ASPEK PROSES DIAGENESIS TERHADAP SIFAT FISIK BATUPASIR FORMASI KEREK, DAERAH KALIPUTIH DAN SEKITARNYA, KECAMATAN SINGOROJO, KABUPATEN KENDAL, JAWA TENGAH

The sedimentary rock is formed and associated with the diagenesis processes, as all the physical, chemical, and<br />biological changes in the characteristics of a sediment accumulation from the time the grains are deposited until<br />they are metamorphosed. This process is profoundly influence the characteristic of sedimentary rock, including the<br />texture, internal structure, mineral composition, cementation type, and pore space. Hence, it is important to know<br />or learn the stage of sandstone diagenesis, especially in the Kerek Formation to mark the correlation between<br />diagenesis and physical properties of sandstone.<br />The purpose of this research is to identify the stage of diagenetic processes, diagenetic environment, the type of<br />cementation, and the relationship between diagenetic stage and physical properties of sandstone. The methods used<br />in this research are survey method and data analysis method. The survey method includes the making of crosssectional<br />measured stratigraphy and data analysis method includes petrographic and scanning electron microscopy<br />(SEM).<br />The sedimentary structures found in the carbonate sandstones are burrows, convolute ripple lamination, graded<br />bedding, parallel lamination, cross lamination, current ripple lamination; which are features of turbidity deposition<br />(Bouma sequence). Based on the petrography analysis results for sample P 01 and P 02 showed compaction,<br />cementation, dissolution, and bioturbation, with a porosity value of 1 %. Sample P 03 showed compaction,<br />cementation, dissolution, and bioturbation, with a porosity value of 7 %. Sample P 04 showed compaction,<br />cementation, and dissolution, with a porosity value of 1 %. Sample P 06 showed compaction, cementation,<br />dissolution and replacement, with a porosity value of 5 %. Sample P 07 showed compaction, and cementation, with<br />a porosity value of 30 %. The Lithology type in the research area was Calcarenite with dominant shell fragment,<br />the lithology names are Packed biomicrite (Folks, 1959; in Nichols, 2009), and Packstone (Dunham, 1962; in<br />Nichols, 2009). Carbonate sandstones predominantly feldspar and quartz minerals and the lihtology names are<br />Carbonate quartz wackes (Pettijhon, 1975; in Nichols, 2009), and Carbonate feldspathic arenite (Pettijhon, 1975;<br />in Nichols, 2009). There are three minerals type of cement showed in carbonate sandstones which are calcite,<br />chlorite and pyrite cements.<br />The results of this research indicate that the diagenesis stages of carbonate sandstones showed cementation,<br />dissolution, replacement, bioturbation, and compaction processes, and the more stages of diagenesis that occurs in<br />carbonate sandstones will result in reduced porosity and progressively up at for formation stratigraphy excelsior<br />sediment rock assess its porosity is equal to 1%, 5%, 7% and 15% respectively. The type of cement minerals in the<br />carbonate sandstone influence porosity, especially in carbonate sandstone which there are chlorite cement that have<br />small porosity value of 1%, 5% and 7%. The environment of diagenesis in carbonate sandstones that is phreatic and<br />burial experienced of eogenesis process, mesogenesis process and telogenesis process