Low-energy Shoreline Research Articles

Seasonal Morphological Variability on Estuarine Beaches and Implications for Low-Energy Beach Management

Mercaldi, B.; Brideau, L.E.; Tait, J.F., and Griggs, G., 2022. Seasonal morphological variability on estuarine beaches and implications for low-energy beach management. Journal of Coastal Research, 38(6), 1135–1147. Coconut Creek (Florida), ISSN 0749-0208. Estuarine beaches and other low-energy shorelines are critical for habitats and coastal infrastructure protection. Many different species inhabit estuaries because of the water bodies' unique characteristics, such as their mixed seawater and freshwater and variable tidal ranges. Estuarine beaches also have the important role of buffering storm wave energy. Yet, their natural physical processes are understudied. This research focuses on seasonal morphological variability of estuarine, low-energy beaches and evaluates the implications for beach management practices. Five sandy beaches were studied along the northern shoreline of Long Island Sound in the northeastern region of the United States. The studied beaches vary in location, width, length, and orientation within Long Island Sound to represent different exposures to wave energy. Three seasonal profiles were measured at each beach approximately every four months from late 2015 to early 2019 to document topographic changes. The results revealed minimal sediment movement throughout the study period and there was no evidence of significant cyclic cross-shore sediment transport to indicate patterns of seasonal profile changes. These findings reveal important implications for beach management practices on low-energy shorelines. Specifically, estuarine and other low-energy beaches should be studied on decadal time scales to document any long-term variability and post-storm recovery rather than the monthly or yearly time scales on which open-ocean beaches are typically evaluated. Additionally, estuarine beaches and other low-energy shorelines require specialized management practices that cater to their stagnancy to ensure adequate protection of coastal structures and infrastructure in the face of intensifying hurricanes and sea level rise.

Reef design and site hydrodynamics mediate oyster restoration and marsh stabilization outcomes.

The detrimental ecological impacts of engineered shoreline protection methods (e.g., seawalls) and the need to protect the coastal zone have prompted calls for greater use of natural and nature-based infrastructure (NNBI). To balance competing needs of structural stability and ecological functioning, managers require assessments of NNBI designs and materials for differing environmental settings (e.g., among wave-energy regimes). To examine the effects of setting and oyster-based NNBI design on the provision of shoreline protection, we constructed reefs from two substrates: a novel, biodegradable material (Oyster Catcher, OC) and traditional oyster shell bags (SB) on low- and high-energy eroding salt marsh shorelines, designated based on fetch and boat wake exposure. Both reef types buffered marsh elevation change on the high-energy shoreline relative to unaltered controls, but only SB reefs were able to do so on the low-energy shoreline. Additionally, both shorelines experienced high ambient rates of retreat and declines in marsh vegetation shoot density. Although constructed reefs did not mitigate marsh retreat on the low-energy shoreline, novel OC reefs significantly reduced retreat relative to SB reefs and control sites (no reefs) on the high-energy shoreline. Those SB reefs were severely damaged by storm events, increasing their areal footprints at the expense of vertical relief. Conversely, OC reefs on both shorelines exhibited steady oyster recruitment and growth and hosted higher densities of larger oysters. To successfully provide shoreline stabilization benefits, oyster-based NNBI must be structurally stable and able to promote sustained oyster recruitment and growth. Our results indicate that deliberate decisions regarding NNBI substrate, siting, and configuration can produce resilient reefs, which reduce rates of erosion and, in some cases, enhance vertical accretion along salt marsh edges. The growth trajectory, structural stability, and co-benefit provisioning of OC reefs demonstrate the potential of alternative restoration substrates to provide valuable oyster habitat along threatened marsh shorelines.

Biological Flora of the Tropical and Subtropical Intertidal Zone: Literature Review for Rhizophora mangle L.

