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A biostratigraphic zonation of the middle and upper siwaliks of the potwar plateau of Northern Pakistan

1982; Elsevier BV; Volume: 37; Issue: 1 Linguagem: Inglês

10.1016/0031-0182(82)90059-1

1872-616X

John C. Barry, Everett H. Lindsay, Louis L. Jacobs,

Morphological variations and asymmetry

Two biostratigraphic reference sections are designated for the middle and upper Siwalik formations of northern Pakistan. The stratigraphic ranges of 41 mammalian taxa are established in the reference sections and the two sections are correlated to each other and to the standard Magnetic Polarity Time Scale by the magnetic-polarity stratigraphy. The resulting stratigraphic and magnetostratigraphic framework is used to define four contiguous biostratigraphic interval-zones. The proposed interval-zones are bounded by five important faunal events which are identified in the reference sections. The four proposed interval-zones and the approximate ages in the reference sections of their lower and upper boundaries are: (1) the "Hipparion s.l." Interval-Zone 7.4–9.5 m.y. B.P.; (2) the Selenoportax lydekkeri Interval-Zone 5.3–7.4 m.y. B.P.; (3) the Hexaprotodon sivalensis Interval-Zone 5.3-2.9 m.y. B.P.; and (4) the Elephas planifrons Interval-Zone 2.9-1.5 m.y. B.P. The paleomagnetic and biostratigraphic evidence indicates that the Tatrot Beds, from which Pilgrim developed his "Tatrot Faunal Zone", are between 2.5 and 3.4 m.y. B.P., with a preferred maximum age of 2.9 m.y. B.P. The biostratigraphic evidence indicates the Sethi Nagri locality (Y311)—the primary source of Pilgrim's "Nagri Faunal Zone"— is in the "Hipparion s.l." Interval-Zone. The paleomagnetic evidence suggests an approximate age of 9 m.y. B.P. A major faunal event at 9.5 m.y. B.P. introduced equids, suids, and large giraffes from Eurasia into the Indain subcontinent. A second, more diffuse faunal event between 5.3 and 2.9 m.y. B.P. introduced several African taxa as well as Equus and cervids from Eurasia.