DOCSLIB.ORG

I LATE MESOZOIC and CENOZOIC KINEMATIC RECONSTRUCTION

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
I LATE MESOZOIC and CENOZOIC KINEMATIC RECONSTRUCTION LATE MESOZOIC AND CENOZOIC KINEMATIC RECONSTRUCTION: ASSESSMENT OF LATE CRETACEOUS MAGMATISM AND SOURCE-TO- SINK CONFIGURATION IN THE NORTHWESTERN GULF OF MEXICO A Thesis Presented to the Faculty of the Department of Earth and Atmospheric Sciences University of Houston ________________________________________ In Partial Fulfillment of the Requirements for the Degree Master of Science _________________________________________ By Jordan Nicole Dickinson August 2017 i LATE MESOZOIC AND CENOZOIC KINEMATIC RECONSTRUCTION: ASSESSMENT OF LATE CRETACEOUS MAGMATISM AND SOURCE-TO- SINK CONFIGURATION IN THE NORTHWESTERN GULF OF MEXICO _______________________________________ Jordan Dickinson APPROVED: _______________________________________ Dr. Michael Murphy, Chairman _______________________________________ Dr. Joel Saylor _______________________________________ Dr. Ana Krueger _______________________________________ Dr. Pete Emmet _______________________________________ Dean, College of Natural Sciences and Mathematics ii ACKNOWLEDGMENTS First and foremost, I would like to thank my advisor Dr. Michael Murphy. Throughout my Master’s Program with UH, Dr. Murphy has instilled an incredible amount of wisdom and guidance into my education. I greatly appreciate his knowledge and energy spent in teaching and advising me throughout my Master’s Program. Dr. Ana Krueger was invaluable with her assistance and guidance with teaching me the necessary softwares and demonstrating the utmost patience, and I appreciate her time and efforts. I am very thankful for my thesis committee which consisted of Dr. Joel Saylor, Dr. Pete Emmet, and Dr. Ana Krueger as well as Dr. Murphy. Throughout my research I conferred with these faculty, previous students, and attended conferences to gain information from all the people who generously provided me with information which made the process rewarding. Last but not least, I am also thankful to my parents and to Wills for their unconditional love and support. iii LATE MESOZOIC AND CENOZOIC KINEMATIC RECONSTRUCTION: ASSESSMENT OF LATE CRETACEOUS MAGMATISM AND SOURCE-TO- SINK CONFIGURATION IN THE NORTHWESTERN GULF OF MEXICO An Abstract of a Thesis Presented to the Faculty of the Department of Earth and Atmospheric Sciences University of Houston ________________________________________ In Partial Fulfillment of the Requirements for the Degree Master of Science _________________________________________ By Jordan Nicole Dickinson August 2017 iv ABSTRACT It has been demonstrated that emplacement of 92-108 Ma post-breakup alkalic magmatism and attendant structural culminations in Louisiana and Arkansas facilitated mid-Cretaceous surface uplift, development of unconformities in updip areas, and incision of fringinng reefs along the northern Gulf of Mexico thereby promoting the development of depositional fairways that permitted transport of Late Cretaceous course siliclastic sediments into the deep water gulf. To the west, the Balcones Igneous Province, exposed for 397 km from Austin to Carizo Springs, Texas, was emplaced between 83.5 and 72.4 Ma. Should this hypothesis for the mechanism driving incision and siliciclastic transport past the fringing carbonate reef due to the Sabine and Monroe uplifts prove to be valid, it is possible that surface uplift above the Balcones igneous province and Llano uplift could have produced the same effect. Additionally, it has long been acknowledged that sedimentation, such as that from an influx of Paleocene sediments, is a driving factor of deformational extension in the Gulf of Mexico, though there have been no previous attempts to quantify it. This is a process most easily acheived through structural restoration. For this thesis, I fully interpreted fautls, salt bodies, and 16 horizons on two GulfSPAN regional 2D seismic reflection profiles guided by well ties from 48 available wells, seismic attributes, and previous interpretations in proximal areas. I also conducted a full line-length kinematic reconstruction on GulfSPAN line 2450 from the Holocene to the Middle Jurassic using 2D Move restoration software, and calculated extension based on the results. GulfSPAN line 2450 was restored in 12 time steps back to the Middle Jurassic, revealing the paleobathymetric surface at each step and providing insight into paleodepositional settings. Measurements of extension from the Pliocene to the Middle Jurassic revealed rates of extension that show generally low rates in the Cretaceous and Paleocene that increase and peak in the Oligocene with modest rates through the Middle Miocene before tapering off. Finally, 2D seismic interpretation delineated 5 sets of slope canyons fed from Paleocene age delta systems. I interpret this system to have been driven by surface uplift on land 10 to 30 Mya later in the Balcones Igneous province than in the Sabine and Monroe uplifts to the east. v CONTENTS CHAPTER 1: INTRODUCTION ...................................................................................... 1 1.1 Motivation and Objectives ....................................................................................... 1 1.2 Study Area ................................................................................................................ 5 1.3 Significance .............................................................................................................. 6 CHAPTER 2: REGIONAL GEOLOGY ........................................................................... 9 CHAPTER 3: DATA & METHODOLOGY ................................................................... 12 3.1 Introduction ............................................................................................................ 