Analysis of Geological Structure based on 3D Virtual Outcrop Model and Physical Properties of Rocks in Wringinanom District, Gresik Regency

The Covid-19 pandemic has caused geological mapping activities to be hampered. This study aims to create a 3D virtual rock outcrop model which is compiled from 2D rock outcrop images with Measured Stratigraphy (MS), strike & dip and the value of rock physical parameters to analyze geological structures in Wringinanom District, Gresik Regency. Analysis of geological structures will be contained in the form of folding reconstructions with rock physical parameter as a validation and descriptions of fault orientation. This research modeled 21 rock outcrops and will be tested 6 core sedimentary rock samples. Physical rock parameter tests in the form of density tests through the comparison of mass weighing results with dimensional measurements by calipers and P-wave velocity tests using the Ultrasonic Pulse Velocity (UPV) method. Petrological descriptions of core rock samples are based on direct observations. The results of 3D virtual rock outcrop integrated with measurements in the field can be used in analyzing geological structures. The study area consists of anticlines with the direction of layering the south (southwest) and north (northeast) wings and 50-degree reverse faults with southeast dipping orientation (N153°E). The folding reconstruction consists of sandstone (top), sandstone-clay interlude, and claystone (top) in the Pucangan Formation and sandstone (bottom) and claystone (bottom) in the Lidah Formation where the presence of fossil layers of bivalve mollusks is a firm correlation. The physical parameters of rocks cannot validate the reconstruction of folds due to the influence of differences in physical values of the sample supported by petrological descriptions.