Transcript Chapter 5
CHAPTER 5 ~ OCEAN Sediments HOMEWORK 1 DUE (Long Marine lab Field Trip) Turn in after class See Syllabus-revised Webpage • 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 – [email protected] OUTLINE The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments • The Oceans Memory –Paleoceanography? Sediments tell a story • 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 OUTLINE The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments Foundations of Paleoceanography • Cesare Emiliani (1922-1995) – Godfather of Paleoceanography – Measure ratio oxygen (18O) vs normal oxygen (16O) • in shells of Fomanifera (plankton) • Varies w/ temp. – Good Indicator of seaH2O temp/time » Cold H2O (high [18O] vs 16O » Warm H2O (low [18O] vs 16O » 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 Foundations of Paleoceanography • DEEP Sea Drilling Projects (Sediment Cores) • NSF (1971-1982) – 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 Milankovitch cycles (1-3) I 2 Challenge Question? 3 What do the Milankovitch cycles vary the amount of? Solar radiation that reaches the earth What can this lead to / result in? ~ 10*C temp changes Ice Ages 1 From Sediment Cores 2 3 4 Heinrich Events discovered – What are they? 6 5 Abrupt climate change/ rapid cooling within decades/ centuries 6 in last 75,000 years. . . Scientists concerned modern lifestyle leading to another. . . e.g. Global Warming Mini ice age . . . http://www.youtube.com/watch?v=Cs56_GqTyIQ&feature=related • Confirming your Knowledge – Using plankton (fomanifera) shells what elemental • ratio is used to gauge cold/warmer sea water temp/time? – delta O18 vs O16 – What are Heinrich events/ how many occurred in last 75000 years? • Rapid change in seawater temp/decades, 6 OUTLINE The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments 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 OUTLINE The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments 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? Dissolving, fracturing/ chemical alteration of rocks – -important role in cycling of elements (Iron, Calcium etc. ) and salinity in Sea Water • 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. 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 Where does CO2 come from? • aka algae = PhytoPlankton ~ = Trees Take in CO2 (from Atmosphere) give off Oxygen Challenge Q Which Produces more O2 (Air) for earth and by how much? Algae, 70-80%! Lots of Stored Carbon (CO2) in sediments 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) ALGAE HAWAII-clear H2O ALGAE Antartic Green/dark H2O Lots of algae Shells dissolve Shells dissolve Shells dissolve Artic Green/dark H2O Lots of algae OUTLINE The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments 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? Think Geology (bathymetry) No Mid ocean ridge In N. Pacific for shells to land on They dissolve before then Can settle on something (calcite) –Red clay occupies deepest regions Global Distribution of Sediments OUTLINE The Oceans Memory Foundations of Paleoceanography Classification of Marine Sediments Sedimentary Processes Global Distribution of Sediments BREAK Page 73 Fig. 5.9 Fig. 5.18 Fig. 5.2 Fig. 5.5 Fig. 5.7 Fig. 5.8 Fig. 5.8.a Fig. 5.8.b Fig. 5.8.c Fig. 5.12 Page 81 Page 84 TABLES Tab. 5.1