Evolutionary ecology of early Paleocene planktonic Foraminifera; size, depth habitat and symbiosis

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doi: 10.1666/11027.1
Author(s): Birch, Heather S.; Coxall, Helen K.; Pearson, Paul N.
Author Affiliation(s): Primary:
Cardiff University, School of Earth and Ocean Sciences, Cardiff, United Kingdom
Volume Title: Paleobiology
Source: Paleobiology, 38(3), p.374-390. Publisher: Paleontological Society, Lawrence, KS, United States. ISSN: 0094-8373 CODEN: PALBBM
Note: In English. Supplemental information/data is available in the online version of this article. 63 refs.; illus., incl. 1 table, sketch map
Summary: The carbon stable isotope (δ13C) composition of the calcitic tests of planktonic foraminifera has an important role as a geochemical tracer of ocean carbon system changes associated with the Cretaceous/Paleogene (K/Pg) mass extinction event and its aftermath. Questions remain, however, about the extent of δ13C isotopic disequilibrium effects and the impact of depth habitat evolution on test calcite δ13C among rapidly evolving Paleocene species, and the influence this has on reconstructed surface-to-deep ocean dissolved inorganic carbon (DIC) gradients. A synthesis of new and existing multispecies data, on the relationship between δ13C and δ18O and test size, sheds light on these issues. Results suggest that early Paleocene species quickly radiated into a range of depths habitats in a thermally stratified water column. Negative δ18O gradients with increasing test size in some species of Praemurica suggest either ontogenetic or ecotypic dependence on calcification temperature that may reflect depth/light controlled variability in symbiont photosynthetic activity. The pattern of positive δ13C test-size correlations allows us to (1) identify metabolic disequilibrium δ13C effects in small foraminifera tests, as occur in the immediate aftermath of the K/Pg event, (2) constrain the timing of evolution of foraminiferal photosymbiosis to 63.5 Ma, ∼0.9 Myr earlier than previously suggested, and (3) identify the apparent loss of symbiosis in a late-ranging morphotype of Praemurica. These findings have implications for interpreting δ13C DIC gradients at a resolution appropriate for incoming highly resolved K/Pg core records.
Year of Publication: 2012
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 10 Paleontology, Invertebrate; Atlantic Ocean; Biologic evolution; C-13/C-12; Carbon; Cenozoic; DSDP Site 384; DSDP Site 528; DSDP Site 577; Deep Sea Drilling Project; Depth; Faunal list; Faunal studies; Foraminifera; Habitat; IPOD; Invertebrata; Isotope ratios; Isotopes; Leg 208; Leg 43; Leg 74; Leg 86; Lower Paleocene; Microfossils; Morozovella; Morphology; North Atlantic; North Pacific; Northwest Pacific; O-18/O-16; ODP Site 1262; Ocean Drilling Program; Oxygen; Pacific Ocean; Paleocene; Paleoecology; Paleoenvironment; Paleogene; Pelagic environment; Planktonic taxa; Praemurica; Protista; SEM data; Shatsky Rise; Size; South Atlantic; Stable isotopes; Symbiosis; Tertiary; Tests; Walvis Ridge; West Pacific
Coordinates: N322628 N322632 E1574324 E1574323
N402139 N402139 W0513948 W0513948
S283100 S271100 E0021927 E0013400
Record ID: 2012073228
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Abstract, Copyright, The Paleontological Society, Reference includes data from GeoScienceWorld, Alexandria, VA, United States