Integrated Cambrian biostratigraphy and carbon isotope chemostratigraphy of the Grönhögen-2015 drill core, Öland, Sweden

2018 ◽  
Vol 156 (06) ◽  
pp. 935-949 ◽  
Author(s):  
PER AHLBERG ◽  
FRANS LUNDBERG ◽  
MIKAEL ERLSTRÖM ◽  
MIKAEL CALNER ◽  
ANDERS LINDSKOG ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Global Scale ◽  
Carbonate Facies ◽  
Southern Sweden ◽  
Middle Ordovician ◽  
Alum Shale ◽  
Carbon Isotope Excursion ◽  
Upper Stage ◽  
Shale Formation ◽  
Isotope Analyses

AbstractThe 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.

Integrated conodont biostratigraphy and carbon isotope chemostratigraphy in the Lower–Middle Ordovician of southern Sweden reveals a complete record of the MDICE

2016 ◽  
Vol 154 (2) ◽  
pp. 334-353 ◽  
Author(s):  
RONGCHANG WU ◽  
MIKAEL CALNER ◽  
OLIVER LEHNERT
Keyword(s):  
North America ◽  
Carbon Isotope ◽  
South China ◽  
North China ◽  
Southern Sweden ◽  
Conodont Biostratigraphy ◽  
Middle Ordovician ◽  
The Core ◽  
Core Section ◽  
Argentine Precordillera

AbstractOne of the few and most complete records of the MDICE (Middle Darriwilian Isotope Carbon Excursion) is herein documented from Baltoscandia. Based on a core section penetrating the condensed Lower–Middle Ordovician succession (~46 m) on the island of Öland, southeastern Sweden, we provide an integrated scheme for carbon isotope chemostratigraphy (313 samples) and conodont biostratigraphy (29 samples) for this period. The carbonate succession in the Tingskullen core records 12 conodont zones and 6 subzones, including theOepikodus evae, Trapezognathus diprion, Baltoniodus triangularis, B. navis, B. norrlandicus, Lenodus antivariabilis, L. variabilis, Yangtzeplacognathus crassus, Eoplacognathus pseudoplanus(Microzarkodina hagetianaandMicrozarkodina ozarkodellasubzones),E. suecicus, Pygodus serra(E. foliaceus, E. reclinatus, E. robustusandE. lindstroemisubzones) andPygodus anserinuszones in ascending order. The δ13Ccarbrecord reveals an apparently complete record of the MDICE, including a rising limb, a well-defined peak and a falling limb. The anomaly covers a thickness ofc. 27 m in the core and spans theEoplacognathus pseudoplanus, E. suecicus, Pygodus serraandP. anserinusconodont zones. Combined with the new, detailed conodont biostratigraphy, the MDICE in the Tingskullen core can be used for detailed correlation with successions from Baltica, North America, the Argentine Precordillera, South China and North China.

Skeletal carbonate productivity and phosphogenesis at the lower–middle Cambrian transition of Scania, southern Sweden

2009 ◽  
Vol 147 (1) ◽  
pp. 59-76 ◽  
Author(s):  
J. JAVIER ÁLVARO ◽  
PER AHLBERG ◽  
NIKLAS AXHEIMER
Keyword(s):  
Primary Productivity ◽  
Microbial Mats ◽  
High Energy ◽  
Nutrient Supply ◽  
Energy Conditions ◽  
Southern Sweden ◽  
Middle Cambrian ◽  
Alum Shale ◽  
Shale Formation ◽  
Reducing Environment

AbstractThe lower–middle Cambrian transitional interval of Scania is largely represented by condensed limestone beds, lithostratigraphically grouped in the Gislöv Formation (1–5.7 m thick), and the Forsemölla and Exsulans Limestone beds (lower part of the Alum Shale Formation, up to 4 m thick). The strata display a combination of skeletal carbonate productivity, episodic nucleation of phosphate hardground nodules, and polyphase reworking recorded on a platform bordering the NW corner of Baltica. The shell accumulations can be subdivided into three deepening-upward parasequences, separated by distinct erosive unconformities. The parasequences correspond biostratigraphically to the Holmia kjerulfi, Ornamentaspis? linnarssoni and Ptychagnostus gibbus zones, the latter two generally being separated by a stratigraphic gap that includes the middle Cambrian Acadoparadoxides oelandicus Superzone. Except for the Exsulans Limestone, the carbonates reflect development of a prolific epibenthic biota, dominated by filter-feeding nonreefal chancelloriid–echinoderm–sponge meadows, rich in trilobites and brachiopods, and which were subjected to high-energy conditions. The absence of microbial mats or veneers encrusting the erosive surfaces of these event-concentration low-relief shoal complexes may be related to long hiatal episodes resulting in microboring proliferation. High levels of nutrient supply resulted in high primary productivity, eutrophic conditions, glauconite precipitation, phosphogenesis (in some case microbially mediated) and microendolithic infestation. An early-diagenetic mildly reducing environment is suggested by the presence of authigenic (subsequently reworked) pyrite, which contrasts with the syndepositional normal oxygenated conditions reflected by macroburrowing and the abundance of benthic fossils.

scholarly journals Stratigraphy and geochemical composition of the Cambrian Alum Shale Formation in the Porsgrunn core, Skien–Langesund district, southern Norway.

