The Magnetostratigraphy and the Age of So’a Basin Fossil-Bearing Sequence, Flores, Indonesia

DOI: 10.17014/ijog.5.3.221-234Three fossil-bearing intervals have been recognized in the Pleistocene So’a Basin, with the upper one holding important evidence of hominin fossils. The sequence also contains numerous in situ stone artifacts and fossils of other vertebrate taxa. Therefore, multiple dating techniques are crucial to secure the age of the fossil and artifact-bearing layers, especially the one with the hominin remains. This paper deals with the palaeomagnetic dating of the So’a Basin sequence to assist other dating methods that have been applied, and to refine the chronostratigraphy of the area. Palaeomagnetic sampling was conducted in four sections along a west to east transect. Four magnetozones can be recognized, consisting of two reverse and two normal polarity zones. By using the available radiometric ages as a guide and comparing the So’a Basin magnetostratigraphy with the Standard Geomagnetic Polarity Time Scale (GPTS), it became clear that both reverse magnetozones are part of the Matuyama Chron, while the normal magnetozones are the Jaramillo subchron and the Brunhes Chron. These palaeomagnetic dating results support the available radiometric dates and refine the age of the fossil-bearing deposits of the So’a Basin.</p

The geodiversity site of Sentono Gentong in Pacitan, Indonesia: Geological characteristics and quantitative assessment

This paper aims to identify the geological properties of Sentono Gentong and provide a quantitative assessment of its geodiversity site in Pacitan Regency, Indonesia.This area is an integral part of the vast Gunung Sewu UNESCO Global Geopark. Rock samples and site conditions are compiled on field study. The study area consists mainly of Neogene limestone and older igneous rock. Microscopic analysis has revealed that the limestone is composed of bioclastic wackestone, boundstone, and fossiliferous wackestone. The igneous rock in the area is a grey-black hornblende andesite. Bangunsari fault, which cuts through the study area, disturbs the coastal terraces to its south. The results of the quantitative assessment show that the site's potential educational use, potential touristic use, and degradation risk scores are 92.5, 80, and 56.25, respectively. The assessment scores describe the site as having potential for education and tourism uses, with a medium risk of degradation. Quite prominent cultural elements, which form the local community's identity, are included as a complement to the identification of the site. In order to preserve and maintain the sustainability of this potential geodiversity site, a high commitment related to geoconservation is required