BATHYMETRIC STUDY OF TIYON FORMATION BASED ON FORAMINIFERAL ASSEMBLAGE AROUND LAKI RANGE, LOWER INDUS BASIN, SINDH

Abstract

The Bathymetric study of the Tiyon formation, which conformably lies in between Laki and Kirthar Formation around Laki Range is carried out to construct the paleoenvironment interpretation, worldwide correlation and assigned the Standard Chronostratigraphic age. The bathymetric study of the Tiyon formation indicates three zones with their characteristic particular species are: -  Brackish water zone (shelf neritic) Elphidium, Nonion  Shallow water zone (outer neritic) Quinqueloculina, Robulus  Deep water zone (inner neritic) Gyroidina, Rosalina Faunal assemblage and planktonic / benthic ratio suggests that the deposition of the Tiyon formation have took place under marine condition, indicating a near-shore deposition under a very shallow to bathyl zone with clear warm water condition in tropical region. The abundant presence of planktonic foraminifera in the lower part of the Tiyon formation indicates the connection of depositional basin with the open sea, while this condition does not exist in the upper part of the formation. The Tiyon formation contains a variety of stratigraphically important benthic and planktonic species which includes 140 species, 35 planktonic and 120 benthonic forams, belonging to 31 genera & 15 families. The recognized planktonic zonation includes Globigerinatheka semiinvolta Zone, Truncorotaloides rohri Zone, Orbulinoid beckmanni Zone, Globigerina frontosa Zone, Hantkenina aragonensis Zone and Acarinina pentacamerata Zone. These zones verify the Late Ypresian to Early Bartonian age to the Tiyon formation rather than Late Ypresian to Lutetian. The benthic assemblage shows distinct affinities with the Lutetian fauna of Sor Range, (Baluchistan), Raki Nala and Nammal Gorge (Salt Range), Hampshire Basin (England), Paris Basin (France), Gulf Coastal Region (USA), Belgium and Kutch (India). The Tiyon formation is correlated with Pir Koh Limestone (Lower part of Drazinda Shale), Basal Shale unit of Kirthar Formation (Baluchistan), upper part of the Ghazij Shale, Chorgali, Sakesar, Kuldana and basal part of the Kohat Formation. Total number of species and specimen have been plotted graphically to indicate the dominancy of different faunal zone over on another. Temperature is also a determining factor in the study of bathymetric study. Some characteristic species which are exclusively tropical and live in warm temperature also have been discussed in this thesis.