GE0-3112GE0-3112 Sedimentary processes and products Sedimentary processes and products

Lecture 13. Sequence stratigraphyLecture 13. Sequence stratigraphy

Geoff CornerGeoff CornerDepartment of GeologyDepartment of GeologyUniversity of TromsøUniversity of Tromsø20062006

Literature:Literature:- Leeder 1999. Ch. 14. Changing sea level and - Leeder 1999. Ch. 14. Changing sea level and

sedimentary sequences.sedimentary sequences.- Reading & Levell 1996. Ch. 2. Controls on the - Reading & Levell 1996. Ch. 2. Controls on the

sedimentary rock record.sedimentary rock record.

ContentsContents

►StratigraphyStratigraphy►Why sequence stratigraphy?Why sequence stratigraphy?►ParasequencesParasequences►Systems tractsSystems tracts►Bounding surfacesBounding surfaces

Stratigraphy – the subdivision of Stratigraphy – the subdivision of rocks in time and spacerocks in time and space

► LithostratigraphyLithostratigraphy► BiostratigraphyBiostratigraphy► ChronostratigraphyChronostratigraphy► MagnetostratigraphyMagnetostratigraphy► ChemostratigraphyChemostratigraphy► MorphostratigraphyMorphostratigraphy► ClimatostratigraphyClimatostratigraphy► KinetostratigraphyKinetostratigraphy► TectonostratigraphyTectonostratigraphy► AllostratigraphyAllostratigraphy► Sequence stratigraphySequence stratigraphy

What is sequence What is sequence stratigraphy?stratigraphy?

►Packages of strata deposited during a Packages of strata deposited during a cycle of relative sea-level change cycle of relative sea-level change and/or changing sediment supply.and/or changing sediment supply.

►Genetic/interpretative approach:Genetic/interpretative approach: packages related to relative sea-level packages related to relative sea-level

and/or sediment supply.and/or sediment supply. packages bounded by chronostratigraphic packages bounded by chronostratigraphic

surfaces.surfaces.

Walker 1992

Why use sequence Why use sequence stratigraphy?stratigraphy?

► To To correlate and predictcorrelate and predict facies and facies and unconformities: division of the sedimentary unconformities: division of the sedimentary record into time-related genetic units.record into time-related genetic units.

► To To understand the distribution of sedimentary understand the distribution of sedimentary faciesfacies and unconformities in time and space. and unconformities in time and space.

► To To determine the amplitudes and rates of determine the amplitudes and rates of change of past relative sea-levelchange of past relative sea-level and, in turn, and, in turn, understand the cyclic and non-cyclic nature understand the cyclic and non-cyclic nature of tectonics and climate change (durations of of tectonics and climate change (durations of 10 ka - >50 Ma). 10 ka - >50 Ma).

What criteria do we use?What criteria do we use?

►Stacking patterns - indicate relative Stacking patterns - indicate relative sea-level change and or sediment sea-level change and or sediment supply.supply.

►Bounding surfacesBounding surfaces

Components of a sequenceComponents of a sequence

►Bounding surfacesBounding surfaces Sequence boundarySequence boundary Transgressive surfaceTransgressive surface Maximum flooding surfaceMaximum flooding surface

►Systems tractsSystems tracts LSTLST TSTTST HST/RSTHST/RST

►ParasequencesParasequences

Prothero & Schwab 1996

ParasequencesParasequences

► Parasequences: the small-scale Parasequences: the small-scale building blocks of systems building blocks of systems tracts and sequences.tracts and sequences.

► A parasequence represents a A parasequence represents a proximal to distal change in proximal to distal change in facies accumulated during a facies accumulated during a minor cycle in the balance minor cycle in the balance between sediment supply and between sediment supply and accomodation.accomodation.

► Each parasequence is bounded Each parasequence is bounded above by a above by a flooding surfaceflooding surface..

Flooding surfaces

Prothero & Schwab 1996

Stacking pattern of Stacking pattern of parasequencesparasequences

►ProgradationalProgradational►RetrogradationalRetrogradational►AggradationalAggradational

Prothero & Schwab 1996

SequencesSequences

► A sequence is composed of a succession of A sequence is composed of a succession of parasequence sets.parasequence sets.

