In:
Climate of the Past, Copernicus GmbH, Vol. 18, No. 6 ( 2022-06-20), p. 1295-1320
Abstract:
Abstract. Late Paleocene deposition of an organic-rich sedimentary facies on the continental shelf and slope of New Zealand and eastern Australia has
been linked to short-lived climatic cooling and terrestrial denudation
following sea level fall. Recent studies confirm that the organic matter in
this facies, termed “Waipawa organofacies”, is primarily of terrestrial origin, with a minor marine component. It is also unusually enriched in 13C. In this study we address the cause of this enrichment. For Waipawa organofacies
and its bounding facies in the Taylor White section, Hawke's Bay, paired
palynofacies and carbon isotope analysis of heavy liquid-separated density
fractions indicate that the heaviest δ13C values are associated
with degraded phytoclasts (woody plant matter) and that the 13C
enrichment may be partly due to lignin degradation. Compound-specific stable carbon isotope analyses of samples from the Taylor White and mid-Waipara (Canterbury) sections display similar trends and further reveal a residual 13C enrichment of ∼ 2.5 ‰ in higher
plant biomarkers (long chain n-alkanes and fatty acids) and a ∼ 2 ‰–5 ‰ change in subordinate marine biomarkers. Using the relationship between atmospheric CO2 and C3 plant tissue δ13C values, we determine that the 3 ‰ increase in terrestrial δ13C may represent a ∼ 35 % decrease in atmospheric CO2. Refined age control for Waipawa organofacies indicates that deposition
occurred between 59.2 and 58.5 Ma, which coincides with an interval of
carbonate dissolution in the deep sea that is associated with a Paleocene
oxygen isotope maximum (POIM, 59.7–58.1 Ma) and the onset of the Paleocene carbon isotope maximum (PCIM, 59.3–57.4 Ma). This association suggests that Waipawa deposition occurred during a time of cool climatic conditions and increased carbon burial. This relationship is further supported by published
TEX86-based sea surface temperatures that indicate a pronounced
regional cooling during deposition. We suggest that reduced greenhouse gas
emissions from volcanism and accelerated carbon burial, due to tectonic
factors, resulted in short-lived global cooling, growth of ephemeral ice
sheets and a global fall in sea level. Accompanying erosion and carbonate
dissolution in deep-sea sediment archives may have hidden the evidence of
this “hypothermal” event until now.
Type of Medium:
Online Resource
ISSN:
1814-9332
DOI:
10.5194/cp-18-1295-2022
DOI:
10.5194/cp-18-1295-2022-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2217985-9