2018 ◽  
Vol 66 ◽  
pp. 1-20
Author(s):  
Niels Hemmingsen Schovsbo ◽  
Arne Thorshøj Nielsen ◽  
Andreas Olaus Harstad ◽  
David L. Bruton
Keyword(s):  
Gamma Ray ◽  
Geochemical Composition ◽  
Middle Cambrian ◽  
Alum Shale ◽  
Carbon Isotope Excursion ◽  
Lower Ordovician ◽  
Shale Formation ◽  
Sedimentary Succession ◽  
Southern Norway ◽  
Spice Event

The fully cored BHD-03-99 borehole (hereafter referred to as the Porsgrunn borehole and core) penetrated Ordovician and Cambrian strata in the Skien–Langesund district, southern part of the Oslo region in Norway. Hand-held X-ray fluorescence (HH-XRF) measurements combined with spectral gamma ray and density core scanning of the Middle Cambrian – Furongian Alum Shale Formation have been made and compared with similar measurements obtained on Alum Shale cores from Scania (southernmost Sweden) and Bornholm (Denmark). The Porsgrunn drill site is located in an area that was only mildly overprinted by Caledonian tectonics and represents one of the few sites in the Oslo area where a nearly untectonised sedimentary succession can be studied in terms of thickness and geochemistry. The Alum Shale Formation is 28.8 m thick in the Porsgrunn core, excluding the thickness of five 0.9–5.5 m thick dolerite sills of assumed Permian age. In the Alum Shale Formation the bulk densities are around 2.7 g/cm3 with a slightly decreasing trend up through the formation. The shale has total organic carbon (TOC) values up to 14 wt%, which is comparable to the TOC levels for the Alum Shale elsewhere in the Oslo area and for dry gas matured Alum Shale in Scania and Bornholm. The basal Furongian is characterised by a gamma ray low and an increase in Mo interpreted to reflect the Steptoean Positive Carbon Isotope Excursion (SPICE) event. The Porsgrunn core data suggest that the Mo concentration remained high also after the SPICE event. Characteristic, readily identified features in the gamma log motif are named the Andrarum gamma low (AGL), base Furongian gamma low (BFGL), Olenus triple gamma spike (OTGS) and the Peltura gamma spike (PGS). No Lower Ordovician Alum Shale is present. The 14.8 m thick Furongian part of the Alum Shale represents the Olenus, Parabolina, Leptoplastus, Protopeltura and Peltura trilobite superzones judging from log-stratigraphic correlations to Scania and Bornholm. The Middle Cambrian interval is 14.0 m thick and includes the Exsulans Limestone Bed and 1.4 m of quartz sandstone. A 0.3 m thick primary limestone bed may be an equivalent to the Andrarum Limestone Bed. The succession represents the Paradoxides paradoxissimus and P. forchhammeri superzones. The Alum Shale Formation rests atop the 13.0 m thick Lower Cambrian Stokkevannet sandstone (new informal name) that in turn directly overlies the basement. Overall, the stratigraphic development of the comparatively thin Alum Shale Formation resembles the condensed sequence seen on Bornholm.

Extending the record of the Lomagundi–Jatuli carbon isotope excursion in the Labrador Trough, Canada

2020 ◽  
Vol 57 (9) ◽  
pp. 1089-1102
Author(s):  
Malcolm S.W. Hodgskiss ◽  
Kelsey G. Lamothe ◽  
Galen P. Halverson ◽  
Erik A. Sperling
Keyword(s):  
High Resolution ◽  
Water Column ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Large Range ◽  
Authigenic Carbonate ◽  
Elemental Ratios ◽  
Carbonate Carbon ◽  
Carbon Isotope Excursion ◽  
Isotope Analyses

The Labrador Trough in northern Québec and Labrador is a 900 km long Rhyacian–Orosirian orogenic belt containing mixed sedimentary–volcanic successions. Despite having been studied intensively since the 1940s, relatively few chemostratigraphic studies have been conducted. To improve our understanding of the Labrador Trough in the context of Earth history, and better constrain the local record of the Lomagundi–Jatuli carbon isotope excursion, high-resolution sampling and carbon isotope analyses of the Le Fer and Denault formations were conducted. Carbonate carbon isotopes (δ13C) in the Le Fer Formation record a large range in values from −4.4‰ to +6.9‰. This large range is likely attributable to a combination of post-depositional alteration and variable abundance of authigenic carbonate minerals; elemental ratios suggest that the most 13C-enriched samples reflect the composition of the water column at the time of deposition. Cumulatively, these data suggest that the Lomagundi–Jatuli Excursion was ongoing during deposition of the Le Fer Formation, approximately 2 km higher in the stratigraphy than previously recognised. However, the possibility of a post-Lomagundi–Jatuli Excursion carbon isotope event cannot conclusively be ruled out. The directly overlying Denault Formation records a range in δ13C values, from −0.5‰ to +4.3‰, suggesting that it was deposited after the conclusion of the Lomagundi–Jatuli Excursion and that the contact between the Le Fer and Denault formations occurred sometime during the transition out of the Lomagundi–Jatuli Excursion, ca. 2106 to 2057 Ma.

