Strathcona Fiord Research Articles

Using tooth enamel microstructure to identify mammalian fossils at an Eocene Arctic forest.

Lower Eocene (Wasatchian-aged) sediments of the Margaret Formation on Ellesmere Island in Canada's High Arctic preserve evidence of a rainforest inhabited by alligators, turtles, and a diverse mammalian fauna. The mammalian fossils are fragmentary and often poorly preserved. Here, we offer an alternative method for their identification. Among the best preserved and extensive of the Eocene Arctic forests is the Strathcona Fiord Fossil Forest, which contains permineralized in situ tree stumps protruding from a prominent coal seam, but a paucity of vertebrate fossils. In 2010 and 2018, we recovered mammalian tooth fragments at the fossil forest, but they are so incomplete as to be undiagnostic by using their external morphology. We used a combination of light microscopy and SEM analysis to study the enamel microstructure of two tooth fragments from the fossil forest-NUFV2092B and 2092E. The results of our analysis indicate that NUFV2092B and 2092E have Coryphodon-enamel, which is characterized by vertical bodies that manifest as bands of nested chevrons or treelike structures visible in the tangential section under light microscopy. This enamel type is not found in other mammals known from the Arctic. Additionally, when studied under SEM, the enamel of NUFV2092B and 2092E has rounded prisms that open to one side and are surrounded by interprismatic matrix that is nearly parallel to the prisms, which also occurs in Coryphodon enamel, based on prior studies. The tooth fragments reported here, along with some poorly preserved bone fragments, thus far are the only documented vertebrate fossils from the Strathcona Fiord Fossil Forest. However, fossils of Coryphodon occur elsewhere in the Margaret Formation, so its presence at the fossil forest is not surprising. What is novel in our study is the way in which we identified the fossils using their enamel microstructure.

Was the Arctic Eocene ‘rainforest’ monsoonal? Estimates of seasonal precipitation from early Eocene megafloras from Ellesmere Island, Nunavut

The early Eocene was the warmest interval of the Cenozoic, and included within it were several hyperthermal events, with the Paleocene–Eocene Thermal Maximum (PETM) the most pronounced of these. These globally warm climates extended into the Arctic and substantive paleobotanical evidence for high Arctic precipitation (MAP > 150 cm/yr) is indicative of an Arctic rainforest, which contradicts some climate models that show low Arctic precipitation. Prior studies of Arctic early Eocene wood stable-isotope chemistry, however, have shown a summer peak in precipitation, which suggests modern analogs are best sought on the summer-wet east coast of the Asia (e.g., China, Japan, South Korea), not the winter-wet west coasts of the Pacific Northwest of North America). Furthermore, some prior modeling data suggest that highly seasonal ‘monsoon-type’ summer-wet precipitation regimes (i.e., summer:MAP > 55%) characterized certain mid and lower latitude regions in the early to mid-Eocene. Presented here is a new analysis using leaf physiognomy of 3 leaf megafloras (Split Lake, Stenkul Fiord and Strathcona Fiord) and palynofloral Bioclimatic Analysis from the Margaret Formation from Ellesmere Island, placed stratigraphically as early Eocene, possibly occurring during or following one of the early Eocene hyperthermals. These new data indicate high summer precipitation in the Arctic during the early Eocene, which in part corroborates the results from Eocene wood chemistry. Nevertheless, in contradiction to the wood analysis, monsoonal conditions are not indicated by our analysis, consistent with current modeling studies. High summer (light season) and winter (dark season) precipitation in the Eocene Arctic during hyperthermals would have contributed to regional warmth.

Climate variability in the Early Pliocene Arctic: Annually resolved evidence from stable isotope values of sub-fossil wood, Ellesmere Island, Canada

Tree-ring analyses have contributed significantly to investigations of past climate. Stable isotope climate proxies (δ 18O, δD and δ 13C values) enhance traditional ring-width data, although poor preservation of ancient wood has tended to limit development of stable isotope proxy records to the Holocene and the Late Pleistocene. Here we apply stable isotope techniques to wood that represent the remains of Mixed-Coniferous Boreal Vegetation preserved in Early Pliocene (4–5 Ma) deposits at Strathcona Fiord, Ellesmere Island, Canada (ca. 78°N). Four well-preserved tree trunks, identified through wood anatomical characteristics as Larix (larch), from this high Arctic site provide annually resolved sequences of up to 250 years from which we developed a high-resolution record of Pliocene climate. Stable oxygen isotope values, in conjunction with ring-width measurements were used to derive annually resolved temperature records for this site. Our ring-width and isotope-based reconstructions provide an annually resolved record, up to 250 years, of temperature and indicate growing season (JJ) temperatures (15.8 ± 5.0 °C) 11.8 ± 5.1 °C, and mean annual temperatures (MAT) (− 1.4 ± 4.0 °C) 18.3 ± 4.1 °C warmer than present. Estimated isotope values of precipitation of − 16.3 ± 2‰ (δ 18O) and − 150.1 ± 8.9‰ (δD) were calculated from the isotopic values of wood cellulose. Relative humidity estimated from both δ 13C and δD records ranged from 60 to 80%. Paleotemperature, source water and humidity estimates are comparable to those of a modern Boreal Forest growing ca. 15–20° south of modern Ellesmere Island.

