Science.gov

Sample records for miocene hawthorn group

  1. Hawthorn

    MedlinePLUS

    ... Hawthorn is a spiny, flowering shrub or small tree of the rose family. The species of hawthorn discussed here are native to northern European regions and grow throughout the world. Historically, hawthorn fruit has been used for heart ...

  2. Origin of dolomite in the phosphatic Hawthorne Group of Florida

    SciTech Connect

    Compton, J.S.; Hall, D.L.; Mallinson, D.J. . Dept. of Marine Science); Hodell, D.A. . Dept. of Geology)

    1994-07-01

    In addition to large amounts of phosphorite, the Miocene Hawthorn Group of Florida contains abundant dolomite. Dolomite is present as disseminated silt-size rhombs, as friable dolosilt beds, and as pore-filling cement in dolostone beds and clasts. The dolomite formed during early burial diagenesis both in the sulfate-reduction zone, overlapping and extending below sediment depths of phosphorite formation, and in adjacent, nonphosphatic, shallow-water lagoonal environments. Much of the dolomite is closely associated with the fibrous, Mg-rich clay minerals palygorskite and sepiolite. The percent carbonate in the Hawthorn Group increases from north to south; the dominant carbonate mineral in north Florida is dolomite, whereas dolomite and calcite are both abundant in south Florida. The [delta][sup 13]C values of the dolomite, from +1.82 to [minus]6.21[per thousand] PDB, suggest that metastable biogenic carbonate (aragonite and high-Mg calcite) and seawater were the predominant sources of carbonate. However, negative [delta][sup 13]C values of dolomite from northeast Florida suggest that as much as 30--40% of the carbonate was derived from degradation of organic matter. Degradation of organic matter enhanced dolomitization by removing sulfate ion and increasing the carbonate alkalinity of the pore waters. The oxygen and strontium isotopic values along with moderate Na contents indicate a marine origin. Evaporation of seawater or mixing of seawater and meteoric water were apparently not major factors in dolomite formation. The presence of dolomite, along with phosphorite, in reworked sequences can indicate deposition of organic-rich sediments from which most of the organic matter has since been removed.

  3. Hawthorne Control Procedures in Educational Experiments: A Reconsideration of Their Use and Effectiveness.

    ERIC Educational Resources Information Center

    Adair, John G.; And Others

    A meta-analysis was conducted on 44 educational studies that used either a (labelled) Hawthorne control group, a manipulation of Hawthorne effects, or a group designed to control for the Hawthorne effect. The sample included published journal articles, ERIC documents or unpublished papers, and dissertations. The studies were coded on 20 variables,

  4. Hawthorne Control Procedures in Educational Experiments: A Reconsideration of Their Use and Effectiveness.

    ERIC Educational Resources Information Center

    Adair, John G.; And Others

    1989-01-01

    A descriptive analysis of research practices and a meta-analysis of control group effect sizes are used to address Hawthorne effects in educational experiments. The analysis of 86 studies and 256 treatment/Hawthorne/no-treatment control group effect size comparisons indicate that artifact controls have limited utility in dealing with the Hawthorne

  5. Process Writing with Hawthorne.

    ERIC Educational Resources Information Center

    Edwards, Lita R.

    Teachers can use the process writing format for many assignments to teach and refine more skills than are often incorporated in older methods, and this is exemplified by a teaching unit comparing two short stories by Nathaniel Hawthorne. Peer conferences and peer editing in the revision stages, which are features of the process model, can lead to

  6. Programmed Student Achievement: A Hawthorne Effect?

    ERIC Educational Resources Information Center

    Haddad, Nabil F.; And Others

    1975-01-01

    Three groups of college students were given instructions using different testing techniques to determine whether the superior performance obtained with Programed Student Achievement (PA) was due to a Hawthorne Effect. Results seem to preclude any attempt to interpret the effectiveness of PA on that basis. (Editor/JT)

  7. Hawthorne Academy: The University Perspective

    ERIC Educational Resources Information Center

    Frazee, Bruce M.; Frazee, Felicia F.

    2005-01-01

    This article revisits the Trinity University and Hawthorne School partnership since the first case study written 10 years ago. This new perspective analyzes the teacher education program-particularly beliefs and attitudes about it and changes made to the program-with an eye to two primary themes: preparing future teachers and Hawthorne's Core

  8. The Hawthorne Misunderstanding (and How to Get the Hawthorne Effect in Action Research).

    ERIC Educational Resources Information Center

    Gottfredson, Gary D.

    1996-01-01

    Examines the original Hawthorne relay-assembly research. Asserts the "Hawthorne misunderstanding" is common in criminology and criminal justice because authors have failed to properly attribute the explanation of increased work output to the Hawthorne effect. Describes the Hawthorne effect, how it is produced, and ways to achieve the Hawthorne

  9. Hawthorn Extract Randomized Blinded Chronic Heart Failure (HERB CHF) Trial

    PubMed Central

    Zick, Suzanna M.; Vautaw, Bonnie Motyka; Gillespie, Brenda; Aaronson, Keith D.

    2009-01-01

    Aims Hawthorn's efficacy when added to contemporary evidence-based heart failure therapy is unknown. We aimed to determine whether hawthorn increases submaximal exercise capacity when added to standard medical therapy. Methods and results We performed a randomized, double-blind, placebo-controlled trial in 120 ambulatory patients aged ?18 years with New York Heart Association (NYHA) class II-III chronic heart failure. All patients received conventional medical therapy, as tolerated, and were randomized to either hawthorn 450 mg twice daily or placebo for 6 months. The primary outcome was change in 6 min walk distance at 6 months. Secondary outcomes included quality of life (QOL) measures, peak oxygen consumption, and anaerobic threshold during maximal treadmill exercise testing, NYHA classification, left ventricular ejection fraction (LVEF), neurohormones, and measures of oxidative stress and inflammation. There were no significant differences between groups in the change in 6 min walk distance (P = 0.61), or on measures of QOL, functional capacity, neurohormones, oxidative stress, or inflammation. A modest difference in LVEF favoured hawthorn (P = 0.04). There were significantly more adverse events reported in the hawthorn group (P = 0.02), although most were non-cardiac. Conclusion Hawthorn provides no symptomatic or functional benefit when given with standard medical therapy to patients with heart failure. This trial is registered in ClinicalTrials.gov ID: NCT00343902. PMID:19789403

  10. The Miocene Topanga Group of Southern California - A 100-Year History of Changes in Stratigraphic Nomenclature

    USGS Publications Warehouse

    Campbell, Russell H.; McCulloh, Thane H.; Vedder, John G.

    2007-01-01

    A review of selected literature summarizes the origin and chronology of changes in usage of 'Topanga' in the Miocene stratigraphic nomenclature of the Los Angeles Basin and adjacent areas in southern California. The review was done to summarize and reconcile some differences in Miocene stratigraphic nomenclature as applied to geologic map compilations of the Santa Ana (Morton, 2004), San Bernardino (Morton and Miller, 2003), Long Beach (Saucedo and others, 2003) and Los Angeles (Yerkes and Campbell, 2005) 30' x 60' quadrangles, all of which are products of the cooperative (California Geological Survey-U.S. Geological Survey) Southern California Areal Mapping Project (SCAMP). The deposition of the Topanga Group spans about 6 my (from as old as about 18 ma to as young as about 12 ma), and the sequence of included strata records changes in provenance and depositional environments that are contemporaneous with part of a major Miocene tectonic episode in southern California -- the 'basin-inception phase' in the evolution of the Neogene Los Angeles basin (Yerkes and others, 1965). The area of Topanga deposition extends to the southern, eastern, northern, and northwestern sides of the Los Angeles basin, as well as the southern part of the eastern Ventura Basin. Topanga beds are inferred to underlie the thick upper Miocene and Pliocene deposits of the central Los Angeles Basin and the southern part of the eastern Ventura Basin; however, they have been reached by drilling only in marginal areas, where the overlying deposits are relatively thin. Post-Topanga strata were deposited in more-restricted areas of rapid subsidence. Selected papers are summarized as they relate to the Topanga nomenclature, and are presented in chronological order.

  11. A Hawthorne strategy: implications for performance measurement and improvement.

    PubMed

    Lied, T R; Kazandjian, V A

    1998-01-01

    The Hawthorne experiments are a backdrop for diverse studies assessing the impact of treatment and experimentation on human and organizational performance. The Hawthorne effect is used to describe the positive impact on behavior that sometimes occurs in a study or experiment as a result of the interest shown by the experimenter in humans who are being treated, studied, or observed. We propose that the Hawthorne effect can be viewed as an active construct to develop a coherent strategy for performance improvement. We propose a "Hawthorne strategy" that transcends the Hawthorne effect in that it offers an approach to improving performance indefinitely. This strategy uses external observations of performance to increase internal commitment to performance improvement. The focus of individual responsibility increases as does the perceived connection between individual efforts and external performance improvement. The sense of accountability is maintained by institutional recognition and periodic reinforcement of individual behaviors that contribute to performance improvement. A successful Hawthorne strategy encourages providers of care to be evaluators of their performance as individuals, as members of groups, and as members of institutions. PMID:10351289

  12. What Caused the Hawthorne Effect?

    ERIC Educational Resources Information Center

    Parsons, H. McIlvaine

    1978-01-01

    Together, information feedback and differential reward could account for the gradually increasing productivity in the Hawthorne plant, especially in an explanatory framework of response shaping in operant conditioning. (Author/IRT)

  13. The Hawthorne Misunderstanding (and How to Get the Hawthorne Effect in Action Research).

    ERIC Educational Resources Information Center

    Gottfredson, Gary D.

    1996-01-01

    Examines the original Hawthorne relay-assembly research. Asserts the "Hawthorne misunderstanding" is common in criminology and criminal justice because authors have failed to properly attribute the explanation of increased work output to the Hawthorne effect. Describes the Hawthorne effect, how it is produced, and ways to achieve the Hawthorne…

  14. 11. Photocopy of photograph (original located in Photograph's Office, Hawthorne ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Photocopy of photograph (original located in Photograph's Office, Hawthorne Army Ammunition Plant, Hawthorne, Nevada). View of gymnasium, photograph no. 20107-28. - Hawthorne Naval Ammunition Depot, Gymnasium, North Main Avenue, Industrial Area, Hawthorne Army Ammunition Plant, Hawthorne, Mineral County, NV

  15. 12. Photocopy of photograph (original located in Photograph's Office, Hawthorne ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. Photocopy of photograph (original located in Photograph's Office, Hawthorne Army Ammunition Plant, Hawthorne, Nevada). View of swimming pool, photograph no. 20107-27. - Hawthorne Naval Ammunition Depot, Gymnasium, North Main Avenue, Industrial Area, Hawthorne Army Ammunition Plant, Hawthorne, Mineral County, NV

  16. Late Miocene diversification and phylogenetic relationships of the huge toads in the Rhinella marina (Linnaeus, 1758) species group (Anura: Bufonidae).

    PubMed

    Maciel, Natan Medeiros; Collevatti, Rosane Garcia; Colli, Guarino Rinaldi; Schwartz, Elisabeth Ferroni

    2010-11-01

    We investigated the phylogeny and biogeography of the Rhinella marina group, using molecular, morphological, and skin-secretion data, contributing to an understanding of Neotropical faunal diversification. The maximum-parsimony and Bayesian analyzes of the combined data recovered a monophyletic R. marina group. Molecular dating based on Bayesian inferences and fossil calibration placed the earliest phylogenetic split within the R. marina group at ? 10.47 MYA, in the late Miocene. Two rapid major diversifications occurred from Central Brazil, first northward (? 8.08 MYA) in late Miocene and later southward (? 5.17 MYA) in early Pliocene. These results suggest that barriers and dispersal routes created by the uplift of Brazilian Central Shield and climatic changes explain the diversification and current species distributions of the R. marina group. Dispersal-vicariance analyzes (DIVA) indicated that the two major diversifications of the R. marina group were due to vicariance, although eleven dispersals subsequently occurred. PMID:20813190

  17. An Observation of Hawthorne Effect in an Experiment in the Teaching of Reading in First Grade: A Hypothesis

    ERIC Educational Resources Information Center

    McCracken, Robert A.

    1968-01-01

    Speculates about the presence of a negative Hawthorne effect on a control group in addition to a positive effect on the experimental group in an experiment involving 2 first-grade teachers and their classes, and draws implications for studies which seek to control for possible interference by positive and negative Hawthorne effects. Bibliography.

  18. The Hawthorne Effect: A Fresh Examination.

    ERIC Educational Resources Information Center

    Diaper, Gordon

    1990-01-01

    Reexamines definitions of and explanations for the Hawthorne Effect in research subjects. Notes that the Hawthorne Effect was tested in a study of the effectiveness of paired classroom reading among students. Challenges the notion that subject's behavior is modified by participation in research. Reviews various research studies that question the

  19. Characterization of antioxidants present in hawthorn fruits.

    PubMed

    Zhang, Z; Chang, Q; Zhu, M; Huang, Y; Ho, W K.K.; Chen, Z -Y.

    2001-03-01

    Hawthorn fruit extract has been shown to have many health benefits including being cardiovascular protective, hypotensive and hypocholesterolemic. The present study was carried out to characterize further the antioxidants of hawthorn fruit and their effect on the oxidation of human low density lipoprotein (LDL) and alpha-tocopherol. The dry hawthorn fruit was extracted successively with ether, ethyl acetate, butanol and water. The ethyl acetate fraction was only effective in inhibition of Cu(+2)-mediated LDL oxidation. The column chromatographic separation led to isolation of eight pure compounds; namely, ursolic acid, hyperoside, isoquercitrin, epicatechin, chlorogenic acid, quercetin, rutin and protocatechuic acid. All of these phenolic compounds, except ursolic acid, were protective to human LDL from Cu(+2)-mediated LDL oxidation. They were also effective in preventing the peroxy free radical-induced oxidation of alpha-tocopherol in human LDL. The inhibitory effect of these compounds on oxidation of LDL and alpha-tocopherol was dose-dependent at concentrations ranging from 5 to 40 M. In addition, supplementation of 2% hawthorn fruit powder significantly elevated serum alpha-tocopherol by 18-20% in rats fed a 30% polyunsaturated canola oil diet, as compared with the control. The present results suggest that part of the mechanism for cardiovascular protective effects of hawthorn fruit might also involve the direct protection to human LDL from oxidation or indirect protection via maintaining the concentration of alpha-tocopherol in human LDL. PMID:11257463

  20. The Hawthorne Effect in Infection Prevention and Epidemiology.

    PubMed

    Chen, Luke F; Vander Weg, Mark W; Hofmann, David A; Reisinger, Heather Schacht

    2015-12-01

    The Hawthorne Effect is a prevalent observer effect that causes behavioral changes among participants of epidemiological studies or infection control interventions. The purpose of the review is to describe the origins of the Hawthorne Effect, to understand the term in relation to current scientific literature, to describe characteristics of the Hawthorne effect, and to discuss methods to quantify and overcome limitations associated with the Hawthorne Effect. PMID:26383964

  1. A "H--ll-Fired Story": Hawthorne's Rhetoric of Rumor.

    ERIC Educational Resources Information Center

    Harshbarger, Scott

    1994-01-01

    Considers Nathaniel Hawthorne's literary technique of providing various, often conflicting, accounts of a narrative scene or event. Analyzes Hawthorne's rhetoric of rumor as featured in "The Scarlet Letter." Shows how Hawthorne tried to translate the dynamics of interpersonal communication into print in this novel. (HB)

  2. The Hawthorne effect and energy awareness.

    PubMed

    Schwartz, Daniel; Fischhoff, Baruch; Krishnamurti, Tamar; Sowell, Fallaw

    2013-09-17

    The feeling of being observed or merely participating in an experiment can affect individuals' behavior. Referred to as the Hawthorne effect, this inconsistently observed phenomenon can both provide insight into individuals' behavior and confound the interpretation of experimental manipulations. Here, we pursue both topics in examining how the Hawthorne effect emerges in a large field experiment focused on residential consumers' electricity use. These consumers received five postcards notifying, and then reminding, them of their participation in a study of household electricity use. We found evidence for a Hawthorne (study participation) effect, seen in a reduction of their electricity use--even though they received no information, instruction, or incentives to change. Responses to a follow-up survey suggested that the effect reflected heightened awareness of energy consumption. Consistent with that interpretation, the treatment effect vanished when the intervention ended. PMID:24003110

  3. The Hawthorne effect and energy awareness

    PubMed Central

    Schwartz, Daniel; Fischhoff, Baruch; Krishnamurti, Tamar; Sowell, Fallaw

    2013-01-01

    The feeling of being observed or merely participating in an experiment can affect individuals behavior. Referred to as the Hawthorne effect, this inconsistently observed phenomenon can both provide insight into individuals' behavior and confound the interpretation of experimental manipulations. Here, we pursue both topics in examining how the Hawthorne effect emerges in a large field experiment focused on residential consumers electricity use. These consumers received five postcards notifying, and then reminding, them of their participation in a study of household electricity use. We found evidence for a Hawthorne (study participation) effect, seen in a reduction of their electricity useeven though they received no information, instruction, or incentives to change. Responses to a follow-up survey suggested that the effect reflected heightened awareness of energy consumption. Consistent with that interpretation, the treatment effect vanished when the intervention ended. PMID:24003110

  4. Paleomagnetism of the Miocene Jantetelco Granodiorites and Tepexco Volcanic Group and inferences for crustal block rotations in central Mexico - Reevaluation

    NASA Astrophysics Data System (ADS)

    Duarte, Alma Vàzquez; Böhnel, Harald; Yutsis, Vsevolod

    2015-09-01

    Miocene igneous rocks from a location in central Mexico provide paleomagnetic data that allow re-evaluation of previous data by Urrutia-Fucugauchi (1981) that were interpreted to suggest a counter clockwise rotation of a crustal block by about 50°. We sampled 31 sites from the Miocene trondhjemitic Chalcatzingo domes, the Tepexco volcanic group, and the Xalostoc diorite, covering the same area of approximately 50 km2 about 90 km SE of Mexico City. Magnetic analysis shows that these rocks contain magnetic phases of variable composition, with Curie temperatures characteristic for magnetite, but often accompanied by lower Curie temperature components. Magnetic hysteresis measurements point to the presence of PSD particles, and in combination these properties suggest that these rocks are also suitable for paleomagnetic study. Scanning electron microscope analysis supports the rock magnetic results, indicating the presence of magnetite and high-intermediate titanium titanomagnetite in many samples. Demagnetization experiments showed in most cases characteristic remanence directions of reasonable to good quality, and for 26 sites mean directions could be determined. Of these 14 (12) are of normal (reverse) polarity. Overall mean directions of normal and reverse sites are antipodal and pass a reversal test at the 95% probability level. The paleodirection from 26 sites is D = 348.1°E, I = 35.7°, α95 = 7.4°, and the paleopole is located at Lat = 78.3°N, Long = 184.2°E, A95 = 7.0°, which is indistinguishable from the 20 Ma reference pole for the stable North America plate. These data do not support any tectonic deformation of the sampling area since the Miocene. Based on the number of sites studied, their rock magnetic characteristics, and the quality of the magnetic remanence that results in a positive reversal test, we consider our data to be reliable and we therefore suggest that this result supersedes that of Urrutia-Fucugauchi (1981). The reason for this previous and much different result remains unknown.

  5. 77 FR 64889 - Amendment of Class D and Class E Airspace; Hawthorne, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-24

    ... Administration 14 CFR Part 71 Amendment of Class D and Class E Airspace; Hawthorne, CA AGENCY: Federal Aviation... description for Class D and Class E airspace at Jack Northrop Field/Hawthorne Municipal Airport, Hawthorne, CA... Class D and E airspace at Jack Northrop Field/Hawthorne Municipal Airport, Hawthorne, CA. The...

  6. Vertebrate-bearing eolian unit from the Ogallala Group (Miocene) in northwestern Texas

    SciTech Connect

    Winkler, D.A.

    1987-08-01

    The upper Couch Formation is part of the lower of two formations composing the Ogallala Group in Blanco and Yellowhouse canyons in northwestern Texas. An eolian origin for the upper Couch Formation is indicated by its mean grain size, pedogenic carbonate nodules, massive bedding, and blanketlike morphology. The unit conforms poorly to the usual eolian depositional models; it resulted from a combination of the processes involved in loess and sand-sheet formation. Grassland or savanna vegetation probably existed over the area and aided in sediment trapping. Vertebrates are unusual in eolian units, but the adaptations and mode of preservation of those in the upper Couch Formation also support an eolian interpretation. This and other widespread silty sand sheets in the Ogallala indicate major fluctuations in depositional style, possibly climatically controlled. Lateral continuity and preservation of vertebrates give silty sand sheets great potential as correlation tools.

  7. Correlation and analysis of Miocene paleochannels in the central Sierra Nevada, California, as displayed by the Stanislaus Group

    NASA Astrophysics Data System (ADS)

    Jones, S.; Pluhar, C. J.; Farner, M. J.; Deino, A. L.

    2013-12-01

    The proposed Neogene uplift of the Sierra Nevada has been debated for several decades. Although multiple lines of evidence indicate substantial uplift of the Sierran crest over the last ten million years, recent isotopic and paleobotanical methods have called the validity of these calculations into question. Our study focuses on the discontinuous units of the Miocene Stanislaus Group: Table Mountain Formation lavas, Dardenelles Formation lavas, and Eureka Valley Tuff (EVT) lava and tuffs. These units are significant because they have been used as a tilt indicator to calculate the uplift of the Sierra Nevada crest since their emplacement, 9.0-10.2 million years ago. Our research increased the quantity of primary data, which will be used to develop and verify a digitally-derived model of the paleodrainage systems of the ancient Sierra Nevada. The localities, Dorrington, Pikes Peak, Rancheria Mountain, Three Chimneys, and Sonora Pass are significant because they may represent the few remaining Table Mountain Formation (trachyandesite) outcrops of previously unmapped paleodrainage channels. To test this hypothesis, geochemical and paleomagnetic data were used to correlate the localities and thereby reconstruct the paleochannels. Outcrops near Dorrington, California contain biotite, display eutaxitic textures and are characterized by a reverse polarity indistinguishable from the Tollhouse Flat Member of the EVT. Previously mapped as Table Mountain Latite, we reclassify these units as Tollhouse Flat Member and eliminate the hypothesis that the units were once part of a potentially lava-back-flooded tributary of the paleo-Stanislaus River. The high potassium, columnar jointed lava at Pikes Peak, exhibits normal polarity; it is plausibly part of the Stanislaus Group and may be correlated to flows along the main 'cataract channel' of the Stanislaus Group. Results from Rancheria Mountain verify the presence of Stanislaus Group lavas and the EVT, previously mapped by Huber et al. (1989). The normal polarity trachyandesite lavas, which have a limited distribution, may be locally sourced; the reversed polarity lavas correlate to outcrops near the Stanislaus Group source area at Little Walker Caldera. Mapping near Three Chimneys confirms the presence of the EVT and a capping trachyandesite lava previously mapped by Huber (1983). We show that the capping lava is younger than the EVT and thus cannot be Table Mountain Formation, as attributed by Huber (1983). This high potassium normal-polarity lava could be part of the Lava Flow Member of the EVT or the Dardanelles Formation. Lastly, Ar/Ar geochronology on the reversed polarity lava of the 'Table Mountain Event' geomagnetic excursion within the Table Mountain Formation suggests that the dated lava erupted during the subchron C5n.2n-1, the first known direct dating of volcanic rocks of this subchron.

  8. 75 FR 17406 - Hawthorn Oil Transportation; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-06

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Hawthorn Oil Transportation; Notice of Filing March 31, 2010. Take notice that on February 12, 2010, Hawthorn Oil Transportation submitted a request for the waiver of...

  9. 77 FR 7525 - Revision of Class D and Class E Airspace; Hawthorne, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-13

    ... Federal Aviation Administration 14 CFR Part 71 Revision of Class D and Class E Airspace; Hawthorne, CA... Class D and Class E airspace at Jack Northrop Field/Hawthorne Municipal Airport, Hawthorne, CA... amend controlled airspace at Hawthorne, CA (76 FR 67103). Interested parties were invited to...

  10. AN OBSERVATION ABOUT HAWTHORNE EFFECT IN AN EXPERIMENT IN THE TEACHING OF READING IN FIRST GRADE--A HYPOTHESIS.

    ERIC Educational Resources Information Center

    MCCRACKEN, ROBERT A.

    THE PURPOSE OF THIS STUDY WAS TO DETERMINE IF A HAWTHORNE EFFECT WERE PRESENT IN A 3-YEAR LONGITUDINAL STUDY WHICH COMPARED TWO METHODS OF TEACHING READING IN FIRST GRADE. THE INITIAL SUBJECTS WERE TWO TEACHERS AND FIVE FIRST-GRADE CLASSES OF RANDOMLY ASSIGNED STUDENTS WHO COMPOSED ONE EXPERIMENTAL, ONE CONTROL, AND THREE SUBCONTROL GROUPS.

  11. Hawthorne Concept--Does It Affect Reading Progress?

    ERIC Educational Resources Information Center

    Rubeck, Patricia A.

    1975-01-01

    Concludes that the extra attention paid to children during the administration of reading tests does not have a significant effect on test performance and that the Hawthorne effect does not influence reading test results. (RB)

  12. Meeting the dark: autobiography in Hawthorne's unfinished tales.

    PubMed

    Loughman, C

    1992-12-01

    This essay discusses the autobiographical implications of Nathaniel Hawthorne's last, unfinished tales. Biographical documents, as well as the tales, demonstrate that Hawthorne's personal condition shaped the characters and ideas in his fiction, particularly the aged protagonist, the meditations on old age and death, and the quest for immortality. The conflict between the moral vision in the tales and his personal attitude toward old age and death caused creative difficulties that he could not overcome. PMID:1478489

  13. Miocene-to-Quaternary oblique rifting signature in the Western Ross Sea from fault patterns in the McMurdo Volcanic Group, north Victoria Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Vignaroli, Gianluca; Balsamo, Fabrizio; Giordano, Guido; Rossetti, Federico; Storti, Fabrizio

    2015-08-01

    Mt. Overlord and Mt. Melbourne are part of the fossil-to-active eruptive centre belt of the McMurdo Volcanic Group, located along the western shoulder of the West Antarctic Rift System in north Victoria Land (Antarctica). The formation and localisation of these volcanic centres are intimately connected to the regional fault patterns associated with Neogene transtensional stretching in the West Antarctic Rift System. This study reports about 900 structural data of faults and fault-related joints affecting the Miocene-Pliocene deposits of Mt. Overlord and the Plio-Quaternary deposits of Mt. Melbourne. Fault surfaces strike along three main directions (NW-SE, NE-SW, and N-S) with high (> 70) dip angles. The reconstructed fault geometries and kinematics document a NW-SE strike-slip fault system having dextral motion in the Mt. Overlord area, which evolves into a more complex structural architecture characterised by transtensional deformations in the Mt. Melbourne area, where volcanism is still active. The fault array can be reconciled with principal and subordinate deformation structures developed at the termination region of NW-SE intraplate strike-slip fault systems inducing oblique rifting in the West Antarctic Rift System. The structural dataset, integrated with available geochronological constraints, gives rise to a two-step (Miocene-to-Holocene) tectonic scenario in which the spatial migration of the volcanic activity towards the eastern boundary of the Transantarctic Mountains occurred during the evolution of the West Antarctic Rift System.

  14. The Effectiveness of Crataegus orientalis M Bieber. (Hawthorn) Extract Administration in Preventing Alveolar Bone Loss in Rats with Experimental Periodontitis

    PubMed Central

    Hatipo?lu, Mkerrem; Sa?lam, Mehmet; Kseo?lu, Serhat; Kksal, Ekrem; Kele?, Ali; Esen, Hac? Hasan

    2015-01-01

    The purpose of this animal study was to evaluate the effects of hawthorn (Crataeus orientalis M Bieber.) extract on serum oxidative status and alveolar bone loss in experimental periodontitis. Twenty-seven Wistar rats were assigned to one of the following groups: non- ligated+placebo (saline) (NL, n = 9), ligature only+placebo (saline) (LO, n = 9), and ligature and treated with hawthorn extract in saline (H, n = 9) (100 mg/kg orogastrically, once a day for 11 days). Periodontitis was induced by submerging a 4/0 silk ligature in the sulcus of the mandibular right first molars of rats, and the animals were sacrificed after 11 days. Micro-CT examinations were performed for linear and volumetric parameter assessment of alveolar bone. Periodontal tissues were histopathologically examined to assess the differences among the study groups. Levels of serum total antioxidant status (TAS)/total oxidant status (TOS), and oxidative stress index (OSI) were also analyzed. Alveolar bone loss was significantly reduced by hawthorn administration compared to LO group (p<0.05). The number of inflammatory cells and osteoclasts in the LO group was significantly higher than that of the NL and H groups (p< 0.05). The number of osteoblasts in the LO and H groups was significantly higher than that of the NL group (p<0.05). TOS and OSI levels were significantly reduced in H group compared to LO group (P <0.05) and TAS levels were similar in H and NL group (p< 0.05). Hawthorn extract showed inhibitory effect on periodontal inflammation and alveolar bone loss by regulating TAS, TOS and OSI levels in periodontal disease in rats when administered systemically. PMID:26030160

  15. Sedimentology of the Whiteclay Gravel Beds (Ogallala Group) in northwestern Nebraska, USA: Structurally controlled drainage promoted by Early Miocene uplift of the Black Hills Dome

    NASA Astrophysics Data System (ADS)

    Fielding, Christopher R.; LaGarry, Hannan E.; LaGarry, Leigh Anne; Bailey, Bruce E.; Swinehart, James B.

    2007-11-01

    The newly recognized Whiteclay Gravel Beds (WGB) of the Miocene Ogallala Group crop out as a narrow, discontinuous ribbon of sands and gravels in Dawes and Sheridan Counties, northwestern Nebraska, USA. The WGB are exposed in a series of municipal gravel quarries and natural exposures that define a linear trench in underlying strata at least 20 m deep and up to 300 m wide, with short, southeast-trending reaches separating generally longer east-trending sections. This gravel-filled trench can be recognized from the Nebraska-South Dakota border near Whiteclay, Nebraska southeastward to east of Gordon, Nebraska, a distance of 30 km. The outcrop belt of the WGB is coincident in location and trend with the Whiteclay Fault Zone. Where exposed in quarries, the walls of the trench are steep-sided, vertical, or locally overhanging. Polished surfaces, slickensides, and parallel joint sets are common in the walls of the trench near Whiteclay, but uncommon in those to the east. The narrow belt defined by this trench is filled by stratified gravel (< 2.0 m, typically < 0.3 m) of sedimentary lithologies derived from various Cenozoic units (but principally Anderson Ranch Formation), and sand. Relatively small amounts of unrounded granitic, volcanic, and quartz gravel are preserved in places. Cross-bedding and clast imbrication indicate palaeoflow towards the east. The WGB are interpreted to have formed in response to tectonic upheaval associated with uplift of the Black Hills of South Dakota in Early Miocene times. Fault rupture topography facilitated formation of a steep-sided canyon, or valley, up to 20 m deep, being virtually straight with sharp bends at intervals of several km. An alluvial channel belt developed in the floor of the valley, filling the available accommodation space with coarse sand and gravel via aggradational stacking of the deposits of successive channels and channel belts. Channel belts were probably braided, with individual channels up to 4 m deep and a few tens of metres wide. The multi-storey character of the deposit indicates multiple episodes of cutting and filling. The coarse grain-size of the fill suggests energetic discharge with frequent bankfull flows, even though the system had a relatively low gradient (0.004). An abundance of reworked fossil debris is derived from several stratigraphic units, clasts of which have been identified in the fill. The presence of a contemporary merychippine horse and a primitive species of the oreodont Brachycrus constrain formation of the WGB to a short interval within the Early Miocene (c. 17.5 Ma). The mammal fauna suggests that this stream was a valuable source of water, while fragments of aquatic organisms such as turtles and fish indicate perennial discharge. The WGB provides a crucial window into a pluvial period in the Miocene that is largely unpreserved elsewhere in the basin, facilitated in part by fault rupture topography.

  16. Secular variation of the middle and late Miocene geomagnetic field recorded by the Columbia River Basalt Group in Oregon, Idaho and Washington, USA

    NASA Astrophysics Data System (ADS)

    Dominguez, Ada R.; Van der Voo, Rob

    2014-06-01

    This study of 118 discrete volcanic flows from the Columbia River Basalt Group is aimed to determine their distribution of geomagnetic field directions and virtual geomagnetic poles (VGPs) and to compare the inherent secular variation parameters with those from other studies. The magnetic signature of these rocks is uniformly carried by primary titanomagnetite, indicating that magnetic changes are due to variations in the magnetic field. Although most flows are flat lying, those that are tilted pass the Tauxe and Watson tilt test. Sequential flows with statistically similar site means were grouped, and directions that were considered outliers were evaluated and removed using the Vandamme cut-off method. Three normal-polarity (N-polarity) and three reversed-polarity (R-polarity) intervals are revealed by the stratigraphically ordered flows and have mean directions of N polarity (dec/inc = 6.6°/+61.2°, k = 29.3, α95 = 4.2°), and R polarity (dec/inc = 178.2°/-59.2°, k = 16, α95 = 5.5°). Regression analysis indicates that the secular variation analysis has not been affected by regional rotation, and that apparent polar wander is negligible. The VGP distribution is almost perfectly circular and supports the preference of VGP positions for the dispersion analysis. Dispersion parameters with corrections for within-site scatter (Sb) show a range of 14.3°-25.5°, including error limits, and were consistently higher for R-polarity results than for those of N polarity. Published dispersion parameters for extrusives <5 Ma show Sb values slightly lower than ours, yielding values of 16°-19°, although the difference is not statistically significant. In contrast, published dispersion parameters from high quality data from the Cretaceous Normal Superchron are lower than those for the Neogene, which suggests that the noisiness of the magnetic field correlates with the frequency of reversals. Our new results allow us to extend the Plio-Pleistocene palaeosecular variation database to the bottom of the middle Miocene. Many Miocene formations on a variety of continents are suitable targets for future analysis. Furthermore, the significant difference between the reversed and N-polarity dispersion parameters is intriguing and needs substantiation.

  17. Is the Hawthorne Effect in Educational Experiments a Chimera?

    ERIC Educational Resources Information Center

    Bauernfeind, Robert H.; Olson, Carl J.

    1973-01-01

    Reports on an experimental study designed to investigate the relationship between two factors commonly regarded as components of the Hawthorne Effect on pupil performance and on intellectual task. These factors are (1) direct cue, or awareness of experimentation, as represented by an announcement that pupils were the subjects of an experiment; and

  18. In Praise of the Hawthorne Effect: Perspectives from the Profs.

    ERIC Educational Resources Information Center

    Raywid, Mary Anne

    1979-01-01

    Successful teacher education and effective teacher and student motivation may be obtainable through a positive approach to the Hawthorne Effect, which is the principle that increased attention to an operative situation leads to an increased productivity by that operation, regardless of all other surrounding variables. (LH)

  19. Mozart, Hawthorne, and Mario Savio: Aesthetic Power and Political Complicity.

    ERIC Educational Resources Information Center

    Herbert, T. Walter

    1995-01-01

    Discusses the false dichotomy pitting aesthetic power against political complicity in literary criticism. Considers the sexual politics of the household of Nathaniel Hawthorne in light of this opposition. Suggests how literary works keep warring voices and inner conflicts alive and at odds. (HB)

  20. Nathaniel Hawthorne's Garden of Eden Story: "Rappaccini's Daughter."

    ERIC Educational Resources Information Center

    Meixner, Linda L.

    1990-01-01

    Presents a four-day lesson plan for secondary U.S. literature or Bible-and-literature classes, using the Garden of Eden story and Nathaniel Hawthorne's "Rappaccini's Daughter." Identifies objectives, materials, procedure, and evaluation measures. Develops students' ability to discover analogies and irony in literary texts. Lists teacher resources,

  1. Nathaniel Hawthorne and Herman Melville: A Research Guide.

    ERIC Educational Resources Information Center

    Van Noate, Judith, Comp.

    This handout is a guide to library resources in the J. Murrey Atkins Library at the University of North Carolina-Charlotte for the study of the 19th-century American authors Nathaniel Hawthorne and Herman Melville. The guide details resources in Atkins library for biographical and critical material on the two authors. The guide is in four

  2. Community Recreation Center greenhouse solar collector, Hawthorne, Nevada. Final report

    SciTech Connect

    Not Available

    1981-04-01

    A solar collector greenhouse and a trombe wall are proposed for the south wall of the Community Recreation Center, Hawthorne, Nevada. The project was integrated with retrofit of an old gymnasium that is still in progress. Thermometers are being used to monitor temperatures inside the greenhouse, inside the gymnasium, and in the outdoors. (BCS)

  3. Screening low fire blight susceptible Crataegus species for host suitability to hawthorn leaf-curling aphids (Dysaphis spp.).

    PubMed

    Bribosia, E; Bylemans, D; Van Impe, G; Migon, M

    2002-01-01

    The group of hawthorn leaf-curling aphids (Dysaphis spp.) hosted by the common hawthorn Crataegus monogyna Jacq. may play an important role in the biological control of the rosy apple aphid, Dysaphis plantaginea (Passerini), by increasing reproduction opportunities for the indigenous hymenopteran parasitoid Ephedrus persicae Froggatt. Unfortunately, most fruitgrowers hesitate to introduce the common hawthorn in their orchards because they fear fire blight infections which may be transmitted by this highly susceptible hawthron species. This potential hazard led us to investigate the suitability to leaf-curling aphids of alternative Crataegus species. As representative for these closely-related aphids, the species Dysaphis apiifolia petroselini (Börner) was used in the trials. Ten Crataegus species characterized by their very low susceptibility to fire blight were examined from two angles. Firstly, aphid sexuals were introduced in autumn onto the different species to verify whether egg laying could take place. Secondly, the development of fundatrices and gall formation were followed the next spring. Although eggs and mature fundatrices could be obtained on almost all species, no fundatrice-hosting galls were recorded in spring. The possible causes of these negative results with respect to the geographical origin of the particular Crataegus species involved in this work are discussed. PMID:12696414

  4. The Impact of the Hawthorne Effect in Experimental Designs in Educational Research. Final Report.

    ERIC Educational Resources Information Center

    Cook, Desmond L.

    Project objectives included (1) establishing a body of knowledge concerning the role of the Hawthorne effect in experimental designs in educational research, (2) assessing the influence of the Hawthorne effect on educational experiments conducted under varying conditions of control, (3) identifying the major components comprising the effect, and

  5. Development of an economic model to assess the cost-effectiveness of hawthorn extract as an adjunct treatment for heart failure in Australia

    PubMed Central

    Ford, Emily; Adams, Jon; Graves, Nicholas

    2012-01-01

    Objective An economic model was developed to evaluate the cost-effectiveness of hawthorn extract as an adjunctive treatment for heart failure in Australia. Methods A Markov model of chronic heart failure was developed to compare the costs and outcomes of standard treatment and standard treatment with hawthorn extract. Health states were defined by the New York Heart Association (NYHA) classification system and death. For any given cycle, patients could remain in the same NYHA class, experience an improvement or deterioration in NYHA class, be hospitalised or die. Model inputs were derived from the published medical literature, and the output was quality-adjusted life years (QALYs). Probabilistic sensitivity analysis was conducted. The expected value of perfect information (EVPI) and the expected value of partial perfect information (EVPPI) were conducted to establish the value of further research and the ideal target for such research. Results Hawthorn extract increased costs by $1866.78 and resulted in a gain of 0.02 QALYs. The incremental cost-effectiveness ratio was $85?160.33 per QALY. The cost-effectiveness acceptability curve indicated that at a threshold of $40?000 the new treatment had a 0.29 probability of being cost-effective. The average incremental net monetary benefit (NMB) was ?$1791.64, the average NMB for the standard treatment was $92?067.49, and for hawthorn extract $90?275.84. Additional research is potentially cost-effective if research is not proposed to cost more than $325 million. Utilities form the most important target parameter group for further research. Conclusions Hawthorn extract is not currently considered to be cost-effective in as an adjunctive treatment for heart failure in Australia. Further research in the area of utilities is warranted. PMID:22942231

  6. The 2011 Hawthorne, Nevada, Earthquake Sequence; Shallow Normal Faulting

    NASA Astrophysics Data System (ADS)

    Smith, K. D.; Johnson, C.; Davies, J. A.; Agbaje, T.; Knezevic Antonijevic, S.; Kent, G.

    2011-12-01

    An energetic sequence of shallow earthquakes that began in early March 2011 in western Nevada, near the community of Hawthorne, has slowly decreased in intensity through mid-2011. To date about 1300 reviewed earthquake locations have been compiled; we have computed moment tensors for the larger earthquakes and have developed a set of high-precision locations for all reviewed events. The sequence to date has included over 50 earthquakes ML 3 and larger with the largest at Mw 4.6. Three 6-channel portable stations configured with broadband sensors and accelerometers were installed by April 20. Data from the portable instruments is telemetered through NSL's microwave backbone to Reno where it is integrated with regional network data for real-time notifications, ShakeMaps, and routine event analysis. The data is provided in real-time to NEIC, CISN and the IRIS DMC. The sequence is located in a remote area about 15-20 km southwest of Hawthorne in the footwall block of the Wassuk Range fault system. An initial concern was that the sequence might be associated with volcanic processes due to the proximity of late Quaternary volcanic flows; there have been no volcanic signatures observed in near source seismograms. An additional concern, as the sequence has proceeded, was a clear progression eastward toward the Wassuk Range front fault. The east dipping range bounding fault is capable of M 7+ events, and poses a significant hazard to the community of Hawthorne and local military facilities. The Hawthorne Army Depot is an ordinance storage facility and the nation's storage site for surplus mercury. The sequence is within what has been termed the 'Mina Deflection' of the Central Walker Lane Belt. Faulting along the Whiskey Flat section of the Wassuk front fault would be primarily down-to-the-east, with an E-W extension direction; moment tensors for the 2011 earthquake show a range of extension directions from E-W to NW-SE, suggesting a possible dextral component to the Wassuk Range front fault at this latitude. At least two faults have been imaged within the sequence; these structures are at shallow depth (3-6 km), strike NE, and dip ~NW. Prior to temporary station installation event depths were poorly constrained, with the nearest network station 25 km from the source area. Early sequence moment tensor solutions show depths are on the order of 2-6 km and locations using the near source stations also confirm the shallow depths of the Hawthorne sequence. S-P times of 0.5 sec and less have been observed on a near-source station, illustrating extremely shallow source depths for some events. Along with the 2011 Hawthorne activity, very shallow depths in Nevada have been observed from near source stations in the 2008 west Reno earthquake sequence (primarily strike-slip faulting; main shock Mw 5.0) and the 1993 Rock Valley sequence in southern NNSS (strike-slip faulting; main shock Mw 4.0). These shallow sequences tend to include high rates of low magnitude earthquakes continuing over several months duration.

  7. The Hawthorne experiments and the introduction of Jean Piaget in American industrial psychology, 1929-1932.

    PubMed

    Hsueh, Yeh

    2002-05-01

    The Hawthorne interview program between 1929 and 1932 was one of the most significant industrial studies in the United States. The Hawthorne researchers applied Jean Piaget's clinical method in their extensive interviews with tens of thousands of workers. Chiefly responsible for the program's methodology was Elton Mayo, an Australian who saw interviewing as a means to promote social cooperation. Previous discussions of the Hawthorne experiments have ignored the influence of Piaget in the social sciences. This article provides an account of Mayo's and the Hawthorne researchers' efforts to fuse Piaget's innovation with burgeoning American industrial psychology. The endeavor was not an isolated event but rather drew on the theories and practice of Janet-Piaget psychology, on the support of the Laura Spelman Rockefeller Memorial Foundation, and on the discourse among social scientists about Piaget's work. PMID:12096759

  8. Miocene Coralline algae

    SciTech Connect

    Bosence, D.W.J.

    1988-01-01

    The coralline algae (Order Corallinales) were sedimentologically and ecologically important during the Miocene, a period when they were particularly abundant. The many poorly described and illustrated species and the lack of quantitative data in coralline thalli make specific determinations particularly difficult, but some species are well known and widespread in the Tethyan area. The sedimentologic importance of the Miocene coralline algae is reflected in the abundance of in-situ coralline buildups, rhodoliths, and coralline debris facies at Malta and Spain; similar sequences are known throughout the Tethyan Miocene. In-situ buildups vary from leafy crustose biostromes to walled reefs with dense coralline crusts and branches. Growth forms are apparently related to hydraulic energy. Rhodoliths vary from leafy, crustose, and open-branched forms in muddy sediments to dense, crustose, and radial-branching forms in coarse grainstones. Rhodolith form and internal structure correlate closely with hydraulic energy. Coralline genera are conservative and, as such, are useful in paleoenvironmental analysis. Of particular interest are the restricted depth ranges of recent coralline genera. More research is needed on the sedimentology, paleoecology, and systematics of the Cenozoic corallines, as they have particular value in paleoenvironmental analysis.

  9. Reticulate evolution in North American black-fruited hawthorns (Crataegus section Douglasia; Rosaceae): evidence from nuclear ITS2 and plastid sequences

    PubMed Central

    Zarrei, M.; Stefanović, S.; Dickinson, T. A.

    2014-01-01

    Background and Aims The taxonomic complexity of Crataegus (hawthorn; Rosaceae, Maleae), especially in North America, has been attributed by some to hybridization in combination with gametophytic apomixis and polyploidization, whereas others have considered the roles of hybridization and apomixis to be minimal. Study of the chemical composition and therapeutic value of hawthorn extracts requires reproducible differentiation of entities that may be difficult to distinguish by morphology alone. This study sought to address this by using the nuclear ribosomal spacer region ITS2 as a supplementary DNA barcode; however, a lack of success prompted an investigation to discover why this locus gave unsatisfactory results. Methods ITS2 was extensively cloned so as to document inter- and intraindividual variation in this locus, using hawthorns of western North America where the genus Crataegus is represented by only two widely divergent groups, the red-fruited section Coccineae and the black-fruited section Douglasia. Additional sequence data from selected loci on the plastid genome were obtained to enhance further the interpretation of the ITS2 results. Key Results In the ITS2 gene tree, ribotypes from western North American hawthorns are found in two clades. Ribotypes from diploid members of section Douglasia occur in one clade (with representatives of the east-Asian section Sanguineae). The other clade comprises those from diploid and polyploid members of section Coccineae. Both clades contribute ribotypes to polyploid Douglasia. Data from four plastid-derived intergenic spacers demonstrate the maternal parentage of these allopolyploids. Conclusions Repeated hybridization between species of section Douglasia and western North American members of section Coccineae involving the fertilization of unreduced female gametes explains the observed distribution of ribotypes and accounts for the phenetic intermediacy of many members of section Douglasia. PMID:24984714

  10. Antarctic Miocene Climate

    NASA Astrophysics Data System (ADS)

    Ashworth, A. C.; Lewis, A. R.

    2013-12-01

    Fossils from Antarctic Miocene terrestrial deposits, coupled with stratigraphic, geochemical and paleontological data from marine boreholes, provide new insights into the climatic history of the continent. During the Miocene, ice caps coalesced to form ice sheets and vegetated surfaces gave way to barren expanses. The cryospheric changes especially have global climatic implications. The fossil data consists of diatoms, pollen and spores, and macroscopic remains of plants, ostracods, insects, molluscs and a fish. Plant fossils include wood and leaves of Nothofagus (southern beech), seeds of several vascular plants, including Ranunculus (buttercup), Hippuris (mare's-tail) and Myriophyllum (watermilfoil), megaspores of Isoetes (quillwort), and moss species. The insect chitin consists of larval head capsules of Chironomidae (midges) and exoskeletal parts of Coleoptera (beetles). The molluscs include freshwater gastropods and bivalves. The majority of these taxa are likely descendants of taxa that had survived on the continent from the Paleogene or earlier. Even though early Miocene glaciations may have been large, the climate was never cold enough to cause the extinction of the biota, which probably survived in coastal refugia. Early Miocene (c. 20 Ma) macrofossils from the McMurdo Dry Valleys (77°S) support palynological interpretations from the Cape Roberts and ANDRILL marine records that the upland vegetation was a shrub tundra. Mean summer temperature (MST) in the uplands was c. 6°C and possibly higher at the coast. The climate was wet, supporting mires and lakes. By the mid-Miocene, even though the climate continued to be wet. MST was c. 4°C which was too cold to support Nothofagus and most vascular plant species. Stratigraphic evidence indicates that the time between the Early and Mid-Miocene was a time of repeated ice advances and retreats of small glaciers originating from ice caps. At c. 14 Ma there appears to have been a modal shift in climate to significantly colder and drier conditions that resulted in the extinction of the upland biota and a shift in glacial regimes from wet to cold-based. Paleontological and geochemical evidence from the deep marine record supports a major climatic event at this time. Based on pollen from the SHALDRIL cores a tundra biota survived until c. 12.8 Ma on the islands of the Antarctic Peninsula (65°S). Recently, sparse angiosperm pollen of chenopods or similar taxa, has been reported from deposits in the Prince Charles mountains (70°S) with a biostratigraphic age of Mid- to Late Miocene (12-9 Ma) making it possible that remnants of a tundra vegetation continued to exist on the edges of the continent after it had become extinct on the islands of the Antarctic Peninsula. Evidence for Pliocene warmth in the Ross Sea from thick diatomite sequence in ANDRILL cores is so far unsupported by terrestrial paleontological evidence. Pliocene wood-like structures reported from a DVDP core are interpreted as the remains of in situ shrubs but the evidence is unconvincing. Pliocene warmth in the Ross sea region, unaccompanied by an unambiguous terrestrial response can be explained in one of two ways: 1. Pliocene MSTs remained below the 3-4°C threshold needed to support shrub or herb tundra, or 2. Pliocene MSTs were warm enough but terrestrial taxa were unavailable because of extinction. Research supported by NSF 0739693,0947821.

  11. Review of Miocene larger foraminifera

    SciTech Connect

    Glenn, E.C.

    1988-01-01

    Miocene larger foraminifera were generally restricted to shallow (<100m), warm, clear, normal marine environments and were primarily dependent on brief drifting of juveniles and rafting on vegetation for dispersal. These factors are reflected in both regional and local occurrences. Regional occurrences of Miocene larger foraminifera vary with bio-province and time. Three main foraminiferal provinces (Central American, Mediterranean, and Indo-West Pacific) developed through a combination of tectonics, eustasy, climate, and faunal evolution and migration. Important effects of Miocene tectonics included widening of the Atlantic, early Miocene occlusion of the western neo-Tethys, and northern movement of the Australian plate into the tropics. Changes in climate primarily expanded or constricted latitudinal provincial boundaries. Eustatic sea level variations caused by the destruction of the late Miocene Mediterranean fauna. Globally, Miocene faunas underwent a progressive loss of taxa. This is particularly noticeable in post-early Miocene faunas of the Mediterranean and Central American provinces. Although post-early Miocene taxa evolved in all three areas, faunal migration was prevented by environmental barriers. For a given time and province, the occurrence of larger foraminifera in well-preserved Miocene reef facies is related to paleoenvironmental factors of water depth, turbidity, water energy, and substrate and to post-mortem processes of transport and selective test destruction. Environmentally related changes in test morphology, together with the relative abundances of planktonic species and small benthic taxa, allow an estimation of the magnitude of the various environmental factors, even without detailed foraminiferal taxonomy.

  12. Identification of host fruit volatiles from domestic apple (Malus domestica), native black hawthorn (Crataegus douglasii) and introduced ornamental hawthorn (C. monogyna) attractive to R. pomonella flies from the western U.S.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The apple maggot fly, Rhagoletis pomonella, infests apple (Malus domestica) and hawthorn species (most notably the downy hawthorn, Crataegus mollis) in the eastern USA. Evidence suggests that the fly was introduced into the western USA sometime in the last 60 years. In addition to apple, R. pomonel...

  13. Apatite (U-Th)/He Thermochronometry as an innovative Geothermal Exploration Tool - A case study from the Wassuk Range, Hawthorne, Nevada

    NASA Astrophysics Data System (ADS)

    Gorynski, K. E.; Stockli, D. F.; Walker, J. D.

    2010-12-01

    A utility-grade geothermal system requires increased, near-surface temperatures (>120°C), water to transfer heat, and structural or sedimentological fluid conduits. In extensional tectonic settings, geothermal anomalies often occur in areas with recent, high strain accumulation and complex faulting (i.e., cross-faults, accommodation zones) where exhumation and uplift of footwall rocks transfer heat, via advection, to the near-surface which is further carried by water through structural fluid conduits. Apatite helium (AHe) thermochronometric footwall age mapping can be used in conjunction with these genetic occurrence models to further focus regional-scale geothermal exploration efforts to areas of probabilistic increased fracture permeability and most recent, rapid footwall exhumation. Furthermore, partially reset apatites resulting from interaction with hydrothermal fluids (>40°C) will show which areas have been hottest most recently. This case study in the Wassuk Range, Hawthrone, NV confirms the utility of AHe thermochronometry as a geothermal exploration tool. A dense grid of footwall samples were collected adjacent to the Hawthorne geothermal anomaly (>85°C BHT) located in the hanging wall of the Wassuk Range block. Our data show that the location of the present-day geothermal anomaly correlates with the location of 1) the most recent episode of rapid footwall exhumation at 3.5-4 Ma, 2) km scale accommodation zones between differentially tilted Wassuk Range blocks, and 3) an elevated Miocene geothermal gradient. Furthermore, anomalously young AHe ages (<3.5 Ma) mimic the lateral extent of the Hawthorne geothermal anomaly and likely resulted from interaction with a deep-seated geothermal cell or hot hydrothermal fluids.

  14. Intentional use of the Hawthorne effect to improve oral hygiene compliance in orthodontic patients.

    PubMed

    Feil, Philip H; Grauer, Jennifer Sherah; Gadbury-Amyot, Cynthia C; Kula, Katherine; McCunniff, Michael D

    2002-10-01

    The purpose of this study was to evaluate whether the home care of noncompliant adolescent orthodontic patients with "poor" oral hygiene could be improved through the use of a deception strategy designed to intentionally induce the Hawthorne effect. This effect is often cited as being responsible for oral health improvements of control groups that receive placebo treatments. It is thought that participating in and fulfilling the requirements of a study alters subjects' behavior, thereby contributing to the improvement. Forty patients with histories of poor oral hygiene were assigned, in a quasi-random fashion, to two groups. Experimental subjects (n = 20) were presented with a situation that simulated participation in an experiment. These included the use of a consent form; distribution of tubes of toothpaste labeled "experimental"; instructions to brush twice a day for two minutes using a timer; and a request to return unused toothpaste. Control subjects (n = 20) had no knowledge of study participation. Tooth surface area covered with plaque was used as a proxy measure of home care behavior. It was measured at baseline, three months, and six months. Mean percentages of tooth surface covered with plaque for the experimental and control groups were 71 (+/- 11.52) and 74 (+/- 11.46) at baseline; 54 (+/- 13.79) and 78 (+/- 12.18) at three months; and 52 (+/- 13.04) and 79 (+/- 10.76) at six months. No statistically significant difference (p > .05) was obtained between groups at baseline. Statistically significant differences (p < .05) were found between groups at three and six months. Significant differences (p < .05) were also found only for the experimental subjects between baseline and each of the two subsequent observation periods. The efficiency and potential effectiveness of this strategy suggest that additional research be conducted to assess oral health improvements and possible applications to the private practice setting. PMID:12449206

  15. Abundances of apple maggot, Rhagoletis pomonella, across different areas in central Washington, with special reference to black-fruited hawthorns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The apple maggot fly, Rhagoletis pomonella (Walsh), has infested native black-fruited hawthorn (mostly Crataegus douglasii Lindl.) in central Washington since at least 2003, but little is known about the fly’s ecology in hawthorns there. The main objective here was to determine adult and larval abu...

  16. Miocene Antarctic Terrestrial Realm

    NASA Astrophysics Data System (ADS)

    Ashworth, A. C.; Lewis, A.; Marchant, D. R.

    2009-12-01

    The discovery of several locations in the Transantarctic Mountains that contain macrofossils and pollen is transforming our understanding of late Cenozoic Antarctica. The most southerly location is on the Beardmore Glacier (85.1°S) about 500 km from the South Pole. The environment was an active glacial margin in which plants, insects and freshwater mollusks inhabited the sand and gravel bars and small lakes on an outwash plain. In addition to leaves and wood of dwarf Nothofagus (Southern Beech) shrubs, achenes of Ranunculus (Buttercup), in situ cushion growth forms of mosses and a vascular plant, the assemblages contains various exoskeletal parts of carabid and curculionid beetles and a cyclorrhaphan fly, the shells of freshwater bivalve and gastropod species and a fish tooth. Initially the deposits were assigned a Pliocene age (3.5 Ma) but a mid- to early Miocene age is more probable (c. 14 - 25 Ma) based on correlation of fossil pollen from the deposits with 39Ar/40Ar dated pollen assemblages from the McMurdo Dry Valleys locations. The oldest location within the Dry Valleys also involved an active ice margin but was part of a valley system that was completely deglaciated for intervals long enough for thick paleosols to develop. The Friis Hills fossil deposits of the Taylor Valley region (77.8°S) are at least 19.76 Ma based on the 39Ar/40Ar age of a volcanic ash bed. The valley floor during the non-glacial phases had poorly-drained soils and the extensive development of mossy mires. Wood and leaves of Nothofagus are abundant in lacustrine deposits. The silts of shallow fluvial channels contain abundant megaspores and spiky leaves of the aquatic lycopod Isoetes (Quillwort). Fossils of beetles are also present in these deposits. During the glacial phases, proglacial lakes were surrounded by dwarfed, deciduous Nothofagus shrubs. The youngest fossils recovered from the Dry Valleys are from the Olympus Range (77.5°S) with an age of 14.07 Ma. The environment was an alpine lake that formed behind a recessional moraine. The fossils are mostly those of freshwater organisms including numerous species of diatoms and an ostracod species in which the soft anatomy is preserved. The base of the lake is marked by a moss bed with exceptionally well-preserved stems and leaves of the extant species Drepanocladus longifolius. Pollen evidence from the Cape Roberts borehole in the Ross Sea basin suggests that tundra existed from the Oligocene to the Early Miocene. Fossil evidence from the Dry Valleys locations indicates that organisms that could not inhabit Antarctica today persisted until c. 14 Ma. At 14 Ma there was a shift in glacial regimes from wet- to cold-based, marking a profound and abrupt climatic shift. We hypothesize that this climate change from warmer and wetter to colder and drier conditions caused the extinction of the tundra biota. It seems probable that at least some of the mid-Miocene fossils are of organisms whose descendants evolved in Antarctica during the Paleogene or earlier. An important consequence of this hypothesis is that the Cenozoic climate of Antarctica was warm enough until the mid-Miocene to support vascular plants and insects. This research was funded by NSF OPP 0739693.

