Physical Sciences and Mathematics Commons^™

Life On The Edge: The Cambrian Marine Realm And Oxygenation, Sara Pruss, Benjamin C. Gill

Geosciences: Faculty Publications

The beginning of the Phanerozoic saw two biological events that set the stage for all life that was to come: (a) the Cambrian Explosion (the appearance of most marine invertebrate phyla) and (b) the Great Ordovician Biodiversification Event (GOBE), the subsequent substantial accumulation of marine biodiversity. Here, we examine the current state of understanding of marine environments and ecosystems from the late Ediacaran through the Early Ordovician, which spans this biologically important interval. Through a compilation and review of the existing geochemical, mineralogical, sedimentological, and fossil records, we argue that this interval was one of sustained low and variable marine …

Interspecies Differences In Food Sources For The Tropical Callichirid Shrimp Neocallichirus Spp. On San Salvador Island, Bahamas, Koji Seike, H. Allen Curran

Geosciences: Faculty Publications

At least 4 species of callichirid shrimp coexist in the shallow marine settings of San Salvador Island, an isolated, small platform of the all-carbonates Bahama Archipelago, implying that interspecific competition or trophic niche segregation occurs between these shrimp species. Carbon and nitrogen stable isotope analyses were conducted on soft tissues of 3 callichirid species, Neocallichirus cacahuate, N. grandimana, and N. maryae, to determine the food sources for each species. These analyses revealed that the isotopic trophic niches for these 3 species do not overlap. The most important food source for all 3 species was manatee grass Syringodium filiforme …

Coral Gardens Reef, Belize: An Acropora Spp. Refugium Under Threat In A Warming World, Lisa Greer, H. Allen Curran, Karl Wirth, Robert Humston, Ginny Johnson, Lauren Mcmanus, Candice Stefanic, Tara Clark, Halard Lescinsky, Kirah Forman-Castillo

Geosciences: Faculty Publications

Live coral cover has declined precipitously on Caribbean reefs in recent decades. Acropora cervicornis coral has been particularly decimated, and few Western Atlantic Acropora spp. refugia remain. Coral Gardens, Belize, was identified in 2020 as a long-term refugium for this species. This study assesses changes in live A. cervicornis coral abundance over time at Coral Gardens to monitor the stability of A. cervicornis corals, and to explore potential threats to this important refugium. Live coral cover was documented annually from 2012– 2019 along five permanent transects. In situ sea-surface temperature data were collected at Coral Gardens throughout the study period …

Cylindrical Mega-Voids In Quaternary Aeolianites, Little Exuma Island, The Bahamas: Georadar Response, Ilya Val Buynevich, H. Allen Curran, Bosiljka Glumac, Michael Savarese, Lisa Park Boush

Geosciences: Faculty Publications

In addition to karst features, tropical carbonates contain a wide range of smaller cylindrical voids (“pipes”) attributed to bioturbation, tree molds, or dissolution, among others. During geophysical investigation of the Little Exuma Island, The Bahamas, several sites with enigmatic voids were investigated using a high-frequency ground-penetrating radar (GPR) imaging.

The aim of the paper is to assess the feasibility of GPR to detect voids within lithified Holocene calcarenites of the Hannah Bay Member

Neoichnological Framework Of Coastal Habitat Shifts Represented By Bahamian Decapod Burrows, Ilya Val Buynevich, Karen Kopcznski, Christopher Sparacio, H. Allen Curran

Geosciences: Faculty Publications

In coastal settings, the cumulative spatial and temporal impacts of burrowing, ichnofabric formation, and biodeposition by large crustaceans have been largely neglected at zoogeomorphic scales. These traces also serve as important (paleo-)environmental and (paleo)hydrologic indicators, both vertical (tidal or groundwater level) and lateral (areal wetland or basin extent). To date, 354 only few studies have addressed the comparative value of decapod ichnites generated by land crabs in carbonate settings. The aim of this paper is to introduce a general conceptual framework for burrows created by three crab species in the Bahama Archipelago, using examples from San Salvador Island.

New Advances In Long-Term Monitoring Of Storm-Deposited Boulder Ridges Along Rocky Shorelines Of San Salvador Island, Bahamas, Bosiljka Glumac, Ursula Miquel, H. Allen Curran

Geosciences: Faculty Publications

Beginning in January 2012, we have monitored two boulder ridges on San Salvador: Singer Bar Point (SBP, length ~790 m) along the reef- and lagoon-protected northern coast and The Gulf (TG, length ~460 m) on the island’s high-energy southern coast. This long-term monitoring aims at documenting changes in ridge morphology and distribution, and the direction and amount of movement of individual boulders to gain insights into the intensity and effects of storms on these coastal areas.

