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USGS2013

Identification of metrics to monitor salt marsh integrity on National Wildlife Refuges in relation to conservation and management objectives

Executive Summary Most salt marshes in the US have been degraded by human activities, and threats from physical alterations, surrounding land-use, species invasions, and global climate change persist. Salt marshes are unique and highly productive ecosystems with high intrinsic value to wildlife, and many National Wildlife Refuges (NWRs) have been established in coastal areas to protect large tracts of salt marsh and wetland-dependent species. Various management practices are employed routinely on coastal NWRs to restore and enhance marsh integrity and ensure ecosystem sustainability. Prioritizing NWR salt marshes for application of management actions and choosing among multiple management options requires scientifically-based methods for assessing marsh condition. Monitoring is integral to structured decision-making (SDM), a formal process for decomposing a decision into its essential elements. Within a natural resource context, SDM involves identifying management objectives, alternative management actions, and expected management outcomes. The core of SDM is a set of criteria for measuring system performance and evaluating management responses. Therefore, use of SDM to frame natural resource decisions leads to logical selection of monitoring attributes that are linked explicitly to management needs. We used SDM to guide selection of variables for monitoring the ecological integrity of salt marshes within the National Wildlife Refuge System (NWRS). Our objectives were to identify indicators of salt marsh integrity that are effective across large geographic regions, responsive to a wide range of threats, and feasible to implement within funding and staffing constraints of the NWRS. In April, 2008, we engaged interdisciplinary experts in a week-long rapid prototyping SDM workshop to define the essential elements of salt marsh management decisions on refuges throughout the northeastern, southwestern, and northwestern US, corresponding to respective Regions 5, 2, and 1 of the US Fish and Wildlife Service (FWS). Through this process we identified measurable attributes for monitoring salt marsh ecosystems that are integrated into conservation practice and target management objectives. The following salt marsh attributes were identified through the SDM process either for describing state condition to determine management needs or for evaluating the achievement of management objectives: historical condition and geomorphic setting; ditch density; surrounding land use; ratio of open water area to vegetation area; rate of pesticide application; environmental contaminant concentration; change in marsh surface elevation relative to sea level rise; tidal range and groundwater level; surface topography; salinity; and species composition and abundance of vegetation, invasive species, invertebrates, nekton, and breeding and wintering birds. The identified attributes were too broadly defined to serve as operational monitoring variables. Therefore, we tested specific metrics for quantifying most of these attributes in summers of 2008 and 2009. The first four attributes in the above list can be characterized by office-based analysis of existing GIS data layers. The remaining attributes require field-based methods for assessment. We were forced to exclude a small number of attributes from field tests due to inconsistent data (pesticide application rate, environmental contaminant concentrations) or requirements that exceeded the scope of this project (change in marsh surface elevation; surface topography; benthic invertebrates; wintering birds). We evaluated potential metrics for evaluating all remaining field attributes. In partnership with NWRS biologists, we tested rapid versus intensive metrics for monitoring field attributes (tidal range and groundwater level; marsh surface elevation; salinity; and species composition and abundance of vegetation, invasive species, nekton, and breeding birds) at coastal refuges throughout FWS Region 5. Seven refuges participated in metric testing in 2008: Rachel Carson (ME), Parker River (MA), Wertheim (NY), E. B. Forsythe (NJ), Bombay Hook (DE), Prime Hook (DE), and Eastern Shore of Virginia Complex (VA). These seven and two additional refuges participated in metric testing in 2009: Rhode Island Complex (RI) and Stewart B. McKinney (CT). We based all