Quaternary Environments Marine Sediments and Corals Marine Environments

Quaternary Environments Marine Sediments and Corals

Marine Environments T Cover more than 70% of the Earth’s surface T Between 6 -11 billion metric tons of sediment accumulate in the ocean basins annually

Definitions Planktic – Passively floating organisms living near the surface (0 -200 m depth) l Benthic – Bottom-dwelling organisms l Test – Protective covering l

CLIMAP T The CLIMAP Research Group Climate: Long-range Investigation, Mapping, and prediction (CLIMAP) T SST and Ocean Surface Conditions T From 635 ocean sediment cores T Data from faunal counts of diatoms, planktonic foraminifera, coccoliths, and radiolaria T Stratigraphy - percent fine, coarse, total carbonate, 18 O and 13 C T Geochemistry - percent opal, quartz, and organic carbon T

SPECMAP T Spectral Mapping Project Determining the spectral characteristics of ocean sediment-based paleoclimatic records T Establishing a basic timeframe for past climatic events T Climate times series of the past 400, 000 years T Based on 17 sediment cores from the Atlantic Ocean. T Quantitative data on planktonic species and assemblages which reflect conditions in the surface waters of the Atlantic Ocean T 18 O, 13 C difference (planktic and benthic), and Cd/Ca. T

Sedimentation in the Ocean

Problems With Marine Sediments T Selective dissolution of thin-walled specimens T Transportation by ocean currents T Removal of easily transported species T Introduction of exotics T These problems may make some ocean floor sediments unsuitable for paleoclimatic reconstructions

Regions Usable for Foram Studies

Important Organisms T Foraminifera - Zooplankton T Coccolithophores (coccoliths) – Unicellular algae T Dinoflagellate – Organic walled T Radiolarians – Siliceous zooplankton T Silicoflagallates – Siliceous T Diatoms – Siliceous algae

Foraminifera – Globigerina bulloides from the Labrador Sea Foraminifera – Neogloboquadrina pachyderma from the North Atlantic

Coccolith Centric Diatom Dinoflagellate Pennate Diatom

Paleoclimatic Inferences T T T Oxygen isotopic composition of Ca. CO 3 in foram tests Quantitative interpretations of species assemblages and their spatial variations through time Morphological variations in particular species resulting from environmental factors

Benthic 18 O record for equatorial Atlantic for the past 3. 2 Mya

SST Reconstructions for 18, 000 yrs BP

Coral Records of Past Climate T Reef-Building Massive Corals that have a symbiotic relationship with algae T The algae produce carbohydrates through photosynthesis and are therefore dependent upon water depth, turbidity, and cloudiness T Sectioned and x-rayed T High and low density bands can be distinguished with high-density bands relating to high SST

Drilling corals for paleoclimatic reconstruction. http: //www. noaanews. noaa. gov/magazine/stories/mag 95. htm

Growth bands in Coral. Arrows indicate "stress bands" revealed in an x-ray of coral skeletal material caused by cold, unfavorable temperatures. http: //www-ocean. tamu. edu/Quarterdeck/QD 6. 2/giese. html

Benefits of Coral Analysis T Tropical records that fill gaps left by other marine paleorecords T Annual resolution T Dating is checked with 230 Th T Possible extent back to 130, 000 years BP

Problems with Coral Analysis T Few records that extend past one century T Real extreme events may go unrecorded do to death of the coral colony for some period of time

Long Coral Based Records of Past Climate