scholarly journals Monoceratella (Ostracoda) from the Silurian of Washington Land, North Greenland

1980 ◽  
Vol 101 ◽  
pp. 37-43
Author(s):  
P.D Lane
Keyword(s):  
Upper Ordovician ◽  
Middle Ordovician ◽  
Lower Silurian ◽  
North Greenland

Monoceratella mazos n. sp. is described from the Lower Silurian of Washington Land, western North Greenland. The occurrence, together with others from the Upper Ordovician and Devonian, emphasises the possibility of homeomorphy within the otherwise typically Middle Ordovician genus Monoceratella.

scholarly journals Middle–Upper Ordovician and Silurian stratigraphy and basin development in southernmost Scandinavia

1969 ◽  
Vol 35 ◽  
pp. 39-42 ◽  
Author(s):  
Niels H. Schovsbo ◽  
Arne T. Nielsen ◽  
Mikael Erlström
Keyword(s):  
Foreland Basin ◽  
Upper Ordovician ◽  
Middle Ordovician ◽  
Lower Silurian ◽  
Basin Development ◽  
Caledonian Orogeny

A complete log-stratigraphical breakdown of the Middle Ordovician to lower Silurian shale-dominated succession is presented for the Bornholm–Skåne–Kattegat area in southernmost Scandinavia. A wireline log zonation developed for the onshore Bornholm Palaeozoic shales is extended to include the offshore Palaeozoic shales in the adjacent Rønne Graben. A complete log zonation scheme for the Cyrtograptus shale (late Llandovery–Wenlock) and the lower part of the Colonus shale (Ludlow) is presented including correlation within the Bornholm–Skåne–Kattegat area. The Cyrtograptus shale in the Bornholm area is estimated to be 400 m thick and marks the shift to a rapidly subsiding foreland basin, heralding the Caledonian Orogeny.

New data on Ordovician–Silurian conodonts and stratigraphy from the Severnaya Zemlya Archipelago, Russian Arctic

2009 ◽  
Vol 146 (4) ◽  
pp. 497-516 ◽  
Author(s):  
P. MÄNNIK ◽  
O. K. BOGOLEPOVA ◽  
A. PÕLDVERE ◽  
A. P. GUBANOV
Keyword(s):  
Shallow Water ◽  
Ural Region ◽  
Russian Arctic ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
The Baltic ◽  
Severnaya Zemlya ◽  
First Time ◽  
Severnaya Zemlya Archipelago ◽  
North Greenland

AbstractThirty samples from 22 sections collected by the SWEDARCTIC international expedition to Severnaya Zemlya in 1999 contained Ordovician and Silurian conodont faunas. Several taxa, including Apsidognathus cf. milleri, Aulacognathus cf. kuehni, Nudibelodina sensitiva, Ozarkodina broenlundi and Pterospathodus eopennatus, allow precise dating of the strata in this region for the first time. The occurrence of Aphelognathus pyramidalis and Rhipidognathus aff. R. symmetricus in samples from the Strojnaya Formation fits well with the earlier dating of these strata as latest Ordovician. However, Aphelognathus sp. in sample BG-99/14-a, collected from the upper Ushakov Formation, indicates that at least in the lower reaches of the Ushakov River the top of this formation is considerably younger than considered earlier: the sampled strata are Late, not Early Ordovician in age. In the Ordovician and Silurian the present-day Severnaya Zemlya region was dominated by extensive shallow-water, mainly semi-restricted basin environments with habitat specific faunas. The occurrence of Riphidognathus aff. R. symmetricus at some levels in the Upper Ordovician suggests extreme shallowing episodes in the basin. On Severnaya Zemlya, ‘normal-marine’ faunas (including Pt. eopennatus) invaded the distal peripheral regions of the wide shallow-water platform at times of maximum sea-level rise only. The occurrence of Oz. broenlundi and N. sensitiva indicates that in the early Silurian the Severnaya Zemlya basin was quite well connected to the basins over modern North Greenland as well as to the Baltic Palaeobasin. The lower Silurian conodont assemblages in the Vodopad to Samojlovich formations are most similar to those described from the eastern Timan–northern Ural region.

scholarly journals Upper Ordovician and Silurian carbonate shelf stratigraphy, facies and evolution, eastern North Greenland