In the initial stage of our investigations, the largest boulders from each site were photographed, GPS-located, measured, and characterized by composition and morphology. Boulders …

Smith College Campus Ada Accessibility Report, Lily Gould, Olivia Kraft, Allison Pasbjerg, Mia Schildbach

Other Student Projects

With Smith College being a residential campus for a diverse population of students, accessibility around campus is extremely important for the wellbeing of these students. All students should have access to physically accessible paths to move around campus.

The Americans with Disabilities Act (ADA) was passed in 1990. The act addresses a wide range of topics related to accessibility, including but not limited to: physical accessibility and accessible design, equal employment opportunity, discrimination prevention, and benefits. This project focuses specifically on physical accessibility across Smith College campus. The standards referenced for the rest of this report are based on the …

Microbial Ecology Of A Shallow Alkaline Hydrothermal Vent: Strýtan Hydrothermal Field, Eyjafördur, Northern Iceland, Katrina I. Twing, L. M. Ward, Zachery K. Kane, Alexa Sanders, Roy Edward Price, H. Lizethe Pendleton, Donato Giovannelli, William J. Brazelton, Shawn E. Mcglynn

Geosciences: Faculty Publications

Strýtan Hydrothermal Field (SHF) is a submarine system located in Eyjafördur in northern Iceland composed of two main vents: Big Strýtan and Arnarnesstrýtan. The vents are shallow, ranging from 16 to 70 m water depth, and vent high pH (up to 10.2), moderate temperature (Tmax ∼70°C), anoxic, fresh fluids elevated in dissolved silica, with slightly elevated concentrations of hydrogen and methane. In contrast to other alkaline hydrothermal vents, SHF is unique because it is hosted in basalt and therefore the high pH is not created by serpentinization. While previous studies have assessed the geology and geochemistry of this site, the …

Mountain Rivers Reveal The Earthquake Hazard Of Geologic Faults In Silicon Valley, Felipe Aron, Samuel A. Johnstone, Andreas Mavrommatis, Robert Sare, Frantz Maerten, John P. Loveless, Curtis W. Baden, George E. Hilley

Geosciences: Faculty Publications

The 1989, Mw = 6.9 Loma Prieta earthquake resulted in tens of lives lost and cost California almost 3% of its gross domestic product. Despite widespread damage, the earthquake did not clearly rupture the surface, challenging the identification and characterization of these hidden hazards. Here, we show that they can be illuminated by inverting fluvial topography for slip-and moment accrual-rates—fundamental components in earthquake hazard assessments—along relief-generating geologic faults. We applied this technique to thrust faults bounding the mountains along the western side of Silicon Valley in the San Francisco Bay Area, and discovered that these structures may be capable of …

Intact Polar Brgdgts In Arctic Lake Catchments: Implications For Lipid Sources And Paleoclimate Applications, Jonathan H. Raberg, Edgart Flores, Sarah E. Crump, Greg De Wet, Nadia Dildar, Gifford H. Miller, Áslaug Geirsdóttir, Julio Sepúlveda

Geosciences: Faculty Publications

Paleotemperature histories derived from lake sediment archives provide valuable context for modern and future climate changes. Branched glycerol dialkyl glycerol tetraether (brGDGT) lipids are a valuable tool in such pursuits due to their empirical correlation with temperature and near ubiquity in nature. However, the relative contributions of terrestrial and lacustrine sources of brGDGTs to lake sediments is site-dependent and difficult to constrain. Here, we explored the potential for intact brGDGTs—the complete lipids with polar head groups (HGs) still attached—to provide insight into the sources of brGDGTs on the landscape and their contributions to the sedimentary record in a set of …

The Oldest Mineralized Bryozoan? A Possible Palaeostomate In The Lower Cambrian Of Nevada, Usa, Sara B. Pruss, Lexie Leeser, Emily F. Smith, Andrey Yu Zhuravlev, Paul D. Taylor

