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Glaciokarst is widespread in the Silurian carbonate bedrock on the Island of Gotland. Grikes and limestone pavements are the most common karst features. Although, less well documented, caves and subsurface channels also contribute to the complex hydrogeology in the bedrock. The karst is interpreted to have been formed, primarily, before the Pleistocene when the landscape was covered with acidic organic soils. Glacial erosion and postglacial karstification have also played significant roles in sculpturing the epikarst morphology we see today. The study presents quantitative and qualitative characterization of karst within several pilot areas on the island of Gotland. High resolution aerial photographs were acquired over the pilot areas using a drone. These images were then analysed in GIS-software to provide a statistical evaluation of length, width, and relative area with karst. As well as providing a statistical understanding of the occurrence and geometry of karst, the results also help to clarify the impact of karst on the sensitive and limited groundwater resources on Gotland. Since a large part of the carbonate bedrock surface is barren or covered by thin quaternary deposits the epikarst provides important pathways for the percolation of meteoric water and recharge to the groundwater. It also locally provides guided pathways for surface runoff. Furthermore, the study demonstrates that the presence of karst often is in conjunction with sensitive ecosystems such as temporary wetlands. Extensive development of grikes and limestone pavements also provide conditions for periodically hanging aquifers, which not only promotes groundwater recharge but also the formation of unique habitats for a variety of often threatened ecosystems. This study, which includes both biologists and earth scientists highlights the importance of the identification of catchment areas and mapping of karst. It also emphasises that investigations into the hydrogeology (including aspects such as groundwater recharge, surface runoff and subsurface transport pathways) is essential for a better understanding of wetland dynamics and their protection. The presence of karst and spreading of contaminations in the ground is also discussed. The work summarizes early results from a collaboration between authorities working with Natura 2000 karst habitats and geological classification and mapping of karst.

The Hemse Group is one of the least understood stratigraphic units of the Silurian sequence of Gotland, Sweden. New results from airborne transient electromagnetic (ATEM) measurements in combinatio...

The Cambrian succession of the Tingskullen drill core from northern Ãland 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, BÃ¥rstad and Ãleklinta members. The Ãleklinta Member is barren of body fossils, whereas the Mossberga and BÃ¥rstad members are moderately to highly fossiliferous and biostratigraphically reasonably well constrained. Trilobites and agnostoids from the BÃ¥rstad Member are indicative of the Acadoparadoxides pinus Zone. The Mossberga Member has not yielded any zonal guide fossils but is tentatively assigned to the Eccaparadoxides insularis Zone. A δ13Corg curve throughout the Borgholm Formation shows a general positive trend up-section without any distinctive excursion, suggesting that the Wuliuan Acadoparadoxides (Baltoparadoxides) oelandicus Superzone (the âOelandicus bedsâ) of Ãland is younger than the negative RedlichiidâOlenellid Extinction Carbon isotope Excursion (ROECE), which is known from near the top of Stage 4 and close to the traditional âLowerâMiddle Cambrian boundaryâ in several parts of the world.

