Recent Submissions

  • The hydrological and limnological characterization of two Canadian water catchments sensitive to anthropogenic influences: Crawford Lake, Ontario and Old Crow Flats, Yukon

    Llew-Williams, Brendan; Department of Earth Sciences
    Crawford Lake, Ontario, and Old Crow Flats, Yukon, provide two unique locations to study interacting hydrological components and the effects of climate and anthropogenically- induced landscape changes on local hydrology, geochemistry, and limnology. Crawford Lake is a small meromictic lake near the Niagara Escarpment, whose bathymetry and wind-protected shores impede seasonal turnover, maintaining density stratification across the chemocline. Chemical and isotopic analysis identified a dense, highly conductive groundwater-fed monimolimnion permanently isolated from a less dense, more dilute mixolimnion. High concentrations of dissolved oxygen were measured in the monimolimnion year-round, with oxic conditions maintained by groundwater seeping through hydraulically conductive units in Silurian dolostones of the Lockport Group. This hydrologic setting facilitates the accumulation of varves below the chemocline where the lack of bioturbation is attributed to the saline, alkaline, and isolated nature of the monimolimnion, allowing the undisturbed laminations to provide an annually resolvable chronology of local and global anthropogenic impact. The Old Crow Flats (OCF) is a remote Arctic wetland that holds over 8700 shallow thermokarst lakes and drain a 14,000 km2 headwater basin via the Old Crow– Porcupine – Yukon River system. OCF is the traditional territory of the Vuntut Gwitchin First Nations who have observed widespread climate-induced landscape changes, including shoreline permafrost slumping, rapid thermokarst lake drainage, shrub encroachment, water level changes, and forest fires. Long-term analysis (2007 –2009 and 2015 – 2019 CE) of the hydrological response to these landscape changes have shown trends of increasing connectivity between the perched lakes and incised rivers, increased seasonal runoff contributions, and altered water chemistry. Analysis of geochemical records sampled from 24 river stations allowed for the rapidly changing contributions of the hydrological endmembers over time (including precipitation, permafrost thaw, lake water, etc.) to be tracked and cross-referenced with the observed climate-induced landscape changes and regional headwater geology.
  • Paleoceanography across the Pliocene–Pleistocene transition in the southern Bering Sea: dinoflagellate cysts and acritarchs from IODP Site U1341

    Haj Soltan, Farzaneh; Department of Earth Sciences
    The latest Pliocene–earliest Pleistocene (2.828 Ma to 2.401 Ma) interval from Integrated Ocean Drilling Program Site U1341, Bowers Ridge, southern Bering Sea, northern North Pacific has been analyzed for dinoflagellate cysts, acritarchs and other palynomorphs. Based on 86 samples, with a spacing equivalent to between 500 and 6000 years, this is the most stratigraphically detailed late Cenozoic marine palynological study yet undertaken in the Bering Sea. The dinoflagellate cyst assemblages are characterized by low taxonomic richness: round brown cysts including Brigantedinium simplex, Lejeunecysta cinctoria, L. fallax, Selenopemphix nephroides, and Trinovantedinium variabile (heterotrophic taxa), and Nematosphaeropsis labyrinthus, Impagidinium cf. japonicum, and Impagidinum spp. indet. (phototrophic taxa). Marine acritarchs are represented by Cymatiosphaera? icenorum and abundant C.? invaginata. Two informal assemblage biozones and their subzones are proposed: biozone MP-A (~2.828 Ma to 2.497 Ma) and biozone MP-B (~2.477–2.401 Ma). The co-dominance of round brown cysts and the extinct high-latitude acritarch Cymatiosphaera? invaginata in biozone MP-A reflects predominantly cold and reduced-salinity surface waters with intermittent incursions of warm and higher salinity waters from the Alaskan Stream. Neither the intensification of northern hemisphere glaciation at 2.7 Ma nor intense glaciation at 2.6 Ma are clearly represented within biozone MP-A, reflecting the enclosed nature of the Bering Sea and low taxonomic richness of the marine palynomorph record. However, the MP-A/ MP-B biozone boundary at 2.47 Ma marks a major change in the hydrography of the Bering Sea, as expressed by an abrupt decline in Cymatiosphaera? invaginata and increased percentages of fresh-water algae and terrestrial plant matter, all suggesting an important increase in the influence of river discharge at Site U1341. The reduced salinity might have largely excluded Cymatiosphaera? invaginata. Biological productivity during the summer months was nonetheless sustained or even elevated judging from the relatively high concentrations of round brown cysts and invertebrate fragments throughout biozone MP-B. Sporadic incursions of the Alaska Stream continued during this time. The overall conclusions of the present study compare favourably with published interpretations based on diatoms, although the major hydrographic change at 2.47 Ma has not yet been detected in other studies of the Bering Sea.
  • The utilisation of coprophilous fungal spores for discerning late Quaternary megaherbivore extinctions in Canada

