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Description
The objective of this thesis is to examine the relationship connecting regional plate tectonics, structural geology, and sedimentology to establish the basin geometry and arc development of the Central and East Java region. This thesis presents tectonostratigraphic and paleontologic data obtained in the field, as well as conclusions derived from collaborative research between San Diego State University (SDSU) and students and faculty from the University of Gadjah Mada (UGM) under the sponsorship of ChevronTexaco (formerly CalTex in Indonesia) as a collaborative university project. The area of concentration is located east of the city of Salatiga and just to the northeast of the large city of Yogyakarta in Java. The emphasis was on the geologically complex Kendeng Zone where evidence of intensive deformation and fracturing is clearly observable around the Kedung Ombo Reservoir, along the Alas Kobong Railroad Cut, and within the Jerukan Wash. The project spanned a period of thirty days of fieldwork and several months of preparation time at SDSU prior to the trip to East Java. This study focuses on the use of tectonostratigraphy and paleontology to decipher the major tectonic events in this region from mid-Miocene time onward. The objectives, as outlined in the project overview, include a brief explanation of the Philippine-Pacific and Indo-Australian plate tectonics as they relate to the study area. The stratigraphic history of the Kendeng Zone, including the sedimentology and fold systems, were examined in order to establish a relationship between localized findings and the movement of plates on a regional scale. Past geologic research was combined with field data to provide insight into the tectonostratigraphic development during the Miocene. A secondary objective of the thesis was to utilize Global Positioning Systems (GPS), Geographic Information Systems (GIS), and remote sensing tools in the field to do real-time field mapping utilizing new computer and visualization technologies applicable to field geology in remote environments. The methodology is explained with detailed descriptions of the problems encountered during fieldwork. Java is an excellent area to test the use of GPS, GIS, and remote sensing because of the abundant vegetation and lack of clear locations needed in traditional geologic mapping. This region provided a testbed to explore the potential for real-time data transfer to benefit field research. The software applications including ArcView and GeoMapper and the hardware devices comprised mainly of a Fujitsu tablet computer, an IBM ThinkPad laptop, and a Motorola satellite phone were implemented in the field. The complications of transmitting data under less than ideal conditions are presented as part of this project. Although successful transmission of data from the field was accomplished in real-time, connection speeds never exceeded 0.2Kb/s, which was unacceptable for the transfer of large packets of data. Final conclusions provide stratigraphic insight into the tectonic development of the Indonesian arc region from an in-depth study of a relatively small area. These data can be used to help clarify the regional tectonic models that have been proposed for this region and the extremely complicated tectonostratigraphic development of Southeast Asia.