field metrics on existing protocols for salt marsh assessment. Sampling locations were determined randomly within delineated marsh study units (MSUs) at each refuge. Detailed field methods are provided in appendices to this report. Measurements for individual metrics were averaged across samples within MSUs during each year of sampling. Each year, correlation or regression analysis was conducted on average measurements across MSUs within each attribute set to identify redundant metrics. Statistical redundancy between a pair of metrics within an attribute set (i.e., correlation or regression slopes with p-values < 0.05) was considered justification for eliminating one of the pair from the regional set of monitoring metrics. Decisions regarding metric elimination versus retention were based on feasibility of monitoring, considering such factors as sampling time, resources required, and potential for regional standardization in implementation. The result of these tests is a reduced suite of monitoring metrics that targets NWRS management decisions and is practicable for implementing on a regional scale. Based on these tests, we recommend the following list of metrics for monitoring integrity of NWRS salt marshes (marsh attribute category is in parentheses): (historical condition and geomorphic setting) position of marsh in the landscape, marsh shape, degree of fill and/or fragmentation, degree of tidal flushing, amount of aquatic edge; (ditch density) ranking of ditch density from none to severe; (surrounding land use) relative proportion of agricultural land in a 150-m buffer around the marsh, relative proportion of natural land in a 150-m buffer around the marsh, relative proportion of natural land in a 1-km buffer around the marsh; (ratio of open water area to vegetation area) ratio of open water to emergent herbaceous wetlands within the marsh; (marsh surface elevation) elevation referenced to NAVD88 in a representative area of the marsh; (tidal range and groundwater level) percent of time the marsh surface is flooded during deployment of a continuous water-level monitor at a representative marsh location, mean depth of surface flooding as measured by a continuous water-level monitor at a representative location; (salinity) salinity measured in surface water; (vegetation community) vegetation species richness using the point-intercept method in 100-m diameter survey plots, percent cover of various marsh community types within 100-m diameter survey plots; (invasive species abundance) percent cover of invasive plant species measured using the point-intercept method in 100-m diameter survey plots; (nekton community) nekton density, nekton species richness, length of Fundulus heteroclitus ; (breeding bird community) abundance of Willets counted per point during standard call-broadcast surveys, summed abundance of tidal marsh obligate species (Clapper Rail, Willet, Saltmarsh Sparrow, Seaside Sparrow) counted per point during standard call-broadcast surveys. Metrics describing the historical condition, geomorphic setting, and broad landscape features can be assessed using existing GIS databases. Our results support use of rapid methods to assess the majority of field metrics; only those used to describe the nekton community must be measured using intensive methods (throw traps or ditch nets, dependant on habitat configuration). Implementation of these metrics for quantitative assessment of NWRS salt marsh integrity in FWS Region 5 requires developing sampling designs for each refuge. Additionally, it is important to determine how the monitoring information will be used within a management context. SDM should be used to complete the analysis of salt marsh management decisions. The next steps would involve 1) prioritizing and weighting the management objectives; 2) predicting responses to individual management actions in terms of objectives and metrics; 3) using multiattribute utility theory to convert all measurable attributes to a common utility scale; 4) determining the total management benefit of each action by summing utilities across objectives; and 5) maximizing the total management benefits within cost constraints for each refuge. This process would allow the optimum management decisions for NWRS salt marshes to be selected and implemented based directly on monitoring data and current understanding of marsh responses to management actions. Monitoring the outcome of management actions would then allow new monitoring data to be incorporated into subsequent decisions.

