Browsing by Author "Furlong, Carolyn M."
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Item Clinoform identification and correlation in fine‐grained sediments: a case study using the Triassic Montney Formation(2018) Playter, Tiffany; Corlett, Hilary; Konhauser, Kurt; Robbins, Leslie; Rohais, Sebastien; Crombez, Vincent; MacCormack, Kelsey; Rokosh, Dean; Prenoslo, Donald; Furlong, Carolyn M.; Pawlowicz, John; Gingras, Murray K.; Lalonde, Stefan; Lyster, Steven; Zonneveld, John-PaulStratigraphic correlation of fine-grained successions is not always straightforward. Complicating factors, such as unconformities, structural complexity, subsidence and especially minimal grain-size variation, make the application of traditional correlation methods to fine-grained successions problematic. Alternatively, the analysis of detailed geochemical data can allow for the determination of variations in sediment provenance, mineralogy, detrital flux and hydrothermal input. When compared with modelled clay input over time, these geochemical indicators can be used to determine changes in relative sea-level and palaeoclimate, allowing for the identification of clinoform surfaces. As an example, this study outlines detailed correlations of chemostratigraphic packages within the lower Triassic Montney Formation in Western Canada to demonstrate the effectiveness of chemostratigraphy in defining and correlating fine-grained clinoforms across a sedimentary basin. The data set used includes five wells and one outcrop succession, from which geochemical profiles were generated and tied directly to mineralogical data and well logs. These analyses reveal 13 distinct chemostratigraphic packages that correlate across the basin. Observed elemental and inferred mineralogical changes highlight trends in relative sea-level and palaeoclimate, as well as episodes of inferred hydrothermal input to the Montney basin. Cross-plots of La/Sm and Yb/Sm further suggest hydrothermal input as well as the scavenging of middle rare earth elements by phosphatic fish debris. Additionally, plots of La/Sm versus Yb/Sm, which show volcanic arc input within the Doig Formation, suggest an additional sediment source from the west during the Anisian. Pairing detrital and clay proxies demonstrates changes in relative sea-level and, at the Smithian/Spathian boundary, the lowest relative sea-level in the Montney Formation is observed, corresponding to a change in climate.Item Evaluating continental channel-hosted Lockeia orientation as a paleoflow indicator: insights from the Jurassic Brushy Basin Member, Western United States(2025) King, M. Ryan; Timmer, Eric R.; Furlong, Carolyn M.; Gingras, Murray K.; Hayes, Derek A.; Nadon, Gregory C.; Tweet, Justin S.; Santucci, Vincent L.Although bivalves can orient infaunal body position to current direction, trace fossils of bivalves have rarely been corroborated against paleocurrent directions determined from physical sedimentary structures. This study compares Lockeia (bivalve-generated trace fossil) orientation and length to the three-dimensional bedform cross-strata dip direction from fluvial deposits at two localities in the Late Jurassic Brushy Basin Member (Morrison Formation) of the western United States. Lockeia mean orientation at each site are comparable, but tangential, to physical sedimentary structure mean orientations. Comparing accuracy (within one standard deviation) and precision (within two standard deviations) in-context of five macroform surfaces, the Lockeia measurements are more accurate indicators of current direction than the physical sedimentary structures. Conversely, the physical sedimentary structures are more precise than the Lockeia measurements. This dissimilarity is partly a function of the variability of cross-stratum dip orientation produced by three-dimensional bedforms resultant from the tangential nature of the bedform, its preservation, and the method by which these are measured. Lockeia has greater paleocurrent representation accuracy than physical sedimentary structures since it is a linear measurement rather than a collection of measurements that can be tangential to paleoflow. Lockeia measurements show shifts vertically and laterally with macroform changes indicating potential use for identifying local changes in paleocurrent direction.Item Induced or natural? Toward rapid expert assessment, with application to the Mw 5.2 Peace River earthquake sequence(2023) Salvage, Rebecca O.; Eaton, David W.; Furlong, Carolyn M.; Dettmer, Jan; Pedersen, Per K.Based on information available at the time, several questionnaire‐based schemes have been developed to provide a qualitative assessment of whether a specific earthquake (or earthquake sequence) was likely induced by anthropogenic activities or is inferred to be natural. From a pragmatic perspective, the value of this assessment is arguably the greatest in the immediate aftermath of an event (hours to days), because it could then better serve to guide regulatory response. However, necessary information is often incomplete or uncertain, and there remains a lack of scientific consensus on the most distinctive attributes of induced (vs. natural) earthquake sequences. We present a case study of the 5.2 Peace River earthquake sequence (Alberta, Canada), evaluated using two published frameworks for origin interpretation. The Alberta Energy Regulator initially considered the sequence to be natural, but a study published ~4 mo later came to the opposite interpretation. Prior to this publication, we convened a panel of experts who completed questionnaires as set out by the frameworks; results using both schemes indicate that experts believe the sequence was likely induced. Based on these expert responses, we critically evaluate information that was available publicly in the weeks to months following the mainshock on 30 November 2022; reassess the relative importance of various components of the questionnaires from a parsimonious, rapid‐response perspective; and consider other types of information that could be critical for near‐real‐time assessment of whether an event was induced or natural.Item Locomotion traces emplaced by modern stalkless comatulid crinoids (featherstars)(2023) Myers, Reed A.; Furlong, Carolyn M.; Gingras, Murray K.; Zonneveld, John-PaulModern crinoids have the ability to use their arms to crawl along the sea floor and some are capable of swimming short distances. The first and only evidence of crinoid locomotion reported from the rock record was described from the Middle Jurassic of the Cabeço da Ladeira Lagerstätte (Portugal) resulting in description of the ichnotaxon Krinodromos bentou. Although the mechanics of crinoid movement are well documented the morphological ranges of crinoid motility tracks are unknown. This study uses observations of crinoid movement and their effects on sediment using modern comatulid crinoids to propose possible trace fossil morphologies. Using 20 experimental trials supported by photography, video analyses, 3D orthogrammetry and resin casting, the morphological ranges of crinoid motility tracks are included in five distinct morphologies attributed to ambling, crawling, walking, running, and landing/taking-off traces, the latter of which are emplaced before and after swimming. Traces produced by ambling occur as epigenic hook-shaped grooves. Crawling traces comprise closely spaced hook-shaped grooves and ridges preserved in concave and convex epirelief. Walking traces consist of semi-bilaterally symmetrical collections of three or more grooves, and associated ridges, preserved in convex and concave epirelief. Running traces consist of semi-bilaterally symmetrical collections of one to three straight to semi-sinusoidal grooves and associated ridges preserved in concave and convex epirelief. Landing/taking-off traces are mounded features preserved in convex epirelief, with grooves radiating from the center. The five trace types described in this paper provide insight into morphological features that can be associated with modern crinoid activities and used to identify crinoid trace fossils, which are rarely reported, in the rock record.