GEOLOGY OF THE INTERMOUNTAIN WEST an open-access journal of the Utah Geological Association ISSN 2380-7601 Volume 9 2022 © 2022 Utah Geological Association. All rights reserved. For permission to copy and distribute, see the following page or visit the UGA website at www.utahgeology.org for information. Email inquiries to GIW@utahgeology.org. MICROBIALLY INDUCED SEDIMENTARY STRUCTURES AND THE PRESERVATION OF VERTEBRATE TRACKS ON THE COLORADO RIVER DELTA IN LAKE POWELL, HITE, UTAH Edward L. Simpson, Michael C. Wizevich, Dakota Pittinger, Garrett Rogers, and Kayla Lazer GEOLOGY OF THE INTERMOUNTAIN WEST an open-access journal of the Utah Geological Association ISSN 2380-7601 Production Cover Design and Desktop Publishing Douglas A. Sprinkel Cover Photograph of preserved Canada goose track preserved in pustular mat. The upper surface is treated with poly- urethane (shiny coating on surface) applied in order to facilitate sample extraction. The polyurethane shrank the pustules. Note the massive mud below the track. Scale bar in mm. i Become a member of the UGA to help support the work of the Association and receive notices for monthly meetings, annual field conferences, and new publi- cations. Annual membership is $20 and annual student membership is only $5. Visit the UGA website at www.utahgeology.org for information and membership application. The UGA board is elected annually by a voting process through UGA members. However, the UGA is a volunteer-driven organization, and we welcome your voluntary service. If you would like to participate please contact the current president or committee member corresponding with the area in which you would like to volunteer. Utah Geological Association formed in 1970 from a merger of the Utah Geological Society, founded in 1946, and the Intermountain Association of Geologists, founded in 1949. Affiliated with the American Association of Petroleum Geologists. Volume 9 2022 This is an open-access article in which the Utah Geological Association permits unrestricted use, distribution, and reproduction of text and figures that are not noted as copyrighted, provided the original author and source are credited. 2021–2022 UGA Board President John South john.south@dominionenergy.com 385.266.2113 President-Elect Rick Ford rford@weber.edu 801.915.3188 Co-Program Chair Megan Crocker meganlynncrocker@gmail.com 801.538.5290 Co-Program Chair Ben Gilder dgilder@gmail.com 337.962.8383 Treasurer Kellen Gunderson kellen@zanskar.us 801.634.9737 Secretary Eugene Syzmanski eugenes@utah.gov 801.537.3364 Past President Riley Brinkerhoff riley.brinkerhoff@gmail.com 406.839.1375 UGA Committees Environmental Affairs Craig Eaton eaton@ihi-env.com 801.633.9396 Geologic Road Sign Greg Gavin greg@loughlinwater.com 801.541.6258 Historian Paul Anderson paul@pbageo.com 801.364.6613 Outreach Greg Nielsen gnielsen@weber.edu 801.626.6394 Public Education Zach Anderson zanderson@utah.gov 801.537.3300 Matt Affolter gfl247@yahoo.com Publications Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 Publicity Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 Social/Recreation Roger Bon rogerbon@xmission.com 801.942.0533 AAPG House of Delegates 2020–2023 Term David A. Wavrek dwavrek@petroleumsystems.com 801.322.2915 State Mapping Advisory Committee UGA Representative Bill Loughlin bill@loughlinwater.com 435.649.4005 UGA Newsletter Newsletter Editor Bill Lund uga.newsletter@gmail.com 435.590.1338 UGA Website — www.utahgeology.org Webmaster Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 Earthquake Safety Committee Chair Grant Willis gwillis@utah.gov 801.537.3355 Douglas A. Sprinkel Azteca Geosolutions 801.391.1977 GIW@utahgeology.org dsprinkel@gmail.com Bart J. Kowallis Brigham Young University 801.380.2736 bkowallis@gmail.com Steven Schamel GeoX Consulting, Inc. 801.583-1146 geox-slc@comcast.net Thomas C. Chidsey, Jr. Utah Geological Survey 801.824.0738 tomchidsey@gmail.com John R. Foster Utah Field House of Natural History State Park Museum 435.789.3799 eutretauranosuchus@ gmail.com Editors GEOLOGY OF THE INTERMOUNTAIN WEST an open-access journal of the Utah Geological Association Volume 9 2022 131 ABSTRACT Microbially induced sedimentary structures (MISS) increase the preservation potential of vertebrate and invertebrate ichnofossils. The Colorado River forms a delta in Lake Powell at Hite, Utah, and the del- taic shoreline provides a natural laboratory to examine the development of MISS and their influence on vertebrate track preservation. Two types of MISS were identified: pustular and blister. Pustular MISS oc- cur in proximity to the June 2020 high water line. The pustular morphology is characterized by mm-scale small mounds, or pimple-like shapes. Field emission scanning electron microscopy (FESEM) examination identified preserved filamentous cyanobacteria intertwined with fine silt- and clay-sized sediment and well-preserved freshwater diatoms. Branta canadensis (Canada goose) tracks are well developed and they vary from single tridactyl tracks to trampled horizons. Blister MISS, in contrast to pustular MISS, are pres- ent in lower elevations, forming in deeper water, greater than 0.5 m. Blisters are mm- to cm-scale irregular mounds that consist of arching mats that are detached from the underlying sediment creating a pore space. Through time the blister mat mounds are destroyed by fragmentation due to desiccation combined with wind processes. FESEM and energy-dispersive spectroscopy system (EDS) analyses indicate the presence of filamentous cyanobacteria on the exterior and palisade Bacillus-type bacteria are in the interior of the blister arch, and gypsum crystals within the mat arch. Freshwater diatoms are present in both mat types. A single human track and multiple trackways of Canis latrans (coyote) were identified on the blister mats. Weakly impressed Canada goose tracks are present. Tracks cross cutting or modifying the pustular MISS have preserved MISS surface textures except in the heavily trampled areas, whereas tracks linked to the blister mat typically do not have preserved mat texture, and usually contain fragmented mat within the impression. Because of fluctuating lake levels and desiccation, these track types had a limited temporal window where they may be produced when moisture conditions permitted MISS development, about two months. Any vertebrates through the area out of the “track window” were not recorded in sediment and mat modification. Tracks imprinted on pustular MISS in lacustrine environments will have a high preser- vation potential if there are annual fluctuations in lake levels. Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Edward L. Simpson1, Michael C. Wizevich2, Dakota Pittinger1, 3, Garrett Rogers1, 4, and Kayla Lazer1, 5 1Department of Physical Sciences, Kutztown University, Kutztown, PA 19530; simpson@kutztown.edu 2Department of Geological Sciences, Central Connecticut State University, New Britain, CT 06050; wizevichmic@ccsu.edu 3dpitt527@live.kutztown.edu; 4groge296@live.kutztown.edu; 516klazer@gmail.com Citation for this article. Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K., 2022, Microbially induced sedimentary structures and the preservation of verte- brate tracks on the Colorado River delta in Lake Powell, Hite, Utah: Geology of the Intermountain West, v. 9, p. 131–151, https://doi.org/10.31711/giw. v9.pp131-151. © 2022 Utah Geological Association. All rights reserved. For permission to use, copy, or distribute see the preceeding page or the UGA website, www.utahgeology.org, for information. Email inquiries to GIW@utahgeology.org. 132 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 INTRODUCTION The preservation potential of vertebrate tracks has been scrutinized for well over seven decades. Nu- merous studies have demonstrated that the preserved morphology of vertebrate tracks is a function of the producer’s anatomy and behavior, coupled with the substrate condition at the time of imprinting, and any modification by post-imprint processes (Peabody 1947, 1948; Lockley, 1986, 1987, 1991a, 1991b; Lockley and Conrad, 1991; Marchetti and others, 2019a, 2019b, 2020; Cuadrado and others, 2021). The fidelity of tracks as a direct function of grain size, moisture variability, and rheology is well documented (Allen, 1989; Man- ning, 2004; Milań and others, 2004; Milań and Brom- ley, 2006; Milań and Loope, 2007; Dalman and Weems, 2013; Falkingham and Gatesy, 2014; Belvedere and oth- ers, 2017; Gatesy and Falkingham, 2017; Szewcyk and others, 2020; and many more). Post imprint processes include weathering, erosion, bioturbation, early cemen- tation, and post-depositional deformation (Laporte and Behrensmeyer, 1980; Nadon, 2001). The presence of microbially induced sedimenta- ry structures (MISS) has been invoked as a condition that increases the preservation probability of vertebrate tracks (Paik and others, 2001; Conti and others, 2005; Marty and others, 2009; Carmona and others, 2011; Carvalho and others, 2013; Dai and others, 2015; Fill- more and others, 2017; Noffke and others, 2019; Car- valho and Leonardi, 2021; Cuadrado and others, 2021). MISS both stabilize the initial track structure and may overgrow impressions protecting them from subse- quent erosional processes (Marty and others, 2009). In addition, early mineral precipitation of calcium carbon- ate (CaCO3) induced by microbial metabolic process- es (Chafetz and Buczynski, 1992; Dupraz and others, 2009; Marty and others, 2009; Cuadrado and others, 2011; Carvalho and others, 2013; Xing and others, 2015a, 2015b, 2015c) and evaporites in arid environ- ments (Lockely and Rodríguez-de la Rosa, 2009) may form during the initial stages of lithification and pro- mote track preservation. The occurrence of vertebrate tracks associated with MISS is documented from modern and ancient tid- al flats (Avanzini and others, 1997; Marty and others, 2009; Cuadrado and others, 2011; Noffke and others, 2019). In continental settings, track preservation asso- ciated with MISS has been documented from alluvial fan to fluvial systems (Carvalho and others, 2013), but rarely lacustrine settings (Lockley and Rodríguez-de la Rosa, 2009; Moratalla and others, 2017). Tracks and as- sociated MISS in modern lacustrine systems have not been scrutinized extensively. Delta-top deposits in Lake Powell, a reservoir within the Glen Canyon National Recreation Area, Utah and Arizona, provide an oppor- tunity to examine the vertical distribution of microbial mats on the shoreline, track generation linked to MISS type, and potential destruction of MISS and tracks over time (figure 1). GEOLOGIC SETTING OF LAKE POWELL After the 1963 completion of the Glen Canyon Dam (figure 1), Lake Powell levels rose until reaching a maxi- mum pool height of 1127 m elevation above sea level in 1983. This was followed by a long-term decline caused by superimposed annual drawdowns and diminished recharges from spring snowmelt combined with sum- mer monsoonal precipitation (figures 2 and 3). With the development of Lake Powell, a delta formed near the confluence of the Colorado and Dirty Devil Rivers at Hite, Utah (Pratson and others, 2008; Anderson and others, 2010; Netoff and others, 2010). Lake-level fluc- tuations over the last several years has led to repeated flooding and exposure of the delta top at Hite as well as channel incision by the Colorado River. The Hite delta has been subject to increased scruti- ny because of the focused emission of greenhouse-re- lated biological methane (CH) (Malenda and others, 2020; Waldo and others, 2021). The release of fluid and gas (CH, carbon dioxide [CO], and air) produces soft-sediment deformation escape features including domes, pockmarks, water-filled (salsas) and dry craters, sediment-filled craters, mud and sand volcanoes, clas- tic dike systems, and small-scale gas fractures (figure 4; Netoff and others, 2010; Livingston and others, 2015; Sherrod and others, 2016; Miller and others, 2018; Mal- enda and others, 2020). The uppermost 2 m of the delta consists typically of different proportions of clay, silt, and fine-sand deposits 133 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 that formed from surface runoff and/or lake-rise flood- ing (Willis, 2012; Sherrod and others, 2016). At the southern end of the Hite delta top, a topographic low is present that was periodically inundated as lake level rose during spring snow melt and spring and summer precipitation (figures 2 and 3). The ephemeral nature of the flooded area permits examination of the surface features on the delta top and enables an understanding of the sequential history of MISS and vertebrate track development (figure 3). The study area was inundated sometime in June–July 2020 (figure 3), based on the Lake Powell hydrograph and the elevation of the study area, with a gradual decline in water level that contin- ued through January 2022. METHODS The study area is located in the southern part of the exposed delta and was imaged via an unmanned aeri- al vehicle (drone). Using MetashapePro™, the photo- graphic images were compiled into a three-dimensional model of the study area (figure 2). The area examined was relatively vegetation free. Field observations of the MISS were during early June and early August of 2021. Samples of pustular mats were stabilized with poly- urethane during June 2021 to protect them from dam- age. Samples of surface fragments collected in August 2021were scraped off the top of blister sediment sur- face MISS. Both types were later analyzed in the Field Emission Scanning Electron Microscope (FESEM) at Kutztown University without additional preparation such as coating. Energy-dispersive spectroscopy system (EDS) examination determined elemental composition. Spectra were taken at 5kv and weight percent (wt.%) are adjusted using 5kv standards in the Aztec Cambridge software. DESCRIPTION OF LAKE POWELL MATS AND VERTEBRATE TRACKS Two end-member MISS morphologies were distin- guished on microbial mat cover surfaces in the study Figure 1. Location map of Lake Powell, Glen Canyon National Recreation Area, Utah and Arizona. The study area is near Hite. (A) Google Earth image of the Hite delta exposed at low water during September 2013. Box denotes study area, and enlarged in (B). Dashed-line box in (B) is approximate location of figure 2. 