Paleomagnetic and geochemical evidence for a pre-Triassic age for the Lower Amaranth Member of the Williston Basin of Manitoba (Canada)

Paleomagnetic and geochemical data obtained from six wells in southwestern Manitoba indicate that the Lower Amaranth redbeds were deposited earlier than Jurassic or Triassic, the most commonly cited depositional ages for this formation in the Williston Basin. The magnetization is carried primarily by detrital specular and pigmentary hematite and occasionally magnetite. Inclination-only analysis of paleomagnetic data (83 specimens from 60 plugs) indicates two possible depositional magnetization ages: Devonian–Pennsylvanian (D, found in very few samples) or Carboniferous to Permian, as suggested by the inclination and the polarity of the most predominant magnetization (B). An isolated magnetization (C) could be a mid-Jurassic to Neogene localized fluid flow remagnetization event. The oxygen and carbon isotope values of dolomite (–6.45‰ to 0.30‰ Vienna PeeDee Belemnite (VPDB) δ18O, –1.57‰ to 5.44‰ VPDB δ13C; n = 18) indicate that dolomitization could have occurred anytime between Carboniferous and Jurassic. However, the distribution of these values is a function of the three types of dolomite present in the Lower Amaranth strata: detrital, cement, and matrix replacive and reflects both the primary values and diagenetic overprints. Detrital and cement dolomite show depleted values in both oxygen and carbon isotopes, most likely inherited from the original values of the detrital dolomite, with superimposed effects of recrystallization. The matrix replacive dolomite has no detrital content, and its oxygen isotope values are similar to the expected values for primary or early diagenetic dolomite from Carboniferous to Jurassic times. Mixtures of detrital and replacive matrix dolomite give intermediate oxygen and carbon isotope values.

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Characterization and significance of dedolomite in Wadi Nisah, central Saudi Arabia

GeoArabia ◽

10.2113/geoarabia120315 ◽

2007 ◽

Vol 12 (3) ◽

pp. 15-30 ◽

Cited By ~ 2

Author(s):

Dave L. Cantrell ◽

Abdullah Al-Khammash ◽

Peter D. Jenden

Keyword(s):

Saudi Arabia ◽

Isotopic Composition ◽

Oxygen Isotope ◽

Carbon Isotope ◽

Carbon Isotopes ◽

Reservoir Quality ◽

Meteoric Diagenesis ◽

Different Types ◽

Lower Oxygen ◽

Lower Carbon

ABSTRACT Two different types of calcified dolomite, or dedolomite, occur as stratiform and non-stratiform bodies within the Jurassic (Kimmeridgian) upper Jubaila Formation in the Wadi Nisah area of central Saudi Arabia. In the stratigraphically-equivalent subsurface Arab-D reservoir in eastern Saudi Arabia, two types of dolomite, stratiform and non-stratiform, occur which appear to be similar in architecture to the dedolomites examined in this study. However, Wadi Nisah dedolomites exhibit systematic changes in texture and isotopic composition from their precursor dolomites. Non-stratiform dedolomite contains lower oxygen isotope (average δ18O = -10.99‰) and much lower carbon isotope (average δ13C = -7.51‰) values and is much more coarsely crystalline than typical subsurface Arab-D non-stratiform dolomite; in contrast, Wadi Nisah stratiform dedolomite contains similar oxygen isotope values (δ18O = -2.89‰) and only slightly lower carbon isotopes (δ13C = 0.98‰) relative to subsurface Arab-D stratiform dolomites. We suggest that non-stratiform dolomite was more susceptible to late meteoric diagenesis than the horizontally bedded stratiform dolomite intervals. Such differences in character highlight the importance of structural and diagenetic architecture in determining later, post-dolomitization diagenesis and ultimately final reservoir quality.