12 3.2 2D Seismic Interpretation....................................................................................... 12 3.3 Gravity and Magnetic Data .................................................................................... 16 3.4 Kinematic Restoration ............................................................................................ 17 CHAPTER 4: INTERPRETATIONS .............................................................................. 21 4.1 Strikeline 5000 ....................................................................................................... 21 4.2 Dip Line 2450......................................................................................................... 25 4.3 Gravity and Magnetic Data .................................................................................... 28 CHAPTER 5: STRUCTURAL RESTORATION ........................................................... 34 5.1 Stage M (Middle Jurassic) ..................................................................................... 36 5.2 Stage L (Early Cretaceous) .................................................................................... 36 5.3 Stage K (Late Cretaceous)...................................................................................... 37 5.4 Stage J (Early Paleocene) ....................................................................................... 37 5.5 Stage I (Late Paleocene) ......................................................................................... 38 5.6 Stage H (Eocene) .................................................................................................... 40 5.7 Stage G (Oligocene) ............................................................................................... 41 5.8 Stage F (Early Miocene) ........................................................................................ 41 5.9 Stage E (Middle Miocene) ..................................................................................... 43 5.10 Stage D (Late Miocene) ....................................................................................... 43 5.11 Stage C (Pliocene) ................................................................................................ 44 5.12 Stage B (Pleistocene) ........................................................................................... 44 vi 5.13 Stage A (Present) .................................................................................................. 44 CHAPTER 6: DISCUSSION AND CONCLUSIONS .................................................... 45 6.1 Paleocene Incision in the Northwestern Gulf of Mexico ....................................... 45 6.2 Extension in the Gulf of Mexico ............................................................................ 47 6.3 Potential Mechanisms for Late Cretaceous Uplift ................................................. 50 6.4 Conclusions ............................................................................................................ 50 REFERENCES ................................................................................................................ 54 APPENDIX………………………………………………………………………………58 vii CHAPTER 1: INTRODUCTION 1.1 Motivation and Objectives Examples of gravity induced deformation along a salt detachment producing significant extensional and shortening regimes have been observed in several passive margin settings (Withjack et al., 1995; Hudec and Jackson, 2002). The northern Gulf of Mexico is one of the best places to study this phenomenon because of the varying nature of extensional deformation across the basin. The most basic type of structural style found in the Gulf of Mexico is a linked system of updip extension, downdip shortening, and an intermediate transitional zone (Figure 1). Along strike, magnitudes
Load more

Recommended publications
  • Age Progressive Volcanism in the New England Seamounts and the Opening of the Central Atlantic Ocean
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 89, NO. B12, PAGES 9980-9990, NOVEMBER 10, 1984 AGEPROGRESSIVE VOLCANISM IN THENEW ENGLAND SEAMOUNTS AND THE OPENING OF THE CENTRAL ATLANTIC OCEAN R. A. Duncan College of Oceanography, Oregon State University, Corvallis Abstract. Radiometric ages (K-Ar and •øAr- transient featur e•s that allow calculations of 39Ar methods) have been determined on dredged relative motions only. volcanic rocks from seven of the New England The possibility that plate motions may be Seamounts, a prominent northwest-southeast trend- recorded by lines of islands and seamounts in the ing volcanic lineament in the northwestern ocean basins is attractive in this regard. If, Atlantic Ocean. The •øAr-39Ar total fusion and as the Carey-Wilson-Morgan model [Carey, 1958; incren•ental heating ages show an increase in Wilson, 1963; Morgan, 19•1] proposes, sublitho- seamount construction age from southeast to spheric, thermal anomalies called hot spots are northwest that is consistent with northwestward active and fixed with respect to one another in motion of the North American plate over a New the earth's upper mantle, they would then consti- England hot spot between 103 and 82 Ma. A linear tute a reference frame for directly and precisely volcano migration rate of 4.7 cm/yr fits the measuring plate motions. Ancient longitudes as seamount age distribution. These ages fall well as latitudes would be determined from vol- Within a longer age progression from the Corner cano construction ages along the tracks left by Seamounts (70 to 75 Ma), at the eastern end of hot spots and, providing relative plate motions the New England Seamounts, to the youngest phase are also known, quantitative estimates of conver- of volcanism in the White Mountain Igneous gent plate motions can be calculated [Engebretson Province, New England (100 to 124 Ma).