134 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 area, blister and pustular. Pustular MISS are present in the high elevations along the upper shoreline zone along the eastern margin of the ponded area, abutting vegetated zones (figure 2). The blister MISS are located at lower elevations (relatively deeper water) relative to the pustular mat (figure 4), continue to the west, and abut a thickly vegetated zone that does not contain mi- crobial mats. No other variety of MISS morphology was recognized. Both MISS types were dry and the upper- most half meter of deltaic sediment is cut by deep des- iccation cracks in the montmorillonite-rich clay (figure 4; Netoff and others, 2010). In the pustular MISS area, desiccation cracks are about 20 cm significantly shal- lower than in the blister mat area. Description of Pustular MISS The pustular MISS morphology is characterized by mm-scale small mounds, or pimple-like shapes, form- ing a single head on the surface (figure 5). Pustules are randomly distributed with no apparent patterning or size difference across the surface and are symmetrical to nearly symmetrical in plan view (figure 5). An individu- al pustule surface is rough and irregular textured (figure 6). Smaller forms may be superimposed on larger forms resulting in a structure that resembles a small cauliflow- er curd (figure 5). In cross section, pustular mats are less than 1 mm thick and cored with clay- to silt-size sed- iment (figure 6). White evaporite crusts are restricted to the margins of the cross-cutting desiccation cracks. No morphological differences in the pustular mats were observed between June and August 2021. FESEM examination of the pustular MISS docu- ments the presence of preserved flattened filaments (fig- ures 7A through 7D) and diatoms (figures 7E through Figure 2. Orthographic model of the study area generated from aerial drone images taken June 3, 2021. Color banding on the left model reflects surface features and probably differences in moisture content. Highlighted colors on the right model equate to the distribution of mat types. See scale on left-side model. 135 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 7G). Flat filaments are twisted and entangled around silt- to clay-size particles (figures 7A and 7B). Filaments have lengths of over 100 μm and widths of approximate- ly 2 to 3 mm. Clay particles are adhered to the filament surface. Structureless organic masses are recognizable on the filament surfaces (figure 7C). Complete to nearly complete diatoms are present and have frustule shapes varying from cylindrical, pennate, to fusiform (figures 7E through 7F). Canada goose (Branta canadensis) tracks are pre- served cross cutting the pustular MISS (figures 5 and 6). These tridactyl tracks range from single distinct tracks to heavy trampling (sensu Richter and Böhme, 2016). The pustular texture is reduced in size within the true tracks than the surrounding MISS. Tracks depress the underlying sediment surface, but under-track deforma- tional structures are not apparent due to the structure- less nature of the underlying mudstone and siltstone (figure 6). Description of Blister MISS During the June 2021 observation, the surface ex- pression of the blister MISS was represented by mm- to cm-scale irregular mounds with maximum length of about 3 cm and widths of about 1.5 cm (figure 8). Thick- ness of crust was less than 1 mm. The blister mounds were randomly distributed with no apparent patterning across the surface (figure 8). These positive structures were slightly asymmetrical with no apparent preferred orientation and arcuate to straight in planform along the crests (figure 8). The surface texture of the blisters was irregular to smooth (figures 8A and 8B). In cross sec- Figure 3. Lake Powell pool level over the past five years. Blue bar, set at study area elevation of the delta top, denotes time period that the lake level was most recently above the area. Note the 2021 reduction in water level, especially the absence of inundation of the study area that typically occurs from June through November. Data from lakepowell.water-data.com/ lakepowell/; MSL = mean sea level. 136 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 tion, the blisters have a distinct open void beneath the thin mm-thick crusts that corresponds to the overall di- mensions of each individual blister. The arch height was up to 5 mm and varies with blister size. In June 2021, numerous crusts were breached with linear and irregu- lar desiccation cracks, illustrating their void-like nature (figures 4, 5, 8, 9, and 10). The brittle, rigid nature of the microbial mat is displayed by crust fragments over- hanging the mud cracks (figure 8C). The overhanging blister MISS pieces matched across the fractured sur- faces of the desiccation cracks. Some pieces appeared to show a lineation perpendicular to the desiccation crack, suggesting ductile behavior of the mat in the early stag- es of desiccation (figure 8C). FESEM coupled with EDS examination determined the presence of gypsum crys- tals within the crusts by crystal morphology and ele- mental composition (figure 11). During the August 2021 observation period, the destruction was ubiquitous when nearly all the blisters overhanging voids were reduced to small fragments Figure 4. Field photographs of fluid/gas escape structures in the study area. (A) Drone photograph of dried salsa in northern edge of study area. Yellow arrow shows salsa in E. Red arrow marks features that are illustrated in B and D. Blue arrow shows position of filled crater/salsa. (B) Gas escape crater marked with red arrow. (C) Erupting mud volcano. Note the various age flows reflected in the different colors. Scale bar is 16.5 cm. (D) Asymmetrical gas escape crater. Yellow scale bar is 2 m. (E) Salsa with erupting gas contained in the crater. Shovel is 0.7 m (white arrow). 137 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 (compare figure 12 with figure 8). The blister mat frag- ments that originally overhung the desiccation cracks were absent (figure 12). In blister mat samples, three groupings of microfos- sils were observed under the FESEM: rods capsules, flat fibers, and diatoms (figure 13). Capsule dimensions are approximately 300 mm in length with widths of 75 mm. Capsules are clustered and commonly tightly packed with long axes nearly perpendicular to the sediment surface forming a palisade-like arrangement. Some cap- sules have up to four, node-like features (figure 13A). Rods are encrusted with sediment (figure 13B). Flat fil- aments and diatoms are noticeably less common than in the pustular MISS (compare figures 7A and 7B to figure 13G). Filaments are twisted and entangled around silt and clay particles (figure 13C). Filament lengths vary up 20 mm with widths of approximately 0.5 mm (figure 13C). Diatoms are fragmented with long axes of frag- ments in the 2 to 15 mm range. Vertebrate tracks are preserved in the blister MISS that include a human shoe print trackway, coyote (Ca- nis latrans) tracks and trackways, and Canada goose prints (figures 14A and 14B). All trackways are linear and cross-cut the blister mat. Within individual tracks, the mat texture is destroyed and in some the track tops are covered with fractured pieces of MISS indicating Figure 5. Field photographs of pustular MISS. (A) Pustular MISS with Canada goose track. (B) Enlargement and delineation by orange shading of track in A. (C) Pustular MISS. Note the size of the pustules highlighted by arrows. (D) Multiple Canada goose tracks on pustular mat. (E) Pustular MISS. Note the subcentimeter size of the pustules and white gypsum (arrow). (F) Pustular MISS cross cut by goose track. (G) Enlargement and delineation by green shading of Canada goose track in F. Use scale bar in F. Note the destruction of pustules in the track. 