Open AccessOceanic primary productivity and dissolved oxygen levels at the Cretaceous/Tertiary Boundary: Their decrease, subsequent warming, and recovery
Author(s) -
Kaiho Kunio,
Kajiwara Yoshimichi,
Tazaki Kazue,
Ueshima Masato,
Takeda Nobuyori,
Kawahata Hodaka,
Arinobu Tetsuya,
Ishiwatari Ryoshi,
Hirai Akio,
Lamolda Marcos A.
Publication year - 1999
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/1999pa900022
Subject(s) - geology , carbonate , authigenic , benthic zone , isotopes of oxygen , calcite , total organic carbon , oceanography , oxygen minimum zone , environmental chemistry , diagenesis , mineralogy , geochemistry , chemistry , organic chemistry , upwelling
Thirty‐six different geochemical and foraminiferal analyses were conducted on samples collected at closely spaced intervals across the Cretaceous/Tertiary (K/T) boundary exposed at Caravaca, Spain. A rapid reduction in the gradient between δ 13 C values in fine fraction carbonate and benthic foraminiferal calcite and a decrease in the abundance of phosphorus (a proxy for organic carbon) and calcium were recorded in sediments 0–0.5 cm above the K/T boundary. These trends imply that an abrupt mass mortality occurred among pelagic organisms, leading to a significant reduction in the flux of organic carbon to the seafloor. In addition, variations in sulfur isotope ratios, the hydrocarbon‐generating potential of kerogen (measured as the hydrogen index), and foraminiferal indices of dissolved oxygen level all imply that a rapid decrease in dissolved oxygen was coincident with the δ 13 C event. Evidence of the low oxygen event has also been recognized in Japan and New Zealand, suggesting that intermediate water oxygen minima were widely developed during earliest Danian time. A threefold increase in the kaolinite/illite ratio and a 1.2‰ decrease in δ 18 O (carbonate fine fraction) were recorded in the basal 0.1–2 cm of Danian age sediments. These trends suggest that atmospheric warming and an increase in surface water temperature occurred 0–3 kyr after the δ 13 C event. Recovery in the difference between δ 13 C values in the carbonate fine fraction and in benthic foraminiferal calcite as well as increases in phosphorus and calcium contents occur at the base of planktonic foraminiferal Zone Pla, implying that an increase in primary productivity commenced some 13 kyr after the K/T boundary. Tables A1‐A3 are available on diskette or via Anonymous FTP from kosmos.agu.org directory APENO (Username = anonymous, Password = guest). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009 or by phone at 800‐966‐2481; $15.00. Payment must accompany order.