Pub Date : 2021-01-24DOI: 10.4138/ATLGEOL.2021.002
Ronald Blakey
Paleogeographic maps represent the ultimate synthesis of complex and extensive geologic data and express pictorially the hypothetical landscape of some region during a given time-slice of deep geologic time. Such maps, presented as paired paleogeographic and paleotectonic reconstructions, have been developed to portray the geologic history of the greater Arctic region over the past 400 million years. Collectively they depict four major episodes in the development of the Arctic region. The first episode witnessed early and middle Paleozoic terrane assembly and accretion during the Caledonian and Ellesmerian orogenies, which brought together many pieces of the Arctic collage along the northern margin of Laurussia. During the second phase, the assembly of Pangea in the late Paleozoic joined Siberia to Laurussia, an entity that became Laurasia during the subsequent break-up of Pangea. Then, Mesozoic subduction and terrane accretion constructed the Cordilleran margin and opened the Canada Basin. Finally, Cenozoic North Atlantic sea-floor spreading fully opened the Arctic Ocean.
{"title":"Paleotectonic and paleogeographic history of the Arctic region","authors":"Ronald Blakey","doi":"10.4138/ATLGEOL.2021.002","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2021.002","url":null,"abstract":"Paleogeographic maps represent the ultimate synthesis of complex and extensive geologic data and express pictorially the hypothetical landscape of some region during a given time-slice of deep geologic time. Such maps, presented as paired paleogeographic and paleotectonic reconstructions, have been developed to portray the geologic history of the greater Arctic region over the past 400 million years. Collectively they depict four major episodes in the development of the Arctic region. The first episode witnessed early and middle Paleozoic terrane assembly and accretion during the Caledonian and Ellesmerian orogenies, which brought together many pieces of the Arctic collage along the northern margin of Laurussia. During the second phase, the assembly of Pangea in the late Paleozoic joined Siberia to Laurussia, an entity that became Laurasia during the subsequent break-up of Pangea. Then, Mesozoic subduction and terrane accretion constructed the Cordilleran margin and opened the Canada Basin. Finally, Cenozoic North Atlantic sea-floor spreading fully opened the Arctic Ocean.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42182755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-24DOI: 10.4138/ATLGEOL.2021.004
Gunn Mangerud, N. Paterson, J. Bujak
Permian palynofloras are recorded around the present-day Arctic and are typically dominated by taeniate and non-taeniate pollen, with intervals of spore domination. The assemblages show close similarities around the Arctic. Based on the published record, we present a compilation of 23 last occurrences (LOs), first occurrences (FOs), and some abundance events. These are anticipated to have regional correlation potential. In general, the Permian palynofloras of the Arctic have not been extensively studied, and the resolution is low due to a general lack of independent age control. doi:10.4138/atlgeol.2021.004 ATLANTIC GEOLOGY 57, 57–69 (2021) 0843-5561|21|0057–0069$2.95|0 (see for example Utting and Piasecki 1995). Utting (1989, p. 234) did not use the Kungurian stage. Utting (1994, p. 9) correlated the Roadian to the “Ufimian (?)” and the Wordian to the “Kazanian (?)” (Fig. 1). See Lucas and Shen (2016) for further discussion on Permian chronostratigraphy. Palynomorphs are the most common, and often the only, fossil group recorded from the Permian, particularly the upper Permian. Palynology is therefore a critical tool for dating and refining stratigraphic correlations of Permian rocks (Stephenson 2016). However, different taxonomic approaches and stratigraphic methods have made comparisons difficult between regions. Especially problematic in the Arctic is the limited communication between Russian and western palynologists; the development especially of a shared taxonomy would likely lead to greatly improved correlations. Permian palynomorphs are primarily pollen and spores (miospores), although acritarchs, algae and foraminiferal linings also occur. For the Cisuralian, fusulinids and conodonts provide independent age determinations for some of the published palynostratigraphic zones. None of the Permian INTRODUCTION This article is a contribution to the Circum-Arctic Palynological Events (CAPE) project, providing a scheme of selected events for the Permian Period. The Permian Period extended from 298.89 to 251.90 Ma according to Gradstein et al. (in press). The Permian is divided into three epochs, Cisuralian, Guadalupian (with a base at 272.3 Ma) and Lopingian (with a base at 259.8 Ma). A major part of the palynological work from the Permian successions in the Arctic was carried out using the chronostratigraphic scale of Harland et al. (1982). Since stratigraphic standards using Global Stratigraphic Sections and Points was not applied until the late 1990s, correlation and comparison with the earlier palynological charts is difficult; this problem has been com-pounded for the Arctic because a variety of Permian region-al stages have been applied there. This is particularly true around the lower/upper Permian boundary (now Cisuralian/Guadalupian boundary) where, for example, the Roadian stage has been correlated to either the upper Kungurian or to the Ufimian (for example Utting et al. 1997), and the Wordian has been correlated to the Kazanian
{"title":"Permian palynoevents in the circum-Arctic region","authors":"Gunn Mangerud, N. Paterson, J. Bujak","doi":"10.4138/ATLGEOL.2021.004","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2021.004","url":null,"abstract":"Permian palynofloras are recorded around the present-day Arctic and are typically dominated by taeniate and non-taeniate pollen, with intervals of spore domination. The assemblages show close similarities around the Arctic. Based on the published record, we present a compilation of 23 last occurrences (LOs), first occurrences (FOs), and some abundance events. These are anticipated to have regional correlation potential. In general, the Permian palynofloras of the Arctic have not been extensively studied, and the resolution is low due to a general lack of independent age control. doi:10.4138/atlgeol.2021.004 ATLANTIC GEOLOGY 57, 57–69 (2021) 0843-5561|21|0057–0069$2.95|0 (see for example Utting and Piasecki 1995). Utting (1989, p. 234) did not use the Kungurian stage. Utting (1994, p. 9) correlated the Roadian to the “Ufimian (?)” and the Wordian to the “Kazanian (?)” (Fig. 1). See Lucas and Shen (2016) for further discussion on Permian chronostratigraphy. Palynomorphs are the most common, and often the only, fossil group recorded from the Permian, particularly the upper Permian. Palynology is therefore a critical tool for dating and refining stratigraphic correlations of Permian rocks (Stephenson 2016). However, different taxonomic approaches and stratigraphic methods have made comparisons difficult between regions. Especially problematic in the Arctic is the limited communication between Russian and western palynologists; the development especially of a shared taxonomy would likely lead to greatly improved correlations. Permian palynomorphs are primarily pollen and spores (miospores), although acritarchs, algae and foraminiferal linings also occur. For the Cisuralian, fusulinids and conodonts provide independent age determinations for some of the published palynostratigraphic zones. None of the Permian INTRODUCTION This article is a contribution to the Circum-Arctic Palynological Events (CAPE) project, providing a scheme of selected events for the Permian Period. The Permian Period extended from 298.89 to 251.90 Ma according to Gradstein et al. (in press). The Permian is divided into three epochs, Cisuralian, Guadalupian (with a base at 272.3 Ma) and Lopingian (with a base at 259.8 Ma). A major part of the palynological work from the Permian successions in the Arctic was carried out using the chronostratigraphic scale of Harland et al. (1982). Since stratigraphic standards using Global Stratigraphic Sections and Points was not applied until the late 1990s, correlation and comparison with the earlier palynological charts is difficult; this problem has been com-pounded for the Arctic because a variety of Permian region-al stages have been applied there. This is particularly true around the lower/upper Permian boundary (now Cisuralian/Guadalupian boundary) where, for example, the Roadian stage has been correlated to either the upper Kungurian or to the Ufimian (for example Utting et al. 1997), and the Wordian has been correlated to the Kazanian","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"57 1","pages":"057-069"},"PeriodicalIF":1.6,"publicationDate":"2021-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48438682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-24DOI: 10.4138/ATLGEOL.2021.001
