Palynological Evidence from Seymour Island, Antarctic Peninsula

Palaeogeography, Palaeoclimatology, Palaeoecology 408 (2014) 26–47 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Latest Cretaceous–earliest Paleogene vegetation and climate change at the high southern latitudes: palynological evidence from Seymour Island, Antarctic Peninsula Vanessa C. Bowman a,⁎, Jane E. Francis a,RosemaryA.Askinb, James B. Riding c, Graeme T. Swindles d a British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK b Jackson, WY, USA c British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK d School of Geography, University of Leeds, Leeds LS2 9JT, UK article info abstract Article history: Fluctuations in Late Cretaceous climate were already influencing biotic change prior to the environmental up- Received 21 January 2014 heaval at the Cretaceous–Paleogene (K–Pg) boundary, but their general nature, magnitude and timing remain Received in revised form 29 April 2014 controversial. A high-resolution dataset on terrestrially-derived palynomorphs is presented from the high south- Accepted 30 April 2014 ern palaeolatitudes that unlocks details of small-scale climate variability throughout this period of significant Available online 9 May 2014 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 Keywords: Late Cretaceous Island, off the northeastern tip of the Antarctic Peninsula, then (as now) located at ~65°S. Using nearest living rel- Paleogene atives the first detailed vegetation, habitat and climate reconstruction is presented for the emergent volcanic arc Pollen at this time. On the coastal lowlands, a cool to warm temperate rainforest is envisaged growing in a riverine land- Palaeoclimate scape, with both wet (river margin, pond) and relatively dry (interfluve, canopy gap) habitats. Diverse podocarps Palaeoecology and southern beech trees grew alongside angiosperm herbs and shrubs in mean annual temperatures of ~10– Antarctica 15 °C. Higher altitude araucarian forests gave way to open ericaceous heathland, beyond the tree line, in subal- pine to alpine conditions with mean annual temperatures of a cold ~5–8 °C. There is no exact modern bo- tanical 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. © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/). 1. Introduction Furthermore, it has remained at approximately its present latitude (65°S) since the Cretaceous (Hathway, 2000). Major climatic fluctuations during the latest Cretaceous were It is well established that climates were cool and dynamic during the already influencing global biotic change immediately prior to the Creta- Late Cretaceous and there is indirect evidence for ephemeral ice sheets ceous–Paleogene (K–Pg) boundary at 66 million years ago (Ma) (Keller, on Antarctica (Barrera, 1994; Barrera and Savin, 1999; Li et al., 2000; 2001; O'Dea et al., 2011). However, details of small-scale climate vari- Miller et al., 2005; Davies et al., 2009; Thibault et al., 2010; Bowman ability, particularly from the climatically-sensitive high palaeolatitudes, et al., 2013a). Global climate change at this time has been associated have been lacking due to a paucity of suitable Upper Cretaceous sedi- with episodes of outgassing from major volcanic events (Courtillot mentary successions. This paper presents a detailed quantitative analy- et al., 1986; Hansen et al., 1996; Chenet et al., 2009), orbital cyclicity sis of terrestrially-derived palynomorphs (spores and pollen) from a (Miller et al., 2003; Stüben et al., 2003; Gallagher et al., 2008)andtecto- continuous and superbly-exposed succession on Seymour Island, off nism (Frank and Arthur, 1999), before culminating at 66 Ma in the the northeast tip of the Antarctic Peninsula (Fig. 1). Seymour Island rep- cataclysmic upheaval caused by a large bolide impact at Chicxulub, on resents the most expanded and best exposed uppermost Cretaceous to the Yucatán Peninsula, Mexico (Schulte et al., 2010). lowermost Paleogene succession from the high southern latitudes. In the mid to high southern latitudes, records of latest Cretaceous terrestrial fossils are sparse; these include wood (Francis and Poole, ⁎ Corresponding author. Tel.: +44 1223 221400. 