Abstract The Toarcian Oceanic Anoxic Event (T-OAE) is marked by major palaeoenvironmental and palaeoceanographical changes on a global scale, associated with a severe disturbance of the global carbon cycle and organic-rich facies deposition. Here, a multiproxy approach (petrographic and geochemical techniques) was applied to the study of the organic content of the T-OAE of the Paris Basin, whose phytoplanktonic origin has been previously inferred by its geochemical signature. The top of the tenuicostatum Zone is characterized by palynomorphs and marine phytoplankton-derived amorphous organic matter (AOM), representing a proximal marine environment with emplacement of euxinic conditions at the top (total organic carbon/sulfur content and increase in AOM). At the base of the serpentinum Zone the proliferation of bacterial biomass begins, with phytoplankton playing a secondary role. This indicates the development of stagnant and restrictive conditions in a proximal environment, with water column stratification (neohop-13(18)-ene). The majority of the serpentinum Zone is dominated by bacterial biomass, suggesting a marine environment with bottom-water stagnation, possibly related to basin palaeogeomorphology and circulation patterns, with episodic euxinia. This therefore suggests that the T-OAE organic fraction is dominated by bacterial biomass, not phytoplankton, showing the importance of an integrated approach to the determination of the organic facies.

Abstract Nine non-pollen palynomorph (NPP) groups occur in Quaternary marine and brackish-water sediments; these groups represent various planktonic or micro- to macrobenthic organisms. Some extant NPP were previously classified as fossil Acritarcha, Chitinozoa or scolecodonts. We refer to reviews of these fossils and their applications for Paleozoic–Mesozoic biostratigraphy and palaeoecology but focus on extant marine NPP that can be studied by laboratory culture, genetics or micro-geochemical methods. Marine NPP include resting cysts of planktonic dinoflagellates and prasinophytes, tintinnids and other cilates, copepod eggs and skeletal remains, and various microzoobenthos: microforaminiferal organic linings, ostracod mandibles and carapace linings, various worm egg capsules and mouthparts. New micro-Fourier Transform Infrared spectroscopy spectra suggest the probable affinities of the tintinnid cyst type P and Beringiella . Our applications in marine biodiversity and provincialism studies emphasize under-studied polar regions and neglected ice-algae nano-plankton and compare climate-based NPP distributions to Ocean Biogeographic Information System realms. Trophic relationships are outlined using sediment-trap studies. Seasonal to annual-scale investigations of palaeoproduction provide new perspectives on ocean carbon budgets during times of rapid climate change and atmospheric carbon increase. More taxonomic and source-linkage studies of non-dinocyst marine NPP are needed but we outline potentials for studies of hemispheric or global-scale shifts in marine food webs as driven by ocean warming.

ABSTRACT Lignin phenol, pollen, and diatom analyses were performed on dated sediments (13,533–8993 cal yr B.P.) recovered from Fallen Leaf Lake, California. This multiproxy data set constrains the end of the Tioga glaciation in the Lake Tahoe Basin and reconstructs the response of the region’s aquatic and terrestrial ecosystems to climatic changes that accompanied the Younger Dryas, the end of the Pleistocene, and early Holocene warming. From the Pleistocene to the Holocene, lignin concentrations and syringyl/vanillyl (S/V) ratios increased, while cinnamyl/vanillyl (C/V) ratios and the lignin phenol vegetation index (LPVI) decreased, recording the proliferation of woody plant material and, particularly, the expansion of angiosperms as the Tioga glaciation ended and temperatures warmed. This interpretation is constrained by lignin phenol analyses of plant material from Fallen Leaf Lake’s present-day watershed. Complementary palynological analyses show a transition from a gymnosperm-dominated landscape to a more mixed angiosperm-gymnosperm vegetation assemblage that formed as closed canopy forests became more open and grasses and aster colonized meadows. Aquatic flora assemblages, in the form of greater amounts of green algae and greater percentages of diatom phytoplankton, indicate increased levels of lake primary productivity in response to warming. Principal component analysis (PCA) distinctly resolves the Pleistocene from the Holocene diatom flora. The Pleistocene flora is dominated by cyclotelloids and low-mantled Aulacoseira species that are rare in Fallen Leaf Lake today, but common at higher and colder elevations that may resemble the Pleistocene Fallen Leaf Lake. The Holocene diatom flora is dominated by Aulacoseira subarctica .