The geological survey of Sweden (SGU) has carried out several detailed airborne TEM (Transient Electromagnetic) surveys in recent years. The data collected in these surveys were inverted to provide models of the resistivity of the subsurface, down to a few hundred meters depth. These resistivity models together with the data from existing boreholes and ground observations offer an excellent basis for further 3D geological modeling. The airborne TEM data presented in this study were collected between 2013 and 2016, covering large areas of the islands of Öland and Gotland, in Sweden. Both islands face problems with water supply due to limited groundwater resources. The aim of the surveys was to identify new groundwater resources, specify the depth to saline groundwater and to improve the understanding of the geology of the islands. On Öland, the Paleozoic sedimentary succession reaches thicknesses of approximately 250 m and is composed of Lower Cambrian sandstone, Middle Cambrian siltstone, and claystone followed by the Alum Shales of Upper Cambrian and Lower Ordovician age. Above this lies an up to 40 m thick Lower Ordovician limestone succession, which forms the bedrock at the surface across much of the island. The entire sedimentary sequence rests on Precambrian crystalline rocks. On the Island of Gotland, Silurian bedrock represents the upper part of a 250-800 m thick Paleozoic sequence overlying the crystalline basement. The Silurian bedrock is dominated by interbedded layers of limestone and marlstone, where the interface between limestone and marlstone is often the primary hydraulic conductor.After acquisition, these data were processed and inverted (1D inversions with lateral constraints), to provide a series of large airborne datasets, providing a resistivity image down to depths of about 250 m in some areas. The considerable resistivity contrast between lithologies, e.g. limestone and marlstone on Gotland, provided an excellent opportunity to resolve boundaries between the different rock types. Borehole information, geological maps, ground geophysical data and the inversion results were incorporated in a 3D geological modelling software. On comparison of the airborne models, ground geophysical data and borehole information it was clear that the airborne resistivity models correlated well with the other available data. Hence, the resistivity models were used as the basis for constructing the 3D hydrogeological and geological models over significant parts of the islands. In this study we present the 3D geological models over the islands of Öland and Gotland which were constructed from the integrated interpretation of all the available data. The models are composed of voxels, each representing a certain lithology classified using a statistical approach. The classification is based on the resistivity range, distance to the neighboring wells/boreholes and the geological observations at the surface. The 3D voxel models will be/have been utilized in hydrological modelling, societal planning, and groundwater management.

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 succession into eight biozones, in ascending order: the uppermost Cambrian Series 3 (Guzhangian) Agnostus pisiformis Zone and the Furongian Olenus gibbosus, O. truncatus, Parabolina spinulosa, Sphaerophthalmus? flagellifer, Ctenopyge tumida, C. linnarssoni and Parabolina lobata zones. Conspicuous lithologic unconformities and the biostratigraphy show that the succession is incomplete and that there are several substantial gaps of variable magnitudes. Carbon isotope analyses (δ13Corg) through the Alum Shale Formation revealed two globally significant excursions: the Steptoean Positive Carbon Isotope Excursion (SPICE) in the lower–middle Paibian Stage, and the negative Top of Cambrian Excursion (TOCE), previously referred to as the HERB Event, in Stage 10. The δ13Corg chemostratigraphy is tied directly to the biostratigraphy and used for an improved integration of these excursions with the standard agnostoid and trilobite zonation of Scandinavia. Their relations to that of coeval successions in Baltoscandia and elsewhere are discussed. The maximum amplitudes of the SPICE and TOCE in the Grönhögen succession are comparable to those recorded in drill cores retrieved from Scania, southern Sweden. The results of this study will be useful for assessing biostratigraphic relations between shale successions and carbonate facies on a global scale.

The Island of Gotland (3000 km2), east of mainland Sweden, suffers from insufficient water availability each summer. Thin soils and lack of coherent reservoirs in the sedimentary bedrock lead to limited reservoir capacity. The feasibility of Managed Aquifer Recharge (MAR) is explored by identifying suitable areas and estimating their possible contribution to an increased water availability. MAR is compared to alternative water management measures, e.g., increased groundwater abstraction, in terms of costs and water availability potential. Results from GIS analyses of infiltration areas and groundwater storage, respectively proximity to surface water sources and surface water storage were classified into three categories of MAR suitability. An area of ca 7700 ha (2.5% of Gotland) was found to have good local conditions for MAR and an area of ca 22,700 ha (7.5% of Gotland) was found to have moderate local conditions for MAR. These results reveal the MAR potential on Gotland. The water supply potential of MAR in existing well fields was estimated to be about 35% of the forecasted drinking water supply and 7% of the total water demand gap in year 2045. It is similar in costs and water supply potential to increased surface water extraction.

