|Boundary between well bedded sandstones and shales of the pre-Neoproterozoic glacial Veinesbotn Formation (tilted gently to the left which is to the north) and the more massive diamictites and conglomerates at the base of the glacial Smalfjord Formation (ca. 640 Ma old), forming the main cliff above. Western end of Vieranjar’ga, W. Varangerbotn. The excursion will be visiting these outcrops by boat, from Grasbakken. Photo: A. Hugh N. Rice, Vienna|
Scientific Outline and General Schedule: The aim is to give the participants an insight into as wide a range of geology as possible, within the remit of the excursion title, promoting a fruitful exchange of ideas through comparisons with other regions visited by the participants.
The days described below will also include stops at suitable roadside outcrops/viewing points. The order in which the days are done will depend on the weather, especially those involving boat journeys, and participant's wishes. Essentially, the itinerary will remain flexible, such that outcrops not scheduled in the guide can be visited if the discussions take us that way and the participants so wish. Each day will finish with a discussion session, sometimes around a campfire, by the light of the midnight sun.
In the following text, the terms Bitter Springs, Sturtian, Marinoan and Gaskiers have been used to identify 'events', the significance and temporal equivalence world-wide of some of which have not been fully demonstrated and the usage of which may not be universally accepted. This is simply to save space. See Halverson et al. (2005; Bull. Geol. Soc. Am.) for an outline on how E. Finnmark may fit into the overall Neoproterozoic picture.
The tour itinerary will be available visually on a dedicated website in the spring of 2008. Updates to the field-trip will be posted on http://www.igcp512.com/ and http://www.snowballearth.org/.
The order of the days is not fixed; they are both weather and tide dependent.
Day 01 (29th July): Arrival in Kirkenes, preferably with everybody on the same flight. Drive to accommodation in Seida. Evening presentation at Seida School.
Day 02 (30th July): Handelsneset. Smalfjord and Nyborg Formations. At Handelsneset, four adjacent outcrops, consisting of a variety of Smalfjord Formation facies resting unconformably above the Vadsø Group (Klubbnasen and Fugleberget Formations), will be investigated. We shall begin at the western end of the outcrop, where we can walk along the contact and observe coarse-grained sandstones and conglomerates, poorly stratified, with granitic boulders and large blocks of deformed Smalfjord Formation sediment. These are interpreted as ice-contact deposits. Following the unconformity toward the east, we encounter conglomerates with excellent sorting and rounded clasts that may represent beach deposits. Further along are conglomeratic sandstones arranged into steep foresets prograding to the west. These are interpreted to be delta foresets. Afterwards, we will visit strongly folded interbedded red shales/silts and thin dolomicrites, passing up to edgewise-breccias. This is the basal member of the Nyborg Formation, a clastic-rich cap-dolostone. If time, we will also visit the base of the Nyborg Formation at Hammarnes, where both interbeddded clastic/dolostone and massive dolostones crop out.
Day 03 (31th July): Karlebotn. Smalfjord Formation. From Karlebotn we will walk along the coast to Oaibaccanjar'ga (Bigganjar'ga), where sandstones of the Veidnesbotn Formation underlie ca. 3 m of melt-out till of the Smalfjord Formation (Reusch's moraine). Sub-glacial bedrock melting during striation formation has been documented here. The till was draped by ca. 100 m of sandstones and shales, locally with soft-sediment structures, and diamictites of the Smalfjord Formation. After walking back to Karlebotn, other basement-cover contacts defining the north and south sides of the Varanger Palaeovalley in the Karlebotn area will be examined. We will then drive north, to see the thin stromatolitic basal dolostone of the Smalfjord Formation at Leirpollen.
Day 04 (1st August): Digermul. Mortensnes Formation. We will take a long boat ride from Torhop to the south side of the Digermul Peninsula, near Stappogiedde to see the remote but dramatic exposures of tidally deposited Nyborg Formation (to show that most of the Nyborg is not deep water) and also to see the superb deformation structures in the exposures of subglacial Mortensnes Formation along the coast. The thin overlying section of post-glacial Lillevatn Member will also be visited. Most of the day will be spent in the boat as this gives the best opportunity to see the rocks, with a few trips on-shore. (This day is totally weather dependent.)
Sharp but curved erosional boundary between white to medium-grey sandstones of the pre-Neoproterozoic glacial Veinesbotn Formation and the more massive pink-buff brown sandstones with occasional outsize clasts, forming the base of the glacial Smalfjord Formation (ca. 640 Ma old). The hammer is on the upper part of the Veinesbotn Formation. East end of Skjåholm, Varangerbotn. The excursion will be visiting these outcrops by boat, from Grasbakken.