  17. Changes in physicochemical characteristics and free amino acids of hawthorn (Crataegus pinnatifida) fruits during maturation.

    PubMed

    Li, Wei-Qin; Hu, Qing-Ping; Xu, Jian-Guo

    2015-05-15

    In this study, changes in physicochemical characteristics associated with fruit quality and free amino acids were investigated during maturation of hawthorn fruits. Significant differences in these parameters were found during maturation. The color turned progressively from mature green to semi-red, to reach bright red; the shape changed gradually from oval to round or approached round; the size, weight, and edible part (flesh/core ratio) of hawthorns increased while the density of intact fruits did not change. The content of moisture, total soluble sugars, soluble pectin, reduced ascorbic acid, total ascorbic acid, fructose, and sucrose increased while crude protein content decreased significantly. The levels of starch, sucrose, titratable acidity, protopectin, pectin, total free amino acids, and total essential amino acids initially increased and then decreased gradually during maturation. The outcomes of this study provide additional and useful information for fresh consumption and processing as well as utilization of dropped unripe hawthorn fruits. PMID:25577050

  18. The Miocene rodents of Serbia

    NASA Astrophysics Data System (ADS)

    Markovic, Z.

    2009-04-01

    During the Miocene period a group of shallow lakes was created in depressions at the territory of present-day Serbia. This caused the present wide distribution of lacustrine sediments, which occasionally alternate with the alluvial and marsh sediments. The remains of large mammals are relatively common, while the remains of small mammals used to be known only from two localities - Mala Miliva and Sibnica. The method of sediment sieving, used during the last decade, led to discovery of 6 new localities with remains of fossil vertebrates - Sibnica 1, Vračevići, village Lazarevac, Bele Vode, Brajkovac and Tavnik. Most of the fossil material is represented by osteological and odontological remains of small mammals. The best represented group of small mammals at each of the localities was the rodents. According to the odontological material presence was proven for 35 rodent species from 6 families. MN zonation was determined according to structure of associations. The geological age of fossil-bearing sediments was determined by using the method of correlation with the sites in Europe and Turkey.

  19. Miocene reef corals: A review

    SciTech Connect

    Frost, S.H.

    1988-01-01

    Tectonic blockage in the Middle East of westward-flowing Tethys surface circulation during the latest Oligocene led to creation in the earliest Miocene of endemic Mediterranean, Western Atlantic-Caribbean, and Indo-Pacific realms. A great reduction in reef coral diversity from 60-80 Oligocene species to 25-35 early Miocene species occurred in the Western Atlantic-Caribbean and Mediterranean areas accompanied by a decrease in reef growth. A slower and less drastic change apparently occurred in the Indo-Pacific area. Early Miocene reef corals of the Western Atlantic-Caribbean comprise a transition between the cosmopolitan Oligocene fauna and its endemic mid-Miocene to modern counterpart. Although early Miocene reefs were dominated by a Porites-Montastrea assemblage, eastward flow of Pacific circulation brought with it ''exotic'' corals such as Coscinaraea and Pseudocolumnastrea. Also, many cosmopolitan genera persisted from the Oligocene. During the middle to late Miocene, most of the species still living on Holocene reefs evolved. As the Mediterranean basin became more restricted, there was a slow decline in reef corals from 20 - 25 species in the Aquitainian to less than five species in the Messinian. Eustatic lowstand led to the extinction of reef-building corals in the late Messinian. In the Indo-Pacific, Neogene evolution of reef corals was conservative. Excluding the Acroporidae and Seriatoporidae, most Holocene framework species had evolved by the middle Miocene. Interplay between regional tectonics and eustatic sea level changes led to extensive development of middle to late Miocene pinnacle reefs over the southwestern Pacific.

  20. The Effects of Using In-Class Focus Groups on Student Course Evaluations.

    ERIC Educational Resources Information Center

    Hamilton, Diane M.; Pritchard, Robert E.; Welsh, Carol N.; Potter, Gregory C.; Saccucci, Michael S.

    2002-01-01

    Student course evaluations were collected from four sections of finance course (two included focus groups). Student recommendations were implemented in all four. Students in focus group sections reported higher satisfaction with the course, perhaps due to the Hawthorne Effect. (SK)

  1. Calcareous Nannofossil Evolution Vs. Climatic Evolution In The Miocene

    NASA Astrophysics Data System (ADS)

    Raffi, I.; Backman, J.; Ciummelli, M.

    2013-12-01

    Miocene times were characterized by major changes in ocean circulation and global climate that were driven by a complex set of factors operating on tectonic, orbital and suborbital timescales (Zachos et al., 2001). This time dependent development of Miocene paleo-environmental conditions is reflected in the distribution and evolutionary patterns, often expressed in terms of biostratigraphic resolution, among the dominant sediment-forming oceanic plankton groups (Kennett & Srinivasan, 1983; Baldauf & Barron, 1990; Perch-Nielsen, 1985) including calcareous nannofossils. In the Miocene through Pleistocene interval, calcareous nannofossil evolutionary appearances or extinctions provide eight biostratigraphically useful biohorizons between 23 Ma and 14 Ma, giving an average rate of 1.5 biohorizon per million years. In the next following eight million years (14-5 Ma), the number of biohorizons are 29 (3.6 biohorizons/million years), representing well over a doubling of the rate of taxonomic evolution among open ocean calcareous nannofossils compared with that of the early half of the Miocene. This observation demonstrates that a distinct evolutionary response to climatic evolution throughout the Miocene, specifically to changing conditions in the photic zone of the middle and late Miocene oceans. This assumption is supported by the behavior of some nannofossil groups, in particular by the representatives of the genus Discoaster, a key group that gives nearly half (14 of 29) of biohorizons in the younger half of the Miocene. The Discoaster's environmental distribution and abundance may provide some information about the complex interaction between climatic evolution and biotic evolution in the plankton realm.

  2. Miocene reefs of Dominican Republic

    SciTech Connect

    Evans, C.C.

    1988-01-01

    The reefs are overlain by conglomeratic strata. The stratigraphic setting of these reefs suggests that they have developed along the stalled portions of rapidly prograding fan deltas. Thickets and layers of coral debris are found seaward and stratigraphically above the well-developed reef. The matrix sediments are exclusively fine-grained sand to mud, and the fauna are suggestive of more open shelf conditions. In thickets, branched (porites spp., Pocillopora spp.), small massive (Montastrea spp., Siderastrea spp.), and foliose or plate like (Agaricia spp.) corals are found upright in the muddy sediment. Similarities in coral species and areal proximity suggest that thickets are the source of most layers of coralline debris. The association of coral debris with graded bedding and cross-bedding suggests that coral debris has been reworked by storms. The growth of corals and development of coral reefs in the Miocene-Pliocene Yaque Group is limited only by opportunities created by the slowing of siliciclastic sedimentation. Soft, muddy, terrigenous substrates and a continuing supply of terrigenous mud exert only a limited, indirect effect on reef growth.

  3. Hawthorn leaf flavonoids alleviate nonalcoholic fatty liver disease by enhancing the adiponectin/AMPK pathway

    PubMed Central

    Li, Zhongping; Xu, Jiaoya; Zheng, Peiyong; Xing, Lianjun; Shen, Hongyi; Yang, Lili; Zhang, Li; Ji, Guang

    2015-01-01

    Hawthorn (Crataeguspinnatifida) belongs to the genus Rosaceae family of plants. The hawthorn leaf, Crataeguspinnatifida Bunge, is used for both condiment and medicinal purposes to prevent and treat metabolic dysfunctions, such as hyperlipidemia, hypertension, and cardiovascular disease in traditional Chinese medicine. However, its effects on nonalcoholic fatty liver disease (NAFLD) remain obscure. The purpose of the present study was to investigate the protective effect of hawthorn leaf flavonoids (HLF), the dominant bioactive extracts of hawthorn leaves, on high fat diet (HFD)-induced hepatic steatosis and to elucidate its underlying mechanisms. HLF supplementation significantly lowered body weight, liver weight, liver/body weight ratio, improved serum parameters and liver dysfunction and markedly decreased hepatic lipid accumulation in HFD-fed rats. In addition, HLF intervention dramatically increased circulating adiponectin levels and up-regulated the expression of adiponectin receptors, particularly adiponectin receptor 2 (AdipoR2) in the liver. Moreover, adenosine monophosphate (AMP)-activated protein kinase (AMPK) was also activated, as well as AMPK-mediated alteration of sterol regulatory element binding protein-1c (SREBP-1c), peroxisome proliferator-activated receptor ? (PPAR?) and their downstream targets. Taken together, our data suggest that HLF ameliorates hepatic steatosis by enhancing the adiponectin/AMPK pathway in the liver of HFD-induced NAFLD rats. PMID:26770322

  4. Gall production on hawthorns caused by Gymnosporangium spp.in Hatay province, Turkey

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three hawthorn and related rust diseases caused by Gymnosporangium confusum on Crataegus monogyna, G. clavariiforme on C. orientalis, and G. sabinae on Pyrus communis were detected in Hatay province, Turkey. Gymnosporangium confusum was also found causing telial galls on Juniperus communis. Gymnospo...

  5. Singing and Companionship in the Hawthorn University of the Third-Age Choir, Australia

    ERIC Educational Resources Information Center

    Joseph, Dawn; Southcott, Jane

    2015-01-01

    The international University of the Third Age (U3A) embodies the principles of lifelong learning and personal fulfilment amongst members. The research reported in this article focused on the Choir of the U3A Hawthorn, Melbourne, Australia and the benefits perceived by members undertaking this active music engagement in non-competitive choral…

  6. The Repressive Nature of the Past: Hawthorne's "House of the Seven Gables."

    ERIC Educational Resources Information Center

    Loges, Max L.

    "The House of the Seven Gables" describes the problems that emerge when a family allows itself to become so locked into the traditions and sins of the past that each new generation becomes a slightly degenerated facsimile of the previous generation. Nathaniel Hawthorne manages this task by comparing Clifford, a descendent of a long line of

  7. The investigation of some bioactive compounds and antioxidant properties of hawthorn (Crataegus monogyna subsp. monogyna Jacq)

    PubMed Central

    Keser, Serhat; Celik, Sait; Turkoglu, Semra; Yilmaz, Ökkes; Turkoglu, Ismail

    2014-01-01

    Aim: The antioxidant and pharmacological effects of hawthorn have mainly been attributed to the polyphenolic contents. The aim of this research is to determine some bioactive compounds and antioxidant properties of hawthorn aqueous and ethanol extracts of leaves, flowers, and ripened fruits. Materials and Methods: For this purpose, antioxidant activities of extracts were assessed on DPPH•, ABTS•+, superoxide scavenging, reducing power and ferrous metal chelating activity assays and phenolic content of extracts was determined by Folin—Cioacalteu’s reagent. Results: The flavonoids including rutin, apigenin, myricetin, quercetin, naringenin and kaempferol, were identified by high-performance liquid chromatography in the hawthorn extract. Conclusion: It was observed the aqueous and ethanol extracts of Crataegus monogyna subsp. monogyna fruits showed the highest activity in reducing power and metal chelating activity assays. In addition, it was determined that the aqueous flower extract showed higher flavonoid content than aqueous leaves extract. The antioxidant and pharmacological effects of hawthorn have mainly been attributed to the polyphenolic contents. PMID:26401347

  8. An overview of Miocene reefs

    SciTech Connect

    Jordan, C.F. Jr. ); Colgan, M.W. ); Frost, S.H. ); Glenn, E.C. ); Bosence, D. ); Esteban, M. )

    1990-05-01

    Miocene reefs lived approximately within the latitudes of 27{degree}S to 48{degree}N compared with 25{degree}S and 32{degree}N for Holocene reefs. This expansion of reef-growing environments was the result of warm Miocene climates, aided by a eustatic sea level rise and tectonic styles that provided numerous foundations for reef development. The majority of Miocene reefs are found in three main areas: (1) Southeast Asia and the western Pacific, (2) the Mediterranean-Middle East, and (3) Middle America and the Caribbean. These regions, with their distinctive suites of coral and foramineral species, formed three biological provinces; respectively, they are the Indo-Pacific, Tethyan, and Western Atlantic provinces. Miocene reefs in Southeast Asia occur in several foreland basins as patch reef complexes on paleohighs and as barrier reefs in back-arc basins. Those reefs in the Mediterranean occur as fringing reefs, middle-shelf patch reefs, or as barrier reefs on the edges of tectonic blocks associated with Alpine thrust belts. Most reefs in the Caribbean grew on isolated open-ocean highs of volcanic origin. Miocene reefs display a diversity of framework types: (1) coral-encrusting, red algal boundstones with diverse coral faunas, (2) branching coral-encrusting, red algal boundstones with a limited Poritid fauna, (3) encrusting red algal boundstones. Barrier reef systems are especially rich in encrusting red algae and robust corals; grainstones are common as interbedded sediment. Patch reef complexes, however, display muddy carbonate textures, may have less diverse coral faunas, and commonly have larger foraminifera. The global distribution of Miocene reefs is important because (1) it provides insight into a paleoclimatic view of the earth during a major greenhouse stage and (2) Miocene buildups, such as the Arun (EUR of 14 tcf) and Bima fields (EUR of about 100 MMBO), are exploration targets.

  9. A macroecological glance at the structure of late Miocene rodent assemblages from Southwest Europe

    NASA Astrophysics Data System (ADS)

    Cano, Ana Rosa Gmez; Cantalapiedra, Juan L.; lvarez-Sierra, M. ngeles; Fernndez, Manuel Hernndez

    2014-10-01

    Deep-time perspectives in macroecology are essential with regard to understanding the impact of climate forcing on faunal communities. Using late Miocene rodent faunas (12 to 5 Ma) from two different biogeographical provinces from southwestern Europe, we asked whether the waxing and waning of faunas with dissimilar ecological affinities tracked climate in different ways. The latest middle Miocene featured a fauna dominated by dormice with forest and mixed-habitat affinities. This group declined towards the Upper Miocene. Rodent taxa with the highest values of richness at the beginning of the Upper Miocene are generalists in the southern province and specialists of forested habitats in the northern province. Finally, we identified a third, increasingly significant group of rodents linked to open landscapes towards the end of the Miocene. These three broad ecological groups showed differential responses to a complex set of interconnected circumstances, including the biogeographic structure of the study area and climatic changes throughout time.

  10. A macroecological glance at the structure of late Miocene rodent assemblages from Southwest Europe

    PubMed Central

    Cano, Ana Rosa Gómez; Cantalapiedra, Juan L.; Álvarez-Sierra, M. Ángeles; Fernández, Manuel Hernández

    2014-01-01

    Deep-time perspectives in macroecology are essential with regard to understanding the impact of climate forcing on faunal communities. Using late Miocene rodent faunas (12 to 5 Ma) from two different biogeographical provinces from southwestern Europe, we asked whether the waxing and waning of faunas with dissimilar ecological affinities tracked climate in different ways. The latest middle Miocene featured a fauna dominated by dormice with forest and mixed-habitat affinities. This group declined towards the Upper Miocene. Rodent taxa with the highest values of richness at the beginning of the Upper Miocene are generalists in the southern province and specialists of forested habitats in the northern province. Finally, we identified a third, increasingly significant group of rodents linked to open landscapes towards the end of the Miocene. These three broad ecological groups showed differential responses to a complex set of interconnected circumstances, including the biogeographic structure of the study area and climatic changes throughout time. PMID:25297009

  11. Ammonium carbonate is more attractive than apple and hawthorn fruit volatile lures to Rhagoletis pomonella (Diptera: Tephritidae) in Washington State.

    PubMed

    Yee, Wee L; Nash, Meralee J; Goughnour, Robert B; Cha, Dong H; Linn, Charles E; Feder, Jeffrey L

    2014-08-01

    The apple maggot fly, Rhagoletis pomonella (Walsh), is an introduced, quarantine pest of apple (Malus domestica Borkhausen) in the Pacific Northwest of the United States. In the eastern United States where the fly is native, fruit volatiles have been reported to be more attractive than ammonia compounds to R. pomonella. However, the opposite may be true in the western United States. Here, we determined whether newly identified western apple and western hawthorn fruit volatiles are more attractive than ammonium carbonate (AC) to R. pomonella in apple, black hawthorn, and ornamental hawthorn trees in western Washington State. In all three host trees, sticky red sphere or yellow panel traps baited with AC generally caught more flies than traps baited with lures containing the four newly developed fruit blends (modified eastern apple, western apple, western ornamental hawthorn, and western black hawthorn) or two older blends (eastern apple and eastern downy hawthorn). Fruit volatiles also displayed more variation among trapping studies conducted at different sites, in different host trees, and across years than AC. The results imply that traps baited with AC represent the best approach to monitoring R. pomonella in Washington State. PMID:24915519

  12. Diagenesis of the Oligocene-Miocene rocks of the Upper Floridan and Intermediate aquifer systems by meteoric and mixing-zone waters in southwest Florida

    SciTech Connect

    Weedman, S.D. ); McCartan, L. )

    1993-03-01

    Optical and SEM of samples from 6 cores of Oligocene and Miocene rocks that compose portions of the Florida and Intermediate aquifers and the intervening semiconfining unit documents meteoric and mixing-zone (seawater and fresh carbonate ground water) diagenesis inferred to have occurred over several cycles of sea level change. Dolomite, limestone, sandstone, and claystone of the Suwannee Formation and the Arcadia Formation (Hawthorn Group) were examined. Core samples from time-equivalent strata in two E--W transects in Manatee, Hardee, Highlands, Sarasota, and DeSoto Counties are estimated to be 16--33 Ma on the basis of [sup 87]Sr/[sup 86]Sr ratios from unaltered mollusk shells and by molluscan biostratigraphy. Lithostratigraphic correlations are based on examination of 19 cores, 62 thin sections, 60 geophysical logs, and mineralogy determined by X-ray diffraction. Diagenetic indicators that the authors tracked petrographically include shell micritization, shell dissolution, equant and (or) fibrous CaCO[sub 3] cement, neomorphism, dolomite, etched phosphate grains, echinoderm fragment syntaxial overgrowths, and amorphous silica pore lining. Infiltration of meteoric water caused dissolution of carbonate minerals, especially aragonite, and precipitation of equant calcite crystals in voids of dissolved fossils and in pore spaces between grains. The silica was precipitated as pore linings in zones having soil textures. Observed replacement of calcite by limpid dolomite is consistent with modeling predictions of mixing-zone diagenesis. Etched crystals of limpid dolomite may indicate freshwater dissolution of a mixing-zone precipitate. Mapping of regional unconformities revealed pronounced thickening and thinning of some units. Evidence of meteoric water diagenesis is observed in the upper 600 ft of the transects examined. Evidence of mixing-zone diagenesis is observed at varying depths, but appears to increase in abundance and thickness toward the west.

  13. B. F. Skinner and T. N. Whitehead: A Brief Encounter, Research Similarities, Hawthorne Revisited, What Next?

    PubMed Central

    Claus, Calvin K

    2007-01-01

    B. F. Skinner and T. N. Whitehead recalled a personal interaction in 1934, with differing memories of the event. No evidence of other subsequent interactions or mutual citations has been found. Although they went their separate ways, three similarities in their research strategies have been found and are discussed. Elements of Whitehead's Hawthorne study and Skinner's concurrent, parallel work reveal that they both (a) introduced the cumulative curve to report data, (b) used a small number of subjects studied over time, and (c) used highly accurate recording devices. A few “afterwords” are offered on their lives and writings, and again, on the Hawthorne effect. A suggestion is made that a Skinner–Whitehead research approach might be useful in studying gambling behavior. PMID:22478490

  14. Effect of a hawthorn extract on contraction and energy turnover of isolated rat cardiomyocytes.

    PubMed

    Ppping, S; Rose, H; Ionescu, I; Fischer, Y; Kammermeier, H

    1995-11-01

    The hawthorn extract LI 132 (crataegus), prepared from leaves and flowers, and standardised to 2.2% flavonoids, was investigated with respect to its effect on (1) the contraction, (2) the energy-turnover and (3) the apparent refractory period (t(ref)) of isolated cardiac myocytes from adult rats. (1) The contractile behaviour of attached myocytes was analyzed by an image processing system. (2) The energy turnover was calculated from the decrease in oxygen content in the myocyte suspension, brought about by cellular respiration. It was differentiated between energy turnover related to cell shortening and that required for ionic transport processes by application of the contraction-inhibiting agent 2,3-butanedione monoxime. (3) The apparent refractory period (t(ref)) was evaluated by pacing the myocytes with increasing stimulation rates and determining the frequency at which failure of single contractions occurred. For these purposes, the myocytes were incubated in a stimulation chamber, which is part of a computer-assisted system allowing to simultaneously evaluate the mechanics and energetics of electrically induced contraction. Within a range of 30-180 microg/ml, the hawthorn extract exhibited a positive inotropic effect on the contraction amplitude accompanied by a moderate increase of energy turnover both for mechanical and ionic processes. In comparison with other positive inotropic interventions, such as application of the beta-adrenergic agonist isoprenaline, or of the cardiac glycoside ouabain (g-strophantin), or elevation of the extracellular Ca++-concentration, the effects of the hawthorn extract were significantly more economical with respect to the energetics of the myocytes. Furthermore the extract prolonged the apparent refractory period in the presence and the absence of isoprenaline, which be indicative for an antiarrhythmic potential. PMID:8929230

  15. Preliminary plan for the development of geothermal energy in the town of Hawthorne, Nevada

    NASA Astrophysics Data System (ADS)

    1981-11-01

    Site characteristics pertinent to the geothermal development are described, including: physiography, demography, economy, and goals and objectives of the citizens as they relate to geothermal development. The geothermal reservoir is characterized on the basis of available information. The probable drilling depth to the reservoir, anticipated water production rates, water quality, and resource temperature are indicated. Uses of the energy that seem appropriate to the situation both now and in the near future at Hawthorne are described. The essential institutional requirements for geothermal energy development are discussed, including the financial, environmental, and legal and regulatory aspects. The various steps that are necessary to accomplish the construction of the geothermal district heating system are described.

  16. Preliminary plan for the development of geothermal energy in the town of Hawthorne, Nevada

    SciTech Connect

    Not Available

    1981-11-04

    Site characteristics pertinent to the geothermal development are described, including: physiography, demography, economy, and goals and objectives of the citizens as they relate to geothermal development. The geothermal reservoir is characterized on the basis of available information. The probable drilling depth to the reservoir, anticipated water production rates, water quality, and resource temperature are indicated. Uses of the energy that seem appropriate to the situation both now and in the near future at Hawthorne are described. The essential institutional requirements for geothermal energy development are discussed, including the financial, environmental, and legal and regulatory aspects. The various steps that are necessary to accomplish the construction of the geothermal district heating system are described.

  17. Miocene benthic foraminiferal isotope records: A synthesis

    USGS Publications Warehouse

    Savin, S.M.; Douglas, R.G.; Keller, G.; Killingley, J.S.; Shaughnessy, L.; Sommer, M.A.; Vincent, E.; Woodruff, F.

    1981-01-01

    18O 16O and 13C 12C ratios of Miocene benthic foraminifera from a number of Atlantic, Pacific and Indian Ocean DSDP sites (71, 77B, 206, 208, 238, 279, 289, 296, 329, 357 and 366A) have been compiled. These provide a rather detailed history of Miocene deep water especially in the Pacific Ocean. Bottom-water temperatures rose during the early Miocene and then declined rapidly during the middle Miocene. This decline was accompanied by an increase in Antarctic glaciation. Late Miocene bottom temperatures and Antarctic ice volumes are inferred to be similar to today's, but exhibited some fluctuation. The early Miocene ocean was less thermally stratified at intermediate and abyssal depths while the late Miocene deep ocean had a thermal structure generally similar to the modern ocean. Foraminiferal carbon isotope ratios at most of the sites varied quasi-sympathetically throughout the Miocene. These variations must reflect comparable variations in the mean 13C 12C of marine HCO3-. However, the causes of such variations are not yet clear. ?? 1981.

  18. Miocene reefs in western Mediterranean

    SciTech Connect

    Esteban, M.

    1988-01-01

    Coral reefs were particularly abundant and well developed during the late Tortonian and Messinian in southeastern Spain, the Balearic Islands, Italy, Sicily, Algeria, and Morocco. These reefs occurred just before and during the deposition of the thick Messinian evaporite units in the basinal areas and disappeared completely from Mediteranean during the early Pliocene. Most of the coral reefs are fringing terrigenous coastal fan complexes with very small lagoons and show progradation of less than 2 km. Some of the reefs occur on, or are intercalated with, Neogene volcanics or Messinian evaporites. Barrier-reef complexes are less common, have extensive lagoons behind them, and show complex progradational geometries more than 10 km wide. Excellent outcrops allow detailed reconstruction of paleogeography and sea level changes. Progradation predominated during phases of relative sea level drops and stillsands, while significant retrogradation occurred during sea level rises. The coral reef wall framework is commonly less than 20 m thick and is dominated by Porites and, locally, Tarbellastrae. Older Miocene reefs are less well developed, but show greater diversity of corals and reef organisms. Younger Miocene reef complexes occurring in open ocean settings are formed by only one branching coral genus (Porites or, locally, Tarbellastraea) with branching colonies up to 7 m high. Halimeda sands are particularly abundant in the upper reef slopes with occasional intercalations of red algae pavements that most likely coincide with episodes of terrigenous influx.

  19. Preliminary plan for the development of geothermal energy in the town of Hawthorne, Nevada

    SciTech Connect

    Not Available

    1981-11-04

    The results of the analyses as well as a plan for the development of the geothermal resource are described. Site characteristics pertinent to the geothermal development are described. These characteristics include physiography, demography, economy, and goals and ojectives of the citizens as they would relate to geothermal development. The geothermal resource is described. The reservoir is characterized on the basis of available information. The probable drilling depth to the reservoir, anticipated water production rates, water quality, and resource temperatures ae indicated. Uses of the energy that seem appropriate to the situation both now and in the near future at Hawthorne are described. The amounts and types of energy currently consumed by end users are estimated. Using this data base, conceptual engineering designs and cost estimates for three alternative district heating systems are presented. In addition, the results of a life cycle cost analysis for these alternatives are discussed. The essential institutional requirements for geothermal energy development, including the financial, environmental, and legal and regulatory aspects are discussed. The various steps that are necessary to accomplish the construction of the geothermal district heating system at Hawthorne are described. A time-line chart shows the tasks, the time estimated to be required for each, and the interrelationships among the activities.

  20. Transcript assembly and quantification by RNA-Seq reveals differentially expressed genes between soft-endocarp and hard-endocarp hawthorns.

    PubMed

    Dai, Hongyan; Han, Guofen; Yan, Yujiao; Zhang, Feng; Liu, Zhongchi; Li, Xiaoming; Li, Wenran; Ma, Yue; Li, He; Liu, Yuexue; Zhang, Zhihong

    2013-01-01

    Hawthorn (Crataegus spp.) is an important pome with a long history as a fruit, an ornamental, and a source of medicine. Fruits of hawthorn are marked by hard stony endocarps, but a hawthorn germplasm with soft and thin endocarp was found in Liaoning province of China. To elucidate the molecular mechanism underlying the soft endocarp of hawthorn, we conducted a de novo assembly of the fruit transcriptome of Crataegus pinnatifida and compared gene expression profiles between the soft-endocarp and the hard-endocarp hawthorn varieties. De novo assembly yielded 52,673 putative unigenes, 20.4% of which are longer than 1,000 bp. Among the high-quality unique sequences, 35,979 (68.3%) had at least one significant match to an existing gene model. A total of 1,218 genes, represented 2.31% total putative unigenes, were differentially expressed between the soft-endocarp hawthorn and the hard-endocarp hawthorn. Among these differentially expressed genes, a number of lignin biosynthetic pathway genes were down-regulated while almost all the flavonoid biosynthetic pathway genes were strongly up-regulated, concomitant with the formation of soft endocarp. In addition, we have identified some MYB and NAC transcription factors that could potentially control lignin and flavonoid biosynthesis. The altered expression levels of the genes encoding lignin biosynthetic enzymes, MYB and NAC transcription factors were confirmed by quantitative RT-PCR. This is the first transcriptome analysis of Crataegus genus. The high quality ESTs generated in this study will aid future gene cloning from hawthorn. Our study provides important insights into the molecular mechanisms underlying soft endocarp formation in hawthorn. PMID:24039819

  1. Transcript Assembly and Quantification by RNA-Seq Reveals Differentially Expressed Genes between Soft-Endocarp and Hard-Endocarp Hawthorns

    PubMed Central

    Zhang, Feng; Liu, Zhongchi; Li, Xiaoming; Li, Wenran; Ma, Yue; Li, He; Liu, Yuexue; Zhang, Zhihong

    2013-01-01

    Hawthorn (Crataegus spp.) is an important pome with a long history as a fruit, an ornamental, and a source of medicine. Fruits of hawthorn are marked by hard stony endocarps, but a hawthorn germplasm with soft and thin endocarp was found in Liaoning province of China. To elucidate the molecular mechanism underlying the soft endocarp of hawthorn, we conducted a de novo assembly of the fruit transcriptome of Crataegus pinnatifida and compared gene expression profiles between the soft-endocarp and the hard-endocarp hawthorn varieties. De novo assembly yielded 52,673 putative unigenes, 20.4% of which are longer than 1,000 bp. Among the high-quality unique sequences, 35,979 (68.3%) had at least one significant match to an existing gene model. A total of 1,218 genes, represented 2.31% total putative unigenes, were differentially expressed between the soft-endocarp hawthorn and the hard-endocarp hawthorn. Among these differentially expressed genes, a number of lignin biosynthetic pathway genes were down-regulated while almost all the flavonoid biosynthetic pathway genes were strongly up-regulated, concomitant with the formation of soft endocarp. In addition, we have identified some MYB and NAC transcription factors that could potentially control lignin and flavonoid biosynthesis. The altered expression levels of the genes encoding lignin biosynthetic enzymes, MYB and NAC transcription factors were confirmed by quantitative RT-PCR. This is the first transcriptome analysis of Crataegus genus. The high quality ESTs generated in this study will aid future gene cloning from hawthorn. Our study provides important insights into the molecular mechanisms underlying soft endocarp formation in hawthorn. PMID:24039819

  2. Phenolic contents and cellular antioxidant activity of Chinese hawthorn "Crataegus pinnatifida".

    PubMed

    Wen, Lingrong; Guo, Xingbo; Liu, Rui Hai; You, Lijun; Abbasi, Arshad Mehmood; Fu, Xiong

    2015-11-01

    It is evident from various epidemiological studies that consumption of fruits and vegetables is essential to maintain health and in the disease prevention. Present study was designed to examine phenolic contents and antioxidant properties of three varieties of Crataegus pinnatifida (Chinese hawthorn). Shanlihong variety exhibited elevated levels of total phenolics and flavonoid contents, including free and bond phenolics. Procyanidin B2 was most abundant phenolic compound in all samples, followed by epicatechin, chlorogenic acid, hyperoside, and isoquercitrin. The free ORAC values, and free hydro-PSC values were 398.3-555.8 ?mol TE/g DW, and 299.1-370.9 ?mol VCE/g DW, respectively. Moreover, the free cellular antioxidant activity (CAA) values were 678-1200 ?mol of QE/100 g DW in the no PBS wash protocol, and 345.9-532.9 ?mol of QE/100 g DW in the PBS wash protocol. C. pinnatifida fruit could be valuable to promote consumer health. PMID:25976791

  3. A preliminary plan for the development of geothermal energy in the town of Hawthorne, Nevada

    NASA Astrophysics Data System (ADS)

    1981-11-01

    The development of the geothermal resource were analyzed. Site characteristics pertinent to the geothermal development are described. The probable drilling depth to the reservoir, anticipated water production rates, water quality, and resource temperatures are indicated. Uses of the energy appropriate to the situation are described. The amounts and types of energy currently consumed by end users are estimated. Conceptual engineering designs and cost estimates for three alternative district heating systems are presented. The results of a life cycle cost analysis for these alternatives are discussed. The essential institutional requirements for geothermal energy development, including the financial, environmental, and legal and regulatory aspects are discussed. The various steps necessary to accomplish the construction of the geothermal district heating system at Hawthorne are described.

  4. Panafrican distribution of Lower Miocene Hominoidea

    NASA Astrophysics Data System (ADS)

    Senut, Brigitte; Pickford, Martin; Wessels, Dudley

    1997-11-01

    Palaeontological survey of the Neogene littoral deposits of the Namaqualand coastal strip, Northern Cape Province, South Africa, has resulted in the collection of the first Lower Miocene faunas from South Africa. Among the mammals from Ryskop and Hondeklip Bay is a gorilla-sized hominoid. This discovery greatly increases the geographic range of early Miocene hominoids and suggests that even at this remote epoch, the superfamily had a Panafrican distribution.

  5. Phytochemical characterization of several hawthorn (Crataegus spp.) species sampled from the Eastern Mediterranean region of Turkey

    PubMed Central

    ali?kan, O?uzhan; Gndz, Kazim; Sere, Sedat; Toplu, Celil; Kamilo?lu, nder; ?engl, Memnune; Erci?li, Sezai

    2012-01-01

    Background: We evaluated the total phenolic content, antioxidant capacity as well as antioxidant activity of five Crataegus species (A1, A2, Y1, Y2, Y4 accessions of Crataegus aronia var. aronia; B2, B3, B5, B6, B7, B9, Y5 accessions of C. aronia var. dentata; B10 accession of C. aronia var. minuta; Y3 accession of Crataegus orientalis var. orientalis and A3 accession of Crataegus monogyna subsp. azarella). Materials and Methods: Antioxidant activity and total phenolic content of fruits were determined by ?-carotene bleaching and FolinCiocalteu assays. Antioxidant capacity was determined by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Results: C. monogyna subsp. azarella had the highest total phenol, antioxidant activity and antioxidant capacity of 55.2 mg gallic acid equivalents (GAE)/g dry weight (DW), 81.9% and 31.2%, respectively. C. aronia var. aronia was found to have the lowest total phenolic content (35.7 mg GAE/g DW). The antioxidant activities of fruit extracts increased in the order of C. orientalis var. orientalis < C. aronia var. minuta < C. aronia var. dentata < C. aronia var. aronia < C. monogyna subsp. azarella according to ?-carotene/linoleic acid assay. In recent years, C. aronia var. dentata has gained importance as a commercial species in this region. B3 and B7 accessions had fruit weight more than 14 g, and considerable total phenol content, antioxidant activity and antioxidant capacity. Conclusion: This investigation shows the potential value of hawthorn fruit species as a good source of natural antioxidants and that consumption of hawthorn fruit or its products may contribute substantial amounts of antioxidants to the diet. PMID:22438658

  6. Updated chronology for the Miocene hominoid radiation in Western Eurasia

    PubMed Central

    Casanovas-Vilar, Isaac; Alba, David M.; Garcs, Miguel; Robles, Josep M.; Moy-Sol, Salvador

    2011-01-01

    Extant apes (Primates: Hominoidea) are the relics of a group that was much more diverse in the past. They originated in Africa around the Oligocene/Miocene boundary, but by the beginning of the Middle Miocene they expanded their range into Eurasia, where they experienced a far-reaching evolutionary radiation. A Eurasian origin of the great ape and human clade (Hominidae) has been favored by several authors, but the assessment of this hypothesis has been hampered by the lack of accurate datings for many Western Eurasian hominoids. Here we provide an updated chronology that incorporates recently discovered Iberian taxa and further reevaluates the age of many previously known sites on the basis of local biostratigraphic scales and magnetostratigraphic data. Our results show that identifiable Eurasian kenyapithecins (Griphopithecus and Kenyapithecus) are much younger than previously thought (ca. 14 Ma instead of 16 Ma), which casts serious doubts on the attribution of the hominoid tooth from Engelswies (16.316.5 Ma) to cf. Griphopithecus. This evidence is further consistent with an alternative scenario, according to which the Eurasian pongines and African hominines might have independently evolved in their respective continents from similar kenyapithecin ancestors, resulting from an early Middle Miocene intercontinental range extension followed by vicariance. This hypothesis, which would imply an independent origin of orthogrady in pongines and hominines, deserves further testing by accurately inferring the phylogenetic position of European dryopithecins, which might be stem pongines rather than stem hominines. PMID:21436034

  7. Allopolyploidy, diversification, and the Miocene grassland expansion

    PubMed Central

    Estep, Matt C.; McKain, Michael R.; Vela Diaz, Dilys; Zhong, Jinshun; Hodge, John G.; Hodkinson, Trevor R.; Layton, Daniel J.; Malcomber, Simon T.; Pasquet, Rémy; Kellogg, Elizabeth A.

    2014-01-01

    The role of polyploidy, particularly allopolyploidy, in plant diversification is a subject of debate. Whole-genome duplications precede the origins of many major clades (e.g., angiosperms, Brassicaceae, Poaceae), suggesting that polyploidy drives diversification. However, theoretical arguments and empirical studies suggest that polyploid lineages may actually have lower speciation rates and higher extinction rates than diploid lineages. We focus here on the grass tribe Andropogoneae, an economically and ecologically important group of C4 species with a high frequency of polyploids. A phylogeny was constructed for ca. 10% of the species of the clade, based on sequences of four concatenated low-copy nuclear loci. Genetic allopolyploidy was documented using the characteristic pattern of double-labeled gene trees. At least 32% of the species sampled are the result of genetic allopolyploidy and result from 28 distinct tetraploidy events plus an additional six hexaploidy events. This number is a minimum, and the actual frequency could be considerably higher. The parental genomes of most Andropogoneae polyploids diverged in the Late Miocene coincident with the expansion of the major C4 grasslands that dominate the earth today. The well-documented whole-genome duplication in Zea mays ssp. mays occurred after the divergence of Zea and Sorghum. We find no evidence that polyploidization is followed by an increase in net diversification rate; nonetheless, allopolyploidy itself is a major mode of speciation. PMID:25288748

  8. Allopolyploidy, diversification, and the Miocene grassland expansion.

    PubMed

    Estep, Matt C; McKain, Michael R; Vela Diaz, Dilys; Zhong, Jinshun; Hodge, John G; Hodkinson, Trevor R; Layton, Daniel J; Malcomber, Simon T; Pasquet, Rémy; Kellogg, Elizabeth A

    2014-10-21

    The role of polyploidy, particularly allopolyploidy, in plant diversification is a subject of debate. Whole-genome duplications precede the origins of many major clades (e.g., angiosperms, Brassicaceae, Poaceae), suggesting that polyploidy drives diversification. However, theoretical arguments and empirical studies suggest that polyploid lineages may actually have lower speciation rates and higher extinction rates than diploid lineages. We focus here on the grass tribe Andropogoneae, an economically and ecologically important group of C4 species with a high frequency of polyploids. A phylogeny was constructed for ca. 10% of the species of the clade, based on sequences of four concatenated low-copy nuclear loci. Genetic allopolyploidy was documented using the characteristic pattern of double-labeled gene trees. At least 32% of the species sampled are the result of genetic allopolyploidy and result from 28 distinct tetraploidy events plus an additional six hexaploidy events. This number is a minimum, and the actual frequency could be considerably higher. The parental genomes of most Andropogoneae polyploids diverged in the Late Miocene coincident with the expansion of the major C4 grasslands that dominate the earth today. The well-documented whole-genome duplication in Zea mays ssp. mays occurred after the divergence of Zea and Sorghum. We find no evidence that polyploidization is followed by an increase in net diversification rate; nonetheless, allopolyploidy itself is a major mode of speciation. PMID:25288748

  9. The late early Miocene Sabine River

    SciTech Connect

    Manning, E. )

    1990-09-01

    Work on a new late early Miocene vertebrate fossil site, in a paleochannel deposit of the upper Carnahan Bayou Member of the lower Fleming Formation, has revealed unexpected data on the course and nature of the Sabine River of that time. Screen washing for smaller vertebrate remains at the site, just west of the Sabine River in Newton County, central eastern Texas, has resulted in the recovery of early Permian, Early Cretaceous, Late Cretaceous (Maestrichtian), Paleocene/Eocene, late Eocene, and Oligocene/Miocene fossils, in addition to the main early Miocene fauna. The reworked fossils, as well as distinctive mineral grains, show that the late early Miocene Sabine River was connected to the Texas/Oklahoma/Arkansas boundary section of the Red River, as well as to rivers draining the southern Ouachita Mountains. These rivers must have joined the Texas/Louisiana boundary section of the Sabine River somewhere in northwest Louisiana at that time. This suggests that the Louisiana section of the present Red River pirated the Texas/Oklahoma/Arkansas boundary section of the river some time after the early Miocene. The preservation of recognizable fossils transported hundreds of miles in a large river itself requires explanation. It is speculated here that the late early Miocene Sabine River incorporated a large amount of the then recently deposited volcanic ash from the Trans-Pecos Volcanic Field. Montmorillonite clay from the altered volcanic ash would have made the river very turbid, which could have allowed coarse sand-sized particles to be carried in the suspended load of the river, rather than in its bed load (where they would have been destroyed by the rolling chert gravel). Additional evidence for such long-distance fossil transport in the late early Miocene rivers of the western Gulf Coastal Plain comes from the abundant Cretaceous fossils of the upper Oakville Formation of southeast Texas and the Siphonina davisi zone of the southeast Texas subsurface.

  10. Abundance of Apple Maggot, Rhagoletis pomonella, Across Different Areas in Central Washington, with Special Reference to Black-Fruited Hawthorns

    PubMed Central

    Yee, Wee L.; Klaus, Michael W.; Cha, Dong H.; Linn, Charles E.; Goughnour, Robert B.

    2012-01-01

    The apple maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), infests non-commercial apple (Malus domestica (Borkh.) Borkh.) and native black-fruited hawthorns (mostly Crataegus douglasii Lindl.) in central Washington, but little has been published on the abundance of the fly in this region. In this paper, the abundance of R. pomonella across different sites near apple-growing areas in central Washington is documented in order to assess the threat of the fly to commercial apple orchards. The fly was first detected on traps in Klickitat, Yakima, and Kittitas Counties in 1981, 1995, and 1997, respectively. From 19812010 in Kittitas and Yakima Counties, only 0 to 4.7% of traps on apple, crabapple, and hawthorn trees were positive for flies, whereas in Klickitat County, located farther from commercial apple orchards, 0 to 41.9% of traps were positive. In 2008, in Yakima County and Goldendale in Klickitat County, 7.8% of black-fruited hawthorn trees were infested, with 0 to 0.00054 larvae per fruit. In 2010, in Kittitas and Yakima Counties and Goldendale in Klickitat County, 25.0% of C. douglasii trees were infested, with 0.00042 to 0.00248 larvae per fruit. In 2010, in a remote forested area of Klickitat County far from commercial apple orchards, 94.7% of C. douglasii trees were infested, with 0.20813 larvae per fruit. Overall results suggest R. pomonella is unlikely to develop high populations rapidly near major commercial apple-growing areas in central Washington, including in black-fruited hawthorns, increasing chances it can be kept out of commercial orchards. PMID:23451979

  11. Miocene reef carbonates of Mariana Islands

    SciTech Connect

    Siegrist, H.G. Jr.

    1988-02-01

    Miocene carbonates in the southern Mariana Islands are impressive for their lithologic diversity, thicknesses (over 250 m), and geographic extent (> 20% combined outcrop coverage over four major high islands: Guam, Rota, Tinian and Saipan). Sections are dominated either by lagoonal algal-foraminiferal wackestones and mudstones with locally abundant high-energy shelly-skeletal facies, or by rubbly to muddy, fore-reef-to-bank deposits of packstones and grainstones with highly diverse and variable biogenic clasts. Fresh to deeply weathered volcaniclastic material may comprise at least 80% of some high-energy fore-reef facies, whereas lagoonal and bank deposits usually contain less than 0.5% terrigenous material. Surprisingly, the Miocene in the Marianas lacks almost completely any reef-core facies. Several poorly developed coral-rich mounds on Saipan and localized laminated red algal buildups on Guam appear to constitute the extant reef-wall facies in the Miocene. The lack of buildups may be a matter of differential survival; it may result from headland erosion and benching associated with emergence of narrow reef tracts as has been postulated by others for south Guam. Alternatively, the authors are proposing that Miocene bathymetry and the volume of terrigenous influx militated against significant reef core formation. Radiometric age dating of these reef carbonates has proven unsuccessful because pervasive diagenesis has transformed the entire Miocene section into low-magnesium calcite with minor and occasional dolomite. Freshwater phreatic diagenesis accounts for the principal porosity variation and trace element distribution.

  12. Identification of fruit volatiles from green hawthorn (Crataegus viridis) and blueberry hawthorn (Crataegus brachyacantha) host plants attractive to different phenotypes of Rhagoletis pomonella flies in the southern United States.

    PubMed

    Cha, Dong H; Powell, Thomas H Q; Feder, Jeffrey L; Linn, Charles E

    2011-09-01

    The apple maggot fly, Rhagoletis pomonella, infests several hawthorn species in the southern USA. In a companion paper, we showed that R. pomonella flies infesting two different mayhaw species (Crataegus opaca and C. aestivalis) can discriminate between volatile blends developed for each host fruit, and that these blends are different from previously constructed blends for northern fly populations that infest domestic apple (Malus domestica), downy hawthorn (Crataegus mollis), and flowering dogwood (Cornus florida). Here, we show by using coupled gas chromatography and electroantennographic detection (GC-EAD), gas chromatography with mass spectrometry (GC-MS), and flight tunnel bioassays, that two additional southern hawthorn fly populations infesting C. viridis (green hawthorn) and C. brachyacantha (blueberry hawthorn) also can discriminate between volatile blends for each host fruit type. A 9-component blend was developed for C. viridis (3-methylbutan-1-ol [5%], butyl butanoate [19.5%], propyl hexanoate [1.5%], butyl hexanoate [24%], hexyl butanoate [24%], pentyl hexanoate [2.5%], 1-octen-3-ol [0.5%], pentyl butanoate [2.5%], and (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) [20.5%]) and an 8-component blend for C. brachyacantha (3-methylbutan-1-ol [0.6%], butyl acetate [50%], pentyl acetate [3.5%], butyl butanoate [9%], butyl hexanoate [16.8%], hexyl butanoate [16.8%], 1-octen-3-ol [0.3%], and pentyl butanoate [3%]). Crataegus viridis and C. brachyacantha-origin flies showed significantly higher levels of upwind oriented flight to their natal blend in flight tunnel assays compared to the alternate, non-natal blend and previously developed northern host plant blends. The presence of DMNT in C. viridis and butyl acetate in C. brachyacantha appeared to be largely responsible for driving the differential response. This sharp behavioral distinction underscores the diversity of odor response phenotypes in the southern USA, points to possible host race formation in these populations, and despite the presence of several apple volatiles in both blends, argues against a functional apple race existing on southern host plants prior to the introduction of apple to North America. PMID:21887525

  13. Additional material of the enigmatic Early Miocene mammal Kelba and its relationship to the order Ptolemaiida

    PubMed Central

    Cote, Susanne; Werdelin, Lars; Seiffert, Erik R.; Barry, John C.

    2007-01-01

    Kelba quadeemae, a fossil mammal from the Early Miocene of East Africa, was originally named on the basis of three isolated upper molars. Kelba has previously been interpreted as a creodont, a pantolestid, an insectivoran, and a hemigaline viverrid. The true affinities of this taxon have remained unclear because of the limited material and its unique morphology relative to other Miocene African mammals. New material of Kelba from several East African Miocene localities, most notably a skull from the Early Miocene locality of Songhor in Western Kenya, permits analysis of the affinities of Kelba and documents the lower dentition of this taxon. Morphological comparison of this new material clearly demonstrates that Kelba is a member of the order Ptolemaiida, a poorly understood group whose fossil record was previously restricted to the Oligocene Fayum deposits of northern Egypt. Phylogenetic analysis supports the monophyly of the Ptolemaiida, including Kelba, and recovers two monophyletic clades within the order. We provide new family names for these groups and an emended diagnosis for the order. The discovery of ptolemaiidans from the Miocene of East Africa is significant because it extends the known temporal range of the order by >10 million years and the geographic range by >3,200 km. Although the higher-level affinities of the Ptolemaiida remain obscure, their unique morphology and distribution through a larger area of Africa (and exclusively Africa) lend support to the idea that Ptolemaiida may have an ancient African origin. PMID:17372202

  14. Shark-bitten vertebrate coprolites from the Miocene of Maryland

    NASA Astrophysics Data System (ADS)

    Godfrey, Stephen J.; Smith, Joshua B.

    2010-05-01

    Coprolites (fossilized feces) preserve a wide range of biogenic components, from bacteria and spores to a variety of vertebrate tissues. Two coprolites from the Calvert Cliffs outcrop belt (Miocene-aged Chesapeake Group), MD, USA, preserve shark tooth impressions in the form of partial dental arcades. The specimens are the first known coprolites to preserve vertebrate tooth marks. They provide another example of trace fossils providing evidence of prehistoric animal behaviors that cannot be directly approached through the study of body fossils. Shark behaviors that could account for these impressions include: (1) aborted coprophagy, (2) benthic or nektonic exploration, or (3) predation.

  15. Miocene precursors to Great Barrier Reef

    SciTech Connect

    Davies, P.J.; Symonds, P.A.; Feary, D.A.; Pigram, C.

    1988-01-01

    Huge reefs of Miocene age are present in the Gulf of Papua north of the present-day Great Barrier Reef and to the east on the Marion and Queensland Plateaus. In the Gulf of Papua, Miocene barrier reefs formed the northern forerunner of the Great Barrier Reef, extending for many hundreds of kilometers along the eastern and northern margin of the Australian craton within a developing foreland basin. Barrier reefs, slope pinnacle reefs, and platform reefs are seen in seismic sections and drill holes. Leeside talus deposits testify to the high energy impinging on the eastern margin of these Miocene reefs. The Queensland Plateau is a marginal plateau east of the central Great Barrier Reef and separated from it by a rift trough. Miocene reefs occupied an area of about 50,000 km/sup 2/ and grew on salt-controlled highs on the western margin of the plateau and on a regional basement high extending from the platform interior to its southern margin. Reef growth has continued to the present day, although two major contractions in the area covered by reefs occurred during the Miocene. The Marion Plateau is present directly east of the Great Barrier Reef and during the Micoene formed a 30,000-km/sup 2/ platform with barrier reefs along its northern margin and huge platform reefs and laggons on the platform interior. These reefs grew on a flat peneplained surface, the whole area forming a large shallow epicontinental sea. In all three areas, the middle Miocene formed the acme of reef expansion in the region.

  16. Miocene reef carbonates of Mariana Islands

    SciTech Connect

    Siegrist, H.G. Jr.

    1988-01-01

    Miocene carbonates in the southern Mariana Islands are impressive for their lithologic diversity, thicknesses (over 250 m), and geographic extend (>20% combined outcrop coverage over four major high islands: Guam, Rota, Tinian and Saipan). Sections are dominated either by lagoonal algal-foraminiferal wackestones and mudstones with locally abundant high-energy shelly-skeletal facies, or by rubbly to muddy, fore-reef-to-bank deposits of packstones and grainstones with highly diverse and variable biogenic clasts. Fresh to deeply weathered volcaniclastic material may comprise at least 80% of some high-energy fore-reef facies, whereas lagoonal and bank deposits usually contain less than 0.5% terrigenous material. Surprisingly, the Miocene in the Marianas lacks almost completely any reef-core facies. Several poorly developed coral-rich mounds on Saipan and localized laminated red algal buildups on Guam appear to constitute the extant reef-wall facies in the Miocene. The lack of buildups may be a matter of differential survival; it may result from headland erosion and benching associated with emergency of narrow reef tracts as has been postulated by others for south Guam. Radiometric age dating of these reef carbonates has proven unsuccessful because pervasive diagenesis has transformed the entire Miocene section into low-magnesium calcite with minor and occasional dolomite. Freshwater phreatic diagenesis accounts for the principal porosity variation and trace element distribution.

  17. Scale-dependent effects of habitat fragmentation on hawthorn pollination, frugivory, and seed predation.

    PubMed

    Garca, Daniel; Chacoff, Natacha P

    2007-04-01

    Habitat fragmentation is a major cause of functional disruption in plant-animal interactions. The net effect on plant regeneration is, however, controversial because a given landscape change can simultaneously hamper mutualism and attenuate antagonism. Furthermore, fragmentation effects may emerge at different spatial scales, depending on the size of the foraging range of the different interacting animals. We studied pollination by insects, frugivory by birds acting as seed dispersers, and postdispersal seed predation by rodents in 60 individual hawthorn (Crataegus monogyna Jacq.) trees in relation to structural fragmentation in the surrounding habitat. We evaluated fragmentation at three spatial scales by measuring the percentage of forest cover in three concentric areas around each tree of, respectively, 10-m, 20- to 50-m, and 50- to 100-m radius. The number of developing pollen tubes per flower style and fruit set decreased in proportion to the decrease of forest cover. Similarly, the magnitude of frugivory in focal trees was negatively affected by habitat loss. In contrast, seed predation was higher under plants in highly fragmented contexts. The effect of fragmentation was additive in terms of reducing the potential of plant regeneration. Moreover, the functional scale of response to habitat loss differed among interactions. Fragmentation effects on pollination emerged at the largest scale, whereas seed predation was mostly affected at the intermediate scale. In contrast to expectations from the larger foraging range of birds, fragmentation effects on frugivory mainly operated at the finest scale, favored by the ability of birds to cope hierarchically with spatial heterogeneity at different scales. Given that two opposing demographic forces (frugivory and seed predation) would be potentially affected by fine-scale features, we propose structural scale as the primary spatial dimension of fragmentation effects on the process of plant regeneration. PMID:17391190

  18. Effect of Temperature on Demographic Parameters of the Hawthorn Red Midget Moth, Phyllonorycter corylifoliella, on Apple

    PubMed Central

    Amiri, Abbas; Talebi, Ali Asghar; Zamani, Abbas Ali; Kamali, Karim

    2010-01-01

    The hawthorn red midget moth, Phyllonorycter corylifoliella (Hübner) (Lepidoptera: Gracillariidae), is one of the most serious pests of apple and pear orchards in Iran, however little is known about its biology and relationship with environmental factors. The reproduction and population growth parameters of P. corylifoliella were examined at six constant temperatures (15, 20, 25, 30, 33 and 35° C) on apple var. golden delicious. At 35° C, P. corylifoliella failed to develop beyond the first instar. The lowest (13%) and highest (64%) mortality rates of immature stages occurred at 25 and 33° C, respectively. The life expectancies (ex) decreased with increasing of age and the life expectancies of one-day-old larvae were estimated to be 38.68, 33.34, 35.11, 26.28 and 16.11 days at 15, 20, 25, 30 and 33° C, respectively. The highest intrinsic rate of natural increase (rm), net reproductive rate (Ro) and finite rate of increase (λ) at 25° C were 0.100 ± 0.003, 47.66 ± 5.47 and 1.11 ± 0.00, respectively. The mean generation time (T) decreased with increasing temperatures from 86.86 ± 0.53 days at 15° C to 33.48 ± 0.16 days at 30° C. Doubling time (DT) varied significantly with temperature and the shortest doubling time was obtained at 25° C. The results of this study provide direction for future research on evaluating the performance of P. corylifoliella and the efficiency of its natural enemies in apple orchards under variable environmental conditions. PMID:20883137

  19. Miocene Soil Database: Global paleosol and climate maps of the Middle Miocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Metzger, C. A.

    2013-12-01

    Paleosols, which record past climatic, biologic, and atmospheric conditions, can be used as a proxy to understand ancient terrestrial landscapes, paleoclimate, and paleoenvironment. In addition, the middle Miocene thermal maximum (~16 Ma) provides an ancient analog for understanding the effects of current and future climate change on soil and ecosystem regimes, as it contains records of shifts similar in magnitude to expected global climate change. The Miocene Soil Database (MSDB) combines new paleosol data from Australia and Argentina with existing and previously uncollated paleosol data from the literature and the Paleobiology Database. These data (n = 507) were then used to derive a paleogeographic map of climatically significant soil types zones during the Middle Miocene. The location of each diagnostic paleosol type (Aridisol, Alfisol, Mollisol, Histosol, Oxisol, and Ultisol) was plotted and compared with the extent of these soil types in the modern environment. The middle Miocene soil map highlights the extension of tropical soils (Oxisols, Ultisols), accompanied by thermophilic flora and fauna, into northern and southern mid-latitudes. Peats, lignites, and Histosols of wetlands were also more abundant at higher latitudes, especially in the northern hemisphere, during the middle Miocene. The paleosol changes reflect that the Middle Miocene was a peak of global soil productivity and carbon sequestration, with replacement of unproductive Aridisols and Gelisols with more productive Oxisols, Alfisols, Mollisols and Histosols. With expansion to include additional data such as soil texture, moisture, or vegetation type, the MSDB has the potential to provide an important dataset for computer models of Miocene climate shifts as well as future land use considerations of soils in times of global change.

