, and 46.5% to
74.0% (64.1%) in the Bhuban Formation (Surma Group). Quartz formed
58.8% of the single Bokabil sample counted. Qm (93%) is dominant over
Qp (Fig. 2). Well-rounded grains are rare, and overgrowths within grains
are not visible. Lithic fragments are next most abundant (3.9%–17.0%;
av. 11.1%). Sedimentary (av. Ls/L=0.53) and metamorphic lithics (av.
Lm/L=0.46) are dominant, and volcanic rock fragments are very rare
(av. Lv/L=0.004). The sedimentary lithics consist of microcrystalline
chert, shale, and siltstone, whereas metamorphic lithics are quartz–mica
schist, mica–schist, phyllite, and metaquartzite.
Small amounts of detrital feldspar are present. Contents are lower
in the Renji Formation (av. 5.6%) than in the Bhuban (8.3%) or Bokabil
Formations (12.0%). Grains are generally unaltered, but partially
altered feldspars are also present. K-feldspar is slightly more
abundant than plagioclase (av. K/F =0.55), and is mostly orthoclase
and microcline. Mica is common, ranging from 3.7% to 13.7% (av. 7.8%)
and is most abundant infine-grained sandstones. Biotite is extensively altered to chlorite, and is dominant over muscovite. Authigenic
minerals are mainly carbonate, with subordinate chlorite and
kaolinite. Matrix contents are usually low (b5%)