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Name Isnianto Saputra and Rian Cahya RohmanaSchool/CollegeUPN Veteran Yogyakarta
Address of School/College Jl. SWK 104 (Lingkar Utara) Condongcatur
Himpunan Mahasiswa Geofisika (HMGF)
Fakultas Matematika dan Ilmu Pengetahuan Alam
Universitas Gadjah MadaSekip Utara Unit III F-MIPA UGM PO BOX BLS 21Yogyakarta 55281
STRATIGRAPHY SEQUENCE BASED ON OUTCROP DATA APPROACH ON
INTREPERTATING DUKUH-FORMATIONS DEPOSITIONAL
ENVIRONTMENT (STRATIGRAPHY)
STRATIGRAPHY SEQUENCE BASED ON OUTCROP DATA APPROACH
ON INTERPRETATING DUKUH-FORMATIONS DEPOSITIONAL
ENVIRONMENT
Isnianto Saputra*,**
Rian Cahya Rohmana*,**
ABSTRACT
Dukuh Formation is a Late Oligocene Formation belongs to the southern mountain
range. The study area is located in Samigaluh and Kalibawang district, Kulonprogo,
Yogyakarta. The paper emphasizes the study of depositional environment utilizing the
concept of sequence stratigraphy. Field observation and measuring section method has
been done at the two different location which is supported by sedimentological,
paleontological and petrographical analysis. Based on the observation and analysis it is
revealed that the deposit on the first measuring section is characterized by the
occurrence of mPSm, csGu, vcSs, cSo, mSl, csGs, csmSs, cSfu, csGs, fSl, csGi lithofacies,
whereas, the second measuring section are characterized out by csGm, Gs, tmSs, Lv, Cs,
csmSm, csGm, cscPSs, Gic, Cs, csmSvb, csGsc, mSs, vcSh, csGg, csSs, csSl, csGa, Pcs, csGs,
fSr, csmSvb lithofacies. Interpretation using facies model is merely unsatisfied because
the lacks of appropriariety so, sequence stratigraphy is prefered. Based on it, lower
Dukuh Formation was interpreted as early lowstand system tract is deep marine. Dukuh
Formation was interpreted as late lowstand system tract is shallow marine, whereas
transgressive system track was representated by Limestone of Jonggrangan Formation.
Keywords: Dukuh, depositional environment, lowstand
INTRODUCTION
The study area was located at Samigaluh district, kulonprogo regency, D. I.
Yogyakarta province. The trevel time to get to the study area is around 45 minutes from
Yogyakarta, and it can be through by the motorcycle and car with good asphalt
condition.
Stratigraphicaly, in the early study dukuh Formation was involved within old
andesit Formation by Van Bemmelen (1949), the processes which occurred has a
relationship with the volcanic activity event at the java island at oligosen-miosen. But, in
further study Pringgoprawiro and Riyanto (1987) did the revision to the classification of
Van Bemmelen. They devided old andesit Formation and introduced two new Formation
both Kaligesing Formation and Dukuh Formation. Kaligesing Formation is characterized
by the rock unit in land deposit, it is composed by intercalation volcanic breccias, lava,
tuffaceous sandstone, and lahar deposit. whereas Dukuh Formation is characterized by
the deep marine deposit which is composed by intercalaton polymic breccias,
tuffaceous sandstone, claystone, and interbedded by carbonate rocks.
* Geological Engineering Dept. UPN Vet eran Yogyakarta
* Geopangea Research Group (GPRG) Indonesia
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Name Isnianto Saputra and Rian Cahya RohmanaSchool/CollegeUPN Veteran Yogyakarta
Address of School/College Jl. SWK 104 (Lingkar Utara) Condongcatur
Himpunan Mahasiswa Geofisika (HMGF)
Fakultas Matematika dan Ilmu Pengetahuan Alam
Universitas Gadjah MadaSekip Utara Unit III F-MIPA UGM PO BOX BLS 21Yogyakarta 55281
STRATIGRAPHY SEQUENCE BASED ON OUTCROP DATA APPROACH ON
INTREPERTATING DUKUH-FORMATIONS DEPOSITIONAL
ENVIRONTMENT (STRATIGRAPHY)
BASIC THEORY
Facies is defined as sum of physical, biological, and chemical aspect of rock unit in
time and space framework. Facies can be subdivided more specifically depends on need,
just to mention lithofacies, that has a meaning physical and chemical aspect of rock.
Facies and litofacies were significant aspect to deciphering rock strata into more
meaningful and useful unit based on the purpose intended. Intrepertation of
depositional environtment can be supported by the detail descripstion of litofacies, and
after it more advance method, litofacies assemblage, can be done to attain the
information about the depositional environment. The present of facies model become
significant both as a norm and also as a comparation. However this method, which was
regarded as conventional method, simultaneously could become unsatisfied since facies
model usualy cant accommodate sedimentological interpretation on deposit which
founded on different location compared to the deposit that has been extracted to
generate those facies model.
