Papers by Stephen Hasiotis
International Conference and Exhibition, Melbourne, Australia 13-16 September 2015, 2015
Geological Society of America Abstracts with Programs, 2016
Journal of Sedimentary Research, 2015
Upper Cretaceous (Santonian to late Campanian) strata from the upper 196 m at Shivugak Bluffs alo... more Upper Cretaceous (Santonian to late Campanian) strata from the upper 196 m at Shivugak Bluffs along the Colville River of northern Alaska preserve a paleopolar, fluvial-deltaic succession deposited along a prograding paleo-Arctic Ocean coastline. The uppermost lower Schrader Bluff Formation is best classified as a river-dominated delta based on muddy prodelta and delta-front deposits that contain abundant hyperpycnites, subaqueous terminal distributary channels, interdistributary bays, and mouth bars. This deltaic succession is overlain by distal distributaries and a braided fluvial system of the Prince Creek Formation. Channel measurements and paleo-discharge calculations from Prince Creek Formation distributaries indicate that rivers were the appropriate size and had the appropriate discharge to regularly produce hyperpycnites. Delta front and interdistributary bays transitioned into lakes and floodbasins on the lower delta plain, alongside distributary channels during delta lobe reorganization and abandonment. These floodbasins were subsequently transgressed and are overlain by proximal shelf and prodelta muds containing Phycosiphon. Overlying strata containing delta front, interdistributary bay, terminal distributary channel, distributary mouth bar, and distributary channel deposits signaled the reactivation of the delta lobe. Ultimately, these deltaic environments were incised into and became overlain by braided channel deposits during a marked drop in relative sea level and progradation of the fluvial system. Combining ichnologic and sedimentologic observations was critical to identify eleven distinct deltaic and continental paleoenvironments. This study documents the architecture and evolution of an ancient, high-latitude, muddy, river-dominated deltaic system and highlights the autogenic and allogenic processes preserved in the system.
Zenodo (CERN European Organization for Nuclear Research), Mar 15, 2023
Subsurface modelling of dryland fluvial-deltaic systems requires that a range of uncertainty is c... more Subsurface modelling of dryland fluvial-deltaic systems requires that a range of uncertainty is considered when determining the 2D and 3D geometry and spatial juxtaposition of facies. In dryland systems, the rivers typically flow only following seasonal rainfall events (a few weeks of the year either following cyclones or winter storms). This study investigates the impact of increasing tidal range and storm-generated flooding associated with seasonal river flashy flows and wave erosion events on the facies distribution of three deltas along the remote arid to semi-arid coast of Western Australia (Gascoyne, Ashburton, and De Grey River deltas). Facies distribution and quantitative geometric measures from element to complex scale are presented for the three systems, outlining the potential application as useful analogues for subsurface modelling of comparable ancient systems as the tidal influence increases. Quantitative data to characterize the deposits of these depositional systems are presented, including results from satellite image analysis, airborne LiDAR, drone based hi-resolution photogrammetry, automated satellite-derived bathymetry, shallow auger holes, river sediment sampling, grain-size analysis. As the deltas grow, distributary channels undergo avulsion to build new sub-areal splays and flood deposits, interacting with tidal flats on the lower delta plain, and growing mouth-bars at the delta front that become extensively reworked by tides and minor waves to build asymmetric deltas, increasing sand connectivity. Tidal reworked fine-medium sands are pumped up the distributary channels, especially in the dry seasons. Laterally, storm-wave generated beach ridges accrete up-drift from the mouth-bars and become moulded into aeolian dunes along their crests. High evaporation rates lead to high salinity in the lower delta plain lagoons and distributary channels, and at the De Grey, calcareous, brown ooids form within a vast delta-front tidal shoal attached to the mouth-bar complex, reworked into distributary channels and beach ridges.
Journal of Sedimentary Research, May 1, 2007
A neoichnological experiment using the Kenyan sand boa, Eryx colubrinus, reveals the diversity of... more A neoichnological experiment using the Kenyan sand boa, Eryx colubrinus, reveals the diversity of biogenic structures produced by sand-swimming vertebrates in unconsolidated sand. Documentation of these biogenic structures will aid in the identification and interpretation of similar ichnofossils in the geologic record and help improve paleoenvironmental and paleoecological reconstructions. Two sand boas and three sand-filled chambers containing 1-3 cm thick layers of fine-to medium-grained sand were used in this burrowing experiment. The burrowing activities of the snakes were observed over a 14day period and the chambers were photographed regularly to record sediment disturbance. Eryx colubrinus produced a number of biogenic structures including (1) cone-shaped, downward-tapering features; (2) straight, vertical tubes; (3) elongate, sinuous tunnels; (4) semicircular, concave divots; (5) downward-and upward-deflected laminae; and (6) offset laminae. These different trace morphologies are present together, forming a large compound ichnofossil resulting from locomotion, resting, and dwelling behaviors. Absent from the sand-swimming biogenic structures were active backfill features, open tunnels, and burrow linings. The recognition and interpretation of ichnofossils in the rock record of sand-swimming vertebrates requires their association with assemblages of known terrestrial body and trace fossils, rhizoliths, and pedogenic fabrics. Given the ecology of extant sand-swimming vertebrates, their biogenic structures characterize loose sediments with low interstitial moisture and environments with arid to semiarid climates. The biogenic structures produced in this experiment represent a new type of previously unrecognized biodiversity-that of sand-swimming vertebrates. In order to understand the evolution of fossorial behavior in continental vertebrates, recognition of the morphology of all types of interactions between vertebrates and the sediment must be considered.