Conodont biostratigraphy and carbon isotope stratigraphy of the Middle Ordovician (Darriwilian) Komstad Limestone, southern Sweden

GFF ◽  
2018 ◽  
Vol 140 (1) ◽  
pp. 44-54 ◽  
Author(s):  
Rong-Chang Wu ◽  
Mikael Calner ◽  
Oliver Lehnert ◽  
Anders Lindskog ◽  
Michael Joachimski
Keyword(s):  
Carbon Isotope ◽  
Southern Sweden ◽  
Conodont Biostratigraphy ◽  
Carbon Isotope Stratigraphy ◽  
Middle Ordovician ◽  
Isotope Stratigraphy

scholarly journals Gamma-ray log correlation and stratigraphic architecture of the Cambro-Ordovician Alum Shale Formation on Bornholm, Denmark: Evidence for differential syndepositional isostasy

2018 ◽  
Vol 66 ◽  
pp. 237-273 ◽  
Author(s):  
Arne Thorshøj Nielsen ◽  
Niels Hemmingsen Schovsbo ◽  
Kurt Klitten ◽  
David Woollhead ◽  
Christian Mac Ørum Rasmussen
Keyword(s):  
Gamma Ray ◽  
Uranium Content ◽  
Middle Ordovician ◽  
Alum Shale ◽  
Stratigraphic Architecture ◽  
Lower Ordovician ◽  
Stress Changes ◽  
Shale Formation ◽  
Thickness Variations ◽  
The Individual

The Cambro–Ordovician Alum Shale Formation on Bornholm, Denmark, is in total 26.7 to ≥ 34.9 m thick in nine boreholes, but may be up to ~39 m thick. The well sections are correlated using gamma-ray logs supplemented in some boreholes with resistivity and sonic logs. The gamma radiation of the ‘hot’ Alum Shale Formation primarily reflects the uranium content, which is moderately high in the Miaolingian (≈ middle Cambrian) and Tremadocian (Lower Ordovician), and very high in the Furongian (≈ upper Cambrian). The log pattern is calibrated with the detailed biozonation established in the Gislövshammar-1 and -2 wells in south-eastern Skåne, Sweden. Except for the Eccaparadoxides oelandicus Superzone, all superzones known from the Alum Shale in Scandinavia are also developed on Bornholm, but not all zones. On Bornholm, the Miaolingian interval is 7.2–11.9 m thick, the Furongian is 16.4–22.8 m thick and the Tremadocian is 2.5–4.0 m thick. The Miaolingian strata exhibit no systematic thickness variations across southern Bornholm, whereas the Furongian Parabolina, Peltura and Acerocarina Superzones and, less pronounced, the Tremadocian, show increased condensation towards the south-east. In comparison with Skåne, the Alum Shale Formation is overall strongly condensed on Bornholm, but different stratigraphic levels show variable developments. The Miaolingian Paradoxides paradoxissimus Superzone is thus extremely condensed and incomplete, whereas the Paradoxides forchhammeri Superzone has almost the same thickness as in Skåne, and locally is even thicker. The Furongian Olenus and Parabolina Superzones are slightly thinner than in Skåne while the Protopeltura, Peltura and Acerocarina Superzones are half as thick or less. The Tremadocian is also much thinner on Bornholm. The Furongian Olenus scanicus–O. rotundatus and Parabolina brevispina Zones seem to be developed on Bornholm, and a thin ‘Leptoplastus neglectus’ Zone is also possibly present. The ‘Parabolina megalops’ Zone in the upper part of the Peltura Superzone appears to be absent. It is impossible to distinguish the individual thin zones in the lower part of the Acerocarina Superzone using wireline logs. A thin veneer of the Lower Ordovician Tøyen Formation, hitherto considered absent on Bornholm, is described from the Billegrav-2 core. It may also be present in the uncored Sømarken-3 and -4 wells. The Middle Ordovician Komstad Limestone Formation thins from c. 4.0–4.7 m in the Læså area to 0.1– c. 2.5 m in the Øleå area. The general decrease in thickness of Cambro–Ordovician strata from Skåne to Bornholm and also within Bornholm from the Læså to the Øleå area is inferred to reflect isostatic uplift of the southern margin of Baltica commencing with the terminal 'early' Cambrian Hawke Bay Event and lasting until the Late Ordovician. In detail, several uplift and subsidence phases can be discerned. The isostatic adjustments are surmised to reflect stress changes related to ongoing plate tectonic processes in the adjacent closing Tornquist Sea.

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