The Kristianstad Basin (Swedish: Kristianstadsbassängen) is a Cretaceous-age structural basin and geological formation in northeastern Skåne, the southernmost province of Sweden. The basin extends from Hanöbukten, a bay in the Baltic Sea, in the east to the town of Hässleholm in the west and ends with the two horsts Linderödsåsen and Nävlingeåsen in the south. The basin's northern boundary is more diffuse and there are several outlying portions of Cretaceous-age sediments. During the Cretaceous, the region was a shallow subtropical to temperate inland sea and archipelago.
Though the sediments in the basin range in age from the Barremian to the earliest Maastrichtian, the only accessible strata are from the Late Cretaceous, ranging in age from the Early or early Middle Santonian to the earliest Maastrichtian. A majority of the fossil sites only expose strata of latest Early Campanian age ( 80.5 million years ago). Fossils from these sites have been collected since the 18th century, but most of the excavations have taken place through commercial quarrying in the 20th century and paleontological expeditions in the 20th and 21st centuries.
The Early Campanian deposits of the Kristianstad Basin preserve fossils of a diverse array of organisms, including algae, brachiopods, bryozoans, molluscs (notably large numbers of bivalves and belemnites), sea urchins and fish (including a large amount of shark species). The Kristianstad Basin has also yielded fossils of several varieties of reptiles, including plesiosaurs, turtles and crocodylomorphs, as well as one of the most diverse mosasaur faunas in the world and some of the few non-avian dinosaurs known from Sweden.
Geology
Geological background The Kristianstad Basin is located in northeastern Skåne, the southernmost province of Sweden, extending from Hanöbukten, a bay in the Baltic Sea, in the east to the town of Hässleholm in the west. The basement of the basin is crystalline and deeply weathered bedrock from the Precambrian. Most of this weathering, and the uneven topography of the basement, is due to the warm and moist climate experienced during the Jurassic or Early Cretaceous. The basement is overlaid by approximately 250 metres (820 feet) of mainly shallow water or marine sediments from the Cretaceous, ranging in age from the Barremian to the earliest Maastrichtian. In addition to the aquatic sediments, there are delta plain deposits of late Santonian to earliest Campanian age, overlaid by marine strata of latest Early Campanian age.
The surface of the basement slopes to the south and is cut off by Linderödsåsen and Nävlingeåsen, two horsts that mark the basin's south-western boundary. To the south-east, the basin's margin is marked by the Baltic Sea while the basin's northern margin is more diffuse, with several small outliers of Cretaceous-age sediments.
During the Late Cretaceous, the basement of the basin was subjected to several regressions and transgressions. The sediments within the basin are dominated by fine- to coarse-grained sandy biocalcarenites (calcarenites that contain fossils) and more or less consolidated sandstones. Conglomeratic beds are also common, typically consisting of belemnite rostra or bivalve shells and coarse terrigenous clastic rocks. There are also several flint beds in the upper parts of the strata, dating to the early Late Campanian through the earliest Maastrichtian. Dominant sediment types from the Early Campanian are oyster banks, calcarenites and calcareous, glauconitic quartz sands.
Accessible strata exposed in the basin range in age from Early or early Middle Santonian to earliest Maastrichtian. A majority of the fossil sites only expose strata of latest Early Campanian age ( 80.5 million years ago). This strata, the "Belemnellocamax mammillatus"-strata, is exceptionally rich in vertebrate fossils and diversity. The biozones of the Kristianstad Basin, based on the local belemnite fossils, are: +AgeSubdivisionTime (mya)Belemnite(s)RefImageSantonianEarly–middleNo precise estimateGonioteuthis westfalica westfalicaLate middleGonioteuthis westfalicagranulataLateGonioteuthis granulataCampanianEarliest 83.5Gonioteuthis granulaquadrata, Actinocamax verus, Belemnellocamax grossouvrei, Belemnitella alphaLatest early 80.5Belemnellocamax mammillatus, Belemnitella mucronata, Gonioteuthis quadrata scaniensisEarliest lateNo precise estimateBelemnellocamax balsvikensisEarly lateBelemnitella mucronataMiddle lateMaastrichtianEarliest 71.3Belemnella lanceolata
Prominent fossil sites
Most of the sites within the Kristianstad Basin are the result of commercial kaolin clay/limestone exploitation. The most prominent sites include:
Ivö Klack, historically known as Blaksudden, an abandoned and partly overgrown limestone and kaolin quarry on the northern slope of the island Ivö. Ivö Klack was once the shores of a small and rocky Cretaceous island and is one of the most extensively excavated sites in the basin, having been excavated since quarrying activities started in 1888. Though quarrying stopped in the late 1960s, the site continues to be excavated by paleontologists and amateurs. Ugnsmunnarna, a partly overgrown cliff section located on the island Ivö, about three kilometers south of Ivö Klack. The rocks at Ugnsmunnarna were deposited in a deeper-water part surrounding the Cretaceous Ivö island. Ignaberga, the Ignaberga site compromises two limestone quarries situated along the southern margin of the basin created by Nävlingeåsen. Maltesholm, a now disused limestone quarry adjacent to the northern end of Linderödsåsen. With the exception of abundant fragmentary invertebrate fossils, few other fossil remains have been found at Maltesholm. Åsen, an abandoned clay pit, presently used as a landfill. The topography of the basement rock, the presence of floodplain sediments and the recovery of fossil hybodont shark teeth suggests that the location was near an ancient river system. One of the most extensively excavated sites in the basin. Axeltorp, an abandoned and overgrown limestone quarry. Balsberg, a natural cave located on the southwestern slope of the Balsberget hill. Ivetofta, a drill core in the town of Bromölla, the sediments penetrated are of latest Early Campanian age. Kjuge, a natural cliff section located near the lake Ivösjön. Ullstorp, a series of five small quarries (one of which remains active) close to Nävlingeåsen. Balsvik, an overgrown quarry which in addition to Campanian rocks also exposes approximately three meters (9 ft) of earliest Maastrichtian strata.
