Geology Commons^™

Impacts Of Environmental Conditions On Fleas In Black-Tailed Prairie Dog Burrows, Julia E. Poje, Tonie Rocke, Michael D. Samuel

United States Geological Survey: Staff Publications

Sylvatic plague, caused by the bacterium Yersinia pestis and transmitted by fleas, occurs in prairie dogs of the western United States. Outbreaks can devastate prairie dog communities, often causing nearly 100% mortality. Three competent flea vectors, prairie dog specialists Oropsylla hirsuta and O. tuberculata, and generalist Pulex simulans, are found on prairie dogs and in their burrows. Fleas are affected by climate, which varies across the range of black-tailed prairie dogs (Cynomys ludovicianus), but these effects may be ameliorated somewhat due to the burrowing habits of prairie dogs. Our goal was to assess how temperature and precipitation …

Interpretation Of Hydrogeologic Data To Support Groundwater Management, Bazile Groundwater Management Area, Northeast Nebraska, 2019—A Case Demonstration Of The Nebraska Geocloud, Christopher M. Hobza, Gregory V. Steele

Publications of the US Geological Survey

Nitrate, age tracer, and continuous groundwater-level data were interpreted in conjunction with airborne electromagnetic (AEM) survey data to understand the movement of nitrate within the Bazile Groundwater Management Area (BGMA) in northeastern Nebraska. Previously published age tracer data and nitrate data indicated vertical stratification of groundwater quality. Younger groundwater sampled within shallow parts of the aquifer had higher concentrations of nitrate, with 70 percent exceeding the U.S. Environmental Protection Agency maximum contaminant level of 10 milligrams per liter. In contrast, groundwater sampled from deeper parts of the aquifer indicated that nitrate concentrations were less than 2 milligrams per liter and …

The Role Of Eolian-Fluvial Interactions And Dune Dams In Landscape Change, Late Pleistocene-Holocene, Mojave Desert, Usa, Mark R. Sweeney, Eric V. Mcdonald, Lucas P. Chabela, Paul R. Hanson

School of Natural Resources: Faculty Publications

The formation of the Kelso Dunes in the eastern Mojave Desert, California, was a landscape-changing event triggered by an increase in sediment supply that followed the incision of Afton Canyon by the Mojave River ca. 25 ka. Eastward migration of sand dunes occurred along a well-defined eolian trans­port corridor. Dunes temporarily blocked washes resulting in substantial aggradation of eolian and fluvial sediments. Stratigraphic exposures reveal numerous fining-up sequences with interbedded eolian sands that provide evidence of dune dams and subsequent aggradation. Luminescence ages reveal that dune blocking and aggradation correspond to a regional pulse of alluvial fan sedimentation that occurred …

Implementation Of An Occupancy-Based Monitoring Protocol For A Widespread And Cryptic Species, The New England Cottontail (Sylvilagus Transitionalis), Colin P. Shea, Mitchell J. Eaton, Darryl I. Mackenzie

United States Geological Survey: Staff Publications

Context. Designing effective long-term monitoring strategies is essential for managing wildlife populations. Implementing a cost-effective, practical monitoring program is especially challenging for widespread but locally rare species. Early successional habitat preferred by the New England cottontail (NEC) has become increasingly rare and fragmented, resulting in substantial declines from their peak distribution in the mid-1900s. The introduction of a possible competitor species, the eastern cottontail (EC),may also have played a role. Uncertainty surrounding how these factors have contributed to NEC declines has complicated management and necessitated development of an appropriate monitoring framework to understand possible drivers of distribution and dynamics.

Aims. …

Tributes To Rick Edwards Upon His Retirement, Robert F. Diffendal Jr., Michael Farrell, Michael David Forsberg, Maurice Godfrey, John J. Janovy Jr., Katie Nieland, Linda Pratt, Rebecca S Wingo, David J. Wishart, George E. Wolf, Peter Longo, John R. Wunder

Robert F. Diffendal, Jr., Publications

I understand that you will be retiring from UNL in August. I wanted to express my sadness that you will be leaving the Center for Great Plains Studies, but am glad that you will now be able to perhaps enjoy life even more without having to do the administrative tasks that go with being the director of any organization. (RFD)

