GE Sedimentary processes and products Lecture 1. Depositional controls Geoff Corner Department of Geology University of Tromsø 2006 Literature: - Reading, 1996, Ch.2. Controls on the sedimentary rock record. - Leeder, 1999, ch. 1, 2, 13, 14, 15, 27, 28

Depositional controls ► Sediment supply ► Accomodation space Corner, in press

Sediment supply A) Terrigenous systems (allogenic, extrabasinal sediment source) – clastic sediments transported into the basin. B) Biochemical/chemical systems (autogenic, intrabasinal sediment source) – carbonate and other sediments produced in the basin.

Sediment supply ► Variations in:  Volume and rate of delivery  Grain size (calibre), etc.  Petrographic composition (siliciclastic, carbonate)  Mechanism of delivery (process) ► Determined by:  Bedrock geology  Tectonics/relief  Climate  Basinal water chemistry (for carbinates, etc.) ► (Denudation processes (weathering and erosion) and their intensity– dependent upon:  relief  Climate)

Sediment source (clastics) ► Weathering

Sediment source (clastics) ► Weathering ► Mass-wasting

Sediment source (clastics) ► Weathering ► Mass-wasting ► Erosion

Sediment source (clastics) ► Weathering ► Mass-wasting ► Erosion ► Attrition

Source area ► Relief  High relief  Low relief

Source area ► Relief ► Bedrock  Hard crystalline  Soft sedimentary

Sediment delivery system ► Glaciers ► Mass-movement ► Rivers ► Wind ► Waves ► Tidal and ocean currents

Accomodation space ► Basin morphology ► Base-level Corner, in press

Basin morphology ► Fjord example Corner, in press

Basin morphology ► Tectonic basin example

Basin morphology ► Shelf example

Base level ► Concept ► Sea-level

Sea level ► Eustatic (global) sea level (eustasy) ► Uplift/subsidence (isostasy) ► Relative sea-level ► Water depth Coe & Church, in Coe (ed.) 2003

Transgression and regression Galloway & Hobday 1996

Controls on deposition II ► Independent variables ► Extrinsic and intrinsic factors

Controls on deposition II ► Independent variables:  Climate  Tectonics Church & Coe, in Coe (ed.) 2003

Climate

Milankovitch

Controls on deposition II ► Independent variables ► Extrinsic and intrinsic factors

Depositional geometry ► Progradation ► Retrogradation ► Aggradation Prothero & Schwab 1996

Facies models and depositonal systems ► Facies ► Facies succession (vertical succession; fining-upward, thickening-upward trends, etc.) ► Architectural element - medium- scale three-dimensional depositional body characterised by a distinctive assemblage of facies and geometry. ► Depositional system - three- dimensional assemblage of lithofacies genetically linked by active or inferred processes and environments.

Hierarchy of depositional elements StrataDepositional unit ExampleAssemblages LaminaBedform Ripple Facies BedBed/arch. element Bar Facies ass./ MemberArchitectural element Channel arch.element FormationDepositional basin Valley-fill Facies assoc. GroupBasin/setting Foreland Miall, in Walker & James (eds.) 1992

Hierarchy of depositional elements Miall, in Walker & James (eds.) 1992

Facies analysis ► Key to analysing deposits: meaningful identification of bounding surfaces, facies associations and/or architectural elements. ► Key to understanding deposits: interpretation of depositional elements with reference to depositional models Depositional model = process + bedforms/geometry + preserved deposits process + bedforms/geometry + preserved deposits

Facies Einsele 1992

Facies and facies codes ► Facies Miall, in Walker & James (eds.) 1992

Facies successions Miall, in Walker & James (eds.) 1992

Architectural elements Miall, in Walker & James (eds.) 1992

Sequence stratigraphy Reading 1996

Practical tips on sedimentological analysis ► 1. Think process ► 2. Think three-dimensional ► 3. Think ’big picture’

Tip 1. Think ’process’ ► Example 1 –climbing-ripple bedding

Tip 1. Think ’process’ ► Example 2 – Fjord-valley fill stratigraphy Corner, in press

Transgressive systems tract Highstand systems tract Forced-regressive systems tract Corner, in press

Tip 2. Think ’3D’ ► Example 1 – Trace fossils in section

Tip 2. Think 3D ► Example 2 – primary sedimentary structures

Tip 2. Think 3D ► Example 3 – Vertical (2D) sections Vorren & Mangerud, in press

Tip 3. Think ’big picture’ ► Spatial aspects of the system ► Time aspects and system controls