Onderzoek in de Siwaliks van Noord-Pakistan

An American/Dutch/Pakistan team is carying out a paleontological fieldwork in the Siwaliks of Northern Pakistan, in an area called the Mangla-Samwal Anticline. The Siwalik Hills are situated along the southern margin of the Himalaya. They consist of the erosional products of the Himalaya, which are laid down as alluvial fan- and riverdeposits. These sediments, with an age of Middle Miocene to Pleistocene, are rich in fossil mammals. During the last 150 years these fossils have been studied and many species have been described. But the existing biostratigraphical classification of the Siwaliks is not satisfactory. With modern methods and views, a more detailed biostratigraphy can be obtained. For that purpose several disciplines within the geology are used, namely sedimentology, paleomagnetism and paleontology/stratigraphy. First the geology of the area is investigated. By taking several lithological sections throughout the area, the rocks are described and divided in lithostratigraphic units. By combining these sections, a lithological framework is created. Based on this framework, one can conclude, that the oldest sediments were laid down by large scale braided rivers, whilst the younger sediments were deposited by small scale rivers with an intermittent discharge. This change in riversystems caused the disappearance of Hexaprotodon sivalensis from this area. A paleomagnetic section taken by the americans in this area, could be correlated with our own lithological sections. In this way the absolute ages of the layers are roughly known and therefore also of the faunas from these layers. These faunas are the basis of our new biostratigraphy of this area. The new biostratigraphy of Barry et al. (1982) for the Potwar Plateau is used as a standard. Preliminary results are: the lower boundary of Barry’s Elephas planifrons Interval-Zone, which was set by Barry et al. at 2.9 my B.P. is tentatively dated around 3.4 my; the Elephas planifrons Interval-Zone can probably be subdivided on the basis of the entrance of Elephas hysudricus, cervids and probably Equus at around 2.7 my B.P., in the Elephas planifrons Interval-Zone and the Elephas hysudricus Interval-Zone.