1

Week 3

Review of week 2o class project; basin spreadsheet

o tectonic setting of sedimentary basins

o Gulf of Suez Rift Basin (Alsharhan, 2003; Lindquist, 1998)

o additional Red Sea information

Topics for Week 3o tectonic classification systems for sedimentary basins

o giant fields, sedimentary basins and tectonic setting

o The Wilson Cycle (handout and Einsele, 2000, Ch 12)

o basin subsidence

http://csmres.jmu.edu/geollab/Fichter/Wilson/Wilson.html

2

Course Schedule and ContentClass Topic

Sept 14

Week 1

Introduction to Course and Material

Review and discussion of concepts

Sept 21

Week 2

Example of basin analysis: Gulf of Suez Rift Basin

Basins I: description of basins, plate tectonics, basin classification and

tectonic setting

Sept 28

Week 3

Basins II: basin classification (continued), basin models of subsidence

and sedimentation

Oct 5

Week 4

Basin Fill I: Stratigraphy and sedimentology; tools used, dating and

correlation

Oct 12

Week 5

Basin Fill II: Facies models, basin mapping; sequence s tratigraphy

Oct 19

Week 6

Basin Fill III: Sequence stratigraphy (continued), seismic stratigraphy

Oct 26

Week 7

Due Today: Selection of basin/petroleum system for main class

project

Basins III: Regional and global stratigraphic cycles

Nov 2

Week 8

Mid Term Exam (tentative)

Review selected basin example

Nov 9

Week 9

Petroleum System I: The petroleum system

Nov 16

Week 10

Student seminars

Petroleum System II: Field size distribution, play concepts

Nov 23

Week 11

Student seminars

Selected geologic topic: Carbonate models: basin fill and sequence

stratigraphy

Nov 30

Week 12

Student seminars

Carbonate models (continued): sequence stratigraphy, reservoir

development

Dec 7

Week 13

Student seminars

Basin modeling software demonstration

3

(after Miall, 2000)

small scale

large scale

Methods of Analysis

Global Stratigraphic Hierarchy

magnetic reversalsearthquake first

motions

deep seismicregional stratigraphy

biogeography

basin modelsbackstripping

geohistory analysis

radiometric datingpaleontology

sequence stratigraphy

seismic stratigraphyseismic facies

regional well datalithofacies analysis

paleocurrent analysis

sequence analysis

analysis of core or outcrop

sea floor spreading

plate positioneustatic sea level

plate and terrane interaction

plate margin typebasin generation

unconformity bounded stratigraphic sequences

depositional systems tracts

depositional systems

lithofacies assemblage

individual lithofacies

4

Basin Analysis: Gulf of Suez

The specific tools used in this basin analysiso Lithostratigraphic units

o stratigraphy: measured stratigraphic sections, subsurface cores, electric

logs

o age: electric logs tied to microfaunal and palynological studies of ditch

samples; pollen and spores used to date Paleozoic-L. Cret Nubian

sandstone

o plate tectonics

o eustatic sea level curves

o subsidence rates

o heat flow

o source rock maturity- TOC, Ro, Van Krevelen

What has not been included?

5

Gulf of Suez Rift Basin

Basin margins uplifted, non-marine sand wedge fills marine basin area

6

Conclusion: Gulf of Suez Rift Basin

Integrated picture covering differing geoscience

disciplines

Simple basin geohistory, basin fill, petroleum system

covered

Missing: seismic facies, sequence stratigraphy, cross

sections, well logs, subsidence model, quantitative

backstripping

some of these may be covered in reference material

7

Red Sea in Plate Tectonic Setting

8

Topographic map of Red Sea - Gulf of Aden Region

9

Gravity map of northern Red Sea

Filtered Bouguer gravity of the Northern Red Sea . The filtered

Bouguer accentuates regions of deep bathymetry and thinned

continental crust and major depocenters. Red dots represent the

locations of earthquakes.

10

Basin Classification: Summary

Reviewed common classification systems as presented

in Miall (2000), Einsele (2000) and Allen and Allen

(1990).

Sedimentary basins classified in terms of 3 criteria:o 1. the type of crust on which the basin rests (continental, oceanic,

transitional)

o 2. the position of the basin relative to plate margins (within plate or

margin of plate)

o 3. where the basin lies close to a plate margin, the type of plate

interaction occurring during sedimentation (divergent, convergent,

transform)

11

Einsele, 2000: Tectonic classification

12

Miall, 2000: Tectonic Classification

Divergent Margin Basins

Convergent Margin Basins

Transform and transcurrent-fault basins

Basins developed during continental collision and

suturing

Intraplate basins

(Miall, 2000, Table 9.1)

13

Classification of Bally and Snelson, 1980 Basins located on the rigid lithosphere, not

associated with the formation of megasutureso Related to formation of oceanic crust

Rifts

Oceanic transform fault associated basins

Oceanic abyssal plains

Atlantic type passive margins which straddle continental and oceanic crust

Cratonic basins located on pre-Mesozoic continental lithosphere

Perisutural basins on rigid lithosphere associated with formation of compressional megasutures

o deep sea trench adjacent to subduction margin

o foredeep and underlying platform sediments

o Chinese type: distal blockfaulting without associated subduction complex

Episutural basins located and mostly contained in compressional megasutures

o oceanic subduction; backarc basins; megashear systems

14(Mann et al, 2001)

World Oil:

Classification of

tectonic setting

of giant oil fields

15

Gulf of Mexico

The Gulf resulted from Middle Jurassic rifting between North America, Mexico, the Yucatan Peninsula and northern South America. Rifting resulted in passive margins flanking a small area of oceanic crust in the deep, central part of the basin. Structures on passive margins include growth faults, salt-withdrawal basins and salt domes that were produced by remobilization of Jurassic salt from sediment loading. For this reason, the area's 42 giants are classified as a passive margin fronting a major ocean basin.

