Eureka Sound Formation Research Articles

A sand tiger shark–dominated fauna from the Eocene Arctic greenhouse

ABSTRACTWe describe a new shark fauna from Canada's westernmost Arctic island, Banks Island, Northwest Territories, based upon thousands of shark teeth recovered from lower–middle Eocene sediments of the Cyclic Member (Eureka Sound Formation) on northern Banks Island, Northwest Territories (∼74°N latitude). Based upon palynology, the sediments preserving the shark teeth are late early to middle Eocene in age and likely span the Early Eocene Climatic Optimum (EECO). The low-diversity faunal assemblage is dominated by the sand tiger sharks Striatolamia and Carcharias, but also includes relatively rare teeth of the carcharhinid Physogaleus (extinct relative of sharpnose and tiger sharks) and very rare teeth of the odontaspidid Odontaspis winkleri. We also report the occurrence of the ray Myliobatis. Based upon analogy with extant Carcharias taurus and Myliobatis, the presence of Carcharias and Myliobatis on northern Banks Island corroborates the relatively warm sea surface temperatures estimated by others for the Eocene Arctic Ocean. We hypothesize that the low diversity of the Banks Island shark fauna, in comparison with other early Eocene brackish, shallow-marine chondrichthyan assemblages such as the Abbey Wood (U.K.) fauna, is probably due to environmental factors, including reduced salinity.

First record of eocene bony fishes and crocodyliforms from Canada's Western Arctic.

BackgroundDiscovery of Eocene non-marine vertebrates, including crocodylians, turtles, bony fishes, and mammals in Canada’s High Arctic was a critical paleontological contribution of the last century because it indicated that this region of the Arctic had been mild, temperate, and ice-free during the early – middle Eocene (∼53–50 Ma), despite being well above the Arctic Circle. To date, these discoveries have been restricted to Canada’s easternmost Arctic – Ellesmere and Axel Heiberg Islands (Nunavut). Although temporally correlative strata crop out over 1,000 km west, on Canada’s westernmost Arctic Island – Banks Island, Northwest Territories – they have been interpreted as predominantly marine. We document the first Eocene bony fish and crocodyliform fossils from Banks Island.Principal FindingsWe describe fossils of bony fishes, including lepisosteid (Atractosteus), esocid (pike), and amiid, and a crocodyliform, from lower – middle Eocene strata of the Cyclic Member, Eureka Sound Formation within Aulavik National Park (∼76°N. paleolat.). Palynology suggests the sediments are late early to middle Eocene in age, and likely spanned the Early Eocene Climatic Optimum (EECO).Conclusions/SignificanceThese fossils extend the geographic range of Eocene Arctic lepisosteids, esocids, amiids, and crocodyliforms west by approximately 40° of longitude or ∼1100 km. The low diversity bony fish fauna, at least at the family level, is essentially identical on Ellesmere and Banks Islands, suggesting a pan-High Arctic bony fish fauna of relatively basal groups around the margin of the Eocene Arctic Ocean. From a paleoclimatic perspective, presence of a crocodyliform, gar and amiid fishes on northern Banks provides further evidence that mild, year-round temperatures extended across the Canadian Arctic during early – middle Eocene time. Additionally, the Banks Island crocodyliform is consistent with the phylogenetic hypothesis of a Paleogene divergence time between the two extant alligatorid lineages Alligator mississippiensis and A. sinensis, and high-latitude dispersal across Beringia.

The Haughton Impact Structure: Summary and Synthesis of the Results of the HISS Project*

Abstract— Surface and subsurface structural studies undertaken under the Haughton impact structure study (HISS) project indicate that the 23 Ma‐old Haughton impact structure, (Devon Island, Canadian Arctic) consists of a central basin of uplifted strata, an inner zone of uplifted megablocks at 3.5–5.5 km radius, a complex, faulted annulus of megablocks at 5.5–7.0 km radius and an outer zone of downfaulted blocks. No evidence of a previously suggested structural multi‐ring form was found. The geophysical studies suggest an original diameter of 24 km, slightly larger than previous estimates and the seismic data indicate considerably more faulting in the western portion than has been mapped from surface exposures. Detailed studies of the allochthonous breccia deposits found no major radial variations in lithology and shock levels. The only anomaly is the concentration of highly shocked, cobble‐sized clasts in the central area coincident with the maximum gravity and magnetic anomalies. It is suggested that this local component is related to the highly shocked rocks of the central uplift and may have been shed from the uplift during late stage adjustments. There is no visible central topographic peak of uplifted bedrock at Haughton but studies of the post‐impact Haughton Formation suggest that the center of the structure subsided 300–350 m soon after formation. Breccia studies also indicate the occurrence of shock‐melted sediments, including shales, but no evidence of shock melted carbonates, the most common target lithology. This may be ascribed to the ease with which carbonates are volatilized by relatively moderate shock levels. The large amount of volatiles released on impact helped disperse the highly shocked products leading to the formation of a relatively cool clastic and polymict breccia deposit in the interior, as opposed to a coherent melt sheet. In this regard, the breccia deposit is somewhat analogous to the suevite deposits within the Ries crater. Sedimentological studies indicate that the Cretaceous‐age Eureka Sound Formation was present at the time of impact and that the Haughton area has undergone as much as 200 m of erosion since the time of impact.

