convergent boundary due to interactions between different types of crust present on lithospheric plates Oceanic-continental convergence Oceanic-oceanic convergence Continental-continental convergence Plate with denser crust is always subducted Rocks of over riding plate undergo folding and are uplifted to form mountain range Subducted plate undergoes melting, molten material rises through over-riding plate and is extruded as lava Lava composition (&amp; type of eruption) a function of plate type/composition Associated chains of volcanoes: Continental arc Island arc Volcanic arc Deepest trenches associated with oceanic oceanic convergent boundaries Transform boundaries mark areas where plates move laterally against one another Form to accommodate differences in spreading rates along mid-ocean ridge system Two types: Oceanic transform faults occur wholly on the ocean floor (most common) Continental transform faults cut across continents Both types always offset two segments of a mid-ocean ridge Case studies origins of particular features Origin of seamounts, guyots, and atolls Originate at mid ocean ridges and are carried off ridge axis due to sea floor spreading Subside as underlying crust cools and contracts Age and structure of Great Barrier Reef Oldest &amp; thickest at northern end Records northward movement of Indian-Australian plate Intraplate features (e.g., intraplate volcanism) Mantle plumes hot spots Hawaiian Island-Emperor Seamount Chain (North Pacific) Yellowstone Galapagos Islands LECTURE 6: MARINE SEDIMENTATION &amp; STRATIGRAPHY I 25 Feb. 2000 ASSOCIATED READING: Pinet, Chapter 3 ( text internet site ) INTERESTING INTERNET LINKS: Ocean Drilling Program Data provided from marine sediments Sedimentary record provides complete, relatively uninterrupted record to 180 million years ago Fossils evolution of marine organisms, extinction events Rock type &amp; geochemistry climate variations, changes in oceanic circulation patterns, changes in nutrient supply to organisms Understanding responses to changes in ocean-climate parameters Methods for collecting sediment samples Clamshell sampler Gravity corer Platform drilling (Ocean Drilling Program) Classification of marine sediment &amp; controls on sedimentation Grain size classification (Wentworth-Udden) Most marine sediment mud-sand sized material, but all grain sizes occur Mode of formation classification Terrigenous sediment Biogenic sediment Authigenic sediment Volcanogenic sediment Cosmogenous sediment Controls on sediment character Source sediment composition Depositional energy grain size Rate of sediment supply sorting Hjulstr&ouml;m diagram Qualitative relationships between grain size and current strength Shelf sedimentation Grain size distribution across continental shelves Predicted variation in grain size across shelf Gravel &amp; sand (inner shelf) to silt &amp; clay (outer shelf) Predicted variation is offset due to sea level variations Find gravel &amp; sand on outer shelf relict sediment out of equilibrium Latitudinal variations in shelf sediment Polar shelves sediment derived from glacial processes Temperate shelves river-borne, terrigenous sediments Tropical shelves biogenic sediments (e.g., coral reefs) Less landmass at low latitudes Some sediment types are climate-dependent Carbonate shelves/carbonate platforms (CaCO3 limestone ) Growth limited by tolerances of corals and other reef-builders Form in warm, tropical waters away from influence of large rivers Most prolific reef growth on western margins of ocean basins (nutrient flux) Bucket model, reef zonation Highest/growth sedimentation rates at reef margin Shed material forms sediments on flanks and in lagoons Reefs also affected by sea level variation Subaerial exposure &amp; chemical alteration/lithification LECTURE 7: MARINE SEDIMENTATION &amp; STRATIGRAPHY II 28 Feb. 2000 ASSOCIATED READING: Pinet, Chapter 3 ( text internet site ) INTERESTING INTERNET LINKS: Ocean Drilling Program Deep-sea sediment Sources of sediment to the deep sea Continents (external) Volcanoes (external) Biota (internal) In situ precipitation of authigenic minerals (internal) Mechanisms for transport of sediment to the deep sea Bulk emplacement large quantities delivered in a single mass, involves mostly terrigenous sediment Settling from surface water involves biogenic sediment and fine (windblown) terrigenous and volcanigenic sediment (ash) Growth of