Connecticut, Delaware, Maine, Massachusetts, New J↗

USGS2022

Science mission requirements for a globally ranging, riserless drilling vessel for U.S. Scientific Ocean Drilling

Through the collection and analysis of shallow and deep subseafloor sediments, rocks, fluids, and life, scientific ocean drilling has enriched our understanding of the complex Earth system. Among other achievements, scientific ocean drilling has documented the history of Earth’s climate, the waxing and waning of polar ice sheets, the past changes in ocean and atmospheric circulation, the existence and function of microbial life in the subseafloor, the compositional variations in Earth’s crust and underlying mantle, and the physical and chemical processes acting at subduction zones, including those associated with tsunamigenic earthquakes. Over the decades, more than 12,000 articles that depend on analyses of scientific ocean drilling samples and geophysical data have been published, many detailing breakthrough contributions to global knowledge about the Earth system. Approximately 45% of these publications were led by U.S.-affiliated authors (International Ocean Discovery Program Publication Services, 2021). Since the mid-1980s, the workhorse of this multidisciplinary, international research effort has been the riserless D/V JOIDES Resolution, operated by Texas A&M University with funding from the U.S. National Science Foundation (NSF). D/V JOIDES Resolution has conducted the vast majority of scientific ocean drilling expeditions and collected most of the scientific cores over that period, including 82% of the expeditions and 93% of the cores in the last decade alone, despite being one of three platforms that is operated within the International Ocean Discovery Program. However, D/V JOIDES Resolution is approaching the end of its useful life. With a strong commitment to continue scientific ocean drilling beyond the end of the current phase, the community developed a document outlining the research frontiers that should be pursued. Exploring Earth by Scientific Ocean Drilling: 2050 Science Framework (Koppers and Coggon, 2020) describes seven scientific strategic objectives that focus on understanding interconnections within the Earth system and five flagship initiatives that integrate these objectives into long-term research efforts that address issues facing society. Additional elements in the 2050 Science Framework, including STEM education, workforce development, technology development, and innovative applications of data analytics, will advance the goals of scientific ocean drilling. Addressing the 2050 Science Framework also requires building partnerships with allied U.S. and international science programs and strengthening existing ones. To implement a significant portion of the 2050 Science Framework, the U.S. scientific community seeks to lease or acquire a newly built, globally ranging, state-of-the art, riserless drilling vessel. The many and varied technical and human resources requirements for successful accomplishment of scientific and educational goals summarized in this document and described in detail in the 2050 Science Framework require broad community input and careful consideration. Following receipt of NSF’s formal Request for Assistance to the United States Science Support Program (USSSP), the U.S. scientific ocean drilling community conducted a one-year exercise to identify its national scientific needs and priorities in order to determine the Science Mission Requirements (SMRs) presented here. This community effort included: (1) a U.S. community-wide survey to identify the specific operational and technical capabilities critical to addressing science in the 2050 Science Framework; (2) a series of online workshops focusing on critical capabilities identified by the survey; and (3) a large in-person workshop to synthesize the results of the survey and the virtual workshops (Appendix 1). The approach was designed to reach as many participants as possible. Overall, 278 survey responses were received from U.S. community members, representing 104 unique institutions from 39 states and the District of Columbia, and 137 unique individuals participated in the workshops (Appendix 2). The results of this effort comprise two classes of SMRs: Foundational Science Mission Requirements and Primary Science Mission Requirements. Foundational SMRs define minimum criteria for a new riserless drilling vessel that can address significant portions of the 2050 Science Framework. Primary SMRs build upon the Foundational SMRs and will create more robust science opportunities and data collection capabilities, will increase progress in addressing the 2050 Science Framework objectives, and will provide more real-time ship-to-shore interaction to improve science productivity, engagement, and outreach. Modern safety and environmental standards, including meeting standards to access protected waters such as exclusive economic zones, extended continental shelves, or high latitudes, while being cognizant of the vessel’s environmental footprint. Safe and efficient operations in global locations and in water depths from 70 m to 6000+ m, with total drill string length of at least 7000 m. High-quality core and data collection from a range of key subseafloor environments. Advanced heave compensation, dynamic positioning, and drill pipe stability. Modern mud and cement/casing systems. Critical onboard measurements for safety, operational decision-making, documentation of ephemeral properties, mission-specific science, and long-term science goals that extend beyond a single expedition. Designated and appropriate space for sample and data preservation. Highly skilled onboard personnel, including technical staff for curation and core handling; support for safety, time-sensitive, and critical shipboard measurements; computer support; equipment and instrument repair; application support; and data assurance. Primary Science Mission Requirements include: Flexible shipboard space for laboratories and on deck to ensure safe, successful implementation of diverse science objectives and operations. Minimizing contamination of recovered samples. Over-the-side capabilities for science-supporting technology (e.g., remotely operated vehicles, water- column sampling, sediment-water interface sampling). Downhole logging and measurements. Expanded borehole observatory capabilities. Reliable and consistent ship-to-shore communications. NSF’s investment in a new globally ranging, riserless drilling vessel will have a powerful economic multiplier effect, including the infusion of additional science support funds in the United States for training and research, the development of new technologies and tools, and the associated scientific and technical workforce development. The skills and knowledge gained through scientific ocean drilling are translatable to careers in fields such as sustainable energy development (e.g., geothermal and offshore wind), carbon sequestration, data management and cyberinfrastructure, biotechnology, communications, science education, policy, hazard mitigation, and environmental management. The United States is a leader in a well-established and internationally collaborative scientific ocean drilling community. A modern, globally ranging, riserless drilling vessel will allow the United States to expand its leadership position, address broad scientific questions that current capabilities preclude, and cultivate equitable international, multidisciplinary collaborations that will ensure scientific ocean drilling’s future success.

