Carbonate platform evolution and conodont stratigraphy during the middle Silurian Mulde Event, Gotland, Sweden

Evidence from sedimentology and conodont biostratigraphy is used to reinterpret the mid-Homerian (Late Wenlock) succession on Gotland, Sweden. A new conodont zonation includes from below: the Ozarkodina bohemica longa Zone (including five subzones), the Kockelella ortus absidata Zone and the Ctenognathodus murchisoni Zone (two taxa are named, Ozarkodina bohemica longa and Pseudooneotodus linguicornis). These new zones are integrated with facies in order to correlate strata and infer the major depositional environments and the controls on deposition during the mid-Homerian Mulde Event. Reef-associated and skeletal carbonate deposition predominated before and after the event, i.e. during the uppermost O. s. sagitta Zone and, again, in the C. murchisoni Zone. These periods are characterized by the expansion of reefs and shoal facies across marls in the topmost Slite Group on eastern Gotland and in the lower parts of the Klinteberg Formation on western Gotland, respectively. The intervening O. b. longa and K. o. absidata zones are initially characterized by rapid facies changes, including siliciclastic deposition, and later stabilisation of a carbonate depositional system. The composition of sediments and depositional rates are closely related to the creation and destruction of accommodation space and reflects a classical case of depositional bias of the carbonate and siliciclastic depositional systems. Based on coastline migration, stratal boundaries, and the stratigraphic position of major reef belts, several facies associations can be fitted into a sequence stratigraphic model for platform evolution. A highstand systems tract (HST) situation prevailed prior to, and during the early part of the event; the upper Slite Group including the lower Frjel Formation. This HST was characterized by prolific skeletal production and regional reef development except for during the latest stage when carbonate production declined at the onset of the Mulde Event. Platform growth was inhibited during a following regressive systems tract (RST) when regional siliciclastic deposition predominated; the Gannarve Member. The subsequent lowstand resulted in regional emersion and karstification, i.e. a complete termination of the platform. The post-extinction transgressive systems tract (TST) is exclusively composed of non-skeletal carbonates; the Bara Member of the Halla Formation. Re-occurrence of reefs and a prolific skeletal production marks platform recovery during a second HST; the remaining Halla and the lower Klinteberg formations. Integration of high-resolution biostratigraphy and sequence stratigraphy reveals that the major physical control on platform evolution was a 5th order eustatic sea-level change during an early part of the Mulde Event, and that the bulk of the strata accumulated when the platform aggraded and prograded during the highstand systems tracts. Thus, Silurian oceanic events and associated sea-level changes had profound impact on the neritic carbonate system. The Gotland-based middle and late Homerian sea-level curve shows two rapid regressions, both leading to truncation of highstand systems tracts. The first lowstand occurred at the very end of the C. lundgreni Chron, and the second at the end of the Co.? ludensis Chron. The intervening interval was characterized by stillstand or possibly slow transgression

Clinical Course of Postoperative Atrial Fibrillation After Cardiac Surgery and Long-term Outcome

Funding Information: The study was supported by the Swedish Heart-Lung Foundation (grant 20180560 to AJ), the Swedish state (ALFGBG-725131 to AJ) under the agreement between the Swedish government and the county councils concerning economic support of research and education of doctors (ALF agreement), Region Västra Götaland (grant VGFOUREG-847811 to AJ and grant VGFOUREG-648981 to AT), and Wilhelm and Martina Lundgrens Foundation (grant 2019-3110 to AT). The authors had full freedom of investigation and full control of the design of the study, analysis of data, and production of the written report. Dr Jeppsson discloses a financial relationship with Boehringer-Ingelheim, XVIVO, Portola, Baxter, and LFB; Dr Taha with Bayer; Dr Bergfeldt with Bayer, Boehringer Ingelheim, and Sanofi. Funding Information: The study was supported by the Swedish Heart-Lung Foundation (grant 20180560 to AJ), the Swedish state (ALFGBG-725131 to AJ) under the agreement between the Swedish government and the county councils concerning economic support of research and education of doctors (ALF agreement), Region Västra Götaland (grant VGFOUREG-847811 to AJ and grant VGFOUREG-648981 to AT), and Wilhelm and Martina Lundgrens Foundation (grant 2019-3110 to AT). The authors had full freedom of investigation and full control of the design of the study, analysis of data, and production of the written report. Publisher Copyright: © 2022 The Society of Thoracic SurgeonsBackground: New-onset postoperative atrial fibrillation (POAF) after cardiac surgery is associated with worse short- and long-term outcomes. Although the clinical presentation of POAF varies substantially, almost all studies model it with a dichotomous yes or no variable. We explored potential associations between the clinical course of POAF and long-term outcome. Methods: This retrospective, observational, single-center study included 6435 coronary artery bypass grafting and/or valve patients between 2010 and 2018. POAF patients were grouped into spontaneous/pharmacologic conversion to sinus rhythm, sinus rhythm after electrical cardioversion, and sustained AF at discharge. Multivariable Cox regression models adjusted for age, sex, type of surgery, comorbidities, and early-initiated oral anticoagulation were used to study associations between the clinical course of POAF and long-term risk for mortality, ischemic stroke, thromboembolic events, heart failure hospitalization, and major bleeding. Median follow-up time was 3.8 years (range, 0-8.3). Results: POAF occurred in 2172 patients (33.8%), 94.9% of whom converted to sinus rhythm before discharge. Of these, 73.6% converted spontaneously or with pharmacologic treatment and 26.4% after electrical cardioversion. Both sustained AF and electrical cardioversion were independently associated with an increased long-term risk for heart failure (adjusted hazard ratio for sustained AF at discharge, 2.55 [95% confidence interval, 1.65-3.93; P < .001]; adjusted hazard ratio for electrical cardioversion, 1.28 [95% confidence interval, 1.00-1.65; P = .049]) but not with increased long-term risk for death, thromboembolic complications, or bleeding. Conclusions: A more complicated POAF course is associated with increased long-term risk for heart failure hospitalization but not for all-cause mortality or thromboembolic complications.Peer reviewe