► Each sequence represents one major cycle Each sequence represents one major cycle of change in the balance between of change in the balance between accomodation space and sediment.accomodation space and sediment.

► A sequence is subdivided into 3 or 4 A sequence is subdivided into 3 or 4 systems tractssystems tracts, each representing a specific , each representing a specific part of the cycle. part of the cycle.

Prothero & Schwab 1996

Systems tractsSystems tracts►ExxonExxon

LST, TST, HST (incl. RST)LST, TST, HST (incl. RST)

►AlternativeAlternative LST, TST, HST, RST (forced RST) LST, TST, HST, RST (forced RST)

Walker 1992

Lowstand STLowstand ST►Formed immediately following s.l. Formed immediately following s.l.

lowstand.lowstand.►Fluvial incision ceases; progradational to Fluvial incision ceases; progradational to

aggradational marine parasequences aggradational marine parasequences deposited.deposited.

►Active submarine fans below the shelf Active submarine fans below the shelf break.break.

Transgressive STTransgressive ST►Formed during s.l. rise.Formed during s.l. rise.►Accomodation space > sediment supply Accomodation space > sediment supply

retrogradational parasequences.retrogradational parasequences.►Base of TST is the transgressive surface Base of TST is the transgressive surface

(=ravinement erosional surface of shoreface).(=ravinement erosional surface of shoreface).►Top of TST is the maximum flooding surface.Top of TST is the maximum flooding surface.

Highstand STHighstand ST

►Formed during rising and high s.l.Formed during rising and high s.l.►Accomodation = sediment supply Accomodation = sediment supply

aggradational to progradational aggradational to progradational parasequences.parasequences.

Falling stage STFalling stage ST

►Formed during a s.l. fall (forced Formed during a s.l. fall (forced regression).regression).

►(Included in late HST in Exxon system).(Included in late HST in Exxon system).►May be associated with erosion.May be associated with erosion.

Walker 1992

Bounding discontinuitesBounding discontinuites► Sequence boundary (SB) - surface of subaerial erosion Sequence boundary (SB) - surface of subaerial erosion

and its correlative marine surface formed during sea-and its correlative marine surface formed during sea-level fall. Corresponds to base of incised valley in level fall. Corresponds to base of incised valley in proximal areas.proximal areas.

► Transgressive (ravinement) surface (TS) - transgressive Transgressive (ravinement) surface (TS) - transgressive surface of marine (shoreface) erosion.surface of marine (shoreface) erosion.

► Marine flooding surface - surface across which there is Marine flooding surface - surface across which there is evidence of an abrupt increase in water depth (may be evidence of an abrupt increase in water depth (may be used to separate parasequewnces).used to separate parasequewnces).

► Maximum flooding surface (MFS) - surface marking Maximum flooding surface (MFS) - surface marking regional transition from trangression to regression and regional transition from trangression to regression and most landward extent of the shoreline - commonly most landward extent of the shoreline - commonly marked by a condensed section (horizon).marked by a condensed section (horizon).

► Regressive surface of erosion. Regressive surface of erosion. (NB. may be removed by (NB. may be removed by subaerial erosion or subaerial erosion or transgressive surface).transgressive surface).

Prothero & Schwab 1996

Wheeler (time-distance) Wheeler (time-distance) diagramsdiagrams

Prothero & Schwab 1996

Sequence stratigraphy and Sequence stratigraphy and global sea-level cycles global sea-level cycles

► Various orders of global sea-level Various orders of global sea-level change distinguisged:change distinguisged: 1st order (200-400 m.y.), e.g. 1st order (200-400 m.y.), e.g.

lowstand during Permian Pangea. lowstand during Permian Pangea. Controlled by major tectonic Controlled by major tectonic cycles.cycles.

2nd order (10-100 m.y.), e.g. Mid-2nd order (10-100 m.y.), e.g. Mid-Cretaceous highstand. Controlled Cretaceous highstand. Controlled by changes in ocean-ridge by changes in ocean-ridge spreading rate. spreading rate.

