Marine Sediments Lab - Seascisurf

Marine Sediments LabIntroductory OceanographyLaboratoryRay Rector: Instructor

Ocean Basins are Vast Depositories for Huge Amountsof Sediments Coming from Numerous Different SourcesShallow Inter-Tidal Sea BottomMarianas Trench Sea Bottom

Ocean Basins Act as Earth’s Memory Files:Files:Recording 100’s of Millions of Years of GeologicEvents and Sedimentation History

Four Major Origins for Seafloor Sediments1. Lithogenous Sources: Erosion of land; volcanic eruptions; wind-blown dust Material: Gravels, Sands, Silts, and Clays2. Biogenous Sources: Organic; accumulation of plant and animal hard parts Material: Calcareous and Siliceous Oozes3. Hydrogenous Sources: Precipitation of minerals from solution Material: Carbonates, Metal Oxides and Sulfides4. Cosmogenous Sources: Extraterrestrial dust and meteorites Material: Tektite particles, Glassy spheres, Silicate dust

Classification of Marine Sediments

Origin of Lithogenous SedimentsKey Points1) Primary source is continental rocks Granodiorite most common rock2) Granodiorite is mechanically brokendown into smaller and smaller pieces From boulder size to silt size Courser near source, finer farther away3) Granodiorite is chemically altered wheremost original minerals turn in clays Feldspars, micas, amphiboles and olivineget altered to clays Quartz is mineral is not altered4) Weathered rock is then eroded away(removed and transported from sourceregion to region of deposition.

Lithogenous Sediments and the Rock Cycle Weathering Breakdown of Rock Erosion Removal and Transport Deposition Settling of MaterialThe Rock CycleBreakdown and Removal

SEDIMENTARY PROCESSESThe Chemical/Physical Breakdown and Removal of RockFormation of LithoenousSediments Weathered Products Clays Quartz Dissolved Ions Erosion Methods Running water Moving ice Blowing wind Turbidity currents

Lithogenous Sediment SourcesSources: Rivers; Glaciers; Wind-blown dust; Coastal Erosion; Volcanic eruptionsMaterials: Silicate-rich Gravels, Sands, Silts, and Clays2) Glaciers1) RiversMajor Sediment Input to the OceansSourceEstimated Amount(109 tons/yr)Rivers18.3Glaciers2.0Wind blown dust0.6Coastal erosion0.25Volcanic debris0.15Groundwater 0.483) Wind-blown dust4) Coastalerosion5) Ash fromvolcaniceruptions

Origin of Biogenous SedimentsKey Points1) Primary source is marine life hard parts Shells and skeletons of dead organisms2) Hard parts from dead planktonic andbenthic organisms settle to the bottom From cobble size to microscopic Material may be further broken down byweathering and erosional processesShallow, benthic biogenous material Courser near source, finer farther away3) Biogenic material is mainly of two types Silica – SiO2 Calcium carbonate – CaCO34) Two general biogenous sedimentdepositional regions are shallow (littoral andshelf) and deep (abyssal pelagic)Deep pelagic biogenous material

Biogenous Sediment SourcesSources: Organic; accumulation of plant and animal hard partsMaterial: Mostly Calcareous and Siliceous Shells and SkeletonsDeep Ocean SeafloorPlankton Tests

Shallow Water Biogenous SedimentsKey Points1) Remains of invertebrate animal hard parts Shells and skeletons of benthic organisms2) Organisms living from shore out on the shelf Mollusks, corals, forams, sponges, crustaceans Material collects to form beach and shelfdepositsCoral-rich beach sand fromMolokai, Hawaii Mostly carbonate in composition3) Biogenous material can dominate the shorelineand shallow water seafloor if there is little to nolithogenous sediment input in the region Coral sand beaches are a good example Extensive carbonate shelf platforms in tropicalregionsForaminifera-rich beach sandHatoma Island Okinawa Japan

The Most Common Minerals inMarine Sediments“Biggie” Sediment Minerals Quartz-Silica Clays CarbonatesOther Sediment MineralsSediment Composition Chart Iron Oxides Phosphates Sulfates Sulfides

