Geology Commons^™

Stratigraphic Framework, Discontinuity Surfaces, And Regional Significance Of Campanian Slope To Ramp Carbonates From Central Dalmatia, Croatia, M. Brlek, T. Korbar, B. Cvetko Tešović, B. Glumac, L. Fuček

Geosciences: Faculty Publications

The sedimentology, microfacies, and stratigraphic age (from planktonic and benthic foraminifera and strontium-isotope stratigraphy) of a 300-m-thick Upper Cretaceous carbonate succession from the Island of Čiovo (central Dalmatia, Croatia) were analyzed in order to determine the lithostratigraphic, depositional, and chronostratigraphic framework. The Cretaceous strata were deposited in the southern part of the long-lasting (Late Triassic to Paleogene) Adriatic-Dinaridic Carbonate Platform (ADCP), one of a few late Mesozoic, intra-Tethyan, peri-Adriatic (sub)tropical archipelagos. The succession is separated by a firmground formational boundary into two lithostratigraphic units: the underlying Middle to Upper Campanian Dol Formation consisting of slope pelagic limestone with intercalated turbidites …

Preservational And Morphological Variability Of Assemblages Of Agglutinated Eukaryotes In Cryogenian Cap Carbonates Of Northern Namibia, Lilly A. Dalton, Tanja Bosak, Francis A. Macdonald, Daniel J.G. Lahr, Sara B. Pruss

Geosciences: Faculty Publications

Laminated carbonates of the Rasthof Formation, deposited in the aftermath of the early Cryogenian low-latitude glaciation (Sturtian, 717-662 Ma), preserve abundant round tests of agglutinated microscopic eukaryotes. Previously, fossil tests were reported in two localities (Ongongo and Okaaru) from microbially laminated carbonates in the Rasthof Formation, which revealed a previous unexplored Cryogenian taphonomic window. In order to better understand the lateral variability in these microfossil assemblages, this work systematically examines fossil tests from two additional localities, South Ombepera and Ombepera, and compares their preservation in thinly and thickly laminated microbial laminites. Cap carbonates in South Ombepera and Ombepera contain abundant, …

Geodetic Constraints On San Francisco Bay Area Fault Slip Rates And Potential Seismogenic Asperities On The Partially Creeping Hayward Fault, Eileen L. Evans, John P. Loveless, Brendan J. Meade

Geosciences: Faculty Publications

The Hayward fault in the San Francisco Bay Area (SFBA) is sometimes considered unusual among continental faults for exhibiting significant aseismic creep during the interseismic phase of the seismic cycle while also generating sufficient elastic strain to produce major earthquakes. Imaging the spatial variation in interseismic fault creep on the Hayward fault is complicated because of the interseismic strain accumulation associated with nearby faults in the SFBA, where the relative motion between the Pacific plate and the Sierra block is partitioned across closely spaced subparallel faults. To estimate spatially variable creep on the Hayward fault, we interpret geodetic observations with …

Response Of A Carbonate Platform To The Cenomanian-Turonian Drowning And Oae 2: A Case Study From The Adriatic Platform (Dalmatia, Croatia), Tvrtko Korbar, B. Glumac, Blanka Cvetko Tesovic, Sarah B. Cadieux

Geosciences: Faculty Publications

Global perturbations during the Cenomanian–Turonian boundary (CTB) interval and the Oceanic Anoxic Event 2 (OAE 2) represent one of the most extensively studied past environmental changes. To explore the response of various carbonate-platform depositional systems to such major environmental perturbations, strata of the intra-Tethyan Adriatic carbonate platform (sensu stricto) from the island of Bracˇ (Adriatic Sea, Croatia) provide excellent exposures and a previously well-established Upper Cretaceous lithostratigraphic framework. Within this context, this study integrated lithostratigraphy, biostratigraphy, and chemostratigraphy to describe a drowned-platform succession underlain and overlain by peritidal carbonates. Carbon-isotope stratigraphy of this succession revealed a shift towards positive d13C …

Recovery Of Carbonate Sand Beaches On San Salvador Island, Bahamas From Damage By Hurricane Frances (2004), H. Allen Curran, Mia Schultz-Baer, Kathryn Durkin, Bosiljka Glumac

Geosciences: Faculty Publications

East Beach and Hanna Bay Beach, located on the northeast coast of San Salvador, were two of the island's beaches most heavily impacted by Hurricane Frances (category 3) on September 2, 2004. A maximum storm surge of 3.1 m was reported for East Beach, with erosion occurring up to 70 m inland from the wave-break line and resulting in scarps cut into dunes of up to 1.5 m height. In January 2005, 5 beach profile stations along 1 km of East Beach and 3 stations along Hanna Bay Beach were established to monitor long-term coastal recovery from hurricane damage. East …

Geology Of New Providence Island, Bahamas: A Field Trip Guide, John E. Mylroie, James L. Carew, H. Allen Curran, Fabienne Godefroid, Pascal Kindler, Neil E. Sealey

Geosciences: Faculty Publications

See other Smith authored Field Trip Guides of Gerace Research Centre.

