The Höganäs Formation is a Late Triassic to Early Jurassic geologic formation in Skåne, Sweden. The formation is mostly known for its incredible flora collection from the Bjuv member, composed of over 110 species, and also includes several vertebrate remains, such as fishes, amphibians and dinosaur tracks & remains, although none have yet been referred to a specific genus.Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607. It´s regional equivalent is the Zagaje Formation in Poland.
Description
The Höganas Formation was deposited in what is now the southern part of Sweden Skåne. The formation straddles the Triassic-Jurassic boundary and has provided evidence of widespread mire-forest deterioration that began in the latest Rhaetian.Petersen & Lindström, 2012, p.8 The upper part of the Höganas Formation is correlated with the Rønne Formation of Bornholm, which is administered by Denmark. The Hóganas Formation is rich in coal and has provided many fossil flora.Petersen & Lindström, 2012, p.9
Vallåkra Member This member represent the basal part of the Formation, that represents a transition between the terrestrial Kågeröd Formation and the delta dominated coal layers of the Bjuv Member, being made by poorly stratified clay & claystone, mostly green in coloration. The sediments of this member are exposed mostly in the quarry of the town of the same name, where is subdivided on the next levels: 6 m of mixed layers, whose composition includes material seen both on the Kågeröd Formation and this member (red clay and 5 m light clay, 3 m argillaceous sandstone and l m dark clay and several layers composed by Spherosiderite). The uppermost levels are covered by the coal seams of the Bjuv Member. This member has been considered as of Middle and Upper Rhaetian in age.
Bjuv Member
The second member is the Bjuv Member, known as the most fossiliferous one, that was known originally as the Gruv Member (gruva= mine). Coal and clay have been mined in this area since the fifteenth century, being this intensive mining one of the main reasons the fossiliferous layers have provided such a diverse flora. The Bjuv member is divided on two different seams, the B seam, that overlies the older member and the A seam, that marks the limit with the Helsingborg Member. This layer has a thickness of around 37.22 and 45.72 m in bore No. 256 (stored at the Höganäs Company in Bjuv) from the Bjuv area. The layer is dominated by coarse arenaceous sediments, specially between Billesholm and Höganäs, parallel to the Söderåsen and Kullaberg horsts. Towards the southern part of this area the deposition changes, with an increased abundance of argillaceous contents, specially at places like Skromberga. The age of this member is considered to be Latest Rhaetian and maybe Lower Hettangian. Thus the member records the Triassic–Jurassic extinction, what is seen in the plant oscillations. The Plant fossils found at this layer are one of the main fossil material of the whole Mesozoic in Sweden, composed by more than 110 species, one of the most complete floras of the same age from any location. The main reason for this datation where suggested due to the presence of the plants Lepidopteris ottonis and Thaumatopteris shenki, as well palynological samples that suggested a Middle Rhaetian age (the Rhaetipollis-Limbosporites Miospore Zone). Latter works have fount that the Dinosaur Footprint layers spam between the Rhaetian-Hettangian boundary. Beyond the exceptional flora, the member is also known for fossils of Molluscs, arthropods and fish remains. In the uppermost sequence the deposition changes from a coastal swamp with abundant evidence of plant colonization to fully marine conditions, evidenced by dinoflagellate cysts, recording thus the Rhaetian maximum flooding.