Reaction to Acid – The “Acid“Acid Test”Test”Defined: Carbonate minerals react toacid solution (HCl): bubble and dissolve Good for positive ID of carbonates Typically either calcite or dolomite Limestone & Calcareous oozes will fizz Silicate minerals and rocks do not fizz Use the acid test only if you think thatyour unknown mineral or rock has lowhardness – close to 3. ineral/mineral.html

SedimentClastCharacteristicsClast SizeClast ShapeClast urce1) Clast size is a function of transporttime & transport mediumSilt-size An indicator of depositional environment2) Clast shape is a function of transportdistance and timeClay-size An indicator of sediment “maturity”3) Clast sorting is a function of transportmedium An indicator of depositional environment

Predominant Sediment Types and GrainSizes at Specific Depositional t Size

Predominant Sediment Types and GrainSizes at Specific Depositional SettingsPointLa JollaGravel-sizeSand-sizeSilt-sizeClay-sizeClast SizeLa JollaShores

Sedimentary Environments are Where SedimentsDeposit and Sedimentary Rocks Form

Seafloor Sediment ProvincesCross--Section Profile of an Ocean BasinCross Continental shoreline Littoral Province Continental shelf Neritic Province Continental slope to rise Transitional All deep sea regions Oceanic

Marine Depositional EnvironmentsFour Major Depositional Provinces1) Very Shallow (shoreline and back shoreline) “Littoral”2) Shallow (over the shelf and banks) “Neritic”3) Slope/Rise (transitional) or “Bathyl“Bathyl””4) Deep (the abyss) “Oceanic”

Type and Locality of Marine SedimentsTypesLocalities1) Lithogenous1) Littoral2) Biogenous2) Shelf3) Hydrogenous3) Slope/Rise4) Cosmogenous4) Pelagic

Marine Sediment Sampling LocationsPrimary Sampling Institutions:1) Governments Agencies2) Academic Institutions3) Oil Companies

Marine Sediment Sampling Methods1) Bucket-Scooping2) Piston Coring4) Submersible3) Drilling

Continental Margins of the World1) Seafloor that includes shorelines and continental shelves2) Submerged continental margins are colored pale orange3) Average width of continental margins is 80 km4) Depths of continental margins typically down to 150 meters5) Continental margin seafloor bedrock mostly granitic rock

Shoreline and Shelf SedimentsKey Points1) Shallow marine sediments that deposit alongshorelines and offshore shelf are termed neritic2) Coast and shelf sediments are of two types: LandLand--derived inorganic rock and mineralfragments of gravel, sand, silt, and clay Organic carbonate materials of marine lifeskeletons and seawater precipitates3) Shelf sediments mostly arrive via rivers4) Coastal sediments may reach deep waters viaturbidity currents moving down submarine canyons

Lithogenous Beach SandMineral CompositionLight--Colored MineralsLight1) Quartz2) Feldspar3) Muscovite micaDark--Colored MineralsDark1) Hornblende2) Biotite3) Pyroxene4) Garnet5) Olivine6) MagnetiteLocation: San Diego1 millimeterSediment Grain Size and Shape

Beach Sand AnalysisDo the Following Steps1) Determine Mineralogy and MineralPercentagesGrainSizes2) Determine Grain Size – Use this chart3) Determine Grain Shape (Roundness)4) Sketch several sand grains5) Think about sediment sources/origin andhow it got transported6) Think about the relationship between grainsize and energy of environment7) Think about the relationship between grainshape and sediment maturityGrainShape

Continental Slope and Rise SedimentsKey Points Thickest ocean sediment piles Up to 20 km thick! Thickest sections found at base ofsubmarine canyons in the form of fanshape sediment wedges Mainly consists of sand, silt and claywithin “graded” bedding layers Continentally derived, but classified astransitional-deep sediment Primarily transported and deposited byturbidity current processes Turbidity currents are densemixtures of sediment and seawaterthat flow down slopes of seafloor Associated with submarine canyons

Turbidity Sedimentation ProcessesLab Simulation of TurbidityCurrents and Deposition ofGraded Bedding