J. Bujak, R. Fensome, Gunn Mangerud, G. Williams
Palynomorphs are one of the few groups of fossils that provide biostratigraphic control in marine to nonmarine rocks and can be applied as proxies for paleoenvironmental and paleoclimatic interpretations. Their utility is enhanced by their microscopic size, which is usually less than 200 micrometres; they are thus easily recovered from small rock samples. They occur throughout the Phanerozoic and are therefore invaluable in refining biostratigraphic control of Arctic successions in Alaska, Arctic Canada, Greenland, northern Europe, and northern Russia. The objective of the Circum-Arctic Palynological Event (CAPE) Stratigraphy series of papers is to integrate data published on Arctic palynomorphs to delineate palynological events (palynoevents) across the Arctic for the Silurian to Cenozoic. Once the series of papers is complete, the data will also be used to compile a TimeScale Creator datapack that can be updated and calibrated on an ongoing basis. Palynoevents include taxon originations (first occurrences or FOs) and extinctions (last occurrences, or LOs) and some abundance events. The palynoevents are correlated with established chronostratigraphic horizons such as bases of ammonoid zones or stages, and hence their chronostratigraphy is independent of the absolute time scale in millions of years. In addition to the palynostratigraphic papers, the series includes a paper detailing the paleogeography of the circum-Arctic regions, including informative maps, as well as a paper providing a palynological perspective of the Cenozoic shift from greenhouse to icehouse conditions.
{"title":"Introduction to the “Circum-Arctic Palynological Event Stratigraphy” (CAPE) series of papers","authors":"J. Bujak, R. Fensome, Gunn Mangerud, G. Williams","doi":"10.4138/ATLGEOL.2021.001","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2021.001","url":null,"abstract":"Palynomorphs are one of the few groups of fossils that provide biostratigraphic control in marine to nonmarine rocks and can be applied as proxies for paleoenvironmental and paleoclimatic interpretations. Their utility is enhanced by their microscopic size, which is usually less than 200 micrometres; they are thus easily recovered from small rock samples. They occur throughout the Phanerozoic and are therefore invaluable in refining biostratigraphic control of Arctic successions in Alaska, Arctic Canada, Greenland, northern Europe, and northern Russia. The objective of the Circum-Arctic Palynological Event (CAPE) Stratigraphy series of papers is to integrate data published on Arctic palynomorphs to delineate palynological events (palynoevents) across the Arctic for the Silurian to Cenozoic. Once the series of papers is complete, the data will also be used to compile a TimeScale Creator datapack that can be updated and calibrated on an ongoing basis. Palynoevents include taxon originations (first occurrences or FOs) and extinctions (last occurrences, or LOs) and some abundance events. The palynoevents are correlated with established chronostratigraphic horizons such as bases of ammonoid zones or stages, and hence their chronostratigraphy is independent of the absolute time scale in millions of years. In addition to the palynostratigraphic papers, the series includes a paper detailing the paleogeography of the circum-Arctic regions, including informative maps, as well as a paper providing a palynological perspective of the Cenozoic shift from greenhouse to icehouse conditions.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"57 1","pages":"001-005"},"PeriodicalIF":1.6,"publicationDate":"2021-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45583820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-24DOI: 10.4138/ATLGEOL.2021.003
Gunn Mangerud, Gilda Lopas, J. Bujak
The Carboniferous of the present-day Arctic yields an abundant and diverse association of terrestrial palynomorphs, particularly from Mississippian successions. Relatively few sections have been studied. However, those published so far demonstrate considerable similarities in the palynofloras between Arctic regions. Based on the published record, we present a compilation of 31 last occurrences (LOs), first occurrences (FOs), and some abundance events that have correlation potential around the Arctic. The chronostratigraphic resolution is relatively low, and the lack of independent age control hampers exact age assignments. But for most of these successions, palynology is the only dating tool available.