minerals in place ferromanganese nodules, sulphides, phosphates Bulk emplacement of sediments to the deep sea During lowstands, sediment carried to shelf edge Buildup of sediment causes slope instability and slope failure Under influence of gravity, material is moved downslope Slumping movement of material downslope as a coherent mass, little internal deformation Flow of sediment-water slurries Internal bedding structures destroyed Turbidity currents Turbidites form when sediment is resuspended and mixed with water Mixture is dense, is pulled downslope under influence of gravity Often triggered by earthquakes Deposits of turbidity currents = turbidite Characterised by graded bedding (fining of grain size from base to top of deposit) Most turbidites associated with submarine canyons, which serve as chutes Turbidite deposits occur primarily at the mouths of submarine canyons, where they form thick, cone-shaped deposits called deep sea fans Grand Banks Earthquake and discovery of turbidity currents Ice rafting and deposition of glacimarine sediments Ice shelves can disintegrate into ice bergs, which float away Upon melting, release their sediment load Deposits characterised by poor sorting Pelagic deposition (settling of sediment from surface water) Sources Windblown dust from continents Major contributor is Africa Volcanic ash Ash carried to stratosphere and disseminated Blocks out solar radiation, gives rise to global cooling Biological remains (skeletal debris) from surface waters Types of biogenic pelagic sediment Based on chemical composition, two types of deposits: Calcareous oozes (CaCO3) chalk when lithified Remains of Phytoplankton single-celled plants (coccolithophores) Skeletons of Zooplankton single-celled animals (foraminifera) Siliceous oozes (SiO2) chert when lithified Remains of phytoplankton (diatoms) Remains of Zooplankton (radiolaria) Distribution of siliceous ooze and calcareous ooze Controlled by ocean chemistry Silica dissolution is greatest in surface waters and decreases in the colder, more acidic deep waters of the ocean High productivity of siliceous organisms in Equatorial and Polar waters Carbonate dissolution increases with depth in the oceans The point at which carbonate dissolution rates increase markedly is termed the lysocline.
(mountain range Subducted plate undergoes; melting; ) (plates; move laterally; T:another Form; to accommodate differences in spreading rates along mid-ocean ridge system Two types; L:areas) (influence of gravity; triggered; by earthquakes Deposits of turbidity currents; T:Often) (external) Volcanoes (external) Biota; involves; mostly terrigenous sediment Settling from surface water) Context(external ) Volcanoes ( external ) Biota involves,List([4052, 4279))):(Intraplate; features; ) Context(Intraplate features external ) Volcanoes ( external ) Biota involves,List([1360, 4279))):(type of eruption; studies; origins of particular features) Context(Intraplate features external ) Volcanoes ( external ) Biota involves,List([1360, 4279))):(Ocean Drilling Program Data; provided; from marine sediments) Context(Intraplate features Ocean Drilling Program Data provided external ) Volcanoes ( external ) Biota involves,List([1360, 4279))):(Mantle; plumes; hot spots) Context(external ) Volcanoes ( external ) Biota involves,List([4052, 4279))):(m diagram Qualitative relationships between grain size and current strength Shelf sedimentation Grain size distribution across continental shelves; Predicted; variation in grain size across shelf Gravel &amp) (Growth; limited; by tolerances of corals and other reef-builders Form in warm, tropical waters away from influence of large rivers) (sediment; is; resuspended and mixed with water Mixture) (most common) Continental; transform; faults cut across continents) (turbidite; Characterised; by graded bedding) (lithified Remains of Phytoplankton single-celled plants; is termed; the lysocline) (submarine canyons; serve; as chutes) (Major contributor; is; Africa Volcanic ash Ash) Context(Major contributor is,List([5744, 5764))):(Sources; Windblown; dust; from continents) (molten material; rises; ) Context(molten material rises,List([362, 383))):(convergent boundary due to interactions between different types of crust present on lithospheric plates Oceanic-continental convergence Oceanic-oceanic convergence Continental-continental convergence Plate with denser crust; is subducted; Rocks; T:always) (Most