GEOLOGI NEOGEN-KUARTER DI SUB CEKUNGAN MAJALENGKA, JAWA BARAT

Abstract

ABSTRAK: Pulau Jawa terbentuk oleh aktivitas konvergensi antar lempeng Eurasia dan India-Australia. Aktivitas tersebut menghasilkan berbagai fenomena geologi dalam jenis batuan Tersier maupun Kuarter, salah satunya di Desa Cipeundeuy, Kabupaten Majalengka, Jawa Barat. Penelitian ini bertujuan untuk menganalisis perkembangan sejarah geologi yang terjadi selama Neogen hingga Kuarter dengan melakukan observasi lapangan, analisis laboratorium, dan analisis studio. Satuan batuan yang tersingkap dari tua ke muda adalah Formasi Cinambo Anggota Batupasir, Formasi Cinambo Anggota Batuserpih, Formasi Halang Anggota Bawah, Formasi Halang Anggota Atas, Formasi Kaliwangu, Andesit Hornblende, Endapan Gunungapi Tua, dan Endapan Gunungapi Muda. Proses pengendapan dimulai pada Miosen Awal-Resen. Pada Miosen Awal-Miosen Tengah terendapkan Formasi Cinambo Anggota Batupasir dengan satuan batupasir melalui mekanisme high density turbidity current pada lingkungan pengendapan lower-middle fan. Formasi Cinambo Anggota Batuserpih terendapkan secara selaras diatasnya yang terdiri dari satuan batuserpih pada lingkungan pengendapan middle fan dengan mekanisme low density turbidity current. Pada Miosen Tengah terbentuk Formasi Halang Anggota Bawah melalui transportasi debris flow yang diselingi oleh aliran low turbidity current pada lingkungan upper fan dengan litologi satuan breksi. Formasi Halang Anggota Atas terendapkan secara selaras diatasnya dengan satuan batulempung pada Miosen Akhir oleh mekanisme low density turbidity current. Selanjutnya, Formasi Kaliwangu diendapkan di zona neritik pinggir dengan satuan konglomerat pada Pliosen. Aktivitas vulkanik mulai terjadi mengakibatkan terbentuknya intrusi Andesit Hornblende yang menerobos batuan tua. Adapun, Pliosen- Pleistosen terjadi aktivitas tektonik dengan rezime kompresional, sehingga membentuk struktur geologi berupa Sinklin Babakanjawa, Antiklin Kadu, Sinklin Cengal, Antiklin Cimanintin, Sinklin Cimanintin, Antiklin Gununglarang, Sinklin Cisampih, Antiklin Ciranggem, Sesar Kadu, Sesar Cengal, Sesar Cimanintin, Sesar Banjarsari, Sesar Cilutung I, Sesar Cilutung II, dan Sesar Cilutung III. Saat fase tersebut terendapkan material vulkanik dimulai Endapan Gunungapi Tua dan Endapan Gunungapi Muda. Resen terjadi pembentukan topografi seperti sekarang dan berlangsung proses denudasional serta erosi.

Kata Kunci: Cipeundeuy, Geologi, Kuarter, Neogen, Sub-Cekungan Majalengka

ABSTRACT: Java Island was formed by convergence of activities between the Eurasian and Indian-Australian plates. These activities produce various geological phenomena in Tertiary and Quaternary rock types, one of which is in Cipeundeuy Village, Majalengka District, West Java. This study aims to analyze the development of geological history that occurred during Neogene to Quaternary by conducting field observations, laboratory analysis, and studio analysis. Rock units that are exposed from old to young are the Cinambo Formation of Sandstone Members, Cinambo Formation of Shalestone Member, Lower Member Halang Formation, Upper Member Halang Formation, Kaliwangu Formation, Hornblende Andesite, Old Volcano Deposition, and Young Volcano Deposition. The deposition process begins at Early Miocene-Recent. In Early Miocene-Middle Miocene, the Cinambo Formation of Sandstone Member was deposited with sandstone units through mechanism of high density turbidity current in lower-middle fan depositional environment. The Cinambo Formation of Shalestone Member is deposited conformity on it consisting of shalestone unit in middle fan depositional environment with a low density turbidity current mechanism. In Middle Miocene, Lower Member Halang Formation is formed through debris flow transportation interspersed with low turbidity current flow in upper fan environment with breccia lithology. The Upper Member Halang Formation is deposited in conformity above it with claystone units in Late Miocene by mechanism of low density turbidity current. Subsequently, Kaliwangu Formation was deposited in a marginal zone with a conglomerate unit in Pliocene. Volcanic activity began to occur resulting in the formation of Hornblende Andesite intrusion that broke through old rocks. Meanwhile, Pliocene-Pleistocene occurred tectonic activity with compressional rezime, thus forming the geological structure in form of Babakanjawa Syncline, Kadu Anticline, Cengal Syncline, Cimanintin Anticline, Cimanintin Syncline, Gununglarang Anticline, Cisampih Syncline, Ciranggem Anticline, Kadu Fault, Cengal Fault, Cimanintin Fault, Banjarsari Fault, Cilutung I Fault, Cilutung II Fault, and Cilutung III Fault. When the phase is deposited volcanic material begins Old Volcano Deposits and Young Volcano Deposits. Resent occurs topographic formation as now and ongoing denudational processes and erosion.

Keywords : Cipeundeuy, Geology, Majalengka Sub-Basin, Neogene, Quarternary