THE STUDY OF TRACE FOSSILS IN THE HALANG FORMATION OF CIPARI AREA AND SURROUNDINGS, CILACAP DISTRICT, CENTRAL JAVA

• Main Author: Chandra Jaya Pratama, Andhika
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/37315
• Institution: Institut Teknologi Bandung

Often the occurrence of trace fossils in a single rock layer is interpreted as a mixture of various kinds of trace fossils. This point of view causes controversy in the interpretation of geological data. An occupational process carried out by organisms on a substrate during a deposition leaves fossil traces as evidence of the organisms' interaction. This process is strongly influenced by the range of colonization windows. The range of colonization windows is the time span available to animals in exploiting the substrate from the time when the larvae settle until further relocation occurs. Therefore, the geological interpretation using fossil traces should pay attention to the occurrence of fossil traces based on the range of colonization windows and the occupational processes. The object of this study is the Halang Formation that is revealed in the Cipari area and its surroundings. The rock formation is found as the sedimentary rocks which is resulting from a deep marine depositional system with variations of the trace fossils occurrence. The aims of this research are to obtain a detailed boundary of the sedimentology process and the stratigraphic phenomena in the gravity flow deposits where occurred in the Halang Formation by using the trace fossils. The collected data from the measured stratigraphic section and the occurrence of trace fossils in the Kali Soka traverse are classified according to the model of morphological complexity. The model resulted is composed of four levels of morphological complexity of trace fossils in the order of morphological complexity from simple to complex: (I) Planolites, (II) Arenicolites - Palaeophycus, (III) Rhizocorallium, and (IV) Thalassinoides - Zoophycos - Chondrites. The model is compared with the genetic facies gravity flow model in the form of Turbidity Current and Debris Flow. In addition, in this study, the length of the colonization window is interpreted as a result of the occupational process that lasted for a short time until a long time. The final result is a colonization window for the organism during the sediment deposition process and a detailed boundary of the gravity flow deposits.