GEOLOGY AND SEDIMENTATION OF TERRACE SEDIMENTS AT SEMBUNGAN AREA, MEGERI VILLAGE, KRADENAN DISTRICT, BLORA REGENCY, CENTRAL JAVA PROVINCE

GEOLOGY AND SEDIMENTATION OF TERRACE SEDIMENTS AT
SEMBUNGAN AREA, MEGERI VILLAGE, KRADENAN DISTRICT, BLORA
REGENCY, CENTRAL JAVA PROVINCE
Sigit Maryanto #
# Geological Survey Institute
Jl. Diponegoro No. 57 Bandung, 40122
Telp. 022-7203205 ext. 180, E-mail: sigit@grdc.esdm.go.id
ABSTRACT
The occurrence of the Early Quarternary Solo River terrace commonly associates with
vertebrate fossils, including hominid. The Solo River terrace cropped out at
Sembungan area is a good object for studying the sedimentology of terrace sediments
and paleo-topograpy of Solo River in associated with the discovery of the vertebrate
fossils. Detailed topography and geological mapping completed with detailed
stratigraphic section shows the dividing unit of the terrace sediments.
The terrace sediments of this area covered unconformably the Tertiary Kerek or
Kalibeng Formations. Based on the detailed geological mapping, the Solo River
terrace can be divided into three units : gravel unit in the lower part, gravely sand unit
in the middle part, and mud unit in the upper part. The lower part consists of gravel bar
or bedform deposit with sporadically intercalated by gravity flow sediment,
predominated by cobble and pebble beds. The middle part consists of point bar
deposit, predominated by gravely sand and sand beds. This terrace sedimentation was
ended by suspended mud deposits at river overbank, predominated by massive mud
beds with several carbonate nodules (calcretes) and plant remains. Both of angular -
subangular in various size and rounded small size of the vertebrate fossil fragments
founded in the lower and middle parts of this terrace.

THE NEW APPROACH FOR SUBDIVISION OF PLEISTOCENE NANNOPLANKTON ZONATION IN WAIPOGA-WAROPEN BASIN, PAPUA: CASE STUDY OF “T” WELL SECTION

THE NEW APPROACH FOR SUBDIVISION OF PLEISTOCENE
NANNOPLANKTON ZONATION IN WAIPOGA-WAROPEN BASIN, PAPUA:
CASE STUDY OF “T” WELL SECTION
Panuju∗
* PPPTMGB “LEMIGAS” Jakarta
Jalan Ciledug Raya, KAV. 109, Cipulir – Kebayoran Lama – Jakarta Selatan 12230 – Indonesia
Telex: 47172, Faximile: 62-21-7246150, P.O. Box:1089 Jakarta 10010, Phone: (021) 7394422,
7393958, 7394091, 7394856, 7394890, 7394901
Email: panuju@lemigas.esdm.go.id
ABSTRACT
Waipoga-Waropen Basin is placed in northern part of Papua on the island of New
Guinea. The gas discoveries had been made since 1958 in this basin, however, no
economic value of reserves lead to the not producing basin state until this time. The
main problem in Waipoga-Waropen Basin is great thickness of Pleistocene
sedimentary layers (until 7500m) as product of turbidite system (Wold & Barret, 2000).
This makes difficulty in well section correlation based on the conventional
biostratigraphy since individual layers within that section is being small part of biozone.
Many reworked nannoplankton as implication of turbidite deposit are also being
complicated aspect in biostratigraphic analysis.
The Pleistocene ranges from 1.806 m.a. to 11.550 k.a. It was the most recent episode
of global cooling or ice age took place. In nannoplankton biostratigraphy, this age is
characterized by the extinction of Discoaster brouweri (Discoaster group) at the bottom
and the first occurrence of Emiliania huxleyi at the top.
The quatitative nannoplankton investigation of “T” well has been done, and there is
evident that its sedimentary section gives the excellent nannoplankton assemblages to
subdivide Pleistocene age sediments of Waipoga-Waropen Basin (Zone NN19) into 9
subzones. Biomarkers from the bottom to the top consist of: LO of Discoaster brouweri,
FO of Gephyrocapsa caribbeanica, FO of Gephyrocapsa oceanica, LO of Cacidiscus
macintyre , LO of Helicosphaera sellii, FO of Reticulofenestra asanoi, FO of
Gephyrocapsa parallela, LO of Reticulofenestra asanoi, FO of Helicosphaera inversa
and LO of Pseudoemiliania lacunosa. The sediments belong to zone NN 20 that placed
in the uppermost part of Pleistocene were not analysed.