Repetitive Sampling And Control Threshold Improve 16s Rrna Gene Sequencing Results From Produced Waters Associated With Hydraulically Fractured Shale, Jenna L. Shelton, Elliott P. Barnhart, Leslie Ruppert, Aaron M. Jubb, Madalyn S. Blondes, Christina A. Devera

United States Geological Survey: Staff Publications

Sequencing microbial DNA from deep subsurface environments is complicated by a number of issues ranging from contamination to non-reproducible results. Many samples obtained from these environments – which are of great interest due to the potential to stimulate microbial methane generation – contain low biomass. Therefore, samples from these environments are difficult to study as sequencing results can be easily impacted by contamination. In this case, the low amount of sample biomass may be effectively swamped by the contaminating DNA and generate misleading results. Additionally, performing field work in these environments can be difficult, as researchers generally have limited access …

Evaluating Airsoft Electric Guns For Control Of Invasive Brown Treesnakes, Adam J. Knox, Björn Lardner, Amy Yackel Adams, Robert N. Reed

United States Geological Survey: Staff Publications

Firearms are often used in lethal control of invasive vertebrates, but safety and regulatory aspects limit the circumstances under which they can be used. During August 2016 at the Brown Treesnake Project laboratory on Guam, we evaluated hobby‐grade Airsoft Electric Guns (AEGs; a lower powered, less‐hazardous, and less‐regulated alternative to firearms) for capture and control of small animals, with specific emphasis on invasive brown treesnakes (Boiga irregularis). Tests of AEGs differing in power with ammunition (plastic pellets) masses ranging from 0.20 to 0.39 g, fired at gelatin blocks from distances of 4, 8, and 12 m, showed that …

Characterizing Peridotite Xenoliths From Southern Vietnam: Insight Into The Underlying Lithospheric Mantle, Kirby Hobbs

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Extrusion tectonics has been invoked to explain the extensive basaltic magmatism that has erupted over Indochina within the last 17 Ma. The basalts display two-stage eruptive cycles consisting of tholeiites followed by alkaline basalts. Lithospheric mantle xenoliths recently sampled from the alkaline basalts of two volcanic centers, Pleiku and Xuan Loc, primarily consist of fertile spinel lherzolites, and Xuan Loc also contains refractory spinel harzburgites. We measured major elements in xenolith mineral separates, trace elements in clinopyroxenes and orthopyroxenes, and Pb-Sr-Nd isotopic compositions in clinopyroxenes to determine the origin and history of the subcontinental lithospheric mantle (SCLM) beneath Vietnam. Most …

Adjusting The Lens Of Invasion Biology To Focus On The Impacts Of Climate-Driven Range Shifts, Piper D. Wallingford, Toni Lyn Morelli, Jenica M. Allen, Evelyn M. Beaury, Dana M. Blumenthal, Bethany A. Bradley, Jeffrey S. Dukes, Regan Early, Emily J. Fusco, Deborah E. Goldberg, Inés Ibáñez, Brittany B. Laginhas, Montserrat Vilà, Cascade J.B. Sorte

United States Geological Survey: Staff Publications

As Earth’s climate rapidly changes, species range shifts are considered key to species persistence. However, some range-shifting species will alter community structure and ecosystem processes. By adapting existing invasion risk assessment frameworks, we can identify characteristics shared with high-impact introductions and thus predict potential impacts. There are fundamental differences between introduced and range-shifting species, primarily shared evolutionary histories between range shifters and their new community. Nevertheless, impacts can occur via analogous mechanisms, such as wide dispersal, community disturbance and low biotic resistance. As ranges shift in response to climate change, we have an opportunity to develop plans to facilitate advantageous …

Increased Drought Severity Tracks Warming In The United States’ Largest River Basin, Justin T. Martin, Gregory T. Pederson, Connie A. Woodhouse, Edward R. Cook, Gregory J. Mccabe, Kevin J. Anchukaitis, Erika K. Wise, Patrick J. Erger, Larry Dolan, Marketa Mcguire, Subhrendu Gangopadhyay, Katherine J. Chase, Jeremy S. Litell, Stephen T. Gray, Scott St. George, Jonathan M. Friedman, David J. Sauchyn, Jeannine-Marie St-Jacques, John King