{"title":"Carboniferous palynoevents in the circum-Arctic region","authors":"Gunn Mangerud, Gilda Lopas, J. Bujak","doi":"10.4138/ATLGEOL.2021.003","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2021.003","url":null,"abstract":"The Carboniferous of the present-day Arctic yields an abundant and diverse association of terrestrial palynomorphs, particularly from Mississippian successions. Relatively few sections have been studied. However, those published so far demonstrate considerable similarities in the palynofloras between Arctic regions. Based on the published record, we present a compilation of 31 last occurrences (LOs), first occurrences (FOs), and some abundance events that have correlation potential around the Arctic. The chronostratigraphic resolution is relatively low, and the lack of independent age control hampers exact age assignments. But for most of these successions, palynology is the only dating tool available.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"57 1","pages":"041-055"},"PeriodicalIF":1.6,"publicationDate":"2021-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46131049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.4138/atlgeol.2021.009
S. Haslett, Bernardine R. Wong
A high-magnitude coastal flood event catastrophically affected the macrotidal Bristol Channel and Severn Estuary in southwest Great Britain, United Kingdom, on 30th January 1607 causing an estimated 2000 fatalities. Historical and physical evidence has provided a basis for the development of a theory that the flood may have been due to a tsunami rather than a storm. Previous studies have collected field data to test this hypothesis including a dataset of 136 wave-transported boulder clasts that was utilised to estimate minimum wave heights through hydrodynamic equations in 2007, but the dataset has hitherto remained unpublished in full. Since 2007 these equations have undergone refinement and for this paper minimum wave heights were recalculated from boulder measurements using revised hydrodynamic equations and presents the complete dataset for the first time. A recent study claiming that such equations are flawed is considered premature, given ongoing refinements to the equations. The results of the present study indicate that a tsunami 4.2 m high can explain the dislodgement of all boulders measured, equivalent to a storm wave height of 16.9 m, which is considerably greater than observed storm wave heights in the region. An up-channel increase in minimum wave height is also suggested by these data, generally corroborating the 2007 study, which may be due to wave amplification caused by the overall funnel-shape of the embayment. The areas worst affected by the 1607 flood are located in the coastal lowlands of the inner Bristol Channel and Severn Estuary, coinciding with the highest minimum estimated wave heights.
{"title":"Recalculation of minimum wave heights from coastal boulder deposits in the Bristol Channel and Severn Estuary, UK: implications for understanding the high-magnitude flood event of AD 1607","authors":"S. Haslett, Bernardine R. Wong","doi":"10.4138/atlgeol.2021.009","DOIUrl":"https://doi.org/10.4138/atlgeol.2021.009","url":null,"abstract":"A high-magnitude coastal flood event catastrophically affected the macrotidal Bristol Channel and Severn Estuary in southwest Great Britain, United Kingdom, on 30th January 1607 causing an estimated 2000 fatalities. Historical and physical evidence has provided a basis for the development of a theory that the flood may have been due to a tsunami rather than a storm. Previous studies have collected field data to test this hypothesis including a dataset of 136 wave-transported boulder clasts that was utilised to estimate minimum wave heights through hydrodynamic equations in 2007, but the dataset has hitherto remained unpublished in full. Since 2007 these equations have undergone refinement and for this paper minimum wave heights were recalculated from boulder measurements using revised hydrodynamic equations and presents the complete dataset for the first time. A recent study claiming that such equations are flawed is considered premature, given ongoing refinements to the equations. The results of the present study indicate that a tsunami 4.2 m high can explain the dislodgement of all boulders measured, equivalent to a storm wave height of 16.9 m, which is considerably greater than observed storm wave heights in the region. An up-channel increase in minimum wave height is also suggested by these data, generally corroborating the 2007 study, which may be due to wave amplification caused by the overall funnel-shape of the embayment. The areas worst affected by the 1607 flood are located in the coastal lowlands of the inner Bristol Channel and Severn Estuary, coinciding with the highest minimum estimated wave heights.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"1 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70754986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-22DOI: 10.4138/ATLGEOL.2020.011
S. Barr, C. White, S. Jensen, T. Palacios, D. V. Rooyen
Scatarie Island and adjacent Hay Island, located 2 km east of the eastern tip of the Avalonian Mira terrane of southern Cape Breton Island, Nova Scotia, contain a succession of epiclastic and other sedimentary rocks of inferred Ediacaran to Cambrian age. The age assignment was based previously on lithological comparison with the Main-à-Dieu Group and overlying Bengal Road and MacCodrum formations of the Mira River Group. Detrital zircon grains from two sandstone samples from the Bengal Road Formation yielded typical Avalonian detrital zircon spectra with middle to late Neoproterozoic, Meso- to Paleoproterozoic (1300–2200 Ma) and Neoarchean ages. They indicate maximum depositional ages of 532.4 ± 4.2 Ma and 525.4 ± 2.4 Ma from essentially the same stratigraphic level, consistent with the interpretation that the rocks are Cambrian. The Bengal Road Formation also yielded scarce organic-walled microfossils including an acanthomorphic acritarch identified as Polygonium sp., also consistent with Cambrian age. The fine-grained siliciclastic succession on Hay Island, tentatively attributed to the MacCodrum Formation, yielded trace fossils, including Teichichnus isp. and Gyrolithes scintillus, that confirm Cambrian age. The Hay Island Gyrolithes scintillus expands the geographical distribution of this ichnospecies, previously known mainly from the Chapel Island Formation of Newfoundland, and represents a younger occurrence.
