PRINSIP DASARSTRATIGRAFI

PRINSIP DASAR STRATIGRAFI

Gambaran tentang bermacam jenis batuan danstrukturnya adalah mengikuti aturan ataupengertian mengenai hubungan dan kejadiangeologinya. Dalam hal ini adalah letak antaratubuh batuan, dan sifat hubungannya yangmenyangkut umur, urutan kejadian, dan sejarahpembentukannya.

BEBARAPA PRINSIP DASAR STRATIGRAFI YANGPENTING :

1. HUKUM STENOa. SUPERPOSISIb. HORISONTALITAS/KEDATARANc. KESINAMBUNGAN

2 UNIFORMITARIANISME

3. HUKUM WALTHER

4. FASIES

a. SUPERPOSISI

Modified statement

Law of Superposition : The younger strata at the top in anundisturbed sequence of sedimentary rocks (Anthony, 1955)

" DALAM KEADAAN NORMAL, SUATU LAPISAN BATUAN YANG LETAKNYADIATAS SATUAN LAPISAN YANG LAIN, SELALU BERUMUR LEBIH MUDADARIPADA LAPISAN BATUAN DIBAWAHNYA .

HUKUM-HUKUM STENO (1669)

In an undisturbed rock sequence, the bottom layer of rock isolder than the layer above it, or

The younger strata at the top in an undisturbed sequence ofsedimentary rocks.

Undisturbed strata

Disturbed strata

Disturbed strata

Penekanan pada :

- waktu diterjemahkan hubungan yangbersifat fisik, antar perlapisan

- strata/lapisan, bukan batuan

- kondisi normal, belum mengalamigangguan

b. HORISONTALITAS / KEDATARAN

Modified statement :

Law of Horizontality Sedimentary strata are laid down nearlyhorizontally and are essentially parallel to the surface upon whichthey accumulate (Anthony, 1955)

- Lapisan-lapisan sedimen diendapkan mendekati horisontal danpada dasarnya sejajar dengan bidang permukaan dimanalapisan sedimen tersebut diendapkan.

-Akumulasi lapisan-lapisan sedimen adalah secara vertikal.

- Susunan lapisan yang kedudukannya tidak horisontal berartitelah mengalami proses geologi lain setelah pengendapannya.

c. KESINAMBUNGAN

Modified statement :

Law of Original continuity : The original continuity of water-laidsedimentary strata is terminated only by pinching out against thebasin of deposition, at the time of their deposition (Anthony, 1955)

Lapisan sedimen diendapkan secara menerus dan bersinambungan(continuity), sampai batas cekungan sedimentasinya

Lapisan sedimen tidak mungkin terpotong secara tiba-tiba, danberubah menjadi batuan lain dalam keadaan normal

Pada dasarnya hasil suatu pengendapan yakni bidang perlapisan,akan menerus walaupun tidak kasat mata

Pemancungan : Ketidakselarasan, erosi, morfologi

Berhentinya perlapisan akibat erosi/morfologi

Sedimentary rocks

Sedimentary rocks

Berhentinya perlapisan akibat ketidakselarasan

Berhentinya perlapisan akibat erosi/morfologi

Berhentinya perlapisan akibat erosi/morfologi

Berhentinya perlapisan akibat erosi/morfologi

UNIFORMITARIANISM (HUTTON., 1785):Peneliti lain yang mempunyai sumbangan penting dalam stratigrafi adalahJAMES HUTTON (1785).

Original statement" In examining things present, we have data from which to reason withregards to that which is to happen hereafter. Therefore, upon thesuperposition that the operations on nature are equable and steady, we rind,in natural appearances, means for concluding a certain portion of time to havenecessarily elapsed in the production of these events of which we see theeffects (Hutton, p.217)

Modified statement " The Present is the Key to the Past

Keterangan:Walaupun kita ketahui bahwa setiap zaman mempunyai ciri yang tertentu,misalnya ZAMAN PERM : umumnya beriklim panas, dan ini berbeda denganiklim zaman sebelumnya yaitu ZAMAN, KARBON : dimana mempunyai iklimlebih bersifat lembab, namun proses-proses yang membentuk semua gejalaGeologi dapat dikatakan sama.Proses di bumi terjadi secara berulang-ulang, membentuk suatu SIKLUS.

MODIFIED STATEMENT The present is the key to the past"

The processes (plate tectonics, mountainbuilding, erosion) we see today are believed tohave been occurring since the Earth was formed.