  20. "The most important technique ": Carl Rogers, Hawthorne, and the rise and fall of nondirective interviewing in sociology.

    PubMed

    Lee, Raymond M

    2011-01-01

    In the 1940s, interviewing practice in sociology became decisively influenced by techniques that had originally been developed by researchers in other disciplines working within a number of therapeutic or quasi-therapeutic contexts, in particular the "nondirective interviewing" methods developed by Carl Rogers and the interviewing procedures developed during the Hawthorne studies. This article discusses the development of nondirective interviewing and looks at how in the 1930s and '40s the approach came to be used in sociology. It examines the factors leading to both the popularity of the method and its subsequent fall from favor. PMID:21462193

  1. Longitudinal Variation in Terrestrial Oxygen Isotope Records of Modern Water and Mid-Miocene Authigenic Minerals: No Mid-Miocene Climatic Optimum in the Inland Pacific Northwest?

    NASA Astrophysics Data System (ADS)

    Takeuchi, A.; Larson, P. B.; Suzuki, K.; Goodwin, A. J.

    2005-12-01

    The stable isotopic compositions of benthic foraminifera quantitatively indicate that the middle Miocene climatic optimum was a period of global greenhouse conditions within the generally cooling and drying climatic trend in the past 65 million years. There are numerous red-colored weathering sequences preserved in intervolcanic paleosurfaces of the middle Miocene Columbia River Basalt Group. Even though most of the reddened layers were considered as thermally altered `baked' zones by the overlying basalt flows, many of them show much evidence of pedogenesis. Thus, it was suggested that these lateritic weathering horizons are products of intense chemical weathering under humid and temperate paleoclimate conditions in the inland Pacific Northwest during the middle Miocene climatic optimum. However, these weathering sequences are only common around the Blue Mountains region in southeastern Washington, Oregon, and Idaho, where modern mean annual precipitation is relatively higher than the surrounding basins. Therefore, we hypothesize that the observed intense chemical weathering is the result of higher mean annual precipitation due to the orographic effect in the Blue Mountains area. The orographic effect is associated with higher altitude than surroundings in an upwind region. Four mid-Miocene spectacular thick reddish paleosols on top of Columbia River basalt flows were found at nearly the same latitude of 46°N but with different longitudes, ranging from 116°W to 120°W. Authigenic minerals at depths greater than 50 cm below the overlying basaltic flows were collected at each location, and also, for comparison, several surface water samples were collected to determine the modern hydrologic isotopic conditions along the transect. The measured δ18O values of modern surface water show a negative shift of approximately 5‰ from west to east in the study area, and the observed negative shift within the δ18O authigenic mineral values is similar (~4.5‰). Using equilibrium fractionation equations, the estimated paleo-temperatures are also similar to the modern temperatures along the transect. Thus, the regional climate has not been changes significantly since the mid-Miocene. It is likely that topography of the study area in the Blue Mountains region has not been significantly changed either since at least late Miocene. The basalt stratigraphy also indicates that there was a tectonic uplift in the Blue Mountains area during the mid- to late-Miocene.

  2. El Nino-like events during Miocene

    SciTech Connect

    Casey, R.E.; Nelson, C.O.; Weinheimer, A.L.; Oeth, P.A.; Swanson, R.J.

    1988-03-01

    El Nino-like events have been recorded from the Miocene laminated siliceous facies of the Monterey Formation. These El Nino-like Miocene events are compared to El Nino events recorded from Holocene varved sediments deposited within the anoxic Santa Barbara basin. Strong El Nino events can be recognized from Holocene Santa Barbara basin sediments by increases in radiolarian flux to the sea floor during those events. For the last 100-plus years, frequency of strong El Ninos has been on the order of one extremely strong event about every 100 years, and one easily recognizable event about every 18 years. Frequencies in the laminated (varved) Miocene range from about every 4-5 years to over 20 years. The higher frequencies occur within generally warm intervals and the lower frequencies within generally cold intervals. Perhaps the frequencies of these events may, in fact, be an important indicator in determining whether the intervals were cold or warm. Reconstructions of the paleo-California Current system during El Nino-like periods have been made for the west coast from the Gulf of California to northern California. Strong El Nino-like events occurred 5.5 and 8 Ma, and a strong anti-El Nino-like event occurred at about 6.5 Ma. Evidence from the 5.5 and 8 Ma events combined with other evidence suggests that modern El Ninos, similar to today's, were initiated at 5.5 Ma or earlier.

  3. A unique Middle Miocene European hominoid and the origins of the great ape and human clade

    PubMed Central

    Moyà-Solà, Salvador; Alba, David M.; Almécija, Sergio; Casanovas-Vilar, Isaac; Köhler, Meike; De Esteban-Trivigno, Soledad; Robles, Josep M.; Galindo, Jordi; Fortuny, Josep

    2009-01-01

    The great ape and human clade (Primates: Hominidae) currently includes orangutans, gorillas, chimpanzees, bonobos, and humans. When, where, and from which taxon hominids evolved are among the most exciting questions yet to be resolved. Within the Afropithecidae, the Kenyapithecinae (Kenyapithecini + Equatorini) have been proposed as the sister taxon of hominids, but thus far the fragmentary and scarce Middle Miocene fossil record has hampered testing this hypothesis. Here we describe a male partial face with mandible of a previously undescribed fossil hominid, Anoiapithecus brevirostris gen. et sp. nov., from the Middle Miocene (11.9 Ma) of Spain, which enables testing this hypothesis. Morphological and geometric morphometrics analyses of this material show a unique facial pattern for hominoids. This taxon combines autapomorphic features—such as a strongly reduced facial prognathism—with kenyapithecine (more specifically, kenyapithecin) and hominid synapomorphies. This combination supports a sister-group relationship between kenyapithecins (Griphopithecus + Kenyapithecus) and hominids. The presence of both groups in Eurasia during the Middle Miocene and the retention in kenyapithecins of a primitive hominoid postcranial body plan support a Eurasian origin of the Hominidae. Alternatively, the two extant hominid clades (Homininae and Ponginae) might have independently evolved in Africa and Eurasia from an ancestral, Middle Miocene stock, so that the supposed crown-hominid synapomorphies might be homoplastic. PMID:19487676

  4. Paleomagnetism of the Miocene Columbia River Basalt Group in Oregon and Washington from the Pacific Coast to the Columbia Plateau: Magnetostratigraphy, Vertical-Axis Rotations, Paleosecular Variation, and Remagnetization

    NASA Astrophysics Data System (ADS)

    Hagstrum, J. T.; Wells, R. E.; Evarts, R. C.; Niem, A. R.; Sawlan, M. G.; Blakely, R. J.

    2008-12-01

    Identification of individual flows within the Columbia River Basalt Group (CRBG) has mostly relied on minor differences in geochemistry, but magnetic polarity has also proved useful in differentiating flows and establishing a temporal framework. Within the thick, rapidly erupted Grande Ronde Basalt four major polarity chrons (R1 to N2) have been identified. Because cooling times of CRBG flows are brief compared to rates of paleosecular variation (PSV), within-flow paleomagnetic directions are expected to be constant across the extensive east-west reaches of these flows. Vertical-axis rotations in OR and WA, driven by northward-oblique subduction of the Juan de Fuca plate, thus can be measured by comparing directions for western sampling localities to directions for the same flow units on the relatively stable Columbia Plateau. Clockwise rotations calculated for outcrop locations within the Coast Range (CR) block are uniformly about 30° (N=102 sites). East of the northwest-trending en échelon Mt. Angel-Gales Creek, Portland Hills, and northern unnamed fault zones, as well as north of the CR block's northern boundary (~Columbia River), clockwise rotations abruptly drop to about 15° (N=39 sites), with offsets in these bounding fault zones corresponding to the Portland and Willamette pull-apart basins. The general agreement of vertical- axis rotation rates estimated from CRBG magnetizations with those determined from modern GPS velocities indicates a relatively steady rate over the last 10 to 15 Myr. Unusual directions due to PSV, field excursions, or polarity transitions could provide useful stratigraphic markers. Individual flow directions, however, have not been routinely used to identify flows. One reason this has been difficult is that remagnetization is prevalent, particularly in the Coast Ranges, coupled with earlier demagnetization techniques that did not completely remove overprint components. Except for the Ginkgo and Pomona flows of the Wanapum and Saddle Mountains Basalts, reference Plateau directions for the CRBG are poorly known. Moreover, field and drill- core relations indicate that flows with different chemistries were erupted at the same time. Renewed sampling, therefore, has been undertaken eastward from the Portland area into the Columbia River Gorge and out onto the Plateau. Resampling of the Patrick Grade section (23 flows) in southeastern WA has shown that overprint magnetizations were not successfully removed in many flows at this locality in an earlier study [1]. This brings into question blanket demagnetization studies of the CRBG as well as polarity measurements routinely made in the field with hand-held fluxgate magnetometers. [1] Choiniere and Swanson, 1979, Am. J. Sci., 279, p. 755

  5. Miocene Paleotopography of the European Central Alps

    NASA Astrophysics Data System (ADS)

    Campani, M.; Mulch, A.; Kempf, O.; Schlunegger, F.; Mancktelow, N.

    2012-12-01

    Reconstructing surface elevation, surface uplift, and relief histories is fundamental to understanding the growth of mountain ranges, to explore their topographic limits, and relate these to the interplay between geodynamic and Earth surface processes. Here, we aim to quantify Miocene elevation of the Central European Alps through stable isotope paleoaltimetry. The novelty of our approach, which renders our analysis less sensitive to past climate change, is that stable isotope proxies of identical age are analyzed from both the high internal parts of the Alpine orogen and the adjacent foreland basin. Whereas the foreland basin was at or near sea level and tracks the combined effects of upstream changes in rainfall amount and composition, stable isotopes in precipitation at the high Alpine site additionally record the effect of elevation. We contrast hydrogen isotope ratios (?D) in mica and chlorite that interacted with meteoric water along the Simplon detachment, a major normal fault that developed near the Miocene Alpine drainage divide, with oxygen isotope ratios (?18O) from carbonate-bearing paleosols of the North-Alpine foreland basin. ?D values of muscovite (-126) and chlorite (-135) from the brittle hanging wall and of recrystallized muscovite (-108) and biotite (-140) from adjacent footwall mylonites provide unequivocal evidence for localized syntectonic meteoric water interaction along the Simplon detachment. Detailed 40Ar/39Ar and fission track geochronology constrains the timing of isotopic exchange to ca. 14.5 Ma, when the footwall mylonites passed through the ductile-to-brittle transition. Age-equivalent oxygen isotope ratios within pedogenic carbonate from North-Alpine foreland paleosols that developed near Miocene sea level serve as our low-elevation point of reference. ?18O values in these paleosols, dated with ca. 100 ka precision, vary between +19 and +25 (SMOW) with average values of +20 at ca. 14.5 Ma. Using the relative differences between meteoric water compositions in the foreland basin and the high Alpine Simplon detachment, our isotope data are consistent with a mid-Miocene minimum average elevation difference of 2350 (+700/-500) m for the Simplon region. Our results indicate that Miocene Central Alpine elevations were at least comparable to those of today at a time when rapid exhumation characterized the internal regions of the Alpine orogen. This implies that the bulk of Alpine topography was built during the construction stage of the Alpine orogenic wedge when accretion rates outpaced erosion and sediment evacuation rates.

  6. Interpretation of a 3D Seismic-Reflection Volume in the Basin and Range, Hawthorne, Nevada

    NASA Astrophysics Data System (ADS)

    Louie, J. N.; Kell, A. M.; Pullammanappallil, S.; Oldow, J. S.; Sabin, A.; Lazaro, M.

    2009-12-01

    A collaborative effort by the Great Basin Center for Geothermal Energy at the University of Nevada, Reno, and Optim Inc. of Reno has interpreted a 3d seismic data set recorded by the U.S. Navy Geothermal Programs Office (GPO) at the Hawthorne Army Depot, Nevada. The 3d survey incorporated about 20 NNW-striking lines covering an area of approximately 3 by 10 km. The survey covered an alluvial area below the eastern flank of the Wassuk Range. In the reflection volume the most prominent events are interpreted to be the base of Quaternary alluvium, the Quaternary Wassuk Range-front normal fault zone, and sequences of intercalated Tertiary volcanic flows and sediments. Such a data set is rare in the Basin and Range. Our interpretation reveals structural and stratigraphic details that form a basis for rapid development of the geothermal-energy resources underlying the Depot. We interpret a map of the time-elevation of the Wassuk Range fault and its associated splays and basin-ward step faults. The range-front fault is the deepest, and its isochron map provides essentially a map of "economic basement" under the prospect area. There are three faults that are the most readily picked through vertical sections. The fault reflections show an uncertainty in the time-depth that we can interpret for them of 50 to 200 ms, due to the over-migrated appearance of the processing contractors prestack time-migrated data set. Proper assessment of velocities for mitigating the migration artifacts through prestack depth migration is not possible from this data set alone, as the offsets are not long enough for sufficiently deep velocity tomography. The three faults we interpreted appear as gradients in potential-field maps. In addition, the southern boundary of a major Tertiary graben may be seen within the volume as the northward termination of the strong reflections from older Tertiary volcanics. Using a transparent volume view across the survey gives a view of the volcanics in full, providing a clear picture of prominent structures. Potential drill targets and areas of development are defined within the data volume by the intersections of the fault surfaces with the tracked, strong stratigraphic reflections. Target volumes for drilling and development are defined by the intersections of the faults and bright-spot stratigraphy, and their uncertainty bounds. There are a few such intersections present within the 3d volume. Analyzing seismic attributes gives the opportunity to identify characteristics common in geothermal environments.

  7. Miocene mass-transport sediments, Troodos Massif, Cyprus

    USGS Publications Warehouse

    Lord, A.R.; Harrison, R.W.; BouDagher-Fadel, M.; Stone, B.D.; Varol, O.

    2009-01-01

    Sediment mass-transport layers of submarine origin on the northern and southern flanks of the Troodos ophiolitic massif are dated biostratigraphically as early Miocene and late Miocene, respectively and therefore represent different seismogenic events in the uplift and erosional history of the Troodos terrane. Analysis of such events has potential for documenting Miocene seismic and uplift events regionally in the context of changing stress field directions and plate vectors through time. ?? 2009 The Geologists' Association.

  8. Miocene mollusks from the Simojovel area in Chiapas, southwestern Mexico

    NASA Astrophysics Data System (ADS)

    del Carmen Perrilliat, María; Vega, Francisco J.; Coutiño, Marco A.

    2010-11-01

    The fauna of gastropods and bivalves from the amber-bearing lithostratigraphic units of the Simojovel area, Chiapas is reported, including the description of two new species and one subspecies: Turbinella maya new species, Melongena corona tzeltal new subspecies and Agladrillia ( Eumetadrillia) vermeiji new species. Stratigraphic affinities of the previously described species suggest an Early Miocene age for the Mazantic Shale, and a Middle Miocene age for the overlying Balumtum Sandstone. One specimen of gastropod, with a relatively large piece of amber attached to the adapertural part of the shell is representative for an Early Miocene age and estuarine paleoenvironmental interpretation for the Mazantic Shale. Mollusca, Miocene, Chiapas, Amber, Mexico.

  9. Miocene mammal reveals a Mesozoic ghost lineage on insular New Zealand, southwest Pacific

    PubMed Central

    Worthy, Trevor H.; Tennyson, Alan J. D.; Archer, Michael; Musser, Anne M.; Hand, Suzanne J.; Jones, Craig; Douglas, Barry J.; McNamara, James A.; Beck, Robin M. D.

    2006-01-01

    New Zealand (NZ) has long been upheld as the archetypical example of a land where the biota evolved without nonvolant terrestrial mammals. Their absence before human arrival is mysterious, because NZ was still attached to East Antarctica in the Early Cretaceous when a variety of terrestrial mammals occupied the adjacent Australian portion of Gondwana. Here we report discovery of a nonvolant mammal from Miocene (1916 Ma) sediments of the Manuherikia Group near St Bathans (SB) in Central Otago, South Island, NZ. A partial relatively plesiomorphic femur and two autapomorphically specialized partial mandibles represent at least one mouse-sized mammal of unknown relationships. The material implies the existence of one or more ghost lineages, at least one of which (based on the relatively plesiomorphic partial femur) spanned the Middle Miocene to at least the Early Cretaceous, probably before the time of divergence of marsupials and placentals >125 Ma. Its presence in NZ in the Middle Miocene and apparent absence from Australia and other adjacent landmasses at this time appear to reflect a Gondwanan vicariant event and imply persistence of emergent land during the Oligocene marine transgression of NZ. Nonvolant terrestrial mammals disappeared from NZ some time since the Middle Miocene, possibly because of late Neogene climatic cooling. PMID:17159151

  10. Miocene paleotopography of the Central Alps

    NASA Astrophysics Data System (ADS)

    Campani, M.; Mulch, A.; Kempf, O.; Schlunegger, F.; Mancktelow, N.

    2012-07-01

    Reconstructing surface elevation, surface uplift, and relief histories is fundamental to understanding the growth of mountain ranges, to explore their topographic limits, and relate these to the interplay between geodynamic and Earth surface processes. Here, we aim to quantify Miocene paleoelevation of the Central European Alps through stable isotope paleoaltimetry. The novelty of our approach, which renders our analysis less sensitive to past climate change, is that stable isotope proxies of identical age are analyzed from both the high internal parts of the Alpine orogen and the adjacent foreland basin. Whereas the foreland basin was at or near sea level and traces the combined effects of upstream changes in rainfall amount and composition, the high Alpine site additionally records the effect of elevation on stable isotopes in precipitation. We compare hydrogen isotopic ratios (?D) in mica and chlorite that interacted with meteoric water along the Simplon detachment, a major normal fault that developed at high elevations, with meteoric water compositions deduced from carbonate-bearing paleosols of the North-Alpine foreland basin. ?D values of muscovite (-126) and chlorite (-135) from the brittle hanging wall and of recrystallized muscovite (-108) and biotite (-140) from adjacent footwall mylonites provide unequivocal evidence for localized syntectonic meteoric water interaction along the Simplon detachment. Detailed 40Ar/39Ar and fission track geochronology constrains the timing of isotopic exchange to ca. 14.5 Ma, when the footwall mylonites passed through the ductile to brittle transition. Age-equivalent oxygen isotope ratios (?18O) measured within pedogenic carbonate from North-Alpine foreland paleosols that developed near Miocene sea level serve as our low-elevation point of reference. ?18O values in these paleosols, dated with ca. 100 ka precision, vary between +19 and +25 (SMOW) with average values of +20 at ca. 14.5 Ma. Using the relative differences between meteoric water compositions in the foreland basin and the high Alpine Simplon detachment, our isotope data are consistent with a mid-Miocene minimum average elevation difference of 2350 (+700/-500) m for the Simplon region. Our results indicate that Miocene Alpine elevations were at least comparable to those of today and are likely to have acted as an important barrier to Atlantic-derived moisture transport into central Europe and Eurasia since that time.

  11. Isotope geochemistry of the Miocene and Quaternary carbonate rocks in Rabigh area, Red Sea coast, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Dawood, Yehia H.; Aref, Mahmoud A.; Mandurah, Mohammed H.; Hakami, Ahmed; Gameil, Mohammed

    2013-11-01

    The Rabigh area, a coastal region north of Jeddah city, Saudi Arabia contains raised Quaternary coral reefal terraces and reworked coral fragments mixed with sand and gravel. This area has a thin exposure Lower Miocene shallow marine carbonate rocks that laterally pass into evaporites. The Miocene carbonate and evaporite rocks conformably overly the Lower Miocene siliciclastic sequence, are in turn capped by the Harrat basaltic boulders. The Miocene carbonates are made up of dolomitic packstone, wackestone and mudstone, whereas the overlying Quaternary reefal terraces are composed of coral boundstone and grainstones. The Quaternary reefal terraces of Rabigh area have been dated using the uranium-series dating method to obtain precise dates for these corals. The calculated ages (128, 212 and 235 ka) indicate that deposition took place during high sea level stands associated with interglacial times during Oxygen Isotope Stages (OIS) 5 and 7. The youngest age (128 ka) clearly corresponds to stage 5e of the last interglacial period. The obtained ages correlate well with those of the emerged reefs on the Sudanese and Egyptian coasts at the western side of the Red Sea. The broad distribution of wet climate, pluvial deposits on the continents and high sea level stands indicate a wide geographical range of the interglacial events of the Oxygen Isotope Stages (OIS) 5 and 7. The oxygen and carbon isotopic composition of the Miocene and Quaternary carbonate rocks in Rabigh area show a broad range of ?13C and ?18O. The Quaternary carbonate rocks have significantly higher ?13C than the Miocene ones, but low ?13C values of the Miocene samples likely indicate a high contribution of carbon from organic sources at the time of deposition. Linear trends are evident in both groups of samples supporting the likelihood of secondary alteration.

  12. Quantification of the Hawthorne effect in hand hygiene compliance monitoring using an electronic monitoring system: a retrospective cohort study

    PubMed Central

    Srigley, Jocelyn A; Furness, Colin D; Baker, G Ross; Gardam, Michael

    2014-01-01

    Background The Hawthorne effect, or behaviour change due to awareness of being observed, is assumed to inflate hand hygiene compliance rates as measured by direct observation but there are limited data to support this. Objective To determine whether the presence of hand hygiene auditors was associated with an increase in hand hygiene events as measured by a real-time location system (RTLS). Methods The RTLS recorded all uses of alcohol-based hand rub and soap for 8?months in two units in an academic acute care hospital. The RTLS also tracked the movement of hospital hand hygiene auditors. Rates of hand hygiene events per dispenser per hour as measured by the RTLS were compared for dispensers within sight of auditors and those not exposed to auditors. Results The hand hygiene event rate in dispensers visible to auditors (3.75/dispenser/h) was significantly higher than in dispensers not visible to the auditors at the same time (1.48; p=0.001) and in the same dispensers during the week prior (1.07; p<0.001). The rate increased significantly when auditors were present compared with 15?min prior to the auditors arrival (1.50; p=0.009). There were no significant changes inside patient rooms. Conclusions Hand hygiene event rates were approximately threefold higher in hallways within eyesight of an auditor compared with when no auditor was visible and the increase occurred after the auditors arrival. This is consistent with the existence of a Hawthorne effect localised to areas where the auditor is visible and calls into question the accuracy of publicly reported hospital hand hygiene compliance rates. PMID:25002555

  13. Distributional patterns of decapod crustaceans in the circum-Mediterranean area during the Oligo-Miocene

    NASA Astrophysics Data System (ADS)

    Hyžný, Matúš

    2015-04-01

    During the Oligocene and Miocene, the circum-Mediterranean area was a complex network of (mostly) shallow marine basins. Significant biogeographic differentiation of this area has been documented (Harzhauser et al. 2007), mainly during the Miocene, when connections between Proto-Mediterranean, Paratethys and Proto-Indo-West Pacific were intermittently opening and closing. These seaways allowed migration of marine faunas. Distributional patterns has so far been discussed for several different animal groups, especially for molluscs (e.g. Studencka et al. 1998; Harzhauser et al. 2002, 2003, 2007). To test these patterns with decapod crustaceans, a database has been compiled including all previously published Oligocene and Miocene decapod occurrences and newly gathered data from examined material deposited in the institutional collections. Decapod associations have been significant components of marine habitats since the Mesozoic times with ever-increasing importance throughout the Cenozoic. Müller (1979) argued that brachyuran decapods are among the best zoogeographical indicators. Although decapods were used as such indicators before (e.g. Schweitzer 2001; Feldmann & Schweitzer 2006), no detailed analysis of the circum-Mediterranean taxa has been conducted so far. Based on proposed anti-estuarine circulation pattern, decapods originated in the Proto-Mediterranean, and migrated both into the North Sea and the Paratethys. Moreover, during the Early Miocene the Rhine Graben served as a connection between the North Sea and the Paratethys which enabled faunal exchange. The Middle Miocene Proto-Mediterranean and Paratethys decapod assemblages as taken together were relatively homogeneous, although distinct due to increasing rate of endemites in the Paratethys during the Miocene. The research has been supported by FWF: Lise Meitner Program M 1544-B25. References Feldmann R.M. & Schweitzer C.E. 2006: Paleobiogeography of Southern Hemisphere decapod Crustacea. J. Paleontol. 80, 83-103. Harzhauser M., Kroh A., Mandic O., Piller W.E., Göhlich U., Reuter M. & Berning B. 2007: Biogeographic responses to geodynamics: a key study all around the Oligo-Miocene Tethyan Seaway. Zool. Anz. 246, 241-256. Harzhauser M., Mandic O. & Zuschin M. 2003: Changes in Paratethyan marine molluscs at the Early/Middle Miocene transition: diversity, palaeogeography and palaeoclimate. Acta Geol. Pol. 53, 323-339. Harzhauser M., Piller W.E. & Steininger F.F. 2002: Circum-Mediterranean Oligo/Miocene Biogeographic Evolution - the Gastropods' Point of View. Palaeogeogr., Palaeoclimatol., Palaeoecol. 183, 103-133. Müller P. 1979: The Indo-West-Pacific character of the Badenian decapod crustaceans of the Paratethys. In: VII International Congress on Mediterranean Neogene. Athens, September 27-October 2. Ann. Géol. Pays Hellén., Tome hors série 2, 865-869. Schweitzer C.E. 2001: Paleobiogeography of Cretaceous and Tertiary decapod crustaceans of the North Pacific Ocean. J. Paleontol. 75, 808-826. Studencka B., Gontsharova I.A. & Popov S.V. 1998: The bivalve faunas as a basis for reconstruction of the Middle Miocene history of the Paratethys. Acta Geol. Pol. 48, 285-342.

  14. The Miocene aquifer system in Mississippi

    USGS Publications Warehouse

    Newcome, Roy

    1975-01-01

    A large amount of information is available on the aquifers of Mississippi. Reports resulting from various areal studies have described the ground-water resources of the areas concerned, but no reports dealing specifically with the statewide occurrence of individual aquifer systems have been prepared previously. A series of "aquifer atlases" was deemed the most effective way to point out the character, the potential, and the extent of development of the aquifers and thereby provide water managers with data needed for efficient utilization of available resources. This report on the Miocene aquifer system is the first in the series. Information on the aquifers was obtained in the cooperative programs of the U.S. Geological Survey with the Mississippi Board of Water Commissioners and other State and Federal agencies.

  15. Paleotopography of the Miocene European Central Alps

    NASA Astrophysics Data System (ADS)

    Campani, M.; Mulch, A.; Kempf, O.; Schlunegger, F.; Mancktelow, N.

    2011-12-01

    Reconstructing the surface elevation, surface uplift, and relief evolution histories is fundamental to understanding the growth of mountain ranges, to explore their topographic limits, and relate these to geodynamic and Earth surface processes. Recent geologic and geodynamic models for the Central European Alps propose that the bulk of topography was built through the Pliocene, mainly based on the observation of a strong increase in sedimentation and erosion rates during the last 5-6 Ma, suggesting that the Alps never attained elevations as high as today. Here, we aim to quantify the Miocene (20-14 Ma) paleoelevation of the Central Alps through stable isotope paleoaltimetry. The novelty of the approach presented here, which renders it rather insensitive to past climate change, is to analyze stable isotope proxies of identical age, both from high internal parts of the Alpine orogen and from the adjacent foreland basin that was at or near sea level. We first exploit the hydrogen isotopic ratio in phyllosilicates (mica and chlorite) that interacted with meteoric water during activity of the Simplon detachment, a major normal fault that developed during orogen-parallel extension in high elevation regions. We then contrast the resulting meteoric water compositions with those recorded in carbonate-bearing paleosols of the North-Alpine foreland basin to provide an estimate of relative elevation differences. In the North-Alpine foreland basin, we present oxygen and carbon isotopic compositions of pedogenic mudstones and carbonate concretions. These terrestrial paleosols, dated with ca. 100 ka precision, serve as our point of reference for stable isotope paleoaltimetry, since they formed at or near sea level. Here, ?18O and ?13C values vary between +19 to +25% (SMOW) and -7 to +1% respectively and show close correspondence to global climate change during the mid-Miocene climatic optimum. In the Simplon fault zone, detachment-related muscovite (-126%) and chlorite (-135%) ?D values from the brittle hanging wall provide unequivocal evidence for syntectonic meteoric water interaction. This result is supported by a strongly localized pattern of meteoric water interaction in the footwall mylonites where recrystallized muscovite and biotite have ?D values of -108% and -140%, respectively. Detailed 40Ar/39Ar and fission track geochronology constrains the timing of isotopic exchange during the ductile to brittle transition of the detachment to ca. 14-15 Ma. Using the relative differences between meteoric water composition in the foreland and internal regions of the orogen, our isotope data are consistent with an average altitude difference of 2300 m 500 m during the mid-Miocene. Our results do not necessarily agree with the proposition that the main formation of topography started only 5-6 Ma ago, since the Alpine elevations were similar or even higher than those of today already in the mid-Miocene. This implies that the bulk of Alpine topography was built during the construction stage of the Alpine orogenic wedge when accretion rates outpaced erosion and sediment evacuation rates.

  16. A new Mammutidae (Proboscidea, Mammalia) from the Late Miocene of Gansu Province, China.

    PubMed

    Mothé, Dimila; Avilla, Leonardo S; Zhao, Desi; Xie, Guangpu; Sun, Boyang

    2016-03-01

    The "Yanghecun specimen", a proboscidean specimen represented by a mandible from Miocene of China and previously described as Gomphotheriidae, is here reviewed and described as a new genus and species of Mammutidae: Sinomammut tobieni. This taxon is a longirostrine mastodon, lacking lower tusks, and bearing a wide last molar with oblique and non-inflated lophids, broad transverse interlophids, and yoke-like wear figures. Phylogenetic analysis of Mammutidae based on dental and mandibular features recovered S. tobieni as sister group of the mastodon Mammut. The longirostrine condition and the well-developed lower incisors seem to be primitive for Mammutidae, while the brevirostry is the derived condition, probably emerged during the middle Miocene (12-11 Mya). However, two derived conditions are recognized to the lower tusks: the absence of lower tusks (S. tobieni) and the occasional presence of vestigial lower tusks (Mammut). PMID:26839998

  17. Miocene Shark and Batoid Fauna from Nosy Makamby (Mahajanga Basin, Northwestern Madagascar)

    PubMed Central

    Andrianavalona, Tsiory H.; Ramihangihajason, Tolotra N.; Rasoamiaramanana, Armand; Ward, David J.; Ali, Jason R.; Samonds, Karen E.

    2015-01-01

    Madagascar is well known for producing exceptional fossils. However, the record for selachians remains relatively poorly known. Paleontological reconnaissance on the island of Nosy Makamby, off northwest Madagascar, has produced a previously undescribed assemblage of Miocene fossils. Based on isolated teeth, ten taxonomic groups are identified: Otodus, Carcharhinus, Galeocerdo, Rhizoprionodon, Sphyrna, Hemipristis, Squatina, Rostroraja, Himantura and Myliobatidae. Six are newly described from Madagascar for the Cenozoic (Galeocerdo, Rhizoprionodon, Sphyrna, Squatina, Rostroraja and Himantura). In association with these specimens, remains of both invertebrates (e.g., corals, gastropods, bivalves) and vertebrates (e.g., bony fish, turtles, crocodylians, and sirenian mammals) were also recovered. The sedimentary facies are highly suggestive of a near-shore/coastal plain depositional environment. This faunal association shares similarities to contemporaneous sites reported from North America and Europe and gives a glimpse into the paleoenvironment of Madagascar’s Miocene, suggesting that this region was warm, tropical shallow-water marine. PMID:26075723

  18. Miocene Shark and Batoid Fauna from Nosy Makamby (Mahajanga Basin, Northwestern Madagascar).

    PubMed

    Andrianavalona, Tsiory H; Ramihangihajason, Tolotra N; Rasoamiaramanana, Armand; Ward, David J; Ali, Jason R; Samonds, Karen E

    2015-01-01

    Madagascar is well known for producing exceptional fossils. However, the record for selachians remains relatively poorly known. Paleontological reconnaissance on the island of Nosy Makamby, off northwest Madagascar, has produced a previously undescribed assemblage of Miocene fossils. Based on isolated teeth, ten taxonomic groups are identified: Otodus, Carcharhinus, Galeocerdo, Rhizoprionodon, Sphyrna, Hemipristis, Squatina, Rostroraja, Himantura and Myliobatidae. Six are newly described from Madagascar for the Cenozoic (Galeocerdo, Rhizoprionodon, Sphyrna, Squatina, Rostroraja and Himantura). In association with these specimens, remains of both invertebrates (e.g., corals, gastropods, bivalves) and vertebrates (e.g., bony fish, turtles, crocodylians, and sirenian mammals) were also recovered. The sedimentary facies are highly suggestive of a near-shore/coastal plain depositional environment. This faunal association shares similarities to contemporaneous sites reported from North America and Europe and gives a glimpse into the paleoenvironment of Madagascar's Miocene, suggesting that this region was warm, tropical shallow-water marine. PMID:26075723

  19. Miocene small-bodied ape from Eurasia sheds light on hominoid evolution.

    PubMed

    Alba, David M; Almcija, Sergio; DeMiguel, Daniel; Fortuny, Josep; Prez de los Ros, Miriam; Pina, Marta; Robles, Josep M; Moy-Sol, Salvador

    2015-10-30

    Miocene small-bodied anthropoid primates from Africa and Eurasia are generally considered to precede the divergence between the two groups of extant catarrhineshominoids (apes and humans) and Old World monkeysand are thus viewed as more primitive than the stem ape Proconsul. Here we describe Pliobates cataloniae gen. et sp. nov., a small-bodied (4 to 5 kilograms) primate from the Iberian Miocene (11.6 million years ago) that displays a mosaic of primitive characteristics coupled with multiple cranial and postcranial shared derived features of extant hominoids. Our cladistic analyses show that Pliobates is a stem hominoid that is more derived than previously described small catarrhines and Proconsul. This forces us to reevaluate the role played by small-bodied catarrhines in ape evolution and provides key insight into the last common ancestor of hylobatids (gibbons) and hominids (great apes and humans). PMID:26516285

  20. Early Miocene granitoids from the Leo Pargil gneiss dome, northwest Himalaya

    NASA Astrophysics Data System (ADS)

    Hassett, W.; Leech, M. L.

    2007-12-01

    The Leo Pargil gneiss dome is comprised of upper amphibolite-facies metasedimentary rocks of the lower Tethyan Himalayan sequence (known as the Haimantas Group), that are intruded by numerous small granitoid bodies and leucogranite dikes. The dome is located in northern India/southwestern Tibet at the junction of the Sutlej and Spiti rivers, west of the Zada basin. U-Pb SHRIMP dating of zircon yield concordant ages ranging from Late Archean to Late Proterozoic for paragneisses (2.6 Ga to 970 Ma) corresponding to the Haimantas group, and Early Oligocene to Middle Miocene ages for granitoid intrusions (33 Ma to 15 Ma). Concordant analyses and lower intercept ages from Tera-Wasserburg concordia plots range from 28.1-17.2 Ma. Late Oligocene to Early Miocene ages are from zircon domains with consistently high U contents (1500 to over 25000 ppm). Linear regression of age vs. U content scatter plots show a trend toward younger ages (22-20 Ma) corresponding to ages from zircon with lower U contents (1000-3000 ppm) and that is consistent with lower intercept ages. These Early Miocene ages for Leo Pargil granitoids correspond to the ages for the widespread leucogranite bodies exposed throughout the Himalaya and granites from the North Himalayan gneiss domes further east.

  1. Preliminary assessment of injection, storage, and recovery of freshwater in the lower Hawthorn aquifer, Cape Coral, Florida

    USGS Publications Warehouse

    Quinones-Aponte, Vicente; Wexler, Eliezer J.

    1995-01-01

    A preliminary assessment of subsurface injection, storage and recovery of fresh canal water was made in the naturally brackish lower Hawthorn aquifer in Cape Coral, southwestern Florida. A digital modeling approach was used for this preliminary assessment, incorporating available data on hydrologic conditions, aquifer properties, and water quality to simulate density-dependent ground-water flow and advective-dispersive transport of a conservative ground-water solute (chloride ion). A baseline simulation was used as reference to compare the effects of changing various operational factors on the recovery efficiency. A recovery efficiency of 64 percent was estimated for the baseline simulation. Based on the model, the recovery efficiency increases if the injection rate and recovery rates are increased and if the ratio of recovery rate to injection rate is increased. Recovery efficiency decreases if the amount of water injected is increased; slightly decreases if the storage time is increased; is not changed significantly if the water is injected to a specific flow zone; increases with successive cycles of injection, storage, and recovery; and decreases if the chloride concentrations in either the injection water or native aquifer water are increased. In everal hypothetical tests, the recovery efficiency fluctuated between 22 and about 100 percent. Two successive cycles could bring the recovery efficiency from 60 to about 80 percent. Interlayer solute mass movement across the upper and lower boundaries seems to be the most important factor affecting the recovery efficiency. A sensitivity analysis was performed applying a technique in which the change in the various factors and the corresponding model responses are normalized so that meaningful comparisons among the responses could be made. The general results from the sensitivity analysis indicated that the permeabilities of the upper and lower flow zones were the most important factors that produced the greatest changes in the relative sensitivity of the recovery efficiency. Almost equally significant changes occurred in the relative sensitivity of the recovery efficiency when all porosity values of the upper and lower flow zones and the leaky confining units and the vertical anisotropy ratio were changed. The advective factors are the most important in the Cape Coral area according to the sensitivity analysis. However, the dispersivity values used in the model were extrapolated from studies conducted at the nearby Lee County Water Treatment Plant, and these values might not be representative of the actual dispersive characteristics of the lower Hawthorn aquifer in the Cape Coral area.

  2. Early Miocene hippopotamids (Cetartiodactyla) constrain the phylogenetic and spatiotemporal settings of hippopotamid origin.

    PubMed

    Orliac, Maeva; Boisserie, Jean-Renaud; Maclatchy, Laura; Lihoreau, Fabrice

    2010-06-29

    The affinities of the Hippopotamidae are at the core of the phylogeny of Cetartiodactyla (even-toed mammals: cetaceans, ruminants, camels, suoids, and hippos). Molecular phylogenies support Cetacea as sister group of the Hippopotamidae, implying a long ghost lineage between the earliest cetaceans (approximately 53 Ma) and the earliest hippopotamids (approximately 16 Ma). Morphological studies have proposed two different sister taxa for hippopotamids: suoids (notably palaeochoerids) or anthracotheriids. Evaluating these phylogenetic hypotheses requires substantiating the poorly known early history of the Hippopotamidae. Here, we undertake an original morphological phylogenetic analysis including several "suiform" families and previously unexamined early Miocene taxa to test previous conflicting hypotheses. According to our results, Morotochoerus ugandensis and Kulutherium rusingensis, until now regarded as the sole African palaeochoerid and the sole African bunodont anthracotheriid, respectively, are unambiguously included within the Hippopotamidae. They are the earliest known hippopotamids and set the family fossil record back to the early Miocene (approximately 21 Ma). The analysis reveals that hippopotamids displayed an unsuspected taxonomic and body size diversity and remained restricted to Africa during most of their history, until the latest Miocene. Our results also confirm the deep nesting of Hippopotamidae within the paraphyletic Anthracotheriidae; this finding allows us to reconstruct the sequence of dental innovations that links advanced selenodont anthracotheriids to hippopotamids, previously a source of major disagreements on hippopotamid origins. The analysis demonstrates a close relationship between Eocene choeropotamids and anthracotheriids, a relationship that potentially fills the evolutionary gap between earliest hippopotamids and cetaceans implied by molecular analyses. PMID:20547829

  3. Global dominance of coralline red-algal facies: A response to Miocene oceanographic events

    NASA Astrophysics Data System (ADS)

    Halfar, Jochen; Mutti, Maria

    2005-06-01

    Rhodoliths (free-living coralline red algae) can thrive under a wide range of temperatures, reduced light, and increased nutrient levels, and often form a distinct so-called rhodalgal lithofacies that is an important component of Cenozoic shallow-water carbonates. Global distributions illustrate that from the late-early to early-late Miocene (Burdigalian early Tortonian), rhodalgal facies reached peak abundances and commonly replaced coral-reef environments, accompanied by a decline in other carbonate-producing phototrophs. We argue that the dominance of red algae over coral reefs was triggered in the Burdigalian by enhanced trophic resources associated with a global increase in productivity, as evidenced by a long-term shift toward higher carbon isotope values. Rhodalgal lithofacies expanded further in the middle Miocene when strengthened thermal gradients associated with the establishment of the East Antarctic Ice Sheet led to enhanced upwelling while climate change generated increased weathering rates, introducing land-derived nutrients into the oceans. Globally cooler temperatures following a climatic optimum in the early-middle Miocene contributed to sustain the dominance of red algae and prevented the recovery of coral reefs. The global shift in nearshore shallow-water carbonate producers to groups tolerant of higher levels of trophic resources provides further evidence for increased nutrient levels during that time interval and shows the sensitivity of shallow-water carbonate facies as indicators of past oceanographic conditions.

  4. Early Miocene hippopotamids (Cetartiodactyla) constrain the phylogenetic and spatiotemporal settings of hippopotamid origin

    PubMed Central

    Orliac, Maeva; Boisserie, Jean-Renaud; MacLatchy, Laura; Lihoreau, Fabrice

    2010-01-01

    The affinities of the Hippopotamidae are at the core of the phylogeny of Cetartiodactyla (even-toed mammals: cetaceans, ruminants, camels, suoids, and hippos). Molecular phylogenies support Cetacea as sister group of the Hippopotamidae, implying a long ghost lineage between the earliest cetaceans (∼53 Ma) and the earliest hippopotamids (∼16 Ma). Morphological studies have proposed two different sister taxa for hippopotamids: suoids (notably palaeochoerids) or anthracotheriids. Evaluating these phylogenetic hypotheses requires substantiating the poorly known early history of the Hippopotamidae. Here, we undertake an original morphological phylogenetic analysis including several “suiform” families and previously unexamined early Miocene taxa to test previous conflicting hypotheses. According to our results, Morotochoerus ugandensis and Kulutherium rusingensis, until now regarded as the sole African palaeochoerid and the sole African bunodont anthracotheriid, respectively, are unambiguously included within the Hippopotamidae. They are the earliest known hippopotamids and set the family fossil record back to the early Miocene (∼21 Ma). The analysis reveals that hippopotamids displayed an unsuspected taxonomic and body size diversity and remained restricted to Africa during most of their history, until the latest Miocene. Our results also confirm the deep nesting of Hippopotamidae within the paraphyletic Anthracotheriidae; this finding allows us to reconstruct the sequence of dental innovations that links advanced selenodont anthracotheriids to hippopotamids, previously a source of major disagreements on hippopotamid origins. The analysis demonstrates a close relationship between Eocene choeropotamids and anthracotheriids, a relationship that potentially fills the evolutionary gap between earliest hippopotamids and cetaceans implied by molecular analyses. PMID:20547829

  5. Chaungtha, a new Middle Miocene mammal locality from the Irrawaddy Formation, Myanmar

    NASA Astrophysics Data System (ADS)

    Chavasseau, Olivier; Chaimanee, Yaowalak; Tun, Soe Thura; Soe, Aung Naing; Barry, John C.; Marandat, Bernard; Sudre, Jean; Marivaux, Laurent; Ducrocq, Stéphane; Jaeger, Jean-Jacques

    2006-12-01

    We describe here a mammalian assemblage originating from the locality of Chaungtha (Irrawaddy Formation, Myanmar). It represents one of the rare descriptions of a precisely located, in space, vertical section and time, fossil mammal fauna from the Irrawaddy Formation. Classically the fossil record of Irrawaddy Formation is essentially known from isolated fossils of imprecise or unknown provenance, especially concerning the stratigraphic position of the fossils along several hundred meter thick sections. The Chaungtha faunal association consists of the rhino Brachypotherium fatehjangense, the pig Conohyus thailandicus, the ruminants cf. Siamotragulus sanyathanai, cf. Siamotragulus sp. and a gomphotheriid proboscidean. This assemblage indicates that the locality is Miocene in age, and not Late Eocene as previously claimed, and roughly contemporaneous with the Chinji Formation of India-Pakistan (ca. 14-11 Ma) and with the Mae Moh Group of northern Thailand. The Chaungtha fauna, even if it displays regional characteristics, shows a strong resemblance to those of the Middle Miocene of India-Pakistan and of Thailand and reinforces the idea that South-East Asia and Pakistan were part of the same biogeographical province during the Middle Miocene.

  6. Miocene reef facies of Pelagian Block, central Mediterranean

    SciTech Connect

    Pedley, H.M.

    1988-01-01

    Miocene reefs outcrop in the Maltese Islands, southeastern Sicily, and the pelagian island of Lampedusa. Several rapid eustatic sea level fluctuations affected these late Tortonian-early Messinian build-ups; normal salinities appear to have been maintained during these events. Substrate, topography, sedimentation rate, and tectonic/eustatic events controlled reef development, which can be grouped into three settings: The most stable situation, the oldest Maltese and southeastern Sicilian reefs, has a ramp profile 15-30 km wide. The outermost zone consists of a broad belt of the large benthic foraminifer Heterostegina (compared with the underyling Oligocene beds rich in Lepidocyclina). Coralline algal carbonates, commonly rhodolitic, form a broad biostromal up-ramp association, kilometers in width, which commonly extends into the shallowest parts of the shelf. Scattered across the shallower ramp areas, in water depths generally less than 10 m, are coral-algal patch reefs, rarely larger than 20-50 m in diameter, commonly with truncated tops, and dominated by crustose coralline algae and the corals Porites and Tarbellastraea.

  7. Molecularly imprinted polymers combination with deep eutectic solvents for solid-phase extraction of caffeic acid from hawthorn.

    PubMed

    Li, Guizhen; Tang, Weiyang; Cao, Weimin; Wang, Qian; Zhu, Tao

    2015-08-01

    Molecularly imprinted polymers (MIPs) with caffeic acid as template and non-imprinted polymers (NIPs) materials were prepared in the same procedure. Field emission scanning electron microscopy (FE-SEM) and adsorption capacity test were used to evaluate characteristic of the new materials. MIPs, NIPs and C18 were used for rapid purification of caffeic acid from hawthorn with solid-phase extraction ( SPE) , and extract yields of caffeic acid with the proposed materials were 3.46 g/g, 1.01 g/g and 1.17 g/g, respectively. To optimize the MIPs-SPE procedures, different kinds of elution solutions were studied. Deep eutectic solvents (DESs) were prepared by choline chloride (ChCl)-glycerol (1/2, n/n) and choline chloride-urea (1/ 2, n/n). Methanol was mixed with the two kinds of DESs (glycerol-based DESs, urea-based DESs) in different ratios (0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, v/v), and they were used to investigated as elution solutions in the above MIPs-SPE procedures. The results showed that MIPs were potential SPE materials, and methanol/ glycerol-based DESs (3 :1, v/v) had the best elution capability with the recovery of 82.32%. PMID:26749853

  8. Late Miocene washhouse climate in Europe

    NASA Astrophysics Data System (ADS)

    Bhme, Madelaine; Ilg, August; Winklhofer, Michael

    2008-11-01

    We present two eight-million year long proxy records of precipitation for Southwest and Central Europe, covering the middle to late Miocene (5.3-13 Ma) at a temporal resolution of about 60 kyr and 150 kyr, respectively. The estimates of precipitation are based on the ecophysiological structure of herpetological assemblages (amphibians and reptiles). From 13.0 Ma until about 9 Ma, both records show a similar trend, evolving from a long dry period (13-11 Ma) into a "washhouse climate" (10.2-9.8 Ma), characterized by global warm conditions and several times more precipitation than present. The transition from washhouse to a dryer climate between 9.7 and 9.5 Ma and the concomitant cooling episode appear to have triggered a severe biotic event known as the Vallesian crisis, which included the extinction of hominoids in Western Europe. A second washhouse period (9.0-8.5 Ma), coeval with a global warm episode, was unprecedentedly intense in Southwest Europe, but less pronounced in Central Europe. From 8 Ma onward, a divergence in the two precipitation records is observed, with Southwest Europe staying wetter and Central Europe becoming dryer than present. Both precipitation records are combined into a common run-off curve as a measure of the relative intensity of the hydrological cycle for moderate latitudes of continental Europe. The run-off curve shows a remarkable positive correlation with Atlantic deep-water temperatures from Cear Rise by Lear et al. (2003), which are significantly higher (up to + 3 C) during the two washhouse periods and show no other positive excursion of comparable magnitude. We discuss potential links and the role of the coeval temporary restriction of the Central American Seaway on ocean and atmosphere circulation.

  9. New method to estimate paleoprecipitation using fossil amphibians and reptiles and the middle and late Miocene precipitation gradients in Europe

    NASA Astrophysics Data System (ADS)

    Bhme, M.; Ilg, A.; Ossig, A.; Kchenhoff, H.

    2006-06-01

    Existing methods for determining paleoprecipitation are subject to large errors (350 400 mm or more using mammalian proxies), or are restricted to wet climate systems due to their strong facies dependence (paleobotanical proxies). Here we describe a new paleoprecipitation tool based on an indexing of ecophysiological groups within herpetological communities. In recent communities these indices show a highly significant correlation to annual precipitation (r2 = 0.88), and yield paleoprecipitation estimates with average errors of 250 280 mm. The approach was validated by comparison with published paleoprecipitation estimates from other methods. The method expands the application of paleoprecipitation tools to dry climate systems and in this way contributes to the establishment of a more comprehensive paleoprecipitation database. This method is applied to two high-resolution time intervals from the European Neogene: the early middle Miocene (early Langhian) and the early late Miocene (early Tortonian). The results indicate that both periods show significant meridional precipitation gradients in Europe, these being stronger in the early Langhian (threefold decrease toward the south) than in the early Tortonian (twofold decrease toward the south). This pattern indicates a strengthening of climatic belts during the middle Miocene climatic optimum due to Southern Hemisphere cooling and an increased contribution of Arctic low-pressure cells to the precipitation from the late Miocene onward due to Northern Hemisphere cooling.

  10. A molecular organic carbon isotope record of miocene climate changes

    SciTech Connect

    Schoell, M. ); Schouten, S.; Sinninghe Damste', J.S.; Leeuw, J.W. de ); Summons, R.E. )

    1994-02-25

    The difference in carbon-13 ([sup 13]C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in [sup 18]O ([delta][sup 18]O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes ([delta][sup 13]C = 25.4 [+-] 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfur-bound C[sub 35] hopanes (likely derived from bacterial plankton living at the base of the photic zone) have systematically decreasing [sup 13]C concentrations in Middle and Late Miocene samples ([delta][sup 13]C = 29.5 to [minus]31.5 per mil), consistent with the Middle Miocene formation of a carbon dioxide-rich cold water mass at the base of the photic zone.

  11. Chad Basin: Paleoenvironments of the Sahara since the Late Miocene

    NASA Astrophysics Data System (ADS)

    Schuster, Mathieu; Duringer, Philippe; Ghienne, Jean-Franois; Roquin, Claude; Sepulchre, Pierre; Moussa, Abderamane; Lebatard, Anne-Elisabeth; Mackaye, Hassan Taisso; Likius, Andossa; Vignaud, Patrick; Brunet, Michel

    2009-08-01

    Since the mid 1990s, the Mission paloanthropologique francotchadienne (MPFT) conducts yearly paleontological field investigations of the Miocene-Pliocene of the Chad Basin. This article synthesizes some of the results of the MPFT, with focus on the Chad Basin development during the Neogene. We propose an overview of the depositional paleoenvironments of this part of Africa at different scales of time and space, based on a multidisciplinary approach (sedimentary geology, geomorphology, geophysic, numerical simulations and geochronology). The Miocene-Pliocene paleoenvironments are examined through the sedimentary archives of the early hominids levels and the Holocene Lake Mega-Chad episode illustrates the last major paleoenvironmental change in this area. The sedimentary record of the Chad Basin since the Late Miocene can be schematized as the result of recurrent interactions from lake to desert environments.

  12. Middle Miocene closure of the Central American Seaway

    NASA Astrophysics Data System (ADS)

    Montes, C.; Cardona, A.; Jaramillo, C.; Pardo, A.; Silva, J. C.; Valencia, V.; Ayala, C.; Prez-Angel, L. C.; Rodriguez-Parra, L. A.; Ramirez, V.; Nio, H.

    2015-04-01

    Uranium-lead geochronology in detrital zircons and provenance analyses in eight boreholes and two surface stratigraphic sections in the northern Andes provide insight into the time of closure of the Central American Seaway. The timing of this closure has been correlated with Plio-Pleistocene global oceanographic, atmospheric, and biotic events. We found that a uniquely Panamanian Eocene detrital zircon fingerprint is pronounced in middle Miocene fluvial and shallow marine strata cropping out in the northern Andes but is absent in underlying lower Miocene and Oligocene strata. We contend that this fingerprint demonstrates a fluvial connection, and therefore the absence of an intervening seaway, between the Panama arc and South America in middle Miocene times; the Central American Seaway had vanished by that time.

  13. Middle Miocene closure of the Central American Seaway.

    PubMed

    Montes, C; Cardona, A; Jaramillo, C; Pardo, A; Silva, J C; Valencia, V; Ayala, C; Pérez-Angel, L C; Rodriguez-Parra, L A; Ramirez, V; Niño, H

    2015-04-10

    Uranium-lead geochronology in detrital zircons and provenance analyses in eight boreholes and two surface stratigraphic sections in the northern Andes provide insight into the time of closure of the Central American Seaway. The timing of this closure has been correlated with Plio-Pleistocene global oceanographic, atmospheric, and biotic events. We found that a uniquely Panamanian Eocene detrital zircon fingerprint is pronounced in middle Miocene fluvial and shallow marine strata cropping out in the northern Andes but is absent in underlying lower Miocene and Oligocene strata. We contend that this fingerprint demonstrates a fluvial connection, and therefore the absence of an intervening seaway, between the Panama arc and South America in middle Miocene times; the Central American Seaway had vanished by that time. PMID:25859042

  14. The Late Miocene climate response to global vegetation change

    NASA Astrophysics Data System (ADS)

    Micheels, Arne; Eronen, Jussi; Fortelius, Mikael; Mosbrugger, Volker; Uhl, Dieter

    2010-05-01

    The Late Miocene belongs to the late phase of the Cenozoic climate cooling, but proxy data indicate that it was still a generally warm and humid episode as compared to today. Corresponding to the overall warm and humid conditions, there were generally more forests and less desert in the Miocene. Especially northern high latitudes were warmer than at present and palaeovegetation was characterised rather more by boreal forests than tundra like today. The vegetation change from the Miocene to present was a result of the overall climate cooling, but based on a climate modelling sensitivity experiment we demonstrate that vegetation changes also contributed to Cenozoic climate cooling. We perform two experiments using the atmosphere-ocean general circulation model COSMOS with the physical boundary conditions representing the Late Miocene. For instance, the model runs consider a lower elevation of the Tibetan Plateau, an open Central American Isthmus and the Paratethys. In order to address the Miocene-to-present vegetation change, one experiment includes the modern vegetation while the other one uses the palaeovegetation. The global temperature of the experiment using the modern vegetation is by 1.6 °C lower than using the palaeovegetation. This is in the same order of magnitude as moderate future climate change projections, if one considers that the sign needs to be reversed. From our sensitivity experiment, we observe that particularly high latitudes get cooler because of replacing boreal forests with modern tundra vegetation. The albedo effect is relevant to understand how the vegetation change from the Miocene to present in the high latitudes contributes to the climate cooling trend. Our results emphasise that the role of vegetation is important to understand past climates.

  15. Oligocene-Miocene deformational and depositional history of the Andean hinterland basin in the northern Altiplano plateau, southern Peru

    NASA Astrophysics Data System (ADS)

    Perez, Nicholas D.; Horton, Brian K.

    2014-09-01

    Cenozoic basin fill of the northern Altiplano plateau records the tectonic development of the flanking Western Cordillera magmatic arc and Eastern Cordillera fold-thrust belt. The Ayaviri hinterland basin of southern Peru contains a ~2300 m thick succession of fluvial sandstones and overbank siltstones (upper Oligocene Puno Group and lower Miocene lower Tinajani Formation) capped by ~400 m of alluvial fan conglomerates (middle Miocene upper Tinajani Formation). New U-Pb zircon chronostratigraphic constraints from ~30 to 15 Ma yield sediment accumulation rates of 110-660 m/Myr. Newly dated growth strata highlight the genetic role played by thrust displacement in basin evolution. A several phase accumulation history derived from chronostratigraphic, provenance, and structural data reveals Oligocene basin filling by fluvial sand and mud that changes provenance from Western Cordillera Mesozoic-Cenozoic volcanic rocks to Paleozoic-Mesozoic Eastern Cordillera sedimentary rocks driven by deformation along the southwest directed, northeastern basin margin Ayaviri thrust at 28-26 Ma. Continued early Miocene fluvial deposition was sourced solely from the Eastern Cordillera. An abrupt middle Miocene shift to coarse alluvial fan deposition sourced from the Western Cordillera was driven by out-of-sequence deformation along the northeast directed, southwestern basin margin Pasani thrust at 18-16 Ma. This northern Altiplano out-of-sequence deformation was coincident with increased Eastern and Western Cordillera exhumation and thrusting and may be symptomatic of changes in critical wedge dynamics. The overall record of basin sedimentation and syndepositional fold-thrust deformation emphasizes the role of regional shortening in governing crustal thickening and basin evolution in the central Andes during the Oligocene to Miocene.