Geosciences: Faculty Publications

All skeletal marine invertebrate phyla appeared during the Cambrian explosion, except for Bryozoa with mineralized skeletons, which first appear in the Early Ordovician. However, the skeletal diversity of Early Ordovician bryozoans suggests a preceding interval of diversification. We report a possible earliest occurrence of palaeostomate bryozoans in limestones of the Cambrian Age 4 Harkless Formation, western United States. Following recent interpretations of the early Cambrian Protomelission as a soft-bodied bryozoan, our findings add to the evidence of early Cambrian roots for the Bryozoa. The Harkless fossils resemble some esthonioporate and cystoporate bryozoans, showing a radiating pattern of densely packed tubes …

Prolonged Drying Trend Coincident With The Demise Of Norse Settlement In Southern Greenland, Boyang Zhao, Isla S. Castañeda, Jeffrey M. Salacup, Elizabeth K. Thomas, William C. Daniels, Tobias Schneider, Gregory A. De Wet, Raymond S. Bradley

Geosciences: Faculty Publications

Declining temperature has been thought to explain the abandonment of Norse settlements, southern Greenland, in the early 15th century, although limited paleoclimate evidence is available from the inner settlement region itself. Here, we reconstruct the temperature and hydroclimate history from lake sediments at a site adjacent to a former Norse farm. We find no substantial temperature changes during the settlement period but rather that the region experienced a persistent drying trend, which peaked in the 16th century. Drier climate would have notably reduced grass production, which was essential for livestock overwintering, and this drying trend is concurrent with a Norse …

The Role Of Slow Slip Events In The Cascadia Subduction Zone Earthquake Cycle, Juliette P. Saux, Elias G. Molitors Bergman, Eileen L. Evans, John P. Loveless

Geosciences: Faculty Publications

Slow slip events (SSEs) detected on the Cascadia Subduction Zone interface at 30–50 km depth imply a release of accumulated strain. However, studies of interseismic deformation in Cascadia typically find coupling on the upper 30 km of the interface, which is generally accepted as defining the seismogenic zone. Estimates of coupling using net interseismic velocities (including SSE effects) and restricting coupling to the shallow interface may underestimate slip deficit accumulation at depths >30 km. Here, we detect reversals in GPS motion as indications of SSEs, then use SSE displacements to estimate cumulative slow slip from 2007 to 2021. We calculate …

Phototrophy And Carbon Fixation In Chlorobi Postdate The Rise Of Oxygen, L. M. Ward, Patrick M. Shih

Geosciences: Faculty Publications

While most productivity on the surface of the Earth today is fueled by oxygenic photosynthesis, for much of Earth history it is thought that anoxygenic photosynthesis—using compounds like ferrous iron or sulfide as electron donors—drove most global carbon fixation. Anoxygenic photosynthesis is still performed by diverse bacteria in niche environments today. Of these, the Chlorobi (formerly green sulfur bacteria) are often interpreted as being particularly ancient and are frequently proposed to have fueled the biosphere during late Archean and early Paleoproterozoic time before the rise of oxygenic photosynthesis. Here, we perform comparative genomic, phylogenetic, and molecular clock analyses to determine …

Sedimentary Dna And Molecular Evidence For Early Human Occupation Of The Faroe Islands, Lorelei Curtin, William J. D’Andrea, Nicholas L. Balascio, Sabrina Shirazi, Beth Shapiro, Gregory A. De Wet, Raymond S. Bradley, Jostein Bakke

Geosciences: Faculty Publications

The Faroe Islands, a North Atlantic archipelago between Norway and Iceland, were settled by Viking explorers in the mid-9th century CE. However, several indirect lines of evidence suggest earlier occupation of the Faroes by people from the British Isles. Here, we present sedimentary ancient DNA and molecular fecal biomarker evidence from a lake sediment core proximal to a prominent archaeological site in the Faroe Islands to establish the earliest date for the arrival of people in the watershed. Our results reveal an increase in fecal biomarker concentrations and the first appearance of sheep DNA at 500 CE (95% confidence interval …

Unusual Intraclast Conglomerates In A Stormy, Hot-House Lake: The Early Triassic North China Basin, Kaixuan Ji, Paul B. Wignall, Jeff Peakall, Jinnan Tong, Daoliang Chu, Sara B. Pruss

