Ashton Embry

Natural Resources Canada, Calgary, Emeritus

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Address: Calgary, Alberta, Canada

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Gabriel Gutierrez-Alonso

University of Salamanca

George Lawson

The Australian National University

Beata Gruszka

Adam Mickiewicz University in Poznań

Stephen W Merkel

Vrije Universiteit Amsterdam

Ziya Öniş

Koç University

Michael Wagreich

University of Vienna

Thomas Algeo

University of Cincinnati

Javier de Carlos Izquierdo

Universidad Complutense de Madrid

Geologica Acta

Universitat de Barcelona

Jana Javornik

University of East London

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Papers by Ashton Embry

The Schei Point and Blaa Mountain groups [middle-upper triassic], Sverdrup Basin, Canadian Arctic Archipelago

Sequence boundaries and sequence hierarchies: problems and proposals

Norwegian Petroleum Society Special Publications, 1995

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Present heat flow and paleo-geothermal regime in the Canadian Arctic margin: analysis of industrial thermal data and coalification gradients

Tectonophysics, 1998

Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep w... more Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep wells of the Canadian Arctic Archipelago. Corrected bottom hole temperature (BHT) data and drill stem test (DST) temperatures were used to determine the thermal gradients for sites for which the quality of data was sufficient. Thermal gradients evaluated for depths below the base of permafrost for the onshore wells and below sea bottom for the offshore wells were combined with the estimates of effective thermal conductivity to approximate heat flow for these sites. The present geothermal gradient is in the 15-50 mK/m range (mean = 31 4-7 mK/m). Present heat flow is mainly in the 35-90 mW/m 2 range (mean = 53 4-12 mW/m2). Maps of the present geothermal gradient and present heat flow have been constructed for the basin. The analysis of vitrinite reflectance profiles and the calculation of logarithmic coalification gradients for 101 boreholes in the Sverdrup Basin showed large variations related in many cases to regional variations of present terrestrial heat flow. Paleo-geothermal gradients estimated from these data are mostly in the range of 15-50 mK/m (mean = 28 5= 9 mK/m) and paleo-heat flow is in the 40-90 mW/m 2 range (mean = 57 ± 18 mW/m 2) related to the time of maximum burial in the Early Tertiary. Mean values of the present heat flow and paleo-heat flow for the Sverdrup Basin are almost identical considering the uncertainties of the methods used (53 + 12 versus 57 4-18 mW/m 2, respectively). Present geothermal gradients and paieo-geothermal gradients are also close when means are compared (31 4-7 versus 28 4-9 mK/m respectively). A zone of high present heat flow and a paleo-heat flow zone coincide in places with the northeastern-southwestern incipient rift landward of the Arctic margin first described by . Correlation between present heat flow and paleo-heat flow for the time of maximum burial in the earliest Tertiary suggests that the high heat flow zone has prevailed since that time.

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Absolute water depth limits of late devonian paleoecological zones

Geologische Rundschau, 1972

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Stratigraphy and tectonic significance of Cretaceous volcanism in the Queen Elizabeth Islands, Canadian Arctic Archipelago: Reply

Canadian Journal of Earth Sciences, 1989

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Chapter 13 Sverdrup Basin

The Sverdrup Basin is located in the Canadian Arctic Islands. It is 1,000 km by 350 km and is fil... more The Sverdrup Basin is located in the Canadian Arctic Islands. It is 1,000 km by 350 km and is filled with up to 13 km of Carboniferous to Paleogene strata. The basin initially developed in Early Carboniferous as a rift basin upon highly deformed Early Paleozoic strata of the Ellesmerian Orogenic Belt. The development of the basin can be broken into eight phases, each being characterized by a distinctive combination of tectonic, depositional and climatic regimes and separated by episodes of widespread uplift and basin reorganization.The Upper Paleozoic strata are up to 5 km thick and are characterized by a distinct shelf to deep basin topography. Carbonate strata dominated the shelf until Middle Permian and were supplanted by siliciclastics and chert in Middle and Late Permian when the climate cooled. Triassic siliciclastics are up to 4 km thick and they filled the deep, central basin by Late Triassic.From latest Triassic to earliest Cretaceous the basin was occupied by shallow siliciclastics shelves and up to 2 km of strata accumulated. Renewed rifting in Early Cretaceous resulted in a thick succession (2 km) of Early Cretaceous non-marine to shallow marine strata with units of basalts in the northeast. Widespread diabase sill and dyke intrusion, likely related to the Alpha Ridge Plume and the opening of the Amerasia Ocean Basin, occurred at this time. Following an interval of low subsidence and low sediment supply in the Late Cretaceous, the basin began to be deformed in earliest Paleocene by the Eurekan Orogeny driven by the counterclockwise rotation of Greenland. Local foreland basins developed and contain up to 3 km of Paleocene–Eocene strata. In Late Eocene the basin was uplifted and deformed by faulting and folding with deformation decreasing southwestwards.Eighteen oil and gas fields have been discovered in Eurekan anticlines and potential prospects include traps associated with Eurekan structures, salt domes, reefs and prominent unconformities. Widespread petroleum source rocks are documented in Middle and Upper Triassic strata and likely occur with other stratigraphic intervals from Carboniferous to Lower Cretaceous.