Report↗

USGS2014

Evaluation of the expected moments algorithm and a multiple low-outlier test for flood frequency analysis at streamgaging stations in Arizona

Flooding is among the costliest natural disasters in terms of loss of life and property in Arizona, which is why the accurate estimation of flood frequency and magnitude is crucial for proper structural design and accurate floodplain mapping. Current guidelines for flood frequency analysis in the United States are described in Bulletin 17B (B17B), yet since B17B’s publication in 1982 (Interagency Advisory Committee on Water Data, 1982), several improvements have been proposed as updates for future guidelines. Two proposed updates are the Expected Moments Algorithm (EMA) to accommodate historical and censored data, and a generalized multiple Grubbs-Beck (MGB) low-outlier test. The current guidelines use a standard Grubbs-Beck (GB) method to identify low outliers, changing the determination of the moment estimators because B17B uses a conditional probability adjustment to handle low outliers while EMA censors the low outliers. B17B and EMA estimates are identical if no historical information or censored or low outliers are present in the peak-flow data. EMA with MGB (EMA-MGB) test was compared to the standard B17B (B17B-GB) method for flood frequency analysis at 328 streamgaging stations in Arizona. The methods were compared using the relative percent difference (RPD) between annual exceedance probabilities (AEPs), goodness-of-fit assessments, random resampling procedures, and Monte Carlo simulations. The AEPs were calculated and compared using both station skew and weighted skew. Streamgaging stations were classified by U.S. Geological Survey (USGS) National Water Information System (NWIS) qualification codes, used to denote historical and censored peak-flow data, to better understand the effect that nonstandard flood information has on the flood frequency analysis for each method. Streamgaging stations were also grouped according to geographic flood regions and analyzed separately to better understand regional differences caused by physiography and climate. The B17B-GB and EMA-MGB RPD-boxplot results showed that the median RPDs across all streamgaging stations for the 10-, 1-, and 0.2-percent AEPs, computed using station skew, were approximately zero. As the AEP flow estimates decreased (that is, from 10 to 0.2 percent AEP) the variability in the RPDs increased, indicating that the AEP flow estimate was greater for EMA-MGB when compared to B17B-GB. There was only one RPD greater than 100 percent for the 10- and 1-percent AEP estimates, whereas 19 RPDs exceeded 100 percent for the 0.2-percent AEP. At streamgaging stations with low-outlier data, historical peak-flow data, or both, RPDs ranged from −84 to 262 percent for the 0.2-percent AEP flow estimate. When streamgaging stations were separated by the presence of historical peak-flow data (that is, no low outliers or censored peaks) or by low outlier peak-flow data (no historical data), the results showed that RPD variability was greatest for the 0.2-AEP flow estimates, indicating that the treatment of historical and (or) low-outlier data was different between methods and that method differences were most influential when estimating the less probable AEP flows (1, 0.5, and 0.2 percent). When regional skew information was weighted with the station skew, B17B-GB estimates were generally higher than the EMA-MGB estimates for any given AEP. This was related to the different regional skews and mean square error used in the weighting procedure for each flood frequency analysis. The B17B-GB weighted skew