Several alternative method could be utilize, one of those is sequence stratigraphy.
Sequence stratigraphy, branch of stratigraphy which was accepted as formal
stratigraphy unit in SSI since 1996, has basic unit called sequence. Its defined as a
stratigraphic unit composed of a relatively conformable succession of genetically related
strata bounded at its top and base by unconformities and their correlative conformities.
Sequence was defined by unconformities based on Exxon group, whereas Galloway
prefer maximum flooding surface. Sequence consist of system tract, which has definition
linkage of contemporaneous depositional system. There are at least three different
types of system tract. Those are transgressive system tract, highstand system tract, and
lowstand system tract.
METHODS
The study based on outcrops observation and after that continued with somelaboratory analysis. The outcrops observation encompasses sampling of lithological
data, sedimentary structures, outcrops log, measuring section, and geological map.
After that, it was continued with laboratory analysis such as petrography, calsimetry,
paleontology, and outcrops log analysis. At the end, all datas and analysis has been
collaborated to get the interpretation of depositional environment and system tract unit
of Dukuh Formation.
RESULT AND DISCUSSION
- Facies AnalysisIn this study of facies analysis, Tuckers facies classification has been used. From the
result of the analysis there were some lithofacies which can be used to determine the
depositional environment and as basic concept to explain the system tract unit of
Dukuh Formation. Two measuring section has been combined to get one set
stratigraphical assemblage completely. Several lithofacies could be obtained to give the
information about the depositional environment. Precisely there were thirty one
lithofacies occurred in this section. Several keys lithofacies will be explained respectively
below :
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Name Isnianto Saputra and Rian Cahya RohmanaSchool/CollegeUPN Veteran Yogyakarta
Address of School/College Jl. SWK 104 (Lingkar Utara) Condongcatur
Himpunan Mahasiswa Geofisika (HMGF)
Fakultas Matematika dan Ilmu Pengetahuan Alam
Universitas Gadjah MadaSekip Utara Unit III F-MIPA UGM PO BOX BLS 21Yogyakarta 55281
STRATIGRAPHY SEQUENCE BASED ON OUTCROP DATA APPROACH ON
INTREPERTATING DUKUH-FORMATIONS DEPOSITIONAL
ENVIRONTMENT (STRATIGRAPHY)
csGi(Inverse graded bedded calcareous Breccia). This lithofacies wasinterpretated as the result of high density turbidity current deposit on traction
carpet phase.
fSl(pararel laminated fine Sandstone) which was deposited by density currentvia traction current on lower flow regime.
vcSu(slumped very coarse Sandstone) which was deposited by density current inwhich rapid sedimentation play an important role.
cSfu (slumped very coarse Sandstone) which was deposited by resedimentationprocess triggered by seismic process or other process.
mSo(ripple cross laminated medium Sandstone) which was deposited by tractioncurrent so possibly generates ripple bedform and the migration as well.
mPsm(massive medium Pebbly Sandstone) which was deposited by high densityturbidity current resembling debris flow in which gravel can be deposited
alongside sand material.
Lv (vertical bioturbated siltstone) was interpreted as a offshore mud depositedat shelf area, the changing of lower current energy to the higher current energyhas been indicated by a vertical bioturbated.
Gic (inverse graded bedded and scour cast Breccia) was interpreted as the resultof high density turbidity current deposit at the traction carpet phase.
csmSvb (vertical and horizontal bioturbated calcareous medium Sandstone) wasinterpreted as the result of a traction mechanism in wave current at the early
sedimentation phase.
vcSh (hummocky cross bedded very coarse Sandstone) was interpreted as theresult of a traction mechanism deposit in a wave current at the shelf area.
csGs (gradded bedded calcareous Breccia) was interpreted as the result of highdensity turbidity current at the suspense phase.
csGsc (stratified and scoured calcareous Breccia) was interpreted as the result ofhigh density turbidity current at the shelf area in traction mechanism.
fSr (cross ripple fine Sandstone) was interpreted as the result of debris flowdeposit which occurred at the shelf area.
Generally Dukuh Formation can be divided into two different depostional
environment based on lithological facies properties. In the upper of Dukuh Formation,
the presence of hummocky cross bedded, symmetrical ripple and vertical bioturbation
(skolithos), those sedimentary structures generally can be the key to explain that Dukuh
Formation was formed by the fair weather wave and storm wave at the shallow marine
area ( shoreface to offshore ).
