The Hasle Formation is a geologic formation on the island on Bornholm, Denmark. It is of early to late Pliensbachian age. Vertebrate fossils have been uncovered from this formation.[2][3] The type section of the formation is found at the south of the costal Hasle Town, and it is composed by rusty yellow to brownish siltstones and very fine-grained sandstones. The southernmost arch, Hvjdoddebuen, is not as fossil-bearing as the type unit in Hasle.[4] The formation can be separated in two different petrographic types: type 1 sandstones are friable with layers and lenses of concretionary siderite and type 2 well-cemented sandstones.[5] Both types where deposited in a relatively high-energy marine environment with a diagenetic pattern that demonstrates a close relation to various phases of subsidence and uplift in the tectonically unstable Fennoscandian Border Zone.[5]
Most of its deposition happened on a storm-dominated shoreface, with the exposed parts deposited in an open marine shelf within 1–2 km distance from the fault-controlled coastlines.[6] However, recent works have recovered terrestrial fauna from it, including a footprint, suggesting easterly winds and low tide could have exposed the inner parts of the upper shoreface, and create long-lasting Floodplain-type environments.[7] Field works since 1984 have shown a mostly hummocky cross-stratified deposition, with great complexity of the sediments that suggests very complicated and variable flow conditions, with Megaripples derived from storm events.[8] Storms were frequent and the coastline faced a wide epeiric sea with a fetch towards the west of possibly 1000 kilometers.[8] The Jamesoni–Ibex Chronozone in the Central European Basin represents a clear sea Transgression, due to the appearance of ammonites from Thuringia and southern Lower Saxony, showing a full marine ingression towards the west.[9] This rise in the sea level is also measured in the north, as is proven by the presence of Uptonia jamesoni in Kurremölla (Röddinge Formation, Skåne) and Beaniceras centaurus plus
Phricodoceras taylori on the Hasle Formation.[9] The whole Hasle Sandstones are a result of this rise in the sea level, where the marine sediments cover the deltaic layers of the Rønne Formation.[9] The rise in the sea level is observed on palynology, as on the Hasle Formation Nannoceratopsis senex (Dinoflajellate) and Mendicodinium reticulaturn (Algae Acritarch) appear, indicating a transition from paralic and restricted marine to fully marine.[10]
A Saltwater lamp shell Brachiopodan, member of Terebratulidae inside Terebratulida. The specimens are rather incomplete. The genus is a possible junior synonym of Terebratula.
A saltwater Clam, type member of the family Astartidae inside Carditida. It is found on small, smooth Clam associations, with the exception of one does section, with less well-preserved stone cores and imprints.
A saltwater pearl oyster, member of the family Pteriidae inside Ostreida. Some specimens are big and found associated with Burrow-filled surfaces. This well-known species occurs extremely frequently; Copies occur at all ages, as well as right-handers Left shells have been found.
A saltwater Oyster, member of the family Bakevelliidae inside Ostreida. Found on a series of incomplete Stone Cores filled with specimens, that by Size and Form can be possibly attributable to Gervilleia aerosa.
A saltwater Scallop, member of the family Pectinoidae inside Pectinida. A Pair of incomplete specimens of a Hinnites are known and probably match with the species Hinnites tumidus; however, the state of preservation is bad, with the assignment rather uncertain.
A saltwater nut Clam, type member of the family Nuculidae inside Nuculida. Two copies of a Nucula (leda?) so closely in accordance with Moberg's depictions and description of occurring at Kurremolla.
A saltwater pointed nut Clam, type member of the family Nuculanidae inside Nuculida. Nuculana bornholmiensis is a very common genus only found locally.
A saltwater Scallop, type member of the family Pectinoidae inside Pectinida. This species has been exceedingly frequent, and numerous Fragments are available.
A saltwater Clam, type member of the family Tancrediidae inside Carditida. Tancredia lineata Is based on six shell cores, of which one complete, the others a little defective at the front end.