analysis used a more positive regional skew determined in USGS Water Supply Paper 2433 (Thomas and others, 1997), while the EMA-MGB analysis used a more negative regional skew with a lower mean square error determined from a Bayesian generalized least squares analysis. Regional groupings of streamgaging stations reflected differences in physiographic and climatic characteristics. Potentially influential low flows (PILFs) were more prevalent in arid regions of the State, and generally AEP flows were larger with EMA-MGB than with B17B-GB for gaging stations with PILFs. In most cases EMA-MGB curves would fit the largest floods more accurately than B17B-GB. In areas of the State with more baseflow, such as along the Mogollon Rim and the White Mountains, streamgaging stations generally had fewer PILFs and more positive skews, causing estimated AEP flows to be larger with B17B-GB than with EMA-MGB. The effect of including regional skew was similar for all regions, and the observed pattern was increasingly greater B17B-GB flows (more negative RPDs) with each decreasing AEP quantile. A variation on a goodness-of-fit test statistic was used to describe each method’s ability to fit the largest floods. The mean absolute percent difference between the measured peak flows and the log-Pearson Type 3 (LP3)-estimated flows, for each method, was averaged over the 90th, 75th, and 50th percentiles of peak-flow data at each site. In most percentile subsets, EMA-MGB on average had smaller differences (1 to 3 percent) between the observed and fitted value, suggesting that the EMA-MGB-LP3 distribution is fitting the observed peak-flow data more precisely than B17B-GB. The smallest EMA-MGB percent differences occurred for the greatest 10 percent (90th percentile) of the peak-flow data. When stations were analyzed by USGS NWIS peak flow qualification code groups, the stations with historical peak flows and no low outliers had average percent differences as high as 11 percent greater for B17B-GB, indicating that EMA-MGB utilized the historical information to fit the largest observed floods more accurately. A resampling procedure was used in which 1,000 random subsamples were drawn, each comprising one-half of the observed data. An LP3 distribution was fit to each subsample using B17B-GB and EMA-MGB methods, and the predicted 1-percent AEP flows were compared to those generated from distributions fit to the entire dataset. With station skew, the two methods were similar in the median percent difference, but with weighted skew EMA-MGB estimates were generally better. At two gages where B17B-GB appeared to perform better, a large number of peak flows were deemed to be PILFs by the MGB test, although they did not appear to depart significantly from the trend of the data (step or dogleg appearance). At two gages where EMA-MGB performed better, the MGB identified several PILFs that were affecting the fitted distribution of the B17B-GB method. Monte Carlo simulations were run for the LP3 distribution using different skews and with different assumptions about the expected number of historical peaks. The primary benefit of running Monte Carlo simulations is that the underlying distribution statistics are known, meaning that the true 1-percent AEP is known. The results showed that EMA-MGB performed as well or better in situations where the LP3 distribution had a zero or positive skew and historical information. When the skew for the LP3 distribution was negative, EMA-MGB performed significantly better than B17B-GB and EMA-MGB estimates were less biased by more closely estimating the true 1-percent AEP for 1, 2, and 10 historical flood scenarios.