At the lower of Dukuh Formation turbidity current deposit has been found. It is
characterized by the presence of slumped bedded, inverse graded, and ripple cross
laminated bed which is interpreted as deep marine deposit (in this case as the upper
fan channel fill, walker, 1984) . the upper part becomes problem if the same approach
to interpreted the lower part of Dukuh Formation is conducted. The problem occurred
since there are no facies model that can explain the occurrence of thick breccias deposit
in this section. Almost all breccias on the facies model have thin thickness because of it
is accepted breccias occur only as a gravel lag deposit. Due to this fact sequence analysis
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Name Isnianto Saputra and Rian Cahya RohmanaSchool/CollegeUPN Veteran Yogyakarta
Address of School/College Jl. SWK 104 (Lingkar Utara) Condongcatur
Himpunan Mahasiswa Geofisika (HMGF)
Fakultas Matematika dan Ilmu Pengetahuan Alam
Universitas Gadjah MadaSekip Utara Unit III F-MIPA UGM PO BOX BLS 21Yogyakarta 55281
STRATIGRAPHY SEQUENCE BASED ON OUTCROP DATA APPROACH ON
INTREPERTATING DUKUH-FORMATIONS DEPOSITIONAL
ENVIRONTMENT (STRATIGRAPHY)
will be conducted to unravel the problem of upper part of Dukuh Formation depositional
environment.
-
Sequence Analysis
The analysis is being conducted to the complete measuring section. First of all
the parasequence is determined based on its bed or bedsets stacking patern wether it is
coarsening, fining, thickening, or thinning. After that the parasequence set is
determined by combining the patern of the parasequence. From this method more
complete depositional linkage system, well known as system tract, can be described.
There are 2 system tract that can be identified from this measuring section, lowstand
system tract and transgressive system tract. Lowstand system tract encompasses the
lower part of Dukuh Formation in which turbidity current deposit is visible. This can be
formulated from the fact that thick submarine fan deposit only possible in condition
where lot of sedimen influx was injected until it reach the shelf margin. This influx
usually accompanied by minor rate of subsidence. This condition happen at lowstand
system tract where the sea level is stable at low level relatively. In this conditionagradation stacking patern is very obvius. This can be seen from the lower part of Dukuh
Formation where the parasequence shown agradation overall patern. The parasequence
set itself consist of several parasequence which show both thining and thickening
stacking pattern. Thining typified channel of the submarine fan whereas thickening
typified the lobes of the submarine fan.
This lowstand deposit continued further upward untill it changes into shallower sea
environment, the upper part of the Dukuh Formation. In this part overall agradation
stacking patern still dominates the section. The deposit in this part is unique since fair
amount of gravel sediment occurred. In first glance its relatively easy to interpretated
this deposit as deep sea deposit because of it. However the occurrence of shallow sea
deposite feature such as hummocky cross bedding, highly bioturbated bed resembleskolithos, coal fragment inside the sandstone bed, etc could obscure that interpretation.
Its more likely a shelf deposit, supported by the paleontological data that has been
obtained from this part of section(more benthonic fossil than planktonic fossil). In this
part the stacking patern of the parasequence set still depicts agradation patern. After
series of intercalation of limey breccias and sandstone a corraline limestone and its
flank was occurred. This is interpretated as the transgressive surface, a surface which
characterize no deposition or in other word the transition from lowstand system tract to
transgressive system tract. This low rate of sedimentation condition allowed corral and
its symbiotic organism to burgeon. Intensive growth in further time generates those
limestones.
Transgressive system tract deposit overlies this transgressive surface. The early
part of the transgressive system tract consist of litology that somewhat similar type of
litology with the upper lowstand system tract deposit. But the overall stacking patern of
the parasequence set is different, where in this part retrograde is the dominant stacking
pattern. In this early transgressive system tract the sediment influx is be still even
though not really significant. The deposition of coralline limestone belongs to
Jongrangan Formation then really conformise the transgressive system tract. it is
supported by the fact that is coralline limestone succession is very thick.
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Name Isnianto Saputra and Rian Cahya RohmanaSchool/CollegeUPN Veteran Yogyakarta
Address of School/College Jl. SWK 104 (Lingkar Utara) Condongcatur
Himpunan Mahasiswa Geofisika (HMGF)
Fakultas Matematika dan Ilmu Pengetahuan Alam
Universitas Gadjah MadaSekip Utara Unit III F-MIPA UGM PO BOX BLS 21Yogyakarta 55281
STRATIGRAPHY SEQUENCE BASED ON OUTCROP DATA APPROACH ON
INTREPERTATING DUKUH-FORMATIONS DEPOSITIONAL
ENVIRONTMENT (STRATIGRAPHY)
Based on this sequence analysis the upper part of Dukuh Formation belongs to
late lowstand deposited in shelf area. Because subsequently after this upper part of
Dukuh Formation is overlied by limestone of Jonggrangan Formation, the transgressive
system tract. The ackwardness of the upper part of Dukuh Formation then can beexplained. The presence of the high area ,the source materials for the sedimentation,
which is very closed to the shoreline might be the approach models to explain about
that. Because the high area is very close, the sediment material undergone relatively
short term transportation. Thus, the materials in gravel size still can be found in shallow
sea environment.