    Cocker, Scott; Department of Earth Sciences
    Northern ecosystems are experiencing dramatic changes due to anthropogenically accelerated climatic warming. Understanding the impacts of this on fauna and flora is key to predicting the long-term sustainability of northern environments. This requires long-term data sets of ecosystem response to environmental change from environments and climates contiguous to contemporary conditions. One event is the climatic warming recorded at the Pleistocene- Holocene transition that resulted in the extinction of 35 megafaunal genera and loss of the mammoth steppe biome in East Beringia. Previous studies have relied on spatially and temporally correlating bone remains, but coprophilous fungi preserved in lake sediments have recently been used as a complimentary proxy for reconstructing megaherbivore populations. A high-resolution record spanning this transition has been reconstructed using a sediment core collected from Gravel Lake, central Yukon Territory. Pollen and coprophilous fungi were complimented by radiocarbon-dated bone remains from Alaska and Yukon Territory. Results indicate the local extirpation of megaherbivores at the beginning of the Holocene (ca. 11,000 to 10,400 cal yr BP) by a decline in coprophilous fungi and a lack of bone remains from Yukon Territory. However, skeletal records indicate the loss of mammoths and horses at ca. 13,000 cal yr BP, 2000 years prior to the fungi records. At this time, pollen assemblages from Gravel Lake indicate the last environments contiguous with the mammoth steppe from this region. The data highlight a faunal turnover at ca. 13,000 cal yr BP with the proliferation of browsing taxa, but it is still unclear why only mammoth and horse populations are lost and not other grazing taxa such as bison and muskox. A secondary study analysed remains preserved in mastodon dung dated to the marine isotope stage 5a/4 transition of Nova Scotia. Results indicate a wetland rich in charophytes, sedges, cattails, bulrushes and bryophytes in a spruce-dominated boreal forest. The limited diversity and abundance of coprophilous fungi in the dung could be attributed to a browser feeding habit. If so, this could have a considerable impact on understanding the influence of feeding ecologies on the presence of coprophilous taxa in lake sediments, and thus inferences of megaherbivore abundance.
  • The hydrology of northern boreal lakes in the Taiga Shield and Plains, Northwest Territories and the importance of catchment characteristics in mediating responses to climate

    Viscek, Josef Anthony; Department of Earth Sciences
    Freshwater lakes are prominent features across northern boreal regions and are sensitive to changing climate conditions. This study, spanning the 2017-18 ice-free seasons, broadens our understanding of how variable climate and landscape conditions influence subarctic lake hydrology in the North Slave Region near Yellowknife, Northwest Territories (NT), Canada. We studied 20 lakes located within the Taiga Shield and Taiga Plains ecozones through an integrated approach, utilizing water isotope tracers (δ2H and δ18O), lake level changes, local meteorological conditions and remotely sensed catchment data. Lake water isotope data were obtained twice during the ice-free season (May and August) and evaporation/inflow (E/I) ratios were calculated to identify the relative importance of catchment hydrological controls. Hydrological data were compared to measured and modelled catchment characteristics, including relative lake/catchment size, slope, land cover and recent wildfire burn area. Overall, precipitation was a major driver of seasonal and interannual lake hydrological change, while evaporation was a major driver of summer water loss. Relative catchment size (lake area to catchment area (LA/CA)) was found to be an important driver of lake hydrology, however, this relationship is complicated by storage deficits associated with variable meteorological conditions. During wet conditions (e.g., freshet and periods of high rainfall), lakes with larger catchments (low LA/CA) had more positive water balances than lakes with high LA/CA. Under drier conditions, lake catchment size and associated fill-and-spill hydrological connectivity was reduced. Lake basins with high LA/CA (particularly those with shallower depth and greater surface area) were more prone to evaporative water loss. Lake hydrological conditions were less influenced by catchment land cover compositions, including burn area. Findings presented here highlight important drivers of lake water balances in subarctic boreal regions, which are sensitive to ongoing changes in climate. This study is part of a broader research project funded and supported by NWT Cumulative Impact Monitoring Program (CIMP), which is using a multi-proxy, paleo-ecological approach to determine long-term (i.e., 2,000 years) records of hydrology, drought, fire and water quality to inform future policy planning.
  • Assessing environmental controls for candidate microbial ichnofossils in hydrothermally altered basaltic tuffs of Upsal Hogback, NV

