Sedimentary Basins

1
Sedimentary Basins

• Plate Tectonics, Sedimentation, and the Coherent
  Logic for the Analysis of Sedimentary Basins

2
Sedimentary Basins

• Topographic/ Bathymetric versus
• Geological
• Sites of Thick sediment accumulation
• (1000's of meters)
• over Long Time Periods
• (Ma-- mega-annum millions of years).

3
Plate Tectonics and Sedimentary Basin Types

SB Suture Belt RMP Rifted margin prism SC
Subduction complex FTB Fold and thrust belt RA
Remnant arc
4
Controls on Basin Formation

• Accommodation Space,
• Space available for the accumulation of sediment
• T E S W
• Ttectonic subsidence
• E Eustatic sea level rise
• SRate of sedimentation
• Wincrease in water depth
• Source of Sediment
• Topographic Controls
• Climate/Vegetation Controls
• Oceanographic Controls (Chemical/Biochemical
  Conditions)

5
Plate Tectonics Mechanisms and Sedimentary Basins

• Lithosphere
• Brittle, outer crustal layer deformation by
  fracture (faults)
• Asthenosphere
• Plastic lower layer deformation by flow
• Horizontal Plate Motions (1000's of km)
  translated to Vertical Displacements (1-10's of
  km)
• Sedimentary Basins
• Negative Crustal Topography
• Sediment Source Areas
• Positive Crustal Topography

6
Mechanisms for the Creation of Crustal Topography

• Isostatic Response
• Compositional (Stretching) Isostacy
• Thermal (Heating/Cooling) Isostacy
• Crustal Load (Tectonic/Sediment) Isostacy
• Tectonic/ Mechanical Processes
• Not isostatically compensated

7
Isostatic Response

• Compositional Isostacy

Archimedes principle Mass of a floating object
mass of the fluid displaced
8
Isostatic Response

• Thermal Isostacy
• Global Empirical Age-Depth Curve for Ocean Crust
• Subsidence _at_1-10cm/1000yrs
• Hotspot Uplift
• 20cm/1000yrs

9
Isostatic Response

• Sediment Loading Isostacy
• Viscous flow in the asthenosphere accommodates
  redistribution of crustal load
• Sediment loading

(A) 300m of 2.3 gm/cc sed accumulates due to
initial driving force subsidence (B) Sed load
displaces a thickness (T) of 3.3 gm/cc
mantle Pressure force 2.3gm/cc 300m
69,000gm/cm2 (C) 69,000gm/cm2 how
much 3.3gm/cc mantle? 3.3gm/cc T 69,000gm/cm2
(T thickness) T 210m This 210m
of subsidence then accumulates more sediment
inducing more load subsidence, and so on.
Ultimately sediment fill is many times the
thickness of the original subsidence.
10
Isostatic Response

• Glacial Rebound (Compositional Isostacy)

Uplift rate .5m/1000yrs
11
Tectonic/ Mechanical Processes

• Uncompensated (mechanical deformation) subsidence
• Transform (transtensional) zones
• Subsidence _at_10-100cm/1000yrs
• Convergence zones
• Uplift _at_30-200cm to as much as 8m/1000yrs

12
Plate Tectonic Settings for Basin Formation

• Crust Type/Heat flow
• Oceanic vs. Continental
• Plate Boundary Type/ Syndepositional Tectonics
• Convergent
• Divergent
• Transcurrent

13
Wilson Cycle

• Opening and closing of ocean basins and creation
  of continental crust

14
Rifted (Divergent) Plate Margins

• Rift Basins
• Thermal Uplift, Crustal thinning and Extensional
  (graben) Basins
• Modern Basin and Range (USA)
• Proto-oceanic troughs
• Modern Red Sea
• Proterozoic Keweenawan Rift - Mid-Continent, USA

15
Passive Continental Margins Basins

• Thermal and Isostatic (sediment loading)
  Subsidence
• North American Paleozoic-Cenozoic Atlantic Coast

16
Failed Continental Rifts

• Aulacogens Thermal/Isostatic Subsidence
• Paleozoic Anadarko Basin, Texas/Oklahoma
  Mississippi Embayment

17
Intra-Plate (Intracratonic) Basin Settings

• Intra-plate (Sag) Basins Thermal/Isostatic/????/S
  ubsidence
• Paleozoic Michigan Basin Illinois Basin

18
Oceanic Basins

• Compositional topography/ thermal subsidence
• Ophiolite
• Pelagic Sedimentation
• Preserved as structural anomalies, obducted slabs

19
Convergent Plate MarginsForearc, Backarc,
Retroarc Basins

• Ocean/Ocean Collision Orogens
• Mechanical Subsidence
• Trenches very deep (10K), narrow troughs.
  Sediment fill dependant on setting
• Modern Mariana Islands Paleozoic Antler Orogenic
  Belt???, Nevada
• Backarc basins Subduction faster than
  compression-- Extensional basins
• Izu-bonin arc-trench system, west pacific

20
Convergent Plate MarginsForearc, Backarc,
Retroarc Basins

• Ocean/Continent Collision Orogens
• Forearc basins
• Great Valley Sequence, Mesozoic California
  Neogene Puget Trough, Oregon/Washington
• Retroarc foreland basins mechanical
  subsidence/sediment loading Rocky Mountain
  Western interior

21
Convergent Plate MarginsForearc, Backarc,
Retroarc Basins

• Continent/Continent Collision (Suture) Orogens
• Peripheral foreland basins tectonic/sediment
  loading
• Molasse" deposits of the Catskill (Devonian)
  Deltas, Himalayan Neogene Siwalik Hills

22
Transcurrent Plate Margins

• Transtensional Basins
• Mechanical and Thermal Subsidence/Uplift
• Salton Trough (Neogene So CA, San Andreas Fault
  system, USA)

• Transpressional Basins
• Mechanical Subsidence/Uplift
• Ridge Basin (Neogene So CA, San Andreas Fault
  system, USA)

23
Plate Tectonic Setting for Basin Formation

• Predictive Insight
• Size and Shape of basin deposits, including the
  nature of the floor and flanks of the basin
• Type of Sedimentary infill
• Rate of Subsidence/Infill
• Depositional Systems
• Provenance
• Texture/Mineralogy maturity of strata
• Contemporaneous Structure and Syndepositional
  deformation
• Heat Flow, Subsidence History and Diagenesis

24
Interrelationship Between Tectonics -
Paleoclimates - and Eustacy

• Anorogenic Areas------
• Climate and Eustacy Dominate
• Orogenic Areas---------
• Sedimentation responds to Tectonism