Reconstructing changes in upper water habitats during the late Maastrichtian global warm event based on stable isotopes

Sigal Abramovich, Gerta Keller, Stüben D., Zsolt Berner

Research output: Contribution to conferencePaper

Abstract

Depth habitats of 56 late Cretaceous planktonic foraminiferal species from cool and warm climate modes were determined based on stable isotope analyses of deep-sea samples from the equatorial Pacific DSDP Sites 577A and 463, and South Atlantic DSDP Site 525A. The following conclusions can be reached: Planoglobulina multicamerata (De Klasz) and Heterohelix rajagopalani (Govindan) occupied the deepest plankton habitats, followed by Abathomphalus mayaroensis (Bolli), Globotruncanella havanensis (Voorwijk), Gublerina cuvillieri Kikoine, and Laeviheterohelix glabrans (Cushman) also at subthermocline depth. Most keeled globotruncanids, and possibly Globigerinelliodes and Racemiguembelina species, lived at or within the thermocline layer. Heterohelix globulosa
(Ehrenberg) and Rugoglobigerina, Pseudotextularia and Planoglobulina occupied the subsurface depth of the mixed
layer, and Pseudoguembelina species inhabited the surface mixed layer. However, depth ranking of some species varied
depending on warm or cool climate modes, and late Campanian or Maastrichtian age. For example, most keeled
globotruncanids occupied similar shallow subsurface habitats as Rugoglobigerina during the warm late Campanian,
but occupied the deeper thermocline layer during cool climatic intervals. Two distinct types of ‘vital effect’
mechanisms reflecting photosymbiosis and respiration effects can be recognized by the exceptional N13C signals of
some species. (1) Photosymbiosis is implied by the repetitive pattern of relatively enriched N13C values of
Racemiguembelina (strongest), Planoglobulina, Rosita and Rugoglobigerina species, Pseudoguembelina excolata
(weakest). (2) Enriched respiration 12C products are recognized in A. mayaroensis, Gublerina acuta De Klasz, and
Heterohelix planata (Cushman). Isotopic trends between samples suggest that photosymbiotic activities varied between
localities or during different climate modes, and may have ceased under certain environmental conditions. The
appearance of most photosymbiotic species in the late Maastrichtian suggests oligotrophic conditions associated with
increased water-mass stratification.
Original languageEnglish
StatePublished - 10 Sep 2006
EventFORAMS 2006 -
Duration: 30 Sep 2006 → …

Conference

ConferenceFORAMS 2006
Period30/09/06 → …

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