DeYoe, H.; Lonard, R.I.; Judd, F.W.; Stalter, R., and Feller, I., 2020. Biological flora of the tropical and subtropical intertidal zone: Literature review for Rhizophora mangle L. Journal of Coastal Research, 36(4), 857–884. Coconut Creek (Florida), ISSN 0749-0208.Rhizophora mangle L. is a tropical and subtropical mangrove species that occurs as a dominant tree species in the intertidal zone of low-energy shorelines. Rhizophora mangle plays an important role in coastal zones as habitat for a wide range of organisms of intertidal food webs, as a natural barrier to coastal erosion, and as carbon sequestration. A review of mangrove literature has been performed, but a review specifically on red mangroves has not. The approach was to cover a broad range of topics with a focus on topics that have seen significant work since the 1970s. This review includes a brief introduction to red mangroves and then focuses on the following topics: biogeography, habitats and zonation, geomorphological interactions, taxonomy, histology, anatomy, physiological ecology, productivity, biomass, litter, reproduction, population biology, plant communities, interactions with other species, impacts of storms, reforestation, remote sensing, modelling, and economic importance.

Defining boat wake impacts on shoreline stability toward management and policy solutions

Coastal economies are often supported by activities that rely on commercial or recreational vessels to move people or goods, such as shipping, transportation, cruising, and fishing. Unintentionally, frequent or intense vessel traffic can contribute to erosion of coastlines; this can be particularly evident in sheltered systems where shoreline erosion should be minimal in the absence of boat waves. We reviewed the state of the science of known effects of boat waves on shoreline stability, examined data on erosion, turbidity, and shoreline armoring patterns for evidence of a response to boat waves in Chesapeake Bay, and reviewed existing management and policy actions in Chesapeake Bay and nearby states to make recommendations for actions to minimize boat wake impacts. In the literature, as well as in our analyses, boat wake energy may be linked to elevated turbidity and shoreline erosion, particularly in narrow waterways. In Chesapeake Bay, three lines of evidence suggest boat waves are contributing to shoreline erosion and poor water clarity in some Bay creeks and tributaries: 1) nearshore turbidity was elevated in many waterways during periods of expected high boating activity, 2) armoring was placed along about a quarter of the low energy shorelines of three examined tidal creeks that are exposed to relatively high boating pressure, and 3) 15% of the shorelines we examined throughout the Bay (9000 km) are low energy shorelines that are experiencing high erosion (≥0.3 m/yr) that cannot be attributed to wind wave energy. Still, there remain significant data gaps that preclude the determination of the overall contribution of boat waves to shoreline erosion throughout the Bay, notably, shoreline erosion data in low energy waterways, recreational boating traffic patterns, and nearshore bathymetry. Interim protective measures can be (and have been) applied in high risk waterways, such as small, low energy waterways that have high recreational boating activity, to help reduce shoreline erosion. Policy options used in Bay states and elsewhere include setbacks from the shore, wake restrictions, and speed restrictions; other more restrictive policies may include prohibition on boats of a certain size or limiting the number of passages. Finally, a systems-approach to boat wake impact management using uniform boat wake policies is likely to be the most effective for consistent shoreline protection.

The Potential for Created Oyster Shell Reefs as a Sustainable Shoreline Protection Strategy in Louisiana

Abstract Coastal protection remains a global priority. Protection and maintenance of shoreline integrity is often a goal of many coastal protection programs. Typically, shorelines are protected by armoring them with hard, non‐native, and nonsustainable materials such as limestone. This study investigated the potential shoreline protection role of created, three‐dimensional Eastern oyster (Crassostrea virginica) shell reefs fringing eroding marsh shorelines in Louisiana. Experimental reefs (25 × 1.0 × 0.7 m; intertidal) were created in June 2002 at both high and low wave energy shorelines. Six 25‐m study sites (three cultched and three control noncultched) were established at each shoreline in June 2002, for a total of 12 sites. Shoreline retreat was reduced in cultched low‐energy shorelines as compared to the control low‐energy shorelines (analysis of variance; p < 0.001) but was not significantly different between cultched and noncultched sites in high‐energy environments. Spat set increased from 0.5 ± 0.1 spat/shell in July 2002 to a peak of 9.5 ± 0.4 spat/shell in October 2002. On average, oyster spat grew at a rate of 0.05 mm/day through the duration of the study. Recruitment and growth rates of oyster spat suggested potential reef sustainability over time. Small fringing reefs may be a useful tool in protecting shorelines in low‐energy environments. However, their usefulness may be limited in high‐energy environments.