Arizona↗

USGS1950

Geology and paleontology of the Santa Maria district, California

Stratigraphy, paleontology, and geologic history.-A basement' consisting of igneous rocks of the Jurassic(?) Franciscan formation and sediments of the Upper Jurassic Knoxville formation, and formations of Tertiary and Quaternary age are exposed in the Santa Maria district. The outcrop section, exclusive of the Franciscan, has a maximum thickness of about 10,000 feet, the subsurface section about 27,000 feet. At no locality, however, is either outcrop or subsurface section as thick as the total maxima for the formations. The outcrop Franciscan is made up of altered basalt, gabbro (generally- greatly altered), and minor areas of peridotite and serpentine. The marine Knoxville formation, consisting of shale, thin-bedded calcareous sandstone, and conglomerate, was deposited on the igneous rocks of the Franciscan. It has an outcrop thickness of about 500 feet and a known subsurface thickness of at least 1,250 feet. Aucella cf. A. piochii, which occurs in both outcrop and subsurface sections, suggests late Jurassic age. The Franciscan and Knoxville were probably uplifted during Taliaferro's Diablan orogeny at the close of the Jurassic and formed a land area that presumably endured during early Cretaceous and perhaps during much of late Cretaceous time. If sediments were laid down while 10,000 feet of Upper Cretaceous were deposited in the adjoining San Rafael Mountains, they were eroded following uplift at the close of the Cretaceous, when Reed and Hollister's San Rafael uplift was formed. The district is inferred to have been part of a Franciscan and Knoxville land area at the south border of the San Rafael uplift during all of early Tertiary time. The known history of the district as part of a Tertiary basin began in the early Miocene(?), possibly a little earlier or possibly 3: little later, when the nonmarine sediments of the early Miocene(?) Lospe formation were deposited. The Lospe formation has a maximum thickness of 2, 700 feet, and is made up of coarse-grained reddish sandstone and conglomerate, and greenish sandstone, gypsiferous siltstone, and mudstone. White tuff is a minor but conspicuous constituent. The Lospe formation overlies the Knoxville, or· overlaps it and rests on the Franciscan. The first known Tertiary invasion of the sea took place immediately thereafter in early middle Miocene time, and from then on until approximately the end of the Pliocene the sea occupied continuously at least most of the region. The extent of the Miocene basin is not certainly known, but it was part of an extensive· basin that has been designated the Santa Barbara embayment. The early middle Miocene Point Sal formation is the earliest marine Tertiary formation. It has an outcrop thickness of as much as 1,500 feet and a maximum subsurface thickness of 3,600 feet, and consists of siltstone, mudstone, and thin beds of sandstone. The Point Sal formation overlies the Lospe formation without marked discontinuity, or overlaps it and rests on Knoxville or Franciscan. It contains a large foraminiferal fauna representing the Siphogenerina hughesi zone, or the lower part of Kleinpell's Relizian stage. The Monterey shale overlies the Point Sal formation without noticeable discontinuity, or overlaps all the older sedimentary formations and rests on the Franciscan. It has a maximum outcrop thickness of 2,100 feet, but is as much as 5,000 feet thick in some subsurface sections. The Monterey is divided into three mapped members. The lower member is characterized by phosphatic shale and somewhat porcelaneous shale; the middle member by chert and cherty shale; and the upper member by porcelaneous shale, or by both porcelaneous shale and diatomaceous strata. The lower member contains Foraminifera representing the upper part of Kleinpell's Relizian stage and all of his Luisian stage, the middle member a few species indicating the lower part of his Mohnian stage, and the upper member a fauna representing the upper part of the Bolivina hughesi zone, at the top of the Mohnian, and in part a younger unnamed faunal division; that is, the Monterey is of late middle and late Miocene age. The diverse stratigraphic relations of the Lospe and Point Sal formations and Monterey shale along the borders of the Franciscan rocks forming Point Sal Ridge are inferred to be the result of repeated movements during Miocene time in the area of basement rocks west of the district, presumably extending westward beyond the present coast. Toward the close of the Miocene, low ridges appeared on the floor of the sea, ridges that grew during Pliocene time and were destined to become anticlines. At the same time deformation took place in the northeastern part of the district, and elsewhere on some anticlines, or on other structural highs bounded by faults. In those areas the Sisquoc formation overlies the Monterey shale with marked discordance; elsewhere there is no discordance. Two facies of the Sisquoc formation are mapped: a marginal sandstone facies, designated the Tinaquaic sandstone member, and a basin facies. The Tinaquaic sandstone member is 1,400 feet thick and contains megafossils of middle Pliocene age (also early Pliocene just east of the