2002; Poole et al., 2005), leaves (Kennedy et al., 2002) and spores and E-mail address: [email protected] (V.C. Bowman). pollen (Askin, 1989, 1990a, 1990b; Dettmann, 1994; Askin and Spicer, http://dx.doi.org/10.1016/j.palaeo.2014.04.018 0031-0182/© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/). V.C. Bowman et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 408 (2014) 26–47 27 Fig. 1. Location maps showing the measured section D5.251 across southern Seymour Island, Antarctic Peninsula. A–C, The maps show modern geography with outcrop of the Marambio and Seymour Island groups on islands in the James Ross Basin. Refer to Bowman et al. (2012) for palaeogeographic maps of this region during the Maastrichtian. D, Measured section D5.251, across the southern part of Seymour Island is a composite of sub-sections (correlated along strike in the field) and includes the oldest strata on the island north of Cape Lamb. The sedimentary sequence on southern Seymour Island dips at a shallow angle to the southeast. K, Cretaceous; Pg, Paleogene. The location of the K–Pg boundary is shown within the uppermost López de Bertodano Formation. 1995). Quantitative biostratigraphical analyses of terrestrially-derived arc basin (the Larsen Basin). The Antarctic Peninsula may have been palynomorphs have concentrated on the K–Pg transition, rather than joined to southern South America by a narrow land bridge to the distant the immediately underlying successions (Askin and Jacobson, 1996; north (Hathway, 2000; Leppe et al., 2012), and the Larsen Basin opened Vajda et al., 2001; Vajda and Raine, 2003; Vajda and MacLoughlin, into the Weddell Sea to the east. There, huge volumes of fine-grained 2004; Barreda et al., 2012; Vajda and Bercovici, 2012). The role of vege- sediment accumulated, having been eroded from the Antarctic Peninsula tation in latest Cretaceous climates has also been explored in modelling volcanic arc immediately to the west (Hathway, 2000; Crame et al., studies (Upchurch et al., 1998, 1999; Hunter et al., 2008), however the 2004; Olivero et al., 2008). Partial inversion of the northern Larsen effectiveness of global climate models in deriving Cretaceous conditions Basin during the Late Cretaceous led to shallow tilting to the southeast, in the high latitudes is somewhat contentious (Craggs et al., 2012). and the basinward progradation of shallow marine facies (Hathway, This study aims at providing the first high-resolution vegetation and 2000). Sediment provenance studies suggest significant volcanic input palaeoclimatic reconstruction for the latest Cretaceous and earliest from the emergent arc, but the intensity of volcanic activity apparently Danian of the high southern palaeolatitudes. Well-preserved spore, decreased during the deposition of the Marambio Group (Pirrie, 1991). pollen and other terrestrial palynomorphs (e.g. algal spores and fungal No evidence for any discrete ash deposits within the López de Bertodano remains) are documented from the López de Bertodano Formation of Formation was found during sedimentary logging. It seems therefore Seymour Island, and assessments made on their likely analogues by unlikely that significant tectonic upheavals or volcanic events occurred comparison with modern palynomorphs. The observed fossil ranges in this region during the Maastrichtian and earliest Danian that could and quantitative abundance data are then used to reconstruct vegeta- have affected the near-offshore palynomorph record. The palaeo- tion types within various habitats on the eastern flank of the Antarctic geography of the Antarctic Peninsula region at this time suggests that Peninsula. Palaeoclimatic trends inferred from changes in these plant the eastern flank of the emergent arc, perhaps tens of kilometres to associations through time are consistent with cool to warm temperate the west of what is now Seymour Island, was the only potential climates and humid to super-humid conditions on Seymour Island source area for the terrestrially-derived palynomorphs recovered in and the surrounding areas during the Maastrichtian, across the K–Pg this study. boundary and into the earliest Danian. The López de Bertodano Formation comprises ~1000 m of unconsoli- dated silty-clays and clayey-silts and contains no sedimentological evi- fi fl 2. Geological setting dence of signi cant hiatuses (Fig. 2). Dino agellate cyst biostratigraphy, macropalaeontology, magnetostratigraphy, strontium isotope stratigra- – fi The shallow marine López de Bertodano Formation of the Marambio phy and a minor iridium anomaly at the K Pg boundary con dently Group crops out on southern Seymour Island in the James Ross Basin,

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