STRATIGRAPHY AND PALAEOICHNOLOGY OF THE “BLACK SHALE” FACIES (CHERT UNIT) OF THE SEMANGGOL FORMATION AT BUKIT MERAH (N PERAK)

The wide exposed area of Bukit Putus, one of Semanggol abandoned quarry in
Bukit Merah has allowed to start a detailed study of the chert unit of the Semanggol
Formation. Chert unit in particular were deposited in a basin of deep ocean
environment under the influence of different regimes of transportation, Basir Jasin &
Zaiton Harun (2007). Till date, no integrated stratigraphy and palaeoichnological has
yet been presented particularly in this area although the siliciclastic succession of Bukit
Merah has been described by Hutchison & Tan (2009), as deep-water deposits across
the Semanggol Basin. The analysis conducted aim to reconstruct its paleoenvironment
evolution. Fieldwork and few data collection has been done in order to produce a
geological map of the study area as well as the stratigraphic logging. The samples
collected have been studied and examined by means of thin sections, Total Organic
Content (TOC), Scanning Electron Microscope (SEM) – EDX, and photography and
image enhancement. Sedimentary facies and facies association description will be
done on the outcrop of the ‘black shale facies’ of the chert unit. As a result, trace and
body fossil data are in agreement with the sedimentological ones; basin evolved from
– mid and distal continental shelf situations to shallower sublittoral conditions. The
general sedimentary evolution is compatible with the dynamics of a deltaic apparatus
prograding seaward (prodelta evolving into lower delta front). The "black shale" facies
are reflecting true anoxic conditions during deposition only in a few cases (i.e., where
rocks lack completely benthic body and trace fossils). In most of the black shale
intervals anoxia was reached after burial, as they show a moderate to high
palaeontological contents of benthic origin. Bivalves of Claraia (suspected) sp, a
Permo-Triassic bivalve which belongs to Aviculopectinidae family and also
brachiopod interpreted as from Lingulida family has also been discovered at the
outcrop of Bukit Putus quarry. In short, the result from integration of stratigraphy and
paleoichnology has supported the hypothesis of this study.