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The Last Interglacial Stage: Definitions and Marine Highstand, North Quaternary International xxx (2014) 1e16 Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint The Last Interglacial Stage: Definitions and marine highstand, North America and Eurasia Ervin G. Otvos Department of Coastal Sciences, University of Southern Mississippi, Ocean Springs, MS 39566, USA article info abstract Article history: Delineation of the boundary between the Last Interglacial (LIG) and the last (Wisconsinan) Glacial Stage Available online xxx in North America represents a critical, yet unresolved issue. Subdivisions of the late Pleistocene are based on oxygen isotope, ice cover, and pollen stratigraphic data. Boundaries defined by isotope chro- Keywords: nology hinge on complex interrelationships between d18O in foraminifer tests, ice volumes stored on Last Interglacial and early Last Glacial land, and coeval sea-level position. In the absence of adequate pollen-stratigraphic documentation, delineations Pleistocene subdivision boundaries were harder to establish in North America than in Europe. Time- Sangamon stage and Geosol definition transgressive pollen zones revealed increased lengths of the climatically-floristically defined LIG from LIG coastal highstand deposits fl fi “ ” Pleistocene pollen stratigraphy the European subarctic to the Mediterranean. Con icting de nitions of Sangamon, as representing fi “ ” Late Pleistocene climate history only the last interglacial of minimum ice cover and higher temperatures or broadly de ned, sensu lato, also incorporating early part of the Last (Wisconsinan) Glacial Stage persist in the North American literature. The exclusively interglacial age of the Sangamon Geosol, originally used in dating the San- gamonian Stage proved untenable. Designation of an “Eowisconsinan” interval corresponding to Susb- tages MIS 5d-a also lacks merit. Despite climate- and vegetation-related discrepancies, pollen- and coastal deposit-based comparisons between Europe and North America during MIS 5 and the Holocene are useful in establishing the climate history of the North American Sangamonian and subsequent early Wisconsinan substages. An overarching MIS 5 cooling trend represented by scattered subarctic and high- mountain ice accumulation events followed the MIS 5e EemianeSangamonian temperature peak. Adoption of the general European practice that asymmetrically splits MIS 5 into a short MIS 5e inter- glacial and a long early Wisconsinan Glacial (MIS 5d-a) interval is preferred in North America as well. Subdivisions in the normalized d18O curve that serve as the chronological framework and the wealth of European pollen data support this approach. While multiple pre-Sangamon Pleistocene marine-paralic intervals do occur on the NW Gulf coast, all pre-Sangamon Pleistocene marine and brackish-inshore deposits had been removed by erosion in the NE coastal plain. A single inshore-nearshore marine sediment and highstand interval is well-documented in this region. The LIG highstand sequence cor- relates with varied Eemian marine and paralic MIS 5e deposits encountered along northern and western European, Siberian, and additional shores. Apart from reliably dated Sangamonian S Florida coral reefs, identification and dating of LIG highstand deposits remain highly problematical in SE Atlantic shore terraces. © 2014 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction the Interglacial and the following early Glacial similar to those that existed between the LIG and Holocene may be applicable in Following its first recognition in late Pleistocene Netherlands considering possible future climate changes. In contrast with the deposits in the mid-19th century, the Last Interglacial Stage (LIG) scarcity of North American MIS 5 pollen data, a large body of became an important research field for Quaternary geologists European palynological record helps the redefinition of chro- and paleoclimatologists. Some of the similarities and differences nostratigraphic subdivisions and inter-regional correlations on between climate and vegetation between the warming phase of this side of the Atlantic. Drawing a firm stratigraphic division between the Last Interglacial and the cold, locally glacial climate conditions of the subsequent Wisconsin Glacial Stage represents a major challenge. Use of European interglacial-glacial pollen E-mail address: [email protected] http://dx.doi.org/10.1016/j.quaint.2014.05.010 1040-6182/© 2014 Elsevier Ltd and INQUA. All rights reserved. Please cite this article in press as: Otvos, E.G., The Last Interglacial Stage: Definitions and marine highstand, North America and Eurasia, Quaternary International (2014), http://dx.doi.org/10.1016/j.quaint.2014.05.010 2 E.G. Otvos / Quaternary International xxx (2014) 1e16 