Linking stratigraphy on the Lomonosov Ridge with standard lithological units of the Amerasia Basin
2007 (English)In: First Conference on Arctic Palaeoclimate and its Extremes (APEX), 2007Conference paper (Other academic)
A lithological classification has been established by Clark et al. (1980), based on cores primarily from the Alpha Ridge, on the Amerasian side of the Arctic Ocean. It has since been applied to correlate sediment cores over large distances, mainly in the Amerasian Basin (Alpha Ridge, Northwind Ridge and Mendeleev Ridge), but also on the Lomonosov Ridge. Over a 310 cm long stratigraphic section, synthesized from 67 cores, 13 units were recognized and named A to M by Clark et al. (1980). An age model was developed for this lithostratigraphy that relied on the identification of the Brunhes-Matuyama paleomagnetic reversal boundary (781 000 years; Lourens et al., 2004) and the assumption of a linear sedimentation rate. However, recent studies have shown that this measured magnetic polarity change represents instead a short-time excursion within the Brunhes chron. We have investigated if it is possible to infer the lithostratigraphy (Units A-M) from the Amerasian Arctic Ocean in cores from the Lomonosov Ridge that in turn have been correlated to cores in the Eurasian Basin. The cores selected for this study were B-8 and B-24 from the LOREX ‘79 ice island drift expedition (Morris et al., 1985), PS2185-6 from the Arctic’91: ARK-VIII/3 expedition with R/V Polarstern (Spielhagen et al., 1997) and 96/12-1pc from the Arctic Ocean 96 expedition with I/B Oden (Jakobsson et al., 2001). Averaged sedimentary proxies (paleomagnetism, grain size, microfossil abundance and lithostratigraphy) from a selected set of T3 cores have been published by Clark et al. (1980) and these have been used in this study to link with the same published proxies for the included Lomonosov Ridge cores. The Lomonosov Ridge cores PS 2185-6 and 96/12-1pc have previously been correlated using paleomagnetic polarity reversals and grain size (Jakobsson et al., 2001) and the lithostratigraphic units A-M were previously inferred in core B-8 by Morris et al. (1985). In our study, the lithostratigraphic units (A to M) could not be inferred in PS2185-6 or 96/12-1pc. However, correlations between the Lomonosov Ridge and Amerasian Basin T3 cores appear to be possible using paleomagnetic and grain size data. More detailed data from the Alpha Ridge sediment stratigraphy would probably enhance our first attempted correlations using these proxies. An additional correlation between the Lomonosov Ridge cores PS2185-6 and 96/12-1pc and piston core HLY0503-18JPC, retrieved from the Lomonosov Ridge during the HOTRAX expedition (2005) with USCGC Healy, has also been made. The grain size data from core HLY0503-18JPC could easily be correlated to the older cores on the Lomonosov Ridge and will hopefully be a good link to the HOTRAX cores taken on the Alpha-Mendeleev Ridge. The correlations made here, imply higher sedimentation rates on the Lomonosov Ridge than on the Alpha Ridge, but not as much higher as previously thought. By establishing a new reliable age model for the Arctic Ocean, earlier studies on Amerasian cores could be viewed from a completely different chronostratigraphic perspective.
Place, publisher, year, edition, pages
IdentifiersURN: urn:nbn:se:su:diva-19507OAI: oai:DiVA.org:su-19507DiVA: diva2:186031