    Pentesco, Justin; Department of Earth Sciences
    Putative biogenic alteration has previously been identified in basaltic glass of the ocean floor, in subglacial hyaloclasts, in meteorite impact glass, and more recently in tuff erupted in a lacustrine environment. Documentation of putative biogenic alteration and characterization of the environments in which they have formed improves understanding of the thermophilic chemotrophic euendoliths to which the ichnofossils are attributed, which may enhance humankind’s understanding of the origins of life on Earth and potential evidence of life elsewhere. Upsal Hogback is a series of monogenetic tuff rings in the topographic low of the Carson Sink in the Lahontan Basin in Western Nevada. These tuff rings erupted into pluvial Lake Lahontan between 19 ka and 33.7 ka. Tufas emplaced on the tuff rings are especially abundant at two elevation intervals, which can be correlated to stillstands of Lake Lahontan, providing the minimum age constraint for the emplacement of Upsal Hogback. Chemical analysis of basalts from each ring indicates a common magmatic source that was likely affected by fractional crystallization of olivine and plagioclase as the rings erupted from north to south. In basaltic tuff of Upsal Hogback, petrographic analysis has revealed the presence of putatively biogenic alteration textures in association with palagonite, calcite, and zeolites. Tuff samples with the most abundant putative biogenic alteration are those from the interior of the tufas. Biogenic origin of the textures is indicated by their size, the log-normal distribution of their sizes, and the complex morphology which cannot readily be explained by known abiogenic processes. Measurement of palagonitization and consideration of zeolite assemblage indicates a hydrothermal fluid of sustained temperature between 40°C and 60°C. Upsal Hogback’s autochthonous carbonates, basaltic tuff, palagonitization, and the emplacement of the tuff rings in an alkaline lake may make it a good analogue for the Mars 2020 landing site in Jezero crater, Mars. The geologic characteristics of Upsal Hogback, including the hydrothermal regime, together with the early stage of putative biogenic alteration identified, provide an instructive example for future work investigating terrestrial and extraterrestrial environments for evidence of life.
  • Microplastics and microfibres in the municipal water systems and agricultural lands of the Niagara Region, Ontario

    Ham, Emily; Department of Earth Sciences
    Microplastics are ubiquitous in freshwater and terrestrial environments across the globe. Undoubtedly, plastics are entering Niagara (Ontario) water systems as well; entering as microplastics and microfibres derived from household products and materials. These microplastics are known to enter wastewater treatment plants with untreated municipal influent and exit with the treated effluent (up to 99%), making their way into water bodies where they may be taken up by aquatic organisms. Furthermore, wastewater biosolids are applied to agricultural fields as fertilizer throughout southern Ontario. Thus, microplastics may be making their way into agricultural soils where runoff can further transport these particles to downstream environments. To investigate the microplastic pathways facilitated by the wastewater treatment system to the environment, monthly effluent sampling was conducted on a local wastewater treatment plant, and monthly tap water sampling at three sites in the Niagara Region. Surface waters upstream and downstream of effluent discharge were also sampled. Wastewater effluent had an average concentration of 1.22±1.59 microplastics per litre, dominantly polyester fibres. In surface waters, greater microplastic concentrations were found downstream than upstream (3.17±2.37 and 0.35±0.33 microplastics per m3, respectively), dominantly polyethylene. In tap water, an average of 0.89 microplastics per litre was recovered (dominantly polyester). One year of monthly effluent sampling showed significant seasonal differences in microplastic concentrations, suggesting that longer studies are necessary to account for seasonal change. This study also highlights the influence of combined sewer overflows on microplastic concentrations in surface waters, which has not been thoroughly discussed in previous studies. To investigate microplastic accumulation in agricultural soils in Niagara, two receiving biosolid application and one control site were investigated. An average concentration of 4.4±4.8 and 4.3±2.4 microplastics per gram was found in soils and biosolids, respectively. Controlled-release plastic fertilizer coatings were found to be a dominant source of microplastics to agricultural soils. This study is the first to our knowledge to highlight the accumulation of polymeric fertilizer coatings in agricultural soils.
  • A Structural Analysis of Smooth-Topped Chaotic Terrains in Southern Circum-Chryse, Mars

    Walmsley, Jonathan; Department of Earth Sciences
    The presence of large outflow channels on Mars shows the importance of water in shaping the surface of the planet over geologic time. Chaotic terrain has been identified as the source region for flood waters responsible for carving out many of these channels. There are still many unanswered questions regarding chaotic terrains on Mars. Using the most up to date CTX, HRSC, and MOLA coverage, DEM and TIN models were used to investigate examples of smooth-topped chaotic terrains which include Hydraotes Chaos, a crater pair in Hydraspis Chaos, Baetis Chaos, and Candor Chaos, all south of Chryse Planitia. The findings of this study suggest that the collapse of chaotic terrains is not regionally controlled. This study also suggests that the largest chaotic terrains do not require external heat sources to form. Finally, there is evidence that chaotic terrain forming events have occurred from the Middle Noachian to the Late Hesperian/Early Amazonian.