Helsingborg Member The Uppermost member of the formation is entirely of Hettangian age, and is the last layer before the start of the deposition of the younger dominant marine Rya Formation. This member is dominated by Deltaic sediments, along several marine interealatians are frequent, with deposition of coarse, in some cases arkosic sandstones in between more fine-grained deposits may indicate Early Kimmerian tectonic movements. The member has a maximunn thickness of 215 m and is divided in 2 parts: Höllviken No. 2 indicated that the lower part starts with up to 12 m of kaolinitic clay succeeded by a 15–20 m thick sequence of cross-bedded arkoses and light-coloured clays, being called Boserup beds or Thaumatopteris schenki zone (Pinuspollenites-Trachysporites Miospore Zone). This beds are known from Boserup, but also from the central part of Helsingborg, the Köpinge No. 3 bore and even extent to the Höganäs region (northwest to Eslöv in the south). This beds are overlain by some metres of arenaceous clays, iron claystone and calcareous sandstone with few intercalation of a coal seam (known as Tågaborg coal seam), where floral remains are also recovered such as Dictyophyllum nilssoni and Equisetites spp. Then the layers turn into 5 m of argillaceous sandstone and 5 m slightly arenaceous clays, with a last 1 m of calcareous sandstone, on a sequence known from cliff series at Laröd-Sofiero at the north of Helsingborg, with plant remains such as Nilssonia polymorpha and Dictyophyllum nilssoni, referred to the Pinuspollenites-Trachysporites zone. It also appears on Rosendal, Fleninge, Farhult and Klappe. Helsingborg (Vossbäumer I 969). There is a coal seam, Tinkarpsflötsen, in the middle part of the sequence. The upper part of the Helsingborg Member starts with a 28 m thick sandstone, with a section known as Fleninge beds, that represent layers where marine ingressions were more common, with the last layers of the formation made up of sandstone, claystone and several minor coal seams.
Fossil content
Ichnofossils GenusSpeciesLocationMaterialMade ByAulichnites A. ispBjuv Hyllinge Farhult Klappe Oregården RosendalDwelling structures GastropodsDiplichnites D. ispp.Bjuv Hyllinge Farhult Klappe Oregården RosendalHypichnial trackway Arachnids Insects Isopods Myriapods XiphosuransDiplocraterion D. parallelum D. ispp.Bjuv Hyllinge Farhult Klappe Oregården RosendalU-Shaped Burrows Annelids Crustaceans Insects Phoronids FishLockeia L. siliquariaBjuv Hyllinge Farhult Klappe Oregården RosendalDwelling traces BivalvesMonocraterion M. tentaculatumBjuv Hyllinge Farhult Klappe Oregården RosendalU-Shaped Burrows Echiurans Enteropneustans Polychaeta SipunculaPlanolites P. annularis P. montanusBjuv Hyllinge Farhult Klappe Oregården RosendalHorizontal burrows Annelids Bivalves CrustaceansRhizocorallium R. ispp.Bjuv Hyllinge Farhult Klappe Oregården RosendalTubular Fodinichnia Annelids Crustaceans InsectsSkolithos S. isp.Bjuv Hyllinge Farhult Klappe Oregården RosendalSac/Bottle shaped burrows Annelids Crustaceans InsectsTeichichnus T. isp.Bjuv Hyllinge Farhult Klappe Oregården RosendalDwelling traces Echiurans Holothurians Polychaetes
Annelida Genus Species Stratigraphic position Member Material Notes ImagesBurejospermumB. crassitestumBjuvBjuv memberCocoonsFreshwater Clitellata Cocoons (Oligochaeta and Hirudinea)."Cycadeospermum""C." sp.BjuvBjuv memberCocoonsDictyothylakosD. pesslerae D. sp. BjuvBjuv memberCocoons
