KULIAH GEOLOGI KELAUTANJURUSAN GEOLOGI

FAKULTAS TEKNOLOGI MINERALUNIVERSITAS TRISAKTI

SEMESTER II, 2002

DOSEN : IR YUSUF SURACHMAN DJAJADIHARDJA MSC

SILABUS

1. PEMAHAMAN MENGENAI GEOLOGIKELAUTAN2. STRUKTUR DAN FORMASI BUMI3. BENTUK DAN CEKUNGAN SAMUDERA4. EVOLUSI CEKUNGAN SAMUDERA5. TEKTONIK6. STRATIGRAFI

II STRUKTUR DAN FORMASI BUMI

Vp = √⁁ + 2µ

Vs = √ µ/

µ⁁ Koefisien Lame

Modulus rigidity

Density

Ray path concept (seismic method) to determine physical properties

B

bT = B + b

bB

medan magnet bumi (B) menginduksi partikel magnetik dalam batuan (b) dan menghasilkan komponen total (T)

Interior could be estimate based on seismic waves propagation

lintasan gelombang seismik jika bumi tidak homogen akibat adanya struktur perlapisan bumi

lintasan gelombang seismik jika kecepatan gelombang seismik meningkat thd. kedalaman

proses internal di dalam inti bumi menyebabkan bumi memiliki medan magnet

Geomagnetik

Sosialisasi HAGI-UI, HG-2007

Gravity Method

Sosialisasi HAGI-UI, HG-2007

gg11 gg22 gg33jarakjarak

gg

Anomali gravitasi hasil pengukuran menggambarkan anomali rapat massa bawah-

permukaan

Sosialisasi HAGI-UI, HG-2007

BENTUK CEKUNGAN SAMUDERA

Kerak samudera terus berubah terhadap waktu karena dua hal;

1. Gerakan lempeng - Samudera Atlantik terus melebar tetapi tidak ada zona subduksi

- Samudera Pacific menyempit karena subduksi lebih menonjol dibanding pemekaran.

2. Bathimetri berubah karena;- kontraksi akibat masa batuan mendingin- pengendapan sedimen dari benua- erosi dan formasi ngarai (canyon) bawah laut akibat pengaruh arus- penyesuaian isostatik

Pinggiran benua

Dua tipe pinggiran benua;

Tipe Atlantik ; aseismik

Tipe Pacific ; pinggiran aktif

Sedimen

1. Pelagic sedimen ialah sedimen yang diendapkan di dasar laut dimana sumbernya berasal dari lautan

2. Terrigenous sedimen adalah sedimen yang diendapkan didasar laut dimana sumbernya berasal dari daratan (continen)

3. Hemipelagic sedimen adalah sedimen yang diendapkan di dasar laut dimana sumbernya berasal dari daratan dan lautan.

Multi Channel Seismic Reflection, Gravity, Magnetic, and Multibeam

Gravity, Magnetic, and Multibeam

SO98-27

Tectonic Evolution of the Celebes Sea

Eocene – Middle Miocene Reconstruction

About 87.7 m unit IV composed mainly of Dark grayish brown to reddish brown claystone including volcanic Indicating an open oceanicenvironment(Rangin, Silver, von Breymann et al., 1990)

Isopach map of sediment unit IIIC and IV (contour interval in second)Grey shadows are topographic high of the oceanic basement

Oligocene Reconstruction

Spreading of the South China SeaStarted at 32 m.y (Taylor & Hayes, 1983,Holloway, 1982)

Satyana et al., 1999

Middle Miocene – Late Miocene Reconstruction

- South China Sea was still spreading,- In the North Borneo, extended South China margin thrusted beneath Borneo- In early Miocene central Borneo was eroded shed sediment into the Kutai, Tarakan and Sandakan basin- In Tarakan basin progradation of deltaic environment was deposited during Eocene – Late Miocene Satyana et al., 1999

New Isopach map of Unit IIIB (middle Miocene turbidite) in seconds (TWT)

Sediment unit IIIA continue deposited up to late Miocene, probably same source environment as sub unit IIIB (major delta complex)

Subunit IIIA consists of Hemipelagic claystoneInterbedded claystone/silty claystone turbidite and Minor carbonate claystone

Rate of accumulation of unit IIIA about33 m/m.y.

Late Miocene-Holocene Reconstruction

Nichols et al., 1999

During late Miocene to Holocene was dominantly by the terrigenous turbidite andHemipelagic sediment. Within sediment unit II, hemipelagic sediment gradually coarsens upward to clayey silt, Silt size consisting of volcanic ash.

Subunit I mostly contain volcanogenic clayey. Most of volcanogenic materials deposited during late Miocene to Holocene were deposited from volcanic arc around Celebes Sea (e.g. Sulu ridge, Mindanao, Sangihe, and North Sulawesi arc)

Sediment accumulation rate of subunit IIIA, II, and I range from 33 – 60 m/m.y.

Sea Level Change

1.Global Warming (Es di Kutub mencair)2.Subside & Accretion of the Basin (Penurunan atau naiknya dasar Samudera )3.Weighting of the Earth’s crust by local ice sheet

Is the sea level changing,or is it the land that is moving?