successions contributes to the resolution of the long-standing 3. The Last Interglacial e chronological definitions and North American paradox, the assumed presence of cold sub- climate history stages within the LIG. Most non-glacial deposits, that in the past have been attributed to the LIG in North America consist of 3.1. European nomenclature eolian, fluvial, coastal sediments, and a major paleosol entity. Highlighting this controversy, the present suggestions propose Deposits of the LIG were described first on the small Eem (Amer) streamlining the “Sangamon” terminology to create a much River near Amersfoort, central Netherlands. In the mid-19th cen- needed reliably established conformity between the North tury Professor P. Harting designated a fossiliferous transgressive American and European use of the LIG and early Wisconsinan and highstand sequence here as the Eem Formation, associated climate phases. Identification of LIG lithosomes within the Plio- with the Eemian Interglacial Stage (Zagwijn, 1961, 1989, 1996; ceneePleistocene terrace complex in the SE Atlantic coastal plain Seidenkrantz and Knudsen, 1994, 1997; Bosch et al., 2000; (Cooke, 1945) remains a major challenge. Only few S. Florida Cleveringa et al., 2000). The corresponding pollen section was interglacial deposits were dated satisfactorily and the interglacial chosen as stratotype. Replacing local terminologies such as the identity of other coastal plain units remains unclear. The single Riss-Würm Interglacial established in central Europe over a century LIG transgressive-regressive, paralic-to-marine Pleistocene sedi- ago (Penck and Brückner, 1909), since the 1970s the designation ment sequence in the NE Gulf coastal plain provides a useful Eemian spread well beyond Europe to be applied among other re- reference interval in correlating with Eemian Interglacial high- gions, to regions such as Anatolia, Turkey (Shumilovskikh et al., stand units in the global context. 2013), Greenland (Funder et al., 2011), Siberia, and Mongolia (Sheinkman, 2011, Table 1). 2. Methods 3.2. Eemian-Sangamonian Interglacial as defined by isotope This paper is based on research of European and north American chronology and vegetation literature, including recent publications that deal with the Last Interglacial (LIG) and Last Glacial stage. Pertinent publications were Retaining its North American “Sangamonian” chronostrati- selected from a voluminous literature that cover German, graphic designation for the last interglacial, Emiliani (1955, 1971) Scandinavian-Baltic, west European and other sites that yielded dated MIS 5 between 132 and 103 ka. He deemed by sensu lato detailed pollen documentation. The extensive literature search definition the Stage coeval with the previously established Sanga- involved coastal, glacial, and paleopedological topics that encom- monian Stage. Corresponding to MIS 5, “warm isotope stage,” is passed the late Pleistocene of North America and several regions applied to the much longer MIS 11 isotope interval of ~64 ka worldwide. As defined by the recovered pollen spectra, the lengths duration. In terms of the underlying astronomical parameters, part of interglacial and glacial chronostratigraphic units vary according of this period resembled the Holocene, MIS 1 to a greater degree to geographic position, altitude and numerous other factors. than it did MIS 5. MIS 11 was “a period of reduced global ice vol- Influenced by uncertainties in defining isotope substage bound- umes.” Following the prolonged MIS 11c Interglacial, four stadials aries, the relationship between d18O values in calcareous fossils, occurred during MIS 11b and 11a (Olson and Hearty, 2009; Candy et continental ice volumes, and sea-level fluctuations is non-linear al., 2014; Blain et al., 2014). and complex. Isotope stage and substage boundaries do not The literature defines interglacials as long periods of minimal conform to the time-transgressive vegetation zones. The precision global ice cover and stadials that usually precede and follow them, by which marine isotope stage and substage boundaries may be as shorter intervals of significant continental ice sheets and glacier established is variable. expansion. However, a vegetation-based interglacial definition, Isotope-based time divisions, stadials and interstadials do not based strictly on increased tree pollen/grass and shrub pollen ratios always reflect ice volume-related sea-level changes. Even when ice (e,g., Turner, 1970) is applicable only to temperate west- and central volumes stored on the continents remain stable, ocean waters and European interglacials, not to the adjacent boreal-subarctic, biogenic carbonate matter in fossils may still be 18O-enriched respectively warm Mediterranean climate belts. For various rea- (Bradley,
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