TURBIDITES DEPOSITIONAL SYSTEMS OF THE LOWER HALANG FORMATION, STRATAL ARCHITECTURE OF SLOPE TO BASIN FLOOR SUCCESSION

TURBIDITES DEPOSITIONAL SYSTEMS OF THE LOWER HALANG
FORMATION, STRATAL ARCHITECTURE OF SLOPE TO BASIN FLOOR
SUCCESSION
M. Ma’ruf Mukti1, 4 , Cipi Armandita2, Hade Bakda Maulin3 and Makoto Ito4
1) Puslit Geoteknologi – LIPI, Jl. Sangkuriang Bandung 40135, telp: 022-2503654 fax: 022-
2504593, email: maruf.mukti@gmail.com; 2) BPMIGAS, Jakarta;
3) Paradigm Geophysical Indonesia, Jakarta; 4) Dept. of Earth Sciences, Chiba University, Japan
ABSTRACT
A sedimentological study in the western part of North Serayu Basin has been
conducted and concentrates on the lowermost, 350 m thick mud/sand-rich depositional
system of the Middle–Late Miocene Halang Formation. On the basis of field mapping,
observation of centimeter-scale lithofacies features and laboratory works, lithofacies
were identified and grouped into four lithofacies associations. These lithofacies
associations include: channel and overbank deposits, sheet-package sandstones,
sediment waves and/or distal overbank deposits, and hemipelagic deposits. Several
ash tuff beds and hemipelagic deposits intervals were used as datums for clarifying
spatial and temporal variations of the four lithofacies associations in seven measured
sections along the trough axis over 22 km. Overall, the succession shows downslope
direction to the east-southeast, with sand percentage range from 50%–25%. Features
observed in the channel-fills suggest the high-sinuosity patterns. Sheet-package
sandstones are interpreted to represent both frontal-splay and crevasse-splay deposits
in relation to channel-sheet package and overbank deposits, respectively. Some of the
geometry of fine-grained intervals exhibit wave-like geometry and interpreted to
represent sediment-waves on a distal overbank environment. Six stages of depositional
units have been mapped and their general pattern of the stages shows landward and
basinward movement of the Halang turbidite systems. The direction of paleotransport
from west-northwest to the east-southeast can be explained by the existence of a paleohigh to the west of research area that supply the sediment source to the lower
Halang Formation. The development of calcareous and volcanic deposition within lower
Halang Formation possibly indicates the development of proto-Ciremai and carbonates
equivalent to Parigi Formation in the Arjawinangun High to the northwest of research
area.

SEDIMENTARY PHASE OF SUMBA ISLAND (INDONESIA)

