biostrat dan kronostrat

8/10/2019 Biostrat Dan Kronostrat

1/25

OTHER TYPE OF STRATIGRAPHIC UNITS

BIOSTRATIGRAPHY & CHRONOSTRATIGRAPHY


2/25


3/25

Biostratigrafi sebagai Unit Stratigrafi Dalam

Sandi Stratigrafi Indonesia (SSI)

Pembagian biostratigrafi dimaksudkan untuk menggolongkan

lapisanlapisan di bumi secara bersistem menjadi satuan

satuan bernama berdasarkan kandungan dan penyebaran fosil.

Satuan biostratigrafi ialah tubuh lapisan batuan yangdipersatukan berdasar kandungan fosil atau ciriciri

paleontologi sebagai sendi pembeda terhadap tubuh batuan

sekitarnya.

Urutan tingkat satuan biostratigrafi resmi, dari besar kecil :Super-Zona, Zona, SubZona, dan Zonula.

Zona ialah satuan dasar biostratigrafi, yang dicirikan oleh satu

takson fosil atau lebih.


4/25

Berdasarkan ciri satuan paleontologi, satuan biostratigrafi

dibedakan menjadi beberapa zona :

a. Zona Kumpulan

b. Zona Kisaran

c. Zona Puncak

d. Zona Selang

e. Zona Rombakan

f. Zona Padat


5/25

ZONA KISARAN

ZONA SELANG

ZONA PADAT

ZONA KUMPULAN


6/25

WHY STUDY BIOSTRATIGRAPHY?

Dating of strata and geological events

- Definition of the geological time scale

- Sedimentary rocks are not normally datable by radiometric

means

Correlation of biological and environmental events between

regions

Framework for paleobiogeographic analysis


7/25


8/25

Applied biostratigraphy analysis are based on a relatively small

number of fossil group, all with one or more features in common.

These are small size, abundance, species diversity, widespread

distribution as well as the potential for fossilisation.


9/25

FACTORS CONTROLLING DISTRIBUTION OF

ORGANISM

Environmental factors

salinity, temperature, carbonate content

Biological factors

association, simbiosis

Time of first and last appearance

FAD and LAD


10/25

First appearance datum (FAD)

- In principletime of evolutionary origin of the taxon

- In practicetime it became abundant and widespread

enough to be preserved and discovered as a fossil

Last appearance datum (LAD)

- In principletime of extinction of a taxon

- In practicetime when it fell to numbers too low to bepreserved and discovered as a fossil and populations did

not recover


11/25

IDEAL SPECIES FOR BIOSTRATIGRAPHIC

CORRELATION

Ideal Index Fossil

- Abundant

- Geographically widespread

- Relatively short range in time (rapid evolutionary turnover)

- Wide range of environments

- Morphologically distinctive

Problemabundant and widespread taxa are often (but notalways) resistant to extinctiontherefore, long - ranging


12/25

BIOSTRATIGRAPHIC METHODOLOGY

Collection of successive samples from carefully

measured stratigraphic sections within a region

Systematic identification of taxa (mainly species) in

each sample

Plotting of taxon ranges against stratigraphic sections

Division of range data into zones based on regionally

consistent biostratigraphic events (FAD and LAD)


13/25

BIOZONATION


14/25

BIOSTRATIGRAPHIC CORRELATION

Process of establishing age relationships between two

regions on the basis of their faunal/floral successions

(zonations)

Events that can be shown to have occured at the sametime in two or more regionsisochronous

Events that can be shown to have occured at different

times in different regionsdiachronous Problemdistinguishing isochronous from diachronous

biostratigraphic events


15/25

DIACHRONOUS BIOSTRATIGRAPHIC EVENTS

Reasons:

Slow rate of dispersal from time of origin

Temporary barriers to dispersal Local extinction

Locally incomplete stratigraphic successions

Locally incomplete sampling

Localregional environmental (facies) changes


16/25


17/25


18/25

KRONOSTRATIGRAFI

Penggolongan lapisan batuan secara bersistem menjadi satuan

bernama berdasarkan interval waktu geologi.

interval waktu geologi ini dapat ditentukan berdasarkangeokronologi atau metode lain yang menunjukkan kesamaan

waktu.

pembagian ini merupakan kerangka untuk menyusun urutankejadian geologi secara lokal, regional, dan global.


19/25

TINGKATTINGKAT SATUAN

KRONOSTRATIGRAFI

Urutan tingkat satuan kronostratigrafi resmi, masing

masing dari besar sampai kecil ialah: Eonotem,

Eratem, Sistem, Seri, Jenjang.

Bidang lapisan pada dasarnya adalah bidangkesamaan waktu, oleh karena itu satu lapisan yang

menerus, cirinya mudah dikenal serta mempunyai

pelamparan luas, dapat merupakan penunjuk

kesamaan waktu dan dinamakan lapisan pandu.

Selang antara dua lapisan pandu disebut selang

antara.


20/25

PEMBAGIAN

KRONOSTRATIGRAFI


21/25

UNITS OF THE GEOLOGIC TIME SCALE

TimeRock Unitsdefined

mainly on biostratigraphic criteria

1. Erathem

2. System

3. Series

4. Stage

5. Zone

(consist of rocks and fossils)

Time Unitscalibrated by radiometric

dating

1. Era

2. Period

3. Epoch

4. Age

5. Chron

(consists of time intervalsyears

before present)


22/25

UNITS OF GEOLOGIC TIME SCALE Determined over hundreds of years of emperical observation of

successions of fossil faunas and floras that are repeated over

wide regionsprinciple of faunal succession

Whole time scale is a composite of observations from many

successions in many parts of the world.


23/25

DEFINITION OF THE TIME SCALE

Each timerock units base is defined by a particular

stratigraphic level at one type section some place in the world

called Global Stratotype Section and Point (GSSP)

That stratigraphic level is marked by first or last appearance ofone or more indextaxa base of a zone

Other sedimentary rocks of that age determined by

biostratigraphic correlation with that type section

Many timerock units are still not formally defined.


24/25

AGE CALIBRATION OF THE GEOLOGICAL

TIME UNITS

Achieved by radiometric dating of volcanic rocks that are

associated (usually interbedded) with fossiliferous sedimentary

rocks.

Other igneous and metamorphic rocks radiometrically dated andrelated to timerock units using establish calibration.

Age may also be inferred by field relationships (position in

succession or crosscutting of units of known ages).


25/25

MAGNETOSTRATIGRAPHY

SEISMIC STRATIGRAPHY

VOLCANOSTRATIGRAPHY LITODEMIC

biostrat dan kronostrat

Documents