Turbidity Current ExperimentDo the Following Steps1) Prepare Turbidity Sediment Samplein a graduated beaker: Mix: 15 mL of sand,15 mL of silt, and25 mL of vermiculate slurry2) Carefully, but quickly, pour the sample(all at once) into up-slope end ofseawater-filled turbidity tank3) Record observations of turbidity event4) Draw cross-section sketch of yourturbidity layer5) Answer set of turbidity question onworksheetTurbidity Tank Demo

Graded Bedding ExperimentDo the Following Steps1) Prepare Graded Bed Sample: Add 50 mL of poorly-sortedsediment mixture in agraduated beaker2) Carefully, but quickly, pour sampleinto top of sediment settling tube3) Record observations of event4) Draw cross-section sketch of yourgraded bed5) Answer set of graded beddingquestion on worksheetGraded Bedding Demo

Deep Ocean Basins1) Deep seafloors from continental slope to mid-ocean ridge3) Deep ocean bottom is shown in blue color (except for lakes)4) Average depth of abyssal seafloor is 4000 meters5) Deepest seafloor down to 11,000 meters6) Deep seafloor bedrock consists of basaltic volcanic rock

Abyssal Plain and Hill Sediment ProvinceKey Points Thick pelagic sedimentcovers a rugged subsurfacebedrock of basalt Abyssal plains are theflattest, most featurelessprovinces on Earth Abyssal hills are tops ofseamounts sticking out Abyssal plains and hillscover the most extensivetracts of ocean seafloor Subsurface imaging of abyssal plains and hills from seismic reflectionstudies and deep sea drilling

Deep MarineSedimentsKey Points1) Deep ocean sediments aredominantly of “pelagic”“pelagic” origin2) Pelagic sediments originate in surfacewaters, and get to deep ocean byvertical settling through water column3) Pelagic sediment is very finefine-grained4) Two types of pelagic sediments Inorganic clays Biogenic oozes5) Two types of biogenic oozes Calcareous Siliceous6) Each type of pelagic sediment has aunique region of deep sea floor where itis most abundant

Biogenous Sediment SourcesSources: Organic; accumulation of plant and animal hard partsMaterial: Calcareous and Siliceous Oozes and DetritusDeep Ocean SeafloorPlankton Tests

Calcareous Ooze Sediments Accumulation of calcium carbonate hard parts from dead microscopic plankton Mainly consists of cocolithophores and foraminifera tests Calcite-shelled plankton abundant in warmer surface waters Accumulate above the Carbonate Compensation Depth (CCD)foraminiferacocolithophores

Distribution of Calcareous OozeSediments1) Calcareous oozes principally deposit in relativelyshallow, low- to mid-latitude regions of deep ocean2) Concentrated on tops and flanks of mid ocean ridges

Silica Ooze Sediments Accumulation of silica hard parts from dead plankton Mainly consists of diatoms and radiolarian tests Abundant in deeper, cooler surface waters – high latitude

Silica Ooze Sediments Accumulation of silica hard parts from dead plankton Mainly consists of diatoms and radiolarian tests Abundant in cooler surface waters – high latitude

Comparing Silica and Carbonate Oozes

Types of Hydrogenous Sediment Sources: Precipitation of minerals from solution Minerals: Carbonates, Phosphates, Metal Oxides and SulfidesBlack SmokerChimneys SulfidesManganeseNodules

Type and Distribution of Marine Sediments

Deep Ocean Sediment AnalysisDo the Following Steps1) Determine Mineralogy of Deep Sea Sediment Lithogenous? Biogenous? Hydrogenous?1) Determine mineralogy Siliceous? (Silica or Clay) Calcareous? (calcite) Use acid test if youthink you might have a carbonate Oxide? (dark and crusty)3) Name the type sediment sample Ooze? Pelagic clay?4) Sketch sample grains if visible5) Think about origin and where in the deep oceanwould this sediment most likely accumulate If it’s an ooze, would it accumulate above orbelow the CCD?

Percentage Distribution of Pelagic Sediments1) Calcareous Oozes covers 48% of deep seafloor2) Siliceous Oozes covers 15% of deep seafloor3) Abyssal Clays covers 38% of deep seafloorNote the variation in the proportions of the three pelagicsediment types from one ocean basin to another

Rates of Deposition of Marine Sediments