Rhynchonellid brachiopods from the upper ordovician-lower silurian Beaverfoot and Nonda formations of the Rocky Mountains, British Columbia

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.

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Ediacaran fossils and dubiofossils, Miette Group of Mount Fitzwilliam area, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e91-138 ◽

1991 ◽

Vol 28 (10) ◽

pp. 1541-1552 ◽

Cited By ~ 14

Author(s):

H. J. Hofmann ◽

E. W. Mountjoy ◽

M. W. Teitz

Keyword(s):

British Columbia ◽

Shallow Water ◽

Rocky Mountains ◽

Carbonate Mounds ◽

Windermere Supergroup

Shallow-water clastic beds flanking stromatolitic carbonate mounds in the upper part of the Vendian Miette Group (Windermere Supergroup) of the Rocky Mountains contain a poorly preserved, soft-bodied fauna that comprises morphologically very variable discoid remains; these include the taxa Beltanella sp., cf. B. grandis, Charniodiscus? sp., Irridinitus? sp., Nimbia occlusa, Protodipleurosoma sp., cf. P. rugulosum, and Zolotytsia? sp. and seven types of dubiofossils.

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Comparative Analysis of the Siliceous Source and Organic Matter Enrichment Mechanism of the Upper Ordovician–Lower Silurian Shale in the Upper-Lower Yangtze Area

Minerals ◽

10.3390/min8070283 ◽

2018 ◽

Vol 8 (7) ◽

pp. 283 ◽

Cited By ~ 8

Author(s):

Kun Zhang ◽

Zhuo Li ◽

Shu Jiang ◽

Zhenxue Jiang ◽

Ming Wen ◽

...

Keyword(s):

Organic Matter ◽

Comparative Analysis ◽

Upper Ordovician ◽

Lower Silurian ◽

Lower Yangtze ◽

Yangtze Area

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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 ◽

10.3390/min8110495 ◽

2018 ◽

Vol 8 (11) ◽

pp. 495 ◽

Cited By ~ 2

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.

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New Lower Jurassic ammonite faunas from the Fernie Formation, southern Canadian Rocky Mountains

Canadian Journal of Earth Sciences ◽

10.1139/e87-162 ◽

1987 ◽

Vol 24 (8) ◽

pp. 1688-1704 ◽

Cited By ~ 9

Author(s):

Russell L. Hall

Keyword(s):

British Columbia ◽

North American ◽

Rocky Mountains ◽

Red Deer ◽

First Record ◽

Lower Jurassic ◽

Canadian Rocky Mountains ◽

Poker Chip

New ammonite faunas are described from sections along Bighorn and Scalp creeks in central-western Alberta where Lower Jurassic parts of the Fernie Formation are exposed. The first record of the upper Sinemurian Obtusum Zone from the Fernie is based on the occurrence of Asteroceras cf. stellare and Epophioceras cf. breoni in the basal pebbly coquina on Bighorn Creek. The overlying Red Deer Member has yielded Amaltheus cf. stokesi, representing the upper Pliensbachian Margaritatus Zone; in immediately superjacent strata the first North American examples of ?Amauroceras occur together with Protogrammoceras and ?Aveyroniceras. In the basal parts of the overlying Poker Chip Shale a fauna including Harpoceras cf. falciferum, Harpoceratoides, Polyplectus cf. subplanatus, Hildaites cf. serpentiniformis, and Dactylioceras cf. athleticum is correlated with the lower Toarcian Falciferum Zone.The upper parts of the Poker Chip Shale on Fording River in southeastern British Columbia contain a fauna representing some part of the upper Toarcian, but owing to poor preservation, generic identifications are only tentatively made.

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