High frequency floral changes at the Paleocene–Eocene boundary revealed by comparative biomarker and palynological studies

Abstract

The Cap d'Ailly area (Upper Normandy, France) shows several terrestrial-lagoonal sections recording the negative Carbon Isotope Excursion (CIE) associated with the Paleocene-Eocene Thermal Maximum (PETM; 55.8 Ma). A study of the biomarkers and spores/pollen content of the Vasterival section gave complementary information on paleofloral changes that occurred around the PaleoceneEocene (P-E) boundary. Aliphatic hydrocarbon fractions revealed a high abundance of vascular plant biomarkers, including tricyclic diterpanes derived from conifers, fernenes derived from ferns and des-A-triterpenes derived from angiosperms. Whereas the vegetation of the depositional environment surroundings seemed alternately dominated by ferns and angiosperms (as revealed by biomarkers), the regional flora seemed strictly dominated by angiosperms such as Juglandaceae (as revealed by pollen).Spores/pollen assemblages reveal no major turnover in the paleovegetation, but slight variation in vegetation composition. However, both biomarkers and spores/pollen exhibited two intervals of rapid floral changes: the first occurred around the P-E boundary and the second at the top of the strictly terrestrial unit that coincides with a marine transgression. Comparison of these data with published paleoclimatic results, obtained from the same samples, indicated that the first interval of floral change was correlated with strong paleohydrological perturbations, whereas the second was linked to an increasing marine influence.

Aliphatic hydrocarbons and triterpenes of the Congo deep-sea fan

“…Similar correlations were observed in a more mature terrestrial set of samples (Garel et al, 2014). In a large set of immature marine and lacustrine samples, matching G 13 C values of both compounds evidenced a diagenetic relationship or a common source in (Sinninghe-Damsté et al, 2014).…”

“…The biological sources of the dominant triterpenes in the lobe sediments, hop-17(21)-ene, EE-hopane and diploptene (hop-22(29)-ene) are microorganisms and ferns (Douka et al, 2001;Innes et al, 1997Innes et al, , 1998Pattituci et al, 1995;Rohmer et al, 1984;Rohmer, 1993;Rontani and Volkman 2005;Sinninghe-Damsté et al, 2014;Welander et al, 2010). They are dominant triterpenes in terrestrial environments with low maturity of the organic matter (Garel et al, 2014). Their predominance in the Congo River sediments suggests that the export of land particles to the lobe complex is a significant source of these triterpenes ( Figure 6).…”

Multiple early Eocene carbon isotope excursions associated with environmental changes in the Dieppe-Hampshire Basin (NW Europe)

“…It is also affected by the degree of leaf-water transpiration and soil-water evaporation that depend on climatic parameters, and by interspecific variability, which is linked to the plant physiology and biochemistry (Smith and Freeman, 2006). However, previous studies on the paleovegetation of the Cap d'Ailly area revealed no correlation between vegetation changes and n-alkane δ 2 H values, implying that the latter are mostly linked to paleoclimatic changes and not to changes in vegetation (Garel et al, 2014;Garel-Laurin, 2013). Furthermore, Garel et al (2013) produced δ 2 H values of onocerane I, a biomarker considered specific to a limited number of angiosperm species (Jacob et al, 2004).…”

Molecular Biomarkers of Anthropic Impacts in Natural Archives: A Review

“…For instance, macroscopic charcoal is usually transported only a few 100 m to a few kilometers and is thus mostly a local fire proxy (Whitlock and Larsen, 2001), whereas levoglucosan can be transported as an aerosol hundreds of kilometers and is therefore a regional to hemispheric fire proxy (Zennaro et al, 2014). The opposite is true for pollen and plant biomarker, with pollen having a larger catchment area than biomarker (e.g., Jansen et al, 2013;Garel et al, 2014).…”

“…Paleoenvironmental records based on biomarker distribution and/or isotopic composition have been produced from a variety of archives, such as peat cores (e.g., Pancost et al, 2002), lake sediment cores (e.g., Jacob et al, 2008a;Simonneau et al, 2013), loess (e.g., Xie et al, 2002), and bat guano deposits (e.g., Wurster et al, 2010). These fossil molecules are resistant to biodegradation (e.g., Brocks and Summons, 2004), surviving passage through the digestive systems of animals largely unchanged, and travel through the Earth system for thousands to millions of years (e.g., Eglinton and Calvin, 1967;Brocks and Pearson, 2005;Garel et al, 2014). The most specific biomarkers have recently become powerful tools to trace human activities such as land-use (e.g., Fisher et al, 2003;Jacob et al, 2008a;Lavrieux et al, 2013;Simonneau et al, 2013;Guillemot et al, 2015), and are reviewed here.…”