SEDIMENTARY PHASE OF SUMBA ISLAND (INDONESIA)
C.I. Abdullah a, E. Suparka a, V. Isnaniawardhani b
a Program Studi Teknik Geologi, Institut Teknologi Bandung, Jalan Ganesha 10 Bandung
b Teknik Geologi, Universitas Padjadjaran, Jalan Raya Bandung-Sumedang Km. 21
Jatinangor, Sumedang
ABSTRACT
The island of Sumba, presently located in the southern row of islands of the Eastern
Nusa Tenggara province of Eastern Indonesia, has a unique position, being part of the
Sunda – Banda magmatic arc and subduction system. It represents a continental
crustal fragment located at the boundary between the Sunda oceanic subduction
system and the Australian are continent collision system, separating the Savu Basin
from the Lombok Basin. New data on sedimentary rocks collected from Sumba are
presented in this paper, including biostratigraphy supported by lithostratigraphy and
geodynamic.
The stratigraphy of Sumba is composed of slightly to unmetamorphosed sediments of
Mesozoic age, unconformably overlain by considerably less deformed Tertiary and
Quaternary deposits.
Three distinct calc – alkaline magmatic episodes are recorded during Cretaceous –
Paleogene are : the Santonian – Campanian episode (86-77 Ma), the Maastrictian –
Thannetian episode (71-56 Ma), the Lutetian – Rupelian episode (42 – 31 Ma).
The island is distinguished into four sedimentary phase; they are : (i) The Late
Cretaceous to Paleocene stage (96 to 54 Ma) represented by marine turbidites
accompanied by the Santonian-Campanian (86-77 Ma) and the Maastrichtian-
Thanetian (71-56 Ma) magmatic episodes respectively; (ii) The Paleogene stage (66.5
to 25.2 Ma) represented by neritic sedimentation accompanied by Lutetian-Rupelian
magmatic episode (42-31 Ma); (iii) The Neogene stage (25.2 to 1.65 Ma) is
characterized by rapid sedimentation in a deep sea environment; (iv) The Quaternary
stage (beginning 1 Ma) was marked by the uplift of terraces.
The relatively simple tectonics of Sumba suggests that the island has never been
subjected to intense deformation. This implies that from Late Cretaceous-Neogene
time Sumba has never been involved in the collision between the Indian – Australian
and Asiatic plates, except during a minor compressive episode in the Paleogene.
Keywords : Sumba, Mesozoic, Paleogene, Neogene, Quartenary, biostratigraphy,
foraminifers, nannoplankton, geochronology, magmatic episode

NEOGENE TECTONIC AND SEDIMENTARY CONTROL TO HYDROCARBON GENERATION IN BANGGAI BASIN, EASTERN SULAWESI

NEOGENE TECTONIC AND SEDIMENTARY CONTROL TO
HYDROCARBON GENERATION IN BANGGAI BASIN, EASTERN
SULAWESI

Bagus Priyanto1, Muh. Rizwan Fitriannur1
1 HMG (Himpunan Mahasiswa Geologi) UNPAD and UNPAD SC of AAPG,
Faculty of Geology, Padjadjaran University
Jl. Raya Bandung-Sumedang km.21, Jatinangor, Sumedang, West Java 45363.
Tel and Fax : (022) 779-6545 Email : priyanto_bagus@yahoo.co.id

ABSTRACT
The Banggai Basin is located eastern Sulawesi, south of Molucca Sea. This region is
one of the most complicated active margin in term of geology. This basin as a part of
the Banggai-Sula microcontinent.
Regional tectonics of Banggai Basin is the collision complex/ foreland thrust belt which
interpreted to have formed as a result of the collision, during the Miocene, of the
Banggai-Sula Continental Microplate and Asiatic Plate. The Collision resulted in
considerable folding, faulting, and imbrication of the sedimentary section, and also in
the obduction of one of the largest masses of ophiolite in the world, which known as the
East Sulawesi Ophiolite Belt. Those tectonic activities have affected the stratigraphy
across The Banggai Basin. It’s stratigraphy is related to two distinct time periods, the
first representing a continental margin rift to collision, and the second representing a
foreland basin molasses sequence. Both of the periods have contribution to
hydrocarbon generation in Banggai Basin. The increasing of geothermal gradient
cause the collision probably also has contribution in this area for hydrocarbon
generation.
The presence of numerous oil and gas seepages in north-west Taliabu, active wet gas
seepages near Falabisahaya in Mangole, oil and gas from the Dongkala-1 well, gas
from Minahaki-1 and Matindok-1 well, prove that hydrocarbons have been generated in
the area from thermally mature source rocks and have migrated into suitable traps.
Source rock, reservoir rock, and sealing rock are all present within the Miocene
sequence. Suitable traps are present both structural and stratigraphic traps.
By reviewing publications about the Banggai Basin, this paper aims to stimulate the
idea that hydrocarbon exploration in the Banggai Basin still have big chance to find
more hydrocarbon. Eventhough the sequence rocks of this basin probably started in
late Paleozoic until Cenozoic, but our focus is Neogene ago.