Geosciences: Faculty Publications

Early Triassic temperatures were some of the hottest of the Phanerozoic, sea-surface temperatures approached 40°C, with profound consequences for both the sedimentology and faunal distributions in the oceans. However, the impact of these temperatures in terrestrial settings is unclear. This study examines shallow lacustrine sediments from the Lower Triassic succession of North China. These consist of diverse fluvial to shallow lacustrine sandstones and also spectacular, coarse conglomerates composed of diverse, intraformational clasts reworked from the interbedded sediments. The conglomerate beds can show inverse grading and high angle, flat-pebble imbrication in their lower part and vertically orientated flat pebbles in their …

Investigating Strike-Slip Faulting Parallel To The Icelandic Plate Boundary Using Boundary Element Models, Anna E.R. Pearson, John P. Loveless

Geosciences: Faculty Publications

Most faults in Iceland strike roughly parallel to the divergent plate boundary, a part of the North American-Eurasian plate boundary, which would be expected to lead to primarily normal faulting. However, several studies have observed a significant component of rift-parallel strike-slip faulting in Iceland. To investigate these fault kinematics, we use the boundary element method to model fault slip and crustal stress patterns of the Icelandic tectonic system, including a spherical hotspot and uniaxial stress that represents rifting. On a network of faults, we estimate the slip required to relieve traction imposed by hotspot inflation and remote rifting stress and …

A New Phosphatized Ophiuroid From The Lower Triassic Of Nevada And Its Position In The Evolutionary History Of The Ophiuroidea (Echinodermata), Ben Thuy, Vivienne Maxwell, Sara B. Pruss

Geosciences: Faculty Publications

The Lower Triassic fossil record of brittle stars is relatively rich, yet most records published to date are based on poorly preserved or insufficiently known fossils. This hampers exhaustive morphological analyses, comparison with recent relatives or inclusion of Early Triassic ophiuroid taxa in phylogenetic estimates. Here, we describe a new ophiuroid from the Lower Triassic of Nevada, preserved as phosphatized skeletal parts and assigned to the new taxon Ophiosuperstes praeparvus gen. et sp. nov Maxwell, V. Pruss. S.B. This unusual preservation of the fossils allowed for acid-extraction of an entire suite of dissociated skeletal parts, including lateral arm plates, ventral …

The Sedimentary Geochemistry And Paleoenvironments Project, Úna C. Farrell, Rifaat Samawi, Savitha Anjanappa, Roman Klykov, Oyeleye O. Adeboye, Heda Agic, Anne Sofie C. Ahm, Thomas H. Boag, Fred Bowyer, Jochen J. Brocks, Tessa N. Brunoir, Donald E. Canfield, Xiaoyan Chen, Meng Cheng, Matthew O. Clarkson, Devon B. Cole, David R. Cordie, Peter W. Crockford, Huan Cui, Tais W. Dahl, Lucas D. Mouro, Keith Dewing, Stephen Q. Dornbos, Nadja Drabon, Julie A. Dumoulin, Joseph F. Emmings, Cecilia R. Endriga, Tiffani A. Fraser, Robert R. Gaines, Richard M. Gaschnig, Timothy M. Gibson, Geoffrey J. Gilleaudeau

Geosciences: Faculty Publications

No abstract provided.

A Global Set Of Subduction Zone Earthquake Scenarios And Recurrence Intervals Inferred From Geodetically Constrained Block Models Of Interseismic Coupling Distributions, Shannon E. Graham, John P. Loveless, Brendan J. Meade

Geosciences: Faculty Publications

The past 100 years have seen the occurrence of five (Formula presented.) earthquakes and 94 (Formula presented.) earthquakes. Here we assess the potential for future great earthquakes using inferences of interseismic subduction zone coupling from a global block model incorporating both tectonic plate motions and earthquake cycle effects. Interseismic earthquake cycle effects are represented using a first-order quasistatic elastic approximation and include (Formula presented.) of interacting fault system area across the globe. We use estimated spatial variations in decadal-duration coupling at 15 subduction zones and the Himalayan range front to estimate the locations and magnitudes of potential seismic events using …

Evaluating Models For Lithospheric Loss And Intraplate Volcanism Beneath The Central Appalachian Mountains, Maureen D. Long, Lara S. Wagner, Scott D. King, Rob L. Evans, Sarah E. Mazza, Joseph S. Byrnes, Elizabeth A. Johnson, Eric Kirby, Maximiliano J. Bezada, Esteban Gazel, Scott R. Miller, John C. Aragon, Shangxin Liu