United States Geological Survey: Staff Publications

Across the Upper Missouri River Basin, the recent drought of 2000 to 2010, known as the “turn-of-the-century drought,” was likely more severe than any in the instrumental record including the Dust Bowl drought. However, until now, adequate proxy records needed to better understand this event with regard to long-term variability have been lacking. Here we examine 1,200 y of streamflow from a network of 17 new tree-ring–based reconstructions for gages across the upper Missouri basin and an independent reconstruction of warm-season regional temperature in order to place the recent drought in a long-term climate context. We find that temperature has …

Testing A Drone-Based Magnetic Field Surveying System, Erik Jacobson, Irina Filina

UCARE Research Products

Aeromagnetic surveys are conducted by geoscientists to study subsurface geologic structures, such as faults. This type of survey uses a magnetometer mounted upon an airborne vehicle to collect magnetic field data. Magnetic anomalies are caused by variations in subsurface geology, namely in magnetic properties of subsurface rocks. Jacobson and Filina (2019) reported on the development of a new low cost drone, based magnetic field surveying system by the UNL Geophysics Team. This drone-based magnetic system is capable of collecting high resolution data at low speeds and low altitudes. The current study focuses on testing this system by conducting two flights …

Nebraska Statewide Groundwater-Level Monitoring Report 2019, Aaron R. Young, Mark E. Burbach, Leslie M. Howard, Sue Olafsen Lackey, Robert Matthew Joeckel

Conservation and Survey Division

The term “groundwater” has come to be all but synonymous with Nebraska. Nearly three-quarters of the total volume of the High Plains Aquifer lies beneath the State. Groundwater maintains our streams, our ecosystems, our people, and our vitally important agricultural economy. Nebraska’s total groundwater resource is vast, yet it is also vulnerable to natural and anthropogenic changes, necessitating a long-term commitment to wise management through informed decision making. Monitoring, studying, and reporting form the essential basis for such management and, ultimately, for meeting the myriad challenges presented by change.

The personnel of the Conservation and Survey Division (CSD) are proud …

Evaluation Of The Potential Geological And Socioeconomic Impacts Of The Imminent Cascadia Megathrust Earthquake, Matthew Pritchard

Honors Theses

The Cascadia Subduction Zone on the northwest coast of the United States poses the threat of a devastating megathrust earthquake and subsequent tsunami damaging coastal populations. This paper synthesizes literature to analyze the geologic and socioeconomic effects of this natural disaster, as well as examines the existing warning system infrastructure, and makes recommendations to mitigate the damage. In order to assess the geologic effects of a megathrust earthquake, I investigate the tectonic history, the role of episodic tremor and slip (ETS) in stress buildup, crustal architecture of the subduction zone, and analogous subduction zones such as Chile and Japan. This …

Groundwater Quality In The High Plains Aquifer

Publications of the US Geological Survey

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water. The High Plains aquifer constitutes one of the important aquifers being evaluated.

The High Plains aquifer underlies an area of about 169,000 square miles, which is populated by about 2 million people in parts of eight western states (Colorado, Kansas, Nebraska, New Mexico, Oklahoma, Texas, South Dakota, and Wyoming). The aquifer ranks 13th in the Nation as a source of groundwater for …

Hydrogeologic Framework And Water Balance Investigation Of Land Near The Gothenburg Canal System, Douglas R. Hallum

Conservation and Survey Division

The Nebraska Public Power District (NPPD) requested that Conservation and Survey Division (CSD) develop a local hydrogeologic framework and conceptual water budget for a parcel of land near a segment of canal in the Gothenburg Canal System to determine likely sources of ponded surface water that are ephemerally present on the parcel. The study seeks to assess the parcel scale water budget and to better understand the parcel-scale hydrology and hydrogeology. The object of this project is to provide reliable information to NPPD and its customers along a small portion of the canal. Information from this report may influence, or …

Mapping The Base Of The High Plains Aquifer Using Borehole Geophysical Logs And Airborne Electromagnetic Surveys In Western Nebraska, Steven S. Sibray, Douglas R. Hallum, Joseph Reedy, Jason Yuill, Thadeus Kuntz

