quartz-rich sandy facies behind the miocene volcanic activity in south east java: insight from...

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IPA13-SG-031

PROCEEDINGS, INDONESIAN PETROLEUM ASSOCIATION

Thirty-Seventh Annual Convention & Exhibition, May 2013

QUARTZ-RICH SANDY FACIES BEHIND THE MIOCENE VOLCANIC ACTIVITY IN SOUTH

EAST JAVA: INSIGHT FROM SANDSTONE CHARACTERISTICS WITHIN JATEN

FORMATION

Rian Cahya Rohmana*,***

Fajar Puspo Dewi*,***

Sutrio Wibowo**

Adrean Novadhani***

Iqbal Fardiansyah***

ABSTRACT

East Java lies on the South East (SE) margin of

Sundaland and is filled by thick sequence of

Tertiary volcanic sediment. Products of Oligo-

Miocene volcanic and quartz deposits are

widespread, acting as important hydrocarbon

accumulation. SE Java is one location where quartz-

rich sandstone is found around volcanic arc. This

paper is analyzing Miocene volcanic quartz

sandstone that has been discussed as potential

reservoir.

Sandy facies within Jaten Formation ischaracterized by flaser sandstone (Sfl), low angle

cross lamination sandstone (Sla), wavy lamination

sandstone (Sw), ripple cross lamination sandstone

(Sr) and horizontal laminated sandstone (Sh) with

total thickness of 2 to 9 m. Thin coal layers

occasionally present in muddy facies, considered as

a good intra formations source rock. Previous

studies describes sandstones of the formation

contains abundant bipyramidal, faceted crystal, and

embayed volcanic quartz grain, indicating volcanic

origin.

Integrated biostratigraphy, petrography and

lithofacies analysis have shown that sandstone of

Jaten Formation was deposited in terrestrial to

transition environment with fluvial point bar and

sand flat facies associations. They are interpreted as

a part of lower flank of the volcanoes in the

southconnected to open marine in the northern part,

indicating fluvial to estuary depositional system in

active volcanic setting. The existence of thic k

volcanic materials in SE Java was neglected

* Department of Geology, UPN “Veteran”Yogyakarta

** Sedimentology Lab., UPN “Veteran” Yogyakarta

*** Geopangea Research Group (gprg)

previously. As a matter of fact, it has valuable

implication for basin history, provenance, and

reservoir properties that will resolve future

exploration problems in SE Java.

Keyword: quartz-rich sand, volcanic, Jaten

Formation, Sandy Facies

INTRODUCTION

The research area is located in Batuwarno and

Giriwoyo Villages, Wonogiri, Pacitan Area, Central

Java. The area is part of Southern Mountain Zone(Figure 2). The Miocene quartz rich sandstones has

been a subject of research of potential reservoir and

source rock in volcanic environment.

This study aims to get better understanding of

depositional facies of estuary system within

volcanic setting. The Jaten Formation that contains

quartz rich sandstone from volcanic origin is one

good example, an interesting study for potential

reservoir and source rock. A preliminary study of

outcrops is probably the most reliable method to

support the exploration in SE Java.

REGIONAL GEOLOGICAL SETTING

East Java is located southeast of Sundaland margin

(Figure 1). Sundaland is the core of SE Asia

continent and is commonly perceived to be the main

source of sediment to East Java (e.g. Ardhana,

1993; Sribudiyani et al., 2003). East Java is

subdivided into four east-west trending zones based

on the Van Bemmelen (1949). The zones weredetermined by Smyth (2005) based on stratigraphy

and structural configuration. From North to South,

those are (Figure 2):

©



Southern Mountains Zone

The Southern Mountain Zone consists of thick

oligo-miocene volcanogenic sendiment with

siliciclastic sediment that lies unformably on

Mesozoic basement. The lithology of this area

consisted of siliciclastic, volcaniclastic, volcanic

and carbonates rocks. The research area is located

in this zone.

Present-day volcanic arc:

The Late Miocene volcanic activity was reactivated

at the position of the present-day arc and

deformation events occurred throughout East Java.

Kendeng Zone:

Is the main Oligo-Miocene depocenter in East Java.

It contains thick sequences of volcanogenic and

pelagic sediments which now is W-E trending fold

thrust belt.

Rembang Zone:

The Eocene-Pliocene sequence includes syn-rift

deposits and post-rift deposits such as fluvial

deltaic, deeper marine, shallow marine clasticsediments and extensive carbonates are found in

this area. This zone is bounded by ENE-WSW

fault-high (Rembang High) from Kendeng zone in

the south and with many E-W structural trend.

METHODS

This research used publications, data and outcrop

observation that include sections profiling, spot

sampling, and geological mapping. In addition,

laboratory analysis consisted of petrographyanalysis and paleontology analyses were conducted

as well. All data were integrated to create

depositional facies model of estuary in volcanic

environment setting. To meet the objectives of the

study, analyses were performed as below:

a.

Facies identification (lithofacies & facies

association).

b. Laboratory Analysis (petrography, mineralogy /

QFL, paleontology).

c.

