Higher-Resolution Sequence Stratigraphy

Higher-Resolution Sequence Stratigraphy

Van Wagoner, J.C., Mitchum, R.M., Campion, K.M. and V.D. Rahmanian, 1990 , Siliciclastic Sequence Stratigraphy in Well Logs, Cores and Outcrops. AAPG Methods in Exploration Series, No. 7. 55pp.

Highstand Systems Tract: Aggradational to Prograda- tional Parasequence Set

Transgressive Systems Tract: Retrogradational Para- sequence Set Lowstand Systems Tract, Low-

stand Wedge: Progradational Parasequence Set

• Higher resolution • Incorporated outcrop, logs, core into seismic model • Documentation of stratal stacking patterns within each systems tract

Starting point: 1990 Exxon Model, Van Wagoner et al.

WHAT IS A PARASEQUENCE??

In outcrops of marginal marine depositional environments, observe cycles in stratification.

Sandstone

Mudstone

Sandstone

Mudstone

Sandstone

When look more closely these “cycles” are repetitive, shoaling-upwards facies assemblages capped by a flooding surface which juxtaposes deeper water facies on top of the shallowest beds of the underlying succession. This is a “parasequence”.

Flooding surface

Not “cycles” because assymmetric. Gradual shoaling, abrupt deepening.

Non-adjacent facies. Walther’s law does not apply across a FS

1 PARA- SEQUENCE ON LOG

Bhattacharya, J., 2007, Sequence Stratigraphy: History, Theory and Applications. AAPG SW Section Short Course, Dec. 3 & 7, Abilene / Ft. Worth.

Definition of a parasequence: A relatively conformable succession of genetically related beds or bedsets bounded by marine-flooding surfaces or their correlative surfaces.

Definition of a marine flooding surface: A surface separating younger from older strata across which there is evidence of an abrupt increase in water depth. This deepening may be accompanied by minor submarine erosion or a hiatus, but NOT by subaerial erosion or a basinward shift in facies (these are indicators of a sequence boundary). The flooding surface has a correlative surface in the coastal plain and on the shelf.

Characteristics of a parasequence (as per 1990): Thickness: 10-100’ Lateral extent: 10 – 1000 sq mi Time for formation: 100 - 10,000yr

Driver?

Some local (autocyclic) but many are regional

“Clastic Hierarchies” Christopher G. St. C. Kendall

Coast Types

Dalrymple et al, 1992

Tidal range <2

WAVE TIDE

FLUVIAL

(Deltas)

Tidal range >4m

Because parasequences are most recognizable in nearshore marine settings, geologists have to be familiar with the typical facies seen in each coastal depositional environment.

Barrier Island (foreshore)

Coastal Texas – Freeport to Western Galveston Bay

Lagoon

Coastal Plain

Upper Shoreface

Lower Shoreface

Offshore

Meandering River (Brazos)

Wave-dominated delta

Marsh

15mi

Modern wave-dominated shoreline

Onshore – offshore facies transect



Lagoon

Coastal Plain

Upper Shoreface

Lower Shoreface

Offshore



Marsh

15mi



http://www.lovethesepics.com/2015/08/bizarre-yet-beautiful-badlands-hidden-gems-in-new-mexicos-wilderness-52-pics/

Back-beach marsh & river channels, coal beds

Cretaceous Fruitland Fm., Bisti Wilderness Area, NM

Barrier Island (Foreshore)


Lagoon

Coastal Plain

Upper Shoreface

Lower Shoreface

Offshore



Marsh

15mi



(Wave swash zone.) Foreshore planar beds

http://www.jeangerard-sed-trace.com/administration/popupAgrandi ssementPhoto.php?id=17&rub=Sedimentary%20Structures beds

Upper shoreface swaley cross-beds

(Above fairweather wave base.) Upper shoreface trough cross-beds

http://www.slideshare.net/wwlittle/principles-of-sequence- stratigraphy-lgc-field-course-in-the-book-cliffs-ut

http://www.jeangerard-sed-trace.com/administration/popupAgrandi





http://www.slideshare.net/wwlittle/principles-of-sequence-








Lagoon

Coastal Plain

Upper Shoreface

Lower Shoreface

Offshore



Marsh

15mi



(Storm wave base.) Lower shoreface, Hummocky x-bedding, Cretaceous, San Juan Basin, NM