Possible Early Foraminiferans In Post-Sturtian (716-635 Ma) Cap Carbonates, Tanja Bosak, Daniel J.G. Lahr, Sara B. Pruss, Francis A. Macdonald, Andrew J. Gooday, Lilly Dalton, Emily D. Matys

Geosciences: Faculty Publications

Foraminifera are an ecologically important group of modern heterotrophic amoeboid eukaryotes whose naked and testate ancestors are thought to have evolved ~1 Ga ago. However, the single-chambered agglutinated tests of these protists appear in the fossil record only after ca. 580 Ma, coinciding with the appearance of macro scopic and mineralized animals. Here we report the discovery of small, slender tubular microfossils in the Sturtian (ca. 716-635 Ma) cap carbonate of the Rasthof Formation in Namibia. The tubes are 200-1300 μm long and 20-70μm wide, and preserve apertures and variably wide lumens, folds, constrictions, and ridges. Their sometimes fl exible …

Unusual Holocene Serpulid-Tufu Bioherms, Enriquillo Valley, Dominican Republic: Morphologies And Paleoenvironmental Implications, Kelsey Winsor, H. Allen Curran, Lisa Greer, Bosiljka Glumac

Geosciences: Faculty Publications

During the early Holocene, rising waters of the Caribbean Sea flooded the Enriquillo Valley of southwestern Dominican Republic. A fringing coral reef developed and flourished along the margins of the Enriquillo Seaway for several millennia, until the seaway became restricted due to a combination of slowed sea-level rise, tectonic uplift, and increased sedimentation. Following changes in salinity and death of the coral reef by about 5 ka, meter-scale bioherms composed of the tubes of opportunistic, aggregating serpulid worms and associated with carbonate tufa that precipitated from the ancient lake or declining seaway waters formed along the steep walls of the …

Distribution Of Oolitic Sediment Along A Beach-To-Offshore Transect, Pigeon Cay, Cat Island, Bahamas: New Insights Into Modern Ooid Formation, Bosiljka Glumac, H. Allen Curran, Madeline M. Weigner, Sarah A. Motti, Sara B. Pruss

Geosciences: Faculty Publications

Ooids are a common component of ancient carbonate rocks, but their origin and distribution in Holocene deposits and modem carbonate sands are not fully understood. Even though ooids are well documented from several localities in the Bahamian Archipelago, their occurrence on Cat Island has not been previously studied in detail. In this study we examined the composition and texture of beach sand and six sediment samples collected from the sea floor at approximately 50-meter intervals along an estimated 300 m transect at Pigeon Cay, Cat Island.

Stress Modulation On The San Andreas Fault By Interseismic Fault System Interactions, John P. Loveless, Brendan J. Meade

Geosciences: Faculty Publications

During the interseismic phase of the earthquake cycle, between large earthquakes, stress on faults evolves in response to elastic strain accumulation driven by tectonic plate motions. Because earthquake cycle processes induce non-local stress changes, the interseismic stress accumulation rate on one fault is influenced by the behavior of all nearby faults. Using a geodetically constrained block model, we show that the total interseismic elastic strain field generated by fault interactions within Southern California may increase stressing rates on the Mojave and San Bernardino sections of the San Andreas fault within the Big Bend region by as much as 38% relative …

Spatial Correlation Of Interseismic Coupling And Coseismic Rupture Extent Of The 2011 Mw=9.0 Tohoku-Oki Earthquake, John P. Loveless, Brendan J. Meade

Geosciences: Faculty Publications

Imaging the extent to which the rupture areas of great earthquakes coincide with regions of pre-seismic interplate coupling is central to understanding patterns of strain accumulation and release through the earthquake cycle. Both geodetic and seismic estimates of the coseismic rupture extent for the March 11, 2011 MW = 8.9–9.0 earthquake Tohoku-oki earthquake may be spatially correlated (0.26 ± 0.05 to 0.82 ± 0.05) with a region estimated to be partially to fully coupled in the interseismic period preceding the earthquake, though there is substantial variation in the estimated distribution and magnitude of coseismic slip. The ∼400 km-long region estimated …