SEM and Quartz Type (taken from Smyth,

2003).

LITHOFACIES AND DEPOSITIONAL

FACIES OF JATEN FORMATION

The focus of lithofacies and depositional facies

study is of the 7-12 km Jaten Formation, located in

along Wonogiri to Pacitan area. Physical analysis

was conducted by sampling, outcrop observation,

and graphic log. The facies in Jaten Formation is

divided into sandy facies and muddy facies.

Sandy Facies

The quartz sandstone can be grouped in several

lithofacies based on their characters; flaser

sandstone (Sfl), low angle cross lamination

sandstone (Sla), wavy lamination sandstone (Sw),

ripple cross lamination sandstone (Sr) and

horizontal laminated sandstone (Shl). Rockdescription is white to yellowish white, fining

upward sequence, very fine to gravel of quartz

grain, angular to well rounded of grains with flaser,

low angel cross lamination, wavy lamination, ripple

cross lamination and parallel lamination

sedimentary structures. Thickness ranges from 2 to

7 m (Figure 4).

Petrography analysis and QFL point measurement

revealed the predominant composition of the

sandstone; quartz grains slightly mixed with

feldspar and lithic (Figure 5). Based on faciesassociation analysis, most of the facies are related to

sandflat deposits that are deposited in transitional

environment (Figure 7).

Muddy Facies

Several muddy facies observed in Jaten Formation

are: Massive carbonaceous shale (CHm)

characterized by lenticular lignites within

carbonaceous shale, the thickness is approximately

estimated 0.5 – 1 m. Massive coal (Cm)

occasionally presents among massive carbonaceusshale (CHm). The coal thickness ranges 0.3 -0.7 m

(Figure 6). The presence of bentonic foram

Elphidium quntori, Rotalia. sp, Quingueloculina sp.,

and shell fragment of gastropod, pelecypod,

molusca indicate transitional environment. The

facies is interpreted as mudflat deposits.

DISCUSSION

South East Java Basin is considered as frontier area

often overlooked due to the volume of Eocene-

Miocene volcanogenic sediments in the area.

However, some evidences show the possibility of

petroleum potential. Eocene volcanic activity in SE



Java is indentified from rock samples. The Plinian

type explosion has created large eruptive columns,

extended to as high as 50 kilometers into the

atmosphere. Magmas were acid to intermediate

such as rhyolitic to dacitic, trachytic and phonolitic

magmas (Smyth, 2003., Fisher et al., 1998). Some

of andesitic to dacitic Oligocene intrusions could be

examined in the study area and are potential source

of quartz (Figure 8).

Thus, their provenance has significantly contributed

to quartz-rich grains for sandy facies of Jaten

Formation. In tropical environment, the single

eruption, reworking and weathering of tuffs, ash

falls, and pyroclastic debris can form well-sorted

single crystal, angular shards or fragments due to

concentration within the magma chamber (Smyth,

2003., Cas and Wright,1987).

Scanning Electron Microscope (SEM) revealed that

quartz grains of Jaten Formation are bipyramidal

quartz, perfect crystal faces or alternatively have

large embayment with features indicating crystal-

melt interaction producing multiple phases of

crystal growth. Other features show skeletal grains,

negative crystals, cracked tile -like fractures,

zonation, tracks or scours along the crystal surfaces

and microcrystalline surface growth. (Smyth, 2003.,

Donaldson and Henderson, 1988). The variety of

features indicates the quartz grains are derived froma volcanic origin (Figure 9).

The Jaten Formation contains quartz sandy facies of

Midlle Miocene tidal deposits deposited in volcanic

arc setting. The abundant volcanic quartz grains

found in the sandy facies indicates good reservoir

potential analog in SE Java. Meanwhile the

alterations of feldspar, volcanic glass constitute

muddy facies. The presence of Eocene-Miocene

volcanic arc in Southern Mountain Zone has

suggested that the study area is adjacent to the

volcanic center. The older formations such asSemilir Formation in south west or equivalent

Besole Formation north east of study area that

composed of volcanic breccias, lava, tuff, and

tuffaceous sandstone have a good role in controlling

the distribution of high and low area toward the

Jaten Formation.

The sandy facies within Jaten Formation has been

interpreted as part of lower flanks of volcanoes that

is it locally deposited and is interfingering with rim

carbonate reef (ex : Punung in NW and Wonosari

in SW) in the margin of high area . The lower flank

of volcano was swampy forest flood plain, resulting

muddy facies containing carbonaceous shale and

thin coal. The rivers were connected to transition

zone to open marine in the northern part. In this

case, integrated biostratigraphic and facies have

obviously proven distinctive characters of tidal

system such as intertidal and estuary tidal bars close

to active volcanic arcs. Volcanic input may have

influenced siliciclastic system and carbonate

development around active volcanic arcs without

killing carbonate-producing organisms and stop

supplying clastic provenance, causing deposition to

cease (Wilson and Lokier, 2002).

CONCLUSION

1.