Growth-ring analysis of Early Tertiary conifer woods from the Canadian High Arctic and its paleoclimatic interpretation

Abstract Fossil forests, where petrified stumps were preserved in growth position, have been found within Early Tertiary sediments near Strathcona Fiord, Ellesmere Island, Canadian Arctic Archipelago. These fossil forests are obvious evidence for Early Tertiary climate much warmer than that of today. We analyzed the growth rings of petrified woods from two fossil forest sites (one in middle Paleocene, and the other in late Early Eocene) to extract information on climate change. The woods consist most abundantly of Metasequoia and cf. Glyptostrobus, suggesting that these forests grew in similar environments of warm to cool temperate climates. Mean ring width, mean sensitivity and power spectrum were calculated for ring-width sequences. Although significant difference in the mean ring width between the two forests was found, a comparison with living trees suggests that the difference can be attributed to the specific difference between the forests, so that a significant climate change may not necessarily be invoked. We found little significant difference in the mean sensitivity and power spectrum between the forests, neither did we find any strong indication of periodicities. Consideration of all features suggests that there was no significant difference in climate of middle Paleocene and late Early Eocene time in the High Arctic. However, the mean ring-widths of these forests were significantly smaller than that reported for mid-Cretaceous High Arctic fossil forest.

The geology, petrography and palynology of Tertiary coals from the Eureka Sound Group at Strathcona Fiord and Bache Peninsula, Ellesmere Island, Arctic Canada

Coal seams of substantial thicknesses and lateral continuity are developed in the Expedition and Iceberg Bay Formations at Strathcona Fiord and in the Expedition Formation at Bache Peninsula. The coals are lignite/subbituminous in rank and have low to moderate sulphur and variable ash contents. At Strathcona Fiord resources have been estimated to be in the order of 1 billion tonnes, whereas at Bache Peninsula estimated resources are 100 million tonnes. The coals at Strathcona Fiord are characterized by the dominance of wood-derived macerals of the humotelinite group, whereas at Bache Peninsula the coals have high amounts of detrital macerals (humodetrinite) and also have significant amounts of inertinite macerals. Pollen and spore assemblages in coals from the Iceberg Bay Formation at Strathcona Fiord are dominated by Taxodiaceace pollen with less and variable amounts of Pinaceae pollen, pteridophyte spores and angiosperm pollen. The pollen and spore assemblages indicate a Late Paleocene-Early Eocene age of the Iceberg Bay Formation coals. The Expedition Formation coals at Bache Peninsula have in general a somewhat less diverse pollen and spore assemblage and show a larger input of fern and Sphagnum spores. The pollen and spore assemblages in Expedition Formation coals at Bache Peninsula are indicative of (Early?) Paleocene age. The depositional environment for Iceberg Bay Formation coals at Strathcona Fiord is that of a forested swamp, which formed on a broad coastal plain. At Bache Peninsula peats formed in broad valleys, in which a fluviatile-lacustrine environment of deposition prevailed. The mires were likely less forested than at Strathcona Fiord as indicated by the abundance of ferns and sphagnum spores and the very low content of wood-derived macerals of the humotelinite group. The pollen assemblages in both Expidition and Iceberg Bay Formation coals indicate a temperate climate and moderate precipitation during peat accumulation.

The first Tertiary (Paleocene) marine mollusks from the Eureka Sound Group, Ellesmere Island, Canada

The gastropodDrepanochilus pervetus(Stanton) and the bivalveCytrodaria rutupiensis(Morris) occur in the Mount Moore Formation at Strathcona Fiord, west-central Ellesmere Island, northern Canada. They are the first marine mollusks identified from the Eureka Sound Group of the Canadian arctic islands. These mollusks correlate with Paleocene faunas of the Cannonball Formation of North Dakota and South Dakota, the Prince Creek Formation of northern Alaska, the Barentsburg Formation of Svalbard, and the Thanet and Oldhaven Formations of southeastern England. These occurrences imply that the earliest Tertiary Arctic Ocean molluscan fauna was compositionally distinct from coeval faunas of the northern Atlantic Ocean.

