 |
| Titel |
Do biosiliceous laminated sediments reveal sea ice seasonality in the middle Eocene Arctic Ocean? |
| VerfasserIn |
C. E. Stickley, N. Koc, R. B. Pearce, A. E. S. Kemp |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020412
|
|
|
|
|
|
| Zusammenfassung |
| We present initial microfabric analyses of finely laminated middle Eocene biosiliceous
sediments from the IODP Expedition 302 “ACEX” cores (central Arctic, Lomonosov Ridge).
Backscattered electron imagery (BSEI) of polished thin sections and scanning electron
microscope secondary electron imagery (SEI) of lamina-parallel fracture surfaces are used to
analyse the laminations in 2 short intervals dated at approximately 46 Ma. Our data offer
insight into the cryospheric history of the central Arctic from a siliceous microfossil
perspective during a significant phase in Cenozoic climate evolution—the start
of the transition from a greenhouse to an icehouse world. Importantly, the BSEI
technique offers the detail of information which can not be achieved by bulk sediment
analysis.
These organic-rich sediments, deposited under an anoxic benthic environment, are also
rich in heavily silicified endemic marine to brackish (diatoms, ebridians, silicoflagellates) and
in situ freshwater (chrysophyte cysts) siliceous microfossils. They also contain the weakly
silicified needle-like diatom Synedropsis spp., an indicator of sea ice and the world’s oldest
known fossil record of sea ice dwelling diatoms (Stickley et al., in press; Stickley and Koc,
Session CL33 this conference). Their presence highlights an exceptional preservational
environment along the Lomonosov Ridge at this time. Synedropsis spp. show the Arctic
Ocean supported sea ice-based life from 47 Ma, yet episodes of melting must have
occurred to allow their preservation in the sediments. Initial investigations indicate
Synedropsis spp. form mono-specific laminations or elongate lenses of, on average, 25 |
|
|
|
|
|
|