  16. Simultaneous determination and pharmacokinetic comparisons of multi-ingredients after oral administration of radix salviae miltiorrhizae extract, hawthorn extract, and a combination of both extracts to rats.

    PubMed

    Liu, Yu-Qiang; Cai, Qian; Liu, Chang; Bao, Feng-Wei; Zhang, Zhen-Qiu

    2014-01-01

    A simple and sensitive HPLC method was developed for simultaneous determination of danshensu (DSS), rosmarinic acid (RA), lithospermic acid (LA), salvianolic acid B (SAB), and hyperoside (HP) in rat plasma. This method validated was successfully applied to the pharmacokinetic study of the main active ingredients after oral administration of Radix Salviae Miltiorrhizae extract (SME), hawthorn extract (HTE), and a combination of both extracts (2.5?:?1) to rats. The results indicated that there have been great differences in pharmacokinetics between a single extract and a combination of both extracts. A combination of both extracts can enhance their bioavailabilities and delay the elimination of SAB and DSS in rats. PMID:24660090

  17. Simultaneous Determination and Pharmacokinetic Comparisons of Multi-Ingredients after Oral Administration of Radix Salviae Miltiorrhizae Extract, Hawthorn Extract, and a Combination of Both Extracts to Rats

    PubMed Central

    Liu, Yu-Qiang; Cai, Qian; Liu, Chang; Bao, Feng-Wei; Zhang, Zhen-Qiu

    2014-01-01

    A simple and sensitive HPLC method was developed for simultaneous determination of danshensu (DSS), rosmarinic acid (RA), lithospermic acid (LA), salvianolic acid B (SAB), and hyperoside (HP) in rat plasma. This method validated was successfully applied to the pharmacokinetic study of the main active ingredients after oral administration of Radix Salviae Miltiorrhizae extract (SME), hawthorn extract (HTE), and a combination of both extracts (2.5?:?1) to rats. The results indicated that there have been great differences in pharmacokinetics between a single extract and a combination of both extracts. A combination of both extracts can enhance their bioavailabilities and delay the elimination of SAB and DSS in rats. PMID:24660090

  18. Interpretation of Samburupithecus, an upper Miocene hominoid from Kenya

    NASA Astrophysics Data System (ADS)

    Pickford, Martin; Ishida, Hidemi

    1998-02-01

    Samburupithecus, an extinct great ape from upper Miocene (9.5 Ma) deposits in Kenya, is compared with other fossil and extant hominoids. It possesses features which are derived in comparison with Proconsul and other Lower and Middle Miocene hominoids, but it has none of the derived features which characterize the Eurasian large apes. It possesses characters which indicate that its closest relationships lie with the AAH clade (extant African apes and man). Within this clade it is closest dentally to primitive hominids such as Praeanthropus.

  19. First record of Mylagaulid rodents (Rodentia, Mammalia) from the Miocene of Eastern Siberia (Olkhon Island, Baikal Lake, Irkutsk Region, Russia).

    PubMed

    Tesakov, A S; Lopatin, A V

    2015-01-01

    A new genus and species of rodent, Lamugaulus olkhonensis, belonging to the subfamily Promylagaulinae of the family Mylagaulidae, is described on the basis of isolated teeth from the Khalagay Formation of the Lower Miocene Tagay locality (Olkhon island, Lake Baikal, Irkutsk Region). This is the first record of mylagaulids in Eastern Siberia, significantly expanding the data on the distribution of this mainly North American group of rodents in Asia and showing its presence outside the Central Asian arid zone. PMID:25773245

  20. Stratigraphical and palaeontological characteristics of the Miocene deposits at Soluq area, NE Libya: First Results

    NASA Astrophysics Data System (ADS)

    Abdulsamad, E. O.; El Zanati, S. M.

    2012-04-01

    The north-south scarp that runs in the middle of Soluq area, about 70 km southeast of Benghazi, attains altitudes towards the north, reaching a maximum of about 300 meters above sea level at wadi al Qattarah. The scarp fades gradually towards the south till at Antelat area and is represented by few meters high hills. The plateau, however, extends eastwards rising to altitudes more than 450 meters above sea level. The plain (known as Soluq plain) extends westwards till near the Mediterranean coast with average width of about 50 kilometers. Several outcrops along the main escarpment have been visited and spot sampled and two carbonate rock units separated by reduced deposits of clastic origin have been recognised based on lithology and faunal contents. The oldest rock unit is representing by the Benghazi Formation and the youngest rock unit is representing by Wadi al Qattarah Formation. Both rock units, nevertheless, are belonging to the Miocene Ar Rajmah Group and cover the greater part of the Soluq area. The lower Benghazi Formation has been dated as Middle Miocene based on the presence of Lepidocyclina (Eulepidina) dilatat (Michelotti) and Borelis melo melo (Fichiteli). The latter taxon was recognized in different local areas of the same time-interval. The inconsistent occurrences and broken nature of tests of Borelis melo melo in some levels in the upper Wadi al Qattarah Formation, however, indicates that this taxon has been subjected to extensive reworking and Late Miocene age is ascribed to the major deposits of the later rock unit. This assumption may explain the occurrences of a number of lenses and irregular bodies of gypsum of the Messenian event in study region. The high variety of the microfacies and fossil assemblages recognised in this study reflects (1) the variety of environmental settings and (2) the effect of the lithofacies on the fossil recovery. In general, larger and small foraminifera from the Miocene Ar Rajmah Group are a mix of infaunal and epifaunal taxa in which a prevalence of free, larger epifaunal types has been recorded. The depositional history of the studied sequence, however, has been interpreted in terms of Wilson standard carbonate facies belts and indicate an overall shallowing upward trend, from open platform (Benghazi Formation) to restricted platform and restricted lagoon-saline conditions (Wadi al Qattarah Formation).

  1. Provenance study conflict Miocene eolian deposit in central China

    NASA Astrophysics Data System (ADS)

    Liu, S.; Stockli, D. F.; Li, J.; Song, C.

    2013-12-01

    The dispute of fine-grained Miocene sediments from Tianshui Basin, northeastern Tibetan Plateau as eolian loess-paleosol or neptunian mudflat/distal fan is an unresolved hot topic in Cenozoic palaeoclimatology , impacting further research of Asian monsoon and the mechanism of its variations. Tratigraphic correlation and constraining the sedimentary age with paleomagnetic method show that hundreds miles of foreland basin stratums occurred in north of West Qinling mountain belt in Miocene. The tratums are about 2000 m thick in the south foredeep range, thinning to less than 300 m thick in the north backbulge range. Similar heavy minerals composition and detrital ziron U/Pb ages distribution also show that the materials in the basin were from the same denuded regions. Such evidences conform that the Miocene sedimentary sections identified as loess in Tianshui basin could be distal fan and flood plain in the united foreland basin system. Comprehensive provenance techniques of heavy minerals and detrital zircon U/Pb ages show differences between Miocene Tianshui sediments and Pliocene- Quaternary loess- red clay from Chinese loess Plateau. Specifically, samples from Tianshui basin have more than 20% of Magnetite and 30% of Epidote, but Amphibole is lacking. Loess-red clay samples consist of 21% Amphibole on average. Classifying degree of correction of Amphibole proves that weathering erosion is not the reason for this dissimilarity. More Amphibole rich iginous rocks or matemorphoic rocks could exist widely in loess's source region. Most zircon U/Pb ages in this study fall into similar ranges, especially from 200Ma to 500Ma. There is a significant age peak from 200Ma to 250Ma in Tianshui sediments and modern river sands originating from West Qinling mountain belt, which is rare in loess-red clay samples. A part of zircons from loess and red clay contain very low U and Th elements, implying some of Mafic or intermediate rocks in eolian source area. Both Mafic and intermediate rocks can be found in north of Tibetan Plateau, the recommended initial source area of Quaternary loess. West Qinling mountain belt is composed mainly of Mesozoic sedimentary rocks and granite, which can only provide materials absent of amphiboles and some local peaks of zircon U/Pb ages. They have been confirmed in Tianshui Miocene samples. We propose that the materials from recommended source areas of Pliocene- Quaternary loess-red clay did not join in the Tianshui basin in Miocene. This conclusion may also challenge previous viewpoints that Asian monsoon can be dated back to early Miocene.

  2. The early to mid-Miocene environment of Antarctica

    NASA Astrophysics Data System (ADS)

    Ashworth, A. C.; Lewis, A.

    2012-12-01

    Paleoecological studies in the Transantarctic Mountains of the McMurdo region provide evidence that the climate was both warmer and wetter in the early to mid-Miocene than it was during the late Miocene. The climate change was accompanied by a shift from wet- to cold-based glaciation in the TAM and the probable growth of the polar ice sheet. Terrestrial and freshwater aquatic fossil assemblages from the Friis Hills (77°S) and the Olympus Range (77°S), with endpoint 40Ar/39Ar ages on tephras of 19.76 Ma and 14.07 Ma, respectively, indicate climatic cooling during the interval. At c.14 Ma, the temperature dropped below the threshold required to support the plants and insects of a tundra biome, and they became extinct. This interpretation is supported by pollen studies from Ross Sea cores. The extinction of the tundra biota on the continent appears to have been time-transgressive, occurring at 12.8 Ma on the Antarctic Peninsula. Evidence of climatic cooling from early to mid-Miocene is based on a decrease in biodiversity. During interglacial phases of the early Miocene, the poorly drained valley of the Friis Hills supported a sexually-reproducing moss community dominated by Campylium cf. polygamum, which today grows on the margins of lakes and in soil between boulders. Wood and leaves of Nothofagus (Southern Beech), and the seeds of at least five other angiosperm species are preserved as fossils. In addition, there are abundant megaspores and spiny, curved leaves of the aquatic lycopod Isoetes (Quillwort), as well as chitinous remains of curculionid beetles and Chironomidae (midges). During glacial phases, the only fossils found are Nothofagus leaves of a species which appears to be different than that associated with the interglacial phases. Pollen supports the interpretation that there was more than one species of Nothofagus in the vegetation. The types and numbers of species indicate that the vegetation was a shrub tundra. The closest modern analog for the fossil assemblage is at treeline and higher on Isla Navarino (55°S) at the southern tip of South America. By mid-Miocene, the upland tundra biota was less diverse, most notably in the number of angiosperm taxa. Based on the autecology and geographic distributions of the descendants of the fossil biota which survive in the subantarctic islands, South America and Tasmania, there was a decline of mean summer temperatures from c. 6°C to c. 4°C from the early to the mid-Miocene. During the early Miocene, the MST of the TAM was c.19°C warmer than today. A paleotemperature estimate based on leaf waxes from a Ross Sea core is for a MST 11°C warmer than today which seems low considering it is based on a near sea-level vegetation. A recent paper utilizing a salt-hydration process to provide adequate moisture to support a Miocene tundra biota is based on erroneous data. The Miocene climate was wet with an annual precipitation of at least 3000 mm. A recent report of the possible survival of vegetation in the Taylor Valley until the Pliocene, based on the discovery of 5 Ma wood-like forms in a DVDP core, is improbable. Even if wood can be definitively identified from the Pliocene deposits it is likely to be reworked Miocene wood from uplands in the TAM (e.g. Friis Hills). Research supported by NSF OPP 0739693.

  3. Palynology of latest Neogene (Middle Miocene to late Pliocene) strata in the Delmarva Peninsula of Maryland and Virginia

    USGS Publications Warehouse

    Sirkin, L.; Owens, J.P.

    1998-01-01

    Palynology of Miocene and Pliocene formations in the Delmarva Peninsula of Maryland and Virginia reveals a significant representation of exotic pollen interspersed in pollen assemblages that are otherwise comparable to those from the modern vegetation of the Mid-Alantic coastal plain region. The late Tertiary arboreal pollen (AP) assemblages are dominated by oak, hickory, pine, birch and alder with minor amounts of mid- and southern coastal tree taxa, as well as minor spruce and hemlock and a trace of fir. Nonarboreal pollen (NAP) include grass, sedge, composite and aquatic taxa. Exotic pollen in these assemblages represent plants now foreign to this region. They may be placed in three categories. First, there are extinct forms, such as Labrapollis, Plicatopollis, and Multiporopollenites, that can be traced from the Cretaceous or Early Tertiary into the Late Tertiary. The second group includes forms, such as Podocarpus, Engelhardtia, Pterocarya, Ephedra, Eucommia, Ulmus-Zelkova, Glyptostrobus, Palmae, and Cyathea, that are not found in this region today and not found in early Pleistocene sediments in the eastern United States. Many of these taxa are subtropical or greatly restricted in geographic range. A third group of exotics, mainly Cyrilla, Planera, Gordonia, Jussiaea, and Sapotacaea, including Minusops, are generally found south of the study area or have their northern limit here at this time. The lack of the extinct or distant exotics in early to mid-Pleistocene sediments in the mid-Atlantic coastal plain and the last appearance of Pterocarya, as the last exotic taxon in the early Pleistocene of western Europe, support the stratigraphic assignment of the Pliocene units. The number of exotic taxa diminish markedly between the Miocene pollen assemblages and those of the Late Pliocene. Climatic fluctuations characterize the Late Tertiary environments. The Miocene, for example, incorporates a warming trend between the upper, middle Miocene and the Manokin beds and the late Miocene of the Pokomoke beds. The late Miocene was probably somewhat warner than the present climate in the Delmarva region. This trend is based on the presence of colder climate indicators, mainly spruce and hemlock, in the Manokin pollen record. The two distinct pollen assemblages constitute two pollen zones. Similarly, the Pliocene pollen record also shows a warming trend. The pollen zone of the Yorktown Formation of the early Pliocene age contains the colder climate indicators spruce and hemlock. The Beaverdam and Walston formation of late Pliocene age contain pollen assemblages that reflect climatic conditions warmer than the present time.

  4. Occlusal Enamel Complexity in Middle Miocene to Holocene Equids (Equidae: Perissodactyla) of North America

    PubMed Central

    Famoso, Nicholas A.; Davis, Edward Byrd

    2014-01-01

    Four groups of equids, Anchitheriinae, Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, but only the Equini remains after 16 Myr of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes influencing the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. We investigated Occlusal Enamel Index, a quantitative method for the analysis of the complexity of occlusal patterns. We used analyses of variance and an analysis of co-variance to test whether equid teeth increase resistive cutting area for food processing during mastication, as expressed in occlusal enamel complexity, in response to increased abrasion in their diet. Results suggest that occlusal enamel complexity was influenced by climate, phylogeny, and tooth position through time. Occlusal enamel complexity in middle Miocene to Modern horses increased as the animals experienced increased tooth abrasion and a cooling climate. PMID:24587267

  5. Occlusal enamel complexity in middle miocene to holocene equids (Equidae: Perissodactyla) of North America.

    PubMed

    Famoso, Nicholas A; Davis, Edward Byrd

    2014-01-01

    Four groups of equids, "Anchitheriinae," Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, but only the Equini remains after 16 Myr of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes influencing the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. We investigated Occlusal Enamel Index, a quantitative method for the analysis of the complexity of occlusal patterns. We used analyses of variance and an analysis of co-variance to test whether equid teeth increase resistive cutting area for food processing during mastication, as expressed in occlusal enamel complexity, in response to increased abrasion in their diet. Results suggest that occlusal enamel complexity was influenced by climate, phylogeny, and tooth position through time. Occlusal enamel complexity in middle Miocene to Modern horses increased as the animals experienced increased tooth abrasion and a cooling climate. PMID:24587267

  6. A new pitheciin primate from the middle Miocene of Argentina.

    PubMed

    Kay, R F; Johnson, D; Meldrum, D J

    1998-01-01

    We report here a new fossil primate from the middle Miocene of Argentina. The material consists of isolated teeth, mandibular fragments, and a talus. The fossils were collected in the Colln Cura formation at Caadn del Tordillo in Neuqun Province. An age of 15.71 +/- 0.07 Ma has been reported for the Pilcaniyeu Ignimbrite, which lies just below the paleosols in which the fossils were found. This material is thus the youngest occurrence of fossil primates in Argentina (hitherto documented in the Santacrucian and older land mammal ages) but still is older than the middle Miocene platyrrhine primates from La Venta, Colombia, in particular the pitheciins Nuciruptor and Cebupithecia. The material is recognized as a new genus and species of Pitheciinae, Propithecia neuquenensis. The mesiodistally compressed, high-crowned incisors are specialized and similar to species in the tribe Pithecini and to the nonpitheciin Soriacebus (early Miocene, Patagonia). We rule out a phylogenetic relationship to the latter because of differences in molar morphology. Propithecia does, however, fit well into the pattern of pitheciin evolution, being more derived than the middle Miocene pitheciin Nuciruptor but not as much as another middle Miocene taxon, Cebupithecia. As such, this makes Propithecia the oldest taxon that can be confidently placed within this modern New World monkey subfamily. By analogy with the molar structures and diets of extant platyrrhines, Propithecia has a molar structure consistent with a variety of low-fiber diets ranging from fruit and gum to seeds. Its incisors suggest seed-eating in much the same way as extant pitheciins, like Pithecia. The talus resembles that of Callicebus, suggesting arboreal quadrupedal locomotion. PMID:9702279

  7. Systematics and Evolution of the Miocene Three-Horned Palaeomerycid Ruminants (Mammalia, Cetartiodactyla)

    PubMed Central

    Sánchez, Israel M.; Cantalapiedra, Juan L.; Ríos, María; Quiralte, Victoria; Morales, Jorge

    2015-01-01

    Palaeomerycids were strange three-horned Eurasian Miocene ruminants known through fossils from Spain to China. We here study their systematics, offering the first cladistic phylogeny of the best-known species of the group, and also reassess their phylogenetic position among ruminants, which is currently disputed. The beautifully preserved remains of a new palaeomerycid from middle Miocene deposits of Spain, Xenokeryx amidalae gen. et sp. nov., helps us to better understand palaeomerycid anatomy, especially that of the nuchal region in the skull, significantly improving our current knowledge on these enigmatic ruminants. Our results show two main lineages of palaeomerycids, one containing the genus Ampelomeryx diagnosed by a characteristic type of cranium / cranial appendages and some dental derived traits, and another one that clusters those forms more closely related to Triceromeryx than to Ampelomeryx, characterized by a more derived dentition and a set of apomorphic cranial features. Xenokeryx branches as a basal offshoot of this clade. Also, we find that Eurasian palaeomerycids are not closely related to North American dromomerycids, thus rejecting the currently more accepted view of palaeomerycids as the Eurasian part of the dromomerycid lineage. Instead of this, palaeomerycids are nested with the African Miocene pecoran Propalaeoryx and with giraffoids. On the other hand, dromomerycids are closely related to cervids. We define a clade Giraffomorpha that includes palaeomerycids and giraffids, and propose an emended diagnosis of the Palaeomerycidae based on cranial and postcranial characters, including several features of the cranium not described so far. We also define the Palaeomerycidae as the least inclusive clade of pecorans containing Triceromeryx and Ampelomeryx. Finally, we reassess the taxonomy of several palaeomerycid taxa. PMID:26630174

  8. Life history of hawthorn spider mite Amphitetranychus viennensis (Acarina: Tetranychidae) on various apple cultivars and at different temperatures.

    PubMed

    Kasap, Ismail

    2003-01-01

    Development duration and reproduction rate of hawthorn spider mite Amphitetranychus viennensis (Zacher) were carried out on five different apple cultivars (Amasya (local cultivar), Golden Delicious, Granny Smith, Starking Delicious and Starkrimson Delicious) at 25 degrees C, 65 +/- 10% RH and 16:8 L:D. In addition, the same parameters were determined on Golden Delicious leaves at three constant temperatures (20, 30 and 35 degrees C, 65 +/- 10% RH and 16:8 L:D) in the laboratory. A. viennensis showed a better performance on Golden Delicious than on the other apple cultivars. This was mainly due to a short development time (10.7 days), high daily egg production (5.2 eggs/female/day) and early reproduction peak. The highest intrinsic rate of natural increase (rm) was determined on the variety Golden Delicious (rm = 0.247/day), while the lowest one was observed on the variety Starking Delicious (rm = 0.215/day). The developmental periods of A. viennensis varied from 7.4 to 18.8 days at 35 and 20 degrees C for females, while it varied from 7.9 to 17.2 days at 30 and 20 degrees C for males. The development threshold of the eggs and pre-adult stages were 9.72 and 9.07 degrees C, total effective temperature was 72.99 and 185.18 degree-days, respectively. The mean generation time (To) of the population ranged from 16.13 days at 30 degrees C to 29.15 days at 20 degrees C. The net reproductive rate (R0) increased from 54.33 female/female at 20 degrees C to 78.34 female/female at 25 degrees C, and decreased to 75.71 female/female at 30 degrees C. The highest intrinsic rate of increase (rm) was reached at 30 C (rm = 0.268/day), the lowest one at 20 degrees C (rm = 0.136/day). PMID:14756403

  9. A New Late Miocene Odobenid (Mammalia: Carnivora) from Hokkaido, Japan Suggests Rapid Diversification of Basal Miocene Odobenids

    PubMed Central

    Tanaka, Yoshihiro; Kohno, Naoki

    2015-01-01

    The modern walrus, Odobenus rosmarus, is specialized and only extant member of the family Odobenidae. They were much more diversified in the past, and at least 16 genera and 20 species of fossil walruses have been known. Although their diversity increased in the late Miocene and Pliocene (around 8–2 Million years ago), older records are poorly known. A new genus and species of archaic odobenid, Archaeodobenus akamatsui, gen. et sp. nov. from the late Miocene (ca. 10.0–9.5 Ma) top of the Ichibangawa Formation, Hokkaido, northern Japan, suggests rapid diversification of basal Miocene walruses. Archaeodobenus akamatsui is the contemporaneous Pseudotaria muramotoi from the same formation, but they are distinguishable from each other in size and shape of the occipital condyle, foramen magnum and mastoid process of the cranium, and other postcranial features. Based on our phylogenetic analysis, A. akamatsui might have split from P. muramotoi at the late Miocene in the western North Pacific. This rapid diversification of the archaic odobenids occurred with a combination of marine regression and transgression, which provided geological isolation among the common ancestors of extinct odobenids. PMID:26244784

  10. A New Late Miocene Odobenid (Mammalia: Carnivora) from Hokkaido, Japan Suggests Rapid Diversification of Basal Miocene Odobenids.

    PubMed

    Tanaka, Yoshihiro; Kohno, Naoki

    2015-01-01

    The modern walrus, Odobenus rosmarus, is specialized and only extant member of the family Odobenidae. They were much more diversified in the past, and at least 16 genera and 20 species of fossil walruses have been known. Although their diversity increased in the late Miocene and Pliocene (around 8-2 Million years ago), older records are poorly known. A new genus and species of archaic odobenid, Archaeodobenus akamatsui, gen. et sp. nov. from the late Miocene (ca. 10.0-9.5 Ma) top of the Ichibangawa Formation, Hokkaido, northern Japan, suggests rapid diversification of basal Miocene walruses. Archaeodobenus akamatsui is the contemporaneous Pseudotaria muramotoi from the same formation, but they are distinguishable from each other in size and shape of the occipital condyle, foramen magnum and mastoid process of the cranium, and other postcranial features. Based on our phylogenetic analysis, A. akamatsui might have split from P. muramotoi at the late Miocene in the western North Pacific. This rapid diversification of the archaic odobenids occurred with a combination of marine regression and transgression, which provided geological isolation among the common ancestors of extinct odobenids. PMID:26244784

  11. Chemical evolution of Miocene wood: Example from the Belchatow brown coal deposit, central Poland

    USGS Publications Warehouse

    Drobniak, A.; Mastalerz, Maria

    2006-01-01

    Miocene conifer wood samples from the Belchatow brown coal deposit in Poland were studied in order to discuss a range of chemical variations that occur as a result of biochemical coalification. Petrographic analysis, ultimate analysis, electron microprobe technique, and FTIR spectroscopy were used in this study. Our data show several progressive trends in functional groups distribution that take place during the wood transformation from group 1 to group 4, such as an overall increase in aromaticity, an increase in lignin/cellulose ratio, and an increase in oxygen functionalities. Other observations include an increase in aliphatic stretching and bending functionalities from groups 1 to 3; followed by a decrease in the wood of group 4; appearance of aliphatic out-of-plane bands in group 3 and increase in group 4; an increase in CH2/CH3 in group 4 compared to the other groups; and decrease in O-H groups in group 4 compared to other groups. These observations, together with other chemical and petrological observations, indicate that the progressive elimination of cellulose and modification of lignin are dominant processes of the wood transformation. ?? 2005 Elsevier B.V. All rights reserved.

  12. Anatomical and developmental study of petrified Quercus (Fagaceae) fruits from the Middle Miocene, Yakima Canyon, Washington, USA.

    PubMed

    Borgardt, S J; Pigg, K B

    1999-03-01

    The first reported petrified acorns to show internal anatomical structure are here described from Middle Miocene (?15.6 million years old) chert of the Columbia River Basalt Group in Yakima Canyon, Washington. Quercus hiholensis Borgardt et Pigg sp. nov. is described from anatomical and morphological fruit features, as well as a little recognized anatomical feature, the umbilical complex. Acorns, each comprising a nut and its cupule, are up to 15.3 mm long and 18.8 mm wide with helically arranged, imbricate, tuberculate cupule scales. They show basal aborted ovules, short styles, broad stigmas, and lack grooves in their cotyledons. These characters and the developmental pattern seen in these fossil acorns demonstrate that Q. hiholensis conforms to genus Quercus (Fagaceae), subgenus Quercus, section Quercus (the white oaks). The correspondence of Q. hiholensis to the modern section Quercus reveals that the derived floral and fruit characters that distinguish section Quercus within the genus had evolved by the Middle Miocene. PMID:10077494

  13. Coarse-grained deltaic sedimentation in the Miocene Cuyama strike-slip basin, California Coast Ranges

    USGS Publications Warehouse

    Alan, Bartow J.

    1990-01-01

    The Cuyama basin, located in the southern Coast Ranges of California southwest of the San Andreas fault, developed early in the history of the San Andreas transform system. The Miocene marine basin formed in a transtensional setting along a dextral strike-slip fault of the transform system following Oligocene non-marine basin formation in an extensional setting. The lower and middle Miocene Vaqueros Formation in the northwestern part of the basin, which represents the first of two transgressive-regressive cycles, is described here in terms of nine facies in two broad facies groups. The 400-m-thick Soda Lake Shale Member (of the Vaqueros) comprises deep-basin and starved-basin facies. A thin transgressive facies occurs locally at the base of the formation. The overlying Painted Rock Sandstone Member (of the Vaqueros), which is more than 2200 m thick and consists mostly of coarse-grained sandstone and pebbly sandstone, constitutes a delta complex of prodelta, slope channel, delta front, tide-influenced distributary channel, interdistributary bay, and fluvial channel facies. The basinal depositional system consisted of turbidite mud and sand, and hemipelagic and pelagic sediments of the basinal facies deposited in a rapidly subsiding basin. The delta depositional system consisted of the delta complex facies that prograded into the deep basin and had a steep prodelta slope that extended to bathyal depths. The delta is inferred to be a mixed fluvial-wave-dominated fan delta, analogous in its delta-front morphology and processes to a fjord delta, in which coarse sediment delivered to the delta front by braided streams was transported down the prodelta slope into deep water by sediment gravity flows. Transgression and rapid deepening of the basin in the early Miocene coincided with rapid tectonic subsidence. Deepening culminated with deposition of a starved-basin facies or condensed section at the time of maximum transgression, which was followed by the beginning of a regression and basin shallowing. The overall basin history and geometry of the northwestern Cuyama basin are typical of strike-slip basins. The initial rapid subsidence to bathyal depths at rates of more than 500 m/m.y. in the early Miocene is interpreted to be a result of extension at the releasing bend of a dextral strike-slip fault. ?? 1990.

  14. C4 expansion in the central Inner Mongolia during the latest Miocene and early Pliocene

    NASA Astrophysics Data System (ADS)

    Zhang, Chunfu; Wang, Yang; Deng, Tao; Wang, Xiaoming; Biasatti, Dana; Xu, Yingfeng; Li, Qiang

    2009-10-01

    The emergence of C4 photosynthesis in plants as a significant component of terrestrial ecosystems is thought to be an adaptive response to changes in atmospheric CO 2 concentration and/or climate during Neogene times and has had a profound effect on the global terrestrial biosphere. Although expansion of C4 grasses in the latest Miocene and Pliocene has been widely documented around the world, the spatial and temporal variations in the C4 expansion are still not well understood and its driving mechanisms remain a contentious issue. Here we present the results of carbon and oxygen isotope analyses of fossil and modern mammalian tooth enamel samples from the central Inner Mongolia. Our samples represent a diverse group of herbivorous mammals including deer, elephants, rhinos, horses and giraffes, ranging in age from the late Oligocene to modern. The δ13C values of 91 tooth enamel samples of early late-Miocene age or older, with the exception of two 13 Ma rhino samples (- 7.8 and - 7.6‰) and one 8.5 Ma suspected rhino sample (- 7.6‰), were all less than - 8.0‰ (VPDB), indicating that there were no C4 grasses present in their diets and thus probably few or no C4 grasses in the ecosystems of the central Inner Mongolia prior to ~ 8 Ma. However, 12 out of 26 tooth enamel samples of younger ages (~ 7.5 Ma to ~ 3.9 Ma) have δ13C values higher than - 8.0‰ (up to - 2.4‰), indicating that herbivores in the area had variable diets ranging from pure C3 to mixed C3-C4 vegetation during that time interval. The presence of C4 grasses in herbivores' diets (up to ~ 76% C4) suggests that C4 grasses were a significant component of the local ecosystems in the latest Miocene and early Pliocene, consistent with the hypothesis of a global factor as the driving mechanism of the late Miocene C4 expansion. Today, C3 grasses dominate grasslands in the central Inner Mongolia area. The retreat of C4 grasses from this area after the early Pliocene may have been driven by regional climate change associated with tectonic processes in central Asia as well as global climate change.

  15. Ethanol extract of Zhongtian hawthorn lowers serum cholesterol in mice by inhibiting transcription of 3-hydroxy-3-methylglutaryl-CoA reductase via nuclear factor-kappa B signal pathway.

    PubMed

    Hu, Hai-Jie; Luo, Xue-Gang; Dong, Qing-Qing; Mu, Ai; Shi, Guo-Long; Wang, Qiu-Tong; Chen, Xiao-Ying; Zhou, Hao; Zhang, Tong-Cun; Pan, Li-Wen

    2016-03-01

    Hawthorn is a berry-like fruit from the species of Crataegus. In China, it has another more famous name, Shan-Zha, which has been used to improve digestion as a traditional Chinese medicine or food for thousands of years. Moreover, during the last decades, hawthorn has received more attention because of its potential to treat cardiovascular diseases. However, currently, only fruits of C. pinnatifida and C. pinnatifida var. major are included as Shan-Zha in the Chinese Pharmacopoeia. In this study, our results showed that the ethanol extract of Zhongtian hawthorn, a novel grafted cultivar of C. cuneata (wild Shan-Zha), could markedly reduce body weight and levels of serum total cholesterol, triglyceride, low-density lipoprotein cholesterol, and liver cholesterol of hyperlipidemia mice. It could suppress the stimulation effect of high-fat diet on the transcription of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and p65, and counteract the downregulation of CYP7A1 and LDLR. In addition, the results of luciferase reporter assay and Western blot showed that the transcriptional activity of HMGCR promoter was inhibited by Zhongtian hawthorn ethanol extract in a dose-dependent manner, while overexpression of p65 could reverse this transcriptional repression effect. These results suggested that Zhongtian hawthorn could provide health benefits by counteracting the high-fat diet-induced hypercholesteolemic and hyperlipidemic effects in vivo, and the mechanism underlying this event was mainly dependent on the suppressive effect of Zhongtian hawthorn ethanol extract on the transcription of HMGCR via nuclear factor-kappa B (NF-κB) signal pathway. Therefore, this novel cultivar of hawthorn cultivar which has much bigger fruits, early bearing, high yield, cold resistance, and drought resistance, might be considered as a good alternative to Shan-Zha and has great value in the food and medicine industry. In addition, to our best knowledge, this is also the first report that the extract of Crataegus could suppress the transcription of HMGCR via NF-κB signal pathway. PMID:26825354

  16. Mid Miocene Terrestrial Ecosystems: Information from Mammalian Herbivore Communities.

    NASA Astrophysics Data System (ADS)

    Janis, C. M.; Damuth, J.; Theodor, J. M.

    2001-05-01

    In present day ecosystems the numbers and proportions of different kinds of ecologically distinct ungulates (hoofed mammals) provide an indicator of the nature of the vegetation in the habitat. Different vegetation types (such as forest, savanna, or grassland) are characteristically associated with different arrays of ungulates, with species exhibiting differences in diet, body size, and type of digestive fermentation system. These biological attributes can also be inferred for fossil ungulate species, the first two from quantitative assessment of skull and dental anatomy, and the last from phylogenetic affinity. Thus fossil ungulate communities may be used as indicators of the vegetation types of the habitats in which they lived. Vegetation types, in turn, are determined largely by a number of physical environmental factors. Typical ungulate communities of the late early to early middle Miocene (17 - 15 Ma) from the Great Plains of North America contained a diversity of browsing (leaf-eating) and grazing (grass-eating) species, with proportions of dietary types and a diversity of body sizes indicative of a woodland savanna habitat. Paleobotanical evidence also indicates a woodland savanna type of vegetation. However, these communities included a much larger number of ungulate species than can be found in any present-day community. The "excess" ungulate species were primarily browsers. Throughout the rest of the middle Miocene both species numbers and the proportion of browsers in ungulate communities appear to have declined steadily. During this decline in browser species the numbers of grazer species remained relatively constant. Within-community species numbers comparable to the present day were attained by the late Miocene. We suggest that the early Miocene browser-rich communities, and their subsequent decline, carry an important paleoenvironmental signal. In particular, communities "over rich" in browsers may reflect higher levels of primary productivity in mid Miocene vegetation types in comparison with corresponding, structurally equivalent present-day vegetation types. The observed decline in species numbers may represent a gradual decline in terrestrial primary productivity, which would be consistent with one current hypothesis of a mid-Miocene decrease in atmospheric carbon dioxide concentrations from higher mid-Cenozoic values.

  17. First Hominoid from the Late Miocene of the Irrawaddy Formation (Myanmar)

    PubMed Central

    Jaeger, Jean-Jacques; Naing Soe, Aung; Chavasseau, Olivier; Coster, Pauline; Emonet, Edouard-Georges; Guy, Franck; Lebrun, Renaud; Maung, Aye; Aung Khyaw, Aung; Shwe, Hla; Thura Tun, Soe; Linn Oo, Kyaw; Rugbumrung, Mana; Bocherens, Hervé; Benammi, Mouloud; Chaivanich, Kamol; Tafforeau, Paul; Chaimanee, Yaowalak

    2011-01-01

    For over a century, a Neogene fossil mammal fauna has been known in the Irrawaddy Formation in central Myanmar. Unfortunately, the lack of accurately located fossiliferous sites and the absence of hominoid fossils have impeded paleontological studies. Here we describe the first hominoid found in Myanmar together with a Hipparion (s.l.) associated mammal fauna from Irrawaddy Formation deposits dated between 10.4 and 8.8 Ma by biochronology and magnetostratigraphy. This hominoid documents a new species of Khoratpithecus, increasing thereby the Miocene diversity of southern Asian hominoids. The composition of the associated fauna as well as stable isotope data on Hipparion (s.l.) indicate that it inhabited an evergreen forest in a C3-plant environment. Our results enlighten that late Miocene hominoids were more regionally diversified than other large mammals, pointing towards regionally-bounded evolution of the representatives of this group in Southeast Asia. The Irrawaddy Formation, with its extensive outcrops and long temporal range, has a great potential for improving our knowledge of hominoid evolution in Asia. PMID:21533131

  18. First hominoid from the Late Miocene of the Irrawaddy Formation (Myanmar).

    PubMed

    Jaeger, Jean-Jacques; Soe, Aung Naing; Chavasseau, Olivier; Coster, Pauline; Emonet, Edouard-Georges; Guy, Franck; Lebrun, Renaud; Maung, Aye; Aung Khyaw, Aung; Shwe, Hla; Thura Tun, Soe; Linn Oo, Kyaw; Rugbumrung, Mana; Bocherens, Herv; Benammi, Mouloud; Chaivanich, Kamol; Tafforeau, Paul; Chaimanee, Yaowalak

    2011-01-01

    For over a century, a Neogene fossil mammal fauna has been known in the Irrawaddy Formation in central Myanmar. Unfortunately, the lack of accurately located fossiliferous sites and the absence of hominoid fossils have impeded paleontological studies. Here we describe the first hominoid found in Myanmar together with a Hipparion (s.l.) associated mammal fauna from Irrawaddy Formation deposits dated between 10.4 and 8.8 Ma by biochronology and magnetostratigraphy. This hominoid documents a new species of Khoratpithecus, increasing thereby the Miocene diversity of southern Asian hominoids. The composition of the associated fauna as well as stable isotope data on Hipparion (s.l.) indicate that it inhabited an evergreen forest in a C3-plant environment. Our results enlighten that late Miocene hominoids were more regionally diversified than other large mammals, pointing towards regionally-bounded evolution of the representatives of this group in Southeast Asia. The Irrawaddy Formation, with its extensive outcrops and long temporal range, has a great potential for improving our knowledge of hominoid evolution in Asia. PMID:21533131

  19. Miocene characid fishes from Colombia: evolutionary stasis and extirpation.

    PubMed

    Lundberg, J G; Machado-Allison, A; Kay, R F

    1986-10-10

    Fossil fishes from the Miocene La Venta fauna of the Magdalena River Valley, Colombia, are identified as Colossoma macropomum (Characidae), a living species from the Orinoco and Amazon basins. The fossils document a long and conservative history for a species that is highly specialized for feeding on streamside plants. The phylogenetically advanced position of Colossoma in the subfamily Serrasalminae implies that six related genera and other higher characid taxa originated well before 15 million years ago. This discovery also corroborates neontological evidence for a vicariance event that contributed species from Miocene Orinoco-Amazon faunas to the original Magdalena region fauna. The fossils suggest a formerly diverse Magdalena fauna that has suffered local extinction, perhaps associated with late Cenozoic tectonism. This new evidence may help explain the depauperate nature of the modern Magdalena River. PMID:17746480

  20. Upper Miocene reef complex of Mallorca, Balearic Islands, Spain

    SciTech Connect

    Pomar, L.

    1988-02-01

    The late Tortonian-Messinian coral reef platform of south Mallorca onlaps a folded middle late Miocene carbonate platform on which progradation of up to 20 km occurs. Vertical sea cliffs (up to 100 m high) superbly show the last 5 km of this progradation and complement the numerous water-well cores from the island interior. The Mallorca reef presents the most complete facies zonation of the Miocene reefs of the western Mediterranean. The reef wall framework is up to 20 m thick and shows (1) erosional reef flat with reef breccia and small corals; (2) spur-and-grove zone with large, massive corals; (3) deep buttresses and pinnacles with terraces of branching corals; and (4) deep reef wall with flat, laminar coral colonies, branching red algae, and Halimeda sands.

  1. Across the Pacific: Climate Evolution in the Middle Miocene

    NASA Astrophysics Data System (ADS)

    Fox, L. R.; Wade, B.; Holbourn, A. E.; Leng, M. J.

    2013-12-01

    We present the first high-resolution (3 kyr) astronomically-tuned record of δ18O and δ13C from planktonic foraminifera for the equatorial Pacific Ocean (16.5-13.5 Myr). Our data provides exciting new information on sea surface temperatures and primary productivity changes at the tropics during the middle Miocene at a resolution not achieved in any previous study, which sheds new light on the middle Miocene climatic transition (MMCT) and associated carbon-isotope excursion. Reliable sea surface temperature estimates are crucial to any reconstruction and modelling of past ocean salinity and density, water column stratification, thermohaline circulation, and ice volume. Despite extensive studies of benthic foraminifera, existing planktonic foraminiferal records of this interval are extremely scarce and of low resolution, with samples representing time intervals of 2x105 and 5x105 years. Previous studies have been hindered by the absence of biogenic carbonate (e.g., Leg 199). Consequently the impact of global warming and cooling on tropical surface waters and the propagation of orbital cycles in the Earth System are unknown. In 2009 Integrated Ocean Drilling Program Expedition 320/321 recovered lower-middle Miocene sediments with high sedimentation rates (30m/myr), continuous recovery, and orbital cyclicity from the east equatorial Pacific Ocean. At Site U1338 planktonic foraminifera are abundant and diverse in the lower and middle Miocene sediments and exceptionally well preserved. Scanning electron microscope studies revealed open pore spaces, little evidence of calcitic overgrowth on the wall surface and in many cases preserved spines (Fox and Wade, in press). We compare our data from Site U1338 to Site 1146 in the western equatorial Pacific Ocean, to reconstruct bottom and surface water conditions and changes in ocean dynamics across the equatorial Pacific during this highly complex interval of climate history.

  2. Across the Pacific: Climate Evolution in the Middle Miocene

    NASA Astrophysics Data System (ADS)

    Fox, Lyndsey; Wade, Bridget; Holbourn, Ann; Leng, Melanie

    2014-05-01

    We present the first high-resolution (3 kyr) astronomically-tuned record of δ18O and δ13C from planktonic foraminifera for the equatorial Pacific Ocean (16.5-13.5 Myr). Our data provides exciting new information on sea surface temperatures and primary productivity changes at the tropics during the middle Miocene at a resolution not achieved in any previous study, which sheds new light on the middle Miocene climatic transition (MMCT) and associated carbon-isotope excursion. Reliable sea surface temperature estimates are crucial to any reconstruction and modelling of past ocean salinity and density, water column stratification, thermohaline circulation, and ice volume. Despite extensive studies of benthic foraminifera, existing planktonic foraminiferal records of this interval are extremely scarce and of low resolution, with samples representing time intervals of 2x105and 5x105 years. Previous studies have been hindered by the absence of biogenic carbonate (e.g., Leg 199). Consequently the impact of global warming and cooling on tropical surface waters and the propagation of orbital cycles in the Earth System are unknown. In 2009 Integrated Ocean Drilling Program Expedition 320/321 recovered lower-middle Miocene sediments with high sedimentation rates (30m/myr), continuous recovery, and orbital cyclicity from the east equatorial Pacific Ocean. At Site U1338 planktonic foraminifera are abundant and diverse in the lower and middle Miocene sediments and exceptionally well preserved. Scanning electron microscope studies revealed open pore spaces, little evidence of calcitic overgrowth on the wall surface and in many cases preserved spines (Fox and Wade, 2013). We compare our data from Site U1338 to Site 1146 in the western equatorial Pacific Ocean, to reconstruct bottom and surface water conditions and changes in ocean dynamics across the equatorial Pacific during this highly complex interval of climate history.

  3. A study of uranium favorability of Cenozoic sedimentary rocks, Basin and Range Province, Arizona: Part I, General geology and chronology of pre-late Miocene Cenozoic sedimentary rocks

    USGS Publications Warehouse

    Scarborough, Robert Bryan; Wilt, Jan Carol

    1979-01-01

    This study focuses attention on Cenozoic sedimentary rocks in the Basin and Range Province of Arizona. The known occurrences of uranium and anomalous radioactivity in these rocks are associated with sediments that accumulated in a low energy environment characterized by fine-grained clastics, including important tuffaceous materials, and carbonate rocks. Most uranium occurrences, in these rocks appear to be stratabound. Emphasis was placed on those sedimentary materials that pre-date the late Cenozoic Basin and Range disturbance. They are deformed and crop out on pedimented range blocks and along the province interface with the Transition Zone. Three tentative age groups are recognized: Group I - Oligocene, pre-22 m.y., Group II - early Miocene - 22 m.y. - 16 m.y., and Group III - middle Miocene - 16 m.y. to 13--10 m.y. Regionally, these three groups contain both coarse to fine-grained red clastics and low energy lighter colored 'lacustrine' phases. Each of the three groups has been the object of uranium exploration. Group II, the early Miocene strata, embraces the Anderson Mine - Artillery region host rocks and also the New River - Cave Creek early Miocene beds-along the boundary with the Transition Zone. These three groups of rocks have been tectonically deformed to the extent that original basins of deposition cannot yet be reconstructed. However, they were considerably more extensive in size than the late Cenozoic basins the origin of which deformed the former. Group II rocks are judged to be of prime interest because of: (1) the development and preservation of organic matter in varying lithologies, (2) apparent contemporaneity with silicic volcanic centers, (3) influence of Precambrian crystalline rocks, and (4) relative outcrop continuity near the stable Transition Zone. The Transition Zone, especially along its boundary with the Basin and Range Province, needs additional geologic investigation, especially as regards the depositional continuity of Group II sediment s.

  4. Early Miocene elevation in northern Tibet estimated by palaeobotanical evidence

    PubMed Central

    Sun, Bin; Wang, Yu-Fei; Li, Cheng-Sen; Yang, Jian; Li, Jin-Feng; Li, Ye-Liang; Deng, Tao; Wang, Shi-Qi; Zhao, Min; Spicer, Robert A.; Ferguson, David K.; Mehrotra, Rakesh C.

    2015-01-01

    The area and elevation of the Tibetan Plateau over time has directly affected Asia’s topography, the characteristics of the Asian monsoon, and modified global climate, but in ways that are poorly understood. Charting the uplift history is crucial for understanding the mechanisms that link elevation and climate irrespective of time and place. While some palaeoelevation data are available for southern and central Tibet, clues to the uplift history of northern Tibet remain sparse and largely circumstantial. Leaf fossils are extremely rare in Tibet but here we report a newly discovered early Miocene barberry (Berberis) from Wudaoliang in the Hoh-Xil Basin in northern Tibet, at a present altitude of 4611 ± 9 m. Considering the fossil and its nearest living species probably occupied a similar or identical environmental niche, the palaeoelevation of the fossil locality, corrected for Miocene global temperature difference, is estimated to have been between 1395 and 2931 m, which means this basin has been uplifted ~2–3 km in the last 17 million years. Our findings contradict hypotheses that suggest northern Tibet had reached or exceeded its present elevation prior to the Miocene. PMID:25976244

  5. Pre-transform early Miocene extension in western California

    SciTech Connect

    Tennyson, M.E. )

    1989-09-01

    Earliest Miocene (20-24 Ma) faulting and volcanism were widespread in western California, including the San Joaquin-La Honda basin, Coast Ranges, and Transverse Ranges. Evidence for strike slip on faults of this age is lacing. Their arrangement on a pre-San Andreas restoration suggest continuity with early Miocene extended terranes in eastern California and southwestern Arizona. Deformation was probably not an effect of transform or triple-junction-migration tectonics, because it was synchronous over 300 km of latitude and there is no direct evidence for a transform boundary until late in early Miocene time. Magnetic anomalies in the eastern Pacific permit an interpretation that a spreading ridge supplied a still-active subduction zone with young oceanic crust until sometime after 20 Ma. If so, extension evidently took place in an arc-related setting. A transform regime probably formed about 18 Ma, when most basins underwent episodes of deepening or uplift, strike-slip faults became active, and rotation of the western Transverse Ranges block began.

  6. Early Miocene elevation in northern Tibet estimated by palaeobotanical evidence.

    PubMed

    Sun, Bin; Wang, Yu-Fei; Li, Cheng-Sen; Yang, Jian; Li, Jin-Feng; Li, Ye-Liang; Deng, Tao; Wang, Shi-Qi; Zhao, Min; Spicer, Robert A; Ferguson, David K; Mehrotra, Rakesh C

    2015-01-01

    The area and elevation of the Tibetan Plateau over time has directly affected Asia's topography, the characteristics of the Asian monsoon, and modified global climate, but in ways that are poorly understood. Charting the uplift history is crucial for understanding the mechanisms that link elevation and climate irrespective of time and place. While some palaeoelevation data are available for southern and central Tibet, clues to the uplift history of northern Tibet remain sparse and largely circumstantial. Leaf fossils are extremely rare in Tibet but here we report a newly discovered early Miocene barberry (Berberis) from Wudaoliang in the Hoh-Xil Basin in northern Tibet, at a present altitude of 4611??9?m. Considering the fossil and its nearest living species probably occupied a similar or identical environmental niche, the palaeoelevation of the fossil locality, corrected for Miocene global temperature difference, is estimated to have been between 1395 and 2931?m, which means this basin has been uplifted ~2-3?km in the last 17 million years. Our findings contradict hypotheses that suggest northern Tibet had reached or exceeded its present elevation prior to the Miocene. PMID:25976244

  7. Miocene Oaks from Eastern Zhejiang, China and their Paleoenvironmental Significance

    NASA Astrophysics Data System (ADS)

    Jia, Hui; Ferguson, David

    2015-04-01

    The intertrappean fluvial-lacustrine beds belonging to the Upper Miocene Shengxian Formation in eastern China contain many exquisitely preserved plant fossils, e.g., leaves, fruits and seeds as well as plentiful pollen. The Fagaceae is the dominant taxon represented by 5 genera and 15 species, four of which belong to Quercus subgenus Cyclobalanopsis. Quercus species (oaks) are highly sensitive to environmental changes. The correlation between climate and trichome base density of Quercus glauca and Quercus delavayi of subg. Cyclobalanopsis, which are the NLRs of two fossil species, Quercus paraglauca and Quercus aff. delavayi, indicates that the trichome base density of Quercus glauca is comprehensively affected by various climate factors, but most influenced by solar radiation and latitude. The trichome base parametrics of Quercus paraglauca and the comparison of epidermal cell characteristics between Quercus paraglauca and Quercus aff. delavayi and their NLR species of subg. Cyclobalanopsis, show that the climate was warmer and more humid in the late Miocene than that of today in eastern Zhejiang, China. A study of the stomatal index of Quercus glauca and Quercus delavayi, collected in different years, demonstrates that they are very sensitive to the variation of atmospheric CO2 concentration. By comparing the stomatal ratio between the two fossil species and their NLRs, the paleoatmospheric CO2 concentration in the late Miocene is reconstructed as ca. 400 ppmv, i.e. higher than the present natural CO2 concentration eliminating the industrial influence.

  8. Miocene reef platforms from northwestern Tuamotu Islands, central Pacific

    SciTech Connect

    Montaggioni, L.F.; Mnhn-Ephe, A.

    1988-02-01

    Reef deposits of Miocene age occur on several northwestern Tuamotu atolls as either pointed residual and scattered reliefs through the Holocene reef sequence (Mataiva, Rangiroa, Tikehau, Kaukura) or elevated atoll-shaped platforms (Makatea). Throughout the region considered, the depositional/diagenetic history of Miocene reefs can be reconstructed as follows. During early Miocene times (e-f range-biozones), reef platforms developed on top of older carbonate banks, capping a midplate volcanic ridge of early Tertiary age. More than 100 m thick, these platforms displayed concentrically zoned environments of deposition: a peripheral subemergent rim composed of coralgalforaminiferal boundstones, and a very shallow central area in which foraminiferal and molluscan fine sands and muds were subhorizontally deposited. Local evidence of internal unconformity surfaces and subaerially produced features indicates that periods of relative emergency occurred as the reef piles grew upward. The ultimate stage of platform development is believed to have been a complete upfilling of the back-reef areas and subsequent emergence. Correlatively, a freshwater lens would have been formed close to the surface level of each of the so-formed islands. Dolomitization may have been initiated in the marine water/freshwater phreatic mixing zone. During lowstands, severe meteoric alteration affected emergent carbonate deposits, forming incipient cavity systems; the usual atoll morphology is considered to have been initiated at this time (presumably middle Micoene).

  9. Ostracods (Crustacea) and their palaeoenvironmental implication for the Solimões Formation (Late Miocene; Western Amazonia/Brazil)

    PubMed Central

    Gross, Martin; Ramos, Maria Ines; Caporaletti, Marco; Piller, Werner E.

    2013-01-01

    Western Amazonia's landscape and biota were shaped by an enormous wetland during the Miocene epoch. Among the most discussed topics of this ecosystem range the question on the transitory influx of marine waters. Inter alia the occurrence of typically brackish water associated ostracods is repeatedly consulted to infer elevated salinities or even marine ingressions. The taxonomical investigation of ostracod faunas derived from the upper part of the Solimões Formation (Eirunepé; W-Brazil) documents a moderately diverse assemblage (19 species). A wealth of freshwater ostracods (mainly Cytheridella, Penthesilenula) was found co-occurring with taxa (chiefly Cyprideis) usually related to marginal marine settings today. The observed faunal compositions as well as constantly very light δ18O- and δ13C-values obtained by measuring both, the freshwater and brackish water ostracod group, refer to entirely freshwater conditions. These results corroborate with previous sedimentological and palaeontological observations, which proposed a fluvial depositional system for this part of western Amazonia during the Late Miocene. We demonstrate that some endemic, “brackish” water ostracods (i.e., Cyprideis) have been effectively adapted to freshwater conditions. Thus, their occurrence is no univocal evidence for the influence of brackish or marine waters in western Amazonia during the Miocene. PMID:26523090

  10. A near-infrared reflectance spectroscopy method for direct analysis of several chemical components and properties of fruit, for example, Chinese hawthorn.

    PubMed

    Dong, Wenjiang; Ni, Yongnian; Kokot, Serge

    2013-01-23

    Near-infrared spectroscopy (NIRS) calibrations were developed for the discrimination of Chinese hawthorn (Crataegus pinnatifida Bge. var. major) fruit from three geographical regions as well as for the estimation of the total sugar, total acid, total phenolic content, and total antioxidant activity. Principal component analysis (PCA) was used for the discrimination of the fruit on the basis of their geographical origin. Three pattern recognition methods, linear discriminant analysis, partial least-squares-discriminant analysis, and back-propagation artificial neural networks, were applied to classify and compare these samples. Furthermore, three multivariate calibration models based on the first derivative NIR spectroscopy, partial least-squares regression, back-propagation artificial neural networks, and least-squares-support vector machines, were constructed for quantitative analysis of the four analytes, total sugar, total acid, total phenolic content, and total antioxidant activity, and validated by prediction data sets. PMID:23265446

  11. Miocene Global Carbon Isotope Shifts and Marine Biological Productivity.

    NASA Astrophysics Data System (ADS)

    Diester-Haass, L.; Billups, K.

    2005-12-01

    The Miocene contains two major global carbon isotope shifts: a negative shift during the late Miocene (~8-6 Ma) and a positive shift during the mid-Miocene (16-14 Ma). We aim at deciphering possible changes in marine biological export productivity during these shifts by calculating paleoproductivity in gC/cm*ky from benthic foraminiferal numbers and accumulation rates at a number of sites spanning the world oceans. Our previous work has illustrated that the onset of the late Miocene negative d 13C shift, which has been attributed to enhanced erosion of terrestrial biomass and expansion of C4 plants, is also accompanied by an increase in marine export productivity from lower than present day values up to 2-3 times modern values at six sites (982, 1088, 721, 846, 1146, 1172; Diester-Haass et al, in press; Diester-Haass et al., in preparation). The Mid-Miocene 'Monterey Event', on the other hand, has been attributed to sequestration of organic material in circum-Pacific basins (Vincent and Berger, 1985) or wide spread deposition of brown coal and drowning of carbonate platforms (Fllmi et al., 2005) . For this particular time interval, our initial results from Site 608 (Atlantic Ocean) reveal relatively constant paleoproductivity values similar to modern ones ( about 10 gC/cm*ky) until 16.5 Ma, after which time paleoproductivity begins to increase until the end of our record at 11 Ma. Superimposed on the trend of generally increasing productivity, there are a number of productivity minima spaced roughly 0.5 million years apart. The long term trend in the paleoproductivity finds some similarities in the global composite benthic foraminiferal d 13C record as both proxies show an overall increase until ~14 Ma. Thereafter, however, paleoproductivity continues to increase while d 13C values decrease marking the end of the Monterey excursion. Stable isotope analyses from these same intervals will show to what extend the smaller scale fluctuations in paleoproductivity can be related to changes in the d13C of the oceanic reservoir or regional water masses. Diester-Haass, L., Billups, K., Emeis, K-C., 2005, Paleoceanography, in press. Vincent, E. and Berger, W., 1985, In: The carbon cycle and atmospheric CO2: Natural variations Archaen to present, edited by Sunquist, E.T. and Broecker, W.S., Am.Geophys. Union Monogr. 32,455-468 Fllmi, K.B. et al., 2005, Geol.Soc.Am.Bull., 117/5, 589-619.

