Monday, May 30, 2016

[Paleontology • 2014] Latest Cretaceous–earliest Paleogene Vegetation and Climate Change at the High Southern Latitudes: Palynological Evidence from Seymour Island, Antarctic Peninsula

Fig. 7. Artist's impression of the eastern flank of the Antarctic Peninsula during the Maastrichtian. The vegetation composition and habitat types are based on the nearest living relatives of the terrestrial palynoflora from Seymour Island discussed in this paper. Mixed temperate rainforest grew in the lowlands to mid altitudes composed mainly of a Nothofagus–podocarp–Proteaceae canopy with Lagarastrobus (Tasmanian Huon Pine) occupying the super-wet habitats along riverine margins. Freshwater pools hosted aquatic ferns and green algae with bordering wetlands filled with diverse mosses and ferns. At higher altitudes, open heath-like vegetation may have grown beyond the tree line of montane araucarian forests (detailed in Fig. 8). All fauna are known from the Cretaceous fossil record of the James Ross Basin
( Chatterjee, 1989, Chatterjee, 2002, Case et al., 2000, Case et al., 2003, Case et al., 2007, Clarke et al., 2005, Salgado and Gasparini, 2006, Cerda et al., 2012 and Coria et al., 2013). Artist: James McKay, University of Leeds.  DOI: 10.1016/j.palaeo.2014.04.018

• First quantitative vegetation analysis for the Antarctic during the Maastrichtian
• Terrestrial palynology suggests a temperate rainforest on the Antarctic Peninsula.
• Floral trends were influenced by concurrent changes in temperature and humidity.
• Cool, humid conditions gave way to a warmer climate ~ 2 myr before the K–Pg event.

Fluctuations in Late Cretaceous climate were already influencing biotic change prior to the environmental upheaval at the Cretaceous–Paleogene (K–Pg) boundary, but their general nature, magnitude and timing remain controversial. A high-resolution dataset on terrestrially-derived palynomorphs is presented from the high southern palaeolatitudes that unlocks details of small-scale climate variability throughout this period of significant global change. Specifically, this is a quantitative spore and pollen analysis of an expanded uppermost Cretaceous to lowermost Paleogene (Maastrichtian–earliest Danian) shallow marine sedimentary succession from Seymour Island, off the northeastern tip of the Antarctic Peninsula, then (as now) located at ~ 65°S. Using nearest living relatives the first detailed vegetation, habitat and climate reconstruction is presented for the emergent volcanic arc at this time. On the coastal lowlands, a cool to warm temperate rainforest is envisaged growing in a riverine landscape, with both wet (river margin, pond) and relatively dry (interfluve, canopy gap) habitats. Diverse podocarps and southern beech trees grew alongside angiosperm herbs and shrubs in mean annual temperatures of ~ 10–15 °C. Higher altitude araucarian forests gave way to open ericaceous heathland, beyond the tree line, in subalpine to alpine conditions with mean annual temperatures of a cold ~ 5–8 °C. There is no exact modern botanical equivalent, but the closest modern flora is that of the Andes of southern Chile and Argentina. Maastrichtian climate is shown to have fluctuated from cool, humid conditions, through a rapid warming ~ 2 million years prior to the K–Pg transition, followed by cooling during the earliest Danian, a trend supported by previous work on this interval.

Keywords: Late Cretaceous; Paleogene; Pollen; Palaeoclimate; Palaeoecology; Antarctica

Vanessa C. Bowman, Jane E. Francis, Rosemary A. Askin, James B. Riding and Graeme T. Swindles. 2014.  Latest Cretaceous–earliest Paleogene Vegetation and Climate Change at the High Southern Latitudes: Palynological Evidence from Seymour Island, Antarctic Peninsula. Palaeogeography, Palaeoclimatology, Palaeoecology. 408(15); 26–47.  DOI: 10.1016/j.palaeo.2014.04.018

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