Lagoon

Coastal Plain

Upper Shoreface

Lower Shoreface

Offshore



Marsh

15mi


Onshore – offshore facies transect Offshore mudstones,

Cretaceous, San Juan Basin, NM

Parasequence characteristics of a wave-dominated shoreline

(Hummocky x-strata)

Coal

University of Georgia Geology Dept. website

Parasequence characteristics of a wave-dominated shoreline


Parasequences in outcrop, well log and core, Blackhawk Fm., Spring Cyn. Mbr., Book Cliffs


Lateral facies relationships and well log response for a beach parasequence

Observing shoaling-upwards facies vertically means that the entire shoreline is shifting laterally. It’s building out. The parasequence is a single episode of progradation, or accommodation space being filled faster than it is created. This switches at the flooding surface when there is an abrupt increase in accommodation space (relative sea level). Recognizing parasequences in cores or well logs is a valuable tool because now can predict facies away from well in updip and downdip directions.

Downdip Updip


Lateral facies relationships and well log response for a beach parasequence

Some parasequences are autocyclic (delta lobe switching, local subsidence events), others are regional. The flooding surfaces on the tops of regional parasequences are the best marker beds stratigraphers have for correlating sandy units in nearshore sedimentary deposits.


Exercise 2A: Identify parasequence boundaries in a measured section

from the Book Cliffs.

Blackhawk Fm. (interpreted as a wave-dominated shoreline)

http://www.sepmstrata.org/ page.aspx?&pageid=749&1

http://www.sepmstrata.org/

Parasequences Exercise 2A Solution

SEPM Strata > Exercises > Outcrop Sequence Stratigraphy > Clastics > Introduction to Sequence Stratigraphy of Clastic Sections, Book Cliffs, Utah.

http://www.sepmstrata.org/page.aspx?&pageid=749&1


Coast Types


Tidal range <2

WAVE TIDE

FLUVIAL

(Deltas)

Tidal range >4m


http://intheplaygroundofgiants.com/geology-of-the-grand-canyon-region/the-geology-of-sedimentary-rocks/

Delta Front

Panther Tongue in Gentile Wash, (Book Cliffs, UT). Falling Stage Systems Tract, River-dominated Delta

DELTA FRONT: thinly interbedded sandstone & mudstone

http://pt.slideshare.net/wwlittle/lgc-field-course-in-the-book-cliffs-ut-presentation-2a-gentile-wash-panther-tongue

Ophiomorpha burrows

Delta Front


Delta Front

http://myweb.facstaff.wwu.edu/talbot/cdgeol/Structure/SedStruct/Sed_struct.html

Distal delta front turbidites (graded beds)

Scours into underlying fines by a density flow. Scours into underlying fines by a dragged object.

Sand deposited on poorly- consolidated mud. Sinks down.

Sand with high water content de-waters.

Panther Tongue in Gentile Wash, (Book Cliffs, UT). Falling Stage Systems Tract, River-dominated Delta

Delta front


Delta front

High sediment delivery (fines) by a current.


And.. Not much bioturbation.

http://intheplaygroundofgiants.com/geology-of-the-grand-canyon-region/the-geology-of-sedimentary-rocks/

Distributary Mouth Bars

Distributary Mouth Bars



Onshore Offshore Facies change from sandstone to mudstone

Parasequences in the Panther Tongue, Book Cliffs, Utah. Delta front depositional environment

Delta-front turbidites

GR Log, 120’ Core


Flooding surface

Ove

rall

Del

ta F

ron

t Sa

nd

s U

pw

ard

s

San

ds

up

Parasequences

Parasequence characteristics of a deltaic environment



Onshore Offshore Facies change from sandstone to mudstone

Parasequences in the Panther Tongue, Book Cliffs, Utah. Delta front depositional environment


GR Log, 120’ Core


Flooding surface

Ove

rall

Del

ta F

ron

t Sa

nd

s U

pw

ard

s

San

ds

up

(Don’t see PS breakout in GR curve!)