Origin and timing of siderite and calcite concretions in late Palaeogene non- to marginal-marine facies of the Te Kuiti Group, New Zealand

The Late Eocene-earliest Miocene Te Kuiti Group represents an overall transgressive sequence of formations ranging upwards from non-marine coal measure facies through marginal-marine low-energy shoreline siliciclastic sediments to fully-marine mixed siliciclastic-carbonate deposits. Concretionary structures are common in the lowest formations of the group, being dominantly sideritic in the non-marine to brackish sediment facies (Waikato Coal Measures and Glen Afton Claystone) and calcitic in the more marine-influenced sediments (Rotowaro Siltstone). The geochemistry of the carbonate cements within these early diagenetic concretions records the change from carbonate precipitation from purely meteoric fluids to precipitation from marine fluids, and a shifting source of carbonate carbon across this transition.Siderite precipitation in the Waikato Coal Measures concretions and hardpans was initiated and often largely completed in the methanogenic zone, within the upper 20 m of the sediment pile over a period possibly lasting 100–300 ka. Precipitation continued at a reduced rate to burial depths of 300 m or more when septarian cracking occurred in some siderite concretions and was healed by calcite vein cements that probably derived carbonate from the oxidation of methane ascending from the maturing coal seams directly below.Siderite precipitation in the concretions and hardpans of the overlying brackish-marine Glen Afton Claystone was completed in the topmost few metres of sediment, possibly a few 10 ka. Stable-isotope values near zero support a marine carbonate carbon source, suggested to be from remobilised shell material as evidenced by the common occurrence of shell casts in the formation and the high degree of Mg and Ca substitution in the siderites.The overlying marginal-marine to low-energy marine Rotowaro Siltstone contains calcite concretions precipitated from pore waters enriched in bicarbonate derived from the sulphate-reduction zone, largely within the upper 8 m of sediment, and possibly growing over a few 100 ka. Concretion development continued at a reduced rate to burial depths of several tens of metres and in some cases septarian cracks developed during the later stages of concretion growth. The precipitation of septarian vein calcites with more depleted δ18O values and more enriched δ13C signatures than central concretions cements, may be due to increasing burial temperatures, and the progressive introduction of carbonate sourced from shell dissolution.

BIOREMEDIATION: APPLICATION OF SLOW-RELEASE FERTILIZERS ON LOW-ENERGY SHORELINES

ABSTRACT In situ biodegradation, the activation of microbial processes capable of destroying contaminants where they are found in the environment, is a biological process that responds rapidly to changing environmental factors. Accordingly, in situ sediment enclosures were used to test the efficacy of selected nutrient formulations to enhance the biodegradation of a waxy crude oil in a low-energy shoreline environment. The addition of soluble inorganic fertilizers (ammonium nitrate and triple superphosphate) and slow-release nutrient formulations (sulfur-coated urea) stimulated microbial activity and prolonged the period of oil degradation, despite a decline in seasonal temperatures. Low temperatures reduced the permeability of the coating on the slow-release fertilizers, effectively suppressing nutrient release. Of the nutrient formulations evaluated, we recommend the application of granular slow-release fertilizers (such as sulfur-coated urea) when the overlying water temperatures are above 15° C, and the application of soluble inorganic fertilizers (such as ammonium nitrate) at lower temperatures. Comprehensive analysis of the experimental results indicate that application protocols for bioremediation (form and type of fertilizer or type and frequency of application), be specifically tailored to account for differences in environmental parameters (including oil characteristics) at each contaminated site.