Altered volcanic ash interbeds (bentonites) in the upper Katian of Baltoscandia indicate significant volcanic activity in neighbouring tectonically active areas. Katian bentonites in the East Baltic can be reliably correlated using sanidine phenocryst composition. Ratios of immobile trace elements TiO2, Nb, Zr and Th to Al2O3enable extension of the correlations to Scandinavia, where late diagenetic alterations could have caused recrystallization of sanidine phenocrysts. At least seven volcanic eruptions were recognized in Baltoscandian sections. Several bentonites found in deep-sea sediments are absent in shallow-sea sediments, indicating extensive breaks in sedimentation and erosion during late Katian and Hirnantian times. The areal distribution pattern of Katian bentonites in Baltoscandia indicates a volcanic source from the north or northwest (present-day orientation) from the margins of the Iapetus Palaeo-Ocean. Signatures of ultra-high-pressure metamorphism in the Seve Nappe (Central Sweden) and intrusions in the Helgeland Nappe Complex in Central Norway have been proposed as potential sources of the magmas that generated the volcanic ashes deposited in the East Baltic in Katian times. Geochemical similarities between Baltoscandian and Dob's Linn bentonites from southern Scotland suggest a common volcanic source in Katian times.

Twenty-three south-Swedish public supply wells were studied to assess pesticide pollution of regional groundwater resources. Relations between pesticide occurrence, hydrogeology, and land use were analyzed using Kohonen’s Self-Organizing Maps approach. Pesticides are demonstrated to be substantially present in regional groundwater, with detections in 18 wells. Concentrations above the drinking water threshold are confirmed for nine wells. Observations indicate considerable urban influence, and lagged effects of past, less restricted use. Modern, oxic waters from shallow, unconfined, unconsolidated or fracture-type bedrock aquifers appear particularly vulnerable. Least affected waters appear primarily associated with deeper wells, anoxic conditions, and more confined sediment aquifers lacking urban influence. Comprehensive, standardized monitoring of pesticides in groundwater need to be implemented nationwide to enable sound assessments of pollution status and trends, and to develop sound groundwater management plans in accordance with the Water Framework Directive. Further, existing water protection areas and associated regulations need to be reassessed.

Based on the Tingskullen drillcore, we present the first continuous carbon isotope stratigraphy from the Lower–Middle Ordovician “orthoceratite limestone” of Oland, Sweden. The extremely condensed Tremadocian and Floian stages include large gaps as well as the Ceratopyge Regressive Event and the widespread Evae transgression accompanied by prominent shifts in the δ 13C record. The Dapingian and Darriwilian stages are characterised by low sedimentation rates and a relatively complete sedimentary record. A total of 99 whole-rock samples were analysed for carbon isotope geochemistry from the Ordovician part of the succession (46 m thick). The most striking anomaly detected is the middle Darriwilian isotope carbon excursion (MDICE) that appears unusually well developed and complete for the region, and thus forms an important proxy for intercontinental correlation of the succession.