138 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 brittle deformation of the blister MISS surface. In Au- gust 2021 fragments on the mat surface and in tracks continued to be reduced in size. All tracks on the blis- ter mat are impressed in the underlying sediment, indi- cating the pliable character of the underlying sediment when tracks were imprinted as opposed to the brittle nature of the mats. INTERPRETATION OF PUSTULAR AND BLISTER MISS Preservation of filamentous bacteria intertwined with sediment is consistent with a MISS attribution for both the pustular and blister structures (Chafetz and Buczynski, 1992; Noffke 1999, 2009, 2010; Noffke and others, 2001, 2002, 2006; Noffke and Chafetz, 2012). Cyanobacteria, palisade Bacillus, and diatoms are a characteristic freshwater assemblage that can be found inhabiting the photic zones of lacustrine settings (Co- hen, 2003). Rods are best interpreted as Bacillus-type bacterium that form palisades – large structureless masses identified on FESEM images and are best inter- preted as extrapolymeric substance (EPS) biopolymers secreted by microorganisms. Bacterial EPS interac- tions with clay minerals can develop large structureless features that can be on the scale of 10s of mm to mm Figure 6. Photograph of preserved Canada goose track preserved in pustular mat. The upper surface is treated with polyure- thane (shiny coating on surface) applied in order to facilitate sample extraction. The polyurethane shrank the pustules. Note the massive mud below the track. Scale bar in mm. 139 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 Figure 7. FESEM images of untreated pustular MISS specimens. Scale bars are at left of the bottom data bar for each image. (A) Flat microbial fibers interlaced with silt- and clay-sized particles. Note the twisting of fibers and attached particles (ar- row). (B) Twisted flat microbial fibers interlaced with clay agglomerates (arrow). (C) Microbial sheath with extrapolymeric substance (EPS) highlighted with yellow arrow. Note the adhering clay particles highlighted with red arrows. (D) Flat twisted microbial fibers with adhering clay particles (arrows). (E) Cylindric diatoms (arrows). (F) Cylindrical diatom. 140 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 (Alimova and others, 2006). Greater abundance of cy- anobacteria in the pustular mats to that of the blister appears to be primarily ecological and may be related to light penetration of the sediment-rich water (Nofke, 2010). Diatoms are more abundant in the pustular MISS also supports ecological partitioning in the mi- crobial mats based on light penetration. Finer pustules in the impressed tracks indicate MISS recovery after imprinting. Upward arching of the sediment surface of the blisters may be the result of gas generation, probably oxygen or decay products by the bacteria being trapped under the less porous microbial mat. Oxygen buildup caused separation of the mat from the sediment surface. This mat-sediment surface separation process is com- monplace in modern ephemeral ponds characterized by filamentous bacteria (Simpson and Simpson, 2014). The upward arching permits Bacillus-type bacteria to reproduce and grow in the open space, generating the palisade structure, a morphology associated with repro- duction. Adhesion structures produced by saltating sand grains sticking to a sediment surface that is water sat- urated by capillary action are crudely similar to pus- tular MISS and can occupy similar marine- or lacus- trine-shoreline settings (Hunter, 1973; Kocurek and Fielder, 1982; Dott and others, 1986; Olsen and others, 1989; Koster and others, 1993). However, adhesion ripples are sand deposits. Sand-size grains are absent Figure 8. Field photographs of blister MISS. (A) Blister MISS with a coyote track within circle. Scale bar in cm (top) and inches. (B) Blister MISS with coyote track (circled). Scale bar in inches. (C) Blister MISS. Note the crust overhanging the desiccation crack and their adjacent symmetry across the cracks and breaching of crusts over voids highlighted by arrows. Scale bar in cm. 141 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 from the mats. In addition, adhesion structures have a distinctive asymmetrical cross section with inter- nal low-angle pseudo-cross laminations and therefore should not be confused with pustular MISS (Hunter, 1973; Kocurek and Fielder, 1982; Davies and others, 2016). Pustular MISS has been recognized throughout the rock record (Prave, 2002; Bottjer and Hagadorn, 2007; Schieber, 2007; Sheldon, 2012; Zhong-Wu and others, 2013; Kumar and Ahmad, 2014; Wilmeth and others, 2014). Simpson and others (2022) named pus- tular MISS as a trace fossil ichnospecies Pustularichnus rebeccahuntfosteri with the holotype at the Early Creta- ceous Mill Canyon Dinosaur Tracksite north of Moab, Utah, USA, where 10 distinctive vertebrate track types are recognized (Lockley and others, 2014a, 2014b). In contrast to pustular MISS, recognition of blister MISS may be problematic in the rock record as evi- denced by the blister destruction documented on the Lake Powell surface supporting their low probability of preservation. A possible equivalent example is termed “cyanobacteria-laden salt ridges” in modern interdune deposits in evaporitic settings (Fryberger and others, 1983, 1988; Simpson, 1983; Simpson and Loope, 1985). These cm-scale modern salt ridges have efflorescent crusts that are separated from the underlying sediment surface with cyanobacteria rimming the arch, gypsum or other types of evaporites present, and limited breech- ing of the crestline (Fryberger and others, 1983, 1988; Figure 9. Field photograph of a close-up view of blister surface. Breeches of blister arches are highlighted by arrows. 142 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 Simpson, 1983; Simpson and Loope, 1985). Differences between the modern salt ridges and the blister MISS in- clude (1) linear ridge morphology with evaporitic inter- dunal areas for salt ridges versus the nonlinearity shape to the blisters on Lake Powell, and (2) erosion resistance in interdunes versus erosion prone structures on Lake Powell. Simpson (1983) recognized flame-like features in excavated interdune deposits of White Sands National Park, New Mexico. These features were attributed to the burial of salt ridges indicating that longer-term preser- vation of open structures could mimic flame structures and suggests how the fragile blister MISS may look like if buried before destruction. Lockley and Rodríquez-de la Rosa (2009) recog- nized the role of wetting and drying, dissolution, cap- illary evapotranspiration, and wind deflation in the preservation of human tracks. The destruction of the blister-mat features at Lake Powell is interpreted as prolonged desiccation of the microbial mats inducing reduction in thickness by water loss. The thinning and loss of filament flexibility causes the blister structure to undergo tension on the outer surface leading to crest failure. Once breeched, wind-induced turbulence rap- idly enhances arch breakup. Wind destruction of MISS in relation to topography has been documented on tid- al flats (Bouougri and Porada, 2012) and ancient tidal flats (Noffke and others, 2019). Our observations on the delta surface indicate these newly formed fragments are mobilized by wind and gradually infill the desiccation cracks leveling the deflation surface. Destruction by wind action of the pustular mat is limited because the interior is filled with sediment as opposed to the void- like nature of blister mats. DISCUSSION Tracks in the rock record are more commonly found associated the fine-grained sediments, suggest- ing that fine-grained sediments provide better foot- print preservation. Detailed study of tracks developed in coarser-grained sediment is in its infancy (Carval- ho, 2004; Fillmore and others, 2012, 2017; Szewcy and others, 2020). MISS types and associated tracks along the Hite delta shoreline were developed in water-laden fine-grained sediment and indicate a short timeframe where conditions were amenable to track generation and preservation. In recent sediments, footprint morphology can be Figure 10. Trackways on blister MISS. Large units on scale bar are in inches. (A) Blister mat with human shoe print track- way (arrows). (B) Multiple superimposed coyote trackways (arrows) across the blistered MISS surface. (C) Isolated coyote trackway (arrows). 