Polygonal Sandcracks: Unique Sedimentary Desiccation Structures In Bahamian Ooid Grainstone, Bosiljka Glumac, H. Allen Curran, Sarah A. Motti, Madeline M. Weigner, Sarah Pruss

Geosciences: Faculty Publications

Sandcracks, which are ubiquitous in Holocene eolian and beach backshore carbonate grainstone on Alligator Point, Cat Island, Bahamas, resemble polygonal mudcracks, but formed in ooid sand without muddy matrix. In experiments on Cat Island beach sand, sediment surfaces cracked polygonally in the absence of mud or biofi lms while drying at room temperature due to contraction generated by capillary effects related to surface tension attraction of interstitial water. Gravitational collapse of irregular open pores and repacking of sand grains due to loss of cohesion between particles caused by evaporation of water enhance the cracking process and appearance of polygons by …

Sphenothallus-Like Fossils From The Martinsburg Formation (Upper Ordovician), Tennessee, Usa, Maya Li Wei-Haas, Bosiljka Glumac, H. Allen Curran

Geosciences: Faculty Publications

Tubular fossils, up to 2 mm in diameter and 60 mm in length, occur rarely in the upper Martinsburg Formation (Upper Ordovician), northeastern Tennessee Appalachians, U.S.A. The fossils are unbranched, straight or slightly bent, occasionally twisted and wrinkled, and not significantly tapered. Orientation of the fossils within shallow-marine tempestites suggests that they represent remains of organisms that were broken, transported, and deposited by storm waves and currents. The fossils are morphologically similar to many of the previously identified species belonging to the genus Sphenothallus, a relatively rare tube-dwelling Paleozoic marine invertebrate. Owing to the limited evidence for distal widening of …

Partitioning Of Localized And Diffuse Deformation In The Tibetan Plateau From Joint Inversions Of Geologic And Geodetic Observations, John P. Loveless, Brendan J. Meade

Geosciences: Faculty Publications

The spatial complexity of continental deformation in the greater Tibetan Plateau region can be defined as the extent to which relative motion of the Indian and Asian plates is partitioned between localized slip on major faults and distributed deformation. Potency rates provide a quantitative metric for determining the magnitudes of diffuse and on-fault crustal deformation, which are proportional to strain rates within crustal micro-plates and fault slip rates, respectively. We simultaneously estimate micro-plate rotation rates, interseismic elastic strain accumulation, fault slip rates on major structures, and strain rates within 24 tectonic micro-plates inferred from active fault maps in the greater …

Evolution Of The Veternica Cave (Medvednica Mountain, Croatia) Drainage System: Insights From The Distribution And Dating Of Cave Deposits, Damir Lacković, Bosiljka Glumac, Yemane Asmerom, Andrej Stroj

Geosciences: Faculty Publications

Detailed field examination, U-Th age dating, and stable isotope analysis of Veternica flowstone and shelfstone deposits have been employed in order to unravel details about the geological history of Veternica Cave (Medvednica Mountain, Croatia). The study was carried out in the hydrologically inactive part of the main cave channel, which is developed mainly along the unconformity between Triassic dolostone and Miocene limestone. For 180 m from the cave entrance, (located at 320 metres above sea level (asl)), the morphology of the main channel reflects exclusively phreatic conditions in the cave until the end of its hydrological activity. From 180 to …

Testing Mechanisms Of Subduction Zone Segmentation And Seismogenesis With Slip Distributions From Recent Andean Earthquakes, John P. Loveless, M. E. Pritchard, K. Kukowski

Geosciences: Faculty Publications

A long-standing goal of subduction zone earthquake studies is to determine whether or not there are physical processes that control seismogenesis and the along-strike segmentation of the megathrust. Studies of individual earthquakes and global compilations of earthquakes find favorable comparison between coseismic interplate slip distributions and several different long-lived forearc characteristics, such as bathymetry, coastline morphology, crustal structure, and interplate frictional properties, but no single explanation seems to govern the location and slip distribution of all earthquakes. One possible reason for the lack of a unifying explanation is that the inferred earthquake parameters, most importantly the slip distribution, calculated in …

Climatic Cycles Recorded In The Middle Eocene Hemipelagites From A Dinaric Foreland Basin Of Istria (Croatia), Borna Lužar-Oberiter, Peter A. Hochuli, Ljubomir Babić, Bosiljka Glumac, Darko Tibljas

Geosciences: Faculty Publications

Middle Eocene hemipelagic marls from the Pazin-Trieste Basin, a foreland basin of the Croatian Dinarides, display repetitive alternations of two types of marls with different resistance to weathering. This study focuses on the chemical composition, stable isotopes, and palynomorph content of these marls in order to better understand the nature of their cyclic deposition and to identify possible paleoenvironmental drivers responsible for their formation. The less resistant marls (LRM) have consistently lower carbonate content, lower δ18O and δ13C values, and more abundant dinoflagellate cysts than the more resistant marls (MRM). We interpret these differences between the two marl types to …

