Per Ahlberg

Lund University | LU · Department of Geology

One of the most complete, spectacular and most thoroughly documented sections of Ordovician cool to temperate water limestones, globally. It is significant in understanding the Ordovician world.

The recent discovery of well-preserved fragments of Sphenothallus in the Central Clare Group (Pennsylvanian) of western Ireland provides new insights into the morphology of this enigmatic, putative cnidarian. The specimens demonstrate a morphological plasticity, including features not previously described for Sphenothallus , such as the presence of...

Fluctuations in marine oxygen concentrations have been invoked as a primary driver for changes in biodiversity throughout Earth history. Expansions in reducing marine conditions are commonly invoked as key causal mechanisms for mass extinctions, while increases in marine oxygenation are becoming an increasingly common causal mechanism invoked for b...

The Ordovician of Scandinavia (i.e. Denmark, Norway and Sweden) have been investigated for over two centuries, and through time various chronostratigraphic schemes have been introduced, facilitating regional correlation. However, a modern chronostratigraphy has never been proposed. Here, we delineate ten regional stages for the Ordovician of Scandi...

The taxonomically difficult ellipsocephalid trilobites from upper lower Cambrian (unnamed Stage 4) strata in Scandinavia are reviewed and revised. The suggested generic identities illustrate the diversification of the Ellipsocephalinae and advocate a modified correlation of the late to latest early Cambrian strata in Scandinavia and Baltica. The st...

Two massive precipitation events of polymetallic ore deposits, encrusted by a mixture of authigenic carbonates, are documented from the Cambrian of the semi-enclosed Baltoscandian Basin. δ34S (‒9.33 to ‒2.08‰) and δ33S (‒4.75 to ‒1.06‰) values from the basal sulphide breccias, sourced from contemporaneous Pb–Zn–Fe-bearing vein stockworks, refect su...

The late Cambrian Steptoean positive carbon isotope excursion (SPICE) represents a major perturbation to the global carbon cycle and was associated with trilobite extinctions and expansion of anoxic and/or euxinic water masses during episodes of eustatic sea-level change. We present a new Re-Os age together with Os and Nd isotope stratigraphy and m...

Continuous and biostratigraphically well-constrained carbon isotope (δ¹³Corg) profiles through the upper Miaolingian (middle Cambrian) to Tremadocian (Lower Ordovician) part of the Alum Shale Formation in four drill cores from southernmost Scandinavia are described. The sections record seven Furongian (upper Cambrian) excursions/spikes, of which th...

In this chapter, we explore the constellation of things in the museum assembled by the Swedish physician and university professor Kilian Stobæus (1690–1742). In particular, we focus on fossils, objects that interested Stobæus the most and were probably the first specimens in his collections. We examine the mechanisms of collecting – the modes in wh...

The Krapperup drill core from Scania (Skåne), southern Sweden, includes one of the most important graptolitic Darriwilian (upper Middle Ordovician) successions of Baltica. Only some intervals have been documented previously and especially the uppermost part of the succession has been completely unknown. A fairly complete succession of mid- to late...

The occurrence of a series of thin but persistent early Cambrian (Cambrian Age 4) brachiopod shell concentrations extending along a transect of some 150 km in NE Greenland, indicates the ability of the group to form widespread, skeletal pavements very early in the history of the phylum, its gregarious behaviour and ability to harness available nutr...

The Dapingian and lower Darriwilian graptolite succession of the Krapperup drill core from Scania, southern Sweden, provides a detailed insight into the axonophoran (biserial) graptolites and their early Palaeozoic evolutionary changes on the Scandinavian platform. Even though earliest Darriwilian axonophorans are not represented, the succession in...

The Cambrian succession of the Tingskullen drill core from northern Öland comprises Cambrian Series 2 and Miaolingian (Wuliuan Stage) siliciclastic strata. The major portion of the succession is represented by the Miaolingian Borgholm Formation, which, in ascending order, is subdivided into the Mossberga, Bårstad and Äleklinta members. The Äleklint...

Appearance of metazoans with mineralized skeletons, “explosion” in biotic diversity and disparity, infaunalization of the substrate, occurrence of metazoan Konservat Fossil-lagerstätten, establishment of most invertebrate phyla, strong faunal provincialism, dominance of trilobites, generally warm climate but with possible glacial–interglacial cycle...