Associations between new-onset postoperative atrial fibrillation and long-term outcome in patients undergoing surgical aortic valve replacement

© The Author(s) 2023. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.OBJECTIVES: Data on prognostic implications of new-onset postoperative atrial fibrillation (POAF) after surgical aortic valve replacement (SAVR) is limited. We sought to explore associations between POAF, early initiated oral anticoagulation (OAC) and long-term outcome after SAVR and combined SAVR + coronary artery bypass grafting (CABG). METHODS: This is a retrospective, population-based study including all isolated SAVR (n = 7038) and combined SAVR and CABG patients (n = 3854) without a history of preoperative atrial fibrillation (AF) in Sweden 2007-2017. Individual patient data were merged from 4 nationwide registries. Inverse probability of treatment weighting-adjusted Cox regression models were employed separately in SAVR and SAVR + CABG patients. The median follow-up time was 4.7 years (range 0-10 years). RESULTS: POAF occurred in 44.5% and 50.7% of SAVR and SAVR + CABG patients, respectively. In SAVR patients, POAF was associated with increased long-term risk of death [adjusted hazard ratio (aHR) 1.21 (95% confidence interval 1.06-1.37)], ischaemic stroke [aHR 1.32 (1.08-1.59)], any thromboembolism, heart failure hospitalization and recurrent AF. In SAVR + CABG, POAF was associated with death [aHR 1.31 (1.14-1.51)], recurrent AF and heart failure, but not with ischaemic stroke [aHR 1.04 (0.84-1.29)] or thromboembolism. OAC was dispensed within 30 days after discharge to 67.0% and 65.9%, respectively, of SAVR and SAVR + CABG patients with POAF. Early initiated OAC was not associated with reduced risk of death, ischaemic stroke or thromboembolism in any group of patients. CONCLUSIONS: POAF after SAVR is associated with an increased risk of long-term mortality and morbidity. Further studies are warranted to clarify the role of OAC in SAVR patients with POAF.Peer reviewe

Biases in the recovery and interpretation of micropalaeontological data

Bias caused by collecting and processing bulk samples is largely independent of what fossil clade or mineral is searched for. Instead, different methods bias the data to a different, frequently very large, degree. Furthermore, biases accumulate with each recovery step, and the sum may be extreme unless appropriate methods to minimize it are employed. The effects depend on what the data are used for, e.g. establishing range ends (zonal boundaries), taxonomy (frequencies as an aid to, for example, conodont apparatus reconstruction) and ecology (relative frequency in a fauna, frequency/kg, faunal diversity). However, the best published methods remove calcium carbonate and dolomite without bias. All rocks with such cement can be broken down without bias, and so can some claystones with little lime. The bias caused by concentration can be measured, kept low, and documented. Removal of clay is an exception: screening or decanting removes all small elements. Extraction methods should be stated in all publications so that the data can be assessed more fully and quoted property. Information about the acid methods, screen hole diameter and collection size arc especially important because these Usually cause the greatest bias. Reliability of observed range ends increases with increasing number of specimens and with decreasing sample distance (recollecting near the boundary). Samples that are too small, yielding subadequate collections, can strongly bias placement of zonal boundaries and implied diversity. Not taking the uncertainty intervals of zonal boundaries into account may result in artificially extended observed ranges of other species. Methodological progress over the last 25 years has increased the potential average yield per hour of manpower over 100 times for samples yielding fewer than 100 elements/kg. This has made it possible to overcome most of the biases outlined herein. Similarly, taking the biases that are known or are likely to have affected data into account allows levels of precision in data to be evaluated and published