    Pilkington, Paul; Department of Earth Sciences
    Anthropogenic activities can speed up eutrophication by increasing the rate of nutrient influx into lakes. Climate change threatens the health of freshwater ecosystems, increasing the frequency and intensity of harmful algal blooms and associated anoxia. The acid-resistant remains of freshwater algae and cyanobacteria commonly found in palynological macerations remain underutilized, even though their fossil record extends back to the Precambrian. Comparing algal palynomorph assemblages in sediments deposited in two meromictic lakes in northeastern Massachusetts illustrated their response to different stressors over the last few centuries. The abundance and diversity of algal palynomorphs increased as nutrient influx to both Sluice and Walden Pond increased with land clearing by European colonists, recorded by an increase in Ambrosia and other non-arboreal pollen in the same slides. As the City of Lynn became heavily industrialized, Sluice Pond received a lot of effluent, and algal palynomorph diversity declined sharply. Walden Pond remained recreational and primarily impacted by summer day-visitors, so a diverse dinoflagellate cyst assemblage together with planktonic colonial cyanophytes and chlorophytes persisted until major fires occurred in Walden Woods in the early 20th century. The different types of land-use between the two sites were hypothesized to be the driving factor that determines algal palynomorph assemblages. Sediments deposited since the mid-20th century at both sites contain abundant green algal palynomorphs, an observation noted in several other studies world-wide. The observed rise of the green algae at two different sites is likely attributed to increasing atmospheric CO2 and the Great Acceleration. This might be a useful auxiliary proxy marking the proposed Anthropocene Epoch, but further research is needed to better understand the taxonomy and taphonomy of algal palynomorphs, with a focus on green algae and cyanobacteria, to improve their utility as biomonitors and paleolimnological proxies.
  • In the Eyes of a Rover: An Educational Game Exploring the Ubehebe Volcanic Craters, Death Valley California, which Mimics the Traverse of a Rover

    Williams, Aileen; Department of Earth Sciences
    The game application, Hebebot: A Martian Expedition through a Terrestrial Analog, was developed for high school students and first year university/college students to promote planetary science, using analyzed data from the Ubehebe Volcanic Field in Death Valley, California. The Ubehebe Volcanic Field are hydrovolcanic landforms created by phreatomagmatic eruptions, which formed a series of maars, which last erupted in the Holocene. The Ubehebe craters are circular depressions, which resembles the crater rich landscape of Mars. The game illustrates how scientists interpret geologic features on Mars by using the techniques and theories used to interpret geologic features on Earth through analog sites. Maar craters resemble impact craters as both are open depressions below the ground surface. The objective of the game is to assist the student participants to identify the origin of the craters, whether they are volcanic or impact. The student participants identified the craters as maars. Photographic images including panoramas and MAHLI images, geochemical analysis- XRF, and petrographic images used to develop the game proved that the craters are maars formed by phreatomagmatic explosions.
  • North Gale Landform and the Volcanic Sources of Sediment in Gale Crater Mars

    Churchill, Jeffrey; Department of Earth Sciences
    An investigation into the origins of a previously unidentified landform north of Gale Crater, Mars (North Gale Landform, NGL) using remotely sensed datasets and morphological mapping has determined that it is a volcanic construct that collapsed and produced a hummocky terrain deposit to the south. Volcaniclastic sediments have been detected in the sedimentary rocks of Gale Crater by APXS. They can be grouped into distinct classes: Jake_M and Bathurst_Inlet. Jake_M are float rocks and cobbles made of igneous sediments with evolved, alkaline compositions and pitted, dusty surfaces. Bathurst_Inlet are least altered potassic basaltic sediments in siltstone sandstone to matrix-supported conglomerates. Simple petrologic models demonstrate there is a need for more than one distinct crystalline source. Bathurst_Inlet class targets are not mantle melts and Jake_M class targets are not differentiated from Bathurst_Inlet or Adirondack. NGL may be one source for the volcaniclastic sediments in Gale Crater.
  • Central North Atlantic paleoceanography during the Late Early Pleistocene (spanning Marine Isotope Stage 21) based on a high-resolution dinoflagellate cyst record