The Stratigraphy, Sedimentology, and Fossils of the Haughton Formation: A Post‐Impact Crater‐Fill, Devon Island, N.W.T., Canada

Abstract—After the impact that formed Haughton crater, 22.4 ± 1.4 Ma ago (early Miocene), the cavity filled with water and began to accumulate lacustrine sediments. These preserve detailed evidence of pre‐impact stratigraphy and post‐impact morphology and development of the crater, as well as of the climatic and biotic regime in which it lay. In this report we formally designate these sediments as the Haughton Formation, of which only a 48 m thick remnant covering approximately 7 km2still exists. Dolomite‐rich, poorly‐sorted silt, fine sand, and mud are the principal lithologies. The formation unconformably overlies a blanket of allochthonous impact breccia forming the floor of the original crater. Presence of a debris‐flow deposit in the base of the sequence indicates that lacustine deposition began very shortly after crater formation.The Haughton Formation contains a moderately diverse and highly endemic vertebrate fauna as well as palynomorphs and plant macrofossils that indicate a cool‐temperate climatic regime. A small percentage of reworked Late Cretaceous and early Tertiary palynomorphs point to the former existence of the Eureka Sound Formation in the drainage area of the crater. In addition, the distribution of the lake beds indicates the absence of an inner ring on the west side of the crater, and the 3° to 3.5° inward dip of Haughton strata implies that the central mass has subsided approximately 300 to 350 m since deposition began.

Organic maturity of Late Cretaceous and Tertiary coal measures, Canadian Arctic Archipelago

Maastrichtian and Lower Tertiary strata of the Eureka Sound Formation are widespread in the Canadian Arctic Archipelago and include major resources of lignite, subbituminous and high-volatile bituminous coal. The level of organic maturity of the strata for the most part reflects pre-orogenic (pre-Late Eocene-Miocene) depths of burial and thus helps define Early Tertiary depositional patterns. In the Remus Basin, in the eastern Canadian Archipelago, over 90 seams of coal occur ranging in rank from lignite (0.15% R 0 max) to high-volatile bituminous (0.70% R 0 max). The maturity values at the base of the Eureka Sound Formation, in conjunction with measured maturation gradients, indicate a maximum paleothickness of 4500 m and outline a basin with well defined eastern, western and southern margins. On the bases of numerical modeling, the maturation gradients are interpreted to reflect paleogeothermal gradients up to 55°C/km in the eastern part of the basin and of about 20°C/km in the western part. Elsewhere in the Canadian Arctic Archipelago the level of organic maturity of the Eureka Sound Formation varies from 0.15% R 0 max to 0.70% R 0 max. Maturation gradients measured from Meighen Island in the Strand Fiord Basin and from Melville Island in the southern part of the West Sverdrup Basin are about 0.10 log R 0 max/km, and when compared to numerical models suggest paleogeothermal gradients on the order of 15°C/km. At Meighen Island the paleodepth of burial of the Eureka Sound Formation may have been up to 6000 m. As a first approximation, the Melville Island gradient is considered representative of West Sverdrup and Banks Basin. Using this gradients, a paleodepth of burial of 3000 m is calculated for central West Sverdrup Basin and 4000 m for the southern part. In Banks Basin the paleodepth of burial is estimated to be on the order of 4000 m. Maturity values obtained from the Lake Hazen and Judge Dally Basins, Eclipse Trough and Somerset, Devon and Cornwallis Islands and at Bache Peninsula on eastern Ellesmere Island cannot be readily interpreted in terms of paleodepth of burial. No measured sections are thick or complete enough to establish maturation gradients, and the Tertiary history of these areas is only poorly known. The low paleogeothernal gradients calculated from Meighen Island, Melville Island and from the western part of the Remus Basin (15–20°C/km) are considered to reflect low heat flow or rapid Tertiary sedimentation and uplift such that an equilibrium geothermal gradient may never have existed. The higher maturation gradients and interpreted paleogeothermal gradients in the eastern Remus Basin are considered to be the product of higher heat flow on eastern Ellesmere Island. Anomalously high levels of maturity obtained along the Stolz Fault and adjacent Strand Fiord on Axel Heiberg Island are attributed to the thermal effects of evaporite diapirs.

