| dc.description.abstract | Geographic Indonesia is located on a volcanic ring path, from the Tertiary era to the Resen
volcanic arc stretching from Sumatra, Java to Banda. The Kulon Progo Mountains are part of the
Oligocene-Miocene volcanic arc called old andesite. The research area is located in the area of
Hargowilis and its surroundings, Kokap District, Kulon Progo Regency, Special Region of
Yogyakarta. Research in the mountainous area of Kulon Progo was carried out because it is a
complex of ancient volcanoes that have undergone intense morphological changes, rock deformation
processes to form geological structures within a certain geological time. The research method used
in this study includes the preliminary stage, the stage of observation and data collection, the stage
of data collection and analysis consisting of structural analysis, petrographic analysis and
micropaleontology analysis. The last stage is the preparation of a report based on the results of
research and field data analysis.
Geomorphology the research area consists of four geomorphic units, namely: Dam unit,
volcanic upper slope hill unit, volcanic middle slope unit, and denudational hill unit with radial,
rectangular and subdendritic flow patterns as well as mature to old area stadia. The stratigraphy in
the study area is composed of four units sorted by old and young consisting of: the Kebo Butak
andesite lava unit, the Kebo Butak andesite breccia unit, the Jonggrangan limestone unit, and the
Sentolo calcarenite unit. The geological structure that develops in the study area is faults and joints
with dominant directions northwest-southeast and north-south. The faults found in the study area
include: Crangah normal fault, Mangun Plawangan left slip fault, Hargotirto left slip fault, Kalibuko
left slip fault, Mount Reto left slip fault, Nganti left slip fault, Sermo Lor right slip fault, Hargorejo
and Gawir normal faults volcano. Resources in the research area are lava mining and andesite
breccia Kebo Butak, plantation land, agricultural land and water resources. Meanwhile, geological
disasters that occur in the research area are in the form of rock mass movements.
The geological history in the study area begins with the formation of the Kebo Butak
Formation ranging from the Late Oligocene to Early Miocene. During the Middle Miocene-Pliocene,
carbonate rocks began to develop in shallow-sloping seas. The ongoing subduction activity of the
Indian Ocean under the Sunda Trench has caused the process of uplift of the Southern Mountains to
date, in the study area marked by the death of carbonate sediment deposition and a change to the
terrestrial environment. The process of structure formation is interpreted as having a north-south
trend of compression, as well as erosion and weathering processes resulting in changes in the
topography of Mount Ijo until it changes to what it is now. | en_US |