1984 ◽  
Vol 148 ◽  
pp. 1-73
Author(s):  
J.M Hurst
Keyword(s):  
Deep Water ◽  
Carbonate Rocks ◽  
Upper Ordovician ◽  
Carbonate Production ◽  
Lower Silurian ◽  
The North ◽  
Lithostratigraphic Units ◽  
Shallow Subtidal ◽  
North Greenland

A new lithostratigraphic scheme is erected for the uppermost Ordovician and lower Silurian shelf carbonate rocks of Peary Land and Kronprins Christian Land, eastern North Greenland. All carbonate rocks were deposited on a fairly stable shelf which was bordered to the north and east by deep-water basins. The shelf foundered in the latest LIandoverian, terminating carbonate production. Five formations and two members are defined and extend from the uppermost Ordovician (Cincinnatian) to the uppermost LIandoverian, or possibly lowermost Wenlock in the Silurian. Lithostratigraphic units include: Turesø Formation (new) composed of alternating light and dark grey peritidal to shallow subtidal laminated or massive dolomites, cryptalgal laminites and fenestral lime mudstones – uppermost Ordovician (Richmondian, Cincinnatian) to Lower or Middle Llandoverian; Ymers Gletscher Formation (new) composed of light grey peritidal lime mudstones, fenestral lime mudstones and cryptalgal laminites 0150 Lower to Middle Llandoverian; Odins Fjord Formation (new) composed of shallow to deep subtidal dark lime mudstones, wackestones and commonly floatstone and rudstone biostromes – Middle (possibly Lower) to Upper Llandoverian; Melville Land Member (new) composed of light grey peritidal lime mudstones, fenestral lime mudstones and cryptalgal laminites – Middle (possibly Lower) Llandoverian; Bure lskappe Member (new) composed of drowned shelf, dark grey to black laminated lime mudstone with terrigenous mudstone interbeds – Upper Llandoverian; Samuelsen Høj Formation (new) composed of light grey to white reef limestones – uppermost Llandoverian; Harefjeld Formation (new), a faulted, folded and cleaved black lime and terrigenous mudstone unit in eastern Kronprins Christian Land – Ordovician to Silurian (Llandoverian).

scholarly journals Conodonts from the Upper Ordovician – Lower Silurian carbonate platform of North Greenland

1990 ◽  
Vol 159 ◽  
pp. 1-151
Author(s):  
H.A Armstrong
Keyword(s):  
Shallow Water ◽  
Carbonate Platform ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
The North ◽  
Single Genus ◽  
Informal Groups ◽  
North Greenland

Samples from Upper Ordovician and Lower Silurian strata of the North Greenland carbonate platform have yielded approximately 16 500 identifiable conodont elements referable to 25 multi-element genera and 71 species and subspecies. A single genus, Pseudobelodella and 17 species and subspecies are new. In addition, 8 informal groups of indeterminate species of Oulodus are described. The Upper Ordovician conodont species can be referred to 'Fauna 12' of the American Midcontinent Province where the presence of Rhipodognathus symmetrius in the late Richmondian is typical of shallow water deposits. The Ordovician-Silurian boundary is difficult to place in this study using conodonts. New conodont zonations are proposed for Lower Silurian shelf and slope biofacies; two new early Llandovery conodont zones are erected in the slope biofacies, the Aspelundia expansa Biozone (?earliest Rhuddanian to early Aeronian) and the Aspelundia fluegeli Biozone (early Aeronian to early Telychian). The Pterospathodus celloni Biozone is shown to be particularly valuable in the correlation of strata of late Llandovery age throughout North Greenland.

scholarly journals Difference Analysis of Organic Matter Enrichment Mechanisms in Upper Ordovician-Lower Silurian Shale from the Yangtze Region of Southern China and Its Geological Significance in Shale Gas Exploration

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Ming Wen ◽  
Zhenxue Jiang ◽  
Kun Zhang ◽  
Yan Song ◽  
Shu Jiang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Southern China ◽  
Sedimentary Organic Matter ◽  
Gas Content ◽  
Silicon Isotope ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
Excess Silicon ◽  
Lower Yangtze