Parasequences 10’s of feet thick

Examples of beach and deltaic parasequences in logs from Jurassic to Miocene in age.



Coast Types


Tidal range <2

WAVE TIDE

FLUVIAL

(Deltas)

Tidal range >4m


Tidal deposits occur in estuaries. The estuaries may occupy former incised valleys. The incised valleys were cut during sequence boundary formation. During the beginning of sea level rise, they backfill with tidal deposits.

Tidal Facies Model

http://aapgbull.geoscienceworld.org/content/94/8/1267/F10

http://www.andeangeology.cl/index.php/revista1/article/view/V42n1-a06/html

Tidal channel: • Sigmoidal cross-bedding, • one dominant direction • mud drapes • sometimes ripples climb up bar form in opposing direction

Subtidal mud flats

Tidal channels

Supra- or Inter-tidal mud flats Tocito Fm., San Juan Basin, NM

Tidal channel: • herringbone cross-bedding, • both ebb and flood tidal currents

Ripples in modern intertidal mud flat.

http://acad.depauw.edu/~tcope/SedStruct.html

Intertidal flat, rooted mudstone, Tocito Fm.

Intertidal flat, flaser bedding

Parasequence from a tide- dominated shoreline. (University of Georgia figure)

http://strata.uga.edu/sequence/parasequences.html

1) Progradation

2) Flooding

3) Progradation


How do parasequences develop?

Rate of deposition

Rate of accommodation

Parasequence stacking patterns

Rate of deposition


Rate of deposition


= 1

<1

>1

Even as relative sea level is rising, backstepping of the shoreline happens as a series of progradational pulses that loose ground in each step.

Even during an overall regression, progradation of the shoreline happens as a series of pulses, punctuated by abrupt floods, that step a little farther seaward each time.

Accommodation and sediment supply are balanced overall, but there are still progradational pulses and abrupt floods happening. They just keep returning the shoreline to the same place.


Parasequences Exercise 2B: Identify parasequences in measured sections and correlate them.

Book Cliffs

Ex. 2A

Parasequences Exercise 2B: Identify parasequences in measured sections and correlate them.

Updip Downdip Exercise 2A

SEPM Strata > Exercises > Outcrop Sequence Stratigraphy > Clastics > Introduction to Sequence Stratigraphy of Clastic Sections, Book Cliffs, Utah. http://www.sepmstrata.org/page.aspx?&pageid=749&1

Parasequences Exercise 2B Solution

http://www.sepmstrata.org/page.aspx?&pageid=749&1

Examples of well logs displaying progradational, retrogradational and aggradational stacking patterns.

Progradational parasequence set, Blackhawk Fm., Spring Cyn. Mbr., Book Cliffs, UT (Wave-dominated delta)

Well log with continuous core

Measured Sections Measured Sections

Coastal plain SS, mdstn, coal

Foreshore & Upper Shoreface SS



Lwr shoreface & delta front





Lwr shoreface & delta front Shelf mudstone

Shelf mudstone

Shelf mudstone

Shelf mudstone

Correlation styles in progradational sandstones

Chronostratigraphic Correlation (correct)

Datum on parasequence set boundary

Lithostratigrphic Correlation (incorrect)

Datum on top sand

• sand continuity exaggerated • genetically different sandstones are linked (each with potentially different fluid contacts) • lowermost shallow marine ss are interpreted to change facies updip into downdip marine mudstones.

Van Wagoner, J.C., Mitchum, R.M., Campion, K.M. and V.D. Rahmanian, 1990, Siliciclastic Sequence Stratigraphy in Well Logs, Cores and Outcrops. AAPG Methods in Exploration Series, No. 7. 55pp.