{"title":"Ediacaran and Cambrian rocks on Scatarie Island and nearby Hay Island, Avalonian Mira terrane, Cape Breton Island, Nova Scotia, Canada","authors":"S. Barr, C. White, S. Jensen, T. Palacios, D. V. Rooyen","doi":"10.4138/ATLGEOL.2020.011","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2020.011","url":null,"abstract":"Scatarie Island and adjacent Hay Island, located 2 km east of the eastern tip of the Avalonian Mira terrane of southern Cape Breton Island, Nova Scotia, contain a succession of epiclastic and other sedimentary rocks of inferred Ediacaran to Cambrian age. The age assignment was based previously on lithological comparison with the Main-à-Dieu Group and overlying Bengal Road and MacCodrum formations of the Mira River Group. Detrital zircon grains from two sandstone samples from the Bengal Road Formation yielded typical Avalonian detrital zircon spectra with middle to late Neoproterozoic, Meso- to Paleoproterozoic (1300–2200 Ma) and Neoarchean ages. They indicate maximum depositional ages of 532.4 ± 4.2 Ma and 525.4 ± 2.4 Ma from essentially the same stratigraphic level, consistent with the interpretation that the rocks are Cambrian. The Bengal Road Formation also yielded scarce organic-walled microfossils including an acanthomorphic acritarch identified as Polygonium sp., also consistent with Cambrian age. The fine-grained siliciclastic succession on Hay Island, tentatively attributed to the MacCodrum Formation, yielded trace fossils, including Teichichnus isp. and Gyrolithes scintillus, that confirm Cambrian age. The Hay Island Gyrolithes scintillus expands the geographical distribution of this ichnospecies, previously known mainly from the Chapel Island Formation of Newfoundland, and represents a younger occurrence.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"56 1","pages":"257-279"},"PeriodicalIF":1.6,"publicationDate":"2020-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43499868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-14DOI: 10.4138/ATLGEOL.2020.010
J. Slack, M. R. V. Baalen, D. Reusch
A reconnaissance geochemical study of 21 samples of sulphidic black phyllite and schist from the Silurian Smalls Falls Formation in Maine was undertaken in order to evaluate compositional changes during regional metamorphism. These samples represent variably metamorphosed black shale. Analyzed samples come from the chlorite zone in northern Maine and the biotite, garnet, and staurolite-andalusite zones in west-central Maine. Strata of the Smalls Falls Formation are distinctive in containing abundant pyrite and/or pyrrhotite (total S = 1.2–9.7 wt%), but only minor organic matter or graphite (TOC = 0.43–1.85 wt%); TOC/S ratios are uniformly low (average = 0.37 ± 0.22). Median enrichment factors were calculated for each element by normalizing the concentration to Ti in each sample to the Ti-normalized median composition of global black shale. In the chlorite zone, moderate to large decreases in enrichment factors (-23.1 to -49.8%) are evident for V, Cr, Cu, Ni, Zn, Pb, Sb, and U, attributed here to various factors during sedimentation plus variable element mobility during diagenesis. With increasing metamorphic grade (biotite through staurolite-andalusite zones), systematic small to extreme decreases (-14.5 to -99.0%) were found for Ba, Sb, Au, and U, together with less-systematic moderate to large decreases (-35.4 to -61.1%) for V and As. Molybdenum shows an extreme decrease (-94.7%) from the garnet to staurolite-andalusite zones. Excluding Ba, these results are interpreted to mainly reflect mobility of trace elements during pyrite recrystallization, and during the metamorphic transformations of organic matter to graphite and of pyrite to pyrrhotite. Moderate to large increases for Rb (+28.1 to +61.5%) and Th (+39.1 to +47.3%) from the biotite to staurolite-andalusite zones likely record the introduction of alkalis and mass loss, respectively, during metamorphism. Three samples from one site in the garnet zone differ in having anomalously high Fe/Al and low La/Yb ratios, attributed here to epigenetic formation of pyrite and related leaching of light rare earth elements during syn-metamorphic, channelized fluid flow.Geologic and geochemical data indicate that strata of the Smalls Falls Formation were deposited during an interval of anoxia on the northwestern flank of the Central Maine Basin, for which detrital sources included an evolved continental arc. Onset of anoxia coincided with deposition of the Mayflower Hill Formation of the Vassalboro Group, on the basin’s southeastern flank, related to emergence of the Brunswick subduction complex. We suggest that this emergence played a role in promoting both lateral and vertical circulation changes, nutrient loading, and deoxygenation through subsequent basin closure that culminated with Acadian deformation and metamorphism. Based on the relatively high contents of total sulphur present in our Smalls Falls samples, sediments in the Black Sea represent the only known plausible candidate among those in mo