In central parts of the Scandinavian Caledonides, detrital zircon signatures provide evidence of the change in character of the Baltoscandian crystalline basement, from the characteristic Late Palaeoproterozoic granites of the Transscandinavian Igneous Belt (TIB, c. 1650–1850 Ma) in the foreland Autochthon to the typical, mainly Mesoproterozoic-age profile (c. 950–1700 Ma) of the Sveconorwegian Orogen of southwestern Scandinavia in the hinterland. Late Ediacaran to Early Cambrian shallow-marine Vemdal quartzites of the Jamtlandian Nappes (Lower Allochthon) provide strong bimodal signatures with TIB (1700–1800 Ma) and Sveconorwegian, sensu stricto (900–1150 Ma) ages dominant. Mid-Ordovician turbidites (Norraker Formation) of the Lower Allochthon in Sweden, sourced from the west, have unimodal signatures dominated by Sveconorwegian ages with peaks at 1000–1100 Ma, but with subordinate components of older Mesoproterozoic zircons (1200–1650 Ma). Latest Ordovician shallow-marine quartzites also yield bimodal signatures, but are more dispersed than in the Vemdal quartzites. In the greenschist facies lower parts of the Middle Allochthon, the Fuda (Offerdal Nappe) and Sarv Nappe signatures are either unimodal or bimodal (950–1100 and/or 1700–1850 Ma), with variable dominance of the younger or older group, and subordinate other Mesoproterozoic components. In the overlying, amphibolite to eclogite facies lower part of the Seve Nappe Complex, where the metasediments are dominated by feldspathic quartzites, calcsilicate-rich psammites and marbles, most units have bimodal signatures similar to the Sarv Nappes, but more dispersed; one has a unimodal signature very similar to the Ordovician turbidites of the Jamtlandian Nappes. In the overlying Upper Allochthon, Lower Koli (Baltica-proximal, Virisen Terrane), Late Ordovician quartzites provide unimodal signatures dominated by Sveconorwegian ages (sensu stricto). Further north in the Scandes, previously published zircon signatures in quartzites of the Lower Allochthon are similar to the Vemdal quartzites in Jamtland. Data from the Kalak Nappes at 70°N are in no way exotic to the Sveconorwegian Baltoscandian margin. They do show a Timanian influence (ages of c. 560–610 Ma), as would be expected from the palinspastic reconstructions of the nappes. Thus the detrital zircon signatures reported here and published elsewhere provide supporting evidence for a continuation northwards of the Sveconorwegian Orogen in the Neoproterozoic, from type areas in the south, along the Baltoscandian margin of Baltica into the high Arctic.

This paper reports on the geochemistry of the mid-Silurian Grotlingbo Bentonite, a ca. 0.1–0.4-m-thick and regionally important bentonite bed in Sweden and the East Baltic area. A series of eight samples, spaced by 5 cm, were taken from the Hunninge-1 drillcore in Gotland, Sweden, and were analysed in order to establish the vertical element composition and variation in the bentonite. The results show that the Gotlingbo Bentonite originates from one source magma and from one single eruption. The lowermost 0.1–0.15 m of the bentonite (compacted) was deposited from air-transport fall-out, whereas the upper portions have been reworked in a shallow-marine environment and re-deposited. Vertical differences in Ti and Zr within the Grotlingbo Bentonite mean that regional correlation of the bed may need several samples at each locality to be reliable.

Late Ordovician shelly faunas occur at several localities in the Ostersund area of Jamtland (Sweden) and developed against a background of intense and rapid global climate change. In the eastern part, approximately in the middle parts of the Krykas Quartzite, and in the western part in the uppermost Kogsta Siltstone changes in faunas and sedimentary patterns provide regional evidence of these global events. In both areas the faunas occur in shale and siltstone facies and are used to effect correlations between the eastern and western parts of the region, which show major differences in facies development. These sub-basins, situated on the margins of a developing mountain belt, reacted differently to global signals providing further evidence of the heterogeneous responses to climate change at the end of the Ordovician Period.

Zircon grains extracted from three sedimentary units within the Caledonian Lower Allochthon in Jamtland, central Sweden, were investigated for provenance studies using LA-ICP-MS. 207 Pb/ 206 Pb ages fall into the intervals: 3.1-1.7 Ga (Ronnofors Conglomerate), 3.2-1.4 Ga (Ede Quartzite), and 2.6-1.1 Ga (Kyrkas Quartzite). The age distribution of the Ronnofors and Kyrkas units vary sufficiently to suggest different source areas. The Ede Quartzite constitutes a mixture of the Kyrkas and Ronnofors provenance groups. The zircon age spectrum of the Kyrkas Quartzite reflects the typical age group present in the Jamtland basin in late Ordovician. In comparison, most zircon grains from the Ronnofors Conglomerate were derived from a local source, and only a small portion of these grains is characteristic for the basin. The Ede Quartzite contains a mixture of the typical basinal and, to a lesser extent, locally derived material. The variation in age distribution between the Ede and Kyrkas Quartzites reflects differ- ent dominating source areas. Tectonic activities along a shear zone (a continuation of SEDZ), which runs through the Ede and Kyrkas areas may be responsible for the noted differences in source areas. A deriva- tion from older sedimentary rocks to the present west-southwest and/or the Southwest Scandinavian Domain is suggested for the younger parts (