143 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 Figure 11. EDS spectral analysis of gypsum found in the blister MISS. The six spectral graph locations are shown on the electron image at the top. Note the presence of Ca and S, indicating gypsum. Table results are in weight percent. 144 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 related the microbial mat thickness and water content of the mat and underlying sediment (Marty and oth- ers, 2009). Microbial mats are generally only produced during wet conditions, restricting the timeframe during which footprints are registered/preserved (Marty and others, 2009). Generally, poorly defined footprints or no footprints at all form on dry mats, whereas imprints are sharp in water-saturated mats, and may have associ- ated well-defined displacement rims (Marty and others, 2009). In addition, Cuadrado and others (2011) noted that examining recent tidal flats over a period of time, dried mats only have tracks that were poorly preserved or significantly modified to be unrecognizable. Mi- crobial mats can form a low-permeability layer, which separates the sediment beneath from the atmosphere insulating against water loss; as a result, the sediment below is wet or moist and not necessarily as dry as the overlying mat (Porada and others, 2007). These observations permit the interpretation of mat and sediment conditions at the time of track imprint- ing at Lake Powell. Pustular MISS were imprinted with tracks and enough time passed to allow the mat to re- cover but the underlying sediment remained plastical- ly deformed and hence did not recover to its original shape. In the blister MISS area well-preserved tracks display both a destroyed mat texture and mat fragments resting in the track indicating two different sets of phys- ical conditions for the track generation. Coyote tracks and trackways were generated when both the mat and underlying sediment where wet or moist, allowing for plastic deformation of both the mat and sediment. The human tracks were made during a time period when the blister MISS was dry enough to fracture under the foot pressure and sediment was moist enough to plas- Figure 12. August 2021 field photographs of blister mats after partial destruction. A and B Eroded blistered MISS. Note the sediment “small flakes” of earlier blister structures (arrows) and the absence of crust overhanging the mud cracks. Scale bar in cm. 145 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 Figure 13. FESEM images of microbes in blister mats. Scale bars are at the left of the bottom data bar for each image. (A) Clustered ovate capsules on the underside of sediment crust. (B) Cross section through blister MISS. Note fine silt and clays attached to the outer surface. Upper surface is to the left. (C) Close-up of aligned capsules in clusters. Note parallel alignment. (D) Capsule with four node-like features (arrow). (E) Enlargement of capsule. (F) Flat fibers (yellow arrow) with gypsum evaporite in the background (red arrow). 146 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 tically deform. Since these blister mats are subjected to extensive destruction by desiccation and wind erosion, they may not be recognizable as a mechanism that en- hances track preservation in the rock record. These MISS and sediment deformation observations and inferred conditions indicate that the Lake Powell track types had a limited window for the development of the well-preserved tracks centered around the June– August 2020 time period, as water level peaked and dropped enough and dried after in the arid setting. Pus- tular MISS tracks formed near the high-water setting, with temporally equivalent blister MISS submerged. The blister MISS exposure was followed “quickly” by transverse track formation. Vertebrates that traversed the depression area out of the “track production win- dow” of approximately two months, were not record- ed in sediment or mat modification. In addition, the high-yield strength of the mat and underlying sediment may not have permitted the development of tracks from smaller fauna biasing the record towards larger fauna (Lockley and Hunt, 1995; Noffke and others, 2019) Thulborn (1990) showed that footprints are most Figure 14. Field photographs of tracks in the blister MISS. (A) Weakly impressed Canada goose track (circle). (B) Isolated coyote track. Note the absence of broken fragments and similar coloration as to the associated mat (circle). (C) Human boot print. Note the fractured pieces of mat in the track (circle) and the well preserved tread lugs. Compare this style of preser- vation with that of B, brittle versus ductile behavior of mat deformation. (D) Human boot print with brittle fragments in the track (circle). Scales is in inches and centimeters. 147 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 commonly preserved in depositional settings in which cyclic accumulation of sediments takes place. Rapid covering of tracks of sediment and overgrowth by mi- crobial mats are significant factors increasing the poten- tial preservation of footprints (Marty and others, 2009). Lacustrine sediments are sensitive indicators of varia- tions in precipitation and snow pack in the source area on a yearly cycle (Barnett and others, 2005; Sadro and others, 2018). Lake Powell shoreline deposits are sub- jected to these types of annual lake-level fluctuations (figure 3), which would enhance the likelihood of track preservation. SUMMARY The Lake Powell deltaic shoreline at Hite is a natu- ral laboratory to unravel the development of MISS and their controls on vertebrate track preservation. Two types of MISS were present, pustular and blister. Pustu- lar MISS are restricted to the high-water line of the pon- ded area. FESEM examination identified preserved cy- anobacteria interleaved with very fine silt and clay-size grains and freshwater diatoms. Canada goose tracks are isolated and as trampled zones. Lower elevations are characterized by blister MISS and are constructed of arching mats that separated from the underlying sedi- ment by an open pore space. Ultimately over time, the blister mat arches are razed by desiccation and wind processes. FESEM and EDS indicate the presence of fil- amentous cyanobacteria, palisade Bacillus, and gypsum crystals on the mat arch of the blister. Vertebrate tracks in the blister mats consist of human and coyote track- ways that traverse the blister mats area in contrast to the tracks restricted to the pustular mat zone, which circle the edge of the water indicating shoreline hunting or drinking behavior. Tracks in pustular MISS destroyed the original mat and subsequently the mat recovered with a smaller pustular texture development, implying the mats were moist when impressed. Tracks linked to the blister mat consisted of two different impression types: (1) destroyed mat texture with plastically de- formed sediment, and (2) fragmented mat on top of the plastically deformed sediment in the true track. These vertebrate track types had a limited development win- dow, centered on the two-month, high-water lake lev- el followed by track formation in the lower elevations. Any vertebrates that traversed the area out of the “track preservation window” were not recorded in sediment deformation or mat modification as numerous gener- ations of scat preserved on the sediment surface. Even during the optimal time