{"title":"Regional geochemical variations in a metamorphosed black shale: a reconnaissance study of the Silurian Smalls Falls Formation, Maine, USA","authors":"J. Slack, M. R. V. Baalen, D. Reusch","doi":"10.4138/ATLGEOL.2020.010","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2020.010","url":null,"abstract":"A reconnaissance geochemical study of 21 samples of sulphidic black phyllite and schist from the Silurian Smalls Falls Formation in Maine was undertaken in order to evaluate compositional changes during regional metamorphism. These samples represent variably metamorphosed black shale. Analyzed samples come from the chlorite zone in northern Maine and the biotite, garnet, and staurolite-andalusite zones in west-central Maine. Strata of the Smalls Falls Formation are distinctive in containing abundant pyrite and/or pyrrhotite (total S = 1.2–9.7 wt%), but only minor organic matter or graphite (TOC = 0.43–1.85 wt%); TOC/S ratios are uniformly low (average = 0.37 ± 0.22). Median enrichment factors were calculated for each element by normalizing the concentration to Ti in each sample to the Ti-normalized median composition of global black shale. In the chlorite zone, moderate to large decreases in enrichment factors (-23.1 to -49.8%) are evident for V, Cr, Cu, Ni, Zn, Pb, Sb, and U, attributed here to various factors during sedimentation plus variable element mobility during diagenesis. With increasing metamorphic grade (biotite through staurolite-andalusite zones), systematic small to extreme decreases (-14.5 to -99.0%) were found for Ba, Sb, Au, and U, together with less-systematic moderate to large decreases (-35.4 to -61.1%) for V and As. Molybdenum shows an extreme decrease (-94.7%) from the garnet to staurolite-andalusite zones. Excluding Ba, these results are interpreted to mainly reflect mobility of trace elements during pyrite recrystallization, and during the metamorphic transformations of organic matter to graphite and of pyrite to pyrrhotite. Moderate to large increases for Rb (+28.1 to +61.5%) and Th (+39.1 to +47.3%) from the biotite to staurolite-andalusite zones likely record the introduction of alkalis and mass loss, respectively, during metamorphism. Three samples from one site in the garnet zone differ in having anomalously high Fe/Al and low La/Yb ratios, attributed here to epigenetic formation of pyrite and related leaching of light rare earth elements during syn-metamorphic, channelized fluid flow.Geologic and geochemical data indicate that strata of the Smalls Falls Formation were deposited during an interval of anoxia on the northwestern flank of the Central Maine Basin, for which detrital sources included an evolved continental arc. Onset of anoxia coincided with deposition of the Mayflower Hill Formation of the Vassalboro Group, on the basin’s southeastern flank, related to emergence of the Brunswick subduction complex. We suggest that this emergence played a role in promoting both lateral and vertical circulation changes, nutrient loading, and deoxygenation through subsequent basin closure that culminated with Acadian deformation and metamorphism. Based on the relatively high contents of total sulphur present in our Smalls Falls samples, sediments in the Black Sea represent the only known plausible candidate among those in mo","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"56 1","pages":"231-255"},"PeriodicalIF":1.6,"publicationDate":"2020-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46543888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-03DOI: 10.4138/ATLGEOL.2020.009
D. Loomer, K. MacQuarrie, T. Al
