CHAPTER 5 ~ OCEAN Sediments

See Syllabus-revised Webpage HOMEWORK 1 DUE (Long Marine lab Field Trip) Turn in after class

HOMEWORK –problem sets 2 Late Policy: Lab assignments are due the week after posting. ~ mondays We ask that you complete your work on time, and will deduct 10% of the credit per day for any late assignments. NO EXCEPTIONS. If you have questions about or need help on the assignments, we invite you to come to the TAs' office hours. If you can't make office hours, we encourage you to make an appointment to meet with the TAs. TA – Sami

The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments OUTLINE

The Oceans Memory –Paleoceanography? Study of Oceans sedimentary record –Analyze Sediment Cores Challenge Question What is the Principle of Superposition? In a deposit of undisturbed sedimentary rocks, oldest rocks at the bottom, youngest at the top Sediments tell a story

The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments OUTLINE

Foundations of Paleoceanography Cesare Emiliani ( ) –Godfather of Paleoceanography –Measure ratio oxygen ( 18 O) vs normal oxygen ( 16 O) in shells of Fomanifera (plankton) Varies w/ temp. –Good Indicator of seaH 2 O temp/time »Cold H 2 O (high [ 18 O] vs 16 O »Warm H 2 O (low [ 18 O] vs 16 O »aka - delta O-18 »Look at O-18 in sediment cores

Foundations of Paleoceanography Emergence of Kullenberg piston corer –Cores of 10-20m into ocean basins... Representing 1-2 million years of sediments

DEEP Sea Drilling Projects (Sediment Cores) NSF ( ) – Changes in Climate ~ 700,000 years Climate: Long Range Investigation, Mapping and Prediction aka (CLIMAP) –Demonstrated Ice Ages result from Mileneum-Scale deviations From Earth’s Orbit around Sun -aka Milankovitch cycle Foundations of Paleoceanography

Milankovitch cycles (1-3) I 2 3 What do the Milankovitch cycles vary the amount of? Challenge Question? ~ 10*C temp changes  Ice Ages Solar radiation that reaches the earth What can this lead to / result in?

From Sediment Cores Heinrich Events discovered – What are they? Abrupt climate change/ rapid cooling within decades/ centuries Scientists concerned modern lifestyle leading to another... e.g. Global Warming  Mini ice age... 6 in last 75,000 years

Confirming your Knowledge –Using plankton (fomanifera) shells what elemental ratio is used to gauge cold/warmer sea water temp/time? –delta O 18 vs O 16 –What are Heinrich events/ how many occurred in last years? Rapid change in seawater temp/decades, 6

The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments OUTLINE

Classification of Marine Sediments many source types: -based on grain size & organism type Old Ocean Sediments: Mostly Phytoplankton Formanifera (carbonate) ooze - 50% Diatom (silica) ooze - 15% Phytoplankton Ocean Sediment CORE

The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments OUTLINE

Sedimentary Processes What are they? = production, transport, deposition of sediments

Sedimentary Processes How and where do sediments move about on the planet? 1. Starts w/ the Hydrologic Cycle -Exchange of H2O b/w various reservoirs

Sedimentary Processes 2. Continental Weathering – what is it? Challenge Question What are the 3 types weathering processes? 1. Physical – breaking apart of rocks via –Rock slides, earthquakes, debris flow 2. Chemical – dissolving of rocks via –Natural acidic rain, rivers etc. 3. Biological – activities of organisms via –fracture, dissolve, chemically alter rocks etc. Dissolving, fracturing/ chemical alteration of rocks – -important role in cycling of elements (Iron, Calcium etc. ) and salinity in Sea Water

Sedimentary Processes Sediment Sinking Grain size effects sinking –Sediment traps measure carbon flux Estimates Global carbon cycle Important For study of Climate change – plankton

Sedimentary Processes Biological sedimentation –The biological pump – complex – phytoplankton aka algae = PhytoPlankton ~ = Trees Take in CO 2 (from Atmosphere) give off Oxygen Lots of Stored Carbon (CO 2 ) in sediments Which Produces more O 2 (Air) for earth and by how much? Challenge Q Algae, 70-80%! Where does CO 2 come from?

Sedimentary Processes Calcium-Carbonate (calcite) Compensation Depth (CCD) –Below certain depth, calcite shells dissolve  –aka “the lysocline” –Challenge Q What factors influence the solubility (dissolution) of calcite shells? –Lower temp., Higher pressure

Sedimentary Processes Calcium-Carbonate (calcite) Compensation Depth (CCD) –The CCD - What is it? Depth/Region where: solid Calcite shells = dissolving Calcite shells –No net change (1:1) Area of high plankton growth – shallow CCD (Artic, Antartic) Area of low plankton growth – deep CCD (Hawaii) –Based on solubility of Calcite in Water (think of Sugar in Water) »If have LOTS, area is saturated (need more Liq. space to dissolve it) HAWAII-clear H 2 O Antartic Green/dark H 2 O Lots of algae Artic Green/dark H 2 O Lots of algae ALGAE Shells dissolve 

The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments OUTLINE

Global Distribution of Sediments Calcite (Carbonate) sediments occupy –~68% Atlantic~36% Pacific Lower microorganism (algae growth) responsible? Final Challenge Q Why does the N. Pacific NOT have the same Calcite deposition as the N. Atlantic? –Red clay occupies deepest regions (calcite) Think Geology (bathymetry) No Mid ocean ridge In N. Pacific for shells to land on They dissolve before then Can settle on something

Global Distribution of Sediments

The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments OUTLINE BREAK

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TABLES

Tab. 5.1