PALEONTOLOGICAL STUDY OF STEGODON FROM SANGIRAN AND THECORRELATION WITH PELEOECOLOGY AND BIOSTRATIGRAPHY

• Main Author: Rizki Puspaningrum, Mika
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/77096
• Institution: Institut Teknologi Bandung

A detailed paleontological study of Stegodon fossil from Sangiran has been conducted to formulate the paleoecology and biostratigraphy based on Stegodon fossil of Sangiran. Sangiran is a dome form, trending in and ENE-SWS where the Quaternary sediments are well exposed. The Sangiran is objected for the study because Sangiran is rich with the Stegodon fossils, but very rare researcher attempted to study the paleontology of Stegodon fossils. The paleontological study of the Stegodon fossils have been done from the collection of Bapang (=Kabuh) and Sangiran (=Pucangan) Formations, which belong to the Balai Pelestarian Situs Manusia Purba (BPSMP) Sangiran, Centre of Geological Survey (CGS), and Paleontology Laboratory of Geological Engineering Study Program, ITB. Identification and biometric measurements of Stegodon have been performed, while the paleoecology was reconstructed based on palynological data. All specimens that has been studied were identified as belongs to Stegodon elephantoides (Clift, 1828) and Stegodon trigonocephalus (Martin, 1884). The Stegodon elephantoides has robust feature, very thick horizontal ramus, narrow alveoli, elongated symphysis, and less number of ridges. The S. trigonocephalus was divided into two groups based on cluster and principal component analysis. Both of the groups are originated from two different formations e.g. Bapang and Sangiran Formations. The S. trigonocephalus from Sangiran formation has robust feature with relatively thicker in horizontal ramus, narrower of olveoli and longer of intraalveolar crest; less number of ridges, shows lower value of Hypsodonty Index in M3 and higher value of HI in M2 , while S. trigonocephalus from Bapang formation has relatively thinner in horizontal ramus, wider of alveoli and shorter of intraalveolar crest; and has more number of ridges, shows higher value of Hypsodonty Index in M3 and lower value of HI in M2 . Therefore, the Stegodon originated from Sangiran Formation then namely as S. trigonocephalus from Sangiran while the fossils from Bapang Formation were namely as S. trigonocephalus from Bapang. The lithology of Sangiran Formation contains of lahar deposits of Lower Lahar Unit at the lowerpart and dominantly black clay and silty clay, wih intercalation of thin layer of silt and fine sandstones. The Bapang Formation consists of very coarse and conglomeratic sandstone intercalated with tuffs and tuffaceous clays of the river deposits. The lithostratigraphic analysis indicates the existence of environment changes from low energy conditions during the deposition of the Sangiran Formation to high-energy with sandy volcaniclastic sediments from adjacent volcanic highlands during the deposition of the Bapang Formation. The environmental changes were also shown in the vegetation composition, indicates the change of the climate from dominantly wetter climate lowland forest and swampy grassland during the deposition of Sangiran Formation to dryer climate grassland during the deposition of Bapang Formation. Therefore, two biostratigraphic units of the Stegodon are proposed. The older unit characterized by S. elephantoides and S. trigonocephalus from Sangiran that belongs to Ci Saat to Trinil HK fauna (Early Pleistocene), and the younger unit characterized by S. trigonocephalus from Bapang that belongs to Kedung Brubus fauna (Middle Pleistocene).