goru Formation showed fluctuation between outer-ramp and deep-basin, showing the overall transgression in the 2nd order cycle in the study area, which coincides with Global Sea Level Curve; however, the 3rd order cycle represents the local tectonic control during deposition of the strata.