OCEAN CORES

1. CONTINUOUS SEDIMENTATION
• Fewer gaps than continental glacial or pluvial record
• Resolution of events depends on sedimentation rate and mixing
2. SEDIMENTATION RATE
• Ancient records available from short (10 m) cores where rate low
• Rate VARIES from PLACE TO PLACE and through TIME
  • Mid - Pacific Ocean 0.2 cm/1000 yr
    
  • Atlantic interglacial 2 cm/1000 yr, glacial 5 cm/1000 yr
    
  • Guaymas Trench 1 m/1000 yr
    
  • Occasionally laminated! (Rea et al, 2003)/

• Terrestiral: Calabrian Type Section (1600 m, S. Italy, first appearance of Arctica islandica and Anomalina baltica REF
  (Plio-Pleistocene, just above Olduvai normal subchron, 1.62 my)
  QUATERNARY = Ice Age ≠ Pleistocene
• Marine: periodic fluctuations (40,000 yr) begin ca. 2.5 my.
  
  above Matuyama/Gauss reversal
  Amplitude and length of oscillations (100,000 yr) increases ca. 0.7 my
  
  above Brunhes - Matuyama reversal
  
  

1872 H.M.S Challenger: first oceanographic expedition, collected bottom samples, showed distribution of planktonic organisms Late compared to land organisms (Linnaeus 1707-78)
1935 W. Schott (Gr.) published studies of short (1 m) cores, found 3 layers differing in foraminifera composition
1939 H.G. Stubbings - British Oceanographic Expedition Arabian Sea Core showed 4 layers of different foraminifera composition. Inferred 4 cold strata, 3 warm
1947-48 Albatross (Sw) used Kullenberg Piston Corer collected cores 10-15 m long. Demonstrated that the sedimentation rate is slow because there was less than 200 m of sediment on ocean floor
1950's beginning of collection of 100's of ocean cores stored at Columbia University, Lamont Geological Observatory (estate of T. Lamont) all NSF-sponsored oceanographic vessels take cores.
1955 Cesare Emiliani. University of Chicago, Classic Paper

1. Inorganic components
• LUTITE terigenous clays rivers, wind, icebergs
  2/3 of worlds rivers flow into the Atlantic Ocean
  lutite conc. highest during glaciations
• VOLCANIC ASH
  most abundant in S. Pacific and N. Atlantic
• METEORITES
  200,000 tons/yr, important in mid-Pacific
2. Remains of marine organisms "hydrogenous"

CARBONATE	SILICATE
COCCOLITHS algae	SILICOFLAGELLATES algae
FORAMINIFERA protozoa	DIATOMS algae
PTEROPODS snails	RADIOLARIA protozoa

1. FAUNAL DISPLACEMENT: Examples (Bradley)
Examples (Indicators):

    Calabrian Section Arctica islandica and Anomalina baltica
    Ivy and Mistletoe in European Environmental Sequence

• Stubbings (1939) found N. Atlantic foraminifera in Arabian core.
• David B. Erickson (1956) developed glacial/interglacial sequence based on Globigerina monardi as INDICATOR of interglacials
• Lidz (1966) temperature curve using ratio warm/cold species
• Imbrie and Kipp (1971) introduce TRANSFER FUNCTIONS
  (CALIBRATION of PROXY DATA)
  Foraminifera in core V12-122 (Caribbean) were compared to foraminifera in 61 modern sediment samples and modern sea-surface temperature
  Tm=XFm : Tp=XFp "X" is the TRANSFER FUNCTION

  
  Imbrie and Kipp techniques
  a. PRINCIPAL COMPONENT ANALYSIS

  data reduction into 5 groups
  A-tropical	B-subtropical	C-subpolar
  D-polar	X-gyre margin assemblage

  b. MULTIVARIATE REGRESSION (CALIBRATION)
  Tw = 23.6A + 10.4B + 2.7C + 3.7D + 2.0K (K=constant)
  
  
2. MORPHOLOGY OF FORAMINIFERA: biological response - no migration
a. Coiling: Direction (r) dextral, (l) sinistral
   Globoratalia truncatulinoides r=tropical l=temperate
b. Size: temp., salinity
c. Shape: height/width, convexity (temp.)
d. Structure/Sculpture (temp.)