  12. Transitional directions from Early Miocene Lavas at Samothraki Island, N. Greece

    NASA Astrophysics Data System (ADS)

    Kondopoulou, Despina; Valet, Jean-Pierre; Zananiri, Irene; Voidomatis, Philippos

    2014-05-01

    The North Hellenic orogen was formed at the expenses of the Variscan and Jurassic oceanic crust, preserved in scattered ophiolitic massifs. Strong post-orogenic extension with coeval emplacement of granodioritic plutons, deposition of clastic sediments and calc-alkaline volcanism appeared from the Middle-Late Eocene to the Middle Miocene. These widespread Tertiary volcanic products, outcropping also in north and central Aegean, have been extensively studied as far as their emplacement conditions are concerned. In parallel, they have been the object of several palaeomagnetic studies, all consistently indicating a general pattern of clockwise rotations. The island of Samothraki belongs to the Circum-Rhodope Zone, a series of Triassic-Jurassic continental margin sedimentary and volcanic rocks that surround the crystalline Serbo-Macedonian and Rhodope Massifs. The geochronological data, along with the morphology and the eruption mode of the Samothraki Tertiary volcanic rocks, allow a division into three groups, namely the "old", the "intermediate" and the "young" ones. Several radiometric ages have been assigned to the three groups, spanning from 25 to 19 Ma. Isotope and trace-element modeling do not favor a continuous evolution of these magmas. The major granitic and volcanic formations of the island have been subjected to paleomagnetic studies. The results revealed a complex pattern with coexisting straightforward directions and puzzling ones, only within the younger lavas, mostly domes. These samples are characterized by a medium temperature component with an eastward declination and a positive inclination and a high temperature one with a negative inclination. Experiments of absolute paleointensity have been conducted on twenty-eight samples from 3 separate domes with ages between 22-19 Ma using a modified Thellier technique with very narrow 4°C to 10°C temperature steps between 500°C and 595°C. The results indicate significantly low field values at two sites. The presence of low paleointensities combined with intermediate directions suggest that they recorded a transitional field state. Interestingly, similar directions were obtained in miocene volcanics from the nearby island of Lemnos as well as from the mainland Thrace area. A further study of these formations will hopefully improve our knowledge of the field behavior in Early Miocene.

  13. Decrease in coccolithophore calcification and CO2 since the middle Miocene

    NASA Astrophysics Data System (ADS)

    Bolton, Clara T.; Hernández-Sánchez, María T.; Fuertes, Miguel-Ángel; González-Lemos, Saúl; Abrevaya, Lorena; Mendez-Vicente, Ana; Flores, José-Abel; Probert, Ian; Giosan, Liviu; Johnson, Joel; Stoll, Heather M.

    2016-01-01

    Marine algae are instrumental in carbon cycling and atmospheric carbon dioxide (CO2) regulation. One group, coccolithophores, uses carbon to photosynthesize and to calcify, covering their cells with chalk platelets (coccoliths). How ocean acidification influences coccolithophore calcification is strongly debated, and the effects of carbonate chemistry changes in the geological past are poorly understood. This paper relates degree of coccolith calcification to cellular calcification, and presents the first records of size-normalized coccolith thickness spanning the last 14 Myr from tropical oceans. Degree of calcification was highest in the low-pH, high-CO2 Miocene ocean, but decreased significantly between 6 and 4 Myr ago. Based on this and concurrent trends in a new alkenone εp record, we propose that decreasing CO2 partly drove the observed trend via reduced cellular bicarbonate allocation to calcification. This trend reversed in the late Pleistocene despite low CO2, suggesting an additional regulator of calcification such as alkalinity.

  14. The genus Macroteleia Westwood in Middle Miocene amber from Peru (Hymenoptera, Platygastridae s.l., Scelioninae)

    PubMed Central

    Perrichot, Vincent; Antoine, Pierre-Olivier; Salas-Gismondi, Rodolfo; Flynn, John J.; Engel, Michael S.

    2014-01-01

    Abstract A new species of the scelionine genus Macroteleia Westwood (Platygastridae s.l., Scelioninae) is described and figured from a female beautifully preserved in Middle Miocene amber from Peru. Macroteleia yaguarum Perrichot & Engel, sp. n., shows a unique combination of characters otherwise seen independently within its congeners. It is most similar to the modern M. surfacei Brues, but differs from it by the non-foveolate notauli, the contiguous punctures of the vertex, and the continuous propodeum. The new species is the first New World fossil of the genus, suggesting a Cretaceous origin for the group and a relatively old age of the South American, tropical African, and Australian faunas, and a younger age of the modern Holarctic faunas. PMID:25147461

  15. The genus Macroteleia Westwood in Middle Miocene amber from Peru (Hymenoptera, Platygastridae s.l., Scelioninae).

    PubMed

    Perrichot, Vincent; Antoine, Pierre-Olivier; Salas-Gismondi, Rodolfo; Flynn, John J; Engel, Michael S

    2014-01-01

    A new species of the scelionine genus Macroteleia Westwood (Platygastridae s.l., Scelioninae) is described and figured from a female beautifully preserved in Middle Miocene amber from Peru. Macroteleia yaguarum Perrichot & Engel, sp. n., shows a unique combination of characters otherwise seen independently within its congeners. It is most similar to the modern M. surfacei Brues, but differs from it by the non-foveolate notauli, the contiguous punctures of the vertex, and the continuous propodeum. The new species is the first New World fossil of the genus, suggesting a Cretaceous origin for the group and a relatively old age of the South American, tropical African, and Australian faunas, and a younger age of the modern Holarctic faunas. PMID:25147461

  16. Decrease in coccolithophore calcification and CO2 since the middle Miocene

    PubMed Central

    Bolton, Clara T.; Hernández-Sánchez, María T.; Fuertes, Miguel-Ángel; González-Lemos, Saúl; Abrevaya, Lorena; Mendez-Vicente, Ana; Flores, José-Abel; Probert, Ian; Giosan, Liviu; Johnson, Joel; Stoll, Heather M.

    2016-01-01

    Marine algae are instrumental in carbon cycling and atmospheric carbon dioxide (CO2) regulation. One group, coccolithophores, uses carbon to photosynthesize and to calcify, covering their cells with chalk platelets (coccoliths). How ocean acidification influences coccolithophore calcification is strongly debated, and the effects of carbonate chemistry changes in the geological past are poorly understood. This paper relates degree of coccolith calcification to cellular calcification, and presents the first records of size-normalized coccolith thickness spanning the last 14 Myr from tropical oceans. Degree of calcification was highest in the low-pH, high-CO2 Miocene ocean, but decreased significantly between 6 and 4 Myr ago. Based on this and concurrent trends in a new alkenone ɛp record, we propose that decreasing CO2 partly drove the observed trend via reduced cellular bicarbonate allocation to calcification. This trend reversed in the late Pleistocene despite low CO2, suggesting an additional regulator of calcification such as alkalinity. PMID:26762469

  17. Decrease in coccolithophore calcification and CO2 since the middle Miocene.

    PubMed

    Bolton, Clara T; Hernández-Sánchez, María T; Fuertes, Miguel-Ángel; González-Lemos, Saúl; Abrevaya, Lorena; Mendez-Vicente, Ana; Flores, José-Abel; Probert, Ian; Giosan, Liviu; Johnson, Joel; Stoll, Heather M

    2016-01-01

    Marine algae are instrumental in carbon cycling and atmospheric carbon dioxide (CO2) regulation. One group, coccolithophores, uses carbon to photosynthesize and to calcify, covering their cells with chalk platelets (coccoliths). How ocean acidification influences coccolithophore calcification is strongly debated, and the effects of carbonate chemistry changes in the geological past are poorly understood. This paper relates degree of coccolith calcification to cellular calcification, and presents the first records of size-normalized coccolith thickness spanning the last 14 Myr from tropical oceans. Degree of calcification was highest in the low-pH, high-CO2 Miocene ocean, but decreased significantly between 6 and 4 Myr ago. Based on this and concurrent trends in a new alkenone ɛp record, we propose that decreasing CO2 partly drove the observed trend via reduced cellular bicarbonate allocation to calcification. This trend reversed in the late Pleistocene despite low CO2, suggesting an additional regulator of calcification such as alkalinity. PMID:26762469

  18. Life-History Traits of the Miocene Hipparion concudense (Spain) Inferred from Bone Histological Structure

    PubMed Central

    Martinez-Maza, Cayetana; Alberdi, Maria Teresa; Nieto-Diaz, Manuel; Prado, José Luis

    2014-01-01

    Histological analyses of fossil bones have provided clues on the growth patterns and life history traits of several extinct vertebrates that would be unavailable for classical morphological studies. We analyzed the bone histology of Hipparion to infer features of its life history traits and growth pattern. Microscope analysis of thin sections of a large sample of humeri, femora, tibiae and metapodials of Hipparion concudense from the upper Miocene site of Los Valles de Fuentidueña (Segovia, Spain) has shown that the number of growth marks is similar among the different limb bones, suggesting that equivalent skeletochronological inferences for this Hipparion population might be achieved by means of any of the elements studied. Considering their abundance, we conducted a skeletechronological study based on the large sample of third metapodials from Los Valles de Fuentidueña together with another large sample from the Upper Miocene locality of Concud (Teruel, Spain). The data obtained enabled us to distinguish four age groups in both samples and to determine that Hipparion concudense tended to reach skeletal maturity during its third year of life. Integration of bone microstructure and skeletochronological data allowed us to identify ontogenetic changes in bone structure and growth rate and to distinguish three histologic ontogenetic stages corresponding to immature, subadult and adult individuals. Data on secondary osteon density revealed an increase in bone remodeling throughout the ontogenetic stages and a lesser degree thereof in the Concud population, which indicates different biomechanical stresses in the two populations, likely due to environmental differences. Several individuals showed atypical growth patterns in the Concud sample, which may also reflect environmental differences between the two localities. Finally, classification of the specimens’ age within groups enabled us to characterize the age structure of both samples, which is typical of attritional assemblages. PMID:25098950

  19. Life-history traits of the Miocene Hipparion concudense (Spain) inferred from bone histological structure.

    PubMed

    Martinez-Maza, Cayetana; Alberdi, Maria Teresa; Nieto-Diaz, Manuel; Prado, Jos Luis

    2014-01-01

    Histological analyses of fossil bones have provided clues on the growth patterns and life history traits of several extinct vertebrates that would be unavailable for classical morphological studies. We analyzed the bone histology of Hipparion to infer features of its life history traits and growth pattern. Microscope analysis of thin sections of a large sample of humeri, femora, tibiae and metapodials of Hipparion concudense from the upper Miocene site of Los Valles de Fuentiduea (Segovia, Spain) has shown that the number of growth marks is similar among the different limb bones, suggesting that equivalent skeletochronological inferences for this Hipparion population might be achieved by means of any of the elements studied. Considering their abundance, we conducted a skeletechronological study based on the large sample of third metapodials from Los Valles de Fuentiduea together with another large sample from the Upper Miocene locality of Concud (Teruel, Spain). The data obtained enabled us to distinguish four age groups in both samples and to determine that Hipparion concudense tended to reach skeletal maturity during its third year of life. Integration of bone microstructure and skeletochronological data allowed us to identify ontogenetic changes in bone structure and growth rate and to distinguish three histologic ontogenetic stages corresponding to immature, subadult and adult individuals. Data on secondary osteon density revealed an increase in bone remodeling throughout the ontogenetic stages and a lesser degree thereof in the Concud population, which indicates different biomechanical stresses in the two populations, likely due to environmental differences. Several individuals showed atypical growth patterns in the Concud sample, which may also reflect environmental differences between the two localities. Finally, classification of the specimens' age within groups enabled us to characterize the age structure of both samples, which is typical of attritional assemblages. PMID:25098950

  20. Miocene Vetigastropoda and Neritimorpha (Mollusca, Gastropoda) of central Chile

    NASA Astrophysics Data System (ADS)

    Nielsen, Sven N.; Frassinetti, Daniel; Bandel, Klaus

    2004-09-01

    Species of Vetigastropoda (Fissurellidae, Turbinidae, Trochidae) and one species of Neritimorpha (Neritidae) from the Navidad area, south of Valpara?so, and the Arauco Peninsula, south of Concepcin, are described. Among these, the Fissurellidae comprise Diodora fragilis n. sp., Diodora pupuyana n. sp., two additional unnamed species of Diodora, and a species resembling Fissurellidea. Turbinidae are represented by Cantrainea sp., and Trochidae include Tegula (Chlorostoma) austropacifica n. sp., Tegula (Chlorostoma) chilena n. sp., Tegula (Chlorostoma) matanzensis n. sp., Tegula (Agathistoma) antiqua n. sp., Bathybembix mcleani n. sp., Gibbula poeppigii [Philippi, 1887] n. comb., Diloma miocenica n. sp., Fagnastesia venefica [Philippi, 1887] n. gen. n. comb., Fagnastesia matanzana n. gen. n. sp., Calliostoma mapucherum n. sp., Calliostoma kleppi n. sp., Calliostoma covacevichi n. sp., Astele laevis [Sowerby, 1846] n. comb., and Monilea riorapelensis n. sp. The Neritidae are represented by Nerita (Heminerita) chilensis [Philippi, 1887]. The new genus Fagnastesia is introduced to represent low-spired trochoideans with a sculpture of nodes below the suture, angulated whorls, and a wide umbilicus. This Miocene Chilean fauna includes genera that have lived at the coast and in shallow, relatively warm water or deeper, much cooler water. This composition therefore suggests that many of the Miocene formations along the central Chilean coast consist of displaced sediments. A comparison with different fossil and Recent faunas from around the Pacific and South America indicates that the vetigastropod and neritid fauna from the Miocene of Chile has only minor affinities with taxa living near New Zealand, Argentina, and the tropical eastern Pacific at that time.

  1. Middle Miocene closure of the Central American Seaway

    NASA Astrophysics Data System (ADS)

    Montes, C.; Cardona, A.

    2014-12-01

    The final closure of the Panama Isthmus and permanent separation of Caribbean and Pacific waters is thought to have modified their salinity, faunistic assemblages, and ultimately, ocean circulation patterns and global climate. The Great American Biotic Interchange (GABI) is thought to have been the result of Plio-Pleistocene closure of the Isthmus that allowed land animals to massively cross the Isthmus. Similarly, the separation of Caribbean and Pacific waters by a rising Isthmus is thougth to be a prime example of vicariance. The role of Isthmus closure on global changes, however, remains controversial due in part to the difficulty of establishing a precise chronology of seaway closure. While timing of glaciation is well established, new data on the chronology of Isthmus emergence suggests that the process of closure is more complex, long, and old than previously thought. We sampled fluvial and shallow marine strata in northwesternmost South America to recover zircon grains for provenance analyses in the immediate vicinity of the docking site. Because the ages of magmatic provinces in northwestern South America and the Panama Isthmus are mutually exclusive, detrital zircon analyses provides a tool to evaluate land connections. We found that an uniquely Panamanian, 40-45 Ma (early Lutetian) detrital zircon fingerprint is abundant in middle Miocene strata, but absent in underlying lower Miocene and Oligocene strata of the northern Andes. This fingerprint represents the beginning of fluvial detrital exchange between the Panama arc and South America, and therefore marks the time of docking and the end of deep-water, and probably shallow-water connections by middle Miocene times.

  2. Paleoceanographic implications of Miocene deep-sea hiatuses.

    USGS Publications Warehouse

    Keller, G.; Barron, J.A.

    1983-01-01

    Miocene paleoceanographic evolution exhibits major changes resulting from the opening and closing of passages, the subsequent changes in oceanic circulation, and development of major Antarctic glaciation. The consequences and timing of these events can be observed in variations in the distribution of deep-sea hiatuses, sedimentation patterns, and biogeographic distribution of planktic organisms. The main aspects of the present oceanic circulation system and sediment distribution pattern were established by 13.5 to 12.5 Ma (hiatus NH 3), coincident with the establishment of a major East Antarctic ice cap. -from Authors

  3. Miocene phosphate-rich sediments in Salento (southern Italy)

    NASA Astrophysics Data System (ADS)

    Föllmi, Karl B.; Hofmann, Hélène; Chiaradia, Massimo; de Kaenel, Eric; Frijia, Gianluca; Parente, Mariano

    2015-08-01

    The upper Middle to lower Upper Miocene (Serravallian to Tortonian) sedimentary succession in Salento (southern Italy) includes glauconite- and phosphate-rich deposits, which are associated with pelagic micrite. In Baia del Ciolo and Marittima (southern Salento), the succession is composed of shallow-water platform carbonates of Late Oligocene age (Chattian; Porto Badisco Formation), which are overlain by a 20- to 30-cm-thick level of glauconite-rich micrite with abundant reworked particles and fossils of the underlying Porto Badisco Formation. This interval is in turn covered by an up to 15 cm thick phosphatic crust ("Livello ad Aturia"), which itself is overlain either by a hemipelagic chalk-like carbonate of Middle to Late Miocene age ("Pietra Leccese"; Marittima) or directly by a micrite of Late Miocene age (Messinian; Novaglie Formation; Baia del Ciolo), which shallows upwards into a shallow-water platform carbonate. A large hiatus is present in this succession, which likely includes the Lower and lower Middle Miocene. In the region of Lecce, two discrete levels enriched in glauconite and phosphate-each associated with a major discontinuity-occur within the Pietra Leccese. The strontium-isotope ages derived on phosphate nodules and phosphatized and non-phosphatized fossils and calcareous nannofossil ages indicate a time interval of phosphogenesis between 13.5 and 7.5 Ma, with two clusters at 12 and 10.5 Ma. The glauconite and phosphate-rich sediments resulted from a current-dominated regime, which was characterized by low overall sedimentation rates, erosion and sediment reworking, and authigenesis. This regime was likely related to a generally westward-directed bottom current, which was forced to upwell once it arrived at the western border of the eastern Mediterranean basin. The timing of the principal phosphogenic phases can only partly be correlated to those of other occurrences in this part of the Mediterranean (Malta, Gozo, southern Sicily, Matese, Latium-Abruzzi platform). The partial diachrony in phosphogenesis may express the effect of lateral switching in and/or focusing of upwelling zones.

  4. The beaver Anchitheriomys from the Miocene of Central Europe

    SciTech Connect

    Stefen, C.; Mors, T.

    2008-09-15

    New finds of teeth and mandibles of Anchitheriomys from the Hambach opencast lignite mine in Northwest Germany and the first detailed descriptions of other mandibles from South Germany and Switzerland allow a review of the Central European specimens of this rare beaver genus. The metric variation of cheek teeth and especially the great differences in dimensions of incisors can be much better assessed. The observed range in size can be attributed to ontogenetic changes, and all material is assigned to Anchitheriomys suevicus. Stratigraphically, this species is restricted to the early middle Miocene, European Mammalian Neogene biozones MN 5-6.

  5. Miocene reef facies of pelagian block, central Mediterranean

    SciTech Connect

    Pedley, H.M.

    1988-02-01

    Miocene reefs outcrop in the Maltese Islands, southeastern Sicily, and the pelagian island of Lampedusa. Several rapid eustatic sea level fluctuations affected these late Tortonian-early Messinian build-ups; normal salinities appear to have been maintained during these events. In addition to sea floor topography, reef development appears to have been controlled by turbulence. Encruster-dominated patch reefs are typical of platform and shallow ramp situations where turbulence is high. Branching and massive coral assemblages are typical of fore-reef curtains and steep slope substrates.

  6. Miocene glaciomarine sediments from beneath the southern ross ice shelf, antarctica.

    PubMed

    Webb, P N; Ronan, T E; Lipps, J H; Delaca, T E

    1979-02-01

    Glaciomarine sediments with middle Miocene microfaunal assemblages are exposed at the sea floor below the southern Ross Ice Shelf. Plio-Pleistocene sediments are not present. Post-Miocene glacial sediments may have been deposited but removed by relatively recent ice shelf grounding. A meager Recent microfauna is present in some core tops. PMID:17734134

  7. Early Miocene sequence development across the New Jersey margin

    USGS Publications Warehouse

    Monteverde, D.H.; Mountain, Gregory S.; Miller, K.G.

    2008-01-01

    Sequence stratigraphy provides an understanding of the interplay between eustasy, sediment supply and accommodation in the sedimentary construction of passive margins. We used this approach to follow the early to middle Miocene growth of the New Jersey margin and analyse the connection between relative changes of sea level and variable sediment supply. Eleven candidate sequence boundaries were traced in high-resolution multi-channel seismic profiles across the inner margin and matched to geophysical log signatures and lithologic changes in ODP Leg 150X onshore coreholes. Chronologies at these drill sites were then used to assign ages to the intervening seismic sequences. We conclude that the regional and global correlation of early Miocene sequences suggests a dominant role of global sea-level change but margin progradation was controlled by localized sediment contribution and that local conditions played a large role in sequence formation and preservation. Lowstand deposits were regionally restricted and their locations point to both single and multiple sediment sources. The distribution of highstand deposits, by contrast, documents redistribution by along shelf currents. We find no evidence that sea level fell below the elevation of the clinoform rollover, and the existence of extensive lowstand deposits seaward of this inflection point indicates efficient cross-shelf sediment transport mechanisms despite the apparent lack of well-developed fluvial drainage. ?? 2008 The Authors. Journal compilation ?? 2008 Blackwell Publishing.

  8. Alkenone producers during late Oligocene-early Miocene revisited

    NASA Astrophysics Data System (ADS)

    Plancq, Julien; Grossi, Vincent; Henderiks, Jorijntje; Simon, Laurent; Mattioli, Emanuela

    2012-03-01

    This study investigates ancient alkenone producers among the late Oligocene-early Miocene coccolithophores recorded at Deep Sea Drilling Project (DSDP) Site 516. Contrary to common assumptions, Reticulofenestra was not the most important alkenone producer throughout the studied time interval. The comparison between coccolith species-specific absolute abundances and alkenone contents in the same sedimentary samples shows that Cyclicargolithus abundances explain 40% of the total variance of alkenone concentration and that the species Cyclicargolithus floridanus was a major alkenone producer, although other related taxa may have also contributed to the alkenone production at DSDP Site 516. The distribution of the different alkenone isomers (MeC37:2, EtC38:2, and MeC38:2) remained unchanged across distinct changes in species composition, suggesting similar diunsaturated alkenone compositions within the Noelaerhabdaceae family during the late Oligocene-early Miocene. However, the overall larger cell size of Cyclicargolithus may have implications for the alkenone-based reconstruction of past partial pressure of CO2. Our results underscore the importance of a careful evaluation of the most likely alkenone producers for periods (>1.85 Ma) predating the first occurrence of contemporary alkenone producers (i.e., Emiliania huxleyi and Gephyrocapsa oceanica).

  9. Miocene to Pliocene osmium isotopic records of Mediterranean sediments

    NASA Astrophysics Data System (ADS)

    Kuroda, Junichiro; Jiménez-Espejo, Francisco J.; Nozaki, Tatsuo; Gennari, Rocco; Lugli, Stefano; Manzi, Vinicio; Roveri, Marco; Flecker, Rachel; Suzuki, Katsuhiko; Yoshimura, Toshihiro; Sierro, Francisco; Ohkouchi, Naohiko

    2015-04-01

    In the late Miocene the Mediterranean Sea experienced a salinity crisis and thick sequences of evaporites precipitated across the basin. In this study we report Os isotopic records from drilled cores in the Mediterranean; the Balearic Sea, the Tyrrhenian Sea, the Ionian Basin and the Florence Rise. Pliocene sediments at all sites show 187Os/188Os values close to that of the coeval ocean water, indicating that the Mediterranean was connected to the North Atlantic. Evaporitic sediments deposited during the late Miocene however, have 187Os/188Os values lower than coeval ocean water values and samples from the eastern Mediterranean and Ionian basins are particularly low. Os isotopic ratios of the pre-evaporite sediments in the western Mediterranean are almost identical to that of the coeval ocean water. In contrast, equivalent sediments from the Florence Rise have significantly lower 187Os/188Os values. The offset of Mediterranean evaporite 187Os/188Os is attributed to limited exchange with the North Atlantic during the Messinian Salinity Crisis (MSC). The source of unradiogenic Os is likely to be weathering of ultramafic rocks (ophiolites) cropping out in the Mediterranean's drainage basins. The offset in the Os ratio on the Florence Rise is attributed either to limited water exchange between eastern and western Mediterranean, or to local effects associated with exhumation of ophiolites around the eastern Mediterranean Sea.

  10. Upper Miocene reef complex of Mallorca, Balearic Islands, Spain

    SciTech Connect

    Pomar, L.

    1988-01-01

    The late Tortonian-Messinian coral reef platform of south Mallorca onlaps a folded middle late Miocene carbonate platform on which progradation of up to 20 km occurs. Vertical sea cliffs (up to 100 m high) superbly show the last 5 km of this progradation and complement the numerous water-well cores from the island interior. The coral reef platform consists of a series of progradational-accretional sequences and erosion surfaces of different orders of magnitude. The first-order sequence is bounded by significant erosion surfaces with breccias, major facies shifts, and vertical accretion. The second-order sequences show accretional events of up to 100 m thick with 1 to 2 km of progradation, and the third-order sequences occur in packages of tens of meters. Individual reef units are bounded by minor erosional surfaces and define the fourth-order sequences. This composite accretional-progradational architecture implies cyclic variations of relative sea level. Episodes of sea level rise were responsible for the vertical accretion. Sea level falls produced the erosional surfaces; most progradation occurred during lowering sea level episodes. This sedimentological framework of the Mallorca reef suggests late Miocene glacio-eustatic fluctuations of sea level similar to the Quaternary.

  11. Miocene semidiurnal tidal rhythmites in Madre de Dios, Peru

    NASA Astrophysics Data System (ADS)

    Hovikoski, Jussi; Rsnen, Matti; Gingras, Murray; Roddaz, Martin; Brusset, Stphane; Hermoza, Wilber; Romero Pittman, Lidia; Lertola, Kalle

    2005-03-01

    New data from upper Miocene deposits in the Madre de Dios region, southern Peru, allow the delineation of tidal regime for the first time in western Amazonia and provide strong evidence of elevated tidal range and brackish-water influence. The results point out the insufficiency of the current depositional models and support the earlier hypothesis that western Amazonia was also connected to the Paranan Sea during the late Miocene. In this paper we present sedimentological, ichnological, and statistical (Fourier transformation) data from two selected outcrops containing rhythmite successions from an area that is traditionally considered as continental. The sediments are interpreted to represent tide-dominated, inner-middle estuarine deposits. The cyclic rhythmites display semidiurnal cyclicity. The results are significant because (1) they contradict recent interpretations of the area's paleoenvironmental history; (2) the evidence for tidal processes is persuasive; and (3) the delineated tidal regime and range provide a unique insight into the depositional dynamics of a system having many important paleogeographic implications.

  12. Plate-induced Miocene extension in southern California

    SciTech Connect

    Stuart, W.D. Univ. of California, Santa Barbara, CA )

    1992-01-01

    Miocene crustal extension in southern California can be explained by the interaction of tectonic plates in relative motion. The Pacific, Juan de Fuca, and Farallon (Guadalupe) plates are represented by flat elastic plates surrounded by an infinite elastic plate, the eastern part of which represents the North America plate. Forcing is by assigned subduction pull, and tractions at all plate boundaries satisfy a viscous constitutive law. Plate bottoms are stress-free. In the first part of the solution plate velocities and boundary tractions are found from static equilibrium. Then principal horizontal stresses and strains in plate interiors caused by tractions and subduction pull are found by a boundary element procedure. Using plate boundary geometry from Stock and Hodges for early- and mid-Miocene times, it is found that the portion of the North America plate margin between the Mendocino and Rivera triple junctions has maximum extensional strain directed westward. This result is generally consistent with directions associated with metamorphic core complex formation in southern California. The model is also consistent with extensional strain and rotation sense of crustal blocks in the vicinity of Los Angeles, as inferred by Luyendyk and others from paleomagnetic data. In the model the greatest extensional strain of the North America plate occurs near the Pacific-North America transform, in the area above the absent Farallon slab. Extension direction varies from northwest to southwest according to plate geometry, subduction pull (Juan de Fuca and Guadalupe), and plate boundary tractions.

  13. Composition and provenance of the Puente Formation (Miocene), Los Angeles Basin

    SciTech Connect

    Critelli, S. ); Rumelhart, P.E.; Ingersoll, R.V. )

    1994-04-01

    The Puente Formation (PFm) is a middle to upper Miocene clastic unit lying unconformably on the middle to lower Miocene El Modeno Volcanics and Topanga Group, within the Los Angeles basin (LAB). The PFm, about 3900m thick, is composed of sandstone, conglomerate, and mudrock deposited on a submarine fan at bathyal depths. Several intrabasinal discordances suggest active tectonics during deposition. The succession consists of two main upward thickening and coarsening megacycles reflecting submarine fan progradation. The PFm is characterized up-section by: (1) thin-bedded fine sandstone and shale (La Vida M.) grading to thick-bedded coarse sandstone an conglomerate (soquel M.); (2) thin-bedded siltstone, mudrock and sandstone (Yorba M.) grading to thick- to very thick-bedded coarse-grained sandstone and conglomerate (Sycamore Canyon M.). Sandstones of the PFm are quartzofeldspathic and suggest a probable local provenance from the plutonic, volcanic, and metamorphic rocks of the San Gabriel Mountains. Petrological parameters, however, suggest variable contribution of these source rock units through time. Coarse-grained plutonic rock fragments are abundant for the entire succession and consist of plagioclase-rich plutonic rocks perhaps sourced from the Lowe granodiorite. Microlitic, lathwork to felsitic volcanic lithic grains are also present in the lower and middle part. In the Yorba M. there is a local increase of volcanic detritus (Lv/L - 0.80), represented by larger volcanic lithics and abundant volcaniclastic matrix. Metamorphic detritus is not very abundant; it is concentrated in the La Vida M. the PFm represents sedimentation during tectonically active time in the evolution of southern California.

  14. Petrology of Early Miocene volcanic rocks from Okushiri Island, Japan: geochemical characteristics of lithospheric mantle beneath the back-arc side of the NE Japan arc.

    NASA Astrophysics Data System (ADS)

    Sato, M.; Shuto, K.; Ishimoto, H.; Yagi, M.; Takazawa, E.

    2004-12-01

    The Sr and Nd isotopic studies on Tertiary to Quaternary basaltic rocks of the NE Japan arc have shown that isotopic characteristics of basaltic rocks found on the back-arc side of the NE Japan arc changed drastically from an undepleted isotopic signature (initial 87Sr/86Sr (SrI)=0.7040-0.7060 and initial 143Nd/144Nd (NdI)=0.51260-0.51284) to a depleted isotopic signature (SrI=0.7030-0.7040 and NdI=0.70284-0.51308) at around 15 Ma (Shuto et., 2004). This feature may have resulted from changes around 15 Ma in the isotopic compositions of the magma source beneath the back-arc side in the NE Japan arc due to the thinning of the undepleted subcontinental lithospheric mantle by upwelling of depleted asthenospheric mantle material during the opening of Japan Sea. Based on major and trace element data as well as SrI and NdI values for Early Miocene basaltic rocks from the back-arc side of the NE Japan arc, we examined geochemical characterization of the magma source (lithospheric mantle) for these basaltic rocks. Early Miocene (23-18 Ma) basalts and associated more felsic volcanic rocks form seven volcanic fields (Okushiri Is., Matsumae Pen., Fukaura, Oga Pen., Honjo, Atsumi and Sado Is.) delineating a 500 km-long array in the back-arc side of the NE Japan arc. In terms of major, trace element and Nd isotopic compositions, two groups of Early Miocene basalts can be distinguished. Group 1 is composed of tholeiitic basalts and alkali basalts, and is characterized by high TiO2 contents (1.5-2.5 %) and high (La/Yb)n ratios (>5.5), and high Zr/Y ratios (>6). These samples show the chondrite-normalized LREE-enriched patterns and have NdI values ranging from 0.51259 to 0.51282. Group 2 is composed of tholeiitic basalts, and is different from Group 1 by lower TiO2 contents (<1.5 %), lower (La/Yb)n ratios (<5) and lower Zr/Y ratios (<5.5). These samples show modelately LREE-enriched patterns and have NdI values ranging from 0.51250 to 0.51278. In contrast, Middle Miocene (after 15 Ma) basaltic rocks from the Niigata and Honjo areas in the back-arc side of the NE Japan arc have NdI values of 0.51286 to 0.51310, which are higher than those of Early Miocene basalts. These Middle Miocene samples are lower in TiO2 contents and (La/Yb)n and Zr/Y ratios than Early Miocene Group 1 samples, but partly overlap with Early Miocene Group 2 samples. The geochemical differences between Group 1 and 2 basalt magmas possibly originated from subcontinental lithospheric mantle may be due to differences in degrees of partial melting or heterogeneity of the mantle.

  15. Ostracoda (Arthropoda, Crustacea) in a Miocene oxygen minimum zone, Trinidad, West Indies: A test of the Platycopid Signal Hypothesis

    NASA Astrophysics Data System (ADS)

    Wilson, Brent; Coimbra, João C.; Hayek, Lee-Ann C.

    2014-10-01

    Studies of Recent ostracodes around the area of South America shed little light on the paleoenvironmental interpretation of Miocene assemblages. Consequently, interpretations of the Miocene ostracode assemblages must be supplemented using evidence from better documented taxa. Benthic foraminifera in samples from the Lower to Middle Miocene Brasso Formation at Brasso Village, Trinidad, have previously been used to distinguish three sample groupings (Beneath, Within and Above) around an oxygen minimum zone (OMZ), this being a layer of water within which dissolved oxygen concentrations can be as low as 0.1-1.0 mL/L. Using these same samples and the foraminiferal assemblage demarcations relative to the OMZ, this paper examines the associated and rich ostracode fauna of the Brasso Formation. The mean recovery of ostracode valves per sample was approximately three times greater in the Within OMZ sample group than in either of the Beneath OMZ or Above OMZ groups, perhaps reflecting the exclusion of macro-predators from within the OMZ. Individual rarefaction of species richness S to N = 300 valves was conducted for each sample group. This showed that S did not differ between the sample groups, ranging from 22.4 to 24.8. We used all ostracode species to model group separation. Based upon the Mahalanobis' criterion, we obtained significant group separation using a model with four taxa: Munseyella ex gr. minuta, Argilloecia posterotruncata, Munseyella sp. and Xestoleberis sp., while a fifth, Argilloecia spp., provided a significant but minor increase in separation probabilities over all groups. The two most abundant species (Bradleya sp., Gangamocytheridea reticulata) were thus not the best species for detecting the OMZ. Platycopid ostracodes of the genus Cytherella were found throughout the section, rather than concentrated within the OMZ, which contradicts the Platycopid Signal Hypothesis that OMZs are characterized by platycopid dominance. The total distribution and turnover of both ostracodal and foraminiferal assemblages were compared and contrasted quantitatively using a total assemblage turnover index (ATI) and the paleoenvironmental importance evaluated. The correlated between-sample ATI is for both groups lowest within the OMZ.

  16. Extreme Warmth in the Late Miocene North Atlantic

    NASA Astrophysics Data System (ADS)

    Pohlman, E. E.; Lawrence, K.; Morabito, J.; Harper, B.; Herbert, T. D.

    2008-12-01

    Climate in the late Miocene was unquestionably much warmer and less glaciated than the following Pliocene. This is implied by benthic oxygen isotope records, but as they necessarily combine the effects of temperature and ice volume, a precise climate history leading up to the onset of Northern Hemisphere glaciation is difficult to resolve. Unambiguous, continuous, and well-dated sea surface temperature (SST) records are required to characterize a pre-glacial world. Ideal sites lie in the sensitive high-latitudes, physically close to the growing ice sheets. ODP Site 907 (69N, 12E) is situated at a sensitively balanced location with respect to the world's ocean dynamics. A temperature record from this location may help to constrain the history of northern-sourced deep water, which plays a pivotal role in global climate. Located at the conflux of three major surface currents, Site 907 experienced the effects of migrating wind fronts, sea-ice cover, and current migration. Magnetostratigraphy demonstrates continuous sedimentation at the level of polarity zonation, and provides an age model to 14 ma. However, lack of abundant microfossils has prevented traditional isotope or faunal assemblage-based climate analysis from this Site. We present an alkenone-based SST and productivity (Total C37 alkenones/gram sediment = C37 total) record from this location, at moderate resolution (~50k between samples) covering the past ~14 ma. SSTs were as high as 23C at ~14 ma, cooling gradually (~1.6/my) to around 10C by 6 ma. A small increase in C37 total indicates a response to the 5 ma global biogenic bloom event observed in other records, but the most distinctive feature of the productivity record is a crash in haptophyte productivity at ~3.5 ma. This crash is echoed by biogenic opal records, and presumably total productivity in the high-latitude North Atlantic was equally affected. The long-term trends (e.g. the Miocene cooling trend) of global benthic ?18O records correlate well with this alkenone-derived local record. The dramatic late Miocene cooling and the mid-Pliocene productivity crash, however, hint at precursor adjustments to the climate system that significantly preceded the establishment of permanent ice sheets in the northern hemisphere.

  17. Porosity evolution of upper Miocene reefs, Almeria Province, southern Spain

    USGS Publications Warehouse

    Armstrong, A.K.; Snavely, P.D.; Addicott, W.O.

    1980-01-01

    Sea cliffs 40 km east of Almeria, southeastern Spain, expose upper Miocene reefs and patch reefs of the Plomo formation. These reefs are formed of scleractinian corals, calcareous algae, and mollusks. The reef cores are as much as 65 m thick and several hundred meters wide. Fore-reef talus beds extend 1,300 m across and are 40 m thick. The reefs and reef breccias are composed of calcific dolomite. They lie on volcanic rocks that have a K-Ar date of 11.5 m.y. and in turn are overlain by the upper Miocene Vicar Formation. In the reef cores and fore-reef breccia beds, porosity is both primary and postdepositional. Primary porosity is of three types: (a) boring clam holes in the scleractinian coral heads, cemented reef rocks, and breccias; (b) intraparticle porosity within the corals, Halimeda plates, and vermetid worm tubes; and (c) interparticle porosity between bioclastic fragments and in the reef breccia. Postdepositional moldic porosity was formed by the solution of aragonitic material such as molluscan and coral fragments. The Plomo reef carbonate rocks have high porosity and permeability, and retain a great amount of depositional porosity. Pores range in size from a few micrometers to 30 cm. The extensive intercrystalline porosity and high permeability resulted from dolomitization of micritic matrix. Dolomite rhombs are between 10 and 30 ? across. More moldic porosity was formed by the dissolution of the calclte bioclasts. Some porosity reduction has occurred by incomplete and partial sparry calcite infilling of interparticular, moldic, and intercrystalline voids. The high porosity and permeability of these reefs make them important targets for petroleum exploration in the western Mediterranean off southern Spain. In these offshore areas in the subsurface the volcanic ridge and the Plomo reef complex are locally onlapped or overlapped by 350 m or more of Miocene(?) and Pliocene fine-grained sedimentary rocks. The possibility exists that the buried Plomo reef deposits may form traps for oil and gas in the offshore areas southwest of the type locality. Stratigraphic traps also may occur where the Neogene sequence above the Plomo reef complex onlaps the volcanic ridge.

  18. Drivers and Dynamics of Ecological Responses to Abrupt Environmental Change on the Early Miocene Oregon Shelf

    NASA Astrophysics Data System (ADS)

    Belanger, C. L.

    2012-12-01

    We know that the biosphere responds to abrupt climate change, but know less about the dynamics of those changes and their proximal drivers. Studies of well-preserved fossil time-series spanning past climate events that utilize multiple environmental proxies and examine multiple taxonomic groups can provide critical insight into (a) the specific environmental factors to which the biota respond, (b) the rate and tempo of those responses, and (c) whether taxonomic groups respond similarly or differently to the same stresses. I examine the drivers and dynamics of ecological changes in continental shelf benthic foraminifera and molluscs from the Early Miocene Newport Member of the Astoria Formation in Oregon (20.3-16.3 mya), which spans a time of global warming leading into the Middle Miocene Climate Optimum. Stable isotope (?18O) data from three species of benthic foraminifera from the Astoria sediments indicate that the region abruptly warmed by 2-4C approximately 19 mya. In addition, ?13C values from epifaunal and infaunal foraminifera indicate an increase in productivity and organic carbon flux over time. Further, an increase in ?15N from bulk sediment and an increase in sedimentary laminations suggest oxygen levels declined. Multivariate analyses demonstrate a strong correlation between foraminiferal community metrics and ?15N suggesting that the foraminiferal community is tracking oxygenation levels while correlations to productivity changes appear indirect. Molluscan community metrics also have an approximately linear relationship to ?15N. Temperature itself had little direct influence on community composition. Changes in community composition and structure of both the foraminifera and the molluscs are abrupt relative to the duration of community states, but each group responds differently to the climate change. The foraminiferal community increases in the number of species and the evenness of species abundances while the molluscan community decreases in diversity, evenness, and body size suggesting the molluscs experienced greater stress. This difference in response may be explained by the shorter life cycles of benthic foraminifera and their ability to respond to seasonal changes in upwelling or oxygen stress. On the Oregon shelf in the last decade, low-oxygen conditions have increased in occurrence due to intensified wind-driven upwelling tied to modern warming. Faunal patterns from the Newport Member suggest that the benthic faunas may change in response to oxygenation and be less directly affected by productivity and temperature changes. Taxonomic groups may also to respond differently to the same environmental stresses due to physiological and ecological dissimilarities.

  19. A mantle plume beneath California? The mid-Miocene Lovejoy Flood Basalt, northern California

    USGS Publications Warehouse

    Garrison, N.J.; Busby, C.J.; Gans, P.B.; Putirka, K.; Wagner, D.L.

    2008-01-01

    The Lovejoy basalt represents the largest eruptive unit identified in California, and its age, volume, and chemistry indicate a genetic affinity with the Columbia River Basalt Group and its associated mantle-plume activity. Recent field mapping, geochemical analyses, and radiometric dating suggest that the Lovejoy basalt erupted during the mid-Miocene from a fissure at Thompson Peak, south of Susanville, California. The Lovejoy flowed through a paleovalley across the northern end of the Sierra Nevada to the Sacramento Valley, a distance of 240 km. Approximately 150 km3 of basalt were erupted over a span of only a few centuries. Our age dates for the Lovejoy basalt cluster are near 15.4 Ma and suggest that it is coeval with the 16.1-15.0 Ma Imnaha and Grande Ronde flows of the Columbia River Basalt Group. Our new mapping and age dating support the interpretation that the Lovejoy basalt erupted in a forearc position relative to the ancestral Cascades arc, in contrast with the Columbia River Basalt Group, which erupted in a backarc position. The arc front shifted trenchward into the Sierran block after 15.4 Ma. However, the Lovejoy basalt appears to be unrelated to volcanism of the predominantly calc-alkaline Cascade arc; instead, the Lovejoy is broadly tholeiitic, with trace-element characteristics similar to the Columbia River Basalt Group. Association of the Lovejoy basalt with mid-Miocene flood basalt volcanism has considerable implications for North American plume dynamics and strengthens the thermal "point source" explanation, as provided by the mantle-plume hypothesis. Alternatives to the plume hypothesis usually call upon lithosphere-scale cracks to control magmatic migrations in the Yellowstone-Columbia River basalt region. However, it is difficult to imagine a lithosphere-scale flaw that crosses Precambrian basement and accreted terranes to reach the Sierra microplate, where the Lovejoy is located. Therefore, we propose that the Lovejoy represents a rapid migration of plume-head material, at ??20 cm/yr to the southwest, a direction not previously recognized. ?? 2008 The Geological Society of America.

  20. A Miocene submarine volcano at Low Layton, Jamaica

    NASA Astrophysics Data System (ADS)

    Wadge, G.

    A submarine fissure eruption of Upper Miocene age produced a modest volume of alkaline basalt at Low Layton, on the north coast of Jamaica. The eruption occurred in no more than a few hundred meters of water and produced a series of hyaloclastites, pillow breccias and pillow lavas, massive lavas, and dikes with an ENE en echelon structure. The volcano lies on the trend of one of the island's major E-W strike-slip fault zones; the Dunavale Fault Zone. The K-Ar age of the eruption of 9.5 plus or minus 0.5 Ma. B.P. corresponds to an extension of the Mid-Cayman Rise spreading center inferred from magnetic anomalies and bathymetry of the Cayman Trough to the north and west of Jamaica. The Low Layton eruption was part of the response of the strike-slip fault systems adjacent to this spreading center during this brief episode of tectonic readjustment.

  1. A Miocene submarine volcano at Low Layton, Jamaica

    NASA Technical Reports Server (NTRS)

    Wadge, G.

    1982-01-01

    A submarine fissure eruption of Upper Miocene age produced a modest volume of alkaline basalt at Low Layton, on the north coast of Jamaica. The eruption occurred in no more than a few hundred meters of water and produced a series of hyaloclastites, pillow breccias and pillow lavas, massive lavas, and dikes with an ENE en echelon structure. The volcano lies on the trend of one of the island's major E-W strike-slip fault zones; the Dunavale Fault Zone. The K-Ar age of the eruption of 9.5 plus or minus 0.5 Ma. B.P. corresponds to an extension of the Mid-Cayman Rise spreading center inferred from magnetic anomalies and bathymetry of the Cayman Trough to the north and west of Jamaica. The Low Layton eruption was part of the response of the strike-slip fault systems adjacent to this spreading center during this brief episode of tectonic readjustment.

  2. Miocene to Pleistocene osmium isotopic records of the Mediterranean sediments

    NASA Astrophysics Data System (ADS)

    Kuroda, Junichiro; Jiménez-Espejo, Francisco J.; Nozaki, Tatsuo; Gennari, Rocco; Lugli, Stefano; Manzi, Vinicio; Roveri, Marco; Flecker, Rachel; Sierro, Francisco J.; Yoshimura, Toshihiro; Suzuki, Katsuhiko; Ohkouchi, Naohiko

    2016-01-01

    In the late Miocene the Mediterranean Sea experienced a salinity crisis and thick sequences of evaporites precipitated across the deep and marginal basins. In this study we report Os isotopic records from Deep Sea Drilling Project and Ocean Drilling Project cores in the Mediterranean: the Balearic Sea (Site 372), the Tyrrhenian Sea (Site 654), the Ionian Basin (Site 374), and the Florence Rise (Sites 375-376), as well as Integrated Ocean Drilling Project Site U1387 in Gulf of Cadiz, North Atlantic. Pliocene-Pleistocene sediments at all sites show 187Os/188Os values close to that of the coeval ocean water, indicating that the Mediterranean was connected to the North Atlantic. Evaporitic sediments deposited during the latest Miocene, however, have 187Os/188Os values significantly lower than coeval ocean water values. The offset of the Mediterranean evaporite 187Os/188Os is attributed to limited exchange with the North Atlantic during the Messinian salinity crisis. The source of unradiogenic Os is likely to be weathering of ultramafic rocks (ophiolites) cropping out in the Mediterranean's drainage basins. Based on a box model we estimated the amount of unradiogenic Os and the Atlantic-Mediterranean exchange rate to explain this offset. Os isotopic ratios of the pre-evaporite sediments in the western Mediterranean are almost identical to that of the coeval ocean water. In contrast, equivalent sediments from the Florence Rise have significantly lower 187Os/188Os values. The offset in the Os isotopic ratio on the Florence Rise is attributed either to limited water exchange between eastern and western Mediterranean or to local effects associated with exhumation of the Troodos ophiolites (Cyprus).

  3. Pannonian (Upper Miocene) deposits at Steinbrunn (Vienna Basin, Austria)

    NASA Astrophysics Data System (ADS)

    Grundtner, M.-L.; Harzhauser, M.; Mandic, O.; Gier, S.; Wagreich, M.

    2009-04-01

    The Steinbrunn sand pit is positioned at the southeastern margin of the Neogene Vienna Basin, about 5 km west of Eisenstadt. It exposes Upper Pannonian (Upper Miocene) lacustrine clays, sands and detritic limestones. The mollusc fauna allows a correlation with the latest Lymnocardium schedelianum Zone and the early Mytilopsis neumayri/zahalkai Zone, pointing to an age of c. 10 Ma. In terms of lithostratigraphy, the beds belong to the Upper Miocene Cary Formation (informally termed Neufeld beds). The section measured along a 100 m long quarry wall is structurally located in the gently ENE dipping eastern limb of a NNW-SSE striking anticline. The 24-m-thick succession represents a single coarsening and shallowing upward sequence. Three lithologic units have been distinguished. The lower unit comprises 7 m clays and silts bearing stringers with late Pannonian molluscs such as Mytilopsis neumayri and Melanopsis sturii together with limnocardiid and unionid bivalve shells. Carbonate contents are between 10 and 30The mineralogy of the clay samples was analyzed with X-ray diffraction. The samples contain quartz, minor amounts of feldspar, high amounts of calcite and dolomite, and the clay minerals smectite, muscovite and chlorite. The entire succession has formed within a floodplain environment. The clayey lower part represents lacustrine environments of local ponds. Geophysical logging was performed (gamma-ray and magnetic susceptibility) in order to investigate the depositional cyclicities observed within middle lithological unit. Spectral analysis suggests the presence of sedimentary cycles with a frequency of c. 3 m. Such small scale cycles might be the expression of the 21-ky-precessional cycles. Based on this assumption, the 8 depositional cycles of the succession may represent a total time of 170 ka.

  4. Miocene reef and nonreef carbonate rocks in Japan

    SciTech Connect

    Konishi, K.

    1988-01-01

    Japan's main islands experienced temperature climates throughout the Neogene with a tropical invasion around 16 Ma (early middle Miocene). This climatic warming, accompanied by a eustatic sea level rise, caused the unusual occurrence of reef facies, mangrove deposits, and lateritic beds in Japan. In cooler climates both before and after reef growth, sediments rich in bryozoan and algal material were widespread. Reef rocks emplaced as penecontemporaneous olistoliths in deep-water clastics at the Pacific coast of central Honshu are characterized by a wide lithologic spectrum, ranging from grainstone to bindstone. These rocks include rudstone and floatstone, which are rich in coralline algae (encrusting forms such as Lithophyllum and Mesophyllum and articulate forms such as Amphiroa) and codiacean algae (Halimeda) with hermatypic corals and large benthic formainifera (e.g., Nephrolepidina and Miogypsina) being less common. Two types of dolomite occur: (1) limpid dolomite with O/sup 18/ = -5.77 and with bipyramidal quartz and (2) microcrystalline dolomite with O/sup 18/ = 2.00 and with length-slow chalcedony. While microcrystalline dolomite tends to predominate in muddy matrix material, limpid dolomite appears to fill pores, some of which are moldic. Younger nonreef carbonate rocks, as occur on the Noto Peninsula of central Honshu, are commonly cross-bedded, contain Bryozoa, mollusks, small foraminifera, and echinoids, and are locally dolomitized. These dolomites are ascribed to a mixed-water origin. A different type of nonreef, yet reservoir-forming, dolostone occurs in the late middle Miocene of northeast Honshu and is interpreted to have formed as a transformation from bathyal opal.

  5. Assessment of geotechnical features of Miocene volcaniclastics using integrated logging

    SciTech Connect

    Toshiyuki, Kurahashi; Tomio, Inazaki; Yasuo, Nakamura

    1996-11-01

    This paper describes that integrated logging evaluates geotechnical conditions of fractures in Miocene volcaniclastics, where the damsites are for proposed. The purpose of this study was to detect fractures for seepage contols along borehole wall and characterize its geotechnical features by integrated logging. It is First step to evaluate the continuity and permeability of fractures. Integrated logging comprises of caliper, acoustic borehole televiewer, full-wave sonic, temperature, borehole video logging, natural gamma spectrum, and magnetic loggings. Natural gamma spectrum and magnetic logs would characterize litholofacies. Caliper, acoustic borehole televiewer and borehole video loggings would identify the depth, the dip and the azimuth of fractures. Besides temperature logging would determine the groudwater flow and suggest the permeable fracture. Integrated loggings were performed at damsites for proposed in northern Kanto district, middle part of Japan, where Miocene volcaniclastics are widely exposed. In Yunishigawa site, thermal jump was remarkably observed at 84 meters in depth from temperature logging. Its thermal gradient, differentiation of temperature, was 30 {degrees}C/m. The fracture causing it was recognized by the borehole enlargements from caliper logging, and had low slowness of full-wave sonic logging. Integrated logging enabled us to identify the fractures in the order of a dozen centimeters along a borehole wall. The identification would be useful for the geotechnical evaluation. Especially Differentiation of temperature revealed the fracture for seepage controls and classified the fractures into three types, which are (1) the permeable fracture circulating the runoff, (2) the permeable one controlling the groundwater from the deep, (3) the non-permeable fracture. As the first and the second are fractures for the seepage controls, they would involve the geotechnical problems.

  6. Gulf of Mexico miocene CO₂ site characterization mega transect

    SciTech Connect

    Meckel, Timothy; Trevino, Ramon

    2014-09-30

    This project characterized the Miocene-age sub-seafloor stratigraphy in the near-offshore portion of the Gulf of Mexico adjacent to the Texas coast. The large number of industrial sources of carbon dioxide (CO₂) in coastal counties and the high density of onshore urbanization and environmentally sensitive areas make this offshore region extremely attractive for long-term storage of carbon dioxide emissions from industrial sources (CCS). The study leverages dense existing geologic data from decades of hydrocarbon exploration in and around the study area to characterize the regional geology for suitability and storage capacity. Primary products of the study include: regional static storage capacity estimates, sequestration “leads” and prospects with associated dynamic capacity estimates, experimental studies of CO₂-brine-rock interaction, best practices for site characterization, a large-format ‘Atlas’ of sequestration for the study area, and characterization of potential fluid migration pathways for reducing storage risks utilizing novel high-resolution 3D (HR3D) seismic surveys. In addition, three subcontracted studies address source-to-sink matching optimization, offshore well bore management and environmental aspects. The various geologic data and interpretations are integrated and summarized in a series of cross-sections and maps, which represent a primary resource for any near-term commercial deployment of CCS in the area. The regional study characterized and mapped important geologic features (e.g., Clemente-Tomas fault zone, the regionally extensive Marginulina A and Amphistegina B confining systems, etc.) that provided an important context for regional static capacity estimates and specific sequestration prospects of the study. A static capacity estimate of the majority of the Study area (14,467 mi2) was estimated at 86 metric Gigatonnes. While local capacity estimates are likely to be lower due to reservoir-scale characteristics, the offshore Miocene interval is a storage resource of National interest for providing CO₂ storage as an atmospheric emissions abatement strategy. The natural petroleum system was used as an analog to infer seal quality and predict possible migration pathways of fluids in an engineered system of anthropogenic CO₂ injection and storage. The regional structural features (e.g., Clemente-Tomas fault zone) that exert primary control on the trapping and distribution of Miocene hydrocarbons are expected to perform similarly for CCS. Industrial-scale CCS will require storage capacity utilizing well-documented Miocene hydrocarbon (dominantly depleted gas) fields and their larger structural closures, as well as barren (unproductive, brine-filled) closures. No assessment was made of potential for CO₂ utilization for enhanced oil and gas recovery. The use of 3D numerical fluid flow simulations have been used in the study to greatly assist in characterizing the potential storage capacity of a specific reservoir. Due to the complexity of geologic systems (stratigraphic heterogeneity) and inherent limitations on producing a 3D geologic model, these simulations are typically simplified scenarios that explore the influence of model property variability (sensitivity study). A specific site offshore San Luis Pass (southern Galveston Island) was undertaken successfully, indicating stacked storage potential. Downscaling regional capacity estimates to the local scale (and the inverse) has proven challenging, and remains an outstanding gap in capacity assessments. In order to characterize regional seal performance and identify potential brine and CO₂ leakage pathways, results from three high-resolution 3D (HR3D) seismic datasets acquired by the study using novel HR3D (P-Cable) acquisition system showed steady and significant improvements in data quality because of improved acquisition and processing technique. Finely detailed faults and stratigraphy in the shallowest 1000 milliseconds (~800 m) of data allowed for the identification and mapping of unconformable surfaces including what is probably a surface associated with the last Pleistocene glacial lowstand. The identification of a previously unrecognized (in commercial seismic data) gas chimney that was clearly defined in the 2013 HR3D survey, indicates that HR3D surveys may be useful as both a characterization tool for the overburden of a potential carbon sequestration site and as an additional monitoring tool for future engineered injection sites. Geochemical modeling indicated that injection of CO₂ would result in minor dissolution of calcite, K-feldspar and albite. In addition, modeling of typical brines in Miocene age rocks indicate that approximately 5% of injection capacity would result from CO₂ dissolution into the brine. After extensive searches, no rock samples of the Marginulina A and Amphistegina B seals (“caprocks”) were obtained, but analyses of available core samples of other Miocene age mudrocks (seals or caprocks) indicate that they have sealing ability sufficient for potential CO2 storage in underlying sandstone units.

  7. Study of fossil wood from the Middle-Late Miocene sediments of Dhemaji and Lakhimpur districts of Assam, India and its palaeoecological and palaeophytogeographical implications

    NASA Astrophysics Data System (ADS)

    Mehrotra, R. C.; Bera, S. K.; Basumatary, S. K.; Srivastava, G.

    2011-08-01

    In order to reconstruct the palaeoclimate, a number of fossil wood pieces were collected and investigated from two new fossil localities situated in the Dhemaji and Lakhimpur districts of Assam. They belong to the Tipam Group considered to be of Middle-Late Miocene in age and show affinities with Gluta (Anacardiaceae), Bischofia (Euphorbiaceae), Bauhinia, Cynometra, Copaifera-Detarium-Sindora, Millettia-Pongamia, and Afzelia-Intsia (Fabaceae). The flora also records a new species of Bauhinia named Bauhinia miocenica sp. nov. The assemblage indicates a warm and humid climate in the region during the deposition of the sediments. The occurrence of some southeast Asian elements in the fossil flora indicates that an exchange of floral elements took place between India and southeast Asia during the Miocene.

  8. Miocene climate seasonality in southern India - first direct evidence for a weak Indian monsoon during the Middle Miocene Climate Optimum

    NASA Astrophysics Data System (ADS)

    Piller, W. E.; Reuter, M.; Kern, A. K.; Harzhauser, M.

