Throughout most of the Tertiary (~65 Ma to ~3 Ma), forests have thrived north of the Arctic Circle. These unique ecosystems were subject to prolonged periods of continuous darkness and light each year, yet managed to persist through the major climate transitions of the Eocene, Oligocene, and Miocene. Much is known about the fossil forests of Arctic North America from studies of Paleocene (e.g., Chickaloon, Alaska), early Eocene(e.g., Ellesmere Island), middle Eocene (e.g., Axel Heiberg Island), and Miocene (e.g., Banks Island) terrestrial sediments. Previous NSF-funded work has supported our reconstructions of seasonal precipitation (Schubert et al., 2012), relative humidity (Jahren and Sternberg, 2003, 2008), the isotopic composition of environmental water (Jahren et al., 2009), soil-methane production (Jahren et al., 2004), and possible water transport mechanisms (Jahren and Sternberg, 2002) using stable isotope analyses of plant fossil materials from the Eocene sediments of Arctic Canada. Russian literature from the 1970s and 80s described the Miocene sediments of Siberia as temporally extensive and spectacularly rich in fossil forests, however, they have not yet been examined using stable isotope techniques. In this proposal, we describe our plan to collect, archive, and analyze Pinaceae and Taxodiaceae fossils from the Baekovo and Nekkeiveem floras, located in the Kolyma River Basin of northeastern Siberia. The sediments we will sample are part of the Khapchan Formation which is late Miocene in age (11.6 to 5.3 Ma; Nikitin, 2007); we will perform one season of fieldwork as part of the Polaris Project II, a recently funded NSF research and education initiative under the direction of Dr. R.M. Holmes (WHRC; see letter of support within Supplementary Documents) to study transport and transformation of carbon in rivers flowing into the Arctic Ocean. As part of Polaris II, we will receive assistance with visas, export permission, and housing at the Northeast Science Station near Cherskiy, as well as the use of an existing boat charter scheduled to navigate the Kolyma River Basin (contact: Dr. Sergei Zimov). We will employ our recent innovations in microanalysis of intra-ring ä13C profiles (Schubert and Jahren, 2011) for determination of the seasonal timing of precipitation (Schubert et al., 2012) for the Miocene Arctic forests of northeastern Siberia. This proposal represents a significant revision of the proposal approved for funding, as necessitated by the >50% reduction in the level of funding, and the restriction of time to two years of total funding. The main alteration of the scientific goals within the original proposal is the exclusion of oxygen isotope analyses of recovered fossil material that were proposed in the original version. In the event that further funding becomes available, collected fossil may be analyzed for oxygen isotope composition, and our hypotheses about paleorelative humidity can be tested under separate support at a later date. The budget has also been altered in that PI Brian Schubert is now an Assistant Professor at University of Louisiana at Lafayette; what would have been postdoc salary to him has been redirected into two months of his summer salary within a subcontract to ULL.
The Intellectual Merit of this study is its potential to open up new intellectual territory on Tertiary Arctic forests via the Miocene sediments of Northeastern Siberia. Fundamentally, we are interested to learn whether the climate scenarios we have constructed for the Canadian Arctic Eocene were global and long-standing, or limited to the Western Hemisphere and/or to the Paleogene. We hypothesize that a general attribute of Tertiary Arctic forests is a summer-dominated hydrologic regime where maximum light levels and maximum water availability coincide, similar to what we observed for the Eocene forests of Arctic North America. We propose a first test of this hypothesis as the determination of the seasonal precipitation regime within Miocene Arctic forests using stable isotope analyses of fossils from the Kolyma River Basin. The Broader Impacts As part of the Polaris II field seasons, we will provide two educational modules introducing students to the Tertiary Arctic forests including hands-on exercises to define simple stratigraphy and collection/identification of plant fossils. Our module will form a separate blog on the website documenting the evolution of the Polaris Project since its inception in 2008 (www.thepolarisproject.org/journals/blog/). Finally, we note that our research at the University of Hawaii serves the State of Hawaii, an EPSCoR state. The EPSCoR program is designed to broadly impact science capabilities in EPSCoR jurisdictions, and coinvests with NSF Directorates and Offices in support of proposals submitted to the Foundation's research and education programs, and crosscutting initiatives.