The upper Ordovician-lower Silurian shale has always been the main target of marine shale gas exploration in southern China. However, the shale gas content varies greatly across different regions. The organic matter content is one of the most important factors in determining gas content; therefore, determining the enrichment mechanisms of organic matter is an important problem that needs to be solved urgently. In this paper, upper Ordovician-lower Silurian shale samples from the X-1 and Y-1 wells that are located in the southern Sichuan area of the upper Yangtze region and the northwestern Jiangxi area of the lower Yangtze region, respectively, are selected for analysis. Based on the core sample description, well logging data analysis, mineral and elemental composition analysis, silicon isotope analysis, and TOC (total organic carbon) content analysis, the upper Ordovician-lower Silurian shale is studied to quantitatively calculate its content of excess silicon. Subsequently, the results of elemental analysis and silicon isotope analysis are used to determine the origin of excess silicon. Finally, we used U/Th to determine the characteristics of the redox environment and the relationship between excess barium and TOC content to judge paleoproductivity and further studied the mechanism underlying sedimentary organic matter enrichment in the study area. The results show that the excess silicon from the upper Ordovician-lower Silurian shale in the upper Yangtze area is derived from biogenesis. The sedimentary water body is divided into an oxygen-rich upper water layer that has higher paleoproductivity and a strongly reducing lower water that is conducive to the preservation of sedimentary organic matter. Thus, for the upper Ordovician-lower Silurian shale in the upper Yangtze region, exploration should be conducted in the center of the blocks with high TOC contents and strongly reducing water body. However, the excess silicon in the upper Ordovician-lower Silurian shale of the lower Yangtze area originates from hydrothermal activity that can enhance the reducibility of the bottom water and carry nutrients from the crust to improve paleoproductivity and enrich sedimentary organic matter. Therefore, for the upper Ordovician-lower Silurian shale in the lower Yangtze region, exploration should be conducted in the blocks near the junction of the two plates where hydrothermal activity was active.

Oxygen isotope (δ18O) trends measured from Ordovician conodont apatite using secondary ion mass spectrometry (SIMS): Implications for paleo-thermometry studies

2021 ◽  
Author(s):  
Cole T. Edwards ◽  
Clive M. Jones ◽  
Page C. Quinton ◽  
David A. Fike
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Matrix Effects ◽  
Analytical Techniques ◽  
Upper Ordovician ◽  
Bulk Analysis ◽  
Middle Ordovician ◽  
Ion Mass Spectrometry ◽  
Oxygen Isotopic ◽  
Secondary Ion

The oxygen isotopic compositions (δ18O) of minimally altered phosphate minerals and fossils, such as conodont elements, are used as a proxy for past ocean temperature. Phosphate is thermally stable under low to moderate burial conditions and is ideal for reconstructing seawater temperatures because the P-O bonds are highly resistant to isotopic exchange during diagenesis. Traditional bulk methods used to measure conodont δ18O include multiple conodont elements, which can reflect different environments and potentially yield an aggregate δ18O value derived from a mixture of different water masses. In situ spot analyses of individual elements using micro-analytical techniques, such as secondary ion mass spectrometry (SIMS), can address these issues. Here we present 108 new δ18O values using SIMS from conodont apatite collected from four Lower to Upper Ordovician stratigraphic successions from North America (Nevada, Oklahoma, and the Cincinnati Arch region of Kentucky and Indiana, USA). The available elements measured had a range of thermal alteration regimes that are categorized based on their conodont alteration index (CAI) as either low (CAI = 1−2) or high (CAI = 3−4). Though individual spot analyses of the same element yield δ18O values that vary by several per mil (‰), most form a normal distribution around a mean value. Isotopic variability of individual spots can be minimized by avoiding surficial heterogeneities like cracks, pits, or near the edge of the element and the precision can be improved with multiple (≥4) spot analyses of the same element. Mean δ18O values from multiple conodonts from the same bed range between 0.0 and 4.3‰ (median 1.0‰), regardless of low or high CAI values. Oxygen isotopic values measured using SIMS in this study reproduce values similar to published trends, namely, δ18O values increase during the Early−Middle Ordovician and plateau by the mid Darriwilian (late Middle Ordovician). Twenty-two of the measured conodonts were from ten sampled beds that had been previously measured using bulk analysis. SIMS-based δ18O values from these samples are more positive by an average of 1.7‰ compared to bulk values, consistent with observations by others who attribute the shift to carbonate- and hydroxyl-related SIMS matrix effects. This offset has implications for paleo-temperature model estimates, which indicate that a 4 °C temperature change corresponds to a 1‰ shift in δ18O (‰). Although this uncertainty precludes precise paleo-temperature reconstructions by SIMS, it is valuable for identifying spatial and stratigraphic trends in temperature that might not have been previously possible with bulk approaches.