    [Show full text]
  • A Joint Local and Teleseismic Tomography Study Of
    PUBLICATIONS Journal of Geophysical Research: Solid Earth RESEARCH ARTICLE A joint local and teleseismic tomography study 10.1002/2015JB012761 of the Mississippi Embayment and New Madrid Key Points: Seismic Zone • We present detailed 3-D images of Vp 1 1 1 and Vs for the upper mantle below the Cecilia A. Nyamwandha , Christine A. Powell , and Charles A. Langston ME and NMSZ • A prominent low-velocity anomaly 1Center for Earthquake Research and Information, University of Memphis, Memphis, Tennessee, USA with similar Vp and Vs anomalies is imaged in the upper mantle • Regions of similar high Vp and Vs anomalies present above and to the Abstract Detailed, upper mantle P and S wave velocity (Vp and Vs) models are developed for the northern sides of the low-velocity anomaly Mississippi Embayment (ME), a major physiographic feature in the Central United States (U.S.) and the location of the active New Madrid Seismic Zone (NMSZ). This study incorporates local earthquake and teleseismic data from the New Madrid Seismic Network, the Earthscope Transportable Array, and the Correspondence to: FlexArray Northern Embayment Lithospheric Experiment stations. The Vp and Vs solutions contain anomalies C. A. Nyamwandha, with similar magnitudes and spatial distributions. High velocities are present in the lower crust beneath the [email protected] NMSZ. A pronounced low-velocity anomaly of ~ À3%–À5% is imaged at depths of 100–250 km. High-velocity anomalies of ~ +3%–+4% are observed at depths of 80–160 km and are located along the sides and top Citation: of the low-velocity anomaly. The low-velocity anomaly is attributed to the presence of hot fluids upwelling Nyamwandha, C.
