The Stáhpogieddi Formation, sometimes spelled as 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.
Geology The Stáhpogieddi Formation consists of three members, which are as follows, in ascending stratigraphic order (lowest to highest):
Members Lillevannet Member: This member is the oldest member of this formation, and is also the smallest, only being at its thickest. It mainly consists of a quartz conglomerate, which are overlain by medium-grained, gray sandstones and siltstones. The depositional environment has been inferred to be fluvial to shallow-marine in nature.
Indreelva Member; This member is the middle member of this formation, and is the largest member in terms of thickness, coming in at around 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. This is also the main fossiliferous member of the whole formation, containing a wide range of discoidal forms, and was likely deposited in deep-marine environment.
Manndrapselva Member: This member is the youngest member of this formation, and is roughly 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, all deposited in a shallow- to marginal-marine environment. This member also sits on the Ediacaran-Cambrian boundary.
Dating Using Rubidium–strontium dating on samples collected within the Stáhpogieddi Formation and other formations within the area, a minimum age of had been recovered from samples collected at the top of the formation, dating part of the Manndrapselva member to within the early Cambrian period, and is inline with previous Rb-Sr dating studies. The maximum age of had been recovered from the base of the formation, reaffirming assumptions that the majority of the formation is Ediacaran in age.
Paleobiota The Stáhpogieddi Formation contains a myriad of discoidal forms, from Cyclomedusa being the most common form, to others like Ediacaria and Nimbia occlusa. Alongside this, occasional frondose fossils, such as Charnia, are also found within the formation, as well as a collection of organic-walled microfossils and tubular fossils.
Petalonamae
GenusSpeciesLocalityNotesImagesCharnia Charnia sp.Indreelva MemberFrondose organism. Two distinct fossils are known, referred to as the "Blåberget" Charnia and "Kommagnes" Charnia.Swartpuntia (?) Swartpuntia (?) sp.Indreelva MemberFrondose organism. Tentatively assigned to Swartpuntia, although some researchers think this is unlikely.
Cnidarian
GenusSpeciesLocalityNotesImagesEdiacaria (?)Ediacaria(?) sp.Indreelva MemberDiscoid organism, tentative assignment.
incertae sedis
GenusSpeciesLocalityNotesImagesAnulitubusA. formosusIndreelva MemberTubular organism.ConiculusC. elegantisIndreelva MemberTubular organism.SilicofistulaS. crenulataIndreelva MemberTubular organism. Previously referred to as Fistula, although the generic name had already been used by Moerch, (1853) for an extant mollusk, as such the new correct name Silicofistula was made.AspidellaAspidella sp.Indreelva MemberDiscoid organism.CyclomedusaCyclomedusa sp.Indreelva MemberDiscoid organism.HiemaloraHiemalora sp.Indreelva MemberDiscoid organism, possibly holdfasts of petalonamids. Nimbia (?)N. occlusa (?)Indreelva MemberDiscoid organism, tentative assignment.PalaeopascichnusP. linearis P. delicatus P. gracilisLillevannet - Indreelva Transition, and Manndrapselva MemberPalaeopascichnid organism. IntritesI. punctatusManndrapselva MemberPalaeopascichnid organism. VendotaeniaV. antiqua Vendotaenia sp.Indreelva MemberRibbon-like organisms. HarlaniellaH. podolicaManndrapselva MemberSegmented, ribbon-like organisms.
Flora
GenusSpeciesLocalityNotesImagesBeltanellaBeltanella sp.Indreelva MemberCyanobacterial colony, now a junior synonym of Beltanelliformis.BeltanelliformisBeltanelliformis sp.Indreelva MemberCyanobacterial colony.
Microfossils
GenusSpeciesLocalityNotesImagesLagoenaforma L. collarisIndreelva MemberOrganic-walled microfossils.Granomarginata G. prima G. squamaceaIndreelva MemberAcritarch.Symplassosphaeridium Symplassosphaeridium sp.Indreelva MemberAcritarch.Leiosphaeridia L. crassa L. jacuticaIndreelva MemberLeiosphaerid Acritarch.Leiosphaerid LeiosphaeridIndreelva MemberLeiosphaerid with a large opening.Sphaeromorph SphaeromorphIndreelva MemberSphaeromorph with a broken vesicle.
Ichnogenera
GenusSpeciesLocalityNotesImagesArenicolitesArenicolites sp.Indreelva MemberBurrows.Planolites-like trace fossils ???Manndrapselva MemberBurrows and trace fossils similar to the ichnotaxon Planolites.SkolithosSkolithos sp.Indreelva MemberBurrows.GordiaGordia sp.Manndrapselva MemberBurrows.CochlichnusCochlichnus sp.Manndrapselva MemberBurrows.HelicolithusHelicolithus sp.Manndrapselva MemberBurrows.BelorhapheBelorhaphe sp.Manndrapselva MemberBurrows.CurvolithusCurvolithus sp.Manndrapselva MemberBurrows.
Undescribed
GenusSpeciesLocalityNotesImagesCandidate frond ???Indreelva MemberFrondose fossil, potentially a member of the arboreomorph, although poor preservation precludes proper identification.TSGF 18953 ???Indreelva MemberFrondose, dumbbell shaped fossil, bears similarities to Primocandelabrum, although poor preservation precludes proper identification.Form C ???Indreelva MemberOrganic-walled microfossil.
See also
List of fossiliferous stratigraphic units in Norway
References