Geosciences: Faculty Publications

The eastern margin of North America has been shaped by a series of tectonic events including the Paleozoic Appalachian Orogeny and the breakup of Pangea during the Mesozoic. For the past ∼200 Ma, eastern North America has been a passive continental margin; however, there is evidence in the Central Appalachian Mountains for post-rifting modification of lithospheric structure. This evidence includes two co-located pulses of magmatism that post-date the rifting event (at 152 and 47 Ma) along with low seismic velocities, high seismic attenuation, and high electrical conductivity in the upper mantle. Here, we synthesize and evaluate constraints on the lithospheric …

Tectonic Transport Directions, Shear Senses And Deformation Temperatures Indicated By Quartz C‐Axis Fabrics And Microstructures In A Nw‐Se Transect Across The Moine And Sgurr Beag Thrust Sheets, Caledonian Orogen Of Northern Scotland, Richard D. Law, J. Ryan Thigpen, Sarah E. Mazza, Calvin A. Mako, Maarten Krabbendam, Brandon M. Spencer, Kyle T. Ashley, Robin A. Strachan, Ella F. Davis

Geosciences: Faculty Publications

Moine metasedimentary rocks of northern Scotland are characterized by arcuate map patterns of mineral lineations that swing progressively clockwise from orogen‐perpendicular E‐trend-ing lineations in greenschist facies mylonites above the Moine thrust on the foreland edge of the Caledonian Orogen, to S‐trending lineations at higher structural levels and metamorphic grades in the hinterland. Quartz c‐axis fabrics measured on a west to east coast transect demonstrate that the lineations developed parallel to the maximum principal extension direction and therefore track the local tectonic transport direction. Microstructures and c‐axis fabrics document a progressive change from top to the N shearing in the hinterland …

Cenomanian–Turonian Oceanic Anoxic Event (Oae2) Imprint On The Northwestern Part Of The Adriatic Carbonate Platform And A Coeval Intra-Platform Basin (Istria And Premuda Island, Croatia), Vlatko Brčić, Bosiljka Glumac, Mihovil Brlek, Ladislav Fuček, Martina Šparica Miko

Geosciences: Faculty Publications

The Cenomanian–Turonian boundary (CTB) on the intra-Tethyan Adriatic Carbonate Platform (AdCP) is generally characterised by a transition between microbially laminated and/or bioclastic limestones to calcisphere-rich massive limestone with bioturbated intervals, organic-rich interbeds, firmgrounds, as well as neptunian dikes, carbonate turbidites, tempestites and slumped structures. Compilation of the results from two study sites in the northwestern part of the AdCP and from previous research (on Istria Peninsula and islands in the Adriatic Sea in Croatia) provides a more complete overview of geological events and paleoenvironmental conditions that transformed the formerly contiguous shallow-marine environments during this time period. For the first time, …

An Early Triassic Small Shelly Fossil-Style Assemblage From The Virgin Limestone Member, Moenkopi Formation, Western United States, Vivienne Maxwell, Ben Thuy, Sara B. Pruss

Geosciences: Faculty Publications

Small shelly fossils (SSFs) are minute fossils moulded or replaced by apatite, and less commonly, other minerals like glauconite and iron oxides. This taphonomic mode is best known from Cambrian deposits, though some occurrences occur across geological time. Instances of small shelly-style preservation were found in insoluble residues from the Lower Triassic Virgin Limestone Member exposed in southern Nevada, the western United States, a second such occurrence known from this unit. Fossil steinkerns of tiny brachiopods, echinoid spines and ophiuroids are fluorapatite, with scarce phosphatic internal moulds of bivalves and two replaced ostracods. In contrast, the crinoid ossicles, almost all …

Slip And Strain Accumulation Along The Sadie Creek Fault, Olympic Peninsula, Washington, W. Cody Duckworth, Colin B. Amos, Elizabeth R. Schermer, John P. Loveless, Tammy M. Rittenour

Geosciences: Faculty Publications

Upper-plate faulting in the Olympic Peninsula of Washington State results from relative motion of crustal blocks within the Cascadia forearc and earthquake cycle processes along the Cascadia subduction zone. We reconstruct fault slip rates since ∼14 ka on the Sadie Creek fault (SCF), north of the Olympic Mountains, using airborne lidar and field mapping of surficial deposits and landforms and optically stimulated luminescence and radiocarbon dating. The SCF is a ≥14 km-long northwest-striking, subvertical, dextral strike-slip fault with a subordinate dip-slip component. Laterally, offset debris flow channels cut into Late-Pleistocene and younger surfaces show dextral slip of 4.0–24.5 m and …

