Preliminary Geology And Petrography Of Swat Kohistan

cornruing conEuent with one mother, and have marked resembleace with Missisipian-Pensyl
vanian corals (M.A. Khan, personal commuoication). The thin
sections a-lso have columnals of crinoids and a few fragments of (1) fusulinids.
The limestone, thus, appears to ba Carboniferous. The underlying thick qual?tzites
and other metasedimentnry rocks may be of this age or even older (Siluro-
Devonian). The group thus belongs to the many Middle to Late Paleeozoic
rocks of the northwestern Pakistan (see Jan and Kempe, 1970).
The Kohistan Basic Complex.
The complex inclndes diorites, norites, amphibolites and the associated
racks, previously called the Upper Swat Hornblendic Group by Martin et of*
(1962). We propose the new name because it is mor meaningful than the old,
arnbiguous one. Besides, such rocks are abundant in Kohistan of Dir and Hazara,
and in southwestern part of Gilgit Agency. The rocks probably ex1 end as far to
the east as Nangs Parbat, and to the west in Afghanistan (Jan, 1970). In the
investigated area, the complex is dominated by norites and diorites, wit.h minor
amphibolites, granites, and layers of pyroxenites and anorthosites. Davics
(1964), who considered the rocks plutonic, has also reported granodiorites and
syenites.
Geologists of Peshawar University, who worked in various parts of Upper
Swat, Indus Valley, and Timurgara (Dir), have proposed the following general
subdivision of the complex : amphibolites, norites/diorites, perido tites, and
granitic rocks. Jan and Kempe (in preparation) have recently shown that the
granites and some peridoties are later in age and are not related genetically to
the basic seriee. They have also suggested that the three major rock types
(amphib olites, norites, arid diorites) repraan t o metamorphosed differentiated
igneous series. A characteristic field feature of the norites is the flesh-pink
plagioclase and dark, greenish-pink hypersthene. Where the feldspar is not pink,
tila rocks look greyish to dark gabbroic. They turn light grey on weathering
but, in the upper reaches of Mankial valley, they are dark brown due to arid
weathering.
Most of the rooks are medium-grained and gneissose. A few are fine-mained
and some are characteristically coarse, such as those of the Miandam area.
With rare exceptions, foliation is well-developed and, in a few, lens-shaped feldspar
may impart the look of angen-gneisses. In rare oases, large crystals of pyroxene
may be studded like buttons in planes often parallel to foliation. Some norites
exhibit textural and/or GO mpositionol layering (Jan and Kempe, in preparation)