Conservation and Survey Division

The project scanned and reviewed data from 15,421 oil and gas well geophysical logs in 13 counties to delineate the base of aquifer and thickness of the High Plains Aquifer (HPA). The data and interpretations from this study can be used in a regional groundwater modeling effort that includes the Western Water Use Management Modeling (WWUMM) and the and the Cooperative Hydrology Study (COHYST) model. The area studied is in the Upper Platte River Basin. The Nebraska Department of Natural Resources (NeDNR) has designated most of the area as either overappropriated or fully appropriated, where groundwater is managed jointly

by …

Chronology Of Advance And Recession Dynamics Of The Southern Green Bay Lobe Of The Laurentide Ice Sheet, South-Central Wisconsin, Usa, Eric C. Carson, John W. Attig, J. Elmo Rawling Iii, Paul R. Hanson, Stefanie E. Dodge

School of Natural Resources: Faculty Publications

We used a combination of accelerator mass spectrometry (AMS) radiocarbon dating, optically stimulated luminescence (OSL) age estimates, and stratigraphic data from cores collected along the southern margin of the Green Bay Lobe (GBL) of the Laurentide Ice Sheet to provide new information on the timing and dynamics of the end of advance of the GBL and the dynamics of the ice sheet while very near its maximum position. Coring at multiple sites along the margin of the GBL indicate that ice had reached a stable position near its maximum extent by 24.7 ka; that ice advanced several kilometers to the …

Estimating Abiotic Thresholds For Sagebrush Condition Class In The Western United States, Stephen Boyte, Bruce K. Wylie, Yingxin Gu, Donald J. Major

United States Geological Survey: Staff Publications

Sagebrush ecosystems of the western United States can transition from extended periods of relatively stable conditions to rapid ecological change if acute disturbances occur. Areas dominated by native sagebrush can transition from species-rich native systems to altered states where non-native annual grasses dominate, if resistance to annual grasses is low. The non-native annual grasses provide relatively little value to wildlife, livestock, and humans and function as fuel that increases fire frequency. The more land area covered by annual grasses, the higher the potential for fire, thus reducing the potential for native vegetation to reestablish, even when applying restoration treatments. Mapping …

Testing Glacial Isostatic Adjustment Models Of Last-Interglacial Sea Level History In The Bahamas And Bermuda, Daniel R. Muhs, Kathleen R. Simmons, R. Randall Schumann, Eugene S. Schweig, Mark P. Rowe

United States Geological Survey: Staff Publications

Part of the spatial variation in the apparent sea-level record of the last interglacial (LIG) period is due to the diverse response of coastlines to glacial isostatic adjustment (GIA) processes, particularly where coastlines were close to the Laurentide Ice Sheet during the past two glacial periods. We tested modeled LIG paleo-sea levels on New Providence Island (NPI), Bahamas and Bermuda by investigating emergent coral patch reefs and oolitic/peloidal beach deposits. Corals with closed-system histories collected from patch reefs on NPI have ages of 128-118 ka and ooids/peloids from beach ridges have closed-system ages of 128-116 ka. Elevations of patch reefs …

Uptake, Metabolism, And Elimination Of Fungicides From Coated Wheat Seeds In Japanese Quail (Coturnix Japonica), Michael S. Gross, Thomas G. Bean, Michelle L. Hladik, Barnett A. Rattner, Kathryn M. Kuivila

United States Geological Survey: Staff Publications

Pesticides coated to the seed surface potentially pose an ecological risk to granivorous birds that consume incompletely buried or spilled seeds. To assess the toxicokinetics of seeds treated with current-use fungicides, Japanese quail ( Coturnix japonica) were orally dosed with commercially coated wheat seeds. Quail were exposed to metalaxyl, tebuconazole, and fludioxonil at either a low dose (0.0655, 0.0308, and 0.0328 mg/kg of body weight, respectively) or a high dose (0.196, 0.0925, and 0.0985 mg/kg of body weight, respectively). Fungicides were rapidly absorbed and distributed to tissues. Tebuconazole was metabolized into tert-butylhydroxy-tebuconazole. All compounds were eliminated to below detection limits …

Acoustic Space Occupancy: Combining Ecoacoustics And Lidar To Model Biodiversity Variation And Detection Bias Across Heterogeneous Landscapes, Danielle I. Rappaport, J. Andrew Royle, Douglas C. Morton