Revised Fractional Abundances And Warm-Season Temperatures Substantially Improve Brgdgt Calibrations In Lake Sediments, Jonathan H. Raberg, David J. Harning, Sarah E. Crump, Gregory De Wet, Aria Blumm, Sebastian Kopf, Áslaug Geirsdóttir, Gifford H. Miller, Julio Sepúlveda

Geosciences: Faculty Publications

Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs) …

Ancient Plant Dna Reveals High Arctic Greening During The Last Interglacial, Sarah E. Crump, Bianca Fréchette, Matthew Power, Sam Cutler, Gregory De Wet, Martha K. Raynolds, Jonathan H. Raberg, Jason P. Briner, Elizabeth K. Thomas, Julio Sepúlveda, Beth Shapiro, Michael Bunce, Gifford H. Miller

Geosciences: Faculty Publications

Summer warming is driving a greening trend across the Arctic, with the potential for large-scale amplification of climate change due to vegetation-related feedbacks [Pearson et al., Nat. Clim. Chang. (3), 673–677 (2013)]. Because observational records are sparse and temporally limited, past episodes of Arctic warming can help elucidate the magnitude of vegetation response to temperature change. The Last Interglacial ([LIG], 129,000 to 116,000 y ago) was the most recent episode of Arctic warming on par with predicted 21st century temperature change [Otto-Bliesner et al., Philos. Trans. A Math. Phys. Eng. Sci. (371), 20130097 (2013) and Post et al., Sci. Adv. …

A Reference Section For The Otavi Group (Damara Supergroup) In Eastern Kaoko Zone Near Ongongo, Namibia, P.F. Hoffman, Sara B. Pruss, C.L. Blättler, E.J. Bellefroid, B.W. Johnson

Geosciences: Faculty Publications

A reference section for the Otavi Group (Damara Supergroup) in the East Kaoko Zone near Ongongo is proposed and described. The section is easily accessible, well exposed, suitable for field excursions, and well documented in terms of carbonate lithofacies, depositional sequences and stableisotope chemostratigraphy. The late Tonian Ombombo Subgroup is 355 m thick above the basal Beesvlakte Formation, which is not included in the section due to poor outcrop and complex structure. The earlymiddle Cryogenian Abenab Subgroup is 636 m thick and the early Ediacaran Tsumeb Subgroup is 1020 m thick. While the section is complete in terms of formations …

Coral Gardens Reef, Belize: A Refugium In The Face Of Caribbean-Wide Acropora Spp. Coral Decline, Lisa Greer, Tara Clark, Tanner Waggoner, James Busch, Thomas P. Guilderson, Karl Wirth, Jian-Xin Zhao, H. Allen Curran

Geosciences: Faculty Publications

Caribbean Acropora spp. corals have undergone a decline in cover since the second half of the twentieth century. Loss of these architecturally complex and fast-growing corals has resulted in significant, cascading changes to the character, diversity, and available eco spaces of Caribbean reefs. Few thriving Acropora spp. populations exist today in the Caribbean and western North Atlantic seas, and our limited ability to access data from reefs assessed via long-term monitoring efforts means that reef scientists are challenged to determine resilience and longevity of existing Acropora spp. reefs. Here we used multiple dating methods to measure reef longevity and determine …

Controls On The Formation Of Microbially Induced Sedimentary Structures And Biotic Recovery In The Lower Triassic Of Arctic Canada, Paul B. Wignall, David P.G. Bond, Stephen E. Grasby, Sara B. Pruss, Jeffrey Peakall

Geosciences: Faculty Publications

Microbially induced sedimentary structures (MISS) are reportedly widespread in the Early Triassic and their occurrence is attributed to either the extinction of marine grazers (allowing mat preservation) during the Permo-Triassic mass extinction or the suppression of grazing due to harsh, oxygenpoor conditions in its aftermath. Here we report on the abundant occurrence of MISS in the Lower Triassic Blind Fiord Formation of the Sverdrup Basin, Arctic Canada. Sedimentological analysis shows that mid-shelf settings were dominated by deposition from cohesive sand-mud flows that produced heterolithic, rippled sandstone facies that pass down dip into laminated siltstones and ultimately basinal mudrocks. The absence …