A new eocene triprojectate pollen genus from the Canadian Arctic, Novemprojectus

A new triprojectate pollen genus, Novemprojectus, is described from a middle Eocene sample from the Eureka Sound Formation on Kanguk Peninsula of Axel Heiberg Island, the Canadian Arctic. The type species of the genus is Novemprojectus traversii.

New evidence for the chronology of the Eurekan Orogeny from south-central Ellesmere Island

Discovery of a post-orogenic coarse-grained sandstone and pebble- to cobble-conglomerate unit on south-central Ellesmere Island provides important new evidence for the chronology of the Eurekan Orogeny in the eastern Arctic Archipelago. Palynological studies indicate an Early Miocene age for these deposits, which rest with marked angular unconformity on mid-Paleocene strata. In adjacent areas, strata of the Eureka Sound Formation as young as Middle Eocene are folded, thereby bracketing the major orogenic phase of the Eurekan Orogeny on southern Ellesmere Island as post-Middle Eocene to pre-Early Miocene. Furthermore, the occurrence of the coarse-grained sandstone and conglomerate deposits indicates an Early Miocene phase of epeirogenic relative uplift of southeastern Ellesmere Island and possible coeval tectonism along the margin of Baffin Bay.The discovery and dating of these post-orogenic deposits provide additional chronological evidence for tectonism that constrains paleogeographic and paleo-plate reconstructions of the eastern Arctic during the Tertiary.

Variations in fluvial style in the lower Cenozoic synorogenic sediments of the Canadian Arctic Islands

The Eureka Sound Formation (Maastrichtian to Eocene or Oligocene) occupies seven intraplate basins in the Arctic Islands and equivalent beds form part of the continental-margin wedges flanking the Arctic Ocean and Baffin Bay. Shallow-marine, deltaic, fluvial and lacustrine facies are present. Fluvial assemblages can be subdivided into: (1) assemblage F: cyclic, generally fine-grained deposits with point bar crossbedding, deposited by high-sinuosity rivers; (2) assemblage G 1: noncyclic sandy sequences of Platte braided type; (3) assemblage G 2: cyclic sandy and conglomeratic assemblages of Donjek type; (4) assemblage H: laminated sandstone with minor crossbedding—ephemeral Bijou Creek or Malbaie type; and (5) assemblage J: cobble and boulder conglomerate deposited on alluvial fans—Scott type. Variations in fluvial style within and between basins are related to local tectonic and, possibly, climatic effects. Adjacent to active faults bounding two of the basins the deposits form coarsening-upward megasequences, showing transitions from assemblages E (deltaic) or F to G and H, and culminating in assemblage J. These sequences document the progradation of a braidplain and alluvial-fan complex in front of rising fault-bounded uplifts. Only at Strathcona Fiord in central Ellesmere Island does coal comprise a significant part of the formation. There the sediments also contain a rich vertebrate fauna. This and other broad facies variations may reflect local climatic differences generated by the rugged topography.

Arctic Terrestrial Biota: Paleomagnetic Evidence of Age Disparity with Mid-Northern Latitudes During the Late Cretaceous and Early Tertiary

Magnetostratigraphic correlation of the Eureka Sound Formation in the Canadian high Arctic reveals profound difference between the time of appearance of fossil land plants and vertebrates in the Arctic and in mid-northern latitudes. Latest Cretaceous plant fossils in the Arctic predate mid-latitude occurrences by as much as 18 million years, while typical Eocene vertebrate fossils appear some 2 to 4 million years early.