scholarly journals Effect of Hydrothermal Activity on Organic Matter Enrichment of Shale: A Case Study of the Upper Ordovician and the Lower Silurian in the Lower Yangtze, South China

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 495 ◽  
Author(s):  
Yizhou Huang ◽  
Zhenxue Jiang ◽  
Kun Zhang ◽  
Yan Song ◽  
Shu Jiang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Oxygen Isotope ◽  
Shale Gas ◽  
Organic Matter Content ◽  
Hydrothermal Activity ◽  
Late Ordovician ◽  
Sedimentary Organic Matter ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
Activity Intensity

The effect of organic matter on hydrocarbon potential, storage space, and gas content of shale is well-known. Additionally, present-day content of sedimentary organic matter in shale is controlled by depositional and preservation processes. Therefore, a study of the enrichment mechanisms of sedimentary organic matter provides a scientific basis for the determination of favorable areas of shale gas. In this study the Upper Ordovician Xinkailing Fm. and the first member of the Lower Silurian Lishuwo Fm. were examined. Stratigraphic sequences were identified through conventional logs and elemental capture spectrum data. Oxygen isotope analysis was applied to recover paleotemperature of seawater in the study area. The excess silicon content was calculated and the origin of the silica was determined by the Fe-Al-Mn ternary plot. The enrichment mechanism of organic matter was analyzed by two aspects: redox conditions and paleoproductivity. As a result, the stratigraphic interval was divided into two 3rd-order sequences. Through oxygen isotope, the paleotemperature of seawater was 62.7–79.2 °C, providing evidence of the development of hydrothermal activity. Analysis of excess siliceous minerals identified two siliceous mineral origins: terrigenous and hydrothermal. It also revealed an upwards decreasing tendency in hydrothermal activity intensity. Strong hydrothermal activity during the Late Ordovician, recognized as TST1, formed a weak-oxidizing to poor-oxygen environment with high paleoproductivity, which promoted organic matter enrichment. During the Late Ordovician to the Early Silurian, identified as RST1, TST2, and RST2, weakening hydrothermal activity caused the decline of paleoproductivity and increased oxidation of bottom waters, leading to a relative decrease of organic matter content in the shale. Therefore, favorable areas of shale gas accumulation in the Upper Ordovician and Lower Silurian are determined stratigraphically as the TST1, with a high total organic carbonate content. Geographically, the hydrothermally-active area near the plate connection of the Yangtze and the Cathaysian is most favorable.

scholarly journals The Wandel Valley Formation (Early - Middle Ordovician) of North Greenland and its correlatives

1988 ◽  
Vol 137 ◽  
pp. 61-92
Author(s):  
J.S Peel ◽  
M.P Smith
Keyword(s):  
Canadian Arctic ◽  
East Greenland ◽  
Middle Ordovician ◽  
Early Ordovician ◽  
Lowermost Part ◽  
North Greenland

Members are formally described within the Wandel Valley Formation (Early - Middle Ordovician) of the Ryder Gletscher Group in central and eastem North Greenland. In Peary Land the names Pyramideplateau Member (the combined lower and middle informal members of previous usage) and Vestervig Elv Member (the upper member) are proposed. In Kronprins Christian Land, the Alexandrine Bjerge Member (new) overlies the previously named Danmarks Fjord and Amdrup Members. Conodont studies, supported by the macrofauna, indicate that the Pyramideplateau, Danmarks Fjord and Amdrup Members are of late Canadian (Early Ordovician) age. The Canadian-Whiterockian boundary lies within the lowermost part of the Vestervig Elv and Alexandrine Bjerge Members. The top of the former is of earliest Late Whiterockian age while the Alexandrine Bjerge Member only extends into the late Middle Whiterockian. The members of the Wandel Valley Formation are correlated with coeval successions in western North Greenland, East Greenland, the Canadian Arctic Islands and Svalbard.

Sign in / Sign up

Export Citation Format

Share Document