Conodont-based revisions of the late Ludfordian on Gotland, Sweden

The Late Ludlow topmost Hemse-Burgsvik succession includes more substantial and more rapid facies changes than most older and younger intervals on Gotland. A revised conodont zonation for this interval includes three zones, the Polygnathoides siluricus, the Icriodontid, and the Ozarkodina snajdri zones and four subzones, the Upper P. siluricus, the Lower, the Middle and the Upper Icriodonfid subzones. The three zones are approximately coeval with the Neocucullograptus kozlowskii graptolite fauna, the succeeding impoverished graptolite fauna and the Monograptus baltictis/Pseudomonoclimacis latilobus Zone (= the lower M. formosus Zone), respectively. The new zonation permits the first high-resolution correlations across Gotland, despite very large differences in facies from SW to NE. Another result is a more detailed stratigraphic subdivision and revised boundaries of most of the units. The Mill-klint, the main and the Botvide members of the Nar Fm. (new, the upper part of the Hemse Group), the lower, middle, and upper Eke Fm., and the Burgsvik Fm. are distinguished. Well known names are kept, as far as possible, but the lateral extent of their boundaries is revised, resulting in a considerable increase in precision and very different thickness data, e.g. the Ludlow is calculated to be somewhere between 337 and 425 m instead of the 215 m given hitherto. Faults or disturbances with similar effects are identified for the first time on Gotland. Silurognathus maximus is named

The lower Wenlock Hangvar Formation - a sequence previously split between the Hogklint and Slite beds (Silurian, Gotland, Sweden)

Conodont faunas solve the long-standing problem regarding the relationships between the Hogklint, Tofta, and lower Slite. The name Hangvar Formation is here formally introduced for the strata identified between the Tofta Formation and the Slite Group. The Hangvar Fm. includes marls as far SW as near Paviken (previously Slite Marl), argillaceous limestones (seen only in the most distal areas accessible) followed by reefs and associated limestones SE and NE of Visby (previously Slite Beds, mostly units a and b) and northeastwards to eastern Faro (from the area around Kappelshamnsviken and NE-wards, previously Hogklint Beds). The formation is delimited below and above by prominent discontinuities i.e. sequence boundaries. These coincide with biostratigraphical boundaries, i.e. they probably represent relatively long time intervals. The Hangvar formation includes two subzones, hence lower and upper parts can be distinguished. The upper Hangvar reef generation is the third in the Wenlock of Gotland

The Silurian Mulde Event and a scenario for secundo-secundo events

Graphic correlation using graptolites and conodonts provides a high-resolution timescale for correlating from coastal to deep oceanic sections and, thereby, also a detailed record of the sequence of changes during the Mulde Secundo-Secundo Event. That interval includes sedimentary facies otherwise unknown in older Wenlock to early Ludlow strata on Gotland. The identified sequence of changes includes a detailed record of, in order: two extinctions (Datum points 1 and 1-5); widespread deposition of carbon-rich sediments extensive enough to cause a delta(13)C increase of c. 4.8parts per thousand, the onset, maximum and end of a sea-level fall and rise of at least 16m during 30 kyr; a third extinction (Datum 2); a disaster fauna; and a slow faunal recovery. Thus, a secondary result of the event was a weakened greenhouse effect triggering a glaciation: the Gannarve Glaciation (new term). The order of changes proves that regression did not cause the extinctions. Faunal and sea-level changes, as well as the sedimentary succession, fit well with predictions based on an oceanic model. Extinctions were primarily caused by a severe drop in primary planktonic productivity, causing starvation among planktonic larvae in non-coastal settings. The Grotlingbo Bentonite (new term), the thickest in the Wenlock of Gotland, was deposited across the basin shortly after Datum 2. Temporal resolution is high enough to permit some comparison with Quaternary glaciations

Wenlock metabentonites from Gotland, Sweden: geochemistry, sources and potential as chemostratigraphic markers

Two metabentonite suites occur within the Wenlock limestones and marls of Gotland, one within the Slite Formation (M. belophorus to the C. ellesae biozones) and the other in the Mulde Formation (G. nassaM. dubius Biozone). Their geochemical characteristics based on rare-earth element (REE) distributions in apatite crystals separated from the metabentonites suggest origins from three separate volcanic sources. One of these sources has an alkaline affinity, reflected in relatively high levels of Th, Nb and Zr, which suggests that it may have lain over thickening continental crust during the waning stages of the closure of the Tornquist Sea, while the other two represent calc-alkaline magmas. The source of the volcanic ash is placed some 400 km to the southwest of Gotland, on the TornquistTeysseyre Zone, which is the northernmost expression of the Trans-European Suture Zone. Distinctive differences in REE distribution in apatite from these metabentonites should assist in future correlation studies in Wenlock stratigraphy, both within the Baltic region and further afield

Graptolites from the Lower and Upper Visby formations of NW Gotland

Graptolites are uncommon in the Lower Visby Formation. Specimens derived from conodont residues are predominantly members of the long ranging genus Retiolites, with single specimens recorded of Paraplectograptus and Monograptus priodon. Only one graptolite, a specimen of Cyrtograptus bohemicus, has been recovered from the Upper Visby Formation. This is the only biostratigraphically important species in the collection: it has a range of murchisoni Biozone to lower riccartonensis Biozone