period, smaller fauna cannot exert enough vertical pressure to affect the mat or the underlying sediment. Annual variation in precipitation inducing lake-level change will increase the preserva- tion potential of the lake margin track systems. ACKNOWLEDGMENTS Kutztown University (KU) Research Committee funded participation of KU students and staff. Con- necticut State University-American Association of University Professors Faculty Research Grants funded participation of Central Connecticut State University students and staff. Kurt Friehauf (Kutztown University) aided in the FESEM and EDS analyses. We thank John Foster, Utah Field House of Natural History State Park Museum, and Doug Sprinkel, Azteca Geosolutions, for their helpful reviews. REFERENCES Allen, J.R.L., 1989, Fossil vertebrate tracks and indenter mechanics: Journal Geological Society London, v. 146, p. 600–602. Alimova, A., Roberts, M., Katz, A., Rudolph, E., Steiner, J.C., Al- fano, R.R., and Gottlieb, P., 2006, Effects of semectite clay on biofilm formation by microorganisms: Biofilm, v. 3, p. 47–54. Anderson, P.B., Willis, G.C., Chidsey, T.C., Jr., and Sprinkel, D.A., Geology of Glen Canyon National Recreation Area, Utah-Ar- izona, in Sprinkel, D.A., Chidsey, T.C., Jr., and Anderson, P.A., Geology of Utah’s Parks and Monuments (third edition): Utah Geological Association Publication 28, p. 309–347. Avanzini, M., Frisia, S., Van Den Driessche, K., and Keppens, E., 1997, A dinosaur tracksite in an Early Liassic tidal flat in north- ern Italy—paleoenvironmental reconstruction from sedimen- tology and geochemistry: PALAIOS, v. 12, p. 538–551. Barnett, T.P., Adam, J.C., and Lettenmaierm D.P., 2005, Poten- tial impacts of a warming climate on water availability in snow-dominated regions: Nature, v. 438, p. 303–309. Belvedere, M., Franceschi, M., Sauro, F., and Mietto, P., 2017, Di- nosaur footprints from the top of Mt. Pelmo—new data for Early Jurassic palaeogeography of the Dolomites (NE Italy): Bulletin Society of Paleontology Italia, v. 56, i–viii. https://doi. org/10.4435/ BSPI.2017.10, 2017. 148 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 Bottjer, D., and Hagadorn, J.W., 2007, Mat growth features, in Schieber, J., Bose, P.K., Eriksson, P.G., Banerjee, S., Sarkar, S., Altermann, W., and Catuneanu, O., editors, Atlas of mat fea- tures preserved within the siliciclastic rock record: Atlases in Geosciences 2, p. 53–71. Bouougri, E.H., and Porada, H., 2012, Wind-induced mat defor- mation structures in recent tidal flats and sabkhas of SE Tuni- sa and their significance for environmental interpretation of fossil structures: Sedimentary Geology, v. 263–264, p. 56–66. Carmona, N., Bournod, C., Ponce, J.J., and Cuadrado, D., 2011, The role of microbial mats in the preservation of bird foot- prints—a case study from the mesotidal Bahia Blanca Estuary (Argentina), in Noffke, N., and Chafetz, H., editors, Microbial mats in siliciclastic depositional systems through time: Society for Sedimentary Geology (SEPM) Special Publication 101, p. 37–45. Carvalho, I.S., 2004, Dinosaur footprints from northeastern Bra- zil—taphonomy and environmental setting: Ichnos, v. 11, p. 112–121, doi: 10.1080/10420940490442368. Carvalho, I.S., Borghi, L., and Leonardi, G., 2013, Preservation of dinosaur tracks induced by microbial mats in the Sousa Ba- sin (Lower Cretaceous), Brazil: Cretaceous Research, v. 44, p. 112–121. Carvalho, I.S., and Leonardi, G., 2021, Fossil footprints as bi- osedimentary structures for paleoenvironmental interpre- tation—examples from Gondwana: Journal of South Amer- ican Earth Science, v. 106, 102936, https://doi.org/10.1016/j. jsames.2020.102936. Chafetz, H.S., and Buczynski, C., 1992, Bacterially induced lithifi- cation of microbial mats: PALAIOS, v. 7, p. 277–293. Cohen, A.S., 2003, Paleolimnology—the history and evolution of lake systems: New York, Oxford University Press, 500 p. Conti, M.A., Morsilli, M., Nicosia, U., Sacchi. E., Savino, V., Wa- gensommer, A., Di Maggio, L., and Gianolla, P., 2005, Juras- sic dinosaur footprints from southern Italy—footprints as indicators of constraints in paleogeographic interpretation: PALAIOS, v. 20, p. 534–550. Cuadrado, D., Carmona, N.B., and Bournod, C., 2011, Biostabiliza- tion of sediments by microbial mats in a temperate siliciclastic tidal flat, Bahia Blanca estuary (Argentina): Sedimentary Ge- ology, v. 237, p. 95–101. Cuadrado, D.G., Maisano, L., and Quijada, I.E., 2021, Role of mi- crobial mats and high sedimentation rates in the early burial and preservation of footprints in siliciclastic tidal flat: Jour- nal of Sedimentary Research, v. 91, p. 479–494. DOI: 10.2110/ jsr.2020.149 Dai, H., Xing, L.D., Marty, D., Zhang, J., Persons, W.S., IV, Hu, H., and Wang, F., 2015, Microbially-induced sedimentary wrinkle structures and possible impact of microbial mats for the en- hanced preservation of dinosaur tracks from the Lower Cre- taceous Jiaguan Formation near Qijang (Chongqing, China): Cretaceous Research, v. 53, p. 98–109. Dalman, S.G., and Weems, R.E., 2013, A new look at morpho- logical variation in the ichnogenus Anomoepus, with special reference to material from the Lower Jurassic Newark Super- group—implications for ichnotaxonomy and ichnodiversity: Peabody Museum of Natural History Bulletin 54, p. 67–124. Davies, N.S., Alexander, G., Liu, A.G., Gibling, M.R., and Mill- er, R.F., 2016, Resolving MISS conceptions and misconcep- tions—a geological approach to sedimentary surface textures generated by microbial and abiotic processes: Earth Science Reviews, v. 154, p. 210–246. Dott, R.H., Jr., Byers, C.W., Fielder, G.W., Stenzel, S.R., and Win- free, K.E., 1986, Aeolian to marine transition in Cambro-Or- dovician cratonic sheet sandstones of the northern Mississippi Valley, U.S.A.: Sedimentology, v. 33, p. 345–367. Dupraz, C., Reid, R.P., Braissant, O., Decho, A.W., Norman, R.S., and Visscher, P.T., 2009, Processes of carbonate precipitation in modern microbial mats: Earth Science Reviews, v. 96, p. 141–162. Falkingham, P.L., and Gatesy, S.M., 2014, The birth of a dinosaur footprint—subsurface 3D motion reconstruction and discrete element simulation reveal track ontogeny: Proceedings Na- tional Academy Sciences, v. 111, p. 18279–18284. Fillmore, D.L., Lucas, S.G., and Simpson, E.L., 2012, Ichnology of the Mississippian Mauch Chunk Formation, eastern Pennsyl- vania: New Mexico Museum Natural History and Science Bul- letin 54, 135 p. Fillmore, D.L., Szajna, M.J., Lucas, S.G., Hartline, B.W., and Simp- son, E.L., 2017, Ichnology of the Late Triassic lake margin— the Lockatong Formation, Newark Basin, Pennsylvania: New Mexico Museum of Natural History and Science Bulletin 76, 107 p. Fryberger, S.G., Al-Sari, A.M., and Clisham, T.J., 1983, Eolian dune, interdune, sand sheet, and siliciclastic sabkha sediments of an offshore prograding sand sea, Dhahran area, Saudi Ara- bia: American Association Petroleum Geologists Bulletin, v. 67, p. 280–312. Fryberger, S.G., Schenk, C.J., and Krystinik, L., 1988, Stokes surfac- es and the effects of near-surface groundwater-table on aeolian deposition: Sedimentology, v. 35, p. 21–41. Gatesy, S.M., and Falkingham, P.L., 2017, Neither bones nor feet— track morphological variation and ‘preservation quality’: Jour- nal of Vertebrate Paleontology, e1314298 https://doi. org/10.1 080/02724634.2017.1314298. Hunter, R.E., 1973, Pseudo-cross-lamination formed by climbing adhesion ripples: Journal of Sedimentary Petrology, v. 43, p. 1125–1127. 