A saltwater Snail, type member of the family Acteoninidae inside Prosobranchia. Of this small species there are quite a few specimens, both stone cores and imprints that perfectly allow identifying the species.
A saltwater Snail, member of the family Pyramidellidae inside Pyramidelloidea. Two Specimens of a Turritella-like Gastropod found locally have been refer to the Genus. Chemnitzia citharella includes ten specimens, the largest of the genus found locally. However, most of the specimens are shell cores.
A belemnite, incertae sedis member of the family Belemnitida. Frequently shows the embryonic chamber preserved as a bladder, slightly bent forward-towards the ventral side.
An Ammonite of the family Coeloceratidae inside Psilocerataceae. Senior synonym of Aegoceras pettos. Possible junior synonym of Coeloceras grenouillouxi[3]
A marine shark, type member of the family Agaleidae inside Euselachii. This genus may have been a suction feeder as its anterior teeth are similar to those of extant nurse sharks.
A marine shark, type member of the family Hybodontidae inside Hybodontiformes. Its teeth suggest that it may have been feeding on shelly invertebrates.
A marine/brackish Osteichthyes, representative of the family Saurichthyidae inside Chondrostei. The referral to the genus must be taken with caution, as currently it´s geological range is limited to the Triassic.
A TeleosauridaeThalattosuchian. One of the northernmost fossil finds of the group and one of the few of the pliensbachian worldwide, it represents a genus whose dermal armor was similar to the genus Macrospondylus of the Toarcian.[22]
A possible Pterosaur. Is quoted the find of a "Flying Reptile" on the Hasle Sandstone by C. Malling at the beginning of the 20th century. No further data related to the find has been published.
Theropod, incertae sedis inside Neotheropoda. Extremely hollow shaft suggests that it most likely belonged to a juvenile member of a theropod dinosaur.[24]
Theropod Tracks, member of the ichnofamily Anchisauripodidae, incertae sedis inside Theropoda. Considered a very Small Dinosaur, probably a juvenile. The Foot resembles those of young Coelophysis from Ghost Ranch Quarries.[7]Stenonyx footprints had been described from the Early Jurassic Soltykow (Hettangian) and an identical one from Szydlowek (Pliensbachian), linking southern Sweden, Bornholm and Poland, contiguous during the Early Jurassic and dinosaurs could thus freely roam this large area.[7]
A SauropodSauropodomorph. Assigned to an early actual Sauropods, which also have quite powerful lateral processes and whose cervical vertebrae are relatively long.
A possible TuriasaurianEusauropod. The oldest geological record of the family, likely represents a new unnamed taxon, estimated to have been 10–14 m long based on related taxa.[29]
A TritylodontoideaCynognathian. Hasle Formation fossil cannot be confidently placed within any known genus, it can be either a primitive Tritylodont related to specimens that lack post-canines (Yunnanodon, Dianzhongia), or an early derived genus of the Stereognathus group.[26] It is the oldest occurrence of a mammaliamorph in Scandinavia.[26]
^Gry, H.; Jørgart, T.; Poulsen, V. (1969). "Lithostratigraphy and sedimentary evolution of the Triassic, Jurassic and Lower Cretaceous of Bornholm, Denmark". Mineralogisk Mus. 6 (1).
^Surlyk, F.; Arndorff, L.; Hamann, N. E.; Hamberg, L.; Johannessen, P. N.; Koppelhus, E. B.; Petersen, H. I. (1995). "High-resolution sequence stratigraphy of a Hettangian-Sinemurian paralic succession, Bornholm, Denmark". Sedimentology. 42 (2): 323–354. Bibcode:1995Sedim..42..323S. doi:10.1111/j.1365-3091.1995.tb02105.x.
^ abcdRees, J.; Bonde, N. (1999). "Plesiosaur remains from the Early Jurassic Hasle Formation, Bornholm, Denmark". Secondary Adaptation to Life in Water: 13–17.