Isotopic analyses of natural gas from the Stoney Creek oil field in New Brunswick indicate carbon (δ13C) and hydrogen (δ2H) values in methane (C1) of -42.4 ± 0.7‰ VPDB and -220.9 ± 3.2‰ VSMOW, respectively. Isotopic data and a gas molecular ratio of 12 ± 1 indicate a wet thermogenic gas formed with oil near the onset of the oil-gas transition zone. The isotopic profiles of the C1–C5 hydrocarbon gases are consistent with kinetic isotope effect models. The Albert Formation of the Horton Group hosts the Stoney Creek oil field (SCOF) and the McCully gas field (MCGF) the only other gas-producing field in the province. Both are thermogenic in origin; however, the SCOF gas has a lower thermal maturity than the MCGS. Hydrocarbon gas composition in shallow aquifers across southeastern New Brunswick was also evaluated. Gas source interpretations based on δ13C and δ2H values are uncertain; oxidation and biogenic overprinting are common and complicate interpretation. The effect of oxidation on δ13C and δ2H values was apparent when C1 concentrations were ≤1 mg/L. In some samples with C1 concentrations >5 mg/L, isotopic discrimination methods point to a biogenic origin. However, the molecular ratios <75 and the presence of >C3 fractions, indicate a thermogenic origin. This suggests a thermogenic isotopic signature has been overprinted by biological activity.
{"title":"Comparison of isotopic compositions of hydrocarbon gas in shallow groundwater and a deep oil and natural gas reservoir in southeastern New Brunswick, Canada","authors":"D. Loomer, K. MacQuarrie, T. Al","doi":"10.4138/ATLGEOL.2020.009","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2020.009","url":null,"abstract":"Isotopic analyses of natural gas from the Stoney Creek oil field in New Brunswick indicate carbon (δ13C) and hydrogen (δ2H) values in methane (C1) of -42.4 ± 0.7‰ VPDB and -220.9 ± 3.2‰ VSMOW, respectively. Isotopic data and a gas molecular ratio of 12 ± 1 indicate a wet thermogenic gas formed with oil near the onset of the oil-gas transition zone. The isotopic profiles of the C1–C5 hydrocarbon gases are consistent with kinetic isotope effect models. The Albert Formation of the Horton Group hosts the Stoney Creek oil field (SCOF) and the McCully gas field (MCGF) the only other gas-producing field in the province. Both are thermogenic in origin; however, the SCOF gas has a lower thermal maturity than the MCGS. Hydrocarbon gas composition in shallow aquifers across southeastern New Brunswick was also evaluated. Gas source interpretations based on δ13C and δ2H values are uncertain; oxidation and biogenic overprinting are common and complicate interpretation. The effect of oxidation on δ13C and δ2H values was apparent when C1 concentrations were ≤1 mg/L. In some samples with C1 concentrations >5 mg/L, isotopic discrimination methods point to a biogenic origin. However, the molecular ratios <75 and the presence of >C3 fractions, indicate a thermogenic origin. This suggests a thermogenic isotopic signature has been overprinted by biological activity.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"1 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2020-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43948798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-13DOI: 10.4138/ATLGEOL.2020.008
L. Fyffe, W. Gardiner
Robert Albert Stuart, the High Sheriff of Charlotte County, deserves credit for establishing the black granite monument industry in New Brunswick. In the late 19th to early 20th centuries, he opened three quarries in mafic plutonic rocks in the vicinity of the Chickahominy Mountain, north of St. Andrews: the Bocabec black granite quarry (1893), the Steen Lake black granite quarry (1895), and the Glenelg porphyry quarry (1906). Much of the information in brief articles in local newspapers lacks sufficient detail to gain a full understanding of the historical development of these quarries. To obtain a clearer timeline for production of stone from the quarries, the rock type in each was examined and compared to black granite monuments in nearby cemeteries known to be sourced from these specific quarries. Previous investigations did not entirely rule out the possibility that the Stuart quarries may have been a source for the headstones placed in the Fairview Lawn Cemetery in Halifax, Nova Scotia, to mark the graves of some of those who were lost when the Titanic sank in 1912. Our detailed analysis of rock textures and production histories leads us to conclude that none of the Stuart quarries could have been a source for the Titanic headstones and supports the previous assessment that they came from Charles Hanson quarry.