Bioremediation: Waxy Crude Oils Stranded on Low-Energy Shorelines

ABSTRACT The degradation of a waxy crude oil (Terra Nova) spilled on sand beach and salt marsh environments in Nova Scotia was monitored over a seven-month period. In the sand beach environment, low concentrations of stranded oil (0.3 percent by volume) were degraded in a matter of days by the indigenous biota, while higher concentrations (3 percent) were much more persistent (components as light as n–C11 remained after six months). In contrast, similar concentrations of oil were found to be extremely resistant to biodegradation in the salt marsh. Our results suggest that cleanup of waxy crude oils at low concentrations in sand beaches should be left to nature, since natural biodegradative processes occur rapidly. At higher oil concentrations, however, nutrient enrichment with agricultural fertilizers was found to be an effective countermeasure. While biodegradation of oil stranded in salt marsh environments is generally limited by oxygen availability, nutrient enrichment may be an effective countermeasure to treat low concentrations of waxy crude oil in salt marshes, provided the oil does not penetrate beneath the aerobic surface layer.

Wabek and Plaza Fields: Carbonate Shoreline Traps in the Williston Basin of North Dakota

Wabek and Plaza fields in Mountrail and Ware counties, North Dakota, will ultimately produce 8 million and 3 million bbl of oil, respectively, from reservoirs in the Sherwood and Bluell intervals of the Mississippian Mission Canyon Formation. Both fields produce from porous, oolitic, and pisolitic lime packstones and grainstones deposited as shoals along a low-energy shoreline. A facies change to impermeable dolomitic and salina/sabkha environments to the east provides the updip trap. The Sherwood at Wabek has more than 100 ft of oil column driven by solution gas and water influx. Effective porosity consists of interparticle, vuggy, and minor dolomitic intercrystalline porosity. Log porosities range from 6 to 26%, averaging about 10%, and net pay averages about 26 ft. One mile west of Wabek, Plaza field produces from the Bluell, stratigraphically overlying the Sherwood. Log porosities range from 6 to 16%, averaging about 9%. Net pay averages about 6 ft. An oil-water contact is not yet defined, but at least 120 ft of oil column are present. Regional depositional slope and local depositional topography were major controls on Mission Canyon shoreline trends and the development of reservoir facies. In the Wabek-Plaza complex, the position and trend of the Sherwood andmore » Bluell shorelines can be related to structural trends indentified in the crystalline basement from aeromagnetic data. Locally, thickness variations in the underlying Mohall interval amplified relief on the Wabek-Plaza structure and influenced the deposition of shoreline reservoirs.« less

Tidal salt marsh restoration

Coastal salt marshes occur in the intertidal zone of moderate to low energy shorelines along estuaries, bays and tidal rivers. They have ecological value in primary production, nutrient cycling, as habitat for fish, birds and other wildlife and in stabilizing shorelines. Disturbance by development activities has resulted in the destruction or degradation of many marshes. Awareness of this loss by scientists and the public has led to an interest in restoration or creation of marshes to enhance estuarine ecosystems. Recovery of marshes after human perturbation such as dredging, discharges of wastes and spillage of petroleum products or other toxic chemicals is often slow under natural conditions and can be accelerated by replanting vegetation. The basic techniques and procedures have been worked out for the propagation of several marsh angiosperms. Factors which affect successful revegetation include elevation of the site in relation to tidal regime, slope, exposure to wave action, soil chemical and physical characteristics, nutrient supply, salinity and availability of viable propagules of the appropriate plant species. Marsh restoration technology has been applied at a variety of locations to vegetate intertidal dredged material disposal sites, stabilize shorelines, mitigate damage to natural marshes and to revegetate one marsh destroyed by an oil spill. Contractual services for marsh establishment are now available in some regions. Further research is needed to determine the success of marsh restoration and creation in terms of ecological function, including the faunal component.

