APPENDIX: EXTRACTION FOR ISOLATING TERRIGENOUS MATERIAL

A series of papers have discussed the isolation of terrigenous material from deep-sea sediment (e.g., Rea and Janecek, 1981; Hovan and Rea, 1992; Olivarez Lyle and Lyle, 2002). In general, these works have used a similar overall procedure that involves sequential extraction to remove carbonate, metalliferous oxides and hydroxides, and biogenic silica. Rarely, however, are the actual steps presented. The detailed steps used in this study to extract terrigenous material are presented here, modified somewhat from notes kindly provided to us by Dr. Leah Joseph.

Carbonate Removal

  1. Place weighed masses of sample (~10 bulk g) into clean, labeled 500 mL Erlenmeyer flasks.
  2. Slowly add ~125 mL of 4.5-N (25% by volume) acetic acid to each flask in 10-mL increments to avoid loss by bubbling.
  3. Shake flasks with mechanical wrist-action shaker for 2 hr.
  4. Pour solutions from flasks into labeled 250-mL centrifuge bottles.
  5. Centrifuge for 13 min at ~4500 rpm and decant supernatant.
  6. Add ~125 mL of 4.5-N (25% by volume) acetic acid to each 250-mL centrifuge bottle.
  7. Sonicate for 5 min.
  8. Pour sample solutions back into corresponding Erlenmeyer flasks and shake again with mechanical wrist-action shaker for 2 hr.
  9. Pour solutions from flasks into corresponding 250-mL centrifuge bottles.
  10. Centrifuge for 13 min at ~4500 rpm and decant supernatant.

Metalliferous Oxyhydroxide Removal

  1. Fill a water bath with tap water to about three-quarters full and heat on hot plate to ~85C.
  2. Fill one 1000-mL beaker full and one 600-mL beaker with mixture of half ultrapure deionized (DI) water and half 0.3-M sodium citrate (50/50) and place on separate hot plate (solution hot plate) at a slightly lower setting.
  3. Add 40 mL of 0.3-M sodium citrate into each 250-mL centrifuge bottle.
  4. Slowly add 5 mL of 1.0-M sodium bicarbonate to each 250-mL centrifuge bottle.
  5. Place bottles in hot water bath and leave for 10–15 min. While waiting, fill one 1000-mL beaker full and one-600 mL beaker with 0.3-M sodium citrate and place on solution hot plate. Only fill the sodium citrate beakers during the first of two repeats (i.e., Step 9).
  6. Add ~1 g sodium dithionate (sodium hydrosulfite) to each 250-mL centrifuge bottle, stir continuously for 30 s, and return to hot water bath.
  7. After 5–10 min, add 100 mL of 50/50 solution to each centrifuge bottle and stir thoroughly.
  8. Centrifuge for 13 min at ~4500 rpm and decant supernatant.
  9. Repeat oxide/hydroxide extraction Steps 2–8.
  10. Add 100 mL of hot 0.3-M sodium citrate and stir thoroughly.
  11. Centrifuge for 13 min at ~4500 rpm and decant supernatant.
  12. Repeat Steps 3–11 so that each sample has received two extractions and hot rinses. Samples should now be a grayish green. If they are still reddish orange, another oxyhydroxide removal sequence may be necessary.
  13. Centrifuge for 13 min at ~4500 rpm and decant supernatant.

Opal Removal

  1. Wash each sample into a clean, labeled 600-mL beaker with ultrapure DI water.
  2. Fill beakers with ultrapure DI water to 400 mL and cover with watchglass.
  3. Place beakers directly on hot plate and bring to ~85C.
  4. Add 24 g sodium hydroxide (NaOH) to each beaker (1.5-M NaOH), stir thoroughly, and replace watchglass.
  5. Leave beakers on hot plate for 2 hr at ~85C. Stir solution after 1 hr.
  6. Remove beakers from hot plate and let cool for several minutes.
  7. Pour sample/solution into corresponding 250-mL centrifuge bottle, centrifuge for 13 min at ~4500 rpm, and decant supernatant.

Note: The opal removal step was not conducted on sediment samples from Leg 208 sites because they lack radiolarians and diatoms (Zachos, Kroon, Blum, et al., 2004).

Final Rinse

  1. Fill each 250-mL centrifuge bottle with ~40 mL of hot, ultrapure DI water and stir thoroughly.
  2. Wash solution and remnant sample into corresponding clean, dry, labeled, and preweighed 50-mL centrifuge tube.
  3. Centrifuge for 13 min at ~4500 rpm and decant supernatant.
  4. Repeat Steps 1–3 four times.
  5. Freeze the residue in the centrifuge tube for 12 hr.
  6. Freeze-dry the residue in the centrifuge tube for 48 hr.
  7. Tare the dried residue.