    [Show full text]
  • PDF Linkchapter
    Index [Italic page numbers indicate major references] Abaco Knoll, 359 116, 304, 310, 323 Bahama Platform, 11, 329, 331, 332, Abathomphalus mayaroensis, 101 Aquia Formation, 97, 98, 124 341, 358, 360 Abbott pluton, 220 aquifers, 463, 464, 466, 468, 471, Bahama volcanic crust, 356 Abenaki Formation, 72, 74, 257, 476, 584 Bahamas basin, 3, 5, 35, 37, 39, 40, 259, 261, 369, 372, 458 Aquitaine, France, 213, 374 50 ablation, 149 Arcadia Formation, 505 Bahamas Fracture Zone, 24, 39, 40, Abyssal Plain, 445 Archaean age, 57 50, 110, 202, 349, 358, 368 Adirondack Mountains, 568 Arctic-North Atlantic rift system, 49, Bahamas Slope, 12 Afar region, Djibouti, 220, 357 50 Bahamas-Cuban Fault system, 50 Africa, 146, 229, 269, 295, 299 Ardsley, New York, 568, 577 Baja California, Mexico, 146 African continental crust, 45, 331, Argana basin, Morocco, 206 Bajocian assemblages, 20, 32 347 Argo Fan, Scotian margin, 279 Balair fault zone, 560 African Craton, 368 Argo Salt Formation, 72, 197, 200, Baltimore Canyon trough, 3, 37, 38, African margin, 45, 374 278, 366, 369, 373 40, 50, 67, 72 , 81, 101, 102, African plate, 19, 39, 44, 49 arkoses, 3 138, 139, 222, 254, 269, 360, Afro-European plate, 197 artesian aquifers, 463 366, 369, 396, 419,437 Agamenticus pluton, 220 Ashley Formation, 126 basement rocks, 74 age, 19, 208, 223 Astrerosoma, 96 carbonate deposits, 79 Agulhas Bank, 146 Atkinson Formation, 116, 117 crustal structure, 4, 5, 46 Aiken Formation, 125 Atlantic basin, 6, 9, 264 faults in, 32 Aikin, South Carolina, 515 marine physiography, 9 geologic
    [Show full text]
  • Hotspots and Mantle Plumes Pdf
    Hotspots and mantle plumes pdf Continue The mantle feathers area is hot, upwelling the mantle. A hot spot develops above the train. Magma, generated by a hot spot, rises through rigid slabs of the lithosphere and produces active volcanoes on the Earth's surface. As ocean volcanoes move away from the hotspot, they cool and subside, producing old islands, atolls and seamounts. As continental volcanoes move away from the hotspot, they cool, subside and die out. Hot spots are places inside the mantle where stones melt to generate magma. The presence of a hot spot stems from abnormal volcanism (i.e. not on the plate boundary) such as Hawaiian volcanoes within the Pacific Plate. The Hawaiian hotspot has been active for at least 70 million years, producing a volcanic chain that stretches for 3,750 miles (6,000 km) across the Pacific Northwest. Hot spots also develop under continents. Yellowstone hot spot has been active for at least 15 million years, producing a chain of caldera and volcanic features along the plains of the Snake River, which stretches 400 miles (650 km) west from northwest Wyoming to the Idaho-Oregon border. Keep in mind, however, that these are just theories. No one knows the answer. The honest answer is that many people are working on it but have not yet come up with an answer. Graphics After Morgan, J., 1971, Convection feathers in the lower mantle: Nature, art 230, p. 42-43. Volcanic regions, which are thought to feed on the underlying mantle, are abnormally hot compared to the surrounding mantle Diagram, showing a cross-section across the Earth's lithosphere (yellow) with magma rising from the mantle (red).
    [Show full text]
  • Sleep, N.H., Hotspots and Mantle Plumes: Some Phenomenology, J
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 95, NO. B5, PAGES 6715-6736, MAY 10, 1990 Hotspotsand Mantle Plumes'Some Phenomenology NORMAN H. SLEEP Departmentsof Geologyand Geophysics,Stanford University, Stanford, California The availabledata, mainly topography, geoid, and heat flow, describinghotspots worldwide are examined to constrainthe mechanismsfor swelluplift and to obtainfluxes and excess temperatures of mantleplumes. Swelluplift is causedmainly by excesstemperatures that move with the lithosphereplate and to a lesser extenthot asthenospherenear the hotspot.The volume,heat, and buoyancy fluxes of hotspotsare computed fromthe cross-sectionalareas of swells,the shapes of nosesof swells,and, for on ridgehotspots, the amount of ascendingmaterial needed to supplythe lengthof ridgeaxis whichhas abnormallyhigh elevationand thickcrust. The buoyancy fluxes range over a factorof 20 withHawaii, 8.7 Mg s -1, thelargest. The buoy- ancyflux for Iceland is 1.4Mg s -1 whichis similarto theflux of CapeVerde. The excess temperature of both on-ridgeand off-ridgehotspots is aroundthe 200øCvalue inferred from petrologybut is not tightly constrainedby geophysicalconsiderations. This observation,the similarityof the fluxesof on-ridgeand off- ridgeplumes, and the tendency for hotspotsto crossthe ridge indicate that similar plumes are likely to cause both typesof hotspots.The buoyancyfluxes of 37 hotspotsare estimated;the globalbuoyancy flux is 50 Mgs -1, whichis equivalentto a globallyaveraged surface heat flow of 4 mWm-2 fromcore sources and wouldcool the core at a rateof 50ø C b.y. -1. Basedon a thermalmodel and the assumption that the likeli- hoodof subductionis independentof age,most of the heatfrom hotspotsis implacedin the lower litho- sphereand later subducted. I.NTRODUCWION ridge plumesusing Iceland as an example. The geometryof flow implied by the assumed existence of a low viscosity Linearseamount chains, such as the Hawaiian Islands, are asthenosphericchannelis illustrated bythis exercise.