Trilobites are marine arthropods that appeared in Cambrian Epoch 2 and became extinct at the end of the Permian. In some Paleozoic deposits, they number among the most abundant macrofossils. Trilobites are important for early Paleozoic biostratigraphy, especially Cambrian.

Recent studies on δ13C chemostratigraphy have produced a wealth of new information of major importance for clarification of local and global stratigraphic relationships. Currently, approximately 15 named positive and negative isotopic excursions have been identified in the Ordovician System. Some of these are significant and geographically widespre...

In a recent communication on carbon isotope chemostratigraphy of the uppermost Cambrian strata, it was claimed that the Top of Cambrian Excursion (TOCE) is (1) an undocumented negative δ13C carb excursion; (2) ambiguously defined; (3) deliberately fictitious or, in the authors' words, a 'nihilartikel'; and (4) not synonymous with the Hellnmaria-Red...

In 2006, a new species of non-calcified dasycladalean alga, Chaetocladus gracilis, from the upper Silurian of Skåne (Scania), southernmost Sweden, was erected. The original description was based on a single incomplete fossil recovered from the abandoned limestone quarry at Bjärsjölagård, a classic geologic locality in Scania. Here we present four a...

The largely covered Middle Ordovician succession in the classic geological Röstånga area in northwestern Scania has not been studied for some 80 years. A new drill core through a succession ranging from the lower–middle Darriwilian to the lower Sandbian has provided a unique opportunity to investigate the graptolite biostratigraphy and the δ13Corg...

The graptolite biostratigraphy of the 116.11-m-long Röstånga-2 drill core from Scania, southern Sweden, includes the Darriwilian (Middle Ordovician) Holmograptus lentus, Nicholsonograptus fasciculatus, Pterograptus elegans, Pseudamplexograptus distichus and Jiangxigraptus vagus biozones, and the lower Sandbian (Upper Ordovician) Nemagraptus gracili...

The zonation of the Furongian Alum Shale in Scandinavia, based on olenid trilobites, is reviewed and revised. The current scheme is rooted in a detailed zonation introduced in the late 1950s with subzones that subsequently have been elevated to zonal rank. Ten of these zones are difficult to recognize in all Alum Shale districts, and a revised zona...

Detailed diagenetic studies of the late Cambrian Alum Shale in southern Sweden were undertaken across an interval that includes the peak Steptoean Positive Carbon Isotope Excursion (SPICE) event to evaluate the pyrite mineralization history in the formation. Samples were collected from the Andrarum-3 core (Scania, Sweden); here the Alum was deposit...

The δ¹³C chemostratigraphy of five of the seven Ordovician global stages has been published previously but no such data have been available from the Floian GSSP and most of the Sandbian GSSP in Sweden. This lack of information has now been remedied by isotope data obtained from series of closely spaced shale samples collected from the Floian strato...

Fossilized eyes permit inferences of the visual capacity of extinct arthropods1–3. However, structural and/or chemical modifications as a result of taphonomic and diagenetic processes can alter the original features, thereby necessitating comparisons with modern species. Here we report the detailed molecular composition and microanatomy of the eyes...

The upper Middle to basal Upper Ordovician succession (Darriwilian to Sandbian) of the Fågelsång-3 drill core provides new important information on the graptolite biostratigraphy of Scania, southern Sweden. The Scanian succession is known largely from drill cores and a few scattered outcrops exposing only parts of the interval. The Darriwilian Alme...

The Miaolingian is the new formal name for Cambrian Series 3 (≈ “Middle” Cambrian). The Global Stratotype Section and Point (GSSP) is defined in the Kaili Formation, Guizhou province, China, and is correlated by the First appearance Datum (FAD) of the trilobite Oryctocephalus indicus. However, this fossil has not been recorded from Baltoscandia. He...

Two major, extended diversifications punctuated the evolution of marine life during the Early Palaeozoic. The interregnum, however, between the Cambrian Explosion and the Great Ordovician Biodiversification Event, is exemplified by the Furongian Gap when there was a marked drop in biodiversity. It is unclear whether the gap is apparent, due to samp...

The Lower to Middle Ordovician Tøyen Shale in southern Sweden, a biostratigraphically well-dated siliciclastic mudstone unit, shows 18 distinct authigenic cements that include sulfides, carbonates, silicates, clays, and phosphates. Marcasite, sphalerite, galena, and six texturally distinct types of pyrite characterize the sulfides whereas only one...