Mollusks Genus Species Location Stratigraphic position Material Notes ImagesAviculaA. nilssoniRosendal Farhult Oregården KlappeBjuv member Helsingborg memberShellsAn Oyster member of Pteriidae CardiniaC. ingelensisRosendal Farhult Oregården KlappeBjuv member Helsingborg memberShellsA Clam member of Cardiniidae inside Carditida. CeratomyaC. stensioei HyllingeBjuv memberShellsA piddock member of Ceromyidae.CercomyaC. carlsoni BjuvBjuv memberShellsA piddock member of Ceromyidae.ChemnitziaC. sp.Vallåkra Vallåkra MemberShellsA sea snail member of Turbonillinae.Eutrapetzium E. pullastra E. hyllingenseRosendal Farhult Hyllinge Oregården KlappeBjuv member Helsingborg memberShellsAn Oyster member of Ostreidae. The local material assigned to this genus is now lostGervillia G. angelini G. praecursorRosendal Farhult Oregården Klappe VallåkraVallåkra Member Bjuv member Helsingborg memberShellsAn Oyster member of BakevelliidaeLiostreaL. hisingeriBjuv Rosendal Farhult Oregården Klappe HelsingborgBjuv member Helsingborg memberShellsAn Oyster member of Ostreidae . The most common Bivalve found locally.MesodesmaM. germariRosendal Farhult Oregården KlappeBjuv member Helsingborg memberShellsA Clam member of Mesodesmatidae inside Venerida. Modiolus M. hoffinanni M. minutus M. sp.Farhult Klappe Helsingborg Oregården Rosendal Skromberga SvanebeckBjuv member Helsingborg memberShellsA Mussel member of Mytilidae. Mya M. ovalis M. elongatusRosendal Farhult Oregården KlappeBjuv member Helsingborg memberShellsA Clam member of Myidae inside Myida. PectenP. sp.Vallåkra Vallåkra MemberShellsA scallop member of Pectinidae. Pleuromya P. aquarum P. suevicaRosendal Farhult Oregården Klappe Skromberga VallåkraVallåkra Member Bjuv member Helsingborg memberShellsA Clam member of Pleuromyidae inside Myida. Protocardia P. eicaldi P. praecursor P. rhaetica P. suecica P. sp.Rosendal Farhult Oregården Klappe VallåkraVallåkra Member Bjuv member Helsingborg memberShellsA Clam member of Protocardiinae inside Carditida. Venerupis V. elongala V. herbertiRosendal Farhult Oregården KlappeBjuv member Helsingborg memberShellsA Clam member of Veneridae inside Venerida.
Insecta Genus Species Location Stratigraphic position Material Notes ImagesAngelinellaA. angeliniHöganäsBjuv memberElytronsA beetle, incertae sedis ArchostemataHeeriaopsisH. laevigatumHöganäsBjuv memberElytronsA beetle, incertae sedis ArchostemataNannocurculionitesN. carlsoniBjuvBjuv memberElytronsA beetle, incertae sedis Archostemata. Originally identified as Curculionites carlsoniParabuprestitesP. rugulosusBjuvBjuv memberElytronsA Beetle, member of the family Cupedidae. Originally identified as Buprestites rugulosusPseudocarabitesP. deplanatusBjuvBjuv memberElytronsA Beetle, member of the family Carabidae. Originally identified as Carabites deplanatus. PseudohydrophilitesP. nathorstiBjuvBjuv memberElytronsA Beetle, member of the family Schizocoleidae. Originally identified as Hydrophilites nathorsti.
Fish Genus Species Location Stratigraphic position Material Notes ImagesHybodusH. sp.HelsingborgHelsingborg memberIsolated TeethA freshwater/marine member of Hybodontidae.HyllingeaH. swanbergiHyllingeBjuv memberTwo flattened fossils, both almost 62 cm in length.A freshwater member of the family Acrolepidae or Ptycholepiformes. LissodusL. sp.HelsingborgHelsingborg memberIsolated TeethA freshwater/marine member of Lonchidiidae. PalaeoxyrisP. muensteriBjuv HelsingborgBjuv member Helsingborg memberShark eggs CapsulesFreshwater shark egg capsule associated with Neocalamites, likely produced by members of Hybodontidae.ParvodusP. sp.HelsingborgHelsingborg memberIsolated TeethA freshwater/marine member of Lonchidiidae. SaurichthysS. acuminatusBjuvBjuv memberSpecimen preserved in an slab; referred scales & TeethA freshwater member of the family Saurichthyidae. ScanilepisS. dubiaBjuvBjuv member (Rhaetian)Almost complete large (110 cm); Isolated specimen (200 cm) which is a counter-impressionA freshwater member of the family Scanilepididae.SemionotusS. nilssoniBjuv BoserupBjuv memberSpecimen preserved in an slab; referred scales & TeethA freshwater member of the family Semionotidae.
Amphibia Genus Species Location Stratigraphic position Material Notes Images GerrothoraxG. pulcherrimusCoal-mine at BjuvBjuv memberLU 3176T, LU 3176aT, LU 3176bT, postcrania including interclavicles and clavicles, vertebrae and osteoderms; referred NR B2–4, partial skull & NR B18a, b, c, d, e, postcranial remainsAn amphibian, member of the family Plagiosauridae.
Amniotes