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Tectonic and eustatic signals in the sequence stratigraphy of the Upper Devonian Canadaway Group, New York state: Discussion

Aapg Bulletin, 2002

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Phanerozoic sea-level changes

Earth-science Reviews, 1993

Late Paleozoic-Mesozoic Evolution of Arctic North America: ABSTRACT

Aapg Bulletin, 1987

Stratigraphy and tectonic significance of Cretaceous volcanism in the Queen Elizabeth Islands, Canadian Arctic Archipelago

Canadian Journal of Earth Sciences, 1988

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Chapter 13 Sverdrup Basin

Sedimentary Basins of the World, 2008

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Transgressive-Regressive (T-R) Sequence Stratigraphy

Sequence Stratigraphic Models for Exploration and Production: Evolving Methodology, Emerging Models, and Application Histories: 22nd Annual, 2002

A sequence, as originally defined by Sloss and colleagues, was a stratigraphic unit bounded by su... more A sequence, as originally defined by Sloss and colleagues, was a stratigraphic unit bounded by subaerial unconformities. Such a stratigraphic unit proved to be of limited value because, in most instances, sequences could be recognized only on the margins of a basin where subaerial unconformities were present. Vail and colleagues greatly expanded the utility of sequences for basin analysis when they redefined the term as a unit bounded by unconformities or correlative conformities. The addition of correlative conformities allowed a sequence to potentially be recognized over an entire basin.

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Lower Triassic bryozoan beds from Ellesmere Island, High Arctic, Canada

Polar Research, 2008

In the Sverdrup Basin (Canadian Arctic), the Lower Triassic Blind Fiord Formation, comprising sil... more In the Sverdrup Basin (Canadian Arctic), the Lower Triassic Blind Fiord Formation, comprising siltstone and shale, overlies various Middle to Late Permian (post-Wordian) sedimentary units. This formation is subdivided into three members: the Confederation Point, Smith Creek and Svartfjeld members of, respectively, Griesbachian–Dienerian, Smithian–Spathian and Spathian ages. Lower Triassic bryozoan beds are known from many sections of Ellesmere Island, but have never been studied in detail. During the Early Triassic biotic recovery interval, immediately following the Permian/Triassic extinction event, only one new bryozoan genus evolved in the Boreal region: Arcticopora. The first lower Triassic bryozoan bed appears in the upper part of the Confederation Point Member, and is dated as late Dienerian. Succeeding bryozoan levels occur in the upper Smith Creek Member, and are late Smithian–early Spathian in age. Bryozoan beds occupy a similar stratigraphic position in Spitsbergen. There, they occur scattered in silt to coarse sandstone beds, but also in bryozoan-dominated packstone beds resembling the packstone units in the uppermost part of the Confederation Point Member of Ellesmere Island. Previously, bryozoan-rich beds of Triassic age have not been reported, and the present work fills an important time gap in the bryozoan carbonate database.

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Present heat flow and paleo-geothermal regime in the Canadian Arctic margin: analysis of industrial thermal data and coalification gradients

