A very few areas of the sedimentary basins of the world are characterized by marine facies of clastic and non-clastic origin, which are rich in planktonic and larger foraminiferal assemblages. Pakistan is one of the countries where the Tertiary marine deposits (Paleocene to Miocene) are represented by both clastic and nonclastic facies characterized by stratigraphically restricted planktonic and larger foraminiferal species, which provide the basis for the interregional biostratigraphic correlation.

The marine clastic deposits of Paleocene to Miocene age in the Lower Indus and Baluchistan basins of Pakistan are rich in the planktonic assemblages. On the basis of the stratigraphically restricted species, 22 planktonic foraminiferal zones were delineated to mark the stratigraphic boundary of the various European stages (Kureshy, 1977). The non-clastic marine deposits of Paleocene to early Miocene age in the Lower Indus and Upper Indus basins of Pakistan, which are interbedded with clastic deposits, are rich in larger foraminifera. On the basis of the stratigraphically restricted species, ten biostratigraphic zones of the larger foraminifera are designated (Kureshy, 1978).

These assemblages are cosmopolitan in occurrence of identical geological ages. The planktonic foraminiferal zones are more widespread and have close resemblance to the Caribbean region, as compared to larger foraminiferal zones. The larger foraminifera of Pakistan have no resemblance to the Caribbean region; however, they closely resemble Middle East and Indo-Pacific regions. The

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planktonic and larger foraminiferal zones are correlated, and datum planes are designated. These zones are correlated to Blow (1969) and van der Vlerk (1927) Letter Stage Classification for interregional correlation.

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