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 (c. 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 (c. 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:
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
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