Traditionally dated as Hettangian-Sinemurian only, recent palynology show that the uppermost assemblages are almost identical that the ones recovered in the Late Pliensbachian Sorthat Formation of Bornholm[1]
The Höör Sandstone is a geologic formation in Skåne County, southern Sweden. It is Early Jurassic (Hettangian-Pliensbachian) in age.[3] This unit outcrops in central Skane on a few isolated exposures, being traditionally subdivided into the lower “millstone” (“kvarnstenen”) and the upper “buildingstone”.[4] The lowermost layers where also claimed to host Rhaetian strata, however latter works suggested that the layers devolved as red beds, were part of the new Hörby Formation, thus delimitating the Höör sandstone to the lower Jurassic.[5][6] It has been assumed to be limited to Hettangian-Sinemurian layers, yet recent palynological analysis suggest the uppermost section is of Pliensbachian age, underlying and maybe interacting with the younger volcanic deposits.[1] The Höör sandstone represents a mostly fluvial unit with a rich collection of fossil plants, yet also includes brackish bivalves in some layers, pointing to marine ingressions locally.[7]
Members
Stanstorp member
This member represents the older layers of the formation, being exposed in the abandoned stanstorpsgraven quarry and in the Vittseröd area.[8] The member is mainly composed by sandstone and has abundant plants fossils, with both allochthonous plant fragments and plant roots indicating vegetation in situ (palaeosols).[8] The layers suggest several types of fluvial and/or coastal depositions, from dunes and river banks to beach deposits, where the palaeocurrent directions are clear generally from the north-east to the south-west.[7] This section hosts abundant conglomerate intercalations, with the lower ones formed by mud fragments and the uppers with distant source material, both abundant on wood fragments, some of them up to 20 cm in diameter.[8]
Vittseröd member
The youngest member is composed by finer-grained and much better sorted sandstones, with limited abundance of mudstones and plant fragments small and limited to a few horizons.[8] The presence of silt and mature quartz arenites, well sorted and fairly well rounded derived from strongly altered feldspars, shows that this member hosted a high-energy environment, one where tidal currents have been invoked for the modification of fine-grained sandstones, linked with the changes of the Laurasian Seaway.[9] The upper parts of this unit are influenced by the initial pulse of the Pliensbachian coeval vulcanism with heavy volcanic minerals in the uppermost layers.[10]
An oyster, member of Ostreidae inside Ostreida. The most common Bivalve found locally, indicator of increased salinity levels on the Hettangian layers.
A clam, member of Cardiniidae inside Carditida. This faunal aggrupation occurs together with abundant foliar remains and are equivalent to the Brandsberga erratics, which was closer to the mouth of the bay developed in the region, as it proves the find on its sandstone of more clear marine fauna.
A horseshoe crab, member of the Limulidae inside Xiphosura. This fragment has been considered to be a Limulus or Mesolimulus prosomal shield, but due to the limited and fragmentary nature some authors referred to it as ?Chelicerata incertae sedis.[14]
Affinities with Williamsoniaceae inside Bennettitales. Wielandiella may be regarded as a fossil taxon characterized by bennettitalean shrubs with branched stems and a divaricate architecture
Affinities with Krassiloviaceae inside Voltziales. The local Podozamites show a rather great range of growth, reflecting tropical to subtropical conditions.
^Brogniart, A. (1826). "De l'arkose — Caracteres mineralogiques et histoire geognostique de cette roche". Ann. Sci. Nat. 4 (1): 200–218.
^Warnock, S. (1983). "Geology of the Röstnga District, Central Skane". Bachelor of Science Thesis in Geology, Queens University. Belfast. 1 (1): 1–160.
^Halle, T. G. (1910). "On the Swedish species of Sagenopteris Presl and of Hydropterangium nov. gen". Kungliga Svenska Vetenskapsakademiens Handlingar. 45 (7): 1–16.
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