Tectonophysics, 1998

Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep w... more Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep wells of the Canadian Arctic Archipelago. Corrected bottom hole temperature (BHT) data and drill stem test (DST) temperatures were used to determine the thermal gradients for sites for which the quality of data was sufficient. Thermal gradients evaluated for depths below the base of permafrost for the onshore wells and below sea bottom for the offshore wells were combined with the estimates of effective thermal conductivity to approximate heat flow for these sites. The present geothermal gradient is in the 15–50 mK/m range (mean = 31 ± 7 mK/m). Present heat flow is mainly in the 35–90 mW/m2 range (mean = 53 ± 12 mW/m2). Maps of the present geothermal gradient and present heat flow have been constructed for the basin. The analysis of vitrinite reflectance profiles and the calculation of logarithmic coalification gradients for 101 boreholes in the Sverdrup Basin showed large variations related in many cases to regional variations of present terrestrial heat flow. Paleo-geothermal gradients estimated from these data are mostly in the range of 15–50 mK/m (mean = 28 ± 9 mK/m) and paleo-heat flow is in the 40–90 mW/m2 range (mean = 57 ± 18 mW/m2) related to the time of maximum burial in the Early Tertiary. Mean values of the present heat flow and paleo-heat flow for the Sverdrup Basin are almost identical considering the uncertainties of the methods used (53 ± 12 versus 57 ± 18 mW/m2, respectively). Present geothermal gradients and paleo-geothermal gradients are also close when means are compared (31 ± 7 versus 28 ± 9 mK/m respectively). A zone of high present heat flow and a paleo-heat flow zone coincide in places with the northeastern-southwestern incipient rift landward of the Arctic margin first described by Balkwill and Fox (1982). Correlation between present heat flow and paleo-heat flow for the time of maximum burial in the earliest Tertiary suggests that the high heat flow zone has prevailed since that time.

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Sequence boundaries and sequence hierarchies: problems and proposals

Norwegian Petroleum Society Special Publications, 1995

Significant problems are being encountered by stratigraphers as they attempt to apply Exxonian se... more Significant problems are being encountered by stratigraphers as they attempt to apply Exxonian sequence analysis to the depositional record. The most serious problem is one of consistent and objective boundary recognition. The unconformable portion of the boundary usually can be recognized with reasonable objectivity but a major problem occurs when the boundary is a “correlative conformity”. The Exxon model defines such a surface as the depositional surface which existed at the time of the end of base level (relative sea level) fall. In many cases this theoretical surface has no apparent lithologic expression and cannot be recognized objectively. Thus correlation of a depositional sequence throughout a basin is either impossible or is an extremely subjective exercise.To remedy the problem of boundary recognition it is proposed that a sequence boundary be placed at the subaerial unconformity and at the correlative transgressive surface. The transgressive surface is ideal for the conformable portion of a sequence boundary because: (1) it is very distinctive lithologically and occurs in both ramp and shelf/slope settings; (2) it has only minor diachroneity in most cases; (3) it merges with the basinward termination of the unconformable portion of the sequence boundary. This methodology results in a practical, genetic unit (T-R sequence) which can be objectively correlated.A second problem with current sequence stratigraphic practice is the use of a sequence hierarchy scheme which is based on frequency of boundary occurrence. This system is very subjective in nature and is prone to circular reasoning.To counter the hierarchy problem, a hierarchical arrangement of T-R sequence boundaries has been established using boundary characteristics which include: (1) extent of the boundary, (2) extent of the unconformable portion of the boundary, (3) degree of deformation of strata directly underlying the boundary, (4) magnitude of deepening across the boundary, (5) degree of change of the depositional regime across the boundary, and (6) degree of change of the tectonic regime across the boundary. These characteristics reflect the magnitude of base level changes which generate sequence boundaries and this linkage allows the establishment of a hierarchy. Five distinct orders of sequence boundaries are recognized in the hierarchy and vary from 1st order boundaries which are widespread subaerial unconformities associated with significant deformation, to 5th order boundaries which are transgressive surfaces which can be correlated only locally.

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Absolute water depth limits of late devonian paleoecological zones