CONCLUSSION
The information based on sequence analysis it could be revealed the upper part
of Dukuh Formation is classified to lowstand system tract deposited in shelf area.
Whereas the ackwardness of this deposit, fair amount of breccia, could be explained by
a model in which the source area is very closed to the shoreline area.
ACKNOWLEDGMENT
The authors would like to particularly thank the Department of Geological
Engineering UPN Veteran Yogyakarta for the support to made this paper. Special
acknowledgement is made to Fery Andika Cahyo and Zaenal Fanani as the fieldwork
team and for the help belongs to the written of this paper, Geopangea Research Group
Indonesia for the discussing, UPN geology laboratories for the sample analysis, and GSC
committee 2011 for publishing this paper.
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Name Isnianto Saputra and Rian Cahya RohmanaSchool/CollegeUPN Veteran Yogyakarta
Address of School/College Jl. SWK 104 (Lingkar Utara) Condongcatur
Himpunan Mahasiswa Geofisika (HMGF)
Fakultas Matematika dan Ilmu Pengetahuan Alam
Universitas Gadjah MadaSekip Utara Unit III F-MIPA UGM PO BOX BLS 21Yogyakarta 55281
STRATIGRAPHY SEQUENCE BASED ON OUTCROP DATA APPROACH ON
INTREPERTATING DUKUH-FORMATIONS DEPOSITIONAL
ENVIRONTMENT (STRATIGRAPHY)
REFERENCES
- Boggs Jr., S., 2006, Principle of Sedimentology and Stratigraphy 4th edition,Pearson Education, Inc, New Jersey, 335-342- Bouma, A. H., 1962, Sedimentology of Some Flysch Deposite, A GraphicApproach to Fasies Interpretations. Elevier Co., Amsterdams, Netherlands.
- Friedman, G. M., Reeckmann, A.(1982), Exploration for Carbonate Reservoir,John Wiley & Sons, New York, 85-89
- Koesoemadinata, R. P, 1981, Prinsip-prinsip SedimentasiDepartemen TeknikGeologi, ITB, Bandung, 65-100
- Tucker, M.E., 2003, Sedimentary Rock In the Field 3rd edition, John Willey &Son, New York, 16
- Van Bemmelen, R. W., 1949, The Geology of Indonesia, vol IA, 2nd ed, TheHague Martinus Nijhoff, Netherlands.
- Walker, R. G. & James, N. P., 1992, Facies Models: Response Sea LevelChange, Geological Association of Canada, Canada.
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Name Isnianto Saputra and Rian Cahya RohmanaSchool/CollegeUPN Veteran Yogyakarta
Address of School/College Jl. SWK 104 (Lingkar Utara) Condongcatur
Himpunan Mahasiswa Geofisika (HMGF)
Fakultas Matematika dan Ilmu Pengetahuan Alam
Universitas Gadjah MadaSekip Utara Unit III F-MIPA UGM PO BOX BLS 21Yogyakarta 55281
STRATIGRAPHY SEQUENCE BASED ON OUTCROP DATA APPROACH ON
INTREPERTATING DUKUH-FORMATIONS DEPOSITIONAL
ENVIRONTMENT (STRATIGRAPHY)
Figure 1. Simplified Geological Map of Kecamatan Samigaluh, the study area are shown in pale orange colour
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Name Isnianto Saputra and Rian Cahya RohmanaSchool/CollegeUPN Veteran Yogyakarta
Address of School/College Jl. SWK 104 (Lingkar Utara) Condongcatur
Himpunan Mahasiswa Geofisika (HMGF)
Fakultas Matematika dan Ilmu Pengetahuan Alam
U i it G dj h M d
STRATIGRAPHY SEQUENCE BASED ON OUTCROP DATA APPROACH ON
INTREPERTATING DUKUH-FORMATIONS DEPOSITIONAL
ENVIRONTMENT STRATIGRAPHY
Figure 2. massive coral Framestone (Fc)
Figure 3. platy coral Bindstone (Bp)
Figure 4. massive coarse Floatstone (cFm)
Figure 5. massive calcareous breccia (csGm)
Figure 6. vertical bioturbated Siltstone (Lv)
Figure 7. vertical & horizontal bioturbated
calcareous Sandstone (csmSvb)
Figure 8. hummocky cross bedding very
coarse Sandstone (vcSh)
Figure 9. slumped very coarse Sandstone
(vcSu)
Figure 10. Facies Analysis and Sequence Analysis of Dukuh Formatin