GEO 460: Sed/Strat
Sedimentary Descriptions (Siliclastic) Lab
Sample 12 – This very poorly sorted, matrix-supported conglomerate consists of
multi-colored cobble-sized framework clasts, ranging between 20-70 mm in size;
displaying subrounded to well rounded shape clasts. The framework and matrix are
both polymict compositions and cemented together with quartz. The moderate
yellow-brown matrix is comprised of medium sand to granule size clasts; with very
angular to subangular grains.
Sample 4 – A poorly sorted, clast-supported conglomerate with no matrix, a light
olive gray hue, and an oligomict composition. Dominated by subrounded quartz and
plagioclase grains that range from very coarse sand to pebble size, this
conglomerate is cemented by quartz.
Sample 9 – This light olive gray, moderately sorted, matrix-supported conglomerate
consists of pebble to cobble sized framework clasts that are subrounded to rounded.
The matrix is comprised of angular to subrounded clasts of a polymict composition
that range from coarse sand to granule sized grains and bonded to the framework
with silica cement.
Sample 7 – This poorly sorted, matrix-supported conglomerate is composed of
angular to subrounded framework clasts that are granule to pebble sized and
polymict in composition. Carbonate cement that is likely calcite has replaced the
matrix. The pale yellowish brown sample is dominated by a wealth of fossils, which
include: bivalves, algae, and gastropods.
Sample 8 –A green-gray, moderately sorted, matrix-supported conglomerate with
subrounded framework clasts ranging from medium sand to granule size and
displays an oligomict composition. The matrix clasts range from fine sand to
medium sand in size and are weakly cemented with silica to the framework clasts.
Sedimentary Characteristics (and how they are altered by diagenesis):
Color – Diagenesis affects color in the