mapped area). It is unconformable on the Monterey. The basin facies, at least 3,000 feet thick in outcrop sections and 5,000 in some subsurface sections, consists of diatomaceous mudstone, other types of diatomaceous ·strata, somewhat porcelaneous mudstone, and porcelaneous shale-deposits that are ordinarily characteristic of the Monterey shale. Even in areas where the two formations are lithologically indistinguishable and conformable, a field basis for differentiating them has been established. The basin facies of the Sisquoc conformably overlies the Monter.ey in outcrop sections, but in some subsurface sections the formations are unconformable, and on the north limb of the Santa Maria Valley syncline the basin facies of the Sisquoc overlaps the Monterey onto the basement, thus forming the overlap trap for the oil in the Monterey in the Santa Maria Valley field. The lower and middle parts of the basin facies contain Foraminifera of the Bolivina obliqua zone. Kleinpell assigned that zone to the lower part of his late upper Miocene Delmontian stage. Assignment to the upper Delmontian, however, appears to be preferable. The upper few hundred feet of the basin facies contain Foraminifera similar to those in the overlying Foxen mudstone and megafossils of middle Pliocene affinities. The basin facies is therefore considered late upper Miocene to middle Pliocene. The submarine ridges were growing during Pilocene time. The Foxen mudstone is missing on them and in the northeastern part of the district. On the north limb of the Santa Maria Valley syncline, the Foxen overlaps the Sisquoc formation and rests on the basement. In the basins between the submarine ridges, the mudstone, siltstone, and fine-grained sandstone of the Foxen (800 feet thick in outcrop sections and as much as 2, 750 in subsurface sections) overlie conformably the Sisquoc formation. In some of the areas where the Foxen is missing as a lithologic unit, it appears to be represented by condensed deposits of phosphatic pellets, mapped with the underlying or overlying Formation, depending on the matrix, or by a condensed section of fine-grained sand, mapped with lithologically indistinguishable sand in the basal part of the overlying formation. Though foraminifera are abundant in the Foxen mudstone, relatively few species are represented. Those from the lower part of the formation may be of middle Pliocene age. Megafossils from the upper part of the Foxen are considered late Pliocene. The formation is therefore assigned to the middle(?) and upper Pliocene. Movements during Pliocene time in the basement area west of Point Sal Ridge are indicated by the occurrence in the western Casmalia Hills of coarse detritus from the Monterey in the upper part of the Sisquoc formation and in the Foxen mudstone. During late Pliocene time, when the Careaga sandstone was deposited, the Pliocene sea had its greatest extent. The region then flooded may be referred to as the Santa Maria basin. Throughout most of the district two mapped members of the Careaga sandstone are differentiated: the Cebada fine-grained member, which has a maximum outcrop thickness of 1,000 feet, and the Graciosa coarse-grained member, 50 to 425 feet thick. Mild deformation continued during the late Pliocene. The Cebada fine-grained member is missing on the embryonic anticlines, where it is overlapped by the Graciosa coarse-grained member. Both members of the Careaga sandstone contain a large megafauna. The nonmarine Paso Robles formation conformably overlies the Careaga sandstone. The Paso Robles consists chiefly of sand and gravel, but clay, marl, and limestone are the most characteristic constituents. The maximum outcrop thickness is 2,000 feet, the estimated maximum subsurface thickness 4,500 feet. The Paso Robles fresh-water fauna is meager, consisting of a few species similar to living forms. The formation is currently assigned to the interval including late Pliocene and early Pleistocene(?). The age assignment late Pliocene(?) and early Pleistocene, however, may be preferable for the Santa Maria district. Then followed the only period of strong general deformation in the known Tertiary and Pleistocene history of the district. The present structural features of the district were formed at that time, and the submarine ridges appeared as fully formed anticlines. Dating of the deformation is uncertain, because of uncertainty concerning the age of the Paso Robles formation. It is, however, without much doubt of the same age as the welldated strong middle Pleistocene deformation in the Ventura basin. Terrace deposits, laid down on both wave-cut and stream-cut platforms, are rather arbitrarily assigned to the late Pleistocene. The oldest and most extensive terrace deposits, not more than 100 feet thick, are designated the Orcutt sand. The Orcutt sand itself is tilted as much as 12° on the limbs of anticlines and is faulted on the north limb of the Graciosa anticline, indicating renewed growth of the anticlines, presumably in late Pleistocene time. Terrace deposits apparently younger than the Orcutt sand are arched in a low anticline west of lower Foxen Canyon. Structure.