    2012-04-01

    The Asian monsoon is an integral component of the global climate system. This large-scale atmospheric circulation comprises the East Asian summer and winter monsoon and the Indian monsoon subsystems, all characterized by seasonal reversing winds and precipitation changes associated with asymmetric heating of land and sea. The Neogene monsoon history is mainly reconstructed from chemical and physical weathering rates recorded in widely continuous marine sequences of the Indus Fan, Bengal Fan and South China Sea, which, depending on the source, physiography and sediment, indicate drier or wetter climates. These indirect climate proxies display an unusually dry period during the Middle Miocene Climate Optimum (MMCO, 16.5-15 Ma). As part of the FWF-projects P18189, P21414 and P23492, we present an Early/Middle Miocene coastal palynoflora record from the siliciclastic Ambalapuzha Formation at the coastal cliff of Varkala (Kerala Basin, SW India). Pollen assemblages and facies document a coastal wetland with mangrove vegetation. The Coexistence Approach was applied for palaeoclimatic reconstructions. This method uses climatic tolerances of all nearest living relatives known for a fossil flora by assuming that the tolerances of a fossil taxon are not significantly different from its modern counterpart. The maximum overlap of the environmental tolerances of all nearest living relatives (coexistence interval) is then regarded as being indicative of the most likely palaeoenvironment. By enquiring the Palaeoflora Database (http://www.palaeoflora.de/), the palaeoclimatic parameters of the pollen flora were calculated. The reconstructed climatic parameters for the MMCO show a seasonal precipitation pattern with a dry and a wet period and moderate rainfalls during the warmest period, which is comparable to the present day annual precipitation cycle in coastal Kerala, and affirms the presence of a monsoon-like atmospheric circulation over South India during the MMCO. However, the precipitation amounts during the wet (average 75%) and the warmest period (average 68%) were significantly reduced compared to today, while the rainfalls during the dry seasons are in the same order. This implies a weak Indian monsoon during the MMCO and a low thermal land - sea gradient between the Eurasian landmass and the Indian Ocean. Although a ~3C warmer global climate during the MMCO and a weaker monsoon accounts for a higher near-surface air temperature during summer, the calculated mean annual temperature (MAT; 24.4C) is 2.7C lower than at present. The estimated warmest month temperature is, however, in the same range as today. Therefore, the low coldest month temperature (CMT; 20.6-22.8C) in the Miocene has to account for the high MAT difference. This parameter represents the lower temperature threshold of the Varkala flora, and displays only the minimum temperature during the coldest month, which is significantly lower than the average CMT. Accordingly, the Miocene CMT approximates the present 24-h minimum temperature during the coldest month in Kerala (22.4C). The reconstructed seasonal temperature cycle supports climate models, which suggest a higher temperature increase in mid-latitudes than in low-latitudes as well as warmer equatorial sea surface temperatures during the MMCO.

  9. A partial hominoid innominate from the Miocene of Pakistan: Description and preliminary analyses

    PubMed Central

    Morgan, Michle E.; Lewton, Kristi L.; Kelley, Jay; Otrola-Castillo, Erik; Barry, John C.; Flynn, Lawrence J.; Pilbeam, David

    2015-01-01

    We describe a partial innominate, YGSP 41216, from a 12.3 Ma locality in the Siwalik Group of the Potwar Plateau in Pakistan, assigned to the Middle Miocene ape species Sivapithecus indicus. We investigate the implications of its morphology for reconstructing positional behavior of this ape. Postcranial anatomy of extant catarrhines falls into two distinct groups, particularly for torso shape. To an extent this reflects different although variable and overlapping positional repertoires: pronograde quadrupedalism for cercopithecoids and orthogrady for hominoids. The YGSP innominate (hipbone) is from a primate with a narrow torso, resembling most extant monkeys and differing from the broader torsos of extant apes. Other postcranial material of S. indicus and its younger and similar congener Sivapithecus sivalensis also supports reconstruction of a hominoid with a positional repertoire more similar to the pronograde quadrupedal patterns of most monkeys than to the orthograde patterns of apes. However, Sivapithecus postcranial morphology differs in many details from any extant species. We reconstruct a slow-moving, deliberate, arboreal animal, primarily traveling above supports but also frequently engaging in antipronograde behaviors. There are no obvious synapomorphic postcranial features shared exclusively with any extant crown hominid, including Pongo. PMID:25489095

  10. Herds Overhead: Nimbadon lavarackorum (Diprotodontidae), Heavyweight Marsupial Herbivores in the Miocene Forests of Australia

    PubMed Central

    Black, Karen H.; Camens, Aaron B.; Archer, Michael; Hand, Suzanne J.

    2012-01-01

    The marsupial family Diprotodontidae (Diprotodontia, Vombatiformes) is a group of extinct large-bodied (60–2500 kg) wombat-like herbivores that were common and geographically widespread in Cenozoic fossil deposits of Australia and New Guinea. Typically they are regarded to be gregarious, terrestrial quadrupeds and have been likened in body form among placental groups to sheep, rhinoceros and hippopotami. Arguably, one of the best represented species is the zygomaturine diprotodontid Nimbadon lavarackorum which is known from exceptionally well-preserved cranial and postcranial material from the middle Miocene cave deposit AL90, in the Riversleigh World Heritage Area, northwestern Queensland. Here we describe and functionally analyse the appendicular skeleton of Nimbadon lavarackorum and reveal a far more unique lifestyle for this plesiomorphic and smallest of diprotodontids. Striking similarities are evident between the skeleton of Nimbadon and that of the extant arboreal koala Phascolarctos cinereus, including the powerfully built forelimbs, highly mobile shoulder and elbow joints, proportionately large manus and pes (both with a semi-opposable digit I) and exceedingly large, recurved and laterally compressed claws. Combined with the unique (among australidelphians) proportionately shortened hindlimbs of Nimbadon, these features suggest adept climbing ability, probable suspensory behaviour, and an arboreal lifestyle. At approximately 70 kg, Nimbadon is the largest herbivorous mammal to have occupied the forest canopies of Australia - an ecological niche that is no longer occupied in any Australian ecosystem and one that further expands the already significant niche diversity displayed by marsupials during the Cenozoic. PMID:23185250

  11. Paleomagnetic Evidence for 'Oroclinal' Rotation in the Central Japan Arc from Early Miocene Sedimentary Rocks

    NASA Astrophysics Data System (ADS)

    Hoshi, H.; Sako, K.; Namikawa, T.; Ando, Y.

    2013-12-01

    In this study we focus on the general curvilinear trend of geologic zones (mainly accretionary complexes) in the central Japan arc. This feature is best represented by the Median Tectonic Line (MTL), a major boundary fault between the Sanbagawa high-P/T and Ryoke low-P/T metamorphic belts. Previous paleomagnetic data imply that the curvature is of 'oroclinal' origin, that is, the curved system was originally straight and formed after the accretionary processes and metamorphism. In order to quantitatively assess this possibility, we have carried out a paleomagnetic study for Early Miocene sedimentary rocks from two areas (Morozaki in Aichi Prefecture and Tomikusa in Nagano Prefecture) in central Japan. In Morozaki, oriented cores were collected at 22 sites from felsic tuff and siltstone beds of the Himaka Formation, which is the lowermost formation of the sedimentary sequence in this area. In Tomikusa, cores were taken at 24 sites from various lithologies of the Tomikusa Group. Rock specimens were subjected to stepwise alternating-field or thermal demagnetization in order to extract characteristic remanent magnetization (ChRM) components. Rock magnetic experiments suggest that ChRMs are carried primarily by magnetite. The Himaka Formation sites have reverse-polarity ChRM directions, and we consider this formation to be correlative to Chronozone C5Dr (18.056-17.533 Ma). The Tomikusa Group indicates both normal and reverse polarities and can be correlated to Chronozone C5D (18.056-17.235 Ma). Mean paleomagnetic directions for the two areas were determined and, together with existing paleomagnetic data from other areas, they were used for a paleomagnetic orocline test with a declination-strike diagram. Our result strongly suggests that the geologic zones and boundary faults (including the MTL) in the central Japan arc was straight before 18 Ma. We suggest that the oroclinal rotation results from a combination of the clockwise rotation of the southwestern Japan arc and the start of collision of the Izu-Bonin-Mariana arc with the central Japan arc, both during the late Early to early Middle Miocene (ca. 17-15 Ma).

  12. Extent of underthrusting of the Indian plate beneath Tibet controlled the distribution of Miocene porphyry Cu-Mo Au deposits

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Richards, Jeremy P.; Hou, Zengqian; Yang, Zhiming

    2014-02-01

    Miocene igneous rocks in the 1,600 km-long E-W Gangdese belt of southern Tibet form two groups separated at longitude 89 E. The eastern group is characterized by mainly intermediate-felsic calc-alkaline plutons with relatively high Sr/Y ratios (23 to 342), low (87Sr/86Sr)i ratios (0.705 to 0.708), and high ?Ndi values (+5.5 to -6.1). In contrast, the western group is characterized by mainly potassic to ultrapotassic volcanic rocks with relatively high Th and K2O contents, low Sr/Y ratios (11 to 163), high (87Sr/86Sr)i ratios (0.707 to 0.740), and low ?Ndi values (-4.1 to -17.5). The eastern plutonic group is associated with several large porphyry Cu-Mo Au deposits, whereas the western group is largely barren. We propose that the sharp longitudinal distinction between magmatism and metallogenic potential in the Miocene Gangdese belt reflects the breakoff of the Greater India slab and the extent of underthrusting by the Indian continental lithosphere at that time. Magmas to the east of 89 E were derived by partial melting of subduction-modified Tibetan lithosphere (mostly lower crust) triggered by heating of hot asthenospheric melt following slab breakoff. These magmas remobilized metals and volatile residual in the crustal roots from prior arc magmatism and generated porphyry Cu-Mo Au deposits upon emplacement in the upper crust. In contrast, magmas to the west of 89 E were formed by smaller volume partial melting of Tibetan lithospheric mantle metasomatized by fluids and melts released from the underthrust Indian plate. They are less hydrous and oxidized and did not have the capacity to transport significant amounts of metals into the upper crust.

  13. A new genus and species of Planopinae (Xenarthra: Tardigrada) from the Miocene of Santa Cruz Province, Argentina.

    PubMed

    Carlini, Alfredo A; Brandoni, Diego; Dal Molin, Carlos N

    2013-01-01

    Prepoplanops boleadorensis, a new genus and species of Planopinae (Xenarthra, Tardigrada), is described herein. The new taxon is based on a nearly complete specimen recovered from the Cerro Boleadoras Formation (Miocene, Rio Zeballos Group), in northwestern Santa Cruz Province, Argentina. The shape and length of the predentary region of the skull and the length of the diastema of Prepoplanops boleadorensis differ from those present in the species of Planops. The posterolateral opening of the mandibular canal and the position of the posterior margin of the mandibular symphysis differ from those of species of Prepotherium. In addition, Prepoplanops boleadorensis differs from Planops martini in the size of the humeral tuberosities, the development of the deltoid crest, the position of the distal margin of the humeral trochlea, the shape and position of the olecranon, the development of the femoral epicondyles, and the shape of the medial margins of the patellar trochlea and medial condyle. On the other hand, it differs from Prepotherium potens in the shape of the medial margin of the medial condyle. The recognition of Prepoplanops boleadorensis increases the diversity of Planopinae for the Miocene of Patagonia, Argentina. PMID:26312311

  14. A new genus of the family Jaculinidae (Cheilostomata, Bryozoa) from the Miocene of the tropical western Atlantic.

    PubMed

    Zágoršek, Kamil; Ramalho, Laís V; Berning, Björn; De Araújo Távora, Vladimir

    2014-01-01

    Pirabasoporella gen. nov. is introduced for three new bryozoan species from the Early Miocene of the tropical western Atlantic. The genus is placed in the family Jaculinidae Zabala, a peculiar group of cheilostome bryozoans characterised by reticulate colonies formed by uni- or biserial branches that are connected by kenozooidal struts. This colonial morphology superficially resembles colonies of the Paleozoic order Fenestrata (Stenolaemata) and some Recent Cyclostomata. As jaculinid colonies are anchored to soft sediments via rhizoids, however, they differ in life habit from Paleozoic and modern fenestrate colonies, which are firmly attached to stable substrata by an encrusting base.        The three new species are Pirabasoporella atalaiaensis n. sp. from the Brazilian Pirabas Formation, Pirabasoporella baitoae n. sp. from the Baitoa Formation (Dominican Republic), and Pirabasoporella chipolae n. sp. from the Floridan Chipola Formation. Their presence in the Early Miocene western Atlantic represents the earliest record of Jaculinidae, and suggests that the origin of the family, the only living species of which are known from the eastern Atlantic and Mediterranean Sea, extends well into the Paleogene.        The Jaculinidae is here transferred from the lepraliomorph superfamily Schizoporelloidea Jullien to the umbonulomorph Lepralielloidea Vigneaux owing to the partly umbonuloid frontal shield and non-schizoporelloid ovicell. PMID:25081761

  15. Late Miocene lineage divergence and ecological differentiation of rare endemic Juniperus blancoi: clues for the diversification of North American conifers.

    PubMed

    Moreno-Letelier, Alejandra; Mastretta-Yanes, Alicia; Barraclough, Timothy G

    2014-07-01

    Western North America and Mexico contain a large number of conifer species. This diversity could be the product of orographic and climate changes of the late Tertiary and Quaternary. In this study, we focus on the evolutionary history of Juniperus blancoi, in order to determine the impact of climate change and environmental heterogeneity on population differentiation. We estimated the population structure, phylogenetic relationships and historical demography of J.blancoi populations using nuclear genes. We correlated genetic structure with ecological differentiation, divergence times and changes in population size. Populations of J.blancoi are differentiated into three lineages that correspond to low-, mid- and high-altitude populations. The three groups diversified in the late Miocene, early Pliocene, with only a few events of gene flow since then. Two lineages in the north exhibited a pattern of population growth during the Pleistocene that could be linked to climate changes. Populations of J.blancoi experienced significant ecological differentiation and early divergence events, which correspond to periods of global cooling and mountain uplift during the Miocene. This suggests that mountain ranges in tropical and subtropical latitudes play an important role in the speciation and persistence of conifer taxa in diversity hotspots, by providing diverse environmental conditions. PMID:24611638

  16. Widespread Miocene deep-sea hiatuses: coincidence with periods of global cooling.

    USGS Publications Warehouse

    Barron, J.A.; Keller, G.

    1982-01-01

    High-resolution biostratigraphic analyses of Miocene deep-sea cores reveal eight intervals of widespread hiatuses in the world ocean. In complete sections these hiatuses correspond to intervals of cool faunal and floral assemblages, rapid enrichment of delta 18O, and sea-level regressions. These factors suggest that Miocene deep-sea hiatuses result from an increased intensity of circulation and corrosiveness of bottom currents during periods of increased polar refrigeration.-Authors

  17. Early Miocene origin and cryptic diversification of South American salamanders

    PubMed Central

    2013-01-01

    Background The currently recognized species richness of South American salamanders is surprisingly low compared to North and Central America. In part, this low richness may be due to the salamanders being a recent arrival to South America. Additionally, the number of South American salamander species may be underestimated because of cryptic diversity. The aims of our present study were to infer evolutionary relationships, lineage diversity, and timing of divergence of the South American Bolitoglossa using mitochondrial and nuclear sequence data from specimens primarily from localities in the Andes and upper Amazon Basin. We also estimated time of colonization of South America to test whether it is consistent with arrival via the Panamanian Isthmus, or land bridge connection, at its traditionally assumed age of 3 million years. Results Divergence time estimates suggest that Bolitoglossa arrived in South America from Central America by at least the Early Miocene, ca. 23.6 MYA (95% HPD 15.9-30.3 MYA), and subsequently diversified. South American salamanders of the genus Bolitoglossa show strong phylogeographic structure at fine geographic scales and deep divergences at the mitochondrial gene cytochrome b (Cytb) and high diversity at the nuclear recombination activating gene-1 (Rag1). Species often contain multiple genetically divergent lineages that are occasionally geographically overlapping. Single specimens from two southeastern localities in Ecuador are sister to the equatoriana-peruviana clade and genetically distinct from all other species investigated to date. Another single exemplar from the Andes of northwestern Ecuador is highly divergent from all other specimens and is sister to all newly studied samples. Nevertheless, all sampled species of South American Bolitoglossa are members of a single clade that is one of several constituting the subgenus Eladinea, one of seven subgenera in this large genus. Conclusions The ancestors of South American salamanders likely arrived at least by the Early Miocene, well before the completion of the Late Pliocene Panamanian land bridge (widely accepted as ca. 3 MYA). This date is in agreement with recent, controversial, arguments that an older, perhaps short-lived, land connection may have existed between South America and present-day Panama 23–25 MYA. Since its arrival in South America, Bolitoglossa has diversified more extensively than previously presumed and currently includes several cryptic species within a relatively small geographic area. Rather than two upper Amazonian species currently recorded for this region, we propose that at least eight should be recognized, although these additional lineages remain to be formally described. PMID:23497060

  18. Paleoecology of middle and late Miocene Monterey Formation, Upper Newport Bay, Newport Beach, California

    SciTech Connect

    Carlos, A.P.; Douglas, R.G.

    1986-07-01

    The Miocene Monterey Formation exposed along the cliffs of Upper Newport Bay represents a lower calcareous facies dominated by foraminifera and coccoliths, indicating warm climate and low nutrient waters, and a siliceous facies consisting of diatomaceous rocks, which records high productivity as a result of climatic deterioration and intensified upwelling. Using the distribution and preservation of foraminifera in the California continental borderland basins as a modern analog, they interpret the effect of changing environmental (climatic and oceanographic) conditions during the middle and late Miocene on the distribution and preservation of foraminifera, calcareous nannofossils, radiolarians, diatoms, and sediments. Two stratigraphic sections were sampled: (1) middle Miocene (Luisian) section 1, and (2) late Miocene (upper Mohnian) section 2. Section 1 best correlates with the middle Miocene Sphenolithus heteromorphus nannofossil zone. Benthic foraminifera indicate deposition in upper bathyal to upper middle bathyal depths. Poor preservation of calcareous tests is generally associated with homogeneous sediments, whereas better preservation is correlated with indistinctly laminated rocks. Stratigraphic section 2, which accumulated in upper bathyal depths, covers parts of the early late Miocene (upper Mohnian) Denticulopsis hustedtii-D. lauta and D. hustedtii diatom zones. Foraminifera and nannofossils are generally more abundant and better preserved in well laminated sediments than in sediments with homogeneous to indistinct laminations. Benthic foraminifera favoring low oxygen conditions have low diversities in rocks with poorly preserved laminations, but have higher densities in well laminated intervals.

  19. Application of carbon isotope stratigraphy to late miocene shallow marine sediments, new zealand.

    PubMed

    Loutit, T S; Kennett, J P

    1979-06-15

    A distinct (0.5 per mil) carbon-13/carbon-12 isotopic shift in the light direction has been identified in a shallow marine sedimentary sequence of Late Miocene age at Blind River, New Zealand, and correlated with a similar shift in Late Miocene Deep Sea Drilling Project sequences throughout the Indo-Pacific. A dated piston core provides an age for the shift of 6.2 +/- 0.1 million years. Correlations based on the carbon isotopic change require a revision of the previously established magnetostratigraphy at Blind River. The carbon shift at Blind River occurs between 6.2 and 6.3 +/- 0.1 million years before present. A new chronology provides an age for the evolutionary first appearance datum of Globorotalia conomiozea at 6.1 +/- 0.1 million years, the beginning of a distinct latest Miocene cooling event associated with the Kapitean stage at 6.2 +/- 0.1 million years, and the beginning of a distinct shallowing of water depths at 6.1 +/- 0.1 million years. The Miocene-Pliocene boundary as recognized in New Zealand is now dated at 5.3 +/- 0.1 million years. Extension of carbon isotope stratigraphy to other shallow Late Miocene sequences should provide an important datum for international correlation of Late Miocene shallow and deep marine sequences. PMID:17772422

  20. Late Miocene ignimbrites at the southern Puna-northern Sierras Pampeanas border (˜27°S): Stratigraphic correlation

    NASA Astrophysics Data System (ADS)

    Montero-López, Carolina; Guzmán, Silvina; Barrios, Fabiola

    2015-10-01

    New field observations and petrographic and geochemical data of pyroclastic deposits exposed along the Las Papas valley (border between southern Puna and northern Sierras Pampeanas, Argentina) and further north, lead us to propose a new stratigraphic correlation and classification of the late Miocene volcanism in this area. We redefine the Las Papas, Las Juntas, Aguada Alumbrera and Rosada ignimbrites and define the Agua Caliente and Del Medio ignimbrites. The whole set of ignimbrites are rhyolites and less frequently dacites of calc-alkaline affinity. In the present contribution we divide ignimbrites into the Agua Negra and Rincón groups, based mainly on their geochemical signature. The Agua Negra Group is formed by the Las Papas and Las Juntas ignimbrites, indurated and welded, lithic-rich, with crystal-poor pumices and crystal-rich matrix. The Rincón Group comprises the Agua Caliente, Aguada Alumbrera, Rosada and Del Medio ignimbrites, with variable welding degrees, lithic and crystal content. The greater enrichment of crystals in the matrix in comparison with the crystal content in pumices indicates significant elutriation during flow transport and thus volume estimations are to be considered lower bounds for the actual erupted volume. The total minimum estimated volume for the ignimbrites of the Agua Negra and Rincón groups is 2.8 km3 (2.3 km3 DRE). Field relationships and new analytical data indicate that the different acid ignimbrites that crop out in this small area are related to at least two different magma chambers. The widespread Quaternary volcanism in this area covers the older deposits, thus making it difficult to recognize the volcanic centers that produced these late Miocene ignimbrites.

  1. Late Oligocene-early Miocene birth of the Taklimakan Desert.

    PubMed

    Zheng, Hongbo; Wei, Xiaochun; Tada, Ryuji; Clift, Peter D; Wang, Bin; Jourdan, Fred; Wang, Ping; He, Mengying

    2015-06-23

    As the world's second largest sand sea and one of the most important dust sources to the global aerosol system, the formation of the Taklimakan Desert marks a major environmental event in central Asia during the Cenozoic. Determining when and how the desert formed holds the key to better understanding the tectonic-climatic linkage in this critical region. However, the age of the Taklimakan remains controversial, with the dominant view being from ? 3.4 Ma to ? 7 Ma based on magnetostratigraphy of sedimentary sequences within and along the margins of the desert. In this study, we applied radioisotopic methods to precisely date a volcanic tuff preserved in the stratigraphy. We constrained the initial desertification to be late Oligocene to early Miocene, between ? 26.7 Ma and 22.6 Ma. We suggest that the Taklimakan Desert was formed as a response to a combination of widespread regional aridification and increased erosion in the surrounding mountain fronts, both of which are closely linked to the tectonic uplift of the Tibetan-Pamir Plateau and Tian Shan, which had reached a climatically sensitive threshold at this time. PMID:26056281

  2. Late Oligocene–early Miocene birth of the Taklimakan Desert

    PubMed Central

    Zheng, Hongbo; Wei, Xiaochun; Tada, Ryuji; Clift, Peter D.; Wang, Bin; Jourdan, Fred; Wang, Ping; He, Mengying

    2015-01-01

    As the world’s second largest sand sea and one of the most important dust sources to the global aerosol system, the formation of the Taklimakan Desert marks a major environmental event in central Asia during the Cenozoic. Determining when and how the desert formed holds the key to better understanding the tectonic–climatic linkage in this critical region. However, the age of the Taklimakan remains controversial, with the dominant view being from ∼3.4 Ma to ∼7 Ma based on magnetostratigraphy of sedimentary sequences within and along the margins of the desert. In this study, we applied radioisotopic methods to precisely date a volcanic tuff preserved in the stratigraphy. We constrained the initial desertification to be late Oligocene to early Miocene, between ∼26.7 Ma and 22.6 Ma. We suggest that the Taklimakan Desert was formed as a response to a combination of widespread regional aridification and increased erosion in the surrounding mountain fronts, both of which are closely linked to the tectonic uplift of the Tibetan–Pamir Plateau and Tian Shan, which had reached a climatically sensitive threshold at this time. PMID:26056281

  3. Resource partitioning among top predators in a Miocene food web

    PubMed Central

    Domingo, M. Soledad; Domingo, Laura; Badgley, Catherine; Sanisidro, Oscar; Morales, Jorge

    2013-01-01

    The exceptional fossil sites of Cerro de los Batallones (Madrid Basin, Spain) contain abundant remains of Late Miocene mammals. From these fossil assemblages, we have inferred diet, resource partitioning and habitat of three sympatric carnivorous mammals based on stable isotopes. The carnivorans include three apex predators: two sabre-toothed cats (Felidae) and a bear dog (Amphicyonidae). Herbivore and carnivore carbon isotope (δ13C) values from tooth enamel imply the presence of a woodland ecosystem dominated by C3 plants. δ13C values and mixing-model analyses suggest that the two sabre-toothed cats, one the size of a leopard and the other the size of a tiger, consumed herbivores with similar δ13C values from a more wooded portion of the ecosystem. The two sabre-toothed cats probably hunted prey of different body sizes, and the smaller species could have used tree cover to avoid encounters with the larger felid. For the bear dog, δ13C values are higher and differ significantly from those of the sabre-toothed cats, suggesting a diet that includes prey from more open woodland. Coexistence of the sabre-toothed cats and the bear dog was likely facilitated by prey capture in different portions of the habitat. This study demonstrates the utility of stable isotope analysis for investigating the behaviour and ecology of members of past carnivoran guilds. PMID:23135673

  4. Porosity evolution of upper Miocene reefs, Almeria Province, Southern Spain

    SciTech Connect

    Armstrong, A.K.; Snavely, P.D. Jr.; Addicott, W.O.

    1980-02-01

    In the reef cores and fore-reef breccia beds, porosity in both primary and postdepositional. Primary porosity is of three types: (a) boring clam holes in the scleractinian coral heads, cemented reef rocks, and breccias; (b) intraparticle porosity within the corals, Halimeda plates, and vermetid worm tubes; and (c) interparticle porosity between bioclastic fragments and in the reef breccia. Postdepositional moldic porosity was formed by the solution of aragonitic material such as molluscan and coral fragments. The Polomo reef carbonate rocks have high porosity and permeability, and retain a great amount of depositional porosity. Pores range in size from a few micrometers to 30 cm. The extensive intercrystalline porosity and high permeability resulted from dolomitization of micritic matrix. Some porosity reduction has occured by incomplete and partial sparry calcite infilling of interparticular, moldic, and intercrystalline voids. The high porosity and permeability of these reefs make them important targets for petroleum exploration in the western Mediterranean off southern Spain. In these offshore areas in the subsuface the volcanic ridge and the Plomo reef complex are locally onlapped or overlapped by 350 m or more of Miocene and Pliocene fine-grained sedimentary rocks. The possibility exists that the buried Plomo reef deposits may form traps for oil and gas in the offshore areas southwest of the type locality. Stratigraphic traps also may occur where the Neogene sequence above the Plomo reef complex onlaps the volcanic ridge. 17 figures.

  5. Late Miocene calcareous nannofossil genus Catinaster: taxonomy, evolution and magnetobiochronology

    USGS Publications Warehouse

    Peleo-Alampay, A.; Bukry, D.; Liu, L.; Young, J.R.

    1998-01-01

    A systematic study on the evolution and stratigraphic distribution of the species of Catinaster from several DSDP/ODP sites with magnetostratigraphic records is presented. The evolution of Catinaster from Discoaster is established by documentation of a transitional nannofossil species, Dicoaster transitus. Two new subspecies, Catinaster coalitus extensus and Catinaster calyculus rectus are defined which appear to be intermediates in the evolution of Catinaster coalitus coalitus to Catinaster calyculus calyculus. The first occurrence of C. coalitus is shown to be in the lower part of C5n.2n at 10.7-10.9 Ma in the low to mid-latitude Atlantic and Pacific oceans. The last occurrence of C. coalitus coalitus varies from the upper part of C5n.2n to the lower portion of C4A. Magnetobiostratigraphic evidence suggests that the FO of C. calyculus rectus is diachronous. Catinaster mexicanus occurs in the late Miocene and has been found only in the eastern equatorial Pacific, the Indian Ocean and the Gulf of Mexico.

  6. Miocene dispersal drives island radiations in the palm tribe Trachycarpeae (Arecaceae).

    PubMed

    Bacon, Christine D; Baker, William J; Simmons, Mark P

    2012-05-01

    The study of three island groups of the palm tribe Trachycarpeae (Arecaceae/Palmae) permits both the analysis of each independent radiation and comparisons across the tribe to address general processes that drive island diversification. Phylogenetic relationships of Trachycarpeae were inferred from three plastid and three low-copy nuclear genes. The incongruent topological position of Brahea in CISP5 was hypothesized to be caused by a gene duplication event and was addressed using uninode coding. The resulting phylogenetic trees were well-resolved and the genera were all highly supported except for Johannesteijsmannia and Serenoa. Divergence time analysis estimated the stem of the tribe to be approximately 86 Ma and the crown to be 38 Ma, indicating that significant extinction may have occurred along this branch. Historical biogeographic analysis suggested that Trachycarpeae are of southern North American, Central American, or Caribbean origin and supports previous hypotheses of a Laurasian origin. The biogeography and disjunctions within the tribe were interpreted with respect to divergence times, the fossil record, and geological factors such as the formation of the Greater Antilles--Aves Ridge, the Bering and the North Atlantic land bridges, tectonic movement in Southeast Asia, climatic shifts between the Eocene and Pliocene, and volcanism in the Pacific basin. In considering the three major island radiations within Trachycarpeae, Miocene dispersal appears to have been the driving force in allopatric speciation and is highlighted here as an emerging pattern across the tree of life. PMID:22223444

  7. A new species of Metopocetus (Cetacea, Mysticeti, Cetotheriidae) from the Late Miocene of the Netherlands.

    PubMed

    Marx, Felix Georg; Bosselaers, Mark E J; Louwye, Stephen

    2016-01-01

    The family Cetotheriidae has played a major role in recent discussions of baleen whale phylogenetics. Within this group, the enigmatic, monotypic Metopocetus durinasus has been interpreted as transitional between herpetocetines and other members of the family, but so far has been restricted to a single, fragmentary cranium of uncertain provenance and age. Here, we expand the genus and shed new light on its phylogenetic affinities and functional morphology by describing Metopocetus hunteri sp. nov. from the Late Miocene of the Netherlands. Unlike the holotype of M. durinasus, the material described here is confidently dated and preserves both the tympanic bulla and additional details of the basicranium. M. hunteri closely resembles M. durinasus, differing primarily in its somewhat less distally expanded compound posterior process of the tympanoperiotic. Both species are characterised by the development of an unusually large fossa on the ventral surface of the paroccipital process, which extends anteriorly on to the compound posterior process and completely floors the facial sulcus. In life, this enlarged fossa may have housed the posterior sinus and/or the articulation of the stylohyal. Like other cetotheriids, Metopocetus also bears a well-developed, posteriorly-pointing dorsal infraorbital foramen near the base of the ascending process of the maxilla, the precise function of which remains unclear. PMID:26835183

  8. Subcellular preservation in giant ostracod sperm from an early Miocene cave deposit in Australia

    PubMed Central

    Matzke-Karasz, Renate; Neil, John V.; Smith, Robin J.; Symonov, Radka; Mo?kovsk, Libor; Archer, Michael; Hand, Suzanne J.; Cloetens, Peter; Tafforeau, Paul

    2014-01-01

    Cypridoidean ostracods are one of a number of animal taxa that reproduce with giant sperm, up to 10 000 m in length, but they are the only group to have aflagellate, filamentous giant sperm. The evolution and function of this highly unusual feature of reproduction with giant sperm are currently unknown. The hypothesis of long-term evolutionary persistence of this kind of reproduction has never been tested. We here report giant sperm discovered by propagation phase contrast X-ray synchrotron micro- and nanotomography, preserved in five Miocene ostracod specimens from Queensland, Australia. The specimens belong to the species Heterocypris collaris Matzke-Karasz et al. 2013 (one male and three females) and Newnhamia mckenziana Matzke-Karasz et al. 2013 (one female). The sperm are not only the oldest petrified gametes on record, but include three-dimensional subcellular preservation. We provide direct evidence that giant sperm have been a feature of this taxon for at least 16 Myr and provide an additional criterion (i.e. longevity) to test hypotheses relating to origin and function of giant sperm in the animal kingdom. We further argue that the highly resistant, most probably chitinous coats of giant ostracod sperm may play a role in delaying decay processes, favouring early mineralization of soft tissue. PMID:24827442

  9. A new species of Metopocetus (Cetacea, Mysticeti, Cetotheriidae) from the Late Miocene of the Netherlands

    PubMed Central

    Bosselaers, Mark E.J.; Louwye, Stephen

    2016-01-01

    The family Cetotheriidae has played a major role in recent discussions of baleen whale phylogenetics. Within this group, the enigmatic, monotypic Metopocetus durinasus has been interpreted as transitional between herpetocetines and other members of the family, but so far has been restricted to a single, fragmentary cranium of uncertain provenance and age. Here, we expand the genus and shed new light on its phylogenetic affinities and functional morphology by describing Metopocetus hunteri sp. nov. from the Late Miocene of the Netherlands. Unlike the holotype of M. durinasus, the material described here is confidently dated and preserves both the tympanic bulla and additional details of the basicranium. M. hunteri closely resembles M. durinasus, differing primarily in its somewhat less distally expanded compound posterior process of the tympanoperiotic. Both species are characterised by the development of an unusually large fossa on the ventral surface of the paroccipital process, which extends anteriorly on to the compound posterior process and completely floors the facial sulcus. In life, this enlarged fossa may have housed the posterior sinus and/or the articulation of the stylohyal. Like other cetotheriids, Metopocetus also bears a well-developed, posteriorly-pointing dorsal infraorbital foramen near the base of the ascending process of the maxilla, the precise function of which remains unclear. PMID:26835183

  10. Dating intrusion and cooling of Cenozoic granitoids in the Dinarides of Southern Serbia and discussion of the geodynamic setting of Paleocene-Miocene magmatism in the Balkan Peninsula

    NASA Astrophysics Data System (ADS)

    Senecio, Schefer; Cvetkovi?, Vladica; Fgenschuh, Bernhard; Kounov, Alexandre; Ovtcharova, Maria; Schaltegger, Urs; Schmid, Stefan

    2010-05-01

    This paper presents the results of high precision single grain U-Pb dating and Hf isotope analyses of thermally annealed and chemically abraded zircons from the Kopaonik, Drenje, eljin, Golija and Polumir intrusions in the inner Dinarides of southern Serbia. In addition, new zircon and apatite fission-track data together with local structural observations, allow for constraining the subsequent exhumation history of these intrusions. Two age groups were determined for the granitoid intrusions: (i) Oligocene intrusive bodies (Kopaonik, Drenje, eljin) ranging in age from 31.7 to 30.6 Ma and (ii) Miocene Golija and Polumir intrusions which emplaced at 20.58-20.17 and 18.06-17.74 Ma, respectively. The apatite fission-track modelling combined with zircon central ages show rapid cooling from above 300 to ca. 80 C between 16 and 10 Ma for granitoids of both age groups, followed by rather slow cooling to surface temperatures for the last 10 Ma. Fast Middle Miocene cooling between 16 and 10 Ma is caused by extensional exhumation of the plutons that are located in the footwall of core-complexes. This documents that Miocene magmatism and core-complex formation leading to formation of the Pannonian basin also affected a part of the mountainous areas of the internal Dinarides. The discussion of an extensive set of age data from the literature and the geodynamic setting of the Balkan Peninsula reveals that there is no direct connection of the Dinaridic Late Eocene to earliest Miocene magmatic belt with contemporaneous Periadriatic intrusions in the Alps and along the Mid-Hungarian fault zone as proposed in the literature. We insist on the fact that the subduction polarity in the Alps, including that within the Western Carpathians north of the Mid-Hungarian fault zone, is opposite to that of the Dinarides during the given time span. Instead, we propose that Late Eocene to Oligocene magmatism, which affects the Adria-derived lower plate units of the internal Dinarides, may be caused by delamination of the Adriatic mantle from the overlying crust, associated with intra-plate convergence that propagates outward into the external Dinarides during this time interval. Miocene magmatism, on the other hand, is associated with core-complex formation at the southern rim of the Pannonian basin probably associated with the W-directed subduction of the European lithosphere beneath the Carpathians, possibly interfering with ongoing Dinaridic-Hellenic back-arc extension.

  11. Middle Miocene Hominoids dispersion and radiation: impact of climate and vegetation changes in Europe

    NASA Astrophysics Data System (ADS)

    Hamon, N.; Sepulchre, P.; Contoux, C.; Jaeger, J.-J.; Ramstein, G.

    2012-04-01

    The middle Miocene is a time of important climatic changes, and a crucial period for ape's evolution. The Middle Miocene Climatic Optimum (MMCO), that occurred approximately 17 to 15 Ma, was one of the last global warming event of the Cenozoic. This period also corresponds to the first dispersion of apes from Africa to Europe, which was made possible by tectonic and environmental changes, in particular the expansion of hominoids habitat: (sub-)tropical forest. Following the MMCO, an abrupt global cooling occurred that coincides with an important radiation of European hominoids. The most common view is that the widening of hominoids habitat during the MMCO was the main factor of their dispersion from Africa to Europe. Moreover, the major climatic change that followed induced an opening of the environment because of cooler and dryer conditions, which should have lead to a fragmentation of hominoids' habitat. This imply that hominoids evolved separately in refuges during the end of the Miocene, so the radiation observed in the fossil record of European Miocene apes is interpreted as a divergent evolution in a fragmented habitat. However, no study has yet demonstrated this evolutionary scenario. Our aim is to study the environmental changes during the middle Miocene, in particular climate and vegetation changes, and to link them with these two major events of hominoids' evolution. Using climate and vegetation models, we investigate the role of environmental variation in hominoids' evolution during the middle Miocene, in particular between 17 and 14 Ma. We perform two climatic experiments (16Ma and 14Ma) with the atmospheric general circulation model LMDZ. The results of these experiments will then be used to force the dynamic vegetation model CARAIB. This should help us to simulate hominoids' habitat for the two time period chosen, and to discuss the role of important climate change for Miocene apes evolution.

  12. Miocene squat lobsters (Decapoda, Anomura, Galatheoidea) of the Central Paratethys a review, with description of a new species of Munidopsis

    PubMed Central

    Hyn, M.; Gapari?, R.; Robins, C.M.; Schlgl, J.

    2015-01-01

    All squat lobsters of the families Galatheidae, Munididae and Munidopsidae from the Miocene of the Central Paratethys are reviewed taxonomically. Based on additional observations emended diagnoses are provided for Agononida cerovensis and Galathea weinfurteri, from the Lower and Middle Miocene, respectively. Munidopsis is represented by two species in the study area; additional data for M. lieskovensis from the Lower Miocene of Slovakia are presented and a new species, M. palmuelleri, from the Middle Miocene of Slovenia is erected. Implications for palaeoenvironmental reconstructions are briefly discussed for each taxon. PMID:26005283

  13. The Late Miocene Carbon Isotope Shift and Marine Biological Productivity.

    NASA Astrophysics Data System (ADS)

    Diester-Haass, L.; Billups, K.; Emeis, K. C.

    2004-12-01

    The late Miocene global carbon isotope shift of approximately 1 per mil is not well understood. Is it linked to ocean-related processes such as the AƒAøAøâ_sA¬A.â_oBiologic BloomAƒAøAøâ_sA¬ \\(Farrell et al., 1995\\), or to changes in type \\(C3/C4 plants\\) or cover of terrestrial vegetation? Here we examine the evolution of marine biological productivity during the isotope shift at ODP Site 846 \\(Pacific equatorial upwelling, where the AƒAøAøâ_sA¬A.â_oBiologic BloomAƒAøAøâ_sA¬ has been first described, Farrell al, 1995\\) and at Indian Ocean Site 721 \\(monsoon-driven upwelling\\), and compare their productivity history with non upwelling locations in the Atlantic Ocean. The onset of the carbon isotope shift is accompanied at all locations by an increase in paleoproductivity derived from benthic foraminiferal accumulation rates \\(expressed as gC/cm2 * ky; Huerguera, 2000\\) and increased abundance of Uvigerina spp.. At the equatorial upwelling sites the increase is comparable to half present-day values to present-day values; in the Atlantic Ocean paleoproductivity increases from present-day up to 3 times present-day values. But the productivity maxima are not concurrent. The carbon isotope shift is accompanied by severe carbonate dissolution and reduced ventilation of bottom waters, as reflected in the occurrence of pyrite and good preservation of cartilageous fish debris. Carbonate preservation is good since about 6 Ma despite high productivity. We discuss changing deep water circulation patterns, increased weathering and continental nutrient delivery, as well as erosion of terrestrial vegetation as possible factors to explain our findings.

  14. Provenance of the lower Miocene of the Gulf of Mexico from detrital zircon double dating

    NASA Astrophysics Data System (ADS)

    xu, J.

    2013-12-01

    The lower Miocene interval of the Gulf of Mexico (GOM) has recently gained increasing attention from oil and gas industry due to its hydrocarbon potential below the salt canopy. However, it has been less well studied than both the underlying Oligocene and overlying middle Miocene strata. The lower Miocene worldwide is a transitional period of tectonic, climatic, and oceanographic change. In particular, it is a period of major tectonic reorganization in the western interior of North America (Rocky Mountains), involving a shift from the Oligocene thermal phase, with abundant volcanic activity recorded in the thick Frio/Vicksburg succession of the GOM, to the Miocene Basin-Range extensional phase. Climatic conditions also changed from a relatively arid Oligocene to wetter Miocene, resulting in increased sediment yields from exhumed tectonic structures. Previous provenance studies used proportions of quartz, feldspar and lithic fragments and consideration of likely river courses through known paleogeomorphological elements. Only limited detrital zircon (DZ) U-Pb studies on Paleocene strata have been undertaken and there has been no previous U-Pb and (U-Th)/He double dating in the GOM. In this study we apply the latest analytical approaches, such as DZ U-Pb dating to gain robust source terranes ages and more fully elucidate the complex sediment provenance and dispersal history of GOM. We also employ DZ (U-Th)/He (ZHe) dating, combined with DZ U-Pb, to not only define sedimentary provenance but also the exhumation histories of detrital source regions. Samples of lower Miocene outcrop exposures in Texas and Louisiana have been collected to discriminate the varied tectonic and drainage system changes across the basin in lateral. In addition, samples from the Eocene, Oligocene and middle Miocene have been obtained to reveal vertical shift of source terranes contributions. Our initial age data show detrital zircons of lower Miocene sediments come from a wide range of source terranes including a large populations from the western interior of North America (Rocky Mountains), Grenville, Mid-Continent, and Yavapai-Mazatzal provinces, with smaller populations from the Appalachian-Ouachita, Wyoming or Superior regions. Based on U-Pb dating results, we will carry out (U-Th)/He dating on selected zircons to reveal the detailed exhumation histories of the sediment source regions. Using the dual criteria of DZ crystallization age (U-Pb) and cooling age (U-Th/He) to constrain provenance will enable us to generate rigorous reconstructions of the lower Miocene depositional systems from source terrane to deep-water sink for this key transitional period in geologic history.

  15. Post-Miocene extension in Central Anatolia; It's linkage to Aegean extension

    NASA Astrophysics Data System (ADS)

    Rojay, Bora; Özsayın, Erman

    2013-04-01

    Post-Miocene extension in Central Anatolia; It's linkage to Aegean extension Anatolian Plate, -where Central Anatolia situated on-, escapes westward onto African plate along Eastern Mediterranean-Cyprus subduction zone, sliding by North and East Anatolian faults. Central Anatolia is bounded by dextral North Anatolian Fault from north, Taurides from south and it is fragmented by strike slip faults evolving under N-S compression in east and by Aegean horst and grabens evolving under N-S extension in west. To be able to delineate and understand the deformational order in Central Anatolia and its linkage to Aegean region, various sectors with the Anatolia are chosen, namely, Ankara region (Beypazarı to Kazan Miocene basins), Eskişehir region (Mihallıçık to İnönü Miocene basins) in Central Anatolia, Gediz-Alaşehir Graben and Efes areas in Western Anatolia are selected. To sum up, in a wide region from Central Anatolia to Western Anatolia, i. Unconformities btw uppermost Late Miocene and Plio-Quaternary, and btw Plio-Quaternary and Quaternary are clearly identified in both regions, ii) ENE-WSW to N-S compression (intense post-Late Miocene - pre-Pliocene folding) with almost E-W extension operates during post-Miocene (during Pliocene) is followed by a short lived strike slip deformation during Early Pliocene, and finally by NW-SE to WNW-ESE oriented multi directional extension during post-Plio-Quaternary. And in Gediz-Alaşehir Graben and Efes (western Anatolia); a continuous NNE-SSW to NE-SW multi directed extension since post-Late Miocene following almost N-S compression (post-Early Miocene) operated. Dextral strike slip faulting with normal components and normal faulting with right lateral strike slip components are recorded on same fault planes, iii) Quaternary normal faulting post dates folding, reverse and strike slip faulting in both regions. However, right lateral strike slip faulting is recorded to the NW tip of the normal faults like Efes, Manisa and Eskişehir faults, iv) under the new kinematic findings, the boundary conditions of neotectonic domains should have to be redefined in Anatolian plate, and v) during the escape of Anatolian plate towards east-southeast, based on the shift of principal stress directions counterclockwise block rotations can be operated along the "microplates" where northern blocks of the "microplates" are downthrown. Key words: normal faulting, extension, neotectonic domains, post-Miocene, central Anatolia.

  16. The late Miocene 'paradox' of the CO2 climate sensitivity (Invited)

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Pagani, M.

    2013-12-01

    Ancient climates provide opportunities for studying the impact of CO2 change on global temperatures. While advances in CO2-reconstruction techniques are yielding a clearer picture of the Cenozoic history of CO2 (Beerling and Royer, 2011), the late Miocene (~12-5 Ma) remains enigmatic. For example, recent sea-surface temperature reconstructions from 12-5 Ma have shown that mid-latitude and equatorial regions of the Pacific cooled 6C (LaRiviere et al., 2012) and 2C (Zhang et al., 2013), respectively. This cooling trend was probably initiated at the mid-Miocene climate transition (14 Ma), and continued into the Plio-Pleistocene. However, existing compilation of late Miocene - Pliocene CO2 records show little variability, with some indicating a rise in CO2 concurrent with global cooling. Here we present four continuous alkenone-based CO2 records using Pacific sediment samples (ODP Sites 769, 806, 850 and 1143), from late Miocene to Pliocene. Compound-specific carbon isotope measurements show a broad decrease in alkenone ?13C values in all four sites, suggesting increasing pCO2 levels in the late Miocene. Decreasing ocean temperature and increasing pCO2 in the late Miocene appears to challenge a leading climatic role for CO2 during this time. Alternatively, alkenone-CO2 estimates are flawed in the late Miocene because factors other than CO2, such as algal growth rate, cell geometry, and carbon-fixation pathways, can influence carbon isotopic fractionation during algae growth. We explore the uncertainty of the alkenone-CO2 methodology and assess the potential influence that non-CO2 variables have in producing spurious CO2 estimates and trends. Beerling, D.J., Royer, D.L., 2011. Convergent Cenozoic CO2 history. Nat. Geosci. 4, 418-420. LaRiviere, J.P., Ravelo, A.C., Crimmins, A., Dekens, P.S., Ford, H.L., Lyle, M., Wara, M.W., 2012. Late Miocene decoupling of oceanic warmth and atmospheric carbon dioxide forcing. Nature 486, 97-100. Zhang, Y.G., Pagani, M., Liu, Z., 2013. Temperature evolution of the equatorial Pacific since late Miocene and the ancient El Nino. In Preperation.

  17. Miocene fluvial-tidal sedimentation in a residual forearc basin of the Northeastern Pacific Rim: Cook Inlet, Alaska case study

    SciTech Connect

    Stricker, G.D.; Flores, R.M. )

    1996-01-01

    Cook Inlet in southern Alaska represents a Cenozoic residual forearc basin in a convergent continental margin, where the Pacific Plate is being subducted beneath the North American Plate. This basin accumulated the >6,700-m-thick, mainly nonmarine, Eocene-Pliocene Kenai Group. These rocks contain biogenic coal-bed methane estimated to be as high as 245 TCF. Lignites to subbituminous coals with subsurface R[sub o] ranging from 0.38 to 0.73 percent and the stage of clay-mineral diagenesis and expandibility indicate a thermally [open quotes]cool[close quotes] basin. Miocene Tyonek and Beluga Formations compose 65 percent (>4,300 m thick) of the Kenai Group. The Tyonek includes conglomeratic sandstones, siltstones, mudstones, coals, and carbonaceous shales, interpreted as braided- stream deposits. These fluvial deposits are interbecided with burrowed, lenticular, and flaser-bedded sandstones, siltstones, and mudstones, interpreted as tidal deposits. Tyonek framework conglomerates formed in wet alluvial fans incised on paleovalleys of the Chugach terrane. Coal-forming mires are well developed on abandoned braided-stream deposits. Tyonek drainages formed in high-gradient alluvial plains inundated by tides similar to environments in the modern upper Cook Inlet. The upper Miocene Beluga consists of sandstones, siltstones, mudstones, carbonaceous shales, and coals deposited in meandering (low sinuosity) and anastomosed fluvial systems. These fluvial deposits alternated vertically with deposits of coal-forming mires. The Beluga drainages formed in low-gradient alluvial plains. The high-gradient Tyonek alluvial plain was probably controlled by provenance uplift and eustatic change, whereas the low-gradient Beluga alluvial plain was influenced by subdued provenance uplift and rapid basin subsidence. Rapid sedimentation on both these low- and high-gradient alluvial plains, which kept up with subsidence, produced a thermally [open quotes]cool[close quotes] basin.

  18. Miocene fluvial-tidal sedimentation in a residual forearc basin of the Northeastern Pacific Rim: Cook Inlet, Alaska case study

    SciTech Connect

    Stricker, G.D.; Flores, R.M.

    1996-12-31

    Cook Inlet in southern Alaska represents a Cenozoic residual forearc basin in a convergent continental margin, where the Pacific Plate is being subducted beneath the North American Plate. This basin accumulated the >6,700-m-thick, mainly nonmarine, Eocene-Pliocene Kenai Group. These rocks contain biogenic coal-bed methane estimated to be as high as 245 TCF. Lignites to subbituminous coals with subsurface R{sub o} ranging from 0.38 to 0.73 percent and the stage of clay-mineral diagenesis and expandibility indicate a thermally {open_quotes}cool{close_quotes} basin. Miocene Tyonek and Beluga Formations compose 65 percent (>4,300 m thick) of the Kenai Group. The Tyonek includes conglomeratic sandstones, siltstones, mudstones, coals, and carbonaceous shales, interpreted as braided- stream deposits. These fluvial deposits are interbecided with burrowed, lenticular, and flaser-bedded sandstones, siltstones, and mudstones, interpreted as tidal deposits. Tyonek framework conglomerates formed in wet alluvial fans incised on paleovalleys of the Chugach terrane. Coal-forming mires are well developed on abandoned braided-stream deposits. Tyonek drainages formed in high-gradient alluvial plains inundated by tides similar to environments in the modern upper Cook Inlet. The upper Miocene Beluga consists of sandstones, siltstones, mudstones, carbonaceous shales, and coals deposited in meandering (low sinuosity) and anastomosed fluvial systems. These fluvial deposits alternated vertically with deposits of coal-forming mires. The Beluga drainages formed in low-gradient alluvial plains. The high-gradient Tyonek alluvial plain was probably controlled by provenance uplift and eustatic change, whereas the low-gradient Beluga alluvial plain was influenced by subdued provenance uplift and rapid basin subsidence. Rapid sedimentation on both these low- and high-gradient alluvial plains, which kept up with subsidence, produced a thermally {open_quotes}cool{close_quotes} basin.

  19. Global cooling in the late Miocene- a precursor to northern hemisphere glaciation

    NASA Astrophysics Data System (ADS)

    Herbert, T.; Tzanova, A.; Lawrence, K. T.; Kelly, C.; Peterson, L.

    2013-12-01

    Very large changes in terrestrial environments, floras, and faunas occurred in late Miocene (10-6 Ma) time. However, marine stable isotopes (?18O, ?13C) do not register signs of accelerated global change. We present here alkenone-based evidence that ocean temperatures from 10 mid-latitude and high latitude locations show coherent and large cooling in late Miocene time. Cooling probably began at ~14 Ma, coincident with the final 'refrigeration' of Antarctica, was clearly well underway by 10 Ma and intensified between ~8 to 6 Ma. The cooling can be reconciled with marine oxygen isotopic data if it involved large sea surface changes but did not reach the threshold of significant continental ice buildup in the northern hemisphere. In magnitude and intensity, the global late Miocene ocean temperature drop, however, dwarfs the better-known latest Pliocene-Pleistocene evolution of climate over the Northern Hemisphere ice ages. It was accompanied by aridification on land and the appearance of ephemeral Arctic sea ice and/or small scale glaciations of the northern hemisphere in latest Miocene and early Pliocene time. It is hard to find a mechanism other than a strong late Miocene reduction in atmospheric CO2 levels as originally suggested by Cerling and colleagues (1993) to explain the ensemble of marine and terrestrial data.

  20. Strong winter monsoon wind causes surface cooling over India and China in the Late Miocene

    NASA Astrophysics Data System (ADS)

    Tang, H.; Eronen, J. T.; Kaakinen, A.; Utescher, T.; Ahrens, B.; Fortelius, M.

    2015-01-01

    Modern Asian winter monsoon characterised by the strong northwesterly wind in East Asia and northeasterly wind in South Asia, has a great impact on the surface temperature of the Asian continent. Its outbreak can result in significant cooling of the monsoon region. However, it is still unclear whether such an impact existed and is detectable in the deep past. In this study, we use temperature reconstructions from plant and mammal fossil data together with climate model results to examine the co-evolution of surface temperature and winter monsoon in the Late Miocene (11-5 Ma), when a significant change of the Asian monsoon system occurred. We find that a stronger-than-present winter monsoon wind might have existed in the Late Miocene due to the lower Asian orography, particularly the northern Tibetan Plateau and the mountains north of it. This can lead to a pronounced cooling in southern China and northern India, which counteracts the generally warmer conditions in the Late Miocene compared to present. The Late Miocene strong winter monsoon was characterised by a marked westerly component and primarily caused by a pressure anomaly between the Tibetan Plateau and Northern Eurasia, rather than by the gradient between the Siberian High and the Aleutian Low. As a result, the close association of surface temperature with winter monsoon strength on inter-annual scale as observed at present may not have established in the Late Miocene.

  1. Miocene-Pliocene transition in the southern Cyprus basins: The sedimentary expression of regional tectonic events

    SciTech Connect

    Orzag-Sperber, F.; Rouchy, J.M. )

    1988-08-01

    In the southern part of Cyprus, a Maastrichtian-Pleistocene sedimentary area fringes Troodos Mountain, a fragment of an ancient crust. During the Neogene, three basins formed in this area: Polemi, Pissouri, and Psematismenos. A deep marine condition has prevailed since the Maastrichtian. During the Paleocene and early Miocene, the sea gradually become shallower until the Messinian, where the most spectacular sedimentary event concerns the deposition of evaporites contemporaneous with other Mediterranean evaporites. Some sedimentary phenomena express the tectonic instability during the upper Miocene. A well-known tectonic event affecting the east Mediterranean region generally referred to as the Miocene-Pliocene phase occurs at the Miocene-Pliocene limit. Recent sedimentological studies indicate this event is in fact complex. The Tortonian-lower Pliocene period is marked by a constraint involving an N20 distension in the Polemi and Pissouri basins and an N100 distension in the Psematismenos basin. Sedimentologic studies have demonstrated three tectonic pulsations during the Messinian prior to the Pliocene transgression. These are expressed by two episodes of seismic brecciation and a paleoemersion indicated by paleosols and detrital discharges. These phenomena suggest brief tectonic instability during the Messinian. Microtectonic studies reveal that the main change in tectonic constraint does not coincide with the Miocene-Pliocene contact but occurs at the top of the lower Pliocene.

  2. Molluscan evidence for early middle Miocene marine glaciation in southern Alaska

    USGS Publications Warehouse

    Marincovich, L., Jr.

    1990-01-01

    Profound cooling of Miocene marine climates in southern Alaska culminated in early middle Miocene coastal marine glaciation in the northeastern Gulf of Alaska. This climatic change resulted from interaction of the Yakutat terrane with southern Alaska beginning in late Oligocene time. The ensuing extreme uplift of the coastal Chugach and St. Elias Mountains resulted in progressive regional cooling that culminated in coastal marine glaciation beginning in the early middle Miocene (15-16 Ma) and continuing to the present. The counterclockwise flow of surface water from the frigid northeastern Gulf of Alaska resulted in a cold-temperate shallow-marine environment in the western Gulf of Alaska, as it does today. Ironically, dating of Gulf of Alaska marine glaciation as early middle Miocene is strongly reinforced by the presence of a few tropical and subtropical mollusks in western Gulf of Alaska faunas. Shallow-marine waters throughout the Gulf of Alaska were cold-temperate to cold in the early middle Miocene, when the world ocean was undergoing peak Neogene warming. -Author

  3. Paleomagnetism of the Ishikoshi Andesite: a Middle Miocene paleomagnetic pole for northeastern Japan and tectonic implications

    NASA Astrophysics Data System (ADS)

    Hoshi, Hiroyuki; Teranishi, Yuki

    2007-07-01

    To determine a Middle Miocene paleomagnetic pole for northeastern Japan and discuss its tectonic implications, we obtained new paleomagnetic results from Middle Miocene (about 14 Ma) dacite and andesite flows of the Ishikoshi Andesite. Characteristic remanent magnetizations were isolated from 12 lava sites by means of detailed alternating field and thermal demagnetizations. Analysis of demagnetization results and rock magnetic experiments indicated that magnetite or Ti-poor titanomagnetite is the main magnetic carrier. We obtained a formation mean direction ( D = 9.2°, I = 65.9°, α95 = 7.3°, k = 40.5, N = 11) and compared it with published paleomagnetic results from other areas of northeastern Japan to discuss tectonic rotation. This comparison provided a mean paleomagnetic pole (85.9°N, 236.6°E, A 95 = 6.2°, K = 115.9, N = 6) that we consider represents the Middle Miocene pole for northeastern Japan. It is statistically indistinguishable from coeval poles for southwestern Japan, South Korea, and northern China, and we therefore conclude that northeastern Japan as a whole has not been subjected to tectonic rotation since the Middle Miocene. A reassessment of geologic and paleomagnetic data suggests that a previous model of the Late Miocene or later counterclockwise rotation of northeastern Japan is based on tilt-uncorrected paleomagnetic directions from tilted rock units.