Photo: A. Hugh N. Rice, Vienna
Close-up of a glacially formed striation in the pre-glacial
Veinesbotn Formation, at the base of the Neoproterozoic
Smalfjord Formation (ca. 640 Ma old) in Varangerfjord.
Detailed examination of the polished rock in the striation
indicates that the underlying quartzitic sandstone melted
during a short period of very rapid movement by the
glacier. The overlying rock is a tillite (a glacially formed sedimentary rock). (10Kr coin for scale.)
Photo: A. Hugh N. Rice, Vienna
|Day 05 (2nd August): Vestertana. Smalfjord Formation. From Torhop, Tanafjord, we will make a short boat trip to Gaessenjarg'ga and spend the whole day examining the best exposures of the upper part of the Smalfjord Formation, over several kilometres along strike. At the simplest level, tillites and mudstones reflect lodgement tillite facies alternating with glaciomarine deposits. The contacts between the tillites and finer sediments show a wide range of deformation structures, indicating the variable ice-movement directions and the effects of successive diamictites mixing with the underlying deposits. The finer grained sediments represent gravity flows, turbidites and deposition from suspension, including dropstones. Along this outcrop we can also see the gentle angular unconformity between the Smalfjord Formation and the underlying Tanafjord Group.
Day 06 (3rd August): Varangerfjord. Smalfjord Formation. From Grasbakken, S. Varangerfjord, we will make a short boat trip to the NE end of Veines, where there are several hundred metres of continuous exposure of the base of the Smalfjord Formation. Up to 20 m of sandstones and conglomerates both conformably and erosively overlie diamictites, which in turn unconformably/erosively overlie sandstones of the Veidnesbotn Formation (Tanafjord/Vadsø Group). Both subglacial and supraglacia/proglacial diamictites are present. The sequence also shows channelling, winnowing of deposits, sand wedges, turbidites, fluvial channel deposits, marine sandstones, sediment gravity flows and overlying braided stream deposits. After this we will go by boat to Skjåholm, where the markedly irregular unconformity between diamictites and fluvio-glacial deposits at the base of the Smalfjord Formation and sandstones of the Veidnesbotn Formation (Tanafjord or Vadsø Group) is well exposed. We will then boat back to Grasbakken. (This day is totally weather dependent.)
Green-blue clast of probable Archean aged
rock (>2,500 million years old) within reddish
laminated shales of the ca. 640 Ma old
Smalfjord Formation. The reddish shales are
of glaciomarine origin, formed by fine-grained sediment released during melting of ice which
was floating in the sea. When the ice melted around the larger clast, it fell into and cut
through the layering in the unconsolidated red shales, as a so-called drop stone. Gaessenjar’ga, south end of Tanafjord; the excursion will be visiting this outcrop by boat from Torhop.
Photo: A. Hugh N. Rice, Vienna
Day 07 (4th August): Persfjord. Båtsfjord Formation. A long, but scenic drive to examine the Båtsfjord Formation (Barents Sea Group), at Persfjord, on the north side of the Trollfjorden-Komagelva Fault. This unit, which is a mixed clastic-carbonate tidal sequence from which only negative d13C values (ca. -4‰) have been obtained, comprises a stromatolitic carbonate and shale tidal succession (Annijokka Member) overlain by up to 1.3 km of violet-green mudstones, pale sandstones and buff to black dolostone (Hestmann Member), representing a shallow marine environment. The formation, which predates the 1.5 km thick, sub-Marinoan, Tanafjord Group and has abundant molar-tooth structures is a possible correlative of the Bitter Springs Anomaly. On the way, other pre-Smalfjord Formation clastic sediments, especially the Lille Molvika Formation (Ekkerøya Group) will be examined. This formation is <200 m thick but is over and underlain by unconformities, one of which may be 'correlative' to the Sturtian event.
Day 08 (5th August): Departure Kirkenes. Drive to Kirkenes early in the morning.
Bad-weather day: Laksefjordvidda-Giilasjokka. Base of Nyborg Formation, Mortensnes Formation. The first part of the day will examine the cap-dolostone above the Smalfjord Formation, forming the base of the Nyborg Formation. This shows very rapid along-strike lithological changes, with an overall gradual drift from a thick massive, typical Marinoan cap-dolostone (sheet cracks, d13C -4‰ VPDB) with an erosional upper surface, to a clastic dominated sequence with rare carbonate-rich layers, over a horizontal distance of a few kilometres. As we traverse the Nyborg Formation, we will have an opportunity to observe the turbidite sandstone packages that comprise much of the central part of this unit. At the end of the day, we will traverse along the Mortensnes Formation, examining a variety of superb subglacial-subaqueous structures formed by the decoupling or lifting of grounded ice to floating ice. (In the event of bad weather hindering the boat-dependent days.)