-Santa Maria Valley is the boundary between two structural provinces. To the north, valleys and hills are either synclines or anticlines. To the south, on the contrary, major valleys coincide generally with major synclines, and the hills are anticlinal. Santa Maria Valley itself is a syncline. Unlike valleys farther south in the district, however, it lies athwart an older uplift. Also unlike most of the valleys farther south, the axis of the syncline is not in the middle of the valley, but is far to the south near the bordering hills. Indeed, in the western Casmalia Hills, the anticline in the bordering hills is overturned and overrides the axis of the syncline. The major structural features of the district have a general west-northwestward trend parallel to the trend of the basin. Minor westward-trending and northward-trending folds and faults, however, extend across the trend of the major features. The district includes areas of wide, open folds and also areas of narrow, closely spaced, and steeply tilted folds, as well as some major overturned anticlines, most of the latter overturned northward. The closely spaced folds coincide almost invariably with outcrops of the Monterey shale and Point Sal formation. Physiography.-The surface on which the terrace deposits, designated the Orcutt sand, were deposited is extensive but is locally deformed, and only remnants are preserved. Toward the coast it changes from a stream-cut surface to a wave-cut surface. In the coastal area three main marine terraces are recognized: the high terrace (altitude about 800 feet), the intermediate terrace (altitude about 600 feet), and the low terrace (altitude 50 to 125 feet). An indurated layer is present at or near the surface at many localities scattered throughout the district. It is suggested that the indurated layer is an ancient hardpan, the incomplete skeleton of a former soil profile developed on a former surface of less relief than the present surface. Sand dunes extend inland from the coast at the north and south borders of the mapped area. They are classified under three age groups: old, intermediate, and modern. The old dunes, which have a protective cover of natural vegetation and are now inactive, are far more extensive than those of the other two groups. They cover many square miles on a terrace bordering Santa Maria Valley, and extend 20 miles inland. It has not been determined whether their inactivity is due to a cutting off of the supply of sand, or to a climatic change. Occurrence of oil.--Oil has been produced in the Santa Maria district since 1901, the total production to the end of 1947 being 269,657,000 barrels. Throughout the district most of the oil is heavy. Seven producing fields are located in the mapped area. In order of discovery from oldest to youngest the fields are as follows: Orcutt, Lompoc, West Cat Canyon, East Cat Canyon, Casmalia, Gato Ridge, and Santa Maria Valley. The Santa Maria Valley field is the largest in both area and productive capacity. It is the largest overlap field in coastal California, and one of the last major fields found in the State up to 1947. The Las Flores (Monterey) pool is transforming the West Cat Canyon field into one of the major fields of the district. The Monterey shale is the chief oil-bearing formation, and the principal reservoir in the Monterey consists of fractured chert and cherty shale. Sand in the Sisquoc formation is the sole reservoir in the minor East Cat Canyon field and in the Pliocene pool of the West Cat Canyon field. The Point Sal formation yields some oil in the southeastern part of the Santa Maria Valley field (the only part of that field where the formation is present) and a recent well in the Casmalia field is producing a small amount of relatively light oil from the Point Sal. The Lospe formation is also productive in a recent well in the Casmalia field. The Knoxville formation is productive in three areas in the northern part of the Santa Maria Valley field. The Point Sal formation offers the greatest promise for deeper-zone production. The Lospe and Knoxville formations can no longer be ignored in areas where younger marine formations overlap against them. Oil possibilities in undeveloped areas.--Two matters weigh heavily in prospecting in the Santa Maria district: the degree of fracturing of chert and cherty shale in the Monterey shale, and the gravity of the oil. Other things being equal, the productivity of the Monterey varies directly with the amount of fracturing. Very heavy oil, too heavy to produce commercially under present conditions, has befln found ii the Monterey in the northeastern part of the district, where five discoveries (one east of the mapped area) have been made in recent years. Among areas of possible interest, three appear to be favorable for prospecting on the basis of surface geology: an area east of Foxen Canyon, where oil may be trapped in the basal part of the Tinaquaic sandstone member of the Sisquoc formation by westward overlap of successively higher Tinaquaic strata onto the Monterey shale; an area so1tth of the I ... ions Head fault, where oil may be trapped by the fault; and the offshore extension of the north border of Point Sal Ridge, where oil may possibly be trapped in the Monterey by overlap of the Sisquoc formation.

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