United States Geological Survey: Staff Publications

There is global interest in quantifying changing biodiversity in human-modified landscapes. Ecoacoustics may offer a promising pathway for supporting multi-taxa monitoring, but its scalability has been hampered by the sonic complexity of biodiverse ecosystems and the imperfect detectability of animal-generated sounds. The acoustic signature of a habitat, or soundscape, contains information about multiple taxa and may circumvent species identification, but robust statistical technology for characterizing community-level attributes is lacking. Here, we present the Acoustic Space Occupancy Model, a flexible hierarchical framework designed to account for detection artifacts from acoustic surveys in order to model biologically relevant variation in acoustic space …

Uptake, Metabolism, And Elimination Of Fungicides From Coated Wheat Seeds In Japanese Quail (Coturnix Japonica), Michael S. Gross, Thomas G. Bean, Michelle L. Hladik, Barnett A. Rattner, Kathryn M. Kuivila

United States Geological Survey: Staff Publications

Pesticides coated to the seed surface potentially pose an ecological risk to granivorous birds that consume incompletely buried or spilled seeds. To assess the toxicokinetics of seeds treated with current-use fungicides, Japanese quail ( Coturnix japonica) were orally dosed with commercially coated wheat seeds. Quail were exposed to metalaxyl, tebuconazole, and fludioxonil at either a low dose (0.0655, 0.0308, and 0.0328 mg/kg of body weight, respectively) or a high dose (0.196, 0.0925, and 0.0985 mg/kg of body weight, respectively). Fungicides were rapidly absorbed and distributed to tissues. Tebuconazole was metabolized into tert-butylhydroxy-tebuconazole. All compounds were eliminated to below detection limits …

Characterization Of Pallid Sturgeon (Scaphirhynchus Albus) Spawning Habitat In The Lower Missouri River, Caroline M. Elliott, Aaron J. Delonay, Kimberly Chojnacki, Robert B. Jacobson

United States Geological Survey: Staff Publications

Acipenseriformes (sturgeons and paddlefish) globally have declined throughout their range due to river fragmentation, habitat loss, overfishing, and degradation of water quality. In North America, pallid sturgeon (Scaphirhynchus albus) populations have experienced poor to no recruitment, or substantial levels of hybridization with the closely related shovelnose sturgeon (S. platorynchus). The Lower Missouri River is the only portion of the species’ range where successful reproduction and recruitment of genetically pure pallid sturgeon have been documented. This paper documents spawning habitat and behavior on the Lower Missouri River, which comprises over 1,300 km of unfragmented river habitat. The …

Human-Associated Species Dominate Passerine Communities Across The United States, Helen R. Sofaer, Curtis H. Flather, Catherine S. Jarnevich, Kristin P. Davis, Liba Pejchar

United States Geological Survey: Staff Publications

Aim: Human development and agriculture can have transformative and homogenizing effects on natural systems, shifting the composition of ecological communities towards non-native and native species that tolerate or thrive under human-dominated conditions. These impacts cannot be fully captured by summarizing species presence, as they include dramatic changes to patterns of species abundance. However, how human land use patterns and species invasions intersect to shape patterns of abundance and dominance within ecological communities is poorly understood even in well-known taxa.

Location: Conterminous United States.

Time period: 2010–2012.

Major taxa studied: Passeriformes.

Methods: We analyse continental-scale monitoring data to study the proportional …

Ecosystem Processes, Land Cover, Climate, And Human Settlement Shape Dynamic Distributions For Golden Eagle Across The Western Us, J.D. Tack, Barry R. Noon, Zachary Bowen, Brad C. Fedy

United States Geological Survey: Staff Publications

Species–environment relationships for highly mobile species outside of the breeding season are often highly dynamic in response to the collective effects of everchanging climatic conditions, food resources, and anthropogenic disturbance. Capturing dynamic space-use patterns in a model-based framework is critical as model inference often drives place-based conservation planning. We applied dynamic occupancy models to broad-scale golden eagle Aquila chrysaetos survey data collected annually from 2006 to 2012 during the late summer post-fledging period in the western US. We defined survey sites as 10 km transect segments with a 1 km buffer on either transect side (n = 3540). Derived estimates …

Human-Associated Species Dominate Passerine Communities Across The United States, Helen R. Sofaer, Curtis H. Flather, Catherine S. Jarnevich, Kristin P. Davis

United States Geological Survey: Staff Publications

Aim: Human development and agriculture can have transformative and homogenizing effects on natural systems, shifting the composition of ecological communities towards non-native and native species that tolerate or thrive under human-dominated conditions. These impacts cannot be fully captured by summarizing species presence, as they include dramatic changes to patterns of species abundance. However, how human land use patterns and species invasions intersect to shape patterns of abundance and dominance within ecological communities is poorly understood even in well-known taxa.