149 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 Kocurek, G., and Fielder, G., 1982, Adhesion structures: Journal of Sedimentary Petrology, v. 52, p. 1229–1241. Koster, E.A., Ilona, I.Y., and Nap, R.L., 1993, Genesis and sedi- mentary structures of late Holocene aeolian drift sands in northwest Europe, in Pye, K., editor, The dynamics and envi- ronmental context of aeolian sedimentary systems: Geologic Society of London Special Publication 72, p. 247–267. Kumar, S., and Ahmad, S., 2014, Microbially induced sedimenta- ry structures (MISS) from the Ediacaran Jodhpur Sandstone, Marwar Supergroup, western Rajasthan: Journal of Asian Earth Sciences, v. 91, p. 352–361. Laporte, L.F., and Behrensmeyer, A.K., 1980, Tracks and substrate reworking by terrestrial vertebrates in Quaternary sediments of Kenya: Journal of Sedimentary Petrology, v. 50, p. 337–346. Livingston, K.M., Bogner, E., Simpson, E.L., Malenda, M., Sherrod, L.A., Betts, T.A., and Laub, E., 2015, The proposed evolution of shallow-sourced methane mud volcano geomorphology Lake Powell, Hite Utah [abs.]: Geological Society of America Ab- stracts with Programs, v. 47, no. 6, p. 588. Lockley, M.G., 1986, The paleobiological and paleoenvironmental importance of dinosaur footprints: PALAIOS, v.1, p. 37–47. Lockley, M.G., 1987, The paleoecological and paleoenvironmental utility of dinosaur tracks, in Farlow, J.O., and Brett-Surman, M.K., editors, The complete dinosaur: Bloomington, Indiana University Press, p. 554–578. Lockley, M.G., 1991a, Tracking dinosaurs—a new look at an an- cient world: Cambridge University Press, Cambridge, 238 p. Lockley, M.G., 1991b, The dinosaur footprint renaissance: Modern Geology, v. 16, p.139–160. Lockley, M.G., and Conrad, K., 1989, The paleoenvironmental context, preservation and paleoecological significance of di- nosaur tracksites in the Western USA, in Gillette, D.D., and Lockley, M.G., editors, Dinosaur tracks and traces: Cambridge University Press, Cambridge, p. 121–134. Lockley, M.G., and Hunt, A.P., 1995, Dinosaur tracks and other fossil footprints of the Western United States: Columbia Uni- versity Press, New York, 338 p. Lockley, M.G., Gierlinski, G.D., Dubicka, Z., Breithaupt, B., and Matthews, N., 2014a, A preliminary report on a new dinosaur tracksite in the Cedar Mountain Formation (Cretaceous) of eastern Utah, in Lockley, M.G., and Lucas, S.G., editors, Fossil footprints of western North America: New Mexico Museum of Natural History and Science Bulletin 62, p. 279–285. Lockley, M.G., Gierlinski, G.D., Houck, K., Lim, J.D-., Kim, K.S., Kim, D-.L., Kim, T.H., Kang, S-.H., Hunt Foster, R., Li, R., Chesser, C., Gay, R., Dubicka, Z., Cart, K., and Wright, C., 2014b, New excavations at the Mill Creek Canyon Dinosaur Track Site (Cedar Mountain Formation, Lower Cretaceous) of eastern Utah, in Lockley, M.G., and Lucas, S.G., editors, Fossil footprints of western North America: New Mexico Museum of Natural History and Science Bulletin 62, p. 287–300. Lockley, M.G., and Rodríguez-de la Rosa, R.A., 2009, Preservation of human tracks in arid environments: Ichnos, v. 16, p. 98–102. Malenda, M., Betts, T.A., Simpson, W.S., Wizevich, M.C., Simp- son, E.L., and Sherrod, L. 2020, Methane emissions from muds during low water-level stages of Lake Powell southern Utah, USA: Geology of the Intermountain West, v. 7, p. 97–112. Manning, P., 2004, A new approach to the analysis and interpreta- tion of tracks—examples from the dinosauria, in McIlroy, D., editor, The application of ichnology to palaeoenvironmental and stratigraphic interpretation: Geologic Society of Lon- don Special Publication 228, https://doi.org/10.1144/GSL. SP.2004.228.01.06 Marchetti, L., Belvedere, M., Voigt, S., Klein, H., Castanera, D., Díaz-Martínez, I., Marty, D., Xing, L., Feola, F., Melchor, R.N., and Farlow, J.O., 2019a, Defining the morphological quality of fossil footprints—problems and principles of preservation in tetrapod ichnology with examples from the Palaeozoic to the present: Earth Science Review, v. 193, p. 109–145. Marchetti, L., Voigt, S., Lucas, S.G., Francischini, H., Dentzien-Di- as, P., Sacchi, R., Mangiacotti, M., Scali, S., Gazzola, A., Ron- chi, A., and Millhouse, A., 2019b, Tetrapod ichnotaxonomy in eolian paleoenvironments (Coconino and De Chelly Forma- tions, Arizona) and late Cisuralian (Permian) sauropsid radia- tion: Earth Science Review, v. 190, p. 148–170. Marchetti, L., Francischini, H., Lucas, S.G., Voigt, S., Hunt, A.P., and Santucci, V.L., 2020, Paleozoic vertebrate ichnology of Grand Canyon National Park, Chapter 9, in Santucci, V.L., and Tweet, J.S., editors, Grand Canyon National Park—centennial paleontology resource inventory (non-sensitive version): Nat- ural Resource Report NPS/GRCA/NRR—2020/2103, National Park Service, Fort Collins, Colorado, p. 333–379. Marty, D., Strasser, A., and Meyer, C.A., 2009, Formation and taphonomy of human footprints in microbial mats of pres- ent-day tidal flat environment—implications for the study of fossil footprints: Ichnos, v. 16, p. 127–142. Milań, J., and Bromley, R.G., 2006, True tracks, undertracks and eroded tracks, experimental work with tetrapod tracks in lab- oratory and field: Palaeogeography Palaeoclimatogy Palaeo- ecology, v. 231, p. 253–264. Milań, J., Clemmensen, L.B., and Bonde, N., 2004, Vertical sec- tions through dinosaur tracks (Late Triassic lake deposits, East Greenland)—undertracks and other subsurface deformation structures revealed: Lethia, v. 37, p. 285–296. Milań, J., and Loope, D.B., 2007, Preservation and erosion of thero- pod tracks in eolian deposits—examples from the Middle Ju- rassic Entrada Sandstone, Utah, U.S.A.: Journal of Geology, v. 115, p. 375–386. 150 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 Miller, K., Simpson, E.L., Sherrod, L., Wizevich, M.C., Malenda, M., Morgano, K., Richardson, A., Livingston, K., Bogner, E., 2018, Gas bubble cavities in deltaic muds, Lake Powell delta, Glen Canyon National Recreation Area, Hite, Utah: Marine and Petroleum Geology, v. 92, p. 904–912, doi: 10.1016/j.mar- petgeo.2018.03.032. Moratalla, J.J., Marugan-Lobon, J., Martin-Abad, H., Cuesta, E., and Buscalioni, A.D., 2017, A new trackway possibly made by a trotting theropod at the Las Hoyas fossil site (Early Creta- ceous, Cuenca Province, Spain)—identification, bio-dynam- icsm and palaeoenvironmental implications: Palaeontologic Electronica, v. 20, p. 1–14. Nadon, G.C., 2001, The impact of sedimentology on vertebrate track studies, in Currie, P.J., Tanke, D.H., Carpenter, K., and Skrepnick, M.W., editors, Mesozoic vertebrate life: Indiana University Press, p. 395–407. Netoff, D., Baldwin, C.T., and Dohrenwend, J., 2010, Non-seismo- genic origin of fluid/gas escape structures and lateral spreads on the recently exposed Hite delta, Lake Powell, Utah, in Car- ney, S.M., Tabet, D.E., and Johnson, C.L., editors, Geology of south-central Utah: Utah Geological Association Publication 39, p. 61–92. Noffke, N., 1999, Erosional remnants and pockets evolving from biotic-physical interactions in a Recent lower supratidal envi- ronment: Sedimentary Geology, v. 123, p. 175–181. Noffke, N., 2009, The criteria for the biogenicity of microbially in- duced sedimentary structures (MISS) in Archean and young- er, sandy deposits: Earth Science Reviews, v. 96, p. 173– 180. Noffke, N. 2010, Geobiology—microbial mats in sandy deposits from Archean Era: Berlin, Springer, 194 p. Noffke, N., and Chafetz, H., editors, 2012, Microbial mats in si- liciclastic depositional systems through time: Society for Sedi- mentary Geology (SEPM) Special Publication 101, 198 p. Noffke, N., Eriksson, K.A., Hazen, R.E., and Simpson, E.L., 2006, A new window into early life—microbial mats in the