3. CALCIUM CARBONATE CONCENTRATION
First piston cores from Albatross (Sw) expedition sent to Gustaf Arrhenius at Scripps Inst. Oceanography, Calif.
a. Productivity of calcareous organisms greater
b. Changes of ocean chemistry



4. TERRIGENOUS SEDIMENT COMPOSITION
grain morphology: desert vs. glacial vs. beach
a. Air-borne: now 25,000,000 tons/yr more during glacials
Satellite Images China Sahara
more exposed land, drier
transect of cores = southward sift of maximum aridity
b. Water-borne
c. Ice-rafted Sand
• Heinrich Events
• Atlantic Ocean sea-ice margin
  Today maximum deposition ice-rafted sand off Greenland
  18 K it was 1500 km SE

5. OXYGEN ISOTOPES

C. Emiliani (1955) proposed a chronology for the history of Pleistocene fluctuations of the ratio of ¹⁸O/¹⁶O in the tests of foraminifera (more ¹⁸O during glacials). Measured relative to arbitrary standard. Positive indicates grater than standard. More positive (= less negative) values indicate colder, BUT positive delta ¹⁸O values occur only in coldest periods.



	(18O/16O) sample - (18O/16O) SMOW
δ 18O =	--------------------------------------------	x 1000‰
	(18O/16O) SMOW



Two causes were initially proposed for ¹⁸O/¹⁶O fluctuations:
a. Biological fractionation in foram tests (Emiliani favored) ¹⁸O/¹⁶O ratio in living forams increases 0.023 % C^-1 (colder = more ¹⁸O)
b. ¹⁸O enrichment in oceans because ¹⁶O deposited in continental glaciers.
More ice = more ¹⁸O left in ocean (Shackleton, 1967)

1. Radiometric
-radiocarbon if age less tha 35,000
-Uranium decay 231Pa/230Th, 230Th/232Th
2. Paleomagnetism
Brunhes/Matuyama reversal at 0.7 ma
Olduvai event at 1.62 ma
Gauss/Matuyama at 2.48 ma
3. Raised Beaches Barbados and New Guinea U/Th dates on corals

130K, 240K, 330K, 400K (Bull and Cooper, 1986 ; Merritts and Bull, 1989)
4.Volcanic Ashes (dated):
N. Atlantic 65, 10.6 (9.8) K ash traces sea ice margin

• Extinctions (dated):
  Stylatractus universus (radiolarian) 425 Ka
  Discoaster pentaradiatus (coccolith ) 2.47 Ma
• Because of sedimentation rates, reworking, and differences among indicators (δ ¹⁸O/¹⁶O, carbonates, fauna), the shapes of curves are used in correlations, not the amplitudes
  
• Correlation with Milankovitch Curves: (Martinson et al., 1987)
  • changes in the earth's orbit that produce changes in the distribution of energy over the earth's surface and may cause the glacial/interglacial cycle.
  • adjust frequency of sea-core climatic cycles to match frequencies of orbital cycle 22,000 41,000 100,000 yr

OXYGEN ISOTOPE CHRONOLOGY

"MIS" Marine oxygen Isotope Stages

Odd numbered, low ¹⁸O = WARM, starting with Holocene (1)
5,7... previous interglacials + like modern
3 = mid-Wisconsin "interstadial"
Even numbered, high ¹⁸O = COLD, starting with Wisconsin (2)
major glaciations except no. 4 less uniform than interglacials - last 2-3 extreme #14 very minor
minor fluctuations 4-6 per stage
e.g. 5 broken up into a,b,c,d,e (or decimals 5.1, 5.2 ...)

Abrupt Deglaciations: most consistent feature of pattern
delimited by abrupt decrease in δ ¹⁸O
Roman numerals, I = Wisconsin/Holocene, II, III, IV...
Termination IV (Stage 11/12) is middle-late Pleistocene Boundary (EPICA, 2004)

Interval between TERMINATIONS
capital letters, A-H during Brunhes normal magnetic chron
A=Holocene, B=Wisconsin + Sangemon ,C...

WHAT IS THE Y-axis ?