No vestiges of the beginning, no vestiges of theend

Everything changes, only the law of changes doesnot change

Perubahan terjadi sangat lambat perubahanbesar

Proses di bumi terjadi secara berulang ulangsiklus

Bermacam jenis batuan

HUTTONS DOCTRINE OF UNIFORMITY( Playfair, 1802 )

F A C I E S (Greeslv. 1836)

Pada tahun 1836 seorang ahli dari SWISS bernama A. GREESLYmenyebutkan caranya sendiri dalam mempelajari batuan.

Modified statement" The term facies designates the differences, whatever they may be

between formations of the same age; the differences may be either inpetrographic composition. resulting the nature of the substancesdeposited, or paleontologic differnces, resulting from the livingconditions of the animal and plant fossils ".

" FACIES are then difinitely the different kinds of deposite,sedimentary or other, which can be produced simultaneously, at a givengeological moment, just as is the case at the present time. One thenspeaks of the various facies of a formation as one would speak of thedifferent deposits of modern times ".

Keterangan .Greesly mulai melihat fosil sebagai bagian batuan, tidak berdiri

sendiri sebagaimana peneliti sebelumnya.

Shallowmarine

Shallowmarine

Shallowmarine

Beach

Beach

Deepmarine

Deepmarine

River

River

Comparison of sediment deposited

Deepmarine

WALTHER LAW (Walther, 1894)

Modified statement" In other words facies that occur in a conformable vertical core sequence

were formed in laterally adjacent depositional environment ".Note" It is specialty important to note as MIDDELTON (1973) pointed out, that

Walther's Law applies only to successions without major erosional or nondepositional breaks. There it is extremely important to recognize such erosionalor non depositional breaks in a vertical sequence".

KeteranganFASIES yg pada dasarnya berarti perbedaan ciri paleontologi dan batuan

pada umur yg sama, namun dalam praktek pengenalannya di lapangan sulitdikerjakan pada daerah tropis. Hal ini karena terbatasnya bentang singkapan.Oleh karena itu pemakaian Hukum Walther ini menolong kita dalam menafsirkanperubahan fasies yg bersifat lateral dan perubahan ciri paleontologi dan batuandalam susunan vertikal. Tetapi pengertian bahwa perubahan vertikaladalah sama dgn perubahan fasies adalah pengertian yg salah, karenasusunan vertikal menunjukkan urutan waktu yg berbeda (superposisi), yg tdksesuai dgn pengertian facies menurut GREESLY.

Time T2000 Time T0

Walthers Law

A Sand Nonmarine Member XShale ZB Sand

Units are defined by lithologyRock Units vary in space and timeBoundaries are subjective

Lithostratigraphy

Unconformity and correlative conformityDownlap surface and correlative conformity

Unit 1 Unit 2 Unit 3

Units based on physically observable stratal surfacesUnits vary in space onlyRepresent natural stratigraphic divisions (genetically related)

Chronostratigraphy

Alluvial PlainCoastal Plain

Foreshore/Upper ShorefaceShoreface/Shelf

Hypothetical Cross Section

Lithostratigraphy andChronostratigraphy

Chronostratigraphic Correlation

Lithostratigraphic Correlation

Correlation Styles

MAXIMUM FLOODINGSURFACE

BASINWARD SHIFT = SEQUENCEBOUNDARY

FLOODINGSURFACE

FLOODINGSURFACE

HypotheticalMicrofossilSignatureofCyclicDeposition

BiostratigraphyvsLithostratigraphyandChronostratigraphy

SPECIESDISTRIBUTIONCHARTREWORKEDMESOZOIC

NANNOS

# NEWFORAM/NANNOTOPS

ABUNDANCEUVIGERINAPEREGRINA

TERTIARYAGE

NANNOS

TOTALABUNDANCE

TOTALDIVERSITY I

NN

ER

NE

RT

IC

MID

DL

EN

ER

TIC

OU

TE

RN

ER

TIC

PALEOBATHYMETRYGAMMA

RAY

FLOODINGSURFACE

PARASEQUENCESCALE

SEQUENCESCALE

FLOODINGSURFACE

SEQUENCEBOUNDRARY

MFS

AFTERHAQ,1991MODIFIEDBY RFW7/02

ACMEZONE

TROUGH

TRUNCATE

PEAK

PEAK

* LAD S. ABIES

* FAD D. TAMALIS

DISTANCENOTE

DIACHRONOUS

CONDENSEDSECTIONMFS

GE

OT

IME

HST

SMW

HST

TST

LSW

BFF