Earth’s oldest siliciclastic tidal flats (3.2 Ga Moodies Group, South Af- rica): Geology, v. 34, p. 253–254. Noffke, N., Gerdes, G., Klenke, T., and Krumben, W. E., 2001, Mi- crobially induced sedimentary structures—a new category within the classification of primary sedimentary structures: Journal of Sedimentary Research, v. 71, p. 649–656. Noffke, N., Hagadorn, J., and Bartlett, S., 2019, Microbial struc- tures and dinosaur trackways from a Cretaceous coastal envi- ronment (Dakota Group, Colorado, U.S.A.): Journal Sedimen- tary Research, v. 89, p. 1096–1108. Noffke, N., Gerdes, G., Klenke, T., and Krumbein, W.E., 2002, Mi- crobially induced sedimentary structures—a new category within the classification of primary sedimentary structures— Reply: Journal Sedimentary Research, v. 72, p. 589–590. Olsen, H., Due, P.H., and Clemmensen, L.B., 1989, Morphology and genesis of asymmetrical adhesion warts—a new adhesion surface structure: Sedimentary Geology, v. 61, p. 277–285. Paik, I.S., Kim, H.J., and Lee, Y.I., 2001, Dinosaur track-bearing deposits in the Cretaceous Jindong Formation, Korea—occur- rence, palaeoenvironments and preservation: Cretaceous Re- search, v. 22, p. 79–92. Peabody, F.E., 1947, Current crescents in the Triassic Moenkopi Formation: Journal of Sedimentary Petrology, v. 17, p. 73–76. Peabody, F.E., 1948, Reptile and amphibian trackways from the Lower Triassic Moenkopi Formation of Arizona and Utah: Department Geological Sciences Bulletin, University of Cal- ifornia, v. 27, p. 295–468. Porada, H., Bouougri, E., and Ghergut, J., 2007, Hydraulic condi- tions and mat related structures in tidal flats and coastal sab- khas, in Schieber, J., Bose, B.K., Eriksson, P. G., Banerjee, S., Altermann, W., and Catuneau, O., editors, Atlas of microbial mat features preserved within the clastic rock record: Amster- dam, Elsevier, p. 258–265. Pratson, L., Hughes-Clarke, J., Anderson, M., Gerber, T., Twichell, D., Ferrari, R., Nittrouer, C., Beaudoin, J., Granet, J., and Crockett, J., 2008, Timing and patterns of basin infilling as documented in Lake Powell during a drought: Geology, v. 36, p. 843–846, doi: 10.1130/G24733A.1. Prave, A.R., 2002, Life on land in the Proterozoic—evidence from the Torridonian rocks of northwest Scotland: Geology, v. 30, p. 811–814. Richter, A., and Böhme, A., 2016, Too many tracks—preliminary description and interpretation of the diverse and heavily di- noturbated Early Cretaceous “chicken yard” ichnoassemblage (Obernkirchen Tracksite, North Germany), in Falkingham, P.L., Marty, D., and Richter, A., editors, Dinosaur tracks: Bloomington, Indiana University Press, p. 334–357. Sadro, S., Sickman, J.O., Melack, J.M., and Skeen, K., 2018, Effects if climate variability on snowmelt and implications for oragnic matter in a high-elevation lake: Water Resources Research, v. 54, p. 4563–4578. Schieber, J., 2007, Microbial mat features in terrigenous clastics of the Belt Supergroup, Mid Proterozoic of Montana, USA., in Schieber, J., Bose, P.K., Eriksson, P.G., Banerjee, S., Sarkar, S., Altermann, W., and Catuneanu, O., editors, Atlas of mat fea- tures preserved within the siliciclastic rock record: Atlases in Geosciences 2, p. 158–170. Sheldon, N.D., 2012, Microbially induced sedimentary structures in the ca. 1100 Ma terrestrial midcontinent rift of North America, in Noffke, N., and Chafetz, H., editors, Microbial mats in siliciclastic depositional systems through time: Soci- ety for Sedimentary Geology (SEPM) Special Publication 101, p. 153–162. 151 Microbially Induced Sedimentary Structures and the Preservation of Vertebrate Tracks on the Colorado River Delta in Lake Powell, Hite, Utah Simpson, E.L., Wizevich, M.C., Pittinger, D., Rogers, G, and Lazer, K. Geology of the Intermountain West 2022 Volume 9 Sherrod, L., Simpson, E.L., Higgins, R., Miller, K., Morgano, K., Snyder, E., and Vales, D., 2016, Subsurface structure of water– gas escape features revealed by ground-penetrating radar and electrical resistivity tomography, Glen Canyon National Rec- reation Area, Lake Powell delta, Utah, USA: Sedimentary Ge- ology, v. 344, p. 160–174, doi: 10.1016/j.sedgeo.2016.02.005. Simpson, E.L., 1983, The geometry and structure of interdune de- posits at White Sands National Monument, New Mexico: Lin- coln, University Nebraska, M.S. thesis, 83 p. Simpson, E.L., and Loope, D.B., 1985, Amalgamated interdune deposits, White Sands, New Mexico: Journal of Sedimentary Petrology, v. 55, p. 361–365. Simpson, E.L., and Simpson, W.S., 2014, Modern continental mi- crobial mat structures—analogs for Precambrian landscapes [abs.]: Geological Society of American Abstracts with Pro- grams, v. 46, no. 6, p. 87. Simpson, E.L., Wizevich, M.C., Reichard-Flynn, W.R., Keebler, A.M., Evans, S., and Kuslik, I., 2022, Pustularichnis rebecca- huntfosteri, a microbially induced sedimentary structure— Early Cretaceous Cedar Mountain Formation, Mill Canyon Dinosaur Tracksite, Moab, Utah, in Lucas, S.G., Blodgett, R.B., Lichtig, A.J., and Hunt, A.P., editors, The Fossil Record 8: New Mexico Museum of Natural History and Science Bulletin 90, p. 371–379. Szewcy, K, L., Vennin, E., Moreau, J.-D., Gand, G., Verolet, M., Klee, N., and Fara, E., 2020, Tracking dinosaur in course-grained sediments from the Upper Triassic of Ardèche (Southeastern France): PALAIOS, v. 35, p. 447–460. Thulborn, T., 1990, Dinosaur tracks (first edition): London, United Kingdom, Chapman and Hall, 410 p. Waldo, S., Deemer, B.R., Bair, L.S., and Beaulieu, J.J., 2021, Green- house gas emission from arid-zone reservoir and their envi- ronmental policy significance—results from existing global models and an exploratory data set: Environmental Science Policy, v. 120, p. 53–62. Willis, C.G., 2012, Geologic map of the Hite Crossing–lower Dirty Devil River area, Glen Canyon National Recreation Area, Garfield and San Juan Counties, Utah: Utah Geological Sur- vey Map 254DM, 12 p., 1 plate, scale 1:62,500, https://doi. org/10.34191/M-254dm. Wilmeth, D.T., Dornbos, S.Q., Isbell, J.L., and Czaja, A.D., 2014, Putative domal microbial structures in fluvial siliciclastic fa- cies of the Mesoproterozoic (1.09 Ga) Copper Harbor Con- glomerate, Upper Peninsula of Michigan, USA: Geobiology, v. 12, p. 99–108. Xing, L., Lockley, M.G., Marty, D., Zhang, J., Klein, H., McCrea, R.T., Buckley, L.G., Belvedere, M., Mateus, O., Gierlinski, G.D., Pinuela, L., Persons, W.S., Wang, F., Ran, H., Dai, H., and Xie, X., 2015a, An ornithopod-dominated tracksite from the Lower Cretaceous Jiaguan Formation (Barremian-Albian) of Qijang, south-central China—new discoveries, ichnotaxono- my, preservation and palaeoecology: PLoS One, 10, e0141059. Xing, L., Li, D., Lockley, M.G., Marty, D., Zhang, J., Scott Persons, W., You, H., Peng, C., and Kümmell, S.B., 2015b, Dinosaur nat- ural track casts from the Lower Cretaceous Hekou Group in the Lanzhou-Minhe Basin, Gansu, northwest China—ichnol- ogy, track formation, and distribution: Cretaceous Research, v. 52, p. 194–205, doi: 10.1016/j. cretres.2014.10.001. Xing, L., Peng, G., Lockley, M.G., Ye, Y., Klein, H., McCrea, R.T., Zhang, J., and Scott Persons, W., 2015c, Saurischian (thero- pod-sauropod) track assemblages from the Jiaguan Formation in the Sichuan Basin, southwest China—ichnology and indi- cations to differential track preservation: Historical Biology 28, p. 1003–1013, doi: 10.1080/0 8912963.2015.1088845. Zhong-Wu, L., Zhong-Qiang, C., Xian-Hua, L., and Kuino, K., 2013, Microbially induced sedimentary structures from the Mesoproterozoic Huangqikou Formation, Helan Mountain re- gion, northern China: Precambrian Research, v. 233, p. 73–92.