The facies analyses of Jaten Formation are

divided into sandy facies and muddy facies. The

sandy facies consists of flaser sandstone (Sfl),

low angle cross lamination sandstone (Sla),wavy lamination sandstone (Sw), ripple cross

lamination sandstone (Sr) and horizontal

laminated sandtone (Sh) with dominant

composition of quartz grain, feldspar and silica

mud. The muddy facies comprises of massive

shale (SHm) characterized by lenticular lignites

within carbonaceous shale with massive coal

occasionally present among massive shale

(SHm).

2.

Quartz grains is dominant in Jaten formation.

The quartz grains are previously reported to be bipyramidal quartz, perfect crystal faces or

alternatively have large embayments with

features indicating crystal-melt interaction

producing multiple phases of crystal growth,

skeletal grains, negative crystals, cracked tile -

like fractures, zonation, tracks or scours along

the crystal surfaces and microcrystalline surface

growth. The grains feature volcanic origin.

Some of andesitic to dasitic of Oligocene

intrusion may be commonly potential for local

provenance to Jaten Formation.

3.

The sandy facies within Jaten Formation is

interpreted as part of lower flanks of volcanoes,

locally deposited and is interfingering with rim

carbonate reef (ex: Punung in NW and

Wonosari in SW) in the margin of high area .

Thus, the active volcanism was not necessarily

disturbing or ceasing the siliciclastic system and

carbonate development. The lower flanks of

volcanoes were swampy forest flood plain,

resulting muddy facies of carbonaceous shale

and thin coal that is potential intraformational

source rock. The rivers connected to transition

zone formed the intertidal and estuary tidal bars

as potential reservoir. Those are obviously



proven distinctive characters of tidal

environment that really close to active volcanic

arcs.

4.

South East Java as frontier area has previously

been overlooked due to the volume of

volcanogenic sediments. However there are

several evidence of petroleum component in

this area, as presented in the Jaten Formation.

This can be used for further study on basin

history, provenance, and reservoir properties to

resolve exploration problems.

ACKNOWLEDGEMENTS

This study is part of the author’s thesis supported by

GeoPangea Research Group and Department ofGeology UPN”Veteran”Yogyakarta. Special

acknowledgment to Agung Budiman and Leon

Taufani who reviewed this paper, GPRG members

and Pangea 2007 for help during fieldwork, UPN

geology laboratories for sample analysis, and IPA

committees for publishing this paper.

REFERENCES

Smyth, H., Hall, R., Nichols,J,G., 2008, Cenozoic

volcanic arc history of East Java, Indonesia: The

stratigraphic record of eruptions on an active

continental margin, The Geological Society of

America Special Paper 436

Smyth, H., Hall, R., Hamilton, J.P., and Kinny, P.,

2005, East Java: Cenozoic basins, volcanoes and

ancient basement: Jakarta, Proceedings, Indonesian

Petroleum Association Annual Convention, 30th, p.

251–266.

Smyth, H., Hall, R., Hamilton, J.P., and Kinny, P.,

2003, Volcanic Origin Of Quartz-Rich Sediments In

East Java: Jakarta, Proceedings, Indonesian

Petroleum Association Annual Convention, 29th, p.IPA03-G-014

Wilson, M.E.J., and Lokier, S.W., 2002,

Siliciclastic and volcaniclastic influences on

equatorial carbonates: Insights from the Neogene of

Indonesia: Sedimentology, v. 49, p. 583–601



Figure 1 - Regional tectonic setting of se asia, the study area is highlighted by yellow box

(smyth,2003).

Figure 2 - Digital elevation model (shuttle radar transect mission) overlain by schematic zonation

of east java, the study area is highlighted by yellow box (after symth,2003).



Figure 3 - Shuttle radar transect mission overlain by regional geological map of study area (after

grdc,1992).

A

B

C

Figure 4 - A) Outcrop Of Jaten Sandstone In Sidorejo Village , (B) Close Up Of Quartz Sandstone

With Parallel Lamination Structure, And (C) Close Up Of Quartz Sandstone With Flaser

Structure.



Figure 5 - Point counting of qfl and quartz types showing jaten formation predominantly composed

of volcanic quartz origin.

A B

C D

Figure 6 - Muddy Facies A) Massive Carboneceous Shale, (B) Massive Shalestone, (C&D)

Massive Coal.



Figure 7 - Sedimentological Log To Identify Facies Of Jaten Formation.



Figure 8 - Oligocene Dasitic Intrusion Is One Of Potential Source For Jaten Quartz-Rich Sandstone.

B C D

A0 A1

A2 A3

Figure 9 - The several thin sections of jaten quartz-rich sandstones,( a0&a1) composed of

bypiramidal quartz grains and rounded embayment. (a2 & a3) quartz wacke in sandy

facies, (b) bypiramidal crystal. Previous study (smyth,2003) c) sem image of rounded

embayments and me lt reaction textures. F) sem image of microcrystalline growth on the

surface of the grain. White bar = 1mm in photomicrographs.

quartz-rich sandy facies behind the miocene volcanic activity in south east java: insight from...

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