Normal And Reverse Faulting Driven By The Subduction Zone Earthquake Cycle In The Northern Chilean Forearc, John P. Loveless, Richard W. Allmendinger, Matthew E. Pritchard, Gabriel González

Geosciences: Faculty Publications

Despite its location in a convergent tectonic setting, the Coastal Cordillera of northern Chile between 21°S and 25°S is dominated by structures demonstrating extension in the direction of plate convergence. In some locations, however, normal faults have been reactivated as reverse faults, complicating the interpretation of long-term strain. In order to place these new observations in a tectonic context, we model stress changes induced on these faults by the subduction earthquake cycle. Our simulations predict that interseismic locking on the plate boundary encourages normal slip on fore-arc faults, which may result from elastic rebound due to interplate earthquakes or from …

Geodetic Imaging Of Plate Motions, Slip Rates, And Partitioning Of Deformation In Japan, John P. Loveless, Brendan J. Meade

Geosciences: Faculty Publications

Interseismic deformation in Japan results from the combined effects of tectonic processes including rotation of crustal blocks and the earthquake cycle process of elastic strain accumulation about upper plate faults and subduction zone interfaces. We use spherical linear block theory constrained by geodetic observations from densely spaced Global Positioning System (GPS) stations to estimate plate motions, fault slip rates, and spatially variable interplate coupling on the Japan-Kuril, Sagami, and Nankai subduction zones. The reference model developed in this paper consists of 20 blocks, produces a mean residual velocity magnitude of 1.84 mm/yr at 950 stations, and accounts for 96% of …

Carbonates In Skeleton-Poor Seas: New Insights From Cambrian And Ordovician Strata Of Laurentia, Sara B. Pruss, Seth Finnegan, Woodward W. Fischer, Andrew H. Knoll

Geosciences: Faculty Publications

Calcareous skeletons evolved as part of the greater EdiacaranCambrian diversification of marine animals. Skeletons did not become permanent, globally important sources of carbonate sediment, however, until the Ordovician radiation. Representative carbonate facies in a Series 3 (510501 Ma) Cambrian to Tremadocian succession from western Newfoundland, Canada, and Ordovician successions from the Ibex area, Utah, USA, show that, on average, Cambrian and Tremadocian carbonates contain much less skeletal material than do post-Tremadocian sediments. Petrographic point counts of skeletal abundance within facies and proportional facies abundance in measured sections suggest that later Cambrian successions contain on average volume, whereas the skeletal content …

Geology Of Central Eleuthera, Bahamas: A Field Trip Guide, Pascal Kindler, John E. Mylroie, H. Allen Curran, James L. Carew, Douglas W. Gamble, Thomas A. Rothfus

Geosciences: Faculty Publications

See other Smith authored Field Trip Guides of Gerace Research Centre.

Enigmatic Structures On Upper Pleistocene Laminar Caliche Surfaces Of The Bahamas: Animal, Vegetable, Or Mineral?, H. Allen Curran

Geosciences: Faculty Publications

Trace fossils are a common and important component of most Quaternary carbonate rock units of the Bahamas and other, similar tropical carbonate regions. In the Bahamas, the Pleistocene-Holocene boundary is typically marked by a calichified paleosol horizon that formed on the exposed limestone surfaces of the islands during the time of lowered sea level of the Last Glacial. On the north coast of San Salvador Island, an extensive horizontal surface of laminar caliche is exposed at Singer Bar Point and to the west. This surface formed on carbonate eolianite of Late Pleistocene (Eemian) age and is overlain by Holocene eolianite. …

Bioturbation, Habitat Partitioning, And Tiering In Tropical Intertidal Callianassid Mounds: An Example From The Bahamas, H. Allen Curran

Geosciences: Faculty Publications

Abstract from 2010 Workshop on Crustacean Bioturbation — Fossil and Recent held in Lepe, Spain.

Editors: Jordi M. deGibert, Fernando Muñiz, Eduardo Mayoral, Zain Belaústegui

Burrow Morphology Of The Bahamian Land Crab Gecarcinus Lateralis, Koji Seike, H. Allen Curran

Geosciences: Faculty Publications

Abstract from 2010 Workshop on Crustacean Bioturbation — Fossil and Recent held in Lepe, Spain.

