7-8 PRINSIP DASAR STRATIGRAFI - Nicolas STENO - William SMITH

Stratum  Strati : tingkat(an) Grafi / grafik : penggambaran Makna Stratigrafi secara harfiah : “ penggambaran tingkat(an) “ Dalam arti yang luas (makna dalam geologi) : “ Penggambaran hubungan (tingkatan) antar (lapisan) batuan vertikal maupun lateral dalam ruang dan waktu “

STENO’S PRINCIPLES (1669) Superposition of Strata Original Lateral Continuity of Strata Original Horizontality of Strata Collorary: Vertical Accumulation of Strata

LAW OF SUPERPOSITION (STENO, 1669) Modified statement: Law of Superposition: The youngest strata are at top in an undisturbed sequence (Anthony, 1955, p. 83

W D C Litostratigrafi B A R A > B > C > D

CONCEPT OF STRATA Strata, stratum, beds, layer Stratification/ bedding/ layering Strata as a basic concept in geology Concept of Strata is important in understanding correlation and time relationships Concept of Strata is important in understanding of reservoir rocks and seals

IDENTIFICATION OF STRATA AND STRATIFICATION Vertical change in lithology Characteristics vertical variations in lithology such as : Grain size, Color, Mineralogy, etc Some degree of lateral continuity Vertical changes and variations in lithology varies from extremely thin, laminae, to very thick

THE NATURE OF VERTICAL BOUNDARIES OF BEDS GRADUAL OR TRANSITIONAL ABRUPT OF SHARP EROSIONAL TRUNCATION DISCONTINUITIES: gaps or breaks in deposition are quite common in stratal sequences.

CAUSES OF STRATIFICATION Strata and stratification is caused by changes in the depositional regime, mechanical energy, chemical of biological Changes are caused by climate/weather, sea level change or tectonics/sediment supply Changes may take place daily, annually or even in millions of years

BED AS BASIC LITHOLOGIC UNIT Generally a uniform unit of lithology Thickness varies from laminae to extremely thick Vertical boundaries of strata are considered depositional interface Lithology of a bed may change laterally but in an extremely gradual way

THE TIME SIGNIFICANCE OF STRATA Steno’s Law of Superposition implies that stratal or depositional surfaces are isochronous time surfaces A stratum or a packet of strata represents of time period of deposition or contemporaneous deposition Seismic reflection surfaces are stratal surfaces and being former bedding surfaces they are geologic time surfaces and are essentially synchronous (Vail et al, 1977)

STRATA IDENTIFIED BY FOSSILS (SMITH, 1816) Modified Statement: Strata can be distinguished by their characteristic fossils (Woodford, 1935, op.cit, p.5-6; Schenk, 1940, p. 1754-1755)

LAW OF FAUNAL SUCCESSION (ABBE GIRAUD-SOULAVIE, 1777) Statement of principle: Fossil differs according to their geologic ages (stratigraphic position); fossils in lower formations are unlike those in higher beds. Fossil floras and faunas succeed one another in a definite and determinable order (Anthony, 1955, p.89)

LAW OF FAUNAL SUCCESSION In a succession of strata units can be identified by the specific assemblage of the fauna of its fossil content top The fauna of the fossil content resembles closer to the modern fauna as one goes toward the top A geologic time scale can be established based on the faunal succession.

Paleontologi W Ψ Biostratigrafi β Evolusi Φ R Φ > β > Ψ

W D C Litostratigrafi B A R A > B > C > D

Φ > β > Ψ Paleontologi W Ψ Biostratigrafi β Evolusi Φ R A > B > C > D Φ > β > Ψ

1 2 A > B > C > D W D Ψ F Ψ C β B Φ E Φ A Φ R E (Φ) > F (Ψ) W 1 2 D Ψ F Ψ Lito vs Biostratigrafi C β B Φ E Φ A Φ R BAGAIMANA GABUNGAN/KORELASI 1 DAN 2 ??

1 2 A > B > C > D W D Ψ F Ψ C β B Φ E Φ A Φ R E (Φ) > F (Ψ) W 1 2 D Ψ F Ψ Lito vs Biostratigrafi C β B Φ E Φ A Φ R (A>B) = E (Φ) > { C (β) > D (Ψ) } =F [(- β) > Ψ]

Paleontologi W Biostratigrafi Litostratigrafi Evolusi R

HORIZONTAL LATERAL CONTINUITY Steno, 1669) Modified statement: Law of Original Continuity: The original continuity of water-laid sedimentary strata is terminated only by pinching out against the basin of deposition, at the time of their deposition. (Anthony, loc.op.cit, p.83)

STRATAL CONTINUITY AND CORRELATION Steno’s Law of Stratal Continuity established that strata or bed can be traced laterally indefinitely(?) William Smith’s Law established that a bed (ls, ss, sh etc) can be identified in different sections by its fossil content Correlation by fossil Correlation is essentially lateral tracing of beds  Stratal Continuity = time continuity As bedding planes or stratal interface are isochronous, correlation is interpreted as establishing time relationships of strata

LATERAL CONTINUITY VS LATERAL TERMINATION Steno’s Law of Lateral Contintuity of strata: Strata continues laterally except at the edge of the depositional basin or being truncated Sequence Stratigraphy Lateral Termination of Strata: All strata terminates laterally by lapping out towards the base as well towards the top of the sequence boundary.

LATERAL TERMINATION OF STRATA Base-lapping Down-lapping towards the open sea On-lapping toward land Top-lapping Off-lapping

LATERAL TERMINATION OF STRATA

STRATAL PATTERN OF LATERAL ACCUMULATION

ORIGINAL HORIZONTALITY (STENO, 1669) Statement of Principle: Dipping beds were once horizontal (Woodford, 1935, p.3) Modified Statement: Law of horizontality: Sedimentary strata are laid down nearly horizontally and essentially parallel to the surface upon which they accumulate. (Anthony, loc op cit., p.83)

GREZZLYS’ CONCEPT OF FACIES

CLINOFORM DEPOSITION

VERTICAL VS LATERAL ACCUMULATION OF STRATA

STRATAL PATTERN OF PROGRADATION, RETROGRADATION AND AGRADATION

TUGAS 2 BAGAIMANA PANDANGAN SAINS TERHADAP PENCIPTAAN, DAN APAKAH PENCIPTAAN ITU SAINS ?

TERIMA KASIH

ELCAPITAN FACIES CHANGES