Lithostratigraphic Analysis of Huntersville Chert of Central Appalachians: ABSTRACT

The Huntersville Chert (Onesquethawan Stage) of the central Appalachians was deposited in a detrital sediment-starved basin where a restricted sea hosted mainly silicisponges of probable Demospongid fauna. The Huntersville Chert grades into the Onondaga Limestone to the west and the Needmore Shale to the east. These Onesquethawan rocks record an initial transgression followed by regression, maximum transgression, and a final regression. Basement sub-blocks as growing structures influenced sedimentation. Differential subsidence of basement sub-blocks and eustatic changes in sea level periodically exposed the basin margins or allowed reworking of low-energy shoreline and shoal sediments. Five mappable stratigraphic units are recognized in the Onesquethawan Stage in the cher -filled basin covering the Rome trough in northern West Virginia, southwestern Pennsylvania, and northeastern Ohio. Shale tongues extending from the east interbed with the chert where the eastern West Virginia arch was low in northern West Virginia and western Maryland, but do not to reach the basin center. Carbonates accumulated over the shelf to the west of the chert basin and periodically over parts of the southern, eastern, and central arches. A moderately steep ramp is interpreted for the facies change from chert to limestone in proximity to the western margin of Rome trough. Are ancient reefs located at this shelf margin? The upper chert lithofacies is the most productive reservoir within the Huntersville. End_of_Article - Last_Page 1435------------

Depositional Styles of Notikewan Member (Upper Gates Equivalent), Fort St. John Group, Northeastern British Columbia: ABSTRACT

The subsurface Notikewan Member (Spirit River Formation) of the Fort St. John Group is correlative with the upper 60 to 70 End_Page 592------------------------------ m of the Gates Formation in northeastern British Columbia. The basal Notikewan is a thin pebbly transgressive lag deposit overlying carbonaceous nonmarine shales, sandstone, and locally conglomerates of the Gates (Falher equivalent). Overlying the transgressive lag is a 5 to 10 m fining-upward transgressive phase of interbedded sandstone or conglomerate and shale. The sandstones are hummocky cross-stratified and the conglomerates are molded into symmetrical gravel dunes (both features indicate storm processes were common during the transgression). The regressive phase is a 20 to 30-m coarsening-upward sequence showing much less evidence of storm influence. Locally 10 to 20 m thick sandstone channels cut through the shoreline into marine sediments. The precise location of the shoreline is generally difficult to pick, unlike in the underlying Falher cycles. Specimens of Ostrea above the channel sandstones suggest a brackish-water depositional environment. The Ostrea are a good local stratigraphic marker in the Bullmoose Mountain area, in some places forming banks. Sedimentary structures in interbedded sandstones, siltstones, and shales, and reversing paleoflow directions suggest a low-energy shoreline dominated by tidal flat and, possibly, estuarine processes. Paleocurrent data indicate that shoreline orientation was generally east-west. This is in marked contrast to the high-energy wave dominated shorelines of the Fahler. The upper 20 to 30 m of the Notikewan is nonmarine floodplain and overbank deposits with thin (< 1 m) coals, lagoonal shales and siltstones, and r re channels. End_of_Article - Last_Page 593------------

Pennsylvanian and Early Permian Paleogeography, Southern Colorado Plateau and Vicinity: ABSTRACT

