SEDIMENTOLOGICAL STUDY OF A SECTION OF THE "UPPER ZIGZAG"
FORMATION ALONG BUED RIVER, TUBA, BENGUET
ROLAND0 E. PENA AND MILAGROS V. REYES
ABSTRACT
Sedimentological study of the
sedimentary section below the Middle
Miocene Kennon Limestone along Bued
River consisted of detailed description
of selected local sections and
subsequent evaluation of primary
sedimentary structures and detailed
petrographic analysis of representative
rock samples.
Primary sedimentary structures shown
mostly by sandstone interbeds in the
dominantly conglomerate section are
parallel lamination and cross
stratification, normal and reverse
graded bedding. Slump structures and
sandwaves were also noted. Paleocurrent
directions derived from reoriented
foresets of cross-stratification
indicate a southwestern, source of the
sediments.
Textures and composition of the wackes
and conglomerates of the section studied
suggest that the sediments were
principally derived from a volcanic
terrain with considerable relief. These
sediments were probably deposited in a
nearby shallow marine basin by very
strong fluvial currents whose energy
diminished as it reached the basin area.
Intermittent changes in current velocity
during transport and at site of
deposition were most likely responsible
for the development of small and large
scale cross stratification.
Geological
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