A 50-Million-Year-Old Fossil Forest from Strathcona Fiord, Ellesmere Island, Arctic Canada: Evidence for a Warm Polar Climate

The remains of a fossil forest are buried within a sedimentary sequence of Eocene age (approximately 50 million years old) near Strathcona Fiord, Ellesmere Island. Large petrified tree stumps are preserved in their original growth positions in coals of the Eureka Sound Group, a sequence of sandstones, siltstones and coals deposited in a delta/floodplain environment. The dimensions of 83 stumps were recorded and their positions plotted on a plan of the exposed area of coal. The fossil stumps are roughly conical in shape, up to 1.8 m high and with roots spreading up to 5 m in diameter. They are closely spaced on the coal, some only 1 m spart. A density of 1 stump in 27 sq. m (367 stumps/Ha) was calculated for this forest. The stumps represent large forest trees that grew in freshwater, swampy conditions between large river channels. Their buttressed roots provided extra support in the waterlogged peats. The rivers periodically shifted their courses, flooding the forest and burying them under silts and sands. Wide growth rings in the fossil wood, in addition to evidence from associated sediments and vertebrate faunas, indicate favourable growing conditions in a mild, cool/warm temperate climate with high rainfall. Palaeolatitude studies suggest that the forest lay close to its present high-latitude position during the Euocene. Such a forest is therefore evidence that the Eocene polar climate was much warmer than today and that the trees were able to tolerate polar sunlight regime of continuous summer sunlight followed by months of winter darkness.Key words: fossil forest, Tertiary, Canadian Arctic, palaeoclimate, Ellesmere Island, petrified wood, Eureka Sound Group

Fish otoliths from the lower Tertiary of Ellesmere Island

Fish otoliths of five species are present in lower Tertiary (Paleocene to Lower Eocene) rocks at Strathcona Fiord, Ellesmere Island. Two species are new, one is conspecific with a species known from the Lower Eocene of southern England, and two remain in open nomenclature.Paleobiogeographic and other implications of the fauna are that first, there is no resemblance to central European faunas; second, there is a resemblance to northern European faunas from Great Britain and the Soviet Union, pointing to cooler climatic conditions; and third, composition of the fauna suggests the prevalence of deeper shelf conditions.

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.

The Middle-Upper Devonian clastic wedge of the Franklinian Geosyncline

ABSTRACT Middle-Upper Devonian clastic strata in the Canadian Arctic Islands are present over an area of about 200,000 sq km (75,000 sq mi) and are up to 5,000 m (16,000 ft) thick. The strata comprise a clastic wedge which was deposited in the Franklinian geosyncline prior to Late Devonian - Early Mississippian deformation. The clastic wedge is divided into eleven formations, and six facies are recognized within the strata. The formations and their facies content are: Blackley (submarine fan); Cape de Bray (marine slope); Weatherall (deltaic-marine shelf); Bird Fiord (open-marine shelf and deltaic-marine shelf); Strathcona Fiord (meandering stream); Hecla Bay (braided stream); Fram (meandering stream) (new); Hell Gate (braided stream) (new); Nordstrand Point (meandering stream) (new); Beverley Inlet (meandering stream) (new); and Parry Islands (braided stream, meandering stream and deltaic-marine shelf) (new). Mineralogy, facies distributions, paleocurrent patterns and regional geology all indicate that the source areas of the clastic strata lay to the north and east, and included the Caledonian and Pearya Mountain systems and Precambrian Shield of Greenland. Chert and rock fragments characterize detritus from the Pearya Mountains whereas detritus from the Caledonian Mountains and Precambrian Shield is characterized by a high percentage of monocrystalline quartz. Compositional variations within the clastic wedge indicate that the Pearya Mountains progressively supplied a higher proportion of the detritus throughout wedge development. Paleolatitude estimations, lithologies, fossils and clay mineralogy imply that the clastic wedge was deposited under humid tropical climatic conditions. Lithologic variations in fluvial strata suggest that the climate fluctuated between savanna and very humid. Clastic deposition commenced in the extreme northeast in Eifelian time, and a coastal plain prograded south and west until it covered almost the entire Arctic Islands area by Middle Frasnian. During progradation, submarine fan and marine slope deposits infilled deep basins in the northwest. In Late Frasnian the entire area was uplifted and subjected to erosion. The area was transgressed in latest Frasnian, and a marine shelf was widespread by Early Famennian. In latest Devonian or Early Mississippian the clastic wedge was uplifted and folded to form a foothills belt bordering the Pearya Mountains. Sandstone units of delta-front, beach and distributary-channel origin within the Weatherall and Bird Fiord Fms are rated as having the highest potential for petroleum accumulations. The strata may have uranium potential but the meagre data at present available in this regard are not encouraging. End_Page 488------------------------