The Bjørnehiet Formation: a faulted preglacial conglomerate, Washington Land, North Greenland

A new occurrence of a Tertiary or Quaternary fluvial conglomerate from North Greenland is described, and named the Bjørnehiet Formation. The main lithology is a carbonate-clast, matrix-supported, oligomictic conglomerate with some coarse sandstone beds. The composite thickness of the formation is about 45 m. The conglomerate is known only from one locality in Washington Land, about 40 km from the shore of Nares Strait. The deposit has been affected by post-depositional faulting and is considered to be preglacial in age. By comparisons with Arctic Canada, the conglomerate is regarded as an equivalent of either the Palaeogene Eureka Sound Formation or the Neogene Beaufort Formation, both of which contain important fluvial conglomerate units. The conglomerate represents the only evidence of post-Palaeozoic, preglacial deposits in this part of Greenland. The occurrence is thus particularly important and provides a way of recording Cenozoic fault movements. If the deposit can be accurately dated, and when its full distribution is known, the formation and the structures affecting it will provide significant data about the Cenozoic palaeogeography and tectonics of the Nares Strait region.

Tertiary Coal Resources, Eastern Arctic Archipelago

In the eastern Canadian Arctic Archipelago major coal resources occur within the Late Cretaceous and Tertiary Eureka Sound Formation. The formation, which ranges in thickness from thin erosional outliers on central Axel Heiberg Island to a maximum thickness of 3300 m on Fosheim Peninsula, Ellesmere Island, contains numerous thick seams of coal. The coal is highly variable in quality, but seams of clean, vitrain rich coal several metres thick are present. The rank of the coal ranges from lignite through sub-bituminous to high-volatile bituminous as measured by vitrinite reflectance. Inferred resources within the area of study are calculated as 30,000 million tonnes of which 15,000 million tonnes are lignite, 11,000 million tonnes are sub-bituminous and 4000 million tonnes are high-volatile bituminous. The area encompassed only a small portion of the known outcrop area of Late Cretaceous and Tertiary coal measures in the Canadian Arctic Archipelago which indicates that considerable further resources are present.

Eocene lower vertebrates from Ellesmere Island, Canadian Arctic Archipelago

Lower vertebrates from the Early Eocene Eureka Sound Formation, Ellesmere Island, Canadian Arctic Archipelago, form a mixed aquatic—riparian—terrestrial assemblage similar to that of many North American Late Cretaceous and Paleogene continental deposits. Taxa include the bony fishes Amia and Lepisosteus, the salamander Piceoerpeton, anguid and varanid lizards and a boid snake. Turtles include two emylids, the tortoise Geochelone, and anosteirine, Trionyx s.s. and an unidentified turtle adapted for durophagy. The durophagous alligator Allognathosuchus is also present. The varanid, tortoise and alligator indicate an equable climate with winters that rarely suffered freezing temperatures. These animals (especially the varanid) have high temperature optima today. Such optima are more likely to have occurred seasonally, under present obliquity of the earth's axis, than with the low obliquity model that has been suggested by paleobotanical data. If so, these animals must have undergone periods of winter dormancy, unlike their living relatives. Zoogeographic affinities of the lower vertebrates are generally with North America although some of the taxa also occur in Palaeogene Europe; only the anosteirine turtle shows Asian affinities. Two of the taxa appear to have been endemic to the Arctic region, and the assemblages as a whole may have been part of a pan-Arctic fauna rather than resembling that of any northern continent in particular.

CLAY MINERALOGY OF THE EUREKA SOUND AND BEAUFORT FORMATIONS, AXEL HEIBERG AND WEST CENTRAL ELLESMERE ISLANDS, EASTERN CANADIAN ARCTIC ARCHIPELAGO

ABSTRACT In the Late Cretaceous and Tertiary strata of the Eureka Sound and Beaufort Formations on Axel Heiberg and west central Ellesmere Islands, kaolinite and illite are the dominant clay minerals, with minor to major amounts of smectite and random mixed-layers, and trace amounts of vermiculite and chlorite. Smectite and associated mixed-layers in the basal Eureka Sound Formation formed by in situ alteration of volcaniclastic material, whereas mixed-layers in the deltaic-alluvial deposits probably result from in situ paleosol formation. These strata are a likely source rock for the younger Tertiary and Quaternary Arctic Ocean sediments.

Mammals from the Palaeogene of the EurekaSound Formation: Ellesmere Island, Arctic Canada

The Eureka Sound Formation on EllesmereIsland, Canadian High Arctic at about 79° north latitude, has yielded mammalian assemblages of early to middle Eocene aspect. Preliminary examination has shown the presence of the orders Protuutheria, Dermoptera, Primates, Rodentia, Pantodonta, carnivores, and Perissodactyla. Associated with these mammals are a variety of lower vertebrates, including numerous fish, salamander, alligator, several kinds of turtle, lizard, snake, and several kinds of birds. The assemblages provide the first paleontological evidence of high latitude Paleogene terrestrial faunas in the Holarctic, and raise new questions about Arctic environment during the Eocene.