    Dube, Mukudzei Mswazi; Department of Earth Sciences
    A high-resolution dinoflagellate cyst record from Integrated Ocean Drilling Program Site U1313, constrained by an ultra-high resolution δ 18O record from the same sample set, is established to enhance our understanding of the paleoceanography and structure of Marine Isotope Stage (MIS) 21 in the central North Atlantic. Changes in cyst abundance, composition of cyst assemblages, and their diversity reflect major regional shifts in climate and ocean circulation for this time interval (866–814 ka). The following paleoenvironmental indicators are used: Operculodinium centrocarpum sensu Wall & Dale (North Atlantic Current), Nematosphaeropsis labyrinthus and Impagidinium pallidum (subpolar gyre), total Impagidinium species (subtropical gyre), and protoperidiniacean cysts (biological productivity). The integration of stable isotope and the generated dinoflagellate cyst data shows MIS 21 to have been climatically unstable and interrupted between 830 and 840 ka by two significant cool episodes. These are resolved using the relative abundance of cooler-water species and by tracking the abundance of O. centrocarpum. During MIS 21, Site U1313 was predominantly under the influence of the subtopical gyre until after 835 ka when the NAC was re-established until the end of MIS 21. This study also extends the stratigraphic range of Fibrocysta? fusiforma from its previously documented range top in the Lower Pleistocene at 2.3 Ma to ~812 ka in the present study. An unnamed Spiniferites species (Spiniferites sp. 1) is confined to the latest phase of MIS 22. Two unidentified acritarchs (Acritarch spp. 1 and 2) occur throughout MIS 21 and merit further investigation.
  • The Evolution Of East Candor Chasma Valles Marineris Mars Proposed Structural Collapse And Sedimentation

    Burden, Amanda; Department of Earth Sciences
    Valles Marineris (VM), Mars has a long history of sedimentary deposition. East Candor Chasma is located on the eastern flank of Valles Marineris. Previous studies of the chasma suggests a complex geological history of collapse and basin infill. Interior Layer Deposits (ILDs) in East Candor Chasma span over 475 km long, 145 km wide and range in elevation from -5.5 km to 3.5 km at datum. The ILDs can be separated into six different unit varieties-massive, thick layer unit, thin layer unit, steeply inclined unit, deformed layer unit, and thin mesa unit. The massive unit contains no visible layering and a distinct erosional style. Thick layer units are found overlying the massive unit and tend to thin upwards within the mound. The thin layer unit overlies the thick layer unit and can be observed truncating thick layering. A steeply dipping unit is anomalous and found only in one mound within the chasma. A Deformed layer unit is commonly observed along the walls of the chasma indicating post erosional slumping. A thin mesa unit is thought to be a late ash cover which conformably drapes all pre-existing geology. Unconformities are observed throughout the chasma, three occur at an elevation of ~1000 m within the thick layer unit. This indicates the chasma likely underwent multiple periods of erosion and deposition. Attitude measurements taken within the layered units of the central mounds reveal a possible secondary collapse along the north wall of the chasma. The lower stratigraphic section along the north face of the central mounds reveals dips of ~20˚, indicating that the massive unit was likely eroded prior to thick layer unit deposition. These observations can be used to interpret the geological history of East Candor Chasma. We suggest that a secondary collapse occurred along the north wall of the chasma after the massive unit was emplaced. Sedimentation and erosion continued after chasma collapse allowing for the emplacement of layer and thin mesa units. Two models for the history of East Candor Chasma are presented.
  • Atmospheric conditions during the Visean (Carboniferous), and post-depositional hydrocarbon generation in the Shubenacadie Basin, Nova Scotia

