scholarly journals In situ geochemistry of middle Ordovician dolomites of the upper Mississippi valley

2018 ◽  
Vol 5 (1) ◽  
pp. 4-22
Author(s):  
John Michael Callen ◽  
Achim D. Herrmann
Keyword(s):  
Mississippi Valley ◽  
Middle Ordovician

Middle Ordovician (Chazy Group) cavity-dwelling boring sponges

1981 ◽  
Vol 18 (6) ◽  
pp. 1101-1108 ◽  
Author(s):  
David R. Kobluk
Keyword(s):  
Cavity Wall ◽  
Hard Substrate ◽  
Middle Ordovician ◽  
Siliceous Spicules ◽  
Boring Sponges

Microcavities in lower Middle Ordovician bryozoan mounds from the Laval Formation (Chazy Group) near Montreal, Quebec contain evidence that endolithic (boring) sponges were present. Ramose borings with scalloped walls and swellings resembling endolithic sponge galleries, faceted carbonate grains similar to modern sponge chips, and siliceous spicules both in situ on the cavity wall or roof and in the sediment, all point to the activities of endolithic sponges in the hard substrate of the wall and roof.Coelobiontic (cavity-dwelling) endolithic sponges therefore infested cavities in skeletal mounds and reefs in the Middle Ordovician and appear to have exploited the cavity habitat very soon after the appearance of metazoan skeletal reefs in the Ordovician.

The proposed Cambrian–Ordovician global Boundary stratotype and point (GSSP) in Western Newfoundland, Canada

1988 ◽  
Vol 125 (4) ◽  
pp. 381-414 ◽  
Author(s):  
C. R. Barnes
Keyword(s):  
New Species ◽  
Shallow Water ◽  
Head Group ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
Green Point ◽  
Group A ◽  
Conodont Fauna ◽  
Three New Species

AbstractSections exposing the Cambrian–Ordovician Boundary interval at Broom Point in western Newfoundland have been proposed earlier for a global systemic boundary stratotype. These lie within the Cow Head Group, a late Middle Cambrian to early Middle Ordovician allochthonous unit of limestone, shale, and conglomerate deposited at the toe of the ancient continental slope and on the adjacent continental rise. Several recent studies have further investigated the stratigraphy, sedimentology, and palaeontology of the Cow Head Group and others are under way on magnetostratigraphy and chemostratigraphy. These aspects are reviewed for six key boundary sections representing proximal to distal facies: Cow Head Ledge, Broom Point South, Broom Point North, St Pauls Inlet Quarry, Martin Point, and Green Point. In particular, new data are presented from 260 conodont samples that yielded 15500 conodonts. This intense sampling has allowed the discrimination of minor hiatuses in the proximal to intermediate facies where conglomerates have eroded and cannibalized underlying strata. New conodont data from Broom Point North have lowered the base of the C. lindstromi Zone into unit 74 conglomerates, thereby making this section unsuitable as a boundary stratotype. New collections from Green Point have yielded abundant conodonts and over 9400 conodonts have been recovered from 77 samples.The conodont, graptolite, and trilobite biostratigraphy through the boundary interval is documented allowing accurate correlation between sections and more precisely revealing small hiatuses in the proximal and intermediate facies. The sequence of conodont zones is: Eoconodontus notchpeakensis, Cordylodus proavus, C. caboti, C. intermedius, C. lindstromi and C. angulatus. These can be correlated with trilobite zones established from both in situ and clast faunas from the proximal to intermediate facies and with graptolite assemblages (of Cooper 1979) especially in the intermediate to distal facies. Three new species of Cordylodus are described (C. andresi, C. hastatus and C. tortus) and the full apparatus of Iapetognathus preaengensis is illustrated.The criteria for selecting a global boundary stratotype and point (GSSP) are reviewed in terms of the Cow Head sections. The Green Point section is shown to meet, and largely surpass, the prerequisites required of a stratotype. The Green Point section is proposed to be the global boundary stratotype with the base of the Ordovician System defined at the base of unit 23, which is the base of the Broom Point Member, Green Point Formation, at a level coincident with the base of the Cordylodus lindstromi Zone. In addition to an abundant and superbly preserved conodont fauna, this section preserves the best sequence of earliest planktic graptolites through a 40 m interval; the first nematophorous graptolites (of Assemblage 1) occur in unit 25, 6.9 m above the base of the C. lindstromi Zone. This level can be readily correlated into the proximal facies where both deep and shallow water trilobites (in situ and in clasts, respectively) show the base of the C. lindstromi Zone to lie within the Symphysurina brevispicata trilobite Subzone.

Chemical correlation of K-bentonite beds in the Middle Ordovician Decorah Subgroup, upper Mississippi Valley

Geology ◽  
1987 ◽  
Vol 15 (3) ◽  
pp. 208 ◽  
Author(s):  
Dennis R. Kolata ◽  
Joyce K. Frost ◽  
Warren D. Huff
Keyword(s):  
Mississippi Valley ◽  
Middle Ordovician ◽  
Chemical Correlation

scholarly journals In situ geochemical characterization of pyrite crystals in burial dolomites of St. George Group carbonates

2018 ◽  
Vol 55 (5) ◽  
pp. 536-544 ◽  
Author(s):  
Babatunde John Olanipekun ◽  
Karem Azmy
Keyword(s):  
Sulfate Reduction ◽  
Fluid Inclusions ◽  
Secondary Ion Mass Spectrometry ◽  
Main Stage ◽  
Mississippi Valley ◽  
Sulfide Mineralization ◽  
Two Phase ◽  
Saddle Dolomite ◽  
Phase Fluid

Secondary ion mass spectrometry (SIMS) was used to measure the δ34S of pyrite disseminated in burial dolomite matrix of Boat Harbour formation at Main Brook and Daniel’s Harbour (about 130 km apart). At Main Brook, δ34S values for the pyrite grains show wide variation (–15 to +20‰ (n = 20)), but are mostly negative. Combined with a paucity of two-phase fluid inclusions in the host burial dolomite, the depleted δ34S values suggest that the pyrite is a direct product of bacterial sulfate reduction (BSR). Predominantly negative δ34S values were also obtained for sampled pyrite at Daniel’s Harbour and Port au Choix; however, relatively high homogenization temperatures (>100 °C) of two-phase fluid inclusions in the host dolomite is incompatible with a BSR process for pyrite formation. More so, Daniel’s Harbour is a site for main stage sulfide mineralization (Mississippi Valley-type (MVT) system), hosted in similarly burial dolomite and that has been previously constrained to be associated with thermochemical sulfate reduction (TSR). A relative proximity of the currently studied pyrite samples to this MVT system deposit is thus inconsistent with an in-situ BSR for these pyrites. The analyzed pyrite grains are commonly encased in bitumen, and they postdate their host burial dolomite and predate deep burial saddle dolomite. Taken together, the depleted δ34S signature in the pyrite was likely inherited from migrated hydrocarbons in the reservoir. Incursion of an initial pulse of hot sulfate-rich brine into the formation can cause thermal cracking of hydrocarbons, thereby releasing its low δ34S. Thus the inherited low δ34S signature was likely a product of an earlier BSR that occurred in the kerogen or source organic materials in source rock. Subsequently, the main stage sulfide mineralization (MVT deposit) occurred via in-situ TSR. These findings have an implication for the paragenetic history of sulfide minerals precipitated during MVT mineralization episode.

Crinoids of the Champlainian (Middle Ordovician) Guttenberg Formation—upper Mississippi Valley region

1986 ◽  
Vol 60 (3) ◽  
pp. 711-718 ◽  
Author(s):  
Dennis R. Kolata
Keyword(s):  
Mississippi Valley ◽  
Middle Ordovician

A well-preserved and locally abundant crinoid fauna has been discovered in the lower part of the Champlainian (Middle Ordovician) Glenhaven Member of the Guttenberg Formation in the Upper Mississippi Valley region. The material consists of the dicyclic inadunates Cupulocrinus levorsoni n. sp., C. jewetti (E. Billings) and monocyclic camerate Pycnocrinus gerki n. sp.

Genèse du gaz naturel de la région de Trois-Rivières, basses terres du Saint-Laurent, et de Saint-Flavien, Appalaches, Québec, Canada

1993 ◽  
Vol 30 (9) ◽  
pp. 1881-1885 ◽  
Author(s):  
P. St-Antoine ◽  
Y. Héroux
Keyword(s):  
Organic Matter ◽  
Natural Gas ◽  
Molecular Composition ◽  
Middle Ordovician ◽  
Thermal Peak ◽  
Isotopic Analyses

Isotopic analyses of 13C and 2H concentrations in methane and determinations of the total gas molecular composition were completed on five samples collected in the Pleistocene sediments of the Trois Rivières area, St-Lawrence Lowlands, and of the Saint-Flavien area, in the Appalachians, where accumulations of natural gas occur. The results indicate that (i) the gas at Yamachiche is biogenic and formed in situ within the Pleistocene deposits, (ii) the gas at Saint-Flavien is thermogenic, and (iii) the gas at Pointe-du-Lac and at the Vieilles-Forges is likely a mixture of both. The petrogenic study of the organic matter of the Beekmantown Group, Middle Ordovician age, suggests that the gas at Saint-Flavien migrated into the present reservoir after the thermal peak. [Journal Translation]

Paleomagnetism of the Mississippi Valley-type ores and host rocks in the northern Arkansas and Tri-State districts

1990 ◽  
Vol 27 (7) ◽  
pp. 923-931 ◽  
Author(s):  
H. Pan ◽  
D. T. A. Symons ◽  
D. F. Sangster
Keyword(s):  
Mississippi Valley ◽  
Middle Ordovician ◽  
Paleomagnetic Study ◽  
Lead Zinc ◽  
Almost All ◽  
Host Rocks ◽  
State Area ◽  
Mississippi Valley Type ◽  
Ore District ◽  
Valley Type

A paleomagnetic study has been done on 452 specimens from the Early Ordovician Cotter and Middle Ordovician Everton formations in the northern Arkansas Mississippi Valley-type (MVT) lead–zinc ore district and from the Mississippian Warsaw and Keokuk formations in the Tri-State MVT district. Progressive alternating-field and thermal demagnetization first removed a steep normal modern viscous remanence component, leaving an underlying stable remanence of very low intensity (0.3 × 10−5 – 3 × 10−5 A/m). In the Tri-State area, further demagnetization of unaltered host rocks at seven sites in the Warsaw Formation yields a B component with a mean direction of declination (D) 146°, inclination (I) 14 °(A95 = 13°), corresponding to a paleopole of 130°E, 31°N (Dp = 7°, Dm = 14°), which is a primary Mississippian remanence. In northern Arkansas further demagnetization reveals an A component at 9 sites with a mean direction of D 156°, I 30° (A95 = 7°) and a C component at 14 sites of D 160°, I 1 °(A95 = 9°), corresponding to pole positions of 116°E, 33°N (Dp = 4°, Dm = 8°) and 119°E, 49°N (Dp = 4°, Dm = 9°), respectively. Almost all of the A-component sites are from unmineralized dolomite, whereas all of the C-component sites are from mineralized locations. This correlation suggests that the A magnetization is related to Late Devonian secondary dolomitization and the C magnetization to Permian mineralization produced by brines migrating from the Arkom basin upon deformation and uplift during the Ouachita orogeny.

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