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SANGIRAN DOME, CENTRAL JAVA : Mud Volcanoes Eruption, Demise of Homo erectus erectus and Migration of Later Hominid

SANGIRAN DOME, CENTRAL JAVA :
Mud Volcanoes Eruption,
Demise of Homo erectus erectus and Migration of Later Hominid

Awang Harun Satyana 1)
1) BPMIGAS (Badan Pelaksana Kegiatan Usaha Hulu Minyak dan Gas Bumi)
Patra Office Tower, 22nd Floor, Jalan Jenderal Gatot Subroto, Kav. 32-34, Jakarta 12950
Telp : 021-52900245, Fax : 021-52900118, E-mail : aharun@bpmigas.com

ABSTRACT
Sangiran Dome, located 12 km to the north of Surakarta (Solo), Central Java is a
famous site in the Quaternary geology due to the exposures of Pleistocene rocks and
fossils of hominids and vertebrates.
Sangiran Dome is a remnant shale diapir and mud volcanoes complex. This is based
on the nature of deformation, presences of several saline water and methane gas
seeps, and erupted materials including exotic blocks of metamorphic basements to
Pliocene rocks. Based on the deformation and age dating, the diapiric deformation and
eruption is considered took place between 0.7 and 0.5 Ma –million years ago (middle
Pleistocene) and could repeat until 0.12 Ma (base late Pleistocene).
Hominid (early human) called the sub-species Homo erectus erectus lived in the
Sangiran Dome. Their fossils were found in the upper part of Pucangan and lower part
of Kabuh Formations. They lived in the Pleistocene (ages remain in dispute as 1.7-1.0
Ma, 1.3-0.7 Ma, or 1.0-0.5 Ma). The termination of the sub-species between 0.7-0.5 Ma
could be contemporaneous with the eruption of the Sangiran mud volcanoes. The
eruption possibly affected the demise of Homo erectus erectus.
The eruption of Sangiran mud volcanoes could also affect the migration of later
hominid (sub-species Homo erectus ngandongensis / soloensis). The sub-species did
not live in Sangiran area possibly the area was in-habitable due to the eruption. The
sub-species migrated eastward downstream of the Solo River into the areas of
Sambungmacan, Trinil, Ngawi, and Ngandong where they lived until the latest
Pleistocene (0.05 Ma).

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GEOMOETRY OF ALASKOBONG FOLD

GEOMOETRY OF ALASKOBONG FOLD

Aswin Mustofa1, Salahuddin Husein2, and Ignatius Sudarno2
1 Student at the Dept. of Geological engineering, Gadjah Mada University
2 Lecture at the Dept. of Geological engineering, Gadjah Mada University
Jl. Grafika 2, Yogyakarta 55281

Abstract
Alaskobong Fold is located in Alaskobong Village, Sumberlawang District, Sragen
Regency, Central Java Province. It lies in the western Kendeng Zone, an area that for
decades have received full attention for hydrocarbon exploration as it is close to the
profilic region of NE Java Basin. The study area is a 300m long gently hill cut by the NS
railroad of Solo-Gundih and thus formed the 20 m separated eastern western walls
showing excellent exposures of the fold outcrops. Tectonics and soft-sediment
deformation developed in the carbonaceous sandstone and marl of the Kerek
Formation and produced a wide variety of geological structures that noticeable along
the eastern and western walls.
The main structure exposed in the central part of the hill is a synformal depression that
have been topographically inverted. Its trend apparently is different on both wall, NESW
in the eastern wall and E-W in the western wall. The northern part is characterized
by vertical beds and intensive strike-slip fault, whilst the western wall exposes gently
westward dips.
Those differences on the structural types and styles indicate a multiphase or
superposed tectonics. This study might provide an important contribution to
understanding of hydrocarbon traps and migration in the western Kendeng Zone.

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