    Shaver, Kristen; Department of Earth Sciences
    Halite has become of particular interest recently due to its potential to preserve ancient air and provide the first paleoatmospheric composition data that is not reliant on proxies. As halite precipitates, fluid inclusions become trapped within the crystal structure. Some of which also capture miniscule gas bubbles of the air present during precipitation. This study presents the first results of Visean (Carboniferous) paleoatmosphere captured in the Shubenacadie Basin, Nova Scotia. To ensure the gas-hosting fluid inclusions are of primary origin, strict screening parameters must be applied. Those deemed adequate from visual and petrographic examinations, had reasonable homogenization temperatures, argon concentration between 0.8 and 1.0 mol %, contained a sum of methane and carbon dioxide below 10 mol %, and displayed minimal gas variation within samples were used for paleoatmospheric interpretation. Trace element concentrations (Mg, K, Ca) of halite were also examined to determine if they could provide further confirmation of primary origin but further work is required to determine its viability. The few halite samples that met all the screening parameters originated from the upper MacDonald Road formation and yielded an O2 window of 11 to 16 mol %. The failed samples in the upper formations contained visible and olfactible hydrocarbons while the lower formations contained elevated methane. This hydrocarbon generation is consistent with and increasing thermal alteration index with depth due to heat generated by the underlying Mississippi Valley-Type deposit in the basin.
  • Atmospheric and environmental interpretations of Early Paleozoic halite (Upper Ordovician, Hudson Bay Basin, & Upper Silurian, Michigan Basin)

    Davis, Alyssa M.; Department of Earth Sciences
    Halite sourced from Upper Ordovician strata (Red Head Rapids Formation) in the Hudson Bay Basin and Upper Silurian strata (Salina Group A-2 and B units) in the Michigan Basin was used to interpret atmospheric and environmental conditions during their respective depositional periods. Primary halite was distinguished from secondary or diagenetically altered halite using screening parameters consisting of petrography, trace element analysis, microthermometry and gas analysis of fluid inclusions. Primary halite preserves liquid and/or liquid-vapour cubic fluid inclusions within chevrons and fluid inclusion bands whereas secondary halite contains large, irregularly-shaped fluid inclusions. Petrographic analysis highlights the coexistence of primary and secondary fluid inclusions within some sample sets. Trace element analysis suggests that the deposits of the Hudson Bay and Michigan Basins were likely affected by periodic freshening that altered the trace element concentrations. Homogenization temperatures of the Upper Silurian halite range from 13.3 – 35.2°C which agree with expected paleoclimatic conditions. The contemporaneous occurrence of primary, depositional halite with secondary, diagenetic halite is noted during the crush fast scan method of gas analysis by mass spectrometry. Diagenetic influences are clearly reflected in the gas analysis results of some halite samples. In part, they reflect the influence of degradation and/or thermal maturation of organic matter and hydrocarbon migration subsequent to halite deposition. Atmospheric oxygen content in the primary halite from the Red Head Rapids Formation (Upper Ordovician) ranges from 13.5 to 19 %, whereas in the Salina Group A-2 and B units (Upper Silurian) it falls between 20 and 26 %. The measured values of atmospheric oxygen based on Upper Ordovician halite overlap with the range of oxygen modelled by Berner (2006) and Algeo & Ingall (2007), and the values of atmospheric oxygen of Upper Silurian halite correspond to values modelled by Berner (2006; 2009).
  • Western Pacific paleoceanography across the Early–Middle Pleistocene boundary (~773 ka, Marine Isotope Stage 19): Dinoflagellate cysts of the Chiba composite section, Japan.

    Balota, Eseroghene; Department of Earth Sciences
    The Chiba composite section, central Boso Peninsular, Japan, is a candidate Global Boundary Stratotype Section and Point for the Early–Middle Pleistocene Subseries boundary. This well-exposed, continuous and expanded marine silty sedimentary succession has a detailed paleomagnetic record and an ultra-high-resolution oxygen isotope stratigraphy supported by U-Pb zircon dating of the Byk-E tephra bed which occurs ~1 m below the Matuyama– Brunhes boundary. A detailed dinoflagellate cyst (dinocyst) study from late Marine Isotope Stage (MIS) 20 to late MIS 19 provides information on paleoceanographic changes in the Western Pacific Ocean between 791 and 770 ka. During Termination IX, a decrease in heterotrophic species (e.g. Brigantidinium spp., Selenopemphix nephroides) and corresponding increase in warm-water autotrophs (e.g. Spiniferites hyperacanthus/mirabilis, Spiniferites sp. 2) indicate a progressive decline in productivity corresponding to deglaciation and a transition from cold nutrient-rich waters of MIS 20 to warm conditions in MIS 19. This gradual warming is interrupted by a sudden but brief cooling at 790 ka which is also reflected in the MAT-based dinocyst sea-surface temperature (SST) for February and August. The dinocyst record shows a gradational response to the onset of MIS 19c. Abundant warm-water autotrophic dinocysts during MIS 19c reflects warm conditions and a northward shift of the warm Kuroshio current from 786 to 773 ka. The end of MIS 19c is marked by a sharp decrease in species richness and evenness, an abrupt and sustained rise to dominance of Protoceratium reticulatum, and a corresponding increase in dinocyst concentrations, indicating an increase in productivity and presaging the onset of the MIS 18 glaciation. Pollen and spore concentrations show a strong terrestrial influence during MIS 19. During the peak of MIS 19, Tsuga has low abundance while angiosperm pollen (deciduous broadleaved trees) increase significantly, which is similar to vegetation presently dominant in the northeastern part of the Japanese archipelago.