turbidites; associated; with submarine canyons) (organisms; Understanding; responses to changes in ocean-climate parameters Methods for collecting sediment samples) (reef zonation Highest/growth sedimentation rates at reef margin; Shed; material) Context(reef zonation Highest / growth sedimentation rates at reef margin Shed,List([3587, 3655))):(Some sediment types; are; climate-dependent Carbonate shelves/carbonate platforms) Context(Some sediment types are reef zonation Highest / growth sedimentation rates at reef margin Shed,List([3268, 3655))):(gravel &amp; sand on outer shelf relict sediment out of equilibrium Latitudinal variations in shelf sediment Polar shelves sediment derived from glacial processes; Temperate; ) Context(gravel & amp ; sand on outer shelf relict sediment out of equilibrium Latitudinal variations in shelf sediment Polar shelves sediment derived from glacial processes Temperate Some sediment types are reef zonation Highest / growth sedimentation rates at reef margin Shed,List([2965, 3655))):(clay (outer shelf) Predicted variation; is offset; due to sea level variations) (their sediment load Deposits; characterised; by poor sorting Pelagic deposition (settling of sediment from surface water) (sediment; mixed; with water Mixture) (solar radiation; gives; rise; to global cooling Biological remains (skeletal debris) from surface waters Types of biogenic pelagic sediment) (Oceanic transform faults; occur; L:wholly on the ocean floor) (large quantities; delivered; L:in a single mass) (Polar shelves sediment; derived; from glacial processes) (cone-shaped deposits; called; ) (lithified Remains of phytoplankton (diatoms) Remains of Zooplankton (radiolaria) Distribution of siliceous ooze and calcareous ooze; is; greatest in surface waters) (Most turbidites associated with submarine canyons,; disseminated; Blocks out) (molten material; is extruded; ) (lagoons; affected; by sea level variation Subaerial exposure &amp) (Ice shelves; can disintegrate; ) Context(Ice shelves can disintegrate,List([5501, 5529))):(little internal deformation Flow of sediment-water slurries; is; dense) (siliceous ooze and calcareous ooze; Controlled; by ocean chemistry Silica dissolution) (they; form; thick) (ice bergs; float; away; T:Upon melting) (Both types; offset; two segments of a mid-ocean ridge Case; T:always) (mostly terrigenous sediment; Settling; from surface water) (Bulk; emplacement; large quantities delivered in a single mass) (Sedimentary record; provides; complete, relatively uninterrupted record) (Slumping movement of material downslope as a coherent mass; is pulled; downslope; T:when sediment is resuspended and mixed with water Mixture) (Most turbidites associated with submarine canyons,; carried; to stratosphere) (Internal bedding structures; destroyed; Turbidity currents Turbidites form) Context(Internal bedding structures destroyed,List([4836, 4873))):(sediment; carried; ) Context(Internal bedding structures destroyed,List([4836, 4873))):(material; is moved; downslope) Context(material is moved Internal bedding structures destroyed,List([4688, 4873))):(ferromanganese nodules, sulphides; causes; slope instability and slope failure) (Types of biogenic pelagic sediment; Based; on chemical composition) (sediment; to shelf; edge Buildup of sediment) (faults; cut; L:across continents) (Turbidite deposits; occur; L:primarily at the mouths of submarine canyons) (carbonate dissolution rates; increase markedly; ) (Gravity corer Platform drilling; [is] sampler [of]; Clamshell)
external ) Volcanoes ( external ) Biota involves,List([4052, 4279)) Intraplate features external ) Volcanoes ( external ) Biota involves,List([1360, 4279)) Intraplate features external ) Volcanoes ( external ) Biota involves,List([1360, 4279)) Intraplate features Ocean Drilling Program Data provided external ) Volcanoes ( external ) Biota involves,List([1360, 4279)) external ) Volcanoes ( external ) Biota involves,List([4052, 4279)) Major contributor is,List([5744, 5764)) molten material rises,List([362, 383)) reef zonation Highest / growth sedimentation rates at reef margin Shed,List([3587, 3655)) Some sediment types are reef zonation Highest / growth sedimentation rates at reef margin Shed,List([3268, 3655)) gravel & amp ; sand on outer shelf relict sediment out of equilibrium Latitudinal variations in shelf sediment Polar shelves sediment derived from glacial processes Temperate Some sediment types are reef zonation Highest / growth sedimentation rates at reef margin Shed,List([2965, 3655)) Ice shelves can disintegrate,List([5501, 5529)) Internal bedding structures destroyed,List([4836, 4873)) Internal bedding structures destroyed,List([4836, 4873)) material is moved Internal bedding structures destroyed,List([4688, 4873))