Ein verfeinertes Schema zur Klassifizierung von Riffkalksteinen, das die Bestandteile über 2 mm (... more Ein verfeinertes Schema zur Klassifizierung von Riffkalksteinen, das die Bestandteile über 2 mm (den konglomeratischen Anteil) und die Art der organischen Bindung besser berücksichtigt, ermöglicht eine genauere Faziesbeschreibung von organischen Riffen. Die Klassifizierung wurde auf oberdevonische Riffe angewandt, die im nordöstlichen Teil der Banks Island, Canadian Arctic Archipelago, anstehen. Die Faziesverteilung und -abfolge in einem der Riffe ermöglichte es, die absoluten Wassertiefen von drei wesentlichen oberdevonischen Zonen zu bestimmen. Korallen waren die vorherrschende Fauna in Wasser tiefer als 21 m; tabulare Stromatoporiden wuchsen zwischen 21 m und 9 m Wassertiefe; massive Stromatoporiden waren die vorherrschende Fauna zwischen 9 m und Meeresspiegel. Der wichtigste Faktor, der die Tiefen der Zonengrenzen bestimmte, war die Wellenenergie (normaler Wellentiefgang 9 m; Sturmwellentiefgang 21 m). A refined scheme of reefal limestone classification, which places more emphasis on the > 2 mm components (conglomeratic fraction) and on the mode of organic binding, allows for a more detailed facies description of organic buildups. The classification has been applied to Late Devonian organic buildups which outcrop on northeastern Banks Island, Canadian Arctic Archipelago. The distribution and sequences of facies in one organic buildup has led to the determination of absolute water depth limits of three major Late Devonian paleoecological zones. Corals were the dominant fauna below 70 feet (21 m.); tabular stromatoporoids flourished between 70 feet (21 m.) and 30 feet (9 m.) of water depth; massive stromatoporoids were the dominant fauna between 30 feet (9 m.) and sea level. The main controlling factor on the depth limits of the zones was wave energy (normal wave base, 30 feet [9 m.]; storm wave base, 70 feet [21 m.]). Une classification schématique et détaillée des calcaires de récif supérieur insistant sur les constituents d'une grosseur à 2 mm. (fraction comglomeratique) et sur la manière avec laquelle les constituents ont été lié spar des organismes permet une déscription plus détaillée des facies d'édifices organiques. Elle a été appliquée à l'étude de ré cifs qui affleurent dans la partie Nord-est des Banks Island dans l'archipel arctique canadien. Lad distribution et la succession des facies dans un édifice organique ont permit de préciser les limites des profondeurs absolues d'eau de trois zones paléoécologiques principales du dévonien supérieur. Des coraux formaient la faune prépondérante audessous de 21 m.; stromatopéroides tabulaires abondaient entre 21 m. et 9 m. de profondeur; des stromatoporoides massifs formaient la faune prépondérante entre la surface de la mer et 9m. de profondeur. Le facteur principal fixant les limites de profondeur des zones paléoécologiques était l'énergie des vagues (base des vagues normales 9 m., base des vagues de tempête 21 m.). Схема классификации рифовых известняков, при которой можно различать составные части боле е 2 мм (конгломератная ч асть) и вид органических образо ваний, разрешает точнее опи сать фаций рифов. Эту классификацию приме нили к верхне-девонским ри фам, которые образуют северо-восточную час ть банок исландского и к анадского арктическ ого архипелага. Распреде ление фация а его чередование в ри фе разрешают определ ить абсолютную глубину в оды в трех важных верхнед евонских зонах. Корал лы являлись господствующей фацией на глубине бол ее 21 м; стержневые стро матолиты росли на глубине 21−9 м; массивные строма топориды господство вали от глубины 9 м до поверхно сти воды. Важнейшим факто ром, определяющим глу бину границы этих зон, явилась энергия волн охода (обычные волны д остигают глубины 9 м., а при шторме — 21 м).

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Triassic transgressive-regressive cycles in the Sverdrup Basin, Svalbard and the Barents Shelf

Correlation in Hydrocarbon Exploration, 1989

Correlation of Upper Palaeozoic and Mesozoic sequences between Svalbard, Canadian Arctic Archipelago, and northern Alaska

Correlation in Hydrocarbon Exploration, 1989

Sequence correlation: Upper Triassic to Lower Jurassic succession, Canadian and Norwegian Arctic

Correlation in Hydrocarbon Exploration, 1989

Correlating middle Cretaceous palynological records from the Canadian High Arctic based on sections from the Sverdrup Basin and the Eclipse Trough

Palynology, 2012

Quantitative palynological analyses undertaken on the middle Cretaceous Hassel Formation of the S... more Quantitative palynological analyses undertaken on the middle Cretaceous Hassel Formation of the Sverdrup Basin and reputedly equivalent rocks from the Eclipse Trough, about 850 km east, provide convincing evidence that they are coeval and of Late Albian–Cenomanian age. We base this conclusion on statistical definition of two palynomorph populations that occur in both spot samples from the Eclipse Trough and in samples from a measured section at Hoodoo Dome, Ellef Ringnes Island in the central Sverdrup Basin, which demonstrate a broad correlation to previously reported palynofloras from North America. By applying ordination techniques, we demonstrate that the range of variability of palynomorph composition of samples from the reputed Hassel Formation in the Eclipse Trough are within the range of variability defined for samples from the Hassel Formation, Hoodoo Dome. Comparable proportions of dicotyledonous angiosperm pollen characterize samples from both localities, but diversity and relative abundance are lower in both of the Canadian Arctic deposits than in more southern Middle and Late Albian–Cenomanian-aged rocks of North America. To explain this, we propose that restricted angiosperm diversity and continued dominance of gymnosperms and ferns into the Cenomanian in the Canadian Arctic reflect relatively cool continental climate conditions or barriers to migration, such as the Western Interior Seaway.

