UMUR FORMASI CANTAYAN DI SUNGAI CIBEET CIANJUR

Abstrak

ABSTRAK
Formasi Cantayan yang tersingkap di Sungai Cibeet disusun oleh batupasir dalam berbagai ukuran butir dan ketebalan, breksi dan batulempung. Di bagian bawah disusun oleh perselingan batupasir kasar, dengan ketebalan bervariasi antara 30 sampai dengan 60 cm, dan dapat bisa menumpuk hingga ketebalan lebih dari 5 meter. Sisipan batulempung sesekali muncul diantara batupasir tersebut. Lapisan breksi dijumpai hanya di bagian bawah dari formasi ini. Semakin ke atas batulempung semakin dominan dan batupasir semakin tipis dan halus.
Sebanyak 15 (lima belas) contoh batuan telah dipilih untuk analisa paleontologi. Delapan contoh diambil pada lintasan bagian timur dan tujuh contoh telah diambil pada lintasan bagian barat. Sedikitnya 3 (tiga) datum umur dapat ditentukan dari kemunculan beberapa fosil indek yang penting diantaranya adalah: Globoroalia menardii, Globorotalia acostaensis, Globorotalia menotumida dan Hestigerina pelagica. Ketiga datum tersebut adalah N14-N15, N16 dan N17. Dengan demikian Formasi Cantayan yang tersingkap di Sungai Cibeet, Cianjur adalah berumur dalam rentang waktu antara N15 – N 17 (Miosen Akhir).
Kata Kunci: Formasi Citayan, Cibeet, Paleontologi, Fosil Index
ABSTRACT
The Cantayan Formation which is revealed on the Cibeet River is composed of sandstones in various grain sizes and thicknesses, breccia and claystone. At the bottom are arranged by coarse sandstone intervals, with thicknesses varying from 30 to 60 cm, and can be piled up to a thickness of more than 5 meters. Claystone inserts occasionally appear between these sandstones. The breccia layer is found only at the bottom of this formation. Increasingly the claystone is increasingly dominant and the sandstone is getting thinner and smoother.
A total of 15 (fifteen) rock samples have been selected for paleontological analysis. Eight samples were taken on the eastern trajectory and seven samples were taken on the western trajectory. At least 3 (three) datum ages can be determined from the appearance of several important fossil indexes including: Globoroalia menardii, Globorotalia acostaensis, Globorotalia menotumida and Hestigerina pelagica. The three datums are N14-N15, N16 and N17. Thus the Cantayan Formation which was revealed on the Cibeet River, Cianjur is aged in the time span between N15 - N 17 (Late Miocene).
Keywords: Citayan Formation, Cibeet, Paleontology, Index Fossil