The Late Ordovician–Early Silurian succession in Jämtland includes the marine Kogsta Siltstone, which is unconformably overlain by the shallow-water Ede Quartzite that grades into the open-marine Berge Limestone. A Hirnantia shelly fauna dates the uppermost Kogsta Siltstone as Hirnantian, and shelly fossils indicate an Aeronian age for the Berge Limestone. Biostratigraphically highly diagnostic conodonts of the early-middle Aeronian Pranognathus tenuis Zone provide the first firm date of the Upper Ede Quartzite and the lowermost Berge Limestone. The Lower Ede Quartzite has not yielded fossils, but sedimentological data suggest it to be of Hirnantian age and reflect the glacio-eustatic low-stand. The contact between the Lower and Upper Ede Quartzite, here taken to be the Ordovician–Silurian boundary, appears to be an unconformity associated with a stratigraphic gap that at least includes the Rhuddanian Stage. The biostratigraphically important conodonts Pranognathus tenuis, Kockelella? manitoulinensis, and Pranognathus siluricus are recorded from Sweden for the first time, and these and other conodonts are used for correlations with coeval units in Europe and North America. In a regional review of Aeronian conodont faunas, three intergrading, apparently depth-related, conodont biofacies are recognised, the Jämtland conodonts representing the one characteristic of the shallowest water.

The Upper Ordovician Kyrkås Quartzite Formation at the Nifsåsen Quarry (Jämtland, Sweden) exhibits c. 90 m of siliciclastic sedimentary rocks deposited on a shallow shelf at the craton-attached part of the Caledonian foreland basin. Five lithologies are distinguished, including claystone, mudstone, siltstone, subarkose and sublitharenite. Based on these five lithologies, sedimentary structures and biota, three marine facies associations are defined: the Mudstone association (FA1) deposited close to storm wave base, the Sandstone/mudstone association (FA2) formed between storm and fair-weather wave bases, and the Sandstone association (FA3) accumulated above fair-weather wave base. The facies associations are arranged in two sequences, c. 50 and 40 m thick, separated by a transgressive surface, indicating repeated shoreline progradation. Both sequences commence with marine heterolithic shales and siltstones, with upwardly increasing frequency of tempestites. Continued shoaling is indicated by a dominance of hummocky and trough (locally tabular) cross-stratified sandstone beds in the upper part of each sequence. Sand beds are increasingly amalgamated up-sequence, reflecting progressively diminishing accommodation space. The depositional style and sedimentary structures indicate that the study area was storm-dominated with an abundant supply of siliciclastic material. Biostratigraphic data tie the depositional changes to the globally recognized Late Ordovician (Hirnantian) glacial interval. These data suggest that the first sequence was formed during the initial phase of regression in the earliest Hirnantian. The lowermost part of the overlying sequence contains elements of a typical Hirnantia fauna followed by beds yielding Normalograptus persculptus, suggesting a second regressive cycle in the Jämtland basin during the early N. persculptus Biozone.