Editors: Jordi M. deGibert, Fernando Muñiz, Eduardo Mayoral, Zain Belaústegui

Block Modeling With Multiple Fault Network Geometries And A Linear Elastic Coupling Estimator In Spherical Coordinates, Brendan J. Meade, John P. Loveless

Geosciences: Faculty Publications

Geodetic observations of interseismic deformation provide constraints on the partitioning of fault slip across plate boundary zones, the spatial distribution of both elastic and inelastic strain accumulation, and the nature of the fault system evolution. Here we describe linear block theory, which decomposes surface velocity fields into four components: (1) plate rotations, (2) elastic deformation from faults with kinematically consistent slip rates, (3) elastic deformation from faults with spatially variable coupling, and (4) homogeneous intrablock strain. Elastic deformation rates are computed for each fault segment in a homogeneous elastic half-space using multiple optimal planar Cartesian coordinate systems to minimize areal …

From Decades To Epochs: Spanning The Gap Between Geodesy And Structural Geology Of Active Mountain Belts, Richard W. Allmendinger, John P. Loveless, Matthew E. Pritchard, Brendan Meade

Geosciences: Faculty Publications

Geodetic data from the Global Navigation Satellite System (GNSS), and from satellite interferometric radar (InSAR) are revolutionizing how we look at instantaneous tectonic deformation, but the significance for long-term finite strain in orogenic belts is less clear. We review two different ways of analyzing geodetic data: velocity gradient fields from which one can extract strain, dilatation, and rotation rate, and elastic block modeling, which assumes that deformation is not continuous but occurs primarily on networks of interconnected faults separating quasi-rigid blocks. These methods are complementary: velocity gradients are purely kinematic and yield information about regional deformation; the calculation does not …

Predicting The Geodetic Signature Of Mw 8 Slow Slip Events, Brendan J. Meade, John P. Loveless

Geosciences: Faculty Publications

Elastic dislocation models of geodetic measurements

above subduction zones have led to the identification of

MW 6.0– 7.2 slow slip events (SSEs) that release elastic

strain over periods of days to months, but great (MW 8)

SSEs have remained unidentified. We extrapolate

observations of SSE duration and slip magnitude to show

that slip velocity decreases with event magnitude and

predict that the slip velocity of MW 8 SSEs is 50 mm/yr.

The slip velocity for great SSEs may never exceed the

plate convergence rate and thus never produce a reversal

in trench perpendicular motion. Instead, geodetically

constrained estimates of apparent …

Surface Cracks Record Long-Term Seismic Segmentation Of The Andean Margin, John P. Loveless, Richard W. Allmendinger, Matthew E. Pritchard, Jordan L. Garroway, Gabriel González

Geosciences: Faculty Publications

Understanding the long-term patterns of great earthquake rupture along a subduction zone provides a framework for assessing modern seismic hazard. However, evidence that can be used to infer the size and location of past earthquakes is typically erased by erosion after a few thousand years. Meter-scale cracks that cut the surface of coastal areas in northern Chile and southern Peru preserve a record of earthquakes spanning several hundred thousand years owing to the hyperarid climate of the region. These cracks have been observed to form during and/or shortly after strong subduction earthquakes, are preserved for long time periods throughout the …

Magma In A Beaker: Analog Experiments With Water And Various Salts Or Sugar For Teaching Igneous Petrology, John B. Brady

Geosciences: Faculty Publications

Solutions of water and a salt or sugar make excellent experimental analog magmas for teaching concepts of igneous petrology because of the comparatively low temperatures involved, the simplicity of the apparatus needed, and the responsiveness of familiar chemical systems. Boiling of these aqueous solutions on a hot plate can be used to increase the concentration of a dissolved salt or sugar to levels that may be predicted by steam-saturation curves. Sufficiently concentrated solutions will crystallize, partially or completely, upon cooling to room temperature. Binary temperature–composition phase diagrams for H₂O and KCl, NaCl, MgCl₂, CaCl₂, …

Motion On Upper-Plate Faults During Subduction Zone Earthquakes: Case Of The Atacama Fault System, Northern Chile, John P. Loveless, Matthew E. Pritchard

Geosciences: Faculty Publications

Motion on the Atacama Fault System (AFS) in northern Chile is driven by Andean subduction zone processes. We use two approaches, observational and theoretical, to evaluate how the AFS and other forearc faults responded to coseismic stress induced by one well-studied megathrust earthquake, the 1995 Mw = 8.1 Antofagasta event. We use synthetic aperture radar interferometry (InSAR) to search for small-scale coseismic and postseismic deformation on individual faults. The InSAR data are ambiguous: some images show offset consistent with coseismic faulting on the Paposo segment of the AFS and others lack such signal. The fact that we do not …