Implications of coalification levels, Eureka Sound Formation, northeastern Arctic Canada

The rank of coal in the Eureka Sound Formation on Ellesmere and Axel Heiberg Islands ranges from brown coal to high volatile bituminous coal, based on reflectance determinations. Reflectance values from coals adjacent to the Stolz Fault, Axel Heiberg Island, are higher than in adjacent areas and may be related to abnormally high heat flows resulting from evaporite diapirism at depth, from the effect of overthrusting, or both. Regional reflectance values indicate that there is no correlation between the degree of coalification and the age of the strata, suggesting differing depths of burial and tectonic settings. Comparison of the coalification gradient at Fosheim Peninsula, Ellesmere Island, with that of the Téjon area of California permits estimation of a geothermal gradient which can be used for calculation of preorogenic sediment thickness. Maximum temperatures derived from the degree of coalification (100 °C at Fosheim) suggest that the sediments are within the zone of initial oil maturity.

Sedimentary structures and paleocurrents in a Tertiary deltaic succession, northern Banks Basin, Arctic Canada

The Eureka Sound Formation of northern Banks Basin is a deltaic unit of Paleocene to Eocene age. A basal member of shale, approximately 100 m thick, passes vertically and, in part, laterally into a succession of sand, silt, shale, and lignitic coal approximately 1000 m thick, which is referred to as the cyclic member because of the abundance of coarsening-upward cycles, averaging 7.4 m in thickness.Sand beds in the cyclic member can be divided into four lithofacies: (1) A facires dominated by medium- to large-scale planar crossbedding, formed by channel processes, including lateral point bar accretion, in the delta plain environment. (2) A predominance of medium-scale trough and (minor) planar crossbeds, formed by migrating dunes in distributary mouth bar sands. (3) A predominance of small-scale ripple-marks, formed by low energy, unimodal currents in distal distributary mouth sands. (4) A lack of current structures, indicating quiet-water, interdeltaic and prodeltaic deposition. The distribution of these four facies outlines a series of small lobate deltas.Paleocurrent data suggest a pattern of radiating distributaries within each delta lobe. Directional variance, when analyzed at various levels of the sedimentary structure hierarchy, provides information regarding channel sinuosity and enables comparisons to be made with other deltaic deposits. High variance for the directions of the distributaries is consistent with a fluvially dominated delta.

Paleogene Terrestrial Vertebrates: Northernmost Occurrence, Ellesmere Island, Canada

Recently discovered Paleogene land vertebrates from the Eureka Sound Formation at about latitude 78 degrees north in Arctic Canada include fish, turtles, an alligatorid, and several taxa of mammals. The assemblage, which is probably early or middle Eocene in age, adds to previously known paleobotanical evidence in suggesting temperate to warm-temperate climatic conditions.

Early Tertiary species of Azolla subg. Azolla sect. Kremastospora from western and arctic Canada

Species of Azolla subg. Azolla sect. Kremastospora Jain & Hall are described from samples of Early Tertiary age from the Ravenscrag Formation of Saskatchewan, the Paskapoo Formation of Alberta, and the Eureka Sound Formation of Banks Island, District of Franklin.Section Kremastospora is restricted to include only Azolla teschiana Florschütz, A. bulbosa Snead, A. stanleyi Jain & Hall, and A. areolata n. sp. The relative phylogenetic position and stratigraphic significance of these species are discussed.

Paleontologic Evidence of Marine Sediments in the Eureka Sound Formation of Ellesmere Island, Arctic Archipelago, N.W.T., Canada

Paleontologic investigation of the early Tertiary Eureka Sound Formation on Ellesmere Island, N.W.T., demonstrates the presence of well developed marine beds in that unit, which was previously considered almost completely terrestrial. This new interpretation is based largely upon the occurrence of remains of foraminifers and fish at four localities.

New Evidence on the Palaeobiology of the Eureka Sound Formation, Arctic Canada

The Eureka Sound Formation, a thick sedimentary unit in the Canadian Arctic having a late Cretaceous and/or early Tertiary age, is known to contain plant fossils indicative of a continental origin of deposition and a relatively temperate climate. The Formation was selected for a palaeontological survey in order to determine whether it could, as suggested by distribution of fossil vertebrates in other areas and from evidence of plate tectonics, provide evidence on terrestrial migrations between North America and Europe in the Palaeogene. Fossils of plants, invertebrates and fish were found. They indicated that large parts of the Formation are marine in origin, although other parts are continental and thus could still be interpreted as representing part of a land connection between the northern landmasses.