Regional hydrogeochemistry of the carbonate rock aquifer, southern Manitoba

2002 ◽  
Vol 39 (7) ◽  
pp. 1053-1063 ◽  
Author(s):  
Stephen E Grasby ◽  
Robert N Betcher
Keyword(s):  
Carbonate Rock ◽  
Geochemical Data ◽  
Williston Basin ◽  
Aquifer System ◽  
Middle Ordovician ◽  
Saline Waters ◽  
Salt Dissolution ◽  
Melt Water ◽  
Major River ◽  
Eastern Edge

Middle Ordovician to Middle Devonian carbonates in the Manitoba lowlands form an extensive aquifer system along the eastern edge of the Williston Basin. The aquifer is divided into fresh and saline portions by a series of topographic lows defined by major river systems and lakes that create a north–south-trending hydraulic divide. East of this divide Ca–Mg–HCO3 fresh waters are derived by active modern-day recharge focused in the Sandilands and Interlake regions. Stable isotope and geochemical data indicate that Na–Cl saline waters west of the divide are a mixture of original basin brines and glacial melt water pushed into the basin during Pleistocene glaciation. High Na/Cl and Cl/Br ratios are consistent with significant salt dissolution by glacial melt water.

The stratigraphy of the Lower Ordovician St. George Group, western Newfoundland: the interaction between eustasy and tectonics

1987 ◽  
Vol 24 (10) ◽  
pp. 1927-1951 ◽  
Author(s):  
Ian Knight ◽  
Noel P. James
Keyword(s):  
Sea Level ◽  
Continental Margin ◽  
Carbonate Rock ◽  
Outer Edge ◽  
Low Latitude ◽  
Middle Ordovician ◽  
Lower Ordovician ◽  
Shallow Subtidal ◽  
Eustatic Fluctuations ◽  
Equal Thickness

The St. George Group is a ~500 m thick sequence of carbonate rock that accumulated during Early and early Middle Ordovician time in a series of shallow subtidal and peritidal environments near the outer edge of a low-latitude continental margin. Lithological variations, in the form of two megacycles, reflect deposition in response to eustatic fluctuations in sea level preceding and during the early stages of Taconic orogenesis.Strata are grouped into four formations of roughly equal thickness. The newly named basal Watts Bight Formation is a lower sequence of peritidal limestones and dolostones and an upper thicker, commonly dolomitized succession of burrowed carbonates distinguished by large digitate thrombolite mounds. The overlying Boat Harbour Formation (new) is a series of muddy, peritidal, shallowing-upward sequences of limestone and dolostone. A widespread subaerial disconformity near the top of the formation, reflecting eustaic sea-level fall and the end of the first megacycle, is marked by breccia, quartz-pebble conglomerate, paleokarst, and (or) extensive dolomitization and is succeeded by higher energy peritidal limestones called the Barbace Cove Member (new). The succeeding, thick, monotonous Catoche Formation (revised) is a succession of fossiliferous subtidal limestones with scattered thrombolite mounds whose upper part is locally affected by extensive, multigeneration dolomitization and Pb–Zn mineralization. The St. George Group is capped by the newly defined Aguathuna Formation, a stack of peritidal dolostones and minor limestones and shales deposited during a period of repeated exposure and synsedimentary faulting. An erosional disconformity, resulting from regional compressional tectonics and eustatic sea-level fall, locally marks the top of the St. George and the second megacycle.

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

2009 ◽  
Vol 46 (11) ◽  
pp. 855-873 ◽  
Author(s):  
Erika Szabó ◽  
Maria T. Cioppa ◽  
Ihsan S. Al-Aasm
Keyword(s):  
Fluid Flow ◽  
Oxygen Isotope ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Geochemical Data ◽  
Williston Basin ◽  
Oxygen And Carbon Isotopes ◽  
Oxygen And Carbon Isotope ◽  
The Matrix ◽  
Expected Values

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.

Secondary dolomitization as a factor determining the reservoir properties of the Lower Devonian deposits in Eastern edge of the Khoreyver depression (Timan-Pechora basin)

2020 ◽  
pp. 47-56
Author(s):  
V. A. Zhemchugova ◽  
E. E. Maslova
Keyword(s):  
Exposure Time ◽  
Carbonate Rock ◽  
Lower Devonian ◽  
Pore Space ◽  
Key Factors ◽  
Reservoir Properties ◽  
Pechora Basin ◽  
Eastern Edge

The Lower Devonian deposits were characterized in terms of their composition, texture and secondary transformations, the distribution of various types of pore space was analyzed and several types of dolomite textures were identified. The analysis showed that permeability, solubility and primary texture of carbonate rock or sediment, as well as temperature, volume and exposure time of dolomitizing fluids are key factors for dolomitization and depending on these factors dolomitization can lead to not only increase but also decrease of porosity.

Sign in / Sign up

Export Citation Format

Share Document