by Staff Writers
Boulder, CO (SPX) May 14, 2012
Ancient glacial deposits in Norway (snowball Earth-aged Smalfjord and the younger Mortensnes formations) are superbly documented and illustrated in this comprehensive eight-day field guide.
This guide was written specifically for use in the field, and, as authors A.H.N. Rice, Marc B. Edwards, and T.A. Hansen note, "is not necessarily fully understandable without actually being in front of the rocks." However, all readers will find the guide a fascinating peek into a wondrous, ancient Snowball Earth.
The aim of the authors (A.H.N. Rice from the University of Vienna; Marc B. Edwards of Houston, Texas, USA; and T.A. Hansen of Talisman Energy Norge AS) is to provide detailed coverage of both the typical and the atypical lithologies and sedimentary structures in the glacial deposits in Finnmark, northern Norway.
The guide, they note, is not a systematic update on published ideas and interpretations, although this has been done at some outcrops.
Instead, the authors invite readers "to critically evaluate our interpretations in the field and to publish their own ideas."
The area is a treasure-trove of geologic features. Lodgement, banded, deformation, flow and melt-out diamictites derived from gneissic, clastic, and dolomitic sources are described, as well as glaciomarine, proglacial and fluvioglacial sediments.
Outcrops showing glaciotectonic folds, faults, flanking structures, shear-sense criteria (sigma-clasts), fluidized sediments, pro- and sub-glacial channels, iceberg dump structures, ghost clasts, dropstones, ice-crystal molds, and a kettle-hole are included.
The classic glacial striations at Oaibaccanjar'ga are described in detail. Marinoan cap-dolostones overlying the Smalford Formation are also included. More than 60 illustrations complete this guide.
Logistically, Finnmark is easily accessible by airplane and/or car in comparison to other Neoproterozoic glacial successions. Most outcrops are along the roadside or are easily reached by small boats. The book includes information about accommodations and renting small boats, as well as a summary of the natural and local history.
Finnmark lies well north of the Arctic Circle and thus has 24 hours of daylight during the midsummer months. The midnight sun disappears around 28 July in the Tana area, although it remains light throughout the night for a week or more afterward.
However, nighttime temperatures rapidly drop in August, and a ground frost is not unusual in the first week of that month. Better weather is more likely in late June to early July, and this is the recommended time for an excursion.
This excursion was first run as part of the International GeoscienceProgramme (IGCP) 512 "Neoproterozoic Ice Ages" project during the 33rd International Geological Congress, in Oslo, Norway, in 2008.
Individual copies of the field guide may be purchased through The Geological Society of America online bookstore. Neoproterozoic Glacial and Associated Facies in the Tanafjord-Varangerfjord Area, Finnmark, North Norway. By A.H.N. Rice, Marc B. Edwards, and T.A. Hansen. Geological Society of America Field Guide 26.
University of Vienna
Beyond the Ice Age
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