► Global correlation of sequences Global correlation of sequences related to eustatic sea-level curves related to eustatic sea-level curves is difficult or impossible due to is difficult or impossible due to local variations in tectonics and local variations in tectonics and sediment supply. Sequence sediment supply. Sequence development is dependent on: 1) development is dependent on: 1) sea level, 2) tectonics, 3) sediment sea level, 2) tectonics, 3) sediment supply. supply.

Walker 1992

An example of sequence An example of sequence stratigraphic subdivision applied to stratigraphic subdivision applied to

fjord-valley fillsfjord-valley fills

Corner, in press

►Deglacial-postglacial transgressive-Deglacial-postglacial transgressive-regressive fillregressive fill

Glaciomarine deposition

A

Outlet glacier

Fjord glacier

Meltwater

B

Valley glacier

Meltwater

Glaciofluvialdelta

Valley glacier

CMeltwater

Marine deposition

Fluvialdelta

RiverD

Fluvial terracing

ERiver

Post

gla

cial

Degla

cial

Corner, in press

Deglacial-postglacial surface

I

IIIc

IVd

IIa

Df

Dv

PMaximum flooding surface

Regressive accretionary surface

Marine limit

I

I

IIIb

IIb

IIdIIc

IVc

Glacial trough

Cross section X - X’

X’X

A

BMarine limit

IVb

1

3 2

IIb

IIc

IIa

I

IVd

IId

Df

Dv

PIIIc

IVc

II

IIIIV

I

DTST (Df)

PRST (P)

DHST (Dv)

Time

Sea

leve

l

Regressive accretionary surface

PDvDf

Postglacial forced regressive (PRST)

Depositional episodes/sequence tracts

Deglacial (fjord glacier) transgressive (DTST)

Deglacial (valley glacier) highstand (DHST)

Bounding surfaces

Fluvial erosion surface

Deltaic erosion surface

Fluvial accretion surface

IV

III

Depositional elements

II

I

Fjord floor

Delta foreset

- Fluvial (P)IVd

Ice-contact (Df)

Glaciofluvial delta foreset (Df/Dv)

- Marine (P)IIc - Prodelta (P)IId

- Glaciomarine (Df/Dv)IIa/IIb

- Delta topset (P)IVc

IIIc - Delta foreset (P)

Terrace top

- Glaciofluvial delta topset (Df/Dv)IVa/IVb

IIIa/IIIb-

Transgressive systems tractTransgressive systems tract

Highstand systems tractHighstand systems tract

Forced-regressive systems tractForced-regressive systems tract

Corner, in press

►TSTTST►HSTHST►RSTRST

Corner, in press

Further readingFurther reading

► Coe (ed.) 2003. The Sedimentary Record of Sea-Coe (ed.) 2003. The Sedimentary Record of Sea-Level Change.Level Change. Well illustrated, modern treatment of sequence Well illustrated, modern treatment of sequence

stratigraphy and depositional successions.stratigraphy and depositional successions.► Emery & Myers 1996. Sequence stratigraphy.Emery & Myers 1996. Sequence stratigraphy.

Similar to above but more dated. Gives background to Similar to above but more dated. Gives background to nomenclature.nomenclature.

► E-learning journal. Sequence stratigraphy.E-learning journal. Sequence stratigraphy.► Walker 1992, in Walker & James (Ch. 1, 'Facies,

Facies Models and Modern Stratigraphic Concepts').► Corner, G.D. (in press, 2006). A transgressive-Corner, G.D. (in press, 2006). A transgressive-

regressive model of fjord-valley fill: stratigraphy, regressive model of fjord-valley fill: stratigraphy, facies and depositional controls. In Dalrymple, R.W., facies and depositional controls. In Dalrymple, R.W., Leckie, D. and Tillman, R.W. (eds.) ‘Incised-Valley Leckie, D. and Tillman, R.W. (eds.) ‘Incised-Valley Systems in Time and Space', SEPM Special Systems in Time and Space', SEPM Special Publication.Publication.