    Vargas Medina, Luis Eduardo; Department of Earth Sciences
    Valles Marineris is the largest canyonland formation known in the solar system being ~4000 km long and up to 11 km deep, it is subparallel to the Martian equator and exposes the interior of the Tharsis province. The spurs on the walls were analyzed using digital elevation models to geometrically quantify their morphology and orientation, relying on methodologies such as dip analysis, relief and curvature analysis, and attitude analysis among others. These analyses permitted the documentation of indicators of structural influence on the walls which were then classified by the morphology and the type of faults from which they originate. Anomalous Planes (APs) are planar features that dip into the walls of a chasma and appear to be pre-existing fault planes within the Tharsis province. These faults are associated with the underlying structures of the Large Wrinkle Ridges (LWRs) located on Ophir Planum. An elastic dislocation model was used to corroborate that the APs can define the geometry of the underlying structure of the LWRs. Planetary grabens can be distinguished from sapping channels using their geometries. It is proposed that the formation of Coprates Chasma was the result of four individual smaller chasmata that later joined. This work shows the tools and criteria used to demonstrate that the formation of Valles Marineris was complex as reflected in the formation of the wall morphology. It is shown that the formation of the walls was influenced by pre-existent structures and chasma producing faults.
  • Central North Atlantic (IODP Site U1313) paleoceanography based on a high-resolution dinoflagellate cyst record across the Early–Middle Pleistocene boundary (Marine Isotope Stages 20–18, ~810–741 ka)

    Abomriga, Walid; Department of Earth Sciences
    A dinoflagellate cyst (dinocyst) study of 102 samples from Integrated Ocean Drilling Program Site U1313 in the central North Atlantic Ocean represents the most detailed dinocyst record yet available for Marine Isotope Stage (MIS) 19, which spans the Lower–Middle Pleistocene boundary. A published ultra-high-resolution δ18O record constrains the study. The following paleoenvironmental indicators were among those used: Operculodinium centrocarpum sensu Wall & Dale (North Atlantic Current [NAC]), Nematosphaeropsis labyrinthus (sub-polar water masses), total Impagidinium spp. (subtropical gyre), and total protoperidiniacean cysts and total cyst concentrations (productivity indicators). Cooling just prior to Termination IX suggests a Younger-Dryas type event. An early arrival of the North Atlantic Current at ~797 ka and then warm subtropical gyre waters at 793.58 ka, presage the arrival of oligotrophic waters at 790.5 ka. The onset of peak interglacial conditions at 790.5 ka is delayed relative to the benthic δ18O signal, which has a midpoint age for Termination IX at ~793 ka, and presumably reflects the persistence of ice sheets to the north. Peak interglacial conditions terminated at 784 ka with a duration of ~6500 years. This is shorter than the 10.5–12.5 kyr extent of full interglacial conditions recorded elsewhere and based on different criteria. Dinocyst transfer functions give August sea-surface temperatures of ~20°C for peak interglacial conditions, a few degrees cooler than at present. Subpolar water masses occupied Site U1313 in late MIS 19, but at 750.89 ka (early MIS 18) a return of the North Atlantic Current was followed by further warming, with an August sea-surface temperature of 20 °C for the highest sample at 741.41 ka.
  • Detecting spatial variation in hydrology and carbon export across a lake-rich permafrost landscape, Old Crow Flats, Yukon, Canada

    Hughes, Daniel; Department of Earth Sciences
    Lake-rich permafrost landscapes are widespread across northern regions and provide refuge for abundant wildlife and resources for local communities. Evidence suggests that these landscapes are highly sensitive to changes in climate. The traditional territory of the Vuntut Gwitchin First Nation, Old Crow Flats (OCF), YK, is a vast 5600-km2 lake-rich landscape that is internationally recognized for its ecological and cultural integrity. Pronounced changes in lake and river water levels and land cover compositions have been observed during recent decades by local community members and in scientific studies. Research presented here focuses on enhancing our understanding of spatial patterns in hydrology and carbon export across OCF, using a suite of water chemistry parameters, carbon concentrations and water and carbon isotope tracers. The spatial patterns detected are providing an important reference for ongoing investigations of how changing climate and lake-rich landscapes are influencing water and carbon balances.
  • Chemostratigraphy of the Uppermost Cambrian Below the Ordovician GSSP