Abstract Pennsylvanian and Lower Permian sedimentary rocks of the southern Colorado Plateau have been the subject of much controversy concerning their correlation and origin. Correlation of rock sequences and major unconformities from the fossiliferous basins onto the adjacent shelves, where relatively unfossiliferous rocks were deposited, has provided a new interpretation in terms of regional stratigraphy and depositional analysis. The Supai Group was deposited in the Grand Canyon Embayment adjacent to the Cordilleran Geosyncline. Sediments of Morrowan, Atokan, Virgilian and Wolfcampian ages were deposited in a variety of offshore marine and shoreline environments. A persistent southwest-to-northeast-trending unstable area, herein named the Sedona Arch, confined all Supai sediments, except Virgilian, to the Grand Canyon and western Mogollon Rim regions; the other strata are truncated beneath the sub-Virgilian unconformity or undergo significant facies change across the arch. The Naco Group of Desmoinesian, Missourian, and Virgilian age was deposited on the Mogollon Shelf adjacent to the Pedregosa Basin. Except for Virgilian strata, these dominantly marine rocks are also truncated beneath the sub-Virgilian unconformity across the Sedona Arch. Thus the bulk of Supai and Naco rocks are not as closely related as most previous workers had thought. Mostly marine rocks of the Molas Formation and Hermosa Group were deposited in the Paradox Basin. The northwest-to-southeast-trending Kaibab Arch provided the barrier between these rocks and the Supai and Naco to the south. Except for several transitional units, the Supai, Naco, and Hermosa Groups were deposited in distinctly separate basins and the units do not generally intertongue. The Wolfcampian Esplanade and Cedar Mesa Sandstones and Halgaito Formation form a distinct eastward-thinning wedge of rocks west of the Sedona Arch. These high-energy marine shoreline and supratidal units grade westward into thick marine carbonate sequences of the Cordilleran Geosyncline. A widespread redbed sequence comprising the Hermit and Organ Rock Formations was deposited across the entire study area. The continental and possibly tidal deposits represent a sharp change in depositional regime from the underlying and overlying sandstone deposits. The youngest sequence of deposition studied consists of sandstone, redbed, evaporite, and carbonate rocks of the Schnebly Hill Formation and DeChelly Sandstone. These units are centered around the Holbrook Basin and represent a complex of shallow marine, high- and low-energy shoreline, eolian, and sabkha depositional environments. This depositional sequence was confined to an area east of Grand Canyon and south of the San Juan River by the Sedona and Kaibab Arches. Both formations grade upward or intertongue with the overlying Coconino Sandstone and related rocks.

Paleobiologic Evidence for Cretaceous Tides, Western Interior Basin, North America: ABSTRACT

Modern intertidal environments contain a suite of diagnostic physical sedimentary structures and macro-invertebrate organisms. The former are often used in the identification of ancient intertidal paleoenvironments; the latter are rarely used. Yet the conservative evolution of intertidal organisms and their distinctive adaptive morphologies, expressed as preservable biogenic structures and/or shells, facilitate their identification in ancient strata. The habitat ranges of modern intertidal organisms are narrowly restricted within the intertidal zone. Groups of organisms with roughly equivalent habitats constitute distinct, low-diversity communities. In general, the total number of taxa in the intertidal biota and, accordingly, the number of recognizable communities increa e with increasing tidal range. We propose that: (1) fossil intertidal organisms and their traces can be used to recognize Mesozoic and Cenozoic intertidal paleoenvironments; and (2) the diversity and number of distinct paleocommunities recognizable among such faunas can be used to determine, at least qualitatively, paleotidal range. We have applied these concepts in a study of Cretaceous nearshore and marginal-marine strata in the western interior basin. Obligate or habitat-selective intertidal organisms occur along both shorelines of the interior Cretaceous seaway from northern Alberta to the Gulf of Mexico. Different groups of paleocommunities characterize exposed, wave-dominated, sandy coasts and low-energy, vegetated shorelines in marginal-marine settings. The compositions of the pal ocommunities along low-energy shorelines further vary with paleosalinity, permitting recognition of broad salinity gradients in Cretaceous estuarine settings. Faunal evidence indicates that Cretaceous tides extended throughout the interior Cretaceous seaway. The tidal range was generally greater along the western shoreline than along the eastern shoreline. Figure End_of_Article - Last_Page 731------------

Upper Devonian Stratigraphy and Structure, Western Canadian Arctic Islands: ABSTRACT