    [Show full text]
  • Hotspot Swells Revisited
    Hotspot Swells Revisited Scott D. Kinga, Claudia Adama aDepartment of Geosciences, Virginia Tech, Blacksburg, VA Abstract The first attempts to quantify the width and height of hotspot swells were made more than 30 years ago. Since that time, global bathymetry, ocean-floor age, and sediment thickness datasets have improved considerably. Swell heights and widths have been used to estimate the heat flow from the core-mantle boundary, constrain numerical models of plumes, and as an indicator of the origin of hotspots. In this paper, we repeat the analysis of swell geometry and buoyancy flux for 54 hotspots, including the 37 considered by Sleep (1990) and the 49 considered by Courtillot et al. (2003), using the latest and most accurate data. We are able to calculate swell geometry for a number of hotspots that Sleep was only able to estimate by comparison with other swells. We find that in spite of the increased resolution in global bathymetry models there is significant uncertainty in our calculation of buoyancy fluxes due to differences in our measurement of the swells’ width and height, the integration method (volume integration or cross-sectional area), and the variations of the plate velocities between HS2-Nuvel1a (Gripp and Gordon, 1990) and HS3-Nuvel1a (Gripp and Gordon, 2002). We also note that the buoyancy flux for Pacific hotspots is in general larger than for Eurasian, North American, African and Antarctic hotspots. Considering that buoyancy flux is linearly related to plate velocity, we speculate that either the calculation of buoyancy flux using plate velocity over-estimates the actual vertical flow of material from the deep mantle or that convection in the Pacific hemisphere is more vigorous than the Atlantic hemisphere.
    [Show full text]
  • Multiresolution Tectonic Features Over the Earth Inferred from a Wavelet Transformed Geoid
    Vis Geosci (2003) 8: 26–44 DOI 10.1007/s10069-003-0008-8 ORIGINAL PAPER Ludeˇ k Vecsey Æ Catherine A. Hier Majumder David A. Yuen Multiresolution tectonic features over the Earth inferred from a wavelet transformed geoid Received: 25 September 2002 / Revised: 18 November 2002 / Accepted: 18 November 2002 / Published online: 1 April 2003 Ó Springer-Verlag 2003 Abstract Geoid signals give information about the un- structures that can only be picked up visually with much derlying density structure and can be used to locate the higher resolution spherical harmonic gravity data. We source depthof themass anomalies. Wavelet analysis have also looked at the wavelength at which the maxi- allows a multiresolution analysis of the signal and per- mum signal occurs over a range of scales. This method, mits one to zoom into a specific area bounded by a known as E-max and k-max, is especially effective for particular lengthscale. Theability of wavelets to resolve detecting plate tectonic boundaries and ancient suture the geoid signal into individual wavelength components zones along withareas of strong non-isostatic gravita- without losing the spatial information makes this tional potential due to high differential stress. These method superior to the more common spherical har- areas are likely to be at high risk of earthquakes. These monic method. The wavelet analysis allows one to zoom methods will be especially useful to future studies of the into a specific area and look at the regional geology. We geoid potentials of other planets, such as Mars and have used a wavelet transform of the geoid to study the Venus, since they will allow careful studies of the regional geology of Japan and the Philippine Plate, regional geology variations withgeoid data of the SouthAmerica, Europe, NorthAmerica, East Africa resolution available from satellites.