As carbonate sediments are strongly influenced by syndepositional conditions, carbonate rocks form an invaluable source of paleoenvironmental information. Analyses of late Cambrian (Furongian) to Middle Ordovician cool-water carbonates from the Baltoscandian paleobasin typically reveal consistent overall stratigraphic patterns and trends in microfa...

In Scandinavia, the boundary between provisional Cambrian Stage 4 and the Wuliuan Stage is marked by a prominent unconformity ascribed to non-deposition and erosion during a eustatic sea-level fall that may partially correlate with the regressive ’Hawke Bay Event’. Wuliuan strata are widely distributed in Scandinavia, but exposures are relatively f...

This study documents the early post-embryonic developmental stages (protaspides and early meraspides) of the Cambrian trilobite Ellipsostrenua granulosa (Ahlberg, 1984) from the Gärdsjön Formation of Jämtland, Sweden. The early protaspid stage is characterized by a circular outline of the exoskeleton, two pairs of fixigenal spines, a short preglabe...

The Ordovician Tøyen Shale Formation of the recently retrieved Fågelsång-3 drill core provides some important information on the graptolite biostratigraphy of the unit and its completeness in the region. The drill core reached downwards into the Kiaerograptus supremus Biozone of late Tremadocian age. Above a major fault zone, faunas with a number o...

The Grönhögen-2015 core drilling on southern Öland, Sweden, penetrated 50.15 m of Cambrian Series 3, Furongian and Lower–Middle Ordovician strata. The Cambrian succession includes the Äleklinta Member (upper Stage 5) of the Borgholm Formation and the Alum Shale Formation (Guzhangian–Tremadocian). Agnostoids and trilobites allowed subdivision of the...

A recent core drilling in the geologically classical Fågelsång area resulted in a 58.70-m-long drill core through the lowermost Sandbian Sularp Shale, the Darriwilian Almelund Shale and Komstad Limestone, and part of the late Tremadocian to earliest Darriwilian Tøyen Shale. The shales contain zone index graptolites that are used for an update of th...

A ca 20 m thick succession of upper Furongian (Cambrian Stage 10) through Middle Ordovician (Darriwilian) strata exposed at Lanna, in the province of Närke, south-central Sweden, is described. The upper Furongian is represented by the Alum Shale Formation and reflects an overall shallowing trend that ultimately resulted in emergence above sea level...

The Lower Ordovician Bjørkåsholmen Formation at Flagabro, Scania, southern Sweden, consists of a 0.8 m thick succession of carbonates with three siliciclastic mudstones, 5, 1 and 100 mm thick, intercalated in the central part of the unit. Carbonate and siliciclastic mudstone beds show both normal and inverse grading. The carbonates are mud-rich and...

One of the principal biostratigraphical tools used in the lower Palaeozoic, and especially the Cambrian System, is trilobites. Historically, both polymerids and agnostoids have commonly been included as ‘trilobite’ groups, although currently the question of whether they comprise a monophyletic group or are polyphyletic is unsettled. Beginning in th...

The Tomten-1 drilling at Torbjörntorp in Västergötland, southern Sweden, penetrated 29.85 m of Cambrian Series 2, Cambrian Series 3, Furongian, and Lower–Middle Ordovician strata. Lithostratigraphically, the succession includes the File Haidar, Borgholm and Alum Shale formations, and the Latorp and Lanna limestones. The drill core succession is des...

A pioneer δ13Corg study through the upper Sandbian and Katian (Upper Ordovician) succession in the Röstånga 1 drill core in the classical geological outcrop area at Röstånga in southernmost Sweden produced a wealth of new carbon isotope data which are useful for local and regional correlations. Among the Upper Ordovician positive δ13C excursions, t...

Ordovician (485.4 – 443.8 Ma) strata record biotic diversification pulses of marine fauna and the growth of the Gondwanan ice sheets, which culminated in the latest Ordovician glaciation and mass extinction. These phenomena were set against the closure of the Iapetus Ocean, onset of the Appalachian-Caledonian orogeny, and large fluctuations in the...

Except for the scattered cephalopod conchs that have given the rock type its name, mollusk fossils are relatively rare in the Middle Ordovician ‘orthoceratite limestone’ of Sweden. However, an interval in the Darriwilian stands out as being unusually rich in various types of mollusks. Throughout southern Sweden, gastropods became relatively abundan...

Three cranidia of a conocoryphid trilobite are described from the lower Caesaraugustan Regional Stage (upper part of provisional Cambrian Stage 5 within Cambrian Series 3) in the Iberian Chains, Spain. The material is from the upper part of the Mansilla Formation and the base of the overlying Murero Formation. It closely resembles Bailiella tenuici...

