TEKTONOSTRATIGRAFI CEKUNGAN OMBILIN SUMATERA BARAT

Abstrak

Ombilin Basin is represent basin intramontane which limited by volcano-plutonic of Bukit Barisan
and zona of Sumatera Fault system which representing a active strike-slip fault zone in west and
metasedimen rock in. Form of fisiography Ombilin Basin show a hilly at part of edge of east-west until
to north with precipitous morphology and level-off continent. Ombilin Basin basement is divided two
part, that is structured basement by Mergui terrain and Woyla terrain. Eldest Basement of Ombilin Basin
is Formation of Limestone crystallin of Silungkang (age Perm) which laid bare at Tanah Hitam which
represent the part of Mergui terrains continent.
Tectonism of Ombilin Basin is started at Paleogen related to peripatetic Southeast Asia tectonism
which moving of India Block to northern. Early Paleogen, Ombilin Basin is formed with early motion of
transtensional effect of strike-slip fault motion of duplex regional, that is graben part of northeast
Ombilin Basin. Motion of strike-slip fault are Sitangkai fault and Silungkang fault where this faults
motion result attraction style in the form of normal fault by terrace to left north-south. This fault pattern
control forming of first basin cause to be formed its faults which instructing northwest-southeast, northsouth,
and northeast-soutwest of west-east. Tectonostratigraphy Ombilin Basin is represent full graben
with set of deposits syn-rift tectonostratigraphy and of post-rift deposits continue at mechanism of
transgressive in the early Neogen.