    [Show full text]
  • Global Na8-Fe8 Systematics of Morbs: Implications for Mantle Heterogeneity, Temperature, and Plumes D
    Global Na8-Fe8 Systematics of MORBs: Implications for Mantle Heterogeneity, Temperature, and Plumes D. Presnall (1,2,3), G. Gudfinnsson (2,3) (1) Department of Geosciences, University of Texas at Dallas, Richardson, TX, USA, (2) Geophysical Laboratory, Washington, D. C., USA, (3) Bayerisches Geoinstitut, Bayreuth, Germany ([email protected] / 972-883-2405 / 972-883-2444) In a global examination of Na8-Fe8-axial depth variations of mid-ocean ridge basalt (MORB) glass compositions from the Smithsonian database, we find that modeling of MORBs as the product of large variations in potential temperaure (Klein and Langmuir, 1987, JGR, 92, 8089) is not supported by Na8-Fe8-depth data for any ridge segment of any length. However, the observed inverse and positive Na8-Fe8 variations are in excellent agreement with the systematics of solidus melts in the plagioclase/spinel lherzolite transition in the CaO-MgO-Al2O 3-SiO2-Na2O-FeO system at 0.93-1.5 GPa, and 1240-1260˚C (Presnall et al., 2002, GCA, 66, 2073). This system contains all the main mantle mineral phases in this pressure range (ol, opx, cpx, pl, sp) and 99% of both the extracted melts and _ the source. Thus, chemical systematics of melts at the solidus provide very strong constraints on the major-element chemistry of melting processes. On the surface that defines solidus melt compositions in the pl/sp lherzolite transition interval, contours of constant pressure are nearly parallel to contours of constant MgO, but are at a high angle to contours of Na2O. An inverse Na8-Fe8 correlation occurs for melting at constant pressure.
    [Show full text]
  • Cretaceous to Cenozoic Tectonics of North America
    CRETACEOUS TO CENOZOIC TECTONICS OF NORTH AMERICA: FROM INTRAPLATE MAGMATISM TO INTRACONTINENTAL RIFTING --------------------------------------------------------------------------------- A Dissertation Presented to the Faculty of the Department of Earth and Atmospheric Sciences University of Houston --------------------------------------------------------------------------------- In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy --------------------------------------------------------------------------------- By Yiduo Andy Liu December 2016 CRETACEOUS TO CENOZOIC TECTONICS OF NORTH AMERICA: FROM INTRAPLATE MAGMATISM TO INTRACONTINENTAL RIFTING Yiduo Andy Liu APPROVED: Dr. Michael A. Murphy, Chairman Dr. Jonathan E. Snow Dr. Alexander C. Robinson Dr. Jolante van Wijk Dean, College of Natural Sciences and Mathematics ii ACKNOWLEDGEMENTS First and foremost, I am extremely grateful to my advisor Prof. Michael A. Murphy. He trained me in field mapping and critical thinking as a structural geologist, which is my primary goal for the PhD pursuit. He instructed me in detail how to write research proposals, which is an invaluable experience that not every student is trained on. He demonstrated to me what great leadership should look like. His persistence, after the brain surgery, deeply motivated me every time I thought about giving up. He taught me how to drive a van, lent me his pick-up truck for months, free, and he even showed up as the sole guest/photographer/witness at my “shotgun-style” wedding! Murphy is truly a role model. For the Gulf of Mexico magmatism chapter, I want to acknowledge Profs. Michael Murphy for initiating the project and providing free atmosphere for me to conduct research; Jonathan E. Snow for his patient guidance on how to understand geochemical data; Jolante van Wijk for significantly deepening my understanding and love of continental rift and subduction zone dynamics; Dale Bird, Stuart Hall, and Alexander C.
