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Stable Isotope Constraints on Marine Productivity Across the Cretaceous‐Paleogene Mass Extinction
Author(s) -
Sepúlveda Julio,
Alegret Laia,
Thomas Ellen,
Haddad Emily,
Cao Changqun,
Summons Roger E.
Publication year - 2019
Publication title -
paleoceanography and paleoclimatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.927
H-Index - 127
eISSN - 2572-4525
pISSN - 2572-4517
DOI - 10.1029/2018pa003442
Subject(s) - isotopes of carbon , isotopes of nitrogen , paleogene , total organic carbon , carbon fibers , geology , extinction event , productivity , carbonate , organic matter , paleontology , oceanography , chemistry , environmental chemistry , nitrogen , cretaceous , materials science , biological dispersal , population , demography , organic chemistry , sociology , composite number , economics , composite material , macroeconomics
The effects of the Cretaceous‐Paleogene (K/Pg) mass extinction (~66 Ma) on marine primary and export productivity remain debated. We studied changes in carbon and nitrogen cycling in eight neritic and upper bathyal sections with expanded K/Pg boundary clay layers in the western Tethys and northeastern Atlantic Ocean, by measuring stable carbon isotopes of bulk carbonate (δ 13 C carb ) and organic matter (δ 13 C org ), nitrogen isotopes in bulk organic matter (δ 15 N), and selected compound‐specific carbon isotopic records (δ 13 C lipid ). Negative carbon isotope excursions (CIEs) in δ 13 C carb , δ 13 C org, and δ 13 C lipid are temporally and spatially heterogeneous as well as decoupled from each other, suggesting that factors affecting the δ 13 C of dissolved inorganic carbon, as well as isotopic fractionation during carbon fixation across the K/Pg, are more complex than commonly assumed. The negative CIEs in δ 13 C org and δ 13 C lipid at each site are smaller in amplitude and shorter in duration than those in δ 13 C carb , but in most sections both carbon pools recovered to preboundary conditions within the time of deposition of the boundary clay layer (<10 3 –10 4 Kyr) or shortly thereafter. This rapid recovery is supported by limited δ 15 N data, which mostly suggests moderate or minor changes in redox conditions (except in Denmark), marine productivity, and phytoplanktonic nitrate utilization in the earliest Danian. Our results indicate that carbon cycling and primary productivity in neritic and upper bathyal regions recovered to preboundary levels faster (<10 4 Kyr) than in oceanic regions (10 5 –10 6 years), likely sustained by resilient noncalcifying phytoplankton with resting stages, consistent with modeling and proxy studies.