Retrogradational parasequence set in well logs, Almond SS, Late Cretaceous age, Washakie Basin, WY



Shallow marine SS

Shallow marine SS

Shelf mudstone Shelf mudstone

Notice no parasequences identified in coastal plain deposits.


Correlation styles in retrogradational sandstones

Chronostratigraphic Correlation (correct)

Datum on parasequence set boundary

• each ss reservoir is isolated above and below in marine mudstones and laterally by coastal plain mudstones. • probably have separate fluid contacts.

Lithostratigrphic Correlation (incorrect)

Datum on top sand

• ss continuity exaggerated • interpreted to have same fluid contact • Problem? Add a “production fault”!


Aggradational parasequence set, Cotton Valley Group, Schuler Fm., east TX


Beware! Parasequences can form from autocyclic processes too. Look for regional correlations.


Parasequence Stacking Patterns within Systems Tracts

HST


Higher

Lower

Eustatic Sea Level

Time

Highstand Systems Tract

1 Aggradation

2 Progradation

Neal & Abreu, 2009

Transgressive Systems Tract Higher

Lower

Eustatic Sea Level

Time

Retrogradation

Neal & Abreu, 2009

Higher

Lower

Eustatic Sea Level

Time

Lowstand Wedge Systems Tract

1 Progradation

2 Aggradation

Neal & Abreu, 2009

California San Joaquin Basin Exercise

Part 1, Well Log stacking patterns.

1. Identify parasequence tops (flooding surfaces)

2. Identify progradational aggradational and retrogradational parasequence sets.

3. Identify systems tracts from the PS Set pattern.

4. Identify any sequence boundaries, transgressive surfacse and maximum flooding surfaces.

SEPM Strata website > Exercises > San Joaquin

Refer to these figures of well log response to parasequence stacking patterns.








Pro- gradational

Pro- gradational

Aggradational

Retro- gradational








Pro- gradational

Pro- gradational

Aggradational

Retro- gradational

LST

TST

HST

HST







4. Identify any sequence boundaries, transgressive surfaces and maximum flooding surfaces.

Pro- gradational

Pro- gradational

Aggradational

Retro- gradational

LST

TST

HST

HST

Sequence boundary

Transgressive Surface

Maximum Flooding Surface

Save this for San Joaquin Seismic Exercise


Fluvial Sequence Stratigraphy

Incised Valley Fill on Well Logs – Best Reservoirs on Shelves

Look more closely at HST stacking on logs. Find valley fills. Van Wagoner, J.C., Mitchum, R.M., Campion, K.M. and V.D. Rahmanian,

1990, Siliciclastic Sequence Stratigraphy in Well Logs, Cores and Outcrops. AAPG Methods in Exploration Series, No. 7. 55pp.

Why do rivers incise when sea level falls?


SB

FS

FS

FS

HST

Strike Section Correlation

TS TST

On shelf, if no incised valleys, the sequence boundary is identified by: • Evidence of exposure (rooting, paleosol development, mineralization) • A basinward shift in facies (doesn’t conform to Walther’s Law). Like foreshore on lower shoreface.

Rooting, Bhattacharya, 2007

FS

FS

FS

TS

HST

TST

SB

Middle Miocene of South-Central Louisiana

zoom

Fluvial Incised Valleys


SB 1

SB 2

SB 3

There are three sequence boundaries in this section identified where rivers have incised into marine parasequences. Identify the systems tracts between the SB’s using the parasequence stacking patterns inferred from the log responses.


Refer to these figures of well log response to parasequence stacking patterns.


Distal marine parasequences Incised Valley with fluvial fill

HST

SB

LST

HST

TST

TST TS

TS

MFS

MFS

SB

LST

SB

LST

HST

Fluvial Incised Valleys - Solution

How far updip can you carry sequence stratigraphic surfaces?

Beyond the nearshore marine setting, can parasequences and systems tracts be identified?


Common Models


How far updip can you carry sequence stratigraphic surfaces?

Coastal sequence stratigraphic surfaces shouldn’t carry above the first lake. Rivers above that are graded to the lake and not to the ocean.

Higher-Resolution Sequence Stratigraphy

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