    [Show full text]
  • Anomalously Thin Transition Zone and Apparently Isotropic Upper Mantle Beneath Bermuda: Evidence for Upwelling
    Letter Volume 14, Number 10 17 October 2013 doi: 10.1002/ggge.20277 ISSN: 1525-2027 Anomalously thin transition zone and apparently isotropic upper mantle beneath Bermuda: Evidence for upwelling Margaret H. Benoit Department of Physics, College of New Jersey, Ewing, New Jersey, USA ([email protected]) Maureen D. Long Department of Geology and Geophysics, Yale University, New Haven, Connecticut, USA Scott D. King Department of Geosciences, Virginia Tech, Blacksburg, Virginia, USA [1] The origin of the Bermuda swell and volcanism remains enigmatic. The lack of an associated time- progressive hotspot track and absence of present-day volcanic activity make it difficult to reconcile with a deep mantle plume model. We analyze shear wave splitting measurements to estimate mantle flow direction and receiver function stacks to place constraints on the mantle transition zone thermal structure. ÃKS phases exhibit well-resolved null arrivals (no splitting) beneath the swell over a range of back azimuths. We find that the 410 and 660 km discontinuities are 49 6 5 km and 19 6 5 km deeper than the global average, respectively, leading to a transition zone thickness that is 27 6 4 km thinner than the average. Together, an apparently isotropic upper mantle and a thinned mantle transition zone suggest that mantle flow is primarily vertical beneath the swell, consistent with the presence of hot, buoyant mantle at depth. Components: 6,354 words, 4 figures. Keywords: hotspot; edge-driven convection; plume; mantle; Bermuda; Atlantic Ocean. Index Terms: 8121 Dynamics: convection currents, and mantle plumes: Tectonophysics; 3037 Oceanic hotspots and intraplate volcanism: Marine Geology and Geophysics; 9325 Atlantic Ocean: Geographic Location.
    [Show full text]
  • Geochronology of the Arkansas Alkaline Province, Southeastern United States Author(S): G
    Geochronology of the Arkansas Alkaline Province, Southeastern United States Author(s): G. Nelson Eby and Paulo Vasconcelos Source: The Journal of Geology, Vol. 117, No. 6 (November 2009), pp. 615-626 Published by: The University of Chicago Press Stable URL: http://www.jstor.org/stable/10.1086/605779 . Accessed: 21/10/2015 21:10 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Geology. http://www.jstor.org This content downloaded from 23.235.32.0 on Wed, 21 Oct 2015 21:10:48 PM All use subject to JSTOR Terms and Conditions Geochronology of the Arkansas Alkaline Province, Southeastern United States G. Nelson Eby and Paulo Vasconcelos1 Department of Environmental, Earth, and Atmospheric Sciences, University of Massachusetts, Lowell, Massachusetts 01854, U.S.A. (e-mail: [email protected]) ABSTRACT The Arkansas alkaline province (AAP) consists of intrusive bodies ranging in lithology from carbonatite and lamproite through nepheline syenite. Apatite and titanite fission-track ages fall into two groups—101–94 Ma and ∼88 Ma. New 40Ar/39Ar ages and those reported in the literature define a third age group of ∼106 Ma.
    [Show full text]
  • Origin of the Bermuda Volcanoes and Bermuda Rise: History, Observations, Models, and Puzzles
    1 Origin of the Bermuda volcanoes and Bermuda Rise: History, Observations, Models, and Puzzles Peter R Vogt Marine Science Institute University of California at Santa Barbara Woo-Yeol Jung Code 7420 Naval Research Laboratory Washington, DC 20375-5320 Abstract Deep-sea drilling on DSDP Leg 43 and on Bermuda itself, together with geophysical data (anomalies in basement depth, geoid and heat flow) and modeling have long suggested the uplift forming the Bermuda Rise, as well as the initial igneous activity that produced the Bermuda volcanoes, began ca. 47-40 Ma, during the early to middle part of the Midde Eocene. Some authors attribute 65 Ma igneous activity in Mississippi and 115 Ma activity in Kansas to a putative “Bermuda hotspot” or plume fixed in the mantle below a moving North America plate. While this is more or less consistent with hotspot traces computed from ‘absolute motion’ models, the hotspot/plume must resemble a lava lamp, turning off for up to 25 million years at a time, and/or be heavily influenced by lithosphere structure. Moreover, Cretaceous igneous activity in Texas and Eocene intrusions in Virginia then require separate mantle “blobs”. The pillow lavas forming the original Bermuda shield volcano have not been reliably dated, and the three associated smaller edifices have not been drilled or dated. A well-dated (ca. 33-34 Ma) episode of unusually titaniferous sheet intrusion in the Bermuda edifice was either triggered by plate-wide stress changes or reflects local volcanogenic events deep in the mantle source region. The high Ti and Fe of the Bermuda intrusive sheets probably relate to the very high amplitude magnetic anomalies discovered on the islands.
    [Show full text]