AGU Fall Meeting Abstracts, Dec 1, 2018
GSA Annual Meeting in Indianapolis, Indiana, USA - 2018, 2018
Geological Journal, Jul 10, 2023
An unusually large exotic boulder occurs in strata close to the interfingering transition of the ... more An unusually large exotic boulder occurs in strata close to the interfingering transition of the fluvial deposits of the Lower Jurassic Kayenta Formation and aeolian deposits of the Lamb Point Tongue of the Jurassic Navajo Sandstone in Grand Staircase Escalante National Monument, Utah. This boulder is composed of a weakly bedded, pink, thrombolitic burrowed mudstone and siltstone in a carbonate mudstone matrix. Comparison with similar carbonate units of the region—interpreted as lacustrine in origin and associated with interfingering deposits of Kayenta‐Navajo strata—indicates that the strata from which the boulder originated was likely a product of wind‐blown silt deposited in carbonate mud of a shallow lake. The exotic boulder is clearly embedded in and is eroding out of mostly massive to weakly bedded Jurassic, fine‐ to medium‐grained host sandstone. Nearby, the sandstone is disrupted by soft‐sediment deformation. The upper half of the enclosing sandstone shows low‐angle cross‐stratification that abuts against the edge of the boulder, indicating that Jurassic sedimentation lapped up against the sides of the boulder. Surprisingly, the exotic boulder does not co‐occur with any other clasts of similar lithology, nor is any obvious source lithology present within the immediate area. Lake beds of similar lithology in the same region are not physically traceable to the site where the exotic boulder occurs. The exotic boulder is evidence of the dynamic processes of the Jurassic landscape. The collective characteristics of the massive sandstone with typical polygonal weathering patterns and clusters of clastic pipes in the lower host rock suggest that the exotic boulder was emplaced in one of three ways: (A) fluid overpressurization, likely triggered by strong ground motion, produced the massive and deformed sandstone host and transported the boulder upward in the subsurface; (B) the block was an erosional remnant produced by Jurassic landscape degradation; or (C) the block was transported by a hyperconcentrated overland flow.
AGU Fall Meeting Abstracts, Dec 1, 2012
AGU Fall Meeting Abstracts, Dec 1, 2017
PALAIOS, Jun 1, 2010
A systematic, semiquantitative measurement of intensity of euendolithic microbioerosion aids in u... more A systematic, semiquantitative measurement of intensity of euendolithic microbioerosion aids in understanding the interactions between microorganisms and basalt glass. These interactions are important because they occur widely in ocean basins and lead to incongruent dissolution of glass. No semiquantitative method currently exists for measuring euendolithic microbioerosion. We modify the ichnofabric index (ii of Droser and Bottjer, 1986) to the microendolithic ichnofabric index (MII), a scaleindependent, orientation-independent, semiquantitative classification scheme specifically for euendolithic microborings in volcanic glass, but applicable to any medium. Material used to develop the MII comes from the phase one core, Hawaii Scientific Drilling Project #2 well and ranges in age from ,636 to 413 ka. Microtubular features in the glass are linear or curvilinear, ,0.5-2 mm in diameter, 1 mm to .100 mm long, and originate from the margins of glass fragments found in hyaloclastites and pillow lavas. Standard categories of the ii were modified to address the circumstances of the microborings. Percent disruption of primary fabric is the basis of the MII rather than percent disruption of bedding. Six categories are used ranging from no (MII 5 1) to complete disruption (MII 5 6). Modification of the ii extends the measuring scale of bioerosion to near the minimum size range for trace fossils. By extension, MII can be used for any traces that penetrate the associated medium, from microbial borings to dinosaur footprints, if the ratio of measurement length to diameter of the traces is ,30:1.
Abstracts with programs, 2021
We report on the extraordinary occurrence of modern traces assignable to Cochlichnus, Planolites,... more We report on the extraordinary occurrence of modern traces assignable to Cochlichnus, Planolites, and Treptichnus in a high polar latitude terrestrial setting near Svea, Svalbard. Svea is an old mining community that sits at 77º45'00"N, 16º43'50"E. The coldest average daily mean temperature is approximately-17ºC from January to March. The warmest daily mean temperature ranges from 1-5ºC from June to August. The remaining months experience daily mean temperatures below freezing. Average precipitation varies between 13 mm (May) to 29 mm (March), and comes in the form of snow, ice, fog, and/or rain. The traces were discovered on near-saturated, patchy grass-covered surfaces of a glacial outwash plain during an expedition in early June 2017. They were most visible in patches of sediment between grasses that were above the very high-water table; no traces were visible in pools of water between grass patches or in large areas underwater and/or barren of vegetation. Thin, regular sinusoidal trails < 1 mm in diameter attributed to Cochlichnus were most common. No tracemaker was visible producing these traces. Thin, curvilinear to irregular trails < 1 mm in diameter attributed to Planolites were common, but not as abundant as Cochlichnus. Thin, feather-stitchlike patterns < 1 mm in diameter attributed to Treptichnus were present, but less common than the other two morphotypes. Dipertan pupae were visible producing these traces. This trace association marks the highest known latitudinal occurrence of summer-produced invertebrate behaviors for an interstadial period, which can be used to interpret potential occurrences in deep time.
GSA 2020 Connects Online, 2020
GSA 2020 Connects Online, 2020
GSA 2020 Connects Online, 2020
Abstracts with programs, 2020
GSA Annual Meeting in Phoenix, Arizona, USA - 2019, 2019
GSA Annual Meeting in Phoenix, Arizona, USA - 2019, 2019
Abstracts with programs, 2018
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Papers by Stephen Hasiotis