夏洛特县的高级治安官罗伯特·阿尔伯特·斯图尔特(Robert Albert Stuart)在新不伦瑞克建立了黑色花岗岩纪念碑产业，值得称赞。在19世纪末到20世纪初，他在圣安德鲁斯北部奇卡霍米尼山附近的基性深成岩中开了三个采石场:Bocabec黑色花岗岩采石场(1893年)、Steen Lake黑色花岗岩采石场(1895年)和Glenelg斑岩采石场(1906年)。当地报纸上的简短文章中的许多信息缺乏足够的细节，无法充分了解这些采石场的历史发展。为了获得采石场生产石头的更清晰的时间表，每个采石场的岩石类型都被检查，并与附近墓地中已知来自这些特定采石场的黑色花岗岩纪念碑进行比较。之前的调查并没有完全排除斯图尔特采石场可能是新斯科舍哈利法克斯Fairview Lawn公墓墓碑来源的可能性，这些墓碑是为了纪念1912年泰坦尼克号沉没时失去的一些人的坟墓。我们对岩石结构和生产历史的详细分析使我们得出结论，斯图尔特采石场都不可能是泰坦尼克号墓碑的来源，并支持了之前的评估，即它们来自查尔斯汉森采石场。
{"title":"Investigation of Sheriff Stuart’s black granite quarries in Charlotte County, southwestern New Brunswick: implications for the source of the titanic headstones in Halifax, Nova Scotia","authors":"L. Fyffe, W. Gardiner","doi":"10.4138/ATLGEOL.2020.008","DOIUrl":"https://doi.org/10.4138/ATLGEOL.2020.008","url":null,"abstract":"Robert Albert Stuart, the High Sheriff of Charlotte County, deserves credit for establishing the black granite monument industry in New Brunswick. In the late 19th to early 20th centuries, he opened three quarries in mafic plutonic rocks in the vicinity of the Chickahominy Mountain, north of St. Andrews: the Bocabec black granite quarry (1893), the Steen Lake black granite quarry (1895), and the Glenelg porphyry quarry (1906). Much of the information in brief articles in local newspapers lacks sufficient detail to gain a full understanding of the historical development of these quarries. To obtain a clearer timeline for production of stone from the quarries, the rock type in each was examined and compared to black granite monuments in nearby cemeteries known to be sourced from these specific quarries. Previous investigations did not entirely rule out the possibility that the Stuart quarries may have been a source for the headstones placed in the Fairview Lawn Cemetery in Halifax, Nova Scotia, to mark the graves of some of those who were lost when the Titanic sank in 1912. Our detailed analysis of rock textures and production histories leads us to conclude that none of the Stuart quarries could have been a source for the Titanic headstones and supports the previous assessment that they came from Charles Hanson quarry.","PeriodicalId":49235,"journal":{"name":"Atlantic Geology","volume":"56 1","pages":"189-206"},"PeriodicalIF":1.6,"publicationDate":"2020-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42388282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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