Pola Perubahan Iklimpurba pada Umur Pliosen dengan Proksi Foraminifera: Studi Kasus Formasi Sentolo, Yogyakarta
DOI:
https://doi.org/10.33332/jgsm.geologi.v23i3.703Abstract
Studi distribusi foraminifera untuk menentukan pola perubahan iklimpurba pada umur Pliosen dilakukan pada Formasi Sentolo. Daerah survei terletak di sebelah barat kota Yogyakarta. Secara regional daerah ini merupakan bagian dari Pegunungan Kulon Progo. Pengukuran stratigrafi dilakukan dengan metode Tongkat Jacob dengan total ketebalan lapisan 38,9 meter. Bagian bawah daerah survei tersusun oleh perlapisan batupasir karbonatan-napal. Bagian tengah berkembang fasies perlapisan batugamping-batupasir karbonatan dan di ketebalan 25 meter berkembang perlapisan batugamping packstone-rudstone. Bagian atas pengukuran stratigrafi kembali berkembang fasies batupasir karbonatan dengan sisipan napal. Analisis lingkungan pengendapan dengan metode P/B ratio mendapatkan dinamika lingkungan pengendapan dari batial bawah hingga neritik luar. Analisis biozonasi mendapatkan zona Globigerina nepenthes dengan kisaran umur N19 (Pliosen Awal) dan zona Globorotalia pseudomiocenica dengan umur N20 (Pliosen Akhir). Dijumpai dua pola perubahan iklim di daerah survei, yaitu pola mendingin pada Pliosen Awal dan pola menghangat pada Pliosen Akhir. Hal tersebut memiliki pola yang sejalan dengan kurva eustasi global yang menunjukkan adanya penurunan muka air laut global pada Pliosen Awal dan kenaikan muka air laut secara gradual memasuki Pliosen Tengah.
Katakunci: Foraminifera, Formasi Sentolo, iklim purba, Pliosen
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