The Schei Point and Blaa Mountain groups [middle-upper triassic], Sverdrup Basin, Canadian Arctic Archipelago

Sequence boundaries and sequence hierarchies: problems and proposals

Norwegian Petroleum Society Special Publications, 1995

Download

Present heat flow and paleo-geothermal regime in the Canadian Arctic margin: analysis of industrial thermal data and coalification gradients

Tectonophysics, 1998

Download

Absolute water depth limits of late devonian paleoecological zones

Geologische Rundschau, 1972

Download

Stratigraphy and tectonic significance of Cretaceous volcanism in the Queen Elizabeth Islands, Canadian Arctic Archipelago: Reply

Canadian Journal of Earth Sciences, 1989

Download

Chapter 13 Sverdrup Basin

Download

Tectonic and eustatic signals in the sequence stratigraphy of the Upper Devonian Canadaway Group, New York state: Discussion

Aapg Bulletin, 2002

Download

Phanerozoic sea-level changes

Earth-science Reviews, 1993

Late Paleozoic-Mesozoic Evolution of Arctic North America: ABSTRACT

Aapg Bulletin, 1987

Stratigraphy and tectonic significance of Cretaceous volcanism in the Queen Elizabeth Islands, Canadian Arctic Archipelago

Canadian Journal of Earth Sciences, 1988

Download

Chapter 13 Sverdrup Basin

Sedimentary Basins of the World, 2008

Download

Transgressive-Regressive (T-R) Sequence Stratigraphy

Sequence Stratigraphic Models for Exploration and Production: Evolving Methodology, Emerging Models, and Application Histories: 22nd Annual, 2002

Download

Lower Triassic bryozoan beds from Ellesmere Island, High Arctic, Canada

Polar Research, 2008

Download

Present heat flow and paleo-geothermal regime in the Canadian Arctic margin: analysis of industrial thermal data and coalification gradients

Tectonophysics, 1998

Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep w... more Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep wells of the Canadian Arctic Archipelago. Corrected bottom hole temperature (BHT) data and drill stem test (DST) temperatures were used to determine the thermal gradients for sites for which the quality of data was sufficient. Thermal gradients evaluated for depths below the base of permafrost for the onshore wells and below sea bottom for the offshore wells were combined with the estimates of effective thermal conductivity to approximate heat flow for these sites. The present geothermal gradient is in the 15–50 mK/m range (mean = 31 ± 7 mK/m). Present heat flow is mainly in the 35–90 mW/m2 range (mean = 53 ± 12 mW/m2). Maps of the present geothermal gradient and present heat flow have been constructed for the basin. The analysis of vitrinite reflectance profiles and the calculation of logarithmic coalification gradients for 101 boreholes in the Sverdrup Basin showed large variations related in many cases to regional variations of present terrestrial heat flow. Paleo-geothermal gradients estimated from these data are mostly in the range of 15–50 mK/m (mean = 28 ± 9 mK/m) and paleo-heat flow is in the 40–90 mW/m2 range (mean = 57 ± 18 mW/m2) related to the time of maximum burial in the Early Tertiary. Mean values of the present heat flow and paleo-heat flow for the Sverdrup Basin are almost identical considering the uncertainties of the methods used (53 ± 12 versus 57 ± 18 mW/m2, respectively). Present geothermal gradients and paleo-geothermal gradients are also close when means are compared (31 ± 7 versus 28 ± 9 mK/m respectively). A zone of high present heat flow and a paleo-heat flow zone coincide in places with the northeastern-southwestern incipient rift landward of the Arctic margin first described by Balkwill and Fox (1982). Correlation between present heat flow and paleo-heat flow for the time of maximum burial in the earliest Tertiary suggests that the high heat flow zone has prevailed since that time.

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Sequence boundaries and sequence hierarchies: problems and proposals

Norwegian Petroleum Society Special Publications, 1995

Download

Absolute water depth limits of late devonian paleoecological zones

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Triassic transgressive-regressive cycles in the Sverdrup Basin, Svalbard and the Barents Shelf

Correlation in Hydrocarbon Exploration, 1989