Sedimentary Basins 1-2.pdf · Sedimentary Basins . ILOs . The aim of this course is to examine ....
Transcript of Sedimentary Basins 1-2.pdf · Sedimentary Basins . ILOs . The aim of this course is to examine ....
Sedimentary Basins
ILOs
The aim of this course is to examine the architecture sedimentary basins. The role of sediment loading and uplift, sea-level change in contributing to basin stratigraphy. opportunities for developing computer skills in the modelling thermal subsidence and uplift, crustal structure and, stratigraphy
Course outline
Basin classification schemes Basin structure and evolution characteristic depositional systems
Literatur
Miall, A.D., 1984, Principles of Sedimentary Basin Analysis: Springer, 490 p.
What are sedimentary basins
A low area in the Earth’s crust, of tectonic origin, in
which sediments accumulate.
1. Sedimentary basins are regions where considerable thicknesses of sediments have accumulated
2. prolonged crustal subsidence
Tectonics control
nature of sediment rate of sediment supply rate of deposition depositional environment nature of source rocks nature of vertical succession
climate – tectonics – sediments
How do you gather data on sedimentary basins
master cross sections stratigraphic sections isopach maps lithofacies maps ratio maps paleocurrent maps grain-size maps
What causes subsidence? What is tectonic setting?
HOW BASINS ARE MADE
Thermal
Flexural
Plate motions
Divergent – plates moving apart Mid-ocean ridges, rifts
Convergent – plates moving towards other Subduction zones
Strike-slip systems
Basin Classification
Ingersoll and Busby (1995): Divergent Intraplate Convergent Transform Hybrid
CLASSIFICATION OF SEDIMENTARY BASINS
descriptive
nature of fill geometry paleogeography tectonic setting
genetic
Rift-related basins
The down-dropped basin formed during rifting because of stretching and thinning of the continental crust
Rift-related basins
Subsidence along a passive margin, mostly due to long-term accumulation of sediments on the continental shelf
Subduction-related basins
Downward flexure of the subducting and non-subducting plates (sites of accretionary wedges)
Subduction-related basins
The area between the accretionary wedge and the magmatic arc, largely caused by the negative buoyancy of the subducting plate pulling down on the overlying continental crust
Subduction-related basins
depression caused by the weight of a large mountain range pushing the adjacent crust below sea level
Subduction-related basins
result from tensional forces caused by oceanic trench rollback. The arc crust is under extension/ rifting as a result of the sinking of the subducting slab
Transform-fault basins
A pull-apart block (eg. between two transform faults) that subsides significantly
Wilson
Intracratonic Basins
Rift Basins
Elongate, valleys bounded by normal faults Few km -> 10s of kmwide Length – up to 1000s km Occur in many platesettings, but
mostcommon in divergentsettings
Aulacogens
“Failed rifts” Occur at high angle to
continental margin Fill: non-marine to deep marine
Extensional basins
passive continental margins • Pre-Rift phase includes sedimentary and tectonic setting prior to initiation of rifting. Depends on pre-rift setting. Commonly continental sedimentation on craton. • Rift phase is tectonically active, with normal faulting, crustal thinning, volcanism, high heat flow and locally high rates of subsidence and sediment accumulation. • Drift phase (post-rift) = dominated by lithospheric cooling, thermal subsidence, and development of broad flexural basins dominated by sediment loading (e.g. continental embankments).