  4. Oligocene-Miocene Sr-isotope stratigraphy: Examples from eastern North America

    SciTech Connect

    Sugarman, P.J. ); Owens, J.P.; Gibson, T.G.; McCartan, L. ); Feigenson, M.D. )

    1994-03-01

    Sr-isotopic age estimates from the coastal plain in New Jersey, Maryland Virginia, and Florida have allowed correlation of upper Oligocene-Miocene stratigraphic sequences with an accuracy of [+-] 0.5--2.0 m.y. The upper Oligocene sequence mapped in New Jersey has an age range of 28.7--24.2 Ma, and is tentatively correlated with the Old Church Formation in Virginia. Sr-isotope age estimates of 28.6--25.3 in the lower part of the Arcadia Formation in Florida provide a chronostratigraphic correlation with the upper Oligocene, N.J. sequence. Miocene Sr-isotopic correlations are better constrained by improved age resolution of [+-]1 m.y. and less in the Miocene. The uppermost lower Miocene sequence in N.J. with Sr-isotopic age estimates of 17.4--15.5 Ma, can be correlated with the Calvert Formation in Maryland and the upper part of the Arcadia Formation in Florida based on Sr-isotopic correlations. The uppermost calcareous marine sequence in New Jersey is lower middle Miocene, with a Sr-isotopic age range of 13.6--12.2 Ma. This sequence is correlative with the Choptank Formation in Maryland. The St. Mary's Formation in Maryland has a Sr-isotopic age range of 10--9.6 Ma, and may be equivalent to the Cohansey Formation in New Jersey.

  5. Organic geochemical evaluations of bituminous rock and coals in Miocene Himmetoglu basin (Bolu, Turkey)

    SciTech Connect

    Sari, A.; Geze, Y.

    2008-07-01

    The studied area is a lake basin located in Bolu basin in Turkey. In the basin, from Upper Cretaceous to Upper Miocene 3,000-m thickness sediments were deposited. Upper Miocene Himmetoglu formation consisted of sandstone, claystone, and marl. To the middle level of the formation are located coal, bituminous limestone, and bituminous shales. In the basin, there are two coal beds whose thicknesses range from 1 to 13 m. The coals are easily breakable and black in color. In the coal beds exists some bituminous limestone and bituminous shales, and their thicknesses are between 5 and 45 cm. The amount of organic matter of the bituminous rocks from the Upper Miocene Himmetoglu formation are between 6.83 and 56.34 wt%, and the amount of organic matter of the bituminous limestone from the formation are between 13.58 and 57.16 wt%. These values indicate that these rocks have very good source potential. According to hydrogen index (HI), S2/S3, HI-T{sub max}, and HI-OI (oxygen index) parameters, kerogen types of the bituminous rocks and coals belonging to Upper Miocene Himmetoglu formation are Type I, Type II, and Type III. In accordance with HI, S2/S3, HI-T{sub max}, and HI-OI parameters, the bituminous rocks and coals from the Upper Miocene Himmetoglu formation are mostly immature.

  6. Distribution history and climatic controls of the Late Miocene Pikermian chronofauna

    PubMed Central

    Eronen, Jussi T.; Ataabadi, Majid Mirzaie; Micheels, Arne; Karme, Aleksis; Bernor, Raymond L.; Fortelius, Mikael

    2009-01-01

    The Late Miocene development of faunas and environments in western Eurasia is well known, but the climatic and environmental processes that controlled its details are incompletely understood. Here we map the rise and fall of the classic Pikermian fossil mammal chronofauna between 12 and 4.2 Ma, using genus-level faunal similarity between localities. To directly relate land mammal community evolution to environmental change, we use the hypsodonty paleoprecipitation proxy and paleoclimate modeling. The geographic distribution of faunal similarity and paleoprecipitation in successive timeslices shows the development of the open biome that favored the evolution and spread of the open-habitat adapted large mammal lineages. In the climate model run, this corresponds to a decrease in precipitation over its core area south of the Paratethys Sea. The process began in the latest Middle Miocene and climaxed in the medial Late Miocene, about 7–8 million years ago. The geographic range of the Pikermian chronofauna contracted in the latest Miocene, a time of increasing summer drought and regional differentiation of habitats in Eastern Europe and Southwestern Asia. Its demise at the Miocene-Pliocene boundary coincides with an environmental reversal toward increased humidity and forestation, changes inevitably detrimental to open-adapted, wide-ranging large mammals. PMID:19571012

  7. Early Miocene Antarctic glacial history: new insights from heavy mineral analysis from ANDRILL AND-2A drill core sediments

    NASA Astrophysics Data System (ADS)

    Iacoviello, Francesco; Giorgetti, Giovanna; Turbanti Memmi, Isabella; Passchier, Sandra

    2015-04-01

    The present study deals with heavy mineral analysis of late Early Miocene marine sediments recovered in the McMurdo Sound region (Ross Sea, Antarctica) during the ANDRILL—SMS Project in 2007. The main objective is to investigate how heavy mineral assemblages reflect different source rocks and hence different provenance areas. These data contribute to a better understanding of East Antarctica ice dynamics in the Ross Sea sector during the Early Miocene (17.6-20.2 Ma), a time of long-term global warming and sea level rise. The AND-2A drill core recovered several stratigraphic intervals that span from Early Miocene to Pleistocene and it collected a variety of terrigenous lithologies. The heavy mineral assemblages of the lower 650-m-thick sedimentary succession were analyzed through SEM observations and SEM-EDS microanalyses on heavy mineral grains. The heavy mineral analysis shows that the sediments are a mix of detritus dominated by McMurdo Volcanic Group sources most likely located in the present-day Mount Morning area (Proto-Mount Morning) with minor contribution from Transantarctic Mountains source rocks located west of the drill site. The heavy mineral assemblages in Interval 1 indicate that between 20.2 and 20.1 Ma, the grounding line of the ice sheet advanced to a position near the present-day Mount Morning volcanic center. During deposition of Interval 2 (20.1-19.3 Ma), the ice sheet most likely experienced a dynamic behavior with interval of ice advance alternating with periods of ice retreat, while Interval 3 (19.3-18.7 Ma) records further retreat to open water conditions. A dynamic behavior is noted in Interval 4 (18.7-17.6 Ma) with a decreasing contribution of materials derived from the basalts of the Mount Morning volcanic center located to the south of the drill site and a consequent increasing contribution of materials derived from the Transantarctic Mountains to the west of the drill site.

  8. First Miocene rodent from Lebanon provides the 'missing link' between Asian and African gundis (Rodentia: Ctenodactylidae)

    PubMed Central

    López-Antoñanzas, Raquel; Knoll, Fabien; Maksoud, Sibelle; Azar, Dany

    2015-01-01

    Ctenodactylinae (gundis) is a clade of rodents that experienced, in Miocene time, their greatest diversification and widest distribution. They expanded from the Far East, their area of origin, to Africa, which they entered from what would become the Arabian Peninsula. Questions concerning the origin of African Ctenodactylinae persist essentially because of a poor fossil record from the Miocene of Afro-Arabia. However, recent excavations in the Late Miocene of Lebanon have yielded a key taxon for our understanding of these issues. Proafricanomys libanensis nov. gen. nov. sp. shares a variety of dental characters with both the most primitive and derived members of the subfamily. A cladistic analysis demonstrates that this species is the sister taxon to a clade encompassing all but one of the African ctenodactylines, plus a southern European species of obvious African extraction. As such, Proafricanomys provides the 'missing link' between the Asian and African gundis. PMID:26250050

  9. Miocene non-marine diatoms from the western Cordillera basins of northern Peru

    USGS Publications Warehouse

    Fourtanier, E.; Gasse, F.; Bellier, O.; Bonhomme, M.G.; Robles, I.

    1993-01-01

    Diatom assemblages are documented from diatomite layers of two Miocene fluvio-lacustrine units from the basins of the western Cordillera of northern Peru: the Namora Formation and the Cajabamba Formation. Emphasis is given to taxa of particular stratigraphic interest. The diatom assemblages indicate for the Namora Formation the occurrence of swampy conditions with very dilute, low alkalinity water. The diatom assemblages of the Cajabamba Formation reflect the occurrence of fresh, slightly alkaline, eutrophic lakes with deep water in some samples, and swampy conditions with relatively high salt content in other samples. The Namora formation is late Miocene in age based on the diatom assemblages and radiometric analyses. The diatom layers of the Cajabamba Formation are dated as late middle to early late Miocene. -from Authors

  10. Major Mid-Miocene Climate Change In The Transantarctic Mountains

    NASA Astrophysics Data System (ADS)

    Ashworth, A. C.; Lewis, A. R.; Marchant, D. R.

    2007-12-01

    Independent lines of evidence from paleoecology, glacial geology and marine isotopes indicate major climate change in the Dry Valley sector of the Transantarctic Mountains (TAM) at c.14 Ma. A fossil assemblage of pollen and spores, freshwater diatoms, ostracods, mosses, and insect remains has been recovered from lacustrine sediments preserved in a small morainic lake basin in the western Olympus Range. The diatom assemblage indicates that the lake existed for >103yr and was ice-free during summers. Based on the moss and insect fossils the minimum mean summer temperature (MST- Dec-Feb) was 2C but could have been as high as 5C. Today at the site the MST is c. -15C. The lake-marginal vegetation was a sparse tundra dominated by mosses and liverworts. Based on pollen, Nothofagus (southern beech) was part of the lowland regional vegetation and individual dwarfed shrubs may have grown on the slopes surrounding the lake basin. The age of the deposits is well-constrained by an 40Ar/39Ar age of 14.11 0.11 Ma from an in situ volcanic ash within related lacustrine sediments. Based on an independent study of the glacial stratigraphy of the western Wright and McKelvey valleys, diamictites of a wet-based glacial regime had been replaced by those of cold-based regime by 13.85 0.03 Ma. The drop in temperatures and the cessation of meltwater at c. 14 Ma would have caused the regional extinction of all plant and insect life with the exception of the hardiest of soil-dwelling organisms. Paleobotanical evidence indicates that Antarctica had likely been vegetated throughout the Cenozoic, with forests replaced by tundra during the early Oligocene. The mid-Miocene extinction marks the end of tundra in the interior of Antarctica and its replacement by the polar desert biota which exists today. Changes in ?18O and Mg/Ca ratios from different sectors of the Southern Ocean indicate sea surface temperature cooling and ice sheet growth between 13.8 - 14.2 Ma. The close correlation of events in these marine records with the glaciological and biological records from the Dry Valleys strongly suggests that they are part of a major hemispheric or global climatic event.

  11. Ramu basin, Papua New Guinea: A record of late Miocene terrane collision

    SciTech Connect

    Cullen, A.B.

    1996-05-01

    The Ramu basin lies along a plate boundary where the Finisterre terrane is colliding with the Indo-Australian plate. Estimates for the age of initial collision range from early Miocene to middle Pliocene. Two unsuccessful wells (Keram 1 and Tsumba 1) drilled to basement and two-dimensional seismic data show that folded and faulted early to middle Miocene carbonates and clastics (the Wogamush sequence) are overlain by relatively undeformed Pliocene marine clastics (the Wewak sequence) along a regional unconformity. The pre-Pliocene section, which is at the crux of resolving the age of initial collision, has been correlated previously to the Finisterre terrane. Clastics within that section, derived from older terranes south of the basin, imply an early Miocene age for collision. I propose that Miocene sedimentary and volcanic rocks in the two wells are correlative with the Wogamush beds of the Maramuni arc. The Ramu basin can then be viewed as having a two-stage evolution. During the Miocene, the basin was part of the Maramuni arc, the polarity of which is unresolved. A collisional successor basin developed in the late Miocene as the Finisterre terrane (Adelbert block) collided with the arc. Thrust faults on the northeastern side of the basin, truncated by a regional unconformity, are interpreted to mark the suture of the Adelbert block. A northern earliest Pliocene sediment source for the basal Wewak sequence was probably the Finisterre terrane, but multiple source areas are inferred for the rest of that sequence. Middle Pliocene inversion of the basin`s northeastern flank, characterized by reverse faulting and forced folding, is attributed to plate boundary reorganization caused by rifting in the Bismarck Sea. The Ramu basin has numerous untested structures related to both collision and basin inversion. Gas-prone source rocks are present, but are largely immature. Reservoir and charge considerations place the Ramu basin in the very high risk sector for exploration.

  12. Eocene and miocene rocks off the northeastern coast of the United States

    USGS Publications Warehouse

    Gibson, T.G.

    1965-01-01

    A grab sample from a depth of 1675 m at a point south of Cape Cod contains early Eocene planktonic Foraminifera and is correlated with the Globorotalia rex zone of Trinidad. The assemblage indicates a depth comparable to that existing today. Regional relations suggest that the Cretaceous and Eocene deposits deepen to the west toward New Jersey. Two mollusk-bearing blocks dredged from the northern side of Georges Bank are correlative with the Miocene Yorktown Formation. Rocks from two other stations are probably Miocene. Benthonic Foraminifera in one sample indicate deposition in cool temperate waters of less than 60 m depth. ?? 1965.

  13. A giant termite from the Late Miocene of Styria, Austria (Isoptera)

    NASA Astrophysics Data System (ADS)

    Engel, Michael S.; Gross, Martin

    2009-02-01

    A giant termite is described and figured from the Late Miocene of the Styrian Basin in southeastern Austria. Gyatermes styriensis gen. n. et sp. n. is represented by a relatively complete forewing, with basal scale. The fossil approximates in size the largest of all termites today and is the largest fossil termite on record. The presence of this species in the Late Miocene fauna of Europe indicates that climatic conditions were appropriate for the persistence of species and colonies requiring relatively stable, warm conditions. The genus is primitive in overall features but shares some similarity with the dampwood termites.

  14. Early Miocene ostracods from the Sadovi section (Mt Poe\\vska gora, Croatia)

    NASA Astrophysics Data System (ADS)

    Hajek-Tadesse, Valentina; Belak, Mirko; Sremac, Jasenka; Vrsaljko, Davor; Wacha, Lara

    2009-06-01

    The study of the Early Miocene (Late Ottnangian/Early Karpatian) ostracod fauna from the Sadovi section (Mt Poe\\vska gora, Croatia) led to several results concerning Neogene paleobiogeography and paleoecology. Brackish deposits of Late Ottnangian and Early Karpatian age have been recognized for the first time in the North Croatian Basin. These deposits indicate the first marine ingression into the Early Miocene lake in this area. Twenty-nine ostracod species were determined, including the new taxa Fabaeformiscandona slavonica nov. sp. and Herpetocypris sadovii nov. sp.

  15. Amber from western Amazonia reveals Neotropical diversity during the middle Miocene

    PubMed Central

    Antoine, Pierre-Olivier; De Franceschi, Dario; Flynn, John J.; Nel, André; Baby, Patrice; Benammi, Mouloud; Calderón, Ysabel; Espurt, Nicolas; Goswami, Anjali; Salas-Gismondi, Rodolfo

    2006-01-01

    Tertiary insects and arachnids have been virtually unknown from the vast western Amazonian basin. We report here the discovery of amber from this region containing a diverse fossil arthropod fauna (13 hexapod families and 3 arachnid species) and abundant microfossil inclusions (pollen, spores, algae, and cyanophyceae). This unique fossil assemblage, recovered from middle Miocene deposits of northeastern Peru, greatly increases the known diversity of Cenozoic tropical–equatorial arthropods and microorganisms and provides insights into the biogeography and evolutionary history of modern Neotropical biota. It also strengthens evidence for the presence of more modern, high-diversity tropical rainforest ecosystems during the middle Miocene in western Amazonia. PMID:16950875

  16. Miocene Blanca Fan, Northern Channel Islands, California: Small fans reflecting tectonism and volcanism

    NASA Astrophysics Data System (ADS)

    McLean, Hugh; Howell, D. G.

    1984-06-01

    Blanca fan is a submarine fan composed of Miocene volcaniclastic strata. Parts of the fan system are exposed on Santa Cruz and Santa Rosa Islands, and possibly correlative strata crop out on San Miguel and Santa Catalina Islands. The Blanca fan and underlying breccia reflect regional transcurrent faulting in the California Continental Borderland and development of a system of rapidly subsiding basins and uplifted linear ridges during early and middle Miocene time. Erosion of uplifted crystalline basement rocks followed by the onset of silicic volcanism created linear sediment sources for the alluvial and submarine fans, respectively.

  17. An age for Kajong, a Miocene fossil site east of Lake Turkana, Kenya

    NASA Astrophysics Data System (ADS)

    Brown, Francis H.; Jicha, Brian R.; Leakey, R. E.

    2016-02-01

    The Kajong Formation in Marsabit District, northern Kenya has yielded a Miocene mammalian fauna consisting of nine taxa. It is capped by a basalt 40Ar/39Ar dated at 19.1 ± 0.1 Ma, and a volcanic clast from a conglomerate within the formation yielded an age of 20.3 Ma, only slightly older. The entire fauna from this site thus lies close to the base of the Miocene Epoch and is older than 19.2 Ma. The site has yielded some of the oldest examples of Archaeobelodon filholi, Prodeinotherium hobleyi, and Gomphotherium sp. in east Africa.

  18. Stratigraphical investigations on a new Miocene fossil-bearing sequence in Central Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Kaakinen, Anu; Aziz, Hayfaa Abdul; Passey, Benjamin H.; Zhang, Zhaoqun; Liu, Liping; Krijgsman, Wout; Fortelius, Mikael

    2014-05-01

    Central Inner Mongolia has been an area of great paleontological interest since the beginning of the 20th century. Although the area has produced numerous diverse collections of Miocene faunas, fossil records from the early Miocene of Inner Mongolia are relatively rare. The localities occur mainly as scattered faunal horizons and their stratigraphy is challenging owing to lack of continuous vertical exposures. Consequently, most age estimations of these Miocene sites are based on paleontological evidence alone, with very few sites having been dated independently based on paleomagnetics. The Damiao site in Siziwang Qi, Inner Mongolia, was discovered in 2006, and during the following four years extensive field activities were undertaken. The focus was on paleontological studies and on the stratigraphy of the Neogene sediments. The field survey led to the recovery of approximately 30 new fossiliferous localities, which have produced a rich mammalian fauna, including pliopithecid remains. The bulk of the vertebrate fossils and localities have been recovered from three main fossil horizons. We have interpreted the Damiao sequence as the remains of a fluvio-lacustrine system comprising channels, subaerially exposed floodplains and ephemeral/marginal lacustrine environments. This study presents the litho- and magnetostratigraphy of the Damiao area and provides age estimations for the important fossil-bearing localities. The two local stratigraphic sections measured and sampled for paleomagnetic analysis coincide with important vertebrate fossil localities. The western section is about 30 m thick and includes fossil locality DM16 while the eastern section spans up 40 m and comprises localities DM01 and DM02. The paleomagnetic results and faunal evidence suggest a correlation in the magnetozones C6Ar through C5r with an age range of ca 21 to 11 Ma. The interval of reversed polarity at the base of the section (C6Ar) coincides with fossil locality DM16. The pliopithecid locality DM01 represents late middle Miocene and has an age estimate of about 12 Ma while the locality DM02 represents earliest late Miocene with an age estimate of about 11.6- 11.7 Ma. Our magnetostratigraphic results confirm that the Damiao strata constitute one of the most continuous sequences in Inner Mongolia with early, middle and late Miocene fossil faunas in stratigraphic superposition. The results also provide constraints on the paleoenvironmenal evolution and bioevents of the area. The occurrence of pliopithecid primates in the middle Miocene of Inner Mongolia suggests relatively humid habitats and challenges the scenarios suggesting arid and highly seasonal conditions for Central Asia since Early Miocene.

  19. Partial record of a Miocene geomagnetic field excursion: Paleomagnetic data from the Paiute Ridge volcanic center, southern Nevada

    SciTech Connect

    Ratcliff, C.D.; Geissman, J.W.; Perry, F.V. ); Crowe, B.M. )

    1993-04-01

    In the Palute Ridge area, northern Halfpint Range, a complex system of late Miocene (about 8.5 Ma) intrusive and extrusive alkaline mafic rocks crops out over an area of about 25km[sup 2]. Post-magmatic faulting and erosion have resulted in excellent exposure of this sub-volcanic center, allowing for a detailed study of mechanisms and timing of magma emplacement. Paleomagnetic data have been obtained from over 50 sites in mafic rocks, and host ash-flow tuffs and carbonate strata, to better understand the duration of magmatic activity. Magnetizations, isolated in progressive alternating field and thermal demagnetization, for most of the sites at Palute Ridge deviate significantly from expected directions for a time-averaged late Miocene field. Demagnetization data show that there are two types of sample behavior. First, samples with close to expected reverse polarity directions (e.g., the chilled margin of a sill, D=209.2, l=[minus]36.4, [alpha]95=13.2, N=5, k=34.8). Second, and far more common, are samples giving magnetizations of southwest to northwest declination, with both shallow to moderate positive and negative inclination. Within this second grouping are several sites, including syenite pods which differentiated in situ from a large lopolith, having mean declinations that are due west and of shallow inclination. Contact tests performed at several sites are positive and show a clear correlation between sample position and isolated remanence direction. The authors preferred interpretation of the anomalously directed magnetization is that these rocks acquired a TRM during either a high amplitude excursion, or the transitional portion of a field reversal. Thermal models based on larger intrusions [+-] 10m thick at Paiute Ridge indicate that the magmas could cool through estimated magnetization blocking temperatures within weeks or months of emplacement.

  20. Characterizing the dispersal and distribution shapes of the geomagnetic field directions of the Late Miocene Columbia River Basalts

    NASA Astrophysics Data System (ADS)

    Dominguez, A. R.; Van Der Voo, R.

    2011-12-01

    This study comprises 118 discrete volcanic flows from the Late Miocene in the eastern Columbia River Basalt (CRB) Group with the aim of testing the distributions of the geomagnetic field directions, as predicted by various geomagnetic models. This is important because little is known empirically about the behavior of the geomagnetic field before the last 5 million years. The results of this study will allow us not only to extend the temporal coverage of geomagnetic field models, but also allow for potential improvements in these models. The rock magnetic analysis of the samples for this collection shows that the primary magnetic directions are uniformly carried by titanomagnetite throughout all the sites; some minor amounts of hematite are present, most likely formed during weathering. Thus, the magnetic behavior of the samples is caused by changes in the magnetic field and not due to changes in magnetic mineralogy. The paleomagnetic directions of the flows show southerly and up (N: 45, Dec: 180.1, Inc: -64.5, k: 25.7, alpha-95: 4.3) and northerly and down site means (N: 57, Dec: 6.3, Inc: 62, k: 29, alpha-95: 3.6). For reference, the local inclination of the geocentric co-axial dipole field is about 64 degrees. Furthermore, deviating directions are also present, possibly due to excursions as part of secular variation, or as intermediate transitions between reversed and normal polarity intervals. No new rock ages were necessary for this study since the CRB has undergone extensive geochronological study with high-quality, reproducible results. Additionally, integrating the ages of the flows and their corresponding paleomagnetic directions will allow us to observe the evolution of the paleosecular variation (PSV) for the Late Miocene, which can be compared with the published characteristics of the geomagnetic field in the last 5 million years.

  1. Miocene and Pliocene dominated diversification of the lichen-forming fungal genus Melanohalea (Parmeliaceae, Ascomycota) and Pleistocene population expansions

    PubMed Central

    2012-01-01

    Background Factors promoting diversification in lichen symbioses remain largely unexplored. While Pleistocene events have been important for driving diversification and affecting distributions in many groups, recent estimates suggest that major radiations within some genera in the largest clade of macrolichens (Parmeliaceae, Ascomycota) vastly predate the Pleistocene. To better understand the temporal placement and sequence of diversification events in lichens, we estimated divergence times in a common lichen-forming fungal genus, Melanohalea, in the Northern Hemisphere. Divergence times were estimated using both concatenated gene tree and coalescent-based multilocus species tree approaches to assess the temporal context of major radiation events within Melanohalea. In order to complement our understanding of processes impacting genetic differentiation, we also evaluated the effects of Pleistocene glacial cycles on population demographics of distinct Melanohalea lineages, differing in reproductive strategies. Results We found that divergence estimates, from both concatenated gene tree and coalescent-based multilocus species tree approaches, suggest that diversification within Melanohalea occurred predominantly during the Miocene and Pliocene, although estimated of divergence times differed by up to 8.3 million years between the two methods. These results indicate that, in some cases, taxonomically diagnostic characters may be maintained among divergent lineages for millions of years. In other cases, similar phenotypic characters among non-sister taxa, including reproductive strategies, suggest the potential for convergent evolution due to similar selective pressures among distinct lineages. Our analyses provide evidence of population expansions predating the last glacial maximum in the sampled lineages. These results suggest that Pleistocene glaciations were not inherently unfavorable or restrictive for some Melanohalea species, albeit with apparently different demographic histories between sexually and vegetatively reproducing lineages. Conclusions Our results contribute to the understanding of how major changes during the Miocene and Pliocene have been important in promoting diversification within common lichen-forming fungi in the northern Hemisphere. Additionally, we provide evidence that glacial oscillations have influenced current population structure of broadly distributed lichenized fungal species throughout the Holarctic. PMID:22963132

  2. Provenance Analysis of Lower Miocene Sediments in the Lower Austrian Molasse Basin

    NASA Astrophysics Data System (ADS)

    Knierzinger, Wolfgang; Palzer, Markus; Wagreich, Michael

    2015-04-01

    In the Early Miocene (Late Ottnangian) a global drop of the sea level and the continuous rise of the Alps caused a regression of the Paratethys. During this time interval the Traisen Formation (formerly Oncophora beds) was deposited in the Lower Austrian Molasse Basin. These yellowish-brownish to greyish mica-rich and carbonate-free sands and silts with clayish interlayers were originally named after a brackish water bivalve ("Oncophora"- now Rzehakia). The southeastern part of the TF partly interfingers with finer sands of the Dietersdorf Formation (DF). The Pixendorf Group combines the TF and the DF [coarse sands, conglomerates, blocks] of the Upper Ottnangian lithostratigraphic units in Lower Austria. West to the Waschberg Zone a deeper-water environment (so called Oncophora beds in former literature, herein [informally] renamed to Wildendürnbach Member) with sediment gravity flows (turbidites, muddy/sandy slumps) is inferred from OMV well data. Examinations of these fine sandstones, silts and laminated pelites have been carried out on the basis of the Wildendürnbach-4 OMV drilling core. Analyses of the TF revealed rather homogenous heavy mineral assemblages, dominated by high amounts of garnet (~65%) and relatively high amounts of epidote/zoisite (~10%) and amphiboles (~10%). Conducted surveys point towards a primary influence of metamorphic (metapelitic) source rocks of Austroalpine Crystalline Complexes of the rising Eastern Alps. Heavy mineral analysis of the WDK-4 drilling core showed even higher amounts of garnet (~80%) combined with minor amounts of rutile, staurolite, apatite, epidote/zoisite, tourmalines, zircon and amphiboles. Consistent heavy mineral assemblages and chemical data (EMPA) suggest a stratigraphical correlation with the Křepice Formation and the Ždánice-Hustopeče Formation in the Czech Republic and sedimentary influence from the Western Carpathian Flysch Belt.

  3. Paleomagnetism, rock magnetism, and PIXE Analysis of Oligocene-Miocene sediments (Bennett County, South Dakota)

    NASA Astrophysics Data System (ADS)

    Karbalaei Saleh, F.; Martin, J.; Sidorovskaia, N.; Richter, C.; Hollerman, W. A.

    2013-12-01

    We present paleo- and rock magnetic results together with Particle Induced X-ray Emission (PIXE) data from an Oligocene-Miocene aged section in central South Dakota. Sediment samples recovered by the High-Plains Aquifer Drilling Program of the South Dakota Geological Survey retrieved well-preserved core material for paleomagnetic and geochemical analysis. A 250 m long core was retrieved from the Tertiary Arikaree Group, which consists predominantly of fine-grained sandstones and limestones with interbedded silt and clay. Paleomagnetic and rock magnetic measurements were carried out at 30 cm resolution on more than 200 discrete samples, and geochemical analysis using PIXE at the Louisiana Accelerator Center on twenty selected samples, with the goal of extracting a geomagnetic polarity time scale and to reconstruct paleoenvironmental conditions. Stepwise demagnetization of the natural remnant magnetization yields excellent to poor demagnetization behavior, with a viscous isothermal remnant magnetization drilling overprint effectively removed during the 20 mT demagnetization step. Paleomagnetic data are characterized by normal and reversed inclinations, consistent with the site position in South Dakota. Magnetic susceptibility measurements of the sediments correlate well with the observed changes in lithology. PIXE sample preparation procedures and calibration techniques to obtain absolute concentrations of heavy elements in the core samples are discussed. An empirical correlation between susceptibility measurements and concentration of the magnetic materials in the core obtained from PIXE will be presented. The results are promising in augmenting traditional paleomagnetic studies to develop a quantitative relationship between the measured magnetization and the concentration of magnetic materials needed for relative paleointensity studies. The PIXE analysis shows also potential in deciphering paleoenvironmental and paleoclimatic conditions during the deposition of the sedimentary section.

  4. Diagenetic gypsum related to sulfur deposits in evaporites (Libros Gypsum, Miocene, NE Spain)

    NASA Astrophysics Data System (ADS)

    Ort, Federico; Rosell, Laura; Anadn, Pere

    2010-07-01

    The Libros Gypsum is the thickest evaporite unit of the Miocene infill of the Teruel Basin in NE Spain. During the deposition of this unit, intense bacterial sulfate-reducing (BSR) activity in the lake depocenter generated a native sulfur deposit. Diagenetic gypsum resulted from subsequent sulfur oxidation. The different processes involved in these transformations were first investigated by Anadn et al. (1992). The present paper is concerned with this diagenetic gypsum from the stratigraphic, petrographic, isotopic and genetic points of view. Diagenetic gypsum occurs mainly as continuous or discontinuous layers, individual levels or lenses, irregular masses, nodules and micronodules, and veins. Its main textures are coarse-crystalline anhedral and fine-grained (alabastrine), both of which can replace any former lithology (carbonate, gypsum, and sulfur). The following sequence of processes and mineral/textural transformations is deduced: primary gypsum deposition BSR and biodiagenetic carbonate/H 2S production growth of native sulfur growth of diagenetic gypsum partial recrystallization of the diagenetic gypsum textures. The gypsification of the native sulfur generated two types of banded structures in the diagenetic gypsum: (1) concentric structures of centripetal growth, and (2) expansive, roughly concentric structures. In the first type, the gypsification operated from the outer boundaries towards the inner parts. In the second type, part of the carbonate hosting the sulfur was also gypsified (replaced/cemented). In the diagenetic gypsum, the ?34S values are in agreement with a native sulfur and H 2S provenance. The ?18O sulfate values, however, enable us to differentiate two main groups of values: one with positive values and the other with negative values. In the group of positive values, interstitial (evaporated) solutions participated in the sulfur oxidation; this process presumably occurred in a first oxidation stage during shallow-to-deeper burial of the Libros Gypsum unit. In the group of negative values, however, only meteoric waters participated in the oxidation, which presumably occurred in a second oxidation stage during the final exhumation of the unit. A third group of values is characterized by very high sulfur and oxygen values, suggesting that BSR residual solutions also participated in the oxidation processes locally. During the two oxidation stages, both the textural characteristics and the isotopic composition of the diagenetic gypsum indicate that gypsification operated as a multistadic process.

  5. Reflections on the Hawthorne Effect

    ERIC Educational Resources Information Center

    Merrett, Frank

    2006-01-01

    When researchers carry out an experiment, they do so in a systematic and regulated manner, attempting to note all of the circumstances and outcomes very carefully, so that they can come to some firm conclusions about causes and effects. Sometimes, however, unaccountable outcomes do occur. Researchers are clearly very interested in such events and

  6. The Miocene avifauna of the Li Mae Long locality, Thailand: systematics and paleoecology

    NASA Astrophysics Data System (ADS)

    Cheneval, Jacques; Ginsburg, Lonard; Mourer-Chauvire, Ccile; Ratanasthien, Benjavun

    The Miocene avifauna from Li Mae Long includes an anhinga, a heron, a new species of lesser flamingo, Phoeniconaias siamensis n. sp., two Anatidae, a Phasianidae, three Rallidae, and a Strigidae. The landscape indicated by the mammalian and avian faunas corresponds to a large swampy depression, with probably saline or alkaline waters, surrounded by humid forests, under a warm climate.

  7. A remarkable new pygmy grasshopper (Orthoptera, Tetrigidae) in Miocene amber from the Dominican Republic

    PubMed Central

    Heads, Sam W.; Thomas, M. Jared; Wang, Yinan

    2014-01-01

    Abstract A new genus and species of pygmy grasshopper (Orthoptera: Tetrigidae) is described from Early Miocene (Burdigalian) Dominican amber. Electrotettix attenboroughi Heads & Thomas, gen. et sp. n. is assigned to the subfamily Cladonotinae based on the deeply forked frontal costa, but is remarkable for the presence of tegmina and hind wings, hitherto unknown in this subfamily. PMID:25147472

  8. Anthracothere dental anatomy reveals a late Miocene Chado-Libyan bioprovince

    PubMed Central

    Lihoreau, Fabrice; Boisserie, Jean-Renaud; Viriot, Laurent; Coppens, Yves; Likius, Andossa; Mackaye, Hassane Taisso; Tafforeau, Paul; Vignaud, Patrick; Brunet, Michel

    2006-01-01

    Recent discovery of an abundant and diverse late Miocene fauna at Toros-Ménalla (Chad, central Africa) by the Mission Paléoanthropologique Franco-Tchadienne provides a unique opportunity to examine African faunal and hominid evolution relative to the early phases of the Saharan arid belt. This study presents evidence from an African Miocene anthracotheriid Libycosaurus, particularly well documented at Toros-Ménalla. Its remains reveal a large semiaquatic mammal that evolved an autapomorphic upper fifth premolar (extremely rare in Cenozoic mammals). The extra tooth appeared ≈12 million years ago, probably in a small northern African population isolated by climate-driven fragmentation and alteration of the environments inhabited by these anthracotheriids [Flower, B. P. & Kennett, J. P. (1994) Palaeogeogr. Palaeoclimatol. Palaeoecol. 108, 537–555 and Zachos, J., Pagani, M., Sloan, L., Thomas, E. & Billups, K. (2001) Science 292, 686–693]. The semiaquatic niche of Libycosaurus, combined with the distribution and relationships of its late Miocene species, indicates that by the end of the Miocene, wet environments connected the Lake Chad Basin to the Libyan Sirt Basin, across what is now the Sahara desert. PMID:16723392

  9. Anthracothere dental anatomy reveals a late Miocene Chado-Libyan bioprovince.

    PubMed

    Lihoreau, Fabrice; Boisserie, Jean-Renaud; Viriot, Laurent; Coppens, Yves; Likius, Andossa; Mackaye, Hassane Taisso; Tafforeau, Paul; Vignaud, Patrick; Brunet, Michel

    2006-06-01

    Recent discovery of an abundant and diverse late Miocene fauna at Toros-Ménalla (Chad, central Africa) by the Mission Paléoanthropologique Franco-Tchadienne provides a unique opportunity to examine African faunal and hominid evolution relative to the early phases of the Saharan arid belt. This study presents evidence from an African Miocene anthracotheriid Libycosaurus, particularly well documented at Toros-Ménalla. Its remains reveal a large semiaquatic mammal that evolved an autapomorphic upper fifth premolar (extremely rare in Cenozoic mammals). The extra tooth appeared approximately 12 million years ago, probably in a small northern African population isolated by climate-driven fragmentation and alteration of the environments inhabited by these anthracotheriids [Flower, B. P. & Kennett, J. P. (1994) Palaeogeogr. Palaeoclimatol. Palaeoecol. 108, 537-555 and Zachos, J., Pagani, M., Sloan, L., Thomas, E. & Billups, K. (2001) Science 292, 686-693]. The semiaquatic niche of Libycosaurus, combined with the distribution and relationships of its late Miocene species, indicates that by the end of the Miocene, wet environments connected the Lake Chad Basin to the Libyan Sirt Basin, across what is now the Sahara desert. PMID:16723392

  10. First record of Mesopithecus (Cercopithecidae, Colobinae) from the Miocene of the Iberian Peninsula.

    PubMed

    Alba, David M; Montoya, Plini; Pina, Marta; Rook, Lorenzo; Abella, Juan; Morales, Jorge; Delson, Eric

    2015-11-01

    We report dental remains of the extinct colobine monkey Mesopithecus from the Turolian (MN13, Late Miocene, ca. 6.23 Ma) locality of Venta del Moro (Valencia, Spain). They include most of the deciduous dentition and the unerupted germs of the first molars of a single infantile individual, as well as two lower left lateral incisors from two additional individuals. On the basis of morphometric comparisons, mainly based on the M1s, these remains are attributed to the Late Miocene species Mesopithecus pentelicus. They represent a significant addition to the knowledge of the deciduous dentition of this taxon, much less well-known than the permanent dentition. Although this genus was widely distributed from the Late Miocene through the Pliocene across Europe, southwestern Asia, Pakistan, and China, until now its occurence in the Late Miocene of the Iberian Peninsula had not been documented conclusively. Hence, the reported remains considerably enlarge southwestwards the known geographic distribution of Mesopithecus. The presence of this genus at Venta del Moro must be understood within the framework of the significant faunal turnover that took place in European faunas during the latest Turolian (the second Messinian mammalian dispersal), which is further documented at this locality by the occurrence of other eastern immigrants. At the same time, the presence of M. pentelicus at this site agrees well with previous paleoenvironmental and sedimentological evidence, indicating a lacustrine depositional environment with strong hydrologic seasonality. PMID:26553814

  11. Early to Middle Miocene vegetation and climate of Wilkes Land, Antarctica (IODP 318)

    NASA Astrophysics Data System (ADS)

    Salzmann, U.; Sangiorgi, F.; Bijl, P. K.; Pross, J.; Schouten, S.; Tauxe, L.; Bendle, J.; Brinkhuis, H.; Escutia, C.; IODP Expedition 318 Science Party

    2012-04-01

    The question of whether continental Antarctic climate was warm enough to support a substantial vegetation cover during the Neogene is of great significance to the ongoing controversial debate on the behaviour of Antarctic land ice during the Miocene-Pliocene transition from dynamic to persistent ice sheets. Here we present palynological results from a Miocene sediment record provided by the Integrated Ocean Drilling Program (IODP) Expedition 318 to the Wilkes Land margin (East Antarctica). The reconstructed vegetation changes are compared with climate estimates derived from dinoflagellate cysts and MBT/CBT organic palaeotemperature proxies. Analyses of pollen and spores indicate a low-diverse vegetation dominated by Podocarpus- and Nothofagus- trees and shrubs. Particular high Podocarpus percentages occur during the Middle Miocene Climatic Optimum (MMCO). For this time period MBT/CBT suggests a cool temperate climate with increased mean air temperatures (MAT). Dinoflagellate cyst assemblages, dominated by autotrophic species, are indicative of ice-free surface waters. After MMCO a subsequent decline in MAT is indicated by MBT and dinoflagellate cyst assemblages, though pollen percentages (e.g. Podocarpus/Nothofagus ratio) remain relatively stable. However, very high Nothofagus and low Podocarpus pollen percentages may suggest lower temperatures towards the end of the middle Miocene.

  12. Late Oligocene and Early Miocene Muroidea of the Zinda Pir Dome

    PubMed Central

    Lindsay, Everett H.; Flynn, Lawrence J.

    2016-01-01

    A series of Oligocene through Early Miocene terrestrial deposits preserved in the foothills of the Zinda Pir Dome of western Pakistan produce multiple, superposed fossil mammal localities. These include small mammal assemblages that shed light on the evolution of rodent lineages, especially Muroidea, in South Asia. Nine small mammal localities span approximately 28–19 Ma, an interval encompassing the Oligocene–Miocene boundary. The Early Miocene rodent fossil assemblages are dominated by muroid rodents, but muroids are uncommon and archaic in earlier Oligocene horizons. The Zinda Pir sequence includes the evolutionary transition to modern Muroidea at about the Oligocene–Miocene boundary. We review the muroid record for the Zinda Pir Dome, which includes the early radiation of primitive bamboo rats (Rhizomyinae) and early members of the modern muroid radiation, which lie near crown Cricetidae and Muridae. The Zinda Pir record dates diversification of modern muroids in the Indian Subcontintent and establishment by 19 Ma of muroid assemblages characteristic of the later Siwaliks. PMID:26681836

  13. Evidence for sediment fan deposition on outer Texas shelf during Miocene eustatic sea level highstands

    SciTech Connect

    Riese, W.C.; Olsen, R.S.; Rosen, R.N.

    1988-02-01

    Four types of data were reviewed in an attempt to clearly define the environments of deposition for reservoir sands in the Matagorda 668 field: well log curve shapes, seismic amplitude responses, micropaleontology, and thin section sedimentary petrology. All four lines of evidence support the interpretation that these lower Miocene sands were deposited as fan complexes.

  14. Abundance variations of benthic foraminifera in Upper Oligocene and Miocene strata of south Louisiana

    SciTech Connect

    Nunn, L.L.; Sen Gupta, B.K.

    1986-09-01

    Abundance variations of benthic foraminifera in some upper Oligocene and Miocene strata of south Louisiana were studied to evaluate trends of species dominance, associations, and faunal diversity. Fifty-seven well-cutting samples were obtained from eleven wells in six parishes: Vermilion, St. Mary, St. Martin, Assumption, Terrebonne, and Lafourche. In addition, core samples were obtained from two wells in Terrebonne Parish.

  15. Middle Miocene E-W tectonic horst structure of Crete through extensional detachment faults

    NASA Astrophysics Data System (ADS)

    Papanikolaou, D.; Vassilakis, E.

    2008-07-01

    Two east-west trending extensional detachment faults have been recognized in Crete, one with top-to-the-north motion of the hanging wall toward the Cretan Sea and one with top-to-the-south motion of the hanging wall toward the Libyan Sea. The east-west trending zone between these two detachment faults, which forms their common footwall, comprises a tectonic horst formed during Middle Miocene slip on the detachment faults. The detachment faults disrupt the overall tectono-stratigraphic succession of Crete and are localized along pre-existing thrust faults and along particular portions of the stratigraphic sequence, including the transition between the Permo-Triassic Tyros Beds and the base of the Upper Triassic-Eocene carbonate platform of the Tripolis nappe. By recognizing several different tectono-stratigraphic formations within what is generally termed the 'phyllite-quartzite', it is possible to distinguish these extensional detachment faults from thrust faults and minor discontinuities in the sequence. The deformation history of units within Crete can be summarized as: (i) compressional deformation producing arc-parallel east-west trending south-directed thrust faults in Oligocene to Early Miocene time (ii) extensional deformation along arc-parallel, east-west trending detachment faults in Middle Miocene time, with hanging wall motion to the north and south; (iii) Late Miocene-Quaternary extensional deformation along high-angle normal and oblique normal faults that disrupt the older arc-parallel structures.

  16. Pliocene and latest Miocene anisotropy of magnetic susceptibility (AMS) from the Wilkes Land margin (Invited)

    NASA Astrophysics Data System (ADS)

    Sugisaki, S.; Tauxe, L.; Iwai, M.; van de Flierdt, T.; Cook, C.; Jimenez, F. J.; Khim, B.; Patterson, M. 0; Mckay, R. M.; Passchier, S.; Roehl, U.; Gonzlez, J. J.; Escutia, C.

    2013-12-01

    During IODP Expedition 318, Sites U1359 and U1361 were drilled on the continental rise offshore the Wilkes Subglacial Basin to reconstruct the stability of the East Antarctic Ice Sheet (EAIS) during Neogene warm periods, such as the late Miocene and the early Pliocene. As the drilled core contains a complex history of compaction, erosion (thus hiatuses), and likely artificial disturbances, identifying these is important for reconstructing paleoenvironments. Anisotropy of magnetic susceptibility (AMS) is sensitive to lithological changes and differential compaction. At both sites, highly anisotropic layers correspond with turbidite units, lithologic boundaries and hiatuses. In places, it appears that low anisotropy is controlled by the bioturbated units and high productivity layers. Here we present a detailed study of the relationships between sediment compaction, based on AMS fabric variations in sedimentary records, and magnetic mineralogy. A clear correlation can be found between the degree of anisotropy and moisture content and diatom abundance during the Pliocene, but this pattern breaks down in the late Miocene. There are also strong rock magnetic indications for changes in the sources of the magnetic minerals throughout the Miocene to Pliocene. Furthermore, a significant difference exists between magnetic minerals at Sites U1359 and U1361. We will use our AMS and rock magnetic study to 1) characterize sediment compaction with biological productivity, and 2) detect the source of magnetic mineralogy throughout the late Miocene to Pliocene at both sites.

  17. Carbonate depositional environments and reservoir properties of the Miocene rocks, east Gulf of Suez, Egypt

    SciTech Connect

    Bakarat, M.A.K.; Kholief, M.M.

    1988-08-01

    Miocene carbonate rocks in six surface sections on the eastern side of the Gulf of Suez were carefully studied in the field, petrographically examined, and mineralogically analyzed using SEM and x-ray microanalysis for all elements. In general, reservoir quality of the Miocene carbonates was poor because of original composition and texture. Three different types of porosity were distinguished in the studied Miocene carbonates: primary (intergranular and moldic), secondary (leached), and fracture. Much of the porosity in the Miocene reservoirs is secondary; however, sometimes this secondary porosity may be reduced by compaction and/or precipitation of evaporites in fractures and pores. The authors conclude that the primary porosity of the carbonate rocks in the reef complex was eliminated by lithification and cementation; only secondary porosity remained. This secondary porosity developed in all environments (supratidal, intertidal, and subtidal), but the best porosity developed in the subtidal facies. This high porosity occurs because the dolomites in the subtidal facies are coarser and free from anhydrite cement, whereas in supratidal and intertidal facies the dolomites are finer and their porosity is plugged by secondary anhydrite cement.

  18. The Miocene Nullarbor Limestone, southern Australia; deposition on a vast subtropical epeiric platform

    NASA Astrophysics Data System (ADS)

    O'Connell, Laura G.; James, Noel P.; Bone, Yvonne

    2012-05-01

    The early to middle Miocene Nullarbor Limestone forms the vast, karsted Nullarbor Plain in southern Australia, and may be the most extensive Miocene carbonate deposit described to date. These carbonates were deposited at southern paleolatitudes of ~ 40S and are interpreted to be subtropical to warm-temperate in character because of the presence of certain genera of tropical coralline algae (rhodoliths and articulated types), large benthic foraminifera, tropical molluscs, zooxanthellate corals, and micrite envelopes. Facies are dominated by skeletal grainstones and floatstones that accumulated in three interpreted paleoenvironments: (1) seagrass banks (upper photic zone), (2) rhodolith pavements (lower photic zone), and (3) open seafloors (lower photic to subphotic zone). A decrease of tropical components from west to east across the platform implies that warm oceanic currents (possibly related to a proto-Leeuwin Current), as well as a period of warm climate (Miocene Climatic Optimum), resulted in subtropical deposition at southern latitudes. The Southern Ocean extended inboard ~ 450 km from the shelf edge during Nullarbor Limestone deposition, but interpreted paleodepths did not extend much below the base of the photic zone. A small slope angle (~ 0.02) over a wide shelf (~ 300,000 km2) implies deposition on an epeiric platform or epeiric ramp. A Miocene barrier reef was likely coeval with Nullarbor Limestone deposition. Therefore, the inboard portion of the Nullarbor Limestone can be considered part of an extensive back-reef lagoon system on a rimmed epeiric platform, perhaps attaining a size similar to the modern Great Barrier Reef system.

  19. Middle Miocene vertebrates from the Amazonian Madre de Dios Subandean Zone, Per

    NASA Astrophysics Data System (ADS)

    Antoine, Pierre-Olivier; Roddaz, Martin; Brichau, Stphanie; Tejada-Lara, Julia; Salas-Gismondi, Rodolfo; Altamirano, Ali; Louterbach, Mlanie; Lambs, Luc; Otto, Thierry; Brusset, Stphane

    2013-03-01

    A new middle Miocene vertebrate fauna from Peruvian Amazonia is described. It yields the marsupials Sipalocyon sp. (Hathliacynidae) and Marmosa (Micoureus) cf. laventica (Didelphidae), as well as an unidentified glyptodontine xenarthran and the rodents Guiomys sp. (Caviidae), Scleromys sp., cf. quadrangulatus-schurmanni-colombianus (Dinomyidae), an unidentified acaremyid, and cf. Microsteiromys sp. (Erethizontidae). Apatite Fission Track provides a detrital age (17.1 2.4 Ma) for the locality, slightly older than its inferred biochronological age (Colloncuran-early Laventan South American Land Mammal Ages: 15.6-13.0 Ma). Put together, both the mammalian assemblage and lithology of the fossil-bearing level point to a mixture of tropical rainforest environment and more open habitats under a monsoonal-like tropical climate. The fully fluvial origin of the concerned sedimentary sequence suggests that the Amazonian Madre de Dios Subandean Zone was not part of the Pebas mega-wetland System by middle Miocene times. This new assemblage seems to reveal a previously undocumented spatiotemporal transition between the late early Miocene assemblages from high latitudes (Patagonia and Southern Chile) and the late middle Miocene faunas of low latitudes (Colombia, Per, Venezuela, and ?Brazil).

  20. Revised Miocene and Pliocene diatom biostratigraphy of Upper Newport Bay, Newport Beach, California

    USGS Publications Warehouse

    Barron, J.A.

    1976-01-01

    North Pacific diatom zones XXIII through IX of Schrader are recognizable in the middle Miocene to lower Pliocene stratigraphic section exposed around Upper Newport Bay in Newport Beach, California. Correlation with DSDP Site 173 and other stratigraphic sections in California allows the selection of diatom datums that are the most reliable for long-distance correlation. Individual diatom datums are proposed as markers for North Pacific diatom zones XXIII through IX. Correlations with DSDP Site 173 reveal a hiatus in the lower part of Core 15 that corresponds with a distinct lithologic and floral change in the core. Preliminary silicoflagellate data for the Upper Newport Bay stratigraphic section supports the diatom correlations. Correlation with calcareous nannofossil, radiolarian, and silicoflagellate zones at Upper Newport Bay and at DSDP Site 173 suggests that the boundary between North Pacific diatom zones XVII and XVI approximates the middle Miocene/upper Miocene boundary. The Miocene/Pliocene boundary is estimated to be in North Pacific diatom zone X. One new stratigraphically useful diatom species is described, Lithodesmium reynoldsii. ?? 1976.

  1. Inferences for the Miocene to present evolution of the Anatolia Plateau south margin

    NASA Astrophysics Data System (ADS)

    Fernndez-Blanco, David; Bertotti, Giovanni

    2010-05-01

    The Miocene to recent Central Anatolia Plateau (CAP) is a first-order morphotectonic feature with high average elevations, low-relief dry interior and steep humid flacks. The ESF-sponsored Vertical Anatolia Movement Project (VAMP) aims at increasing the temporal and spatial resolution of plateau-building processes, using the CAP as a case study. Unravelling the tectonic history of its margins is essential. Our component of the VAMP strives to determine the subsidence-uplift mechanisms in the south margin of the Anatolia Plateau, structures responsible for, and age of growth of this margin, as well as achieve a quantitative understanding of the regional tectonics. A common division of the study area, from north to south, is: (i) south part of the continental basins of Central Turkey, with Tuz Gl Basin as the main representative, in the high flat area of the Anatolian Plateau, (ii) the arcuate Tauride fold-thrust belt and the Miocene Basins on top of it, forming part of the south flank of the plateau, (iii) offshore Cilicia Basin between Turkey and Cyprus, as the downward continuation of the south flank of the plateau, and (iv) the southward-thrusted Kyrenia Mountain Range and Circum-Troodos sedimentary succession. Miocene marine sediments in southern Turkey are presently found in Manavgat, Mut and Adana Basins. These sediments, possibly originally belonging to one single basin, are fundamental archives to constrain the tectonic stages immediately preceding and contemporaneous with plateau development. Miocene Mut Basin lies between Manavgat and Adana Basins, and is considered to have developed on a relatively stable area of Mesozoic Tauride basement, thus is a strategic area to solve the tectonic history that existed in southern Turkey since Miocene. Three N-S regional geological sections from Mut Basin to Mesoaria Basin (north Cyprus) that reproduce the present relationships among the units of the area have been constructed. These sections show a pre-Cenozoic highly-deformed metamorphic basement with paleotopography, unconformably overlain by relatively undeformed marine Miocene sediments, and post-Miocene continental deposits. These Miocene deposits are uplifted at more than 2000m in Mut Basin and located at depths of more than 2500m in the Cilicia Basin, outcroping again in the Kyrenia ridge. Two main periods of differential tectonic activity are distinguished within the post-Eocene succession; Miocene, with subsidence of the whole area, and post-Messinian, characterized by uplift in the north, subsidence in the central transtensional domains and thrust activity and uplift in the Kyrenia Range. In this contribution, using data from previous studies, a 3D visualization program and structural fieldwork techniques, we aim to determine the areal distribution and tectonic evolution of a Miocene basin that probably covered an area from Karaman to Mesoaria basins and from Antalya to Adana basins.

  2. The Oligocene-Miocene transition at the East Antarctic Wilkes Land margin: IODP Site 1356

    NASA Astrophysics Data System (ADS)

    Salabarnada, Ariadna; Escutia, Carlota; Nelson, Hans; Damuth, John E.; Jimenez-Espejo, Francisco

    2015-04-01

    IODP drilling in the flank of a levee deposit at continental rise Site U1356 recovered a thick section of Oligocene to upper Miocene sediments indicative of relatively deep water, sea ice -- influenced setting. Three main lithological units characterize the sediment record: 1) hemipelagic and bottom current deposition dominated during the late early to late Oligocene; 2) debris flows with interbedded turbidite deposits characterize sedimentation during late Oligocene to early Miocene; and 3) turbidite and hemipelagic sedimentation dominated during the early Miocene. The regional grid of multichannel seismic lines, provide a regional depositional context for the three units. Early to late Oligocene deposits record abyssal plain sedimentation under the influence of bottom currents. The sharp transition from abyssal plain facies to distal debris flows during the late Oligocene coincides with the deposition of large mass transport deposits at the base of the continental slope and erosion of large channels on the continental rise. The distal end of these mass transport deposits is recovered in our cores interbedded with levee turbidites from the nearby channel. The Oligocene to Miocene transition marks the disappearance of debris flows in our cores and the start of turbidite and hemipelagic deposition that characterizes levee sedimentation of the early Miocene environment. The studied section records one of the major climate transitions in the history of Earth's climate and ice sheet evolution during leading to the Mi-1 event. We argue that mass transport processes resulted from East Antarctic Ice Sheet expansion during the climate cooling leading to the Mi-1 glaciation. Following the Mi-1 event, sedimentation is characterized by hemipelagic, turbidity-, and bottom-current deposition. In addition, we present elemental and clay mineralogy data that provide insights into terrigenous fluxes, productivity, and the transition from a poorly oxygenated low-silica system to a ventilated silica-enriched system that is more similar to the modern Southern Ocean.

  3. Orbital and suborbital-scale sedimentary rhythms in the Middle Miocene Onnagawa Formation, Northeastern Japan

    NASA Astrophysics Data System (ADS)

    Kurokawa, S.; Tada, R.; Takahashi, S.; Itaki, T.; Kubota, Y.

    2014-12-01

    Late Quaternary climate is characterized by millennial-scale abrupt climatic changes namely Dansgaard-Oeschger Cycles. Such millennial-scale changes are faithfully recorded in the Japan Sea sediments as alternation of dark and light colored silty clay, and the relationship between the millennial-scale variability and orbitally-driven changes in ice volume has been explored. On the other hand, presence of similar millennial-scale changes was reported from the Middle Miocene alternations of dark and light colored siliceous rocks in the Onnnagawa Formation, Northeastern Japan. Because large, unstable ice sheet was present during the Late Quaternary and the Middle Miocene, it is suggested that such millennial-scale variability and waxing and waning of unstable ice sheet could be interrelated. Thus, it is important to specify the cyclicity and the amplitude variability of millennial-scale cycles during the Middle Miocene to understand the underlying mechanism and the ultimate cause. The Middle Miocene Onnagawa Formation is known as bedded siliceous rocks equivalent to the Monterey Formation, California. Tada (1991) demonstrated that its cm-scale dark-light colored alternations reflected millennial-scale variability. However, the timing, periodicity, and duration of the millennial-scale variability are not fully understood. Thus, we aim to clarify when the millennial-scale variability became distinct and faded out, and examine its possible association with ice volume changes. We conducted a field survey in the Yashima area, Akita, Northeastern Japan to reconstruct a continuous sedimentary record throughout the Middle Miocene, and constructed the age model based on biostratigraphy. In addition, we identified cyclic changes in lithology, and applied cyclostratigraphy to produce the high-resolution age model. Based on this age model, we attempt correlation with δ18O curve to examine the relationship between cyclicity of δ18O changes and occurrence of millennial-scale variability.