16

Gulf of Mexico

17

Basin Category: Passive Margin

Passive Margin

18

Arabian Peninsula / Persian Gulf.

There are 151 giants in this region, Fig. 4. They are

concentrated in a large foreland basin formed during the Late

Cenozoic collision of the Arabian Peninsula with Eurasia.

Downward flexure of the Arabian Peninsula beneath the

Zagros Mountains of Iran / Iraq was caused by the

northeastward consumption of the Tethys Ocean at the

Zagros suture zone

However, other than minor tilting, large areas of the foreland

appear completely undisturbed by Zagros-related convergent

deformation, as manifested in the variety of giant-field

shapes. For that reason, formation of elongate giants parallel

to folds and thrusts in the Zagros Mountain and foreland

basin was classified as a continental collision margin, while

those giants to the southwest were counted as continental

rifts and overlying steer's head sag basins.

19

“Steers head” sag basin

20

Rocky Mountain Foreland

This foreland region, stretching from Mexico through

Canada and central Alaska, resulted from eastward

thrusting of a westward-thickening wedge of mostly

shallow-water, platform-deposited sedimentary rocks of

Precambrian through Jurassic age, Fig. 4. This occurred

during Early Cretaceous through Eocene time. Major

thrusts are oldest in the west and become progressively

younger to the east. Dating of synorogenic, clastic

deposits shows a complex pattern of thrust evolution.

Giants are largely concentrated in complex basins of the

Utah-Wyoming area and in western Canada's

asymmetrical foreland basin. The setting for these 18

giants is classified as a continental collision margin.

21

Wilson Cycle

simple picture of opening and closing of ocean basins

important for implications regarding differentiation of

rock types to form lighter continental crust

22

Continuum: Sags to Passive Margins

(Allen and Allen, 1990, Fig 3.31)

23

The “Wilson Cycle”

24

Wilson Cycle

B

C

D

E

F

Summary of basins formed,

tectonic setting, and

depositional

environments/sedimentation

during typical Wilson Cycle

(Einsele, 2000, Table 12.1)

25

The circular Wilson Cycle

26

Basin Models, Mechanics of Subsidence

Topics:o Basin models

o Concept of Isostasy

o Subsidence

27

Basin Models, Mechanics of Subsidence, Cycles

We use “basin models” to put together a picture of how the basin

formed and was filled with sediment

We need information about the “container”:o crustal thickness

o crust mechanical properties (Poisson ratio, Young’s modulus, crust strength)

o heat flow

o isostatic response

We need information about the material filling the container: o Stratigraphy, depositional systems

o Basin and crustal geometry

o Porosity-depth relationships

o Paleobathymetry

o Sea-level change

28

Basin Model for Each Basin Type

In describing the origin and history of a sedimentary basin we use these

components:

the plate tectonic processes generating the basin convergent, divergent, shear

the mechanism of crustal subsidence

the structural geology of the basin

the typical evolutionary development of the depositional system

The two most important basin models: extensional basins (divergence: rifting, passive margin)

supracrustal loading (convergence, compression: foreland basins)

29

Subsidence Mechanisms

crustal thinning as a result of extensional plate

movements

supracrustal loading, by magmatism and stacking of

thrust sheets at convergent boundaries

mantle-lithosphere thickening during cooling or

underthrusting

flow of the asthenosphere by convection currents

sedimentary and volcanic loading

Need info on lithospheric mechanics (Allen and Allen,

1990, chapter 2)

30

Crustal Subsidence

Subsidence is controlled by o isostasy

o thermal contraction of the lithosphere

o flexural loading

Elevation of the top of the crust is controlled by the thickness and densities of several layers

o sea water

o sediments

o solid crust (igneus and metamorphic

o solid upper mantle (mantle lithosphere

o these rest on viscous asthenosphere

Load: sediment, change in density, stacking of thrust sheets

31

Simple Concept: Isostasy

32

Layer Thickness Controlling Subsidence

whw+shs +chc +mhm +aha=constant

where the layers of thickness h are:

w: sea water

s: sediment

c: crust

m: mantle lithosphere

a: mantle asthenosphere

surface of constant pressure

a a

33

Concepts in Modeling Isostasy

Asthenosphere: horizontal surfaces of constant

pressure are assumed

The mass/unit rock volume of overlying rock volume

must be the same everywhere

Behavior of Lithosphere:o no lateral strength of lithosphere

o lithosphere has some strength (elastic, viscoelastic)

34

Airy model

Lithosphere has no lateral strengtho an applied load of sediment and water is fuly compensated by local

displacement (vertical faults)

o interconnected fault slices; no transmission of load between fault

blocks

35

Airy Model

36

Pratt Model of Isostasy

37

Physical Concepts: Airy vs Pratt Isostasy

Airy

Pratt

38

Flexural Model

Effect of load is spread beyond the points or area to

which it is applied

Lithosphere may behave as:o plastic plate model: return to original position

o viscoelastic plate model:

o these are temperature dependent

39

Thermal Uplift and Subsidence

40

Supracrustal Loading Model

41

Foreland Basin Model (WCSB analogy)