History of research
Local paleontological and geological research
The Kristianstad Basin is one of the most prolific and historically famous Mesozoic fossil sites in Scandinavia. The earliest known fossil discoveries within the basin were made by the physician and paleontologist Magnus Bromelius at Ivö Klack and Ignaberga in 1725. Most of the early fossil finds were belemnite fossils, descriptions of which were published by physician and naturalist Kilian Stobæus in 1752 (whose work Opuscula included the first illustrations of the common Belemnellocamax mammillatus belemnites), naturalist Göran Wahlenberg in 1821 and zoologist and archaeologist Sven Nilsson in 1826, 1827, 1835 and 1857. Early sedimentological studies were also conducted throughout the 19th and early 20th centuries, prominently by paleontologist and geologist Bernhard Lundgren in 1888 and geologist Alf Lundegren in 1931 and 1934.
The various limestone and kaolin quarries throughout the basin were described in detail by geologist and paleontologist Karl A. Grönwall in 1915, followed by further descriptions by Alf Lundegren in 1931, geologist Lars Bjerning in 1947, geologist Per H. Lundegårdh in 1971, geologists Jan Bergström and Naz Ahmed Shaikh in 1980 and geologists Mikael Erlström and Jan Gabrielson in 1985 and 1992. Throughout the 20th century, quarrying was most intense at Åsen, Axeltorp and Ivö Klack, most of it conducted by the companies Höganäs keramik and Ifö-verken.
Important historical studies conducted on the basin's many invertebrate taxa include those by Bernhard Lundgren (in 1876, 1885 and 1895), paleontologist J. Christian Moberg in 1884 and 1885, geologist Anders H. Hennig in 1892, 1894 and 1904 (together with paleontologist Alfred Elis Törnebohm), geologist and mineralogist Assar Hadding in 1919, Alf Lundegren in 1934, paleontologist Gustaf Troedsson in 1946 and 1954, paleontologist Richard Hägg in 1954 and geologist and paleontologist Fritz Brotzen in 1960. Further studies on the invertebrate fauna, as with the more publicized vertebrate fossils, have continued into the 21st century.
Actinopterygian (ray-finned) fishes were first described form the basin by Sven Nilsson in 1827, with further studies being conducted by paleontologist John W. Davis in 1890 and by paleontologist Mohamad Bazzi and colleagues in 2016. Though shark teeth have been recovered from the basin since early times, the shark and ray fauna was first studied in detail by paleontologist Mikael Siverson in the 20th century, who in a series of publications from 1989 to 2016, some together with other authors, identified a vast number of species.
Marine reptile fossils, found at Ivetofta, were first described from the basin by Sven Nilsson in 1835. Nilsson's work was followed by further investigations by physicist and chemist Wilhelm Hisinger in 1837, archaeologist and bibliographer Johan Henrik Schröder in 1885 and paleontologist Carl Wiman in 1916. Later studies on marine reptile fossils were also conducted by J. Christian Moberg in 1884 and 1885, Bernhard Lundgren in 1888, Anders H. Hennig in 1910, Alf Lundegren in 1934, Gustaf Troedsson in 1946 and 1954 and prominently in a series of publications of paleontologist Per-Ove Persson, who described several species of mosasaurs and plesiosaurs alongside sea turtles and the crocodylomorph Aigialosuchus, from 1954 to 1996. More recent work on marine reptiles has been conducted primarily by Mikael Siverson and paleontologist Johan Lindgren (especially on mosasaurs) and paleontologists Elisabeth Einarsson, Benjamin P. Kear, Sven Sachs and Torsten M. Scheyer (especially on plesiosaurs and sea turtles).
Dinosaur fossils
Fossils of non-avian dinosaurs are exceptionally rare in Scandinavia, and the Kristianstad Basin is one of only two locations in Sweden where dinosaur fossils have been recovered. The only other site of known dinosaur fossils in Sweden is the Höganäs Formation, where they were first announced to be present by researchers in 2022. Though theropod teeth were reported from Ivö Klack by Per-Ove Persson in the 1950s, these have since been identified as fish teeth, probably from the genus Protosphyraena. Fossil material conclusively identified as dinosaurian was recovered only relatively recently, with the earliest discovery being two teeth from a small Ornithopod, similar to those of Hypsilophodon, being found at Ivö Klack in 2001. More comprehensive material referred to a leptoceratopsid ceratopsian ("Kristianasaura") was described in 2007 and further fragmentary fossils of other groups were recovered during excavations from 2010 to 2013. The local dinosaur fossils have mainly been researched by Johan Lindgren and paleontologist Jan Rees, alongside several colleagues.