Well-preserved early holaspid stages of the Cambrian Series 3 trilobites Ellipsocephalus hoffi (Schlotheim, 1823) and Ellipsocephalus polytomus Linnarsson, 1877 have been discovered in the Příbram-Jince Basin (Czech Republic) and Jämtland (Sweden), respectively. Both species show remarkable morphological changes during late ontogeny. The earliest h...

The late Ediacaran–mid Cambrian occurrences of phosphorites in the western Mediterranean region (West Gondwana) and southern Sweden (north-west Baltica) are related to the poleward drift of West Gondwana and the northern drift of Baltica. As a result, these regions crossed subtropical and temperate palaeolatitudes of the southern hemisphere, in whi...

The developing high-resolution chronostratigraphy of the Cambrian provides an updated age model for various geologic and biotic events that occurred during this critical period of Earth history. Broad, time-specific patterns of lithofacies, such as organic-rich deposits, and biofacies appear to be consistent across all Cambrian paleocontinents. Rec...

The concept of the agnostoid arthropod species Lotagnostus americanus (Billings, 1860), which has been reported from numerous localities in the upper Furongian Series (Cambrian) of Laurentia, Gondwana, Baltica, Avalonia, and Siberia, is reviewed with emphasis on morphologic and taphonomic information afforded by large collections from Hunan in Sout...

Seventeen taxa of exotic trilobites representing eight families are described from the olenid- and agnostoid-dominated strata of the uppermost Cambrian Series 3 and lower Furongian alum shale facies of Sweden and from glacial erratic boulders of Denmark. Only five taxa are assigned to species level, i.e., Maladioidella abdita (Salter, 1866), Olente...

The Cambrian Alum Shale Formation in the Andrarum-3 core from Scania, southern Sweden, consists of black siliciclastic mudstone with minor carbonate intercalations. Four facies comprise three siliciclastic mudstones and one fine-grained carbonate. The facies reflect deposition along a transect from deep ramp to basin on a Cambrian shelf. The three...

Sphenothallus, a Palaeozoic genus of uncertain affinity, possibly a hydrozoan, is reported from the Furongian (Cambrian) of Scandinavia. This is the only known occurrence of the genus in Cambrian rocks outside of China, western North America and Bohemia, and also the first report of Sphenothallus in the Cambrian–Ordovician of Baltica. The material...

A palynological study of the Ordovician–Silurian boundary (Katian–Rhuddanian) succession in the Röstånga-1 drillcore, southern Sweden, has been performed. The lithology is dominated by mudstone and graptolitic shale, with subordinate limestone, formed in the deeper marine halo of southern Baltica. The palynological assemblages are dominated by mari...

Since the time of its ratification in 1992, the Cambrian GSSP, 2.3 m above the base of Member 2A (Quaco Road Member) of the Chapel Island Formation, Fortune Head section, Newfoundland, Canada, has been challenged as posing an ambiguous correlation level. Difficulties have been encountered in precisely correlating the horizon coinciding with the GSS...

The Röstånga-1 core from west-central Scania provides the most complete succession of the Sandbian (Upper Ordovician) through lower Telychian (Silurian, Llandovery) strata of southern Scandinavia. The Hirnantian is identified in the Kallholn Formation by the presence of a Metabolograptus persculptus Biozone fauna. The Akidograptus ascensus, Parakid...

Cambrian Series 2 (Stage 4) helcionelloid molluscs are relatively common at two localities in Sweden: Gislövshammar, SE Scania, and Mt Luopakte, south of Lake Torneträsk, northern Lapland. At Gislövshammar, more than 500 specimens have been recovered from a 30 cm thick interval of laminated siltstone with intercalated calcareous nodules in the Gisl...

Upper lower Cambrian (provisional Cambrian Series 2) trilobites are described from three sections through the Shuangyingshan Formation in the Beishan area, northwestern Gansu Province, China. The trilobite fauna is dominated by eodiscoid and 'corynexochid' trilobites, together representing at least ten genera: Serrodiscus, Tannudiscus, Calodiscus,...

Palaeobiogeographical data on Cambrian trilobites obtained during the twentieth century are combined in this paper to evaluate palaeoceanographic links through c. 30 myr, once these arthropods biomineralized. Worldwide major tectonostratigraphic units are characterized at series intervals of Cambrian time and datasets of trilobite genera (629 for C...