Location: Conterminous United States.

Time period: 2010–2012.

Major taxa studied: Passeriformes.

Methods: We analyse continental-scale monitoring data to study the proportional …

Acoustic Space Occupancy: Combining Ecoacoustics And Lidar To Model Biodiversity Variation And Detection Bias Across Heterogeneous Landscapes, Danielle I. Rappaport, J. Andrew Royle, Douglas C. Morton

United States Geological Survey: Staff Publications

There is global interest in quantifying changing biodiversity in human-modified landscapes. Ecoacoustics may offer a promising pathway for supporting multi-taxa monitoring, but its scalability has been hampered by the sonic complexity of biodiverse ecosystems and the imperfect detectability of animal-generated sounds. The acoustic signature of a habitat, or soundscape, contains information about multiple taxa and may circumvent species identification, but robust statistical technology for characterizing community-level attributes is lacking. Here, we present the Acoustic Space Occupancy Model, a flexible hierarchical framework designed to account for detection artifacts from acoustic surveys in order to model biologically relevant variation in acoustic space …

Adjusting The Lens Of Invasion Biology To Focus On The Impacts Of Climate-Driven Range Shifts, Piper D. Wallingford, Toni Lyn Morelli, Jenica M. Allen, Evelyn M. Beaury, Dana M. Blumenthal, Bethany A. Bradley, Jeffrey S. Dukes, Regan Early, Emily J. Fusco, Deborah E. Goldberg, Inés Ibáñez, Brittany B. Laginhas, Montserrat Vilà, Cascade J.B. Sorte

United States Geological Survey: Staff Publications

As Earth’s climate rapidly changes, species range shifts are considered key to species persistence. However, some range-shifting species will alter community structure and ecosystem processes. By adapting existing invasion risk assessment frameworks, we can identify characteristics shared with high-impact introductions and thus predict potential impacts. There are fundamen- tal differences between introduced and range-shifting species, primarily shared evolutionary histories between range shifters and their new community. Nevertheless, impacts can occur via analogous mechanisms, such as wide dispersal, community disturbance and low biotic resistance. As ranges shift in response to climate change, we have an opportunity to develop plans to facilitate …

David Quentin Bowen: A Memorial, John T. Andrews, David R. Bridgland, Peter U. Clark, Thomas M. Cronin, Claude Hillaire-Marcel, Darrel Maddy, Gifford H. Miller, Daniel R. Muhs, Colin V. Murray-Wallace

United States Geological Survey: Staff Publications

The Quaternary community lost a giant and a leader on October 5, 2020, when David Quentin Bowen, known to many as “DQ” and founding editor of Quaternary Science Reviews, passed away in Cardiff. Born on February 14, 1938 in Llanelli, SouthWales, he received his PhD at University College London. David’s 50 years of contributions to our science cannot be adequately summarized in a brief memorial but past, present, and future generations of Quaternary scientists will long remember his landmark achievements in publishing, his scientific contributions, and his personal and professional class in all his endeavors.

Late Quaternary Sea-Level History Of Saipan, Commonwealth Of The Northern Mariana Islands, Usa: A Test Of Tectonic Uplift And Glacial Isostatic Adjustment Models, Daniel R. Muhs, Eugene S. Schweig, Kathleen R. Simmons

United States Geological Survey: Staff Publications

In 1979, S. Uyeda and H. Kanamori proposed a tectonic model with two end members of a subduction-boundary continuum: the “Chilean” type (shallow dip of the subducting plate, great thrust events, compression, and uplift of the overriding plate) and a “Mariana” type (steep dip of the subducting plate, no great thrust events, tension, and no uplift). This concept has been used to explain variable rates of Quaternary uplift around the Pacific Rim, yet no uplift rates have been determined for the Mariana Islands themselves, one of the end members in this model. We studied the late Quaternary Tanapag Limestone, which …