mountain range Subducted plate undergoes plates influence of gravity external) Volcanoes (external) Biota Intraplate type of eruption Ocean Drilling Program Data Mantle m diagram Qualitative relationships between grain size and current strength Shelf sedimentation Grain size distribution across continental shelves Growth sediment most common) Continental turbidite lithified Remains of Phytoplankton single-celled plants submarine canyons Major contributor Sources molten material convergent boundary due to interactions between different types of crust present on lithospheric plates Oceanic-continental convergence Oceanic-oceanic convergence Continental-continental convergence Plate with denser crust Most turbidites organisms reef zonation Highest/growth sedimentation rates at reef margin Some sediment types gravel &amp clay (outer shelf) Predicted variation their sediment load Deposits sediment solar radiation Oceanic transform faults large quantities Polar shelves sediment cone-shaped deposits lithified Remains of phytoplankton (diatoms) Remains of Zooplankton (radiolaria) Distribution of siliceous ooze and calcareous ooze Most turbidites associated with submarine canyons, molten material lagoons Ice shelves little internal deformation Flow of sediment-water slurries siliceous ooze and calcareous ooze they ice bergs Both types mostly terrigenous sediment Bulk Sedimentary record Slumping movement of material downslope as a coherent mass Most turbidites associated with submarine canyons, Internal bedding structures sediment material ferromanganese nodules, sulphides Types of biogenic pelagic sediment sediment faults Turbidite deposits carbonate dissolution rates Gravity corer Platform drilling
melting move laterally triggered involves features studies provided plumes Predicted limited is transform Characterised is termed serve is Windblown rises is subducted associated Understanding Shed are sand on outer shelf relict sediment out of equilibrium Latitudinal variations in shelf sediment Polar shelves sediment derived from glacial processes is offset characterised mixed gives occur delivered derived called is disseminated is extruded affected can disintegrate is Controlled form float offset Settling emplacement provides is pulled carried destroyed carried is moved causes Based to shelf cut occur increase markedly [is] sampler [of]
T:another Form to accommodate differences in spreading rates along mid-ocean ridge system Two types L:areas
by earthquakes Deposits of turbidity currents T:Often
mostly terrigenous sediment Settling from surface water
origins of particular features
from marine sediments
hot spots
variation in grain size across shelf Gravel &amp
by tolerances of corals and other reef-builders Form in warm, tropical waters away from influence of large rivers
resuspended and mixed with water Mixture
faults cut across continents
by graded bedding
the lysocline
as chutes
Africa Volcanic ash Ash
dust from continents
Rocks T:always
with submarine canyons
responses to changes in ocean-climate parameters Methods for collecting sediment samples
material
climate-dependent Carbonate shelves/carbonate platforms
Temperate
due to sea level variations
by poor sorting Pelagic deposition (settling of sediment from surface water
with water Mixture
rise to global cooling Biological remains (skeletal debris) from surface waters Types of biogenic pelagic sediment
L:wholly on the ocean floor
L:in a single mass
from glacial processes
greatest in surface waters
Blocks out
by sea level variation Subaerial exposure &amp
dense
by ocean chemistry Silica dissolution
thick
away T:Upon melting
two segments of a mid-ocean ridge Case T:always
from surface water
large quantities delivered in a single mass
complete, relatively uninterrupted record
downslope T:when sediment is resuspended and mixed with water Mixture
to stratosphere
Turbidity currents Turbidites form
downslope
slope instability and slope failure
on chemical composition
edge Buildup of sediment
L:across continents
L:primarily at the mouths of submarine canyons
Clamshell