Upper Devonian strata (Melville Island Group) in the western Arctic Islands are part of a clastic wedge at least 10,000 ft thick. The strata represent the uppermost part of the Lower to Middle Paleozoic sequence of the Franklinian miogeosyncline. Three major depositional facies are recognized. (1) Marine shelf facies--interbedded green, very fine-grained, argillaceous quartz sandstone, siltstone, and shale with a few marine fossils. Organic limestones are rare. (2) High energy shoreline facies--white, fine to coarse-grained, well-sorted quartz sandstone with plant and fish remains. (3) Low energy shoreline facies--interbedded, very fine-grained, argillaceous quartz sandstone, siltstone, shale, and coal. On Bathurst and Melville Islands, the Group is divided into the Hecla Bay Formation (early to middle Frasnian) consisting mainly of high-energy shoreline facies, and the overlying Griper Bay Formation consisting of 2 informal members. The lower member (mid to late Frasnian) consists of marine shelf facies, and the upper member (early to middle Famennian) consists of high- and low-energy shoreline facies. On Prince Patrick and Banks Islands only the Griper Bay Formation is developed. Two informal members are recognized, the lower comprising the entire Frasnian stage, and the upper a part of the Famennian. The source area for the sediments is interpreted to have been a tectonic highland situated along the present western continental margin. Mississippian (Ellesmerian) deformation resulted in the development of open anticline-syncline couples and normal faults. On Bathurst and Melville Islands these structures trend east-west. In contrast, the structures trend north-south on Banks Island. This sharp bend in the Ellesmerian fold belt may be interpreted to be an orocline superimposed on the Franklinian geosyncline during the Ellesmerian orogeny. Restoration of the orocline clarifies otherwise irreconcilable facies relations in the Upper Devonian strata of the Western Arctic Islands. End_of_Article - Last_Page 2491------------

Synorogenic Quartz Sandstone in the Jurassic Mobile Belt of Western Nevada: Boyer Ranch Formation

The province of Lower Mesozoic layered rocks in western Nevada contains a diversity of marine lithologies whose deposition continued locally as late as Middle Jurassic time. At places in the province, mature quartz sandstone constitutes all or part of the highest stratigraphic units in sections of non-volcanic rocks and is believed to record the last deposition of terrigenous sediments before complete effacement of the marine basin by widespread orogeny. The sandstone was deposited early in the erogenic episode and at least locally in troughs created by folding of subjacent rocks. The sands are anomalously mature with respect to co-deposited clastic components and to coarse detrital materials in nearly all earlier Mesozoic rocks of the province. The problems are the source of the quartz sand and the reasons the sand was deposited synorogenically. The name, Boyer Ranch Formation, is formally proposed for a lithesome of homogeneous Jurassic quartz sandstone and basal conglomerate and limestone in the Dixie Valley region which is approximately in the northern third of the outcrop area of Jurassic quartz sandstone in western Nevada. The Boyer Ranch Formation contains up to 500 ft of sandstone, largely fine-grained calcareous quartz arenite, whose granulometric properties suggest eolian sorting, but whose bedding indicates quiet-water deposition. The sandstone lies above limestone and carbonate-pebble conglomerate with interstitial quartz sand. The inferred early Mesozoic geographic and tectonic histories in the Dixie Valley region suggest that the sands of the Boyer Ranch Formation accumulated at the eastern shoreline of the Mesozoic basin in western Nevada in late Early or Middle Jurassic time. Until the onset of orogeny, the sands remained unlithified, probably owing to eolian saltation, and followed a generally westerly regression of the shoreline. Postulated strong wave action prevented seaward movement of the sand. The late Early Jurassic or Middle Jurassic (or both) orogeny created local troughs which the sea reinvaded and provided an irregularly configured and low-energy shoreline environment such that movement of the sand into the water was no longer impeded. The sands may have evolved locally through the action of water and wind at the beach of the Early Mesozoic sea in western Nevada, or they may have been largely co-derived from a distant source with sands in Jurassic rocks of the eastern Cordillera and the Colorado Plateau.