A study of the Upper Ordovician-Lower Silurian strata in Jamtland, central Sweden, shows that large-scale changes in shelf deposition took place close to the systems boundary. These changes include unconformity development and the replacement of a siliciclastic shelf with a carbonate-dominated shelf, suggesting the interaction of allocyclic controls such as changing eustatic sea-level and climate. The 6-m-thick Ede Formation is a key lithosome for interpretation of this transition. Its sediments were deposited in the Caledonian foreland basin, situated east of the closing Iapetus Ocean on the western margin of the Baltic craton. A major part of the late. Caradoc to late Ashgill (into the Hirnantian) was characterised by continuous and uniform deposition over wide areas (Kogsta Formation), whereas erosional surfaces and complex lateral facies relationships characterise the Ordovician-Silurian boundary strata (Ede Formation and lateral equivalents). The Ede Formation represents the end of terrigenous deposition, which in the middle Aeronian was followed by regional expansion of carbonate deposition (Berge Formation). A syn-sedimentary erosional surface, with at least I in of relief locally, forms the lower boundary of the Ede Formation. This surface is overlain by two types of conglomerate. Lower parts of the Ede Formation consist of medium to thick-bedded quartzites. A second erosional surface with only minor (few centimetres) relief occurs on top of these quartzites. The upper parts of the Ede Formation consist of a thin, basal favositid biostrome overlain by thin bedded, calcareous sandstones, limestones and intensely bioturbated shales. Analysis of stratigraphic boundaries and the facies succession suggests that the lower Ede Formation represents a major downward shift in coastal onlap and by-pass sedimentation that created the lower erosional surface. The erosional surface in the middle of the Ede Formation is inferred to have formed during the subsequent maximum lowstand or as a ravinement surface, and is interpreted as an unconformity. The succession is subdivided into four facies associations, each corresponding to a specific systems tract: (a) a Shale-Siltstone Association (uppermost Kogsta Formation), deposited during a highstand situation in mid-outer shelf areas; (b) a Quartzite Association (the lower Ede Formation), deposited during forced regression in a shoreface environment; (c) a Mixed Carbonate-Siliciclastic Association (the upper Ede Formation), deposited during transgression in a wave-dominated, proximal shelf environment when elastic supply was reduced; and (d) a Micritic Limestone Association (lowermost Berge Formation), deposited during a second highstand situation in a low-energy, offshore environment. Conodont data, together with a previously reported Hirnantia fauna, constrain the position of the Ordovician-Silurian boundary to the lower 1.65 m of the Ede Formation, or less likely, to the uppermost metre of the underlying Kogsta Formation, i.e., within a 2.65-m-thick uncertainty interval. The base of the Berge Formation is about 4 m above the top of the uncertainty interval, and is dated as being mid-Aeronian in age, suggesting condensation and/or a hiatus close to, or at, the Ordovician-Silurian boundary. These data tie the unconformity and the regional facies change from a siliciclastic to a carbonate-dominated shelf to Late Ordovician-Early Silurian eustatic and climatic changes. (C) 2004 Elsevier B.V. All rights reserved.

As water scarcity and drought become more common, planning to avoid their consequences becomes crucial. Measures to prevent the impact of new climate conditions are expected to be extensive, costly and associated with major uncertainties. It is therefore necessary that policymakers and practitioners in both the public and private sector can compare possible mitigation measures in order to make economically rational investment decisions. For this to be successful, decision-makers need relevant decision support. This paper presents a novel approach of constructing marginal abatement cost curves for comparing water scarcity mitigation measures while taking the underlying uncertainties into account. Uncertainties in input variables are represented by probability distributions and calculations are performed using Monte Carlo simulations. This approach is applied on the island of Gotland, one of the most water-stressed parts of Sweden, to provide the first marginal abatement cost curve in Europe for water scarcity mitigation in which municipal, agricultural, industrial and household measures are compared. The results show that the agricultural measure of on-farm storage has the greatest potential to increase water availability on the island. Among municipal measures, increased groundwater extraction and desalination offer the greatest potential, although desalination is almost 25 times more costly per cubic meter. The most cost-effective measure is linked to hot water savings in the hotel industry. The approach presented provides a quantitative visualization of the financial trade-offs and uncertainties implied by different mitigation measures. It provides critical economic insights for all parties concerned and is thus an important basis for decision-making.