  4. Paleogeographic and structural setting of Miocene strata in central western Nevada

    SciTech Connect

    Stewart, J.H. )

    1993-04-01

    Late Cenozoic sedimentary rocks as old as 19 Ma are widely distributed in central western Nevada. They are greatly more abundant than older Cenozoic strata and are commonly interpreted to have formed in fault-bounded basins that mark the onset of widespread extension in the Basin and Range Province. Miocene strata are largely coeval with a magmatic arc that extended south southeast near the boundary of the Basin and Range and Sierra Nevada Provinces. This arc produced voluminous andesitic flows and lahars that locally interfinger with the Miocene strata. Miocene depositional basins apparently varied greatly in size. The largest that can be defined clearly is the Esmeralda Basin that was at least 65 km long and 45 km wide. Other basins may have been larger but are difficult to reconstruct; still other basins may be small and isolated, particularly within the magmatic arc. Lacustrine deposits and minor interfingering deltaic and distal fluvial units predominate; near-source, coarse alluvial-fan and megabreccia landslide deposits are locally conspicuous. coarse near-source deposits, particularly landslide deposits, are interpreted to be adjacent to basin-bounding normal faults. The Esmeralda, Coal Valley, and Gabbs Valley-Stewart Valley-Tonopah Basins are interpreted to be related to large-scale Miocene extension. Other basins may be (1) pull-apart structures related to strike-slip faults, (2) downdropped blocks in areas of cross-cutting normal and/or strike-slip faults related to changes in the extension direction or (3) grabens or half-grabens related to uniform extension. Younger Cenozoic basins, including present-day basins, overprint and cut across the Miocene basins.

  5. A zircon study on Miocene silicic pyroclasts in the Bukkalja, Hungary

    NASA Astrophysics Data System (ADS)

    Szabo, Zs.; Harangi, Sz.

    2003-04-01

    During the Miocene, reapeted explosive eruptions of silicic magmas occurred in the Pannonian Basin,simultaneously with the main period of basin formation. The majority of the volcanic products are covered by post-Miocene sediments, the best study area in Hungary is the Bukkalja. Traditionally, the Miocene silicic piroklastic rocks of the Pannonian Basin have been devided into three horizonts (Lower-Middle-Upper Riolithe Complex) based on primary stratigraphic observations. Other studies point out that there are three horisonts based on the paleomagnetic data but several volcanic events based on radiometric ages (Marton &Pecskay, 1998.) Morphology of zircon mineral depends upon the temperatur and type of the magma (calc-alcaline, alcaline or peralcaline) it is crystallised from. This lead Pupin (1980) to introduce a methode to distinguish different granitic magmas, based on the morphology of their zicon population. We applied this method for silicic volcanic rocks in the Bukkalja area with an attempt to see similarities and/or differences among the previously distinguish Miocene pyroclastic horisonts. We applied our resultes taking into account recent resultes of Vavra and Klotzli. We focused on the bimodal samples wich has been already studied by cathodluminescence image. As a results of our study we can conclude the followings about Miocen silicic piroclasts in the Bkkalja: 1., The source of magma is the mantel with different magnitude crustal contamination. 2., Generally the samples from the "same horison" have different chemical characteristics, so we cannot say: there are three well defined complexes. 3., In some cases zircon morphology seems to be a good method to follow piroclast levels. 4., There are some samples with bimodal zircon population, wich means that the magma it is crystallised from has a higher alcaline component. 5., Using the Pupin method we can see examples for the solution of local stratigraphic problems. The preliminary results of zircon morphological study are supported by geochemical data.

  6. Plate tectonic model for the oligo-miocene evolution of the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Cohen, Curtis R.

    1980-10-01

    This paper outlines a plate tectonic model for the Oligo-Miocene evolution of the western Mediterranean which incorporates recent data from several tectonic domains (Corsica, Sardinia, the Kabylies, Balearic promontory, Iberia, Algero-Provenal Basin and Tunisian Atlas). Following late Mesozoic anticlockwise rotation of the Iberian peninsula (including the Balearic promontory and Sardinia), late Eocene collision occurred between the Kabylies and Balearic promontory forming a NE-trending suture with NW-tectonic polarity. As a result of continued convergence between the African and European plates, a polarity flip occurred and a southward-facing trench formed south of the KabylieBalearic promontory suture. During late Oligocene time an E-W-trending arc and marginal basin developed behind the southward-facing trench in the area of the present-day Gulf of Lion. Opening of this basin moved the CorsicaSardiniaCalabriaPetit KabylieMenorca plate southward, relative to the African plate. Early Miocene back-arc spreading in the area between the Balearic promontory and Grand Kabylie emplaced the latter in northern Algeria and formed the South Balearic Basin. Coeval with early Miocene back-arc basin development, the N-S-extension in the Gulf of Lion marginal basin changed to a more NW-SE direction causing short-lived extension in the area of the present-day Valencia trough and a 30 anticlockwise rotation of the Corsica-Sardinia-CalabriaPetit Kabylie plate away from the European plate. Earlymiddle Miocene deformation along the western Italian and northeastern African continental margins resulted from this rotation. During the early late Miocene (Tortonian), spreading within a sphenochasm to the southwest of Sardinia resulted in the emplacement of Petit Kabylie in northeastern Algeria.

  7. The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru.

    PubMed

    Lambert, Olivier; Bianucci, Giovanni; Post, Klaas; de Muizon, Christian; Salas-Gismondi, Rodolfo; Urbina, Mario; Reumer, Jelle

    2010-07-01

    The modern giant sperm whale Physeter macrocephalus, one of the largest known predators, preys upon cephalopods at great depths. Lacking a functional upper dentition, it relies on suction for catching its prey; in contrast, several smaller Miocene sperm whales (Physeteroidea) have been interpreted as raptorial (versus suction) feeders, analogous to the modern killer whale Orcinus orca. Whereas very large physeteroid teeth have been discovered in various Miocene localities, associated diagnostic cranial remains have not been found so far. Here we report the discovery of a new giant sperm whale from the Middle Miocene of Peru (approximately 12-13 million years ago), Leviathan melvillei, described on the basis of a skull with teeth and mandible. With a 3-m-long head, very large upper and lower teeth (maximum diameter and length of 12 cm and greater than 36 cm, respectively), robust jaws and a temporal fossa considerably larger than in Physeter, this stem physeteroid represents one of the largest raptorial predators and, to our knowledge, the biggest tetrapod bite ever found. The appearance of gigantic raptorial sperm whales in the fossil record coincides with a phase of diversification and size-range increase of the baleen-bearing mysticetes in the Miocene. We propose that Leviathan fed mostly on high-energy content medium-size baleen whales. As a top predator, together with the contemporaneous giant shark Carcharocles megalodon, it probably had a profound impact on the structuring of Miocene marine communities. The development of a vast supracranial basin in Leviathan, extending on the rostrum as in Physeter, might indicate the presence of an enlarged spermaceti organ in the former that is not associated with deep diving or obligatory suction feeding. PMID:20596020

  8. Seawater osmium isotope evidence for a middle Miocene flood basalt event in ferromanganese crust records

    NASA Astrophysics Data System (ADS)

    Klemm, Veronika; Frank, Martin; Levasseur, Sylvain; Halliday, Alex N.; Hein, James R.

    2008-08-01

    Three ferromanganese crusts from the northeast, northwest and central Atlantic were re-dated using osmium (Os) isotope stratigraphy and yield ages from middle Miocene to the present. The three Os isotope records do not show evidence for growth hiatuses. The reconstructed Os isotope-based growth rates for the sections older than 10 Ma are higher than those determined previously by the combined beryllium isotope (10Be/9Be) and cobalt (Co) constant-flux methods, which results in a decrease in the maximum age of each crust. This re-dating does not lead to significant changes to the interpretation of previously determined radiogenic isotope neodymium, lead (Nd, Pb) time series because the variability of these isotopes was very small in the records of the three crusts prior to 10 Ma. The Os isotope record of the central Atlantic crust shows a pronounced minimum during the middle Miocene between 15 and 12 Ma, similar to a minimum previously observed in two ferromanganese crusts from the central Pacific. For the other two Atlantic crusts, the Os isotope records and their calibration to the global seawater curve for the middle Miocene are either more uncertain or too short and thus do not allow for a reliable identification of an isotopic minimum. Similar to pronounced minima reported previously for the Cretaceous/Tertiary and Eocene/Oligocene boundaries, possible interpretations for the newly identified middle Miocene Os isotope minimum include changes in weathering intensity and/or a meteorite impact coinciding with the formation of the Nrdlinger Ries Crater. It is suggested that the eruption and weathering of the Columbia River flood basalts provided a significant amount of the unradiogenic Os required to produce the middle Miocene minimum.

  9. Seawater osmium isotope evidence for a middle Miocene flood basalt event in ferromanganese crust records

    USGS Publications Warehouse

    Klemm, V.; Frank, M.; Levasseur, S.; Halliday, A.N.; Hein, J.R.

    2008-01-01

    Three ferromanganese crusts from the northeast, northwest and central Atlantic were re-dated using osmium (Os) isotope stratigraphy and yield ages from middle Miocene to the present. The three Os isotope records do not show evidence for growth hiatuses. The reconstructed Os isotope-based growth rates for the sections older than 10??Ma are higher than those determined previously by the combined beryllium isotope (10Be/9Be) and cobalt (Co) constant-flux methods, which results in a decrease in the maximum age of each crust. This re-dating does not lead to significant changes to the interpretation of previously determined radiogenic isotope neodymium, lead (Nd, Pb) time series because the variability of these isotopes was very small in the records of the three crusts prior to 10??Ma. The Os isotope record of the central Atlantic crust shows a pronounced minimum during the middle Miocene between 15 and 12??Ma, similar to a minimum previously observed in two ferromanganese crusts from the central Pacific. For the other two Atlantic crusts, the Os isotope records and their calibration to the global seawater curve for the middle Miocene are either more uncertain or too short and thus do not allow for a reliable identification of an isotopic minimum. Similar to pronounced minima reported previously for the Cretaceous/Tertiary and Eocene/Oligocene boundaries, possible interpretations for the newly identified middle Miocene Os isotope minimum include changes in weathering intensity and/or a meteorite impact coinciding with the formation of the No??rdlinger Ries Crater. It is suggested that the eruption and weathering of the Columbia River flood basalts provided a significant amount of the unradiogenic Os required to produce the middle Miocene minimum. ?? 2008 Elsevier B.V.

  10. Evidence for Repeated Early Miocene Glaciation and the Cutting of Upper Taylor Valley from the Friis Hills, Antarctica

    NASA Astrophysics Data System (ADS)

    Lewis, A.; Ashworth, A. C.; Marchant, D. R.; Hemming, S. R.

    2009-12-01

    The Friis Hills, located at the head of Taylor Valley in the the McMurdo Dry Valleys, hold a sequence of stacked tills at least Early Miocene in age. Sedimentology, clast lithology and bedrock striations indicate these tills were deposited from wet-based glaciers that flowed southeastward down a shallow paleovalley toward the Ferrar trough. Interbedded paleosols, fluvial, and glaciolacustrine deposits register ice-free periods when the valley held small streams and ponds. Exceptionally well-preserved fossil biota suggests mild conditions during at least two of these interglacial episodes. Proglacial lacustrine deposits that include dropstones and debris flows mark the return of glacial conditions but fossil leaves and wood of Nothofagus suggest conditions during the initial phase of ice advance were also relatively mild. Geomorphic relationships show that major valley incision must have taken place after deposition of these sediments as the Friis Hills is today a flat-topped inselberg, about 5 km across, isolated from nearby topography by the deep glacial troughs of the Taylor Valley drainage. A second suite of tills, directly overlying the first, registers a reorganized glacial system with ice streaming eastward, roughly parallel to Taylor Valley. Like the first, these tills were deposited during repeated ice advances but glaciers never fully inundated the Friis Hills and ice-free periods are marked by only weak weathering surfaces and thin glaciolacustrine deposits. We interpret the changing glacial pattern to reflect headward cutting in upper Taylor Valley and the capture of ice from the Ferrar drainage. A volcanic ash interbed dated by Ar-Ar at 19.76 (0.11) Ma occurs in a Taylor Valley-oriented drift near the eastern edge of the Friis Hills plateau. Based on its stratigraphic position, the older suite of tills and fossil-bearing interbeds are >19.76 Ma. Underlying bedrock striations show that ice flow had been redirected into Taylor Valley by this time. The preservation of the ash adjacent to Taylor Glacier suggests that cutting had already deepened the Taylor trough enough to protect the deposit from erosion during later glacier advances. The Friis Hills deposits are the first to show terrestrial evidence for Early Miocene-aged (or older) glacier cycles and the biota will provide novel constraints on paleoclimate. These tills may also help shed light on how Sirius Group deposits relate to the well-dated Middle Miocene-aged glacial record from the western Dry Valleys. Sirius Group tills occur on Table Mountain only 20 km to the south of the Friis Hills and at the same elevation. The lithology of these sediments is similar to that of the older tills in the Friis Hills and like them these sediments show ice flow into the Ferrar trough. One major difference is the degree of lithification. Tills in the Friis Hills are only weakly consolidated, whereas Sirius Group deposits are strongly lithified. This suggests that the Sirius Group in the southwestern Dry Valleys may be older than 19.76 Ma and could date to a period not long before deposition began on the Friis Hills. This research is supported by NSF OPP 0739693.

  11. Correlation and zonation of miocene strata along the atlantic margin of North America using diatoms and silicoflagellates

    USGS Publications Warehouse

    Abbott, W.H.

    1978-01-01

    Six Atlantic Miocene siliceous microfossil zones are proposed based on onshore and offshore samples from the United States Atlantic Margin. Diatoms and silicoflagellates are used to establish the zones. These zones are from oldest to youngest: 1. Zone I Actinoptychus heliopelta Concurrent Range Zone - Early Miocene 2. Zone II Delphineis ovata Partial Range Zone - late Early to early Middle Miocene 3. Zone III Delphineis ovata/Delphineis penelliptica Concurrent Range Zone - early Middle Miocene 4. Zone IV Delphineis penelliptica Partial Range Zone - Middle Miocene 5. Zone V Delphineis penelliptica/Coscinodiscus plicatus Concurrent Range Zone - Middle Miocene 6. Zone VI Coscinodiscus plicatus Partial Range Zone - Middle Miocene. The six zones are easily traced along the Southern and Middle Atlantic Seaboard, but the older three are found for the most part between Cape Hatteras and New Jersey. There is some suggestion of sea-level change during Zone IV. Using rare planktonic diatoms that are index species from other regions and the zonal markers established in this study, correlation can be made with the Standard Foraminiferal Zones, the North Pacific Diatom Zones and with DSDP core 391A in the Blake-Bahama Basin. ?? 1978.

  12. Interim report on the ground-water resources of Manatee County, Florida

    USGS Publications Warehouse

    Peek, Harry M.; Anders, Robert B.

    1955-01-01

    Manatee County comprises an area of about 800 square miles adjacent to the Gulf of Mexico in the southwestern part of the Florida peninsula. The county is underlain at depths ranging from about 200 to 350 feet by a series of limestone formations of Tertiary age having a total thickness of several thousand feet. The upper part of the limestone section consists of the Ocala group of Eocene age, the Suwannee limestone of Oligocene age, and the Tampa formation of early Miocene age. These limestone formations are overlain by the Hawthorn formation of middle Miocene age which consists of interbedded clay, limestone, and sand. The Hawthorn is overlain by undifferentiated deposits of sand, limestone, and shell of Pliocene(?) and Pleistocene age that range in thickness from a few feet to about 75 feet.

  13. Cementation in Oligo-Miocene non-tropical shelf limestones, Otway Basin, Australia

    NASA Astrophysics Data System (ADS)

    Nicolaides, Stelios

    1995-02-01

    The Oligocene to Miocene Heytesbury Group of the Otway Basin, southeastern Australia, is a non-tropical carbonate shelf succession. This subsurface stratigraphic succession consists of bioclastic grainstones to mudstones containing bryozoa, benthonic and planktonic foraminifera, echinoderms, brachiopods, and molluscs. The basal bryozoa-dominated Clifton Formation was deposited in relatively shallow waters. The overlying Gellibrand Marl, rich in planktonic foraminifera and bryozoa, formed under deep waters. The uppermost unit, benthonic foraminifera-dominated Port Campbell Limestone, was deposited in a moderately deep, middle shelf environment. Cementation is limited and includes: (1) scalenohedral calcite (non-luminescent to bright, Mn- and Fe-poor, in inter- and intraparticle porosity); (2) blocky equant calcite (dull, Mn- and Fe-rich, in interparticle porosity); (3) syntaxial calcite overgrowths on echinoderm particles (non/bright/dull-zoned); (4) euhedral dolomite (in the interparticle pore space of the Port Campbell Limestone); (5) bladed-prismatic calcite (ferroan, in planktonic foraminifera); (6) fibrous calcite (non-luminescent, in intraparticle porosity); and (7) glauconite and iron-oxides (only in intraparticle porosity). All CaCO 3 cements are low-Mg calcites (< 4 mol% MgCO 3). The cements observed in the Heytesbury Group appear to have formed in three successive diagenetic environments: (1) early shallow burial (early Fe- and Mn-poor, non-luminescent syntaxial overgrowths and non-luminescent scalenohedral calcite, under oxidising conditions); (2) late shallow burial (bright, more Mn-rich syntaxial overgrowth zone, i.e., more than the initial non-luminescent one, and bright scalenohedral calcite, under moderately reducing pore water conditions); and (3) moderate burial (ferroan, dull blocky calcite and dull syntaxial overgrowth zone, under reducing conditions). Pressure solution was the main cement-producing mechanism, although seawater and aragonite dissolution could account for the precipitation of the early non-luminescent cements. Scarcity of early interparticle cements may have been caused by the calcite-rich character of the original sediments. The ferroan dully luminescent blocky equant calcite and syntaxial overgrowths, typically interpreted to represent products of deep burial in ancient carbonate successions, are observed in the shallow-buried Port Campbell Limestone.

  14. Style and age of late Oligocene-early Miocene deformation in the southern Stillwater Range, west central Nevada: Paleomagnetism, geochronology, and field relations

    USGS Publications Warehouse

    Hudson, Mark R.; John, David A.; Conrad, James E.; McKee, Edwin H.

    2000-01-01

    Paleomagnetic and geochronologic data combined with geologic mapping tightly restrict the timing and character of a late Oligocene to early Miocene episode of large magnitude extension in the southern Stillwater Range and adjacent regions of west central Nevada. The southern Stillwater Range was the site of an Oligocene to early Miocene volcanic center comprising (1) 28.3 to 24.3 Ma intracaldera ash flow tuffs, lava flows, and subjacent plutons associated with three calderas, (2) 24.8 to 20.7 Ma postcaldera silicic dikes and domes, and (3) unconformably overlying 15.3 to 13.0 Ma dacite to basalt lava flows, plugs, and dikes. The caldera-related tuffs, lava flows, and plutons were tilted 60°-70° either west or east during the initial period of Cenozoic deformation that accommodated over 100% extension. Directions of remanent magnetization obtained from these extrusive and intrusive, caldera-related rocks are strongly deflected from an expected Miocene direction in senses appropriate for their tilt. A mean direction for these rocks after tilt correction, however, suggests that they were also affected by a moderate (33.4° ± 11.8°) component of counterclockwise vertical axis rotation. Paleomagnetic data indicate that the episode of large tilting occurred during emplacement of 24.8 to 20.7 Ma postcaldera dikes and domes. In detail, an apparent decrease in rotation with decreasing age of individual, isotopically dated bodies of the postcaldera group indicates that most tilting occurred between 24.4 and 24.2 Ma. The onset of tilting immediately following after the final caldera eruptions suggests that the magmatism and deformation were linked. Deformation was not driven by magma buoyancy, however, because tilting equally affected the caldera systems of different ages, including their plutonic roots. It is more likely that regional extension was focused in the southern Stillwater Range due to magmatic warming and reduction of tensile strength of the brittle crust. Faults that accommodated deformation in the southern Stillwater Range initially dipped steeply and cut deeply to expose more than 9 km of crustal section. The exposed crustal sections are probably rotated blocks above an unexposed basal detachment that lay near the early Miocene brittle-ductile transition.

  15. Oligo-Miocene onset of exhumation of the Tien Shan: the role of the Talas-Fergana strike-slip fault

    NASA Astrophysics Data System (ADS)

    Bande, A.; Sobel, E. R.; Mikolaichuk, A.; Auxietre, J.; Munsch, H.

    2012-12-01

    The Talas-Fergana dextral strike-slip fault (TFF) in Central Asia is one of the world's most prominent strike-slip faults. Separating the Western and Central Tien Shan, the TFF forms a prominent feature in the mountainous topography. Geological knowledge about the Western Tien Shan is substantially less developed than the surrounding areas and it is an area where the Pamir indentation should play an important role in its geodynamic evolution. In this contribution we present new thermochronological data from the Kyrgyz Western Tien Shan and relate them to the evolution of the mountain belt. Apatite fission track samples from the northern Western Tien Shan (Talas and Shandalash ranges) show clustered reset Oligo-Miocene (22-29 Ma) ages. This first group of samples was collected less than 15 km away from TFF and shows the maximum amount of Cenozoic exhumation. In contrast, a vertical profile located in the Shandalash range but ~60 km away from the TFF exhibit partially reset, Eocene (30-43 Ma) ages, implying a smaller amount of exhumation along strike moving further away from the main strike-slip fault. The northernmost samples (Ugam range) also showed partially reset ages (37-51 Ma), showing that exhumation also decrease moving towards the Kazakh platform. In addition, the Oligo-Miocene episode is also recorded in the stratigraphic section of the adjacent Fergana basin by a change in the source area, detected using detrital zircon age populations. Several studies in the northern Central Tien Shan show a regional increase in the exhumation rate by the late Miocene (~10 Ma). Although our data come from similar latitudes within the Tien Shan we have little evidence to extrapolate this event to the Western Tien Shan. However, our results can be compared with the onset of exhumation of the southernmost basement involved thrusts in the Chinese South Tien Shan. Studies north of the Kashgar area determined the initiation of exhumation there to be around 25 Ma. Paleomagnetic studies along the TFF show opposite sense of rotation on either side of the strike-slip fault in the Cenozoic, but the timing of that motion is not well constrained. Both the Northern Tien Shan west of the TFF and the Southern Tien Shan east of the TFF show onset of exhumation at around the Oligo-Miocene boundary, despite being separated from each other by ~400 km. We explain this behavior by interpreting both set of ranges as horse-tails, kinematically-linked to the main strike-slip fault. Furthermore, we can conclude that the onset of Cenozoic slip along the TFF was at around the same time frame.

  16. Tectonics or climate: What drove the Miocene global expansion of C4 grasslands?

    NASA Astrophysics Data System (ADS)

    Singh, Seema; Awasthi, A. K.; Parkash, B.; Kumar, S.

    2013-04-01

    Investigations into the most plausible causes which triggered the Late Miocene global expansion of C4 grasslands have reached no consensus and are still being debated. The global decline in CO2 levels in the Late Miocene has been thought to be the most common driver. Although C4 grassland expansion was largely confined to the Late Miocene, their first appearance varied significantly in different parts of the Old and New world and therefore emphasizes role of local and/or regional factors may or may not be in combination with one or more global factors. The dynamic Himalayan orogen constitutes a significant global tectonic event that is believed to have affected global climate. Hence, a study of the Himalayan foreland basin sediments could help in gleaning out possible causes behind this major paleoecologic event, which could perhaps be directly or indirectly related. Stable carbon isotope analyses of a total of 141 pedogenic carbonates in the Mio-Pleistocene Siwalik paleosols of the Ramnagar sub-basin are coherent, providing a better insight into paleovegetational changes across the sub-basin on temporal and spatial scales. Furthermore, paleovegetational history during Oligocene is reconstructed from Dagshai paleosols exposed in the Subathu sub-basin. The isotopic results show dominance of C3 vegetation pre-7 Ma and dominance of C4 vegetation post-5 Ma. Percentage abundance of C4 vegetation was less than 20 % pre-7 Ma but increased to more than 40 % post-5 Ma, reaching up to 100 % in the youngest analyzed sediments. There is exclusive dominance of C3 vegetation during Oligocene. These results conform to the pattern of change in vegetation documented in other parts of the Himalayan belt. The global expansion of C4 grasslands largely during Late Miocene have long been linked with then climate changes, particularly brought by declining atmospheric CO2 level, large-scale fires, intensification of monsoon, seasonality, and aridity as demonstrated by various researchers. These major hypotheses explaining expansion of C4 grasslands during Late Miocene are not very convincing due to significant shortcomings associated with them, for example, expansion of C4 grasslands in non-monsoonal regions put serious constraints on the monsoonal intensification hypothesis. Likewise, aridity as being the primary driver of C4 grassland expansion seems hard to support since there is no substantial evidence that could suggest global onset of arid conditions at about same geologic time, and some most arid periods, like the Triassic, show no evidence of C4 plants. We suggest that the initial lowering of CO2 below 450 ppmV created an environment for the beginning of C4 vegetation, but the persistence of this threshold value for a considerable time during Late Miocene appears to be the probable cause of the Late Miocene global expansion of C4 grasslands irrespective of their time of first appearance. It has been deduced through the correlation of Himalayan tectonic events with atmospheric CO2 levels and paleovegetational changes since Upper Miocene times that it was indeed the Late Miocene continuous, intense tectonic instability of the Himalayas that significantly decreased atmospheric CO2 levels and which perhaps played a key role in changing the nature of photosynthetic pathways.

  17. Evolution of the Northern Nicaragua Rise during the Oligocene Miocene: Drowning by environmental factors

    NASA Astrophysics Data System (ADS)

    Mutti, Maria; Droxler, Andr W.; Cunningham, Andrew D.

    2005-04-01

    Possible causes to explain platform drowning have been hotly debated by carbonate sedimentologists for more than a decade now. In this paper, we present multiple evidence to explain the drowning of a carbonate megabank that covered most of the modern Northern Nicaragua Rise (NNR) during an interval spanning from late Oligocene to early Miocene by the interaction of several environmental factors. The recovery during ODP Leg 165 of late Oligocene to middle Miocene sedimentary sequences in the sub-seafloor of the modern channels and basin, Pedro Channel and Walton Basin, respectively, that dissect the NNR (Site 1000) and south of the rise in the Colombian Basin (Site 999), combined with information from dredged rock samples, allows us to explore in more detail the timing and possible mechanisms responsible for the drowning of the megabank and its relationship to Miocene climate change. The modern system of isolated banks and shelves dissected by a series of intervening seaways and basins on the NNR has evolved from a continuous, shallow-water carbonate megabank that extended from the Honduras/Nicaraguan mainland to the modern island of Jamaica. Available information suggests that this megabank broke apart and partially drowned in the late part of the late Oligocene at around 27 Ma and finally foundered during the late early Miocene around 20 Ma, resulting in limited neritic coral growth in the areas where the modern isolated carbonate banks and shelves are occurring today. Available information also suggests that the southern and central parts of Pedro Channel were already a deep-water area before the major episode of platform drowning, and its formation predates the initiation of the Caribbean Current. However, after the partial drowning of the megabank, the channel has become a major pathway for the Caribbean Current. Stratigraphic units identified in deep-water carbonates sampled at ODP Sites 999 and 1000 help to constrain the environmental setting leading to the drowning of the banks. Changes in lithology and mass accumulation rates of both the carbonate and non-carbonate fraction parallel stable isotope shifts and likely indicate regional changes in climate and circulation during the late Oligocene middle Miocene interval. Carbonate mass accumulation rates (MARs) at Site 999 suggest increased regional productivity during the early Miocene. Terrigenous MARs at both Sites 999 and 1000 show a general increase from the Burdigalian through the Serravallian. The temporal association among episodes of neritic platform deposition, followed by increased productivity as identified by higher carbonate MARs and positive excursion in carbon isotopes, suggests that oceanographic changes such as local upwelling and nutrification have led to the partial drowning of the NNR megabank.

  18. A High-Resolution Investigation of mid-Miocene Global Cooling

    NASA Astrophysics Data System (ADS)

    Maddison, E. J.; Coe, A. L.; Cohen, A. S.; Weedon, G. P.; Gilmour, M. A.

    2007-12-01

    The mid-Miocene encompasses one of the four major cooling steps that formed part of the long-term decrease in global temperature during the Cenozoic. Four distinct mechanisms have been suggested to explain this mid- Miocene (c. 14 Ma) climatic change: drawdown of CO¬2 by burial of large amounts of marine organic matter (the "Monterey Hypothesis"); drawdown of CO¬2 by an increase in chemical weathering of fresh silicate rocks resulting from uplift of the Himalaya; changing ocean circulation patterns redistributing ocean-atmosphere heat; and the congruence of orbital parameters. However, the duration, timing and causative mechanisms of mid-Miocene cooling remain poorly constrained, largely due to incomplete sedimentary successions spanning this time period. In an attempt to resolve these issues we have conducted a high-resolution study of the Monterey Formation near Santa Barbara. Our detailed graphic logging has enabled us to identify eleven mudrock facies that are distributed cyclically (length-scales ranging from c. 0.5 to 20 m) throughout the section. Biostratigraphic dating of this section is based on diatom (this study) and calcareous nannofossil (Föllmi et al., 2005, GSA Bulletin, 117: 589-619) datums. Utilising these biostratigraphic age constraints and Fourier analysis of geochemical and physical parameters, we have produced an astronomical timescale that we have correlated with the Laskar orbital solution (Laskar et al. 2004, Astronomy and Astrophysics, 428: 261-285). High-resolution scanning electron microscopy has shown that several benthic foraminifera species are well preserved in these sedimentary deposits. The exceptional preservation of this sedimentary succession allows us to use a suite of geochemical proxies to investigate this global cooling event. The mid-Miocene carbon isotope record is characterised by a positive excursion, which commenced during global warming and ended after major expansion of the Antarctic ice sheet. We present an astronomically tuned high-resolution record (sampling on a sub-millenial timescale) of total organic carbon abundance and carbon isotope data that provides a detailed record of changes in the carbon cycle in the mid-Miocene. This new high- resolution carbon isotope record can be correlated with the distinctive carbon isotope maxima events CM5 and CM6 that have been identified previously in deep-sea sections. Our high-resolution data from the Monterey Formation provides us with a robust framework within which we can examine the dynamics and mechanisms of mid-Miocene global cooling.

  19. The role of CO2 in modulating Miocene climate and ice volume (Invited)

    NASA Astrophysics Data System (ADS)

    Greenop, R.; Sosdian, S. M.; Lear, C. H.; Foster, G. L.; Wilson, P.

    2013-12-01

    The Neogene period is characterised by long term cooling interrupted by a number of prominent warming events, for example the Middle Miocene climate optimum (MCO), an interval of global warmth, that was followed by the Mid-Miocene climate transition (MMCT), a step cooling superimposed on the long-term climate trend. Several Antarctic climate records suggest that the East Antarctic ice sheet was dynamic during the early Miocene (Lewis et al., 2006, Passchier et al., 2011). However, the output from ice sheet modeling experiments suggest that once large ice sheets have grown on East Antarctica they are inherently stable and consequently relatively high levels of CO2 are needed in order to initiate a deglaciation (~1000 ppm; Pollard and DeConto 2005). Over the past 5 years or so an increasing number of studies have illustrated that atmospheric CO2 was much more variable during the Miocene than previously thought, although the magnitude of CO2 change remains much smaller than anticipated by the ice sheet models (Foster et al., 2012, Kurshner et al., 2008, Zhang et al., 2013). Here we will draw together δ11B-pCO2 records, both new published, to evaluate the role of CO2 in modulating Miocene climate. Calculated δ11B-CO2 spanning 5-23 Ma from ODP Sites 926 and 872 are in broad agreement with the other recently published alkenone CO2 records despite the limitations of δ11B based CO2 reconstruction over these long timescales (e.g. variable δ11B of seawater) (Sosdian et al. 2013). We will also present high-temporal resolution boron isotope records from ODP Site 761 across the MCO and ODP Site 926 across the Oligocene-Miocene boundary. We examine the role of CO2 in controlling the stability of the East Antarctic ice sheet during these short time intervals thought to be characterised by substantial retreat of the AIS (Feakins et al. 2012, Passchier et al. 2011, Warny et al. 2009). References: Feakins et al. (2012) Nat. Geoscience 5(8) 557-560, Foster et al., (2012) ESPL 341 243-254, Lewis et al., (2006) Geology 34(7) 513-516, Kurshner et al., (2008) PNAS 105(2) 449-453, Passchier et al., (2011) Geol Soc Am Bull, 123(11-12), 2352-2365, Pollard & DeConto (2005) Global and Planetary Change 45(1-3) 9-21, Sosdian et al. (2013) ICP11 abstract no. 161, Warny et al. (2009) Geology 37(10) 955-958, Zhang et al., (2013) in press, Phil. Trans. R. Soc. A

  20. Post-Miocene Tectonics from Black Sea to Mediterrenean Sea along Central Anatolian Plateau

    NASA Astrophysics Data System (ADS)

    Rojay, B.; zsay?n, E.; iner, A.

    2012-04-01

    The existences of the gross structures are crucial elements in the understanding of the Neogene evolution of the Anatolia. The structures, from north to south, are fairly documented extensional Black Sea coast structures, "N vergent tectonics" in Black Sea region, the cross cutting scar/shear zone -North Anatolian Fault- , S verging tectonics in central Anatolian overthrust belt (Cretaceous ophiolitic mlange belt), extensional Tuzgl basin, basins like Cilicia, Mut situated to the back of the Cyprian arc and Cyprus locked subduction and accretionary tectonics (locked by approaching and colliding of the Eratosthenes and Hecatacus "seamount" obstacles). The closure of the northern Neotethys during post-Late Eocene- pre-Miocene end with the collision of the squeezed "Anatolian Block" from south with the Eurasian Continent. Consequently the linkage of the central Anatolian basins is lost with the Seas (Paratethys) in north by the evolution of Black Sea Mountains. However, the subduction in southern Neotethys continued with a complex array due to oblique subduction between "Anatolian Block" and downgoing African-Arabian plates. The growth of the accretionary wedge along southeast Anatolia resulted in retreat of the Miocene Seas towards Basra Bay (Iraq) and collision of the southeast Anatolian belt operated to the end of late Miocene where the marine realm in eastern Mediterrenean Sea continues. The rifting - sea-floor spreading in Red Sea, propagating of Dead Sea Transform to the north and oblique subduction in southern Tethys Ocean during different times in Miocene-Pliocene manifested a various different tectonic mechanism stories in the evolution of the Neogene basin in Anatolia. Consequently progressive closure of the Tethys Oceans resulted in the development Central Anatolian and Eastern Anatolian Plateaus. The growth of the Plateaus, in other words, the progressive shortening from north to south during Late Miocene, ended with the escape of the Anatolian Block to the west during Pliocene as a result of the initiation of the North and East Anatolian Faults. The escape can be caused by the retreat of downgoing slab or enlargement of downgoing slab window or solely initiation of the North and East Anatolian faults as single shears or all. The escape was resulted in the NW-SE to NE-SW multi oriented extension in central Anatolian Plateau (from Ankara to Tuzgl lake to Mut region) between North Anatolian in north and Cyprus in south. To sum up, the regions between the seismogenic North Anatolian Fault in north and Kirenia of northern Cyprus in south experience an extension since Pliocene. Key words: uplift, plateau evolution, locked subduction, Miocene, Anatolia.

  1. Orbitally paced phosphogenesis in Mediterranean shallow marine carbonates during the middle Miocene Monterey event

    NASA Astrophysics Data System (ADS)

    Auer, Gerald; Hauzenberger, Christoph A.; Reuter, Markus; Piller, Werner E.

    2015-04-01

    During the Oligo-Miocene major phases of phosphogenesis occurred in the Earth's oceans. Particularly in the Mediterranean region phosphate-rich sediments are well-known during this time. However, most phosphate-rich beds represent condensed or allochthonous hemipelagic deposits, formed by a complex interplay of physical and chemical enrichment processes. These underlying processes limit the application of these records for the study of a possible Milankovitch-scale climate control on Miocene phosphogenesis. In this regard the middle Miocene "Monterey event" is of particular interest, as it represents a documented phase of phosphogenesis coupled with a prominent carbon isotope excursion containing nine orbitally paced carbon isotope maxima (CM-events). The Oligo-Miocene shallow marine Decontra section located on the Maiella Platform (central Apennines, Italy), is a widely continuous carbonate succession in a mostly outer to middle neritic setting. Of particular interest are the well-winnowed grain- to packstones of the Middle Miocene Bryozoan Limestone, were occurrences of authigenic phosphate grains coincide with the Monterey event. The depositional setting of the Bryozoan Limestone allows to resolve the influence of orbital forcing on phosphogenesis, within a bio-, chemo- and cyclostratigraphically constrained stratigraphic model. LA-ICP-MS analyses revealed a significant enrichment of Uranium in the studied authigenic phosphate grains compared to the surrounding carbonate sediment. Notably, the Uranium enrichment allowed the use of natural gamma radiation (GR) as a proxy for the qualitative estimation of autochthonous phosphate content within the section, based on the absence of any other major gamma ray sources within the sediment. Time series analyses of high-resolution GR data indicate a strong influence of the 405kyr long-eccentricity cycle on natural gamma radiation in the Bryozoan Limestone. Our results link maxima in the GR record and thus phosphate content to orbitally paced increases in the burial of organic carbon, particularly during the CM-events of the "Monterey event". Thus, phosphogenesis during the middle Miocene in the Mediterranean was consequently controlled by the 405-kyr-eccentricity and its influence on large-scale paleoproductivity patterns in the Mediterranean.

  2. Miocene to Recent geological evolution of the Lazufre segment in the Andean volcanic arc

    NASA Astrophysics Data System (ADS)

    Naranjo, J. A.; Villa, V.; Ramrez, C.; Prez de Arce, C.

    2014-12-01

    The volcano-tectonic setting in which the InSAR-detected Lazufre deformation is developing is particularly relevant in the evolution of this Andean volcanic arc segment (25-26S). Through regional mapping techniques, a comprehensive field control in addition to geochronological sampling, various volcanic units comprising stratovolcanoes, volcanic complexes, ignimbrites and caldera structures are distinguished. The Lazufre intumescence is located above the overlying block of the NE trending Middle Miocene, Pedernales-Arizaro overthrust. This area comprises an Upper Miocene (8-4 Ma) basal unit of andesitic-dacitic volcanoes and lava fields, upon which nine volcanic complexes of similar composition, including Caletones de Cori Ignimbrite and Escorial Volcano, Lastarria, Cordn del Azufre and Bayo volcanic complexes, were emplaced in several pulses between 3.5 Ma and Holocene times. Coalescing Lazufre structure, immediately to the SE, we have discovered the Miocene (9.8 Ma) Los Colorados caldera. This caldera is 30 km in diameter and sourced the homonymous dacitic ignimbrite of about 500 km3. The caldera scarp was formed in Paleozoic rocks, Miocene dacitic-rhyolitic ignimbrites and ~16 and 10 Ma volcanoes. A 6.9-6.8 Ma andesitic-dacitic volcano ridge formed by Abra Grande, Ro Grande and Aguas Calientes stratovolcanoes, from NE to SW, is nested on the caldera floor. Lavas of early stages of Cordn del Azufre and Bayo complexes were shed into the NW part of the caldera. The coalescing structure formed by the Lazufre intumescence and Los Colorados caldera is conjugate at about 30 to the Pedernales-Arizaro overthrust, and has a NW-SE orientation, parallel to the Archibarca lineament. A SE to NW migration of volcanism is observed along this structure at least since the Middle Miocene. We proposed that, since Miocene, tectonic spaces with no surficial fault displacements and conjugated to the main compressive structures within the upper crust, have been created as a result of tensional stresses. Subsequently, the so increased lithostatic gradient could play a major role in the vertical traction of magma rising, favoring crustal assimilation processes. The available geochronological data indicate that the deformation that preceded the Los Colorados caldera occurred in a maximum period between 13 and 10 Ma.

  3. Highly extended terrains, lateral segmentation of the substratum, and basin development: The middle-late Miocene Radicondoli Basin (inner northern Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Brogi, Andrea; Liotta, Domenico

    2008-09-01

    This paper deals with the evolution of sedimentary basins not delimited by normal faults, with a substratum characterized by an upward concave shape and with infilling sediments synclinally deformed. We describe the middle-late Miocene Radicondoli Basin, representing an example of such bowl-shaped basins. Its tectonic origin is controversial, being related both to compression and extension; these opposite interpretations bear significant consequences on the geodynamic context in which the inner northern Apennines developed during the middle-late Miocene. The results of our structural studies, carried out in the substratum and infilling sediments, indicate that the Radicondoli Basin is an example of a hanging wall basin developed in an extensional setting. Extensional tectonics determined the lateral segmentation of the substratum competent levels (i.e., Tuscan Nappe and Verrucano Group) and the consequent collapse of overlying less competent levels (i.e., the Ligurian units) with the formation of a bowl-shaped tectonic depression. Here, the syntectonic sediments (Serravallian-late Messinian) are deformed in a large syncline, characterized by minor gravity-driven folds, with vergences toward the depocenter and traces of their axial planes parallel to the basin margins. This paper highlights the role of the competence contrast during the postcollisional tectonic evolution and the influence of substratum lateral segmentation for the accommodation of syntectonic sediments.

  4. Petrofacies and provenance of the Puente Formation (middle to upper Miocene), Los Angeles basin, southern California: Implications for rapid uplift and accumulation rates

    SciTech Connect

    Critelli, S.; Rumelhart, P.E.; Ingersoll, R.V.

    1995-10-02

    The Peunte Formation is a Middle-Upper Miocene clastic unit lying unconformably on the Lower-Middle Miocene El Modeno Volcanics and Topanga Group, in the Los Angeles basin. The Puente Formation, about 3900 m thick, is composed of conglomerate, sandstone, and mudrock deposit;ed as a submarine fan at bathyal depths. Several intrabasinal discordances suggest tectonic activity during deposition. The succession consists of two main upward-thickening and -coarsening megacycles, reflecting submarine-fan progradation. The Puente Formation is characterized up-section by: (1) thin-bedded sandstone and shale (La Vida member) grading to thick-bedded sandstone and conglomerate (Soquel Member); and (2) thin-bedded mudrock and sandstone (Yorba Member) grading to thick- to very thick-bedded sandstone and conglomerate (Sycamore Canyon Member). There is consistent provenance signal in spite of complex transportation tectonics, responsible for opening of the Los Angeles Basin, and later transpressional processes, which are still active. Detailed provenance study of the Puente Formation and related units provides important constraints on paleogeographic and paleotectonic reconstructions of southern California basins and uplifts.

  5. The occurrence of an abdominal fauna in an articulated tapir (Tapirus polkensis) from the Late Miocene Gray Fossil Site, Northeastern Tennessee.

    PubMed

    McConnell, Shannon M; Zavada, Michael S

    2013-03-01

    The analysis of samples recovered from the abdominal area of an articulated tapir (Tapirus polkensis) from the Late Miocene (4.5-7 million BP) Gray Fossil Site (GFS) revealed a rich palyno-fauna comprised of about 94% egg/oocyst-like structures and 6% pollen and other palynomorphs. In addition, a group of 6 hickory nuts (Carya) was recovered from the same area suggesting that the samples represent the abdominal contents. The analysis of a sample from immediately outside the tapir produced a sample with 98% pollen and less than 0.5% egg/oocyst-like structures. The size, shape, and general morphology of egg/oocyst-like structures were analyzed with light and scanning electron microscopy and were compared to a variety of intestinal parasites found in extant ungulates, and the Perissodactyla in particular. We also compared fossil structures to the numbers and kind of intestinal parasites recovered from fecal samples from the Baird's tapir (T. bairdii) in Costa Rica and from samples collected from the lowland tapir (T. terrestris) from Ecuador to assess their similarity to our fossil sample. Based on these data, we discuss what role parasites may have played in the biology of T. polkensis during the Late Miocene-Early Pliocene. PMID:23586562

  6. A new fossil thryonomyid from the Late Miocene of the United Arab Emirates and the origin of African cane rats

    NASA Astrophysics Data System (ADS)

    Kraatz, Brian P.; Bibi, Faysal; Hill, Andrew; Beech, Mark

    2013-05-01

    Cane rats (Thryonomyidae) are represented today by two species inhabiting sub-Saharan Africa. Their fossil record is predominately African, but includes several Miocene species from Arabia and continental Asia that represent dispersal events from Africa. For example, Paraulacodus indicus, known from the Miocene of Pakistan, is closely related to living Thryonomys. Here we describe a new thryonomyid, Protohummus dango, gen. et sp. nov., from the late Miocene Baynunah Formation of the United Arab Emirates. The new thryonomyid is less derived than " Thryonomys" asakomae from the latest Miocene of Ethiopia and clarifies the origin of crown Thryonomys and the evolutionary transition from Paraulacodus. A phylogenetic analysis shows Protohummus dango to be morphologically intermediate between Paraulacodus spp. and extinct and living Thryonomys spp. The morphological grade and phylogenetic position of Protohummus dango further supports previous biochronological estimates of the age of the Baynunah Formation (ca. 6-8 Ma).

  7. Absolute Paleointensity Study of Miocene Tiva Canyon Tuff, Yucca Mountain, Nevada

    NASA Astrophysics Data System (ADS)

    Patiman, A.; Bowles, J.

    2014-12-01

    Unoriented samples from the ~12.7 Ma Tiva Canyon (TC) tuff from Yucca Mountain, Nevada are studied in terms of magnetic properties and geomagnetic paleointensity. The magnetic mineralogy and magnetic properties of the TC tuff have previously been well documented, and the remanence-carrier in ~15-m thick zones at the top and bottom of the unit is dominantly is single domain (SD) to superparamagnetic (SP) magnetite, which may be considered ideal for absolute paleointensity studies. Among one of the several episodic volcanic eruptions of the Southwestern Nevada Volcanic Field (SWNVF), the welded TC tuff belongs to the Paintbrush Group. Here we present magnetic properties from two previously unreported sections of the TC tuff, as well as Thellier-type absolute paleointensity estimates. Samples were collected from the lower ~7 m at the base of the flow. Magnetic properties studied include hysteresis, bulk magnetic susceptibility, frequency-dependent susceptibility, and anhysteretic remanent magnetization acquisition. Magnetic property results are consistent with earlier work, showing that the main magnetic mineral is magnetite. SP samples are dominant from the lower ~1 m to ~3.6 m basal unit while the middle unit of ~3.7 m to 7.0 m mainly consists of SD samples. The paleointensity results are closely tied to the stratigraphic height and magnetic properties linked to domain state. The SD samples have consistent absolute paleointensity values 32.40±0.22 uT, VADM 5.74*1022 A.m2 and behaved ideally during paleointensity experiments. The SP samples have consistently higher paleointensity and less ideal behavior, but would likely pass many traditional quality-control tests. Since the magnetite has been interpreted to form by precipitation out of the glass post-emplacement, but at temperatures higher than the Curie temperature, we tentatively interpret the SD remanence to be a primary thermal remanent magnetization and the paleointensity result to be a valid estimate of geomagnetic paleointensity for the Miocene. Post-emplacement vapor-phase alteration might be expected to alter magnetic mineralogy and magnetization, and has been reported in the upper portions of the TC tuff, but not in the lower sections discussed here.

  8. Facies analysis of the Plateau Sandstones (Eocene to early Miocene?), Bako National Park, Sarawak, Malaysia

    NASA Astrophysics Data System (ADS)

    Johansson, M.

    1999-04-01

    Sandstones, located in the Kuching area, western Sarawak, are known as the 'Plateau Sandstones' (of possible Eocene to early Miocene age). However, based on a number of factors, including: (i) anomalous kerogene compositions; (ii) proximity of the on-lap surface; and (iii) palaeocurrent direction (generally to the NNE), it is thought that the sands exposed on the Bako Peninsula are unrelated to the Plateau Formation (located to the south of the Bako Penisula) and therefore a new name is coined; the Bako Sandstones, which form a subgroup of the Bako Sandstone Group. The Bako Sandstones form the Bako Peninsula, a flat-topped cliffed plateau which extends into the South China Sea at a latitude of 130'N. The plateau has a gently dipping surface, sloping northwards from a height of about 300 to 150 m. The sandstones form a succession of very thick bedded sandstones (up to 6 m thick), with lenses of conglomerates and subordinate sandy mudstones. The sandstones consist of pebbly coarse-medium grained sands, interbedded with polymictic pebble conglomerates. The sandstones are mainly lithic arenite, poorly to moderately sorted and consist of subangular to subrounded grains. Isolated pebbles are common throughout the sandstones. The most common structure in both sandstones and conglomerates is cross-bedding; planar cross-bedding and trough cross-bedding, together with thick sequences of climbing ripples. These structures suggest extensive tractional transport, forming both ripple and dune structures along the base of the channel. The geometry of the sands is either (i) lensoidal, or (ii) tabular, with the channel-fill interpreted as scour-fill channels or migrating dunes, respectively. Both types are commonly stacked vertically or amalgamate laterally to form thick interconnected units. The conglomeratic lenses, scour-fill features and rip-up shale clasts are related to higher energy erosional events, whilst the mud-draped ripples, ripple rejuvenation surfaces and two-tiered channel margins indicate a lower energy and stasis period. Slope instabilities at the channel margin are inferred from the slump structures present and shale clast slurries. The sandstones at Bako are thought to have formed within a braided channel environment (subject to exposure, from the presence of mud cracks within the formation).

  9. Magmatic Genesis Versus Evolution: the Tale of the Miocene - Pliocene Tuscan Magmatic Province

    NASA Astrophysics Data System (ADS)

    Poli, G.; Perugini, D.

    2007-12-01

    Miocene-Pliocene Tuscan Magmatic Province (TMP, Central Italy) reveals a complex magmatic setting with a large variety of volcanic and plutonic rock types closely associated in space and time (8-1 Ma). The main rock associations are represented by three group of rocks with different degree of evolution: i) mafic rocks with lamproitic, high-potassium calc-alkaline, and shoshonitic affinity; ii) intermediate rocks showing strong field, petrographic, and geochemical evidence of magma interaction processes; iii) felsic volcanics and intrusives showing petrological and geochemical characteristics of both extreme evolved and pure anatectic melts. Geochemical and thermodynamical characteristics of volcanic and plutonic rocks of TMP suggest a complex petrological evolution in which interaction between mafic and felsic magmas played a major role. The development of interaction processes between mafic and felsic magmas involves several evolutionary stages including the evolution of mafic magmas by Contamination and Fractional Crystallization (CFC) processes, once injected into the felsic reservoirs, followed by widespread mixing processes in magma chambers. Petrologic data indicate that felsic end-members are crustal anatectic melts derived by partial melting at ca 4-6 Kbar of a metasedimentary protolith constituting the Tuscan basement. Residual assemblages of the partial melting process, calculated by geochemical models, are consistent with experimental petrology data, and constraint the levels of emplacement for intrusive complexes, and the paths of extrusion for the effusive ones. Mafic end-members are compositionally akin to basic-intermediate magmas cropping out on the island of Capraia and to lamproites; such a variety of mafic magmas are found associated even in a single volcanic or plutonic complex, testifying for an extremely heterogeneous mantle source. The petrological model proposed in this work fits well with geophysical data. Starting from Middle Pliocene, western Tuscany underwent a strong regional uplift caused by an asthenospheric intrusion that thinned the crustal stack and completely restructured the crust-mantle boundary with possible intercalation of stack of high- level crust even in the lower crust. In response to the increasing heat flow both asthenosphere and heterogeneously metasomatized lithosphere melted to give basaltic magmas that either extruded or intruded and mixed with anatectic melts, the latter generated in the interlayered metasedimentary crustal stacks.

  10. Lower Miocene (Upper Ottnangian) sands in the Lower Austrian Molasse Basin

    NASA Astrophysics Data System (ADS)

    Palzer, Markus; Knierzinger, Wolfgang; Wagreich, Michael; Gier, Susanne; Meszar, Maria Elisabeth; Soliman, Ali

    2015-04-01

    In the Early Miocene (late Ottnangian), a global sea level drop and the continuous rise of the Alps lead to the regression of the Parathethys sea, and to the sedimentation of the Upper Freshwater Molasse. In the Lower Austrian Molasse Basin, this event is represented by yellowish-brownish to greyish white mica-rich and carbonate-free sands and silts with clayish interlayers, formerly called Oncophora Beds (OB), which crop out between St. Plten and Tulln. A new lithostratigraphy combines these sediments, now called Traisen-Formation (TF) together with the Dietersdorf Formation within the Pixendorf Group. Drill cores from OMV-wells predominantly from the NE show hundreds of meters thick sequences of pelites with intersections of sands interpreted as representing the OB. Contrary to the mainly brackish TF, a turbiditic marine deeper-water environment is inferred. An OMV-funded project investigates the relationship between these sediments, their stratigraphical and chronological range, provenance, facies and internal stratigraphy. First results from outcrops and several wells in the NE confirm large differences in grain size, structures and carbonate content. XRD-results indicate quartz, feldspar, muscovite, chlorite, calcite and dolomite as the main minerals within the sands and pelites. Pyrite is frequent. Halite and kaolinite occur. Whole rock chemistry, carbonate content measurements and biostratigraphic investigations of samples from the Wildendrnbach K4 well indicate, that these turbiditic OB can be divided into two sections: A lower fossil-free, carbonate poor and probably brackish (indicated by B/Al* and TOC/S) section with only few turbiditic very fine sands, and an upper microfossil bearing, marine section with carbonate contents up to 30% and more and coarser turbiditic sands. Therefore we use the working terms Lower and Upper Wildendrnbach Member (LWM, UWM). The lower part is enriched in (redox sensitive) heavy minerals such as Ce, Co, Cr, Cu, Gd, Ni, Pb, Sc, Zn and REE. It shows much lower constant Sr (about 140 ppm) values and B/Al* ratios (about 80) than the upper part (150 - 250 ppm; >120). The TOC/S ratio is much higher (17-23) in the LWM than in the UWM (>5). These two members can be correlated quite well by SP-logs over several wells. Therefore it can be concluded, that the lower part represents a period of salinity and carbonate crisis which may correspond to an (more or less) isolated deep basin probably poor in oxygen. At the beginning of the upper interval, a connection with the open sea was reestablished.

  11. Fluid-Rock Interaction in the Miocene Tejeda Caldera, Gran Canaria, Canary Islands

    NASA Astrophysics Data System (ADS)

    Donoghue, E.; Troll, V. R.; Harris, C.; Walter, T. R.; Prez Torrado, F. J.

    2007-12-01

    Rhyolite-trachyte tuffs deposited within the Miocene Tejeda caldera (Mogn Group 14-13.3Ma) show evidence of severe fluid-rock interaction. The altered tuffs are restricted to a peripheral zone directly inside the caldera margin, and occur at four distinct horizons within the mid-upper Mogn ignimbrite succession. Upper-Mogn tuffs display pervasive intermediate argillic alteration (smectite+illite+zeolites+adularia) and silicification (microcrystalline quartz+amorphous silica), indicative of low-temperature (?250C) near-neutral pH conditions. Quartz+kaolinite+muscovite+chlorite+calcite alteration of mid-Mogn tuffs and breccias may reflect boiling of higher-temperature, acidic hydrothermal fluids at depth. Si+Na+K+Pb+Sr+Rb were highly mobile during fluid-rock interaction, whereas Ti+Zr+Nb were dominantly refractory. Altered intra-caldera tuffs (n=65) have higher ?18O values than equivalent unaltered extra-caldera ignimbrites, reflecting an overall low-temperature near-surface environment in which meteoric water (?D ca.-15, ?18O ca.-3) was the dominant fluid source. A decrease in ?18O from upper- to mid- Mogn altered tuffs is consistent with an increase in fluid temperature with depth. Unaltered ignimbrites have ?D values of -110 to -168 (n=6) and ?0.2wt% H2O, indicative of Rayleigh-type H2O-exsolution. Altered tuffs have ?D values of -52 to -117 (n=75) and up to 4wt% H2O, reflecting interaction with steam (?D\\ll-15) or an evolved low-?D fluid. Apparently unaltered ignimbrites between altered horizons (n=13), and shield basalts directly outside the caldera margin (n=6), have elevated ?D and H2O values relative to equivalent unaltered rocks, indicative of minor alteration. Supported by numerical modelling, our Gran Canaria data reflect an intrusion-related, structurally controlled epithermal system, in which fluids and/or vapours migrated through intra-caldera tuffs via channelised, porous flow. This study may help to unravel the complex processes of fluid-rock interaction characteristic of both active and fossil caldera-hosted epithermal systems that are presently inaccessible or poorly exposed.

  12. Sexual dimorphism in Laccopithecus robustus, a late miocene hominoid from China.

    PubMed

    Pan, Y R; Waddle, D M; Fleagle, J G

    1989-06-01

    Laccopithecus robustus is a siamang-sized fossil ape from the Miocene site of Lufeng, China. The species is known from a partial cranium, numerous mandibles, and scores of isolated teeth. This species shows striking dental similarities to Pliopithecus from the Miocene of Europe and a number of cranial similarities to extant gibbons. Laccopithecus differs from extant gibbons and resembles other fossil and extant apes in showing marked sexual dimorphism in the size and shape of the canines and anterior lower premolars. Evidence for sexual differences in either the size or shape of other teeth is less clear. There is some evidence for a sexual size dimorphism based on the variability of molar teeth. PMