GEOLOGY AND SEDIMENTATION OF TERRACE SEDIMENTS AT SEMBUNGAN AREA, MEGERI VILLAGE, KRADENAN DISTRICT, BLORA REGENCY, CENTRAL JAVA PROVINCE

GEOLOGY AND SEDIMENTATION OF TERRACE SEDIMENTS AT
SEMBUNGAN AREA, MEGERI VILLAGE, KRADENAN DISTRICT, BLORA
REGENCY, CENTRAL JAVA PROVINCE
Sigit Maryanto #
# Geological Survey Institute
Jl. Diponegoro No. 57 Bandung, 40122
Telp. 022-7203205 ext. 180, E-mail: sigit@grdc.esdm.go.id
ABSTRACT
The occurrence of the Early Quarternary Solo River terrace commonly associates with
vertebrate fossils, including hominid. The Solo River terrace cropped out at
Sembungan area is a good object for studying the sedimentology of terrace sediments
and paleo-topograpy of Solo River in associated with the discovery of the vertebrate
fossils. Detailed topography and geological mapping completed with detailed
stratigraphic section shows the dividing unit of the terrace sediments.
The terrace sediments of this area covered unconformably the Tertiary Kerek or
Kalibeng Formations. Based on the detailed geological mapping, the Solo River
terrace can be divided into three units : gravel unit in the lower part, gravely sand unit
in the middle part, and mud unit in the upper part. The lower part consists of gravel bar
or bedform deposit with sporadically intercalated by gravity flow sediment,
predominated by cobble and pebble beds. The middle part consists of point bar
deposit, predominated by gravely sand and sand beds. This terrace sedimentation was
ended by suspended mud deposits at river overbank, predominated by massive mud
beds with several carbonate nodules (calcretes) and plant remains. Both of angular -
subangular in various size and rounded small size of the vertebrate fossil fragments
founded in the lower and middle parts of this terrace.