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Variability in the length of the sea ice season in the middle Eocene Arctic

Catherine E. Stickley, Nalan Koc, Richard B. Pearce, Alan E. S. Kemp, Richard W. Jordan, Francesca Sangiorgi and Kristen St. John
Variability in the length of the sea ice season in the middle Eocene Arctic
Geology (Boulder) (June 2012) 40 (8): 727-730


Finely laminated Middle Eocene sediments from the central Arctic contain high abundances of the delicate, sea ice-dwelling fossil diatoms Synedropsis spp. and sea ice-rafted debris (sea ice-IRD), establishing an offshore seasonal sea ice regime ca. 47 Ma. Synedropsis spp. co-occur with other diatom taxa and microfossils requiring open water. This strongly indicates seasonality; nonetheless, seasonal reconstruction of the flux cycle cannot be resolved by standard bulk-sediment analysis, which destroys sedimentary fabrics and averages data within samples. Here we resolve and reconstruct seasonal-scale flux events from these sediments using backscattered electron imagery (BSEI) of resin-embedded sediment, a nondestructive technique that preserves the integrity of sedimentary microfabrics, thus revealing discrete productivity-flux events at ultrahigh (e.g., <30 mu m) resolution. Seasonality is expressed at the submillimeter scale by successions of discrete mono-specific laminae and micro-lenses of Synedropsis spp., terrigenous material (sea ice-IRD), and open-water taxa, indicating that first-year ice existed in the central Arctic. Further, BSEI reveals millimeter-scale alternation of bundles of laminae and microlenses of two distinct types: one characterized by Synedropsis spp. and terrigenous material, the other by mainly open-water taxa and little terrigenous material. The sedimentation rate and preliminary assessment of annual cycles indicate suborbital variability on the order of multi-decadal to centennial duration; we argue that this reflects variations in the sea ice-season length.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 40
Serial Issue: 8
Title: Variability in the length of the sea ice season in the middle Eocene Arctic
Affiliation: University of Tromso, Department of Geology, Tromso, Norway
Pages: 727-730
Published: 20120615
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 22
Accession Number: 2012-065559
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2012201; accessed on July 5, 2012
Illustration Description: illus.
Source Medium: WWW
N87°50'60" - N87°55'60", E136°10'00" - E139°33'00"
Secondary Affiliation: Norwegian Polar Institute, NOR, NorwayUniversity of Southampton, GBR, United KingdomYamagata University, JPN, JapanUtrecht University, NLD, NetherlandsJames Madison University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201234
Program Name: IODPIntegrated Ocean Drilling Program
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