    Wang, Lisha; Department of Earth Sciences
    Chemostratigraphy is an important tool for correlating layered sedimentary rock successions. Preserved/near primary carbon isotope signatures in marine carbonates can provide high-resolution profiles for sedimentary sequences supplementing the need for distinguishing fossils from different depositional environments and those lacking fossil materials. The Global Boundary Stratotype Section and Point (GSSP) of the Cambrian‒Ordovician boundary is located at Green Point in the Green Point Formation of the Cow Head Group in western Newfoundland, Canada. To reconstruct a continuous and high-resolution chemostratigraphy from the Cambrian‒Ordovician boundary to the Furongian Series Stage 10, we included the δ13C results of the Green Point Formation covering the Ordovician GSSP interval (Azmy et al., 2014). The Green Point Formation through the base of Ordovician GSSP consists of alternating dark gray to black shale and thin ribbon limestone rhythmites, with few fossils. The samples are micritic limestone, dolomitic limestone, and dolostone. They were determined to be in primary to near-primary condition based on multiple screening tests. Cathodoluminescence screening reveals dull to bright luminescence of the samples indicative of good preservation for many of them. The δ13Ccarb and δ18O values of the Green Point carbonates range from -6.44‰ to +0.33‰ (VPDB) and from -8.63‰ to -5.67‰ (VPDB), respectively, with poor correlation. Mn/Sr ratios range from 0.63 to 9.82, with no correlation to δ13Ccarb, but with ratios supporting the near primary nature of the δ13C values. Carbon isotope compositions of the Green Point Formation below the Ordovician GSSP fluctuate but remaine essentially invariantly negative. The δ13C values reveal a negative excursion at and below the Cambrian‒Ordovician boundary, which may correlate with the Top of Cambrian Carbon Isotope Excursion (TOCE) and its significant negative excursion. A nadir of -6.44 ‰ at the base of the Eoconodontus conodont zone marks the proposed GSSP for the base of the Furongian Series Stage 10. The lower excursion may be correlated with the Hellnmaria-Red Tops Boundary (HERB) carbon isotope excursion found in sequences in the United States of America, Australia, and north China. Without an adequate record of conodonts, high-resolution chemostratigraphic trends of carbon isotope compositions facilitate the correlation of intercontinental and intracontinental sequences.
  • Dinoflagellate cyst stratigraphy and paleoecology of the Upper Miocene and Pliocene, Rees Borehole, Northern Belgium

    Al-Silwadi, Saif; Department of Earth Sciences
    Correlating and dating Neogene deposits along the southern margin of the North Sea Basin have historically been complicated by the fragmentary nature of the outcrops studied, the boreal aspect of the benthic foraminifera present, and scarcity of planktonic microfossils. Dinoflagellate cysts and other palynomorphs from the Rees Borehole, Campine area of northern Belgium, are therefore used to elucidate the paleoenvironmental history of the area. The borehole contains the Upper Miocene Diest and Kasterlee, mid-Pliocene Poederlee, and Pliocene Mol and Merksplas formations. For the Diest Formation, the presence of Achomosphaera andalousiensis andalousiensis, Barssidinium pliocenicum, Operculodinium? eirikianum, Operculodinium tegillatum, Selenopemphix armageddonensis and the acritarch Nannobarbophora walldalei are consistent with a late Late Miocene age. The dinoflagellate cyst assemblages of the Kasterlee Formation in the Rees borehole differ from those of the Kasterlee Formation in other areas, and are more similar to assemblages of the underlying Diest Formation. This may be explained by reworking of the Diest into the Kasterlee Formation. The Poederlee Formation assemblages include Achomosphaera andalousiensis suttonensis, Invertocysta lacrymosa, Operculodinium? eirikianum and, with the absence of Reticulatosphaera actinocoronata, Operculodinium tegillatum and Batiacasphaera minuta/micropapillata, point to a mid- to Late Pliocene age, between 3.7 and 2.7 Ma. For the first time, dinoflagellate cysts were found in the Merksplas Formation, indicating a marine influence. The presence of Achomosphaera andalousiensis suttonensis, Barssidinium pliocenicum, Capisocysta lyelli, Geonettia waltonensis, and Invertocysta lacrymosa within this formation collectively point towards a Late Pliocene age. Assemblages throughout the Rees Borehole reflect neritic deposition within a restricted marine basin under temperate climates.

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