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A database of Holocene nearshore marine mollusc shell geochemistry from the Northeast Pacific

10.5194/essd-2021-301 ◽

2021 ◽

Author(s):

Hannah M. Palmer ◽

Veronica Padilla Vriesman ◽

Roxanne M. W. Banker ◽

Jessica R. Bean

Keyword(s):

Carbon Isotope ◽

Heat Waves ◽

Indigenous Communities ◽

Geochemical Data ◽

Shell Middens ◽

Data Set ◽

Oxygen And Carbon Isotope ◽

Northeast Pacific ◽

Isotope Data ◽

Δ13c And Δ18o

Abstract. The shells of marine invertebrates can serve as high-resolution records of oceanographic and atmospheric change through time. In particular, oxygen and carbon isotope analyses of nearshore marine calcifiers that grow by accretion over their lifespans provide seasonal records of environmental and oceanographic conditions. Archaeological shell middens generated by Indigenous communities along the Northeast Pacific coast contain shells harvested over multiple seasons for millennia. These shell middens, as well as analyses of archival and modern shells, have the potential to provide multi-site, seasonal archives of nearshore conditions throughout the Holocene. A significant volume of oxygen and carbon isotope data from archaeological shells exists, yet is separately published in archaeological, geochemical, and paleoceanographic journals and has not been comprehensively analyzed to examine oceanographic change over time. Here, we compiled a database of previously published oxygen and carbon isotope data from archaeological, archival, and modern marine molluscs from the North American coast of the Northeast Pacific (32° N to 50° N). This database includes oxygen and carbon isotope data from over 550 modern, archaeological, and sub-fossil shells from 8880 years before present (BP) to the present, from which there are 4,845 total δ13C and 5,071 total δ18O measurements. Shell dating and sampling strategies vary among studies (1–118 samples per shell) and vary significantly by journal discipline. Data are from various bivalves and gastropod species, with Mytilus spp. being the most commonly analyzed taxon. This novel database can be used to investigate changes in nearshore sea surface conditions including warm-cool oscillations, heat waves, and upwelling intensity, and provides nearshore calcite δ13C and δ18O values that can be compared to the vast collections of offshore foraminifera calcite δ13C and δ18O data from marine sediment cores. By utilizing previously published geochemical data from midden and museum shells rather than sampling new specimens, future scientific research can reduce or omit the alteration or destruction of culturally valued specimens and sites. The data set is publicly available through PANGAEA at https://doi.org/10.1594/PANGAEA.932671 (Palmer et al., 2021).

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Fluid Flow and Diffusion in the Waterville Limestone, South--Central Maine: Constraints from Strontium, Oxygen and Carbon Isotope Profiles

Journal of Petrology ◽

10.1093/petroj/38.11.1489 ◽

1997 ◽

Vol 38 (11) ◽

pp. 1489-1512 ◽

Cited By ~ 24

Author(s):

M. J. Bickle ◽

H. J. Chapman ◽

J. M. Ferry ◽

D. Rumble ◽

A. E. Fallick

Keyword(s):

Fluid Flow ◽

Carbon Isotope ◽

Oxygen And Carbon Isotope ◽

South Central ◽

And Diffusion

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Dolomite and dedolomitization in Danian bryozoan limestone from Fakse, Denmark

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-1988-37-06 ◽

1988 ◽

Vol 37 ◽

pp. 63-74

Author(s):

N O Jørgensen

Keyword(s):

Elemental Composition ◽

Carbon Isotope ◽

Carbon Isotopes ◽

Carbonate Rock ◽

Meteoric Water ◽

Genetic Origin ◽

Oxygen And Carbon Isotope ◽

Dolomite Formation ◽

Rock Complex ◽

Host Sediment

The bryozoan limestones in the middle Danian (Lower Paleocene) carbonate rock complex of Fakse Quarry, Denmark, includes small intraformational bodies of dolomite that occur in three different ways: 1) completely dolomitized bryozoan limestones; 2) partially dolomitized bryozoan limestones in which the larger skeletons have resisted total dolomitization, and 3) concretionary dolomite. Furthermore, scattered secondary rhombohedral porosity is observed in bryozoan limestones indicating former occurrences of dolomite. The dolomites are calcian with an elemental composition of approximately (Ca.55, Mg_45)Co3• The Sr content averages 500 ppm Sr, whereas the Mn and Fe contents are relatively low, c. 200 ppm Mn and 2000-4000 ppm total Fe respectively. The oxygen and carbon isotope values (-2.3%. to -3.9%. 1'>180; + 1.9%. to +4.6%. 1'>13C) are close to the field of early diagenetic dolomite replacing marine limestones. The carbon isotopes are enriched by approximately 2%. in comparison to the host sediment, which suggests that dolomitization most likely took place in a zone of methanogenesis. Crystal chemistry and geochemistry indicate a common genetic origin for these dolomites. The dolomite formation was probably an early diagenetic event in which the sequence from occurrences of individual dolomite rhombohedra, concretionary dolomite and partially dolomitized bryozoan limestones, to completely dolomitized bryozoan limestones is interpreted to represent progressive dolomitization. Dedolomitization is most pronounced in the dolomite concretions and to lesser extent in the dolomitized bryozoan limestone beds. The isotopes of the replacive calcite suggests that dedolomitization took place under the influence of meteoric water. The progressive dedolomitization appears to be governed by the access of meteoric water along cleavage traces spreading to the entire dolomite crystals. Therefore, cleavage traces probably control dedolomitization under suitable physicochemical conditions.

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Stable isotope geochemistry of the modern Shinfa River, northwestern Ethiopian lowlands: a potential model for interpreting ancient environments of the Middle Stone Age

Geological Society London Special Publications ◽

10.1144/sp507-2020-219 ◽

2021 ◽

pp. SP507-2020-219

Author(s):

Neil J. Tabor ◽

A. Hope Jahren ◽

Lani Wyman ◽

Mulugeta Feseha ◽

Lawrence Todd ◽

...

Keyword(s):

Oxygen Isotope ◽

River Water ◽

Carbon Isotope ◽

Middle Stone Age ◽

Dry Season ◽

Wet Season ◽

Oxygen Isotope Fractionation ◽

Oxygen And Carbon Isotope ◽

Calcareous Deposits ◽

Stable Oxygen

AbstractSeveral years of weekly sampling of waters from the Shinfa River watershed in the lowlands of northwestern Ethiopia yielded 275 samples with δDvsmow and δ18Ovsmow values ranging from c. −10 to +100‰ and from c. −2 to +20‰, respectively. Wet season (summertime) Shinfa River water stable hydrogen and oxygen isotope values are among the lowest reported in this study, whereas the dry season (winter/spring) usually records a progressive trend towards +100 and +20‰, respectively. Overlapping with this interval of Shinfa River water sampling, air temperatures (n = 155) also were recorded at the same time; temperatures range from c. 18 to 47°C. The coolest temperatures occur during the summer wet season, associated with the arrival of the Kiremt rains in the region, whereas the warmest temperatures occur towards the end of the dry season. In order to evaluate the extent to which this rather extreme isotope hydrology is recorded in the sediments and biota of the Shinfa River system, both hardwater calcareous deposits precipitated on basalt cobbles by evaporation in the Shinfa River channel during the dry season and aragonite from three different modern bivalve mollusc species were collected and analysed for their stable oxygen and carbon isotope compositions. Hardwater calcareous deposit δ18Ovpdb and δ13Cvpdb values range from c. −2 to +5‰ and c. −9 to +7‰, respectively, and preserve a trend towards progressively more positive δ18Ovpdb and δ13Cvpdb values through the course of the dry season. Shinfa River mollusc aragonite powders (n = 51) were serially sampled from cf. Coelutura aegyptica, cf. Chambardia rubens and Etheria elliptica species. All species record oxygen and carbon isotopes between c. −2 and +7‰ and between c. −18 and −8‰, and each species records coherent trends between those extremes as well as a positive parametric correlation between measured oxygen and carbon isotope values. However, there does appear to be some variability of measured isotope values by species, suggesting that species-specific metabolic differences may impact the resulting range of aragonite stable carbon and oxygen values. Based upon the measured Shinfa River water δ18Ovsmow and corresponding water temperatures at the time of sampling, a possible range of Shinfa River calcite and aragonite δ18Ovpdb values were calculated in conjunction with well-established calcite–water and aragonite–water oxygen isotope fractionation equations. These ‘fictive’ calcite and aragonite δ18Ovpdb values range from c. −5 to +15‰, which is a much larger range than previously documented from analyses of the hardwater calcareous deposits and mollusc aragonite samples. The narrower range of values in the natural calcite and aragonite samples may be attributed to several mechanisms, including time averaging and environmental stress. Nevertheless, the stable oxygen isotopic compositions of these natural samples offer a minimum assessment of the environmental extremes which occur in this region today, and provide a model for reconstructing the environments of the past.

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