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

Abstract

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