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).