Stappogiedde Formation

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Stappogiedde Formation
Stratigraphic range: Ediacaran - Cambrian 560–530  Ma [1]
Type Formation
Unit of Vestertana Group
Sub-unitsManndraperelv, Innerelv and Lillevatn Members [2]
Underlies Breivik Formation
Overlies Mortensnes Formation
Thickness505–530 metres (1,657–1,739 ft)
Lithology
Primary Sandstone
Other Shale, Conglomerate, Quartzite, Mudstone, Greywacke
Location
Country Norway

The Stappogiedde Formation is a geologic formation in Norway, which spans from the late Ediacaran into the early Cambrian, and also preserves fossils dated to the Ediacaran period.

Contents

Geology

The Stappogeidde Formation consists of three members, which are as follows, from the topmost member to the basal most member:

Manndraperelv Member

The Manndraperelv Member is the youngest member of this formation, and is roughly 190 metres (620 ft) at its thickest, and mainly consists of coarse-grained, red quartzite sandstones and conglomerate, which is interbedded with greywacke and mudstone. The lower strata of this member contains occasional Ichnotaxon, which have been noted to be similar to Planolites , and also contains the agglutinated organism, Palaeopascichnus . [2] [3]

Innerelv Member

The Innerelv Member is the middle member of this formation, and is the largest member in terms of thickness, coming in at around 275–300 metres (902–984 ft) thick. Near the base of this member, it mainly consists of green to red shales, which contain occasional interbedded fine-grained, red sandstones. Towards and into the middle, the shales become a more greenish-grey colour, with fine-grained cross-laminated sandstones. At the top of the member, the fine-grained sandstones give way to much thicker interbedded medium to coarse, parallel-laminated sandstone. In exposed areas, the sandstone features rippled tops, and their orientation suggest a southwestern palaeocurrent at the time of deposition. In non-exposed areas, this layer is overlain by a top-most layer of greenish-grey, parallel-laminated siltstones, which are interbedded with fine-grained, ripple-marked sandstone. [2]

This is also the main fossiliferous member of the whole formation, containing a wide range of discoidal forms. [2]

Lillevatn Member

The Lillevatn Member is the oldest member of this formation, and is also the smallest, only being 40 metres (130 ft) at its thickest. It mainly consists of a quartz conglomerate, which are overlain by medium-grained, gray sandstones. [2]

Dating

Using Rubidium–strontium dating on samples collected within the Stappogiedde Formation and other formations within the area, a minimum age of 530±0  Ma had been recovered from samples collected at the top of the formation, dating part of the Manndraperelv member to within the early Cambrian period, and is inline with previous Rb-Sr dating studies. [4] The maximum age of 560±0  Ma had been recovered from the base of the formation, reaffirming assumptions that the majority of the formation is Ediacaran in age. [1]

Paleobiota

The Stappogiedde Formation contains a myriad of discoidal forms, from Cyclomedusa being the most common form, to others like Ediacaria and Nimbia occlusa . [2]

Genera that are not found within the main fossiliferous Innerelv member will be noted as such.

Color key
Taxon Reclassified taxonTaxon falsely reported as presentDubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Cnidarian

GenusSpeciesNotesImages
Ediacaria (?) [2]
  • Ediacaria sp. (?)
Discoid organism, tentative assignment.
Ediacaria (35159560925).jpg

incertae sedis

GenusSpeciesNotesImages
Cyclomedusa [2]
  • Cyclomedusa sp.
Discoid organism.
Cyclomedusa.jpg
Hiemalora [2]
  • Hiemalora sp.
Discoid organism, possibly holdfasts of petalonamids.
Hiemalora stellaris.jpg
Nimbia (?) [2]
  • N. occlusa (?)
Discoid organism, tentative assignment.
Nimbia.jpg
Palaeopascichnus [3]
  • P. delicatus
Palaeopascichnid organism, found in the Manndraperelv member.
Palaeopascichnus CU21.png
Vendotaenia [3]
  • Vendotaenia sp.
Ribbon-like organisms.
Vendotaenid indet.jpg

Flora

GenusSpeciesNotesImages
Beltanella [2]
  • Beltanella sp.
Cyanobacterial colony, now a junior synonym of Beltanelliformis.
Beltanelliformis
  • Beltanelliformis sp.
Cyanobacterial colony.
Anthozoa - Nemiana simplex.JPG

Ichnogenera

GenusSpeciesNotesImages
Arenicolites [2]
  • Arenicolites isp.
Burrows.
Planolites -like trace fossils [2]
  • ???
Burrows and trace fossils similar to the ichnotaxon Planolites from the Manndraperelv member.
Planolites.jpg
Skolithos [2]
  • Skolithos isp.
Burrows.
Skolithos.jpg


See also

References

  1. 1 2 Gorokhov, I. M.; Siedlecka, A.; Roberts, D.; Melnikov, N. N.; Turchenko, T. L. (September 2001). "Rb–Sr dating of diagenetic illite in Neoproterozoic shales, Varanger Peninsula, northern Norway". Geological Magazine. 138 (5): 541–562. doi:10.1017/S001675680100574X.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Farmer, J.; Vidal, G.; Moczydłowska, M.; Strauss, H.; Ahlberg, P.; Siedlecka, A. (March 1992). "Ediacaran fossils from the Innerelv Member (late Proterozoic) of the Tanafjorden area, northeastern Finnmark". Geological Magazine. 129 (2): 181–195. doi:10.1017/S001675680000827X.
  3. 1 2 3 Crimes, T. P.; McILROY, D. (November 1999). "A biota of Ediacaran aspect from lower Cambrian strata on the Digermul Peninsula, Arctic Norway". Geological Magazine. 136 (6): 633–642. doi:10.1017/S0016756899003179.
  4. ↑ Pringle, I. R. (November 1972). "Rb-Sr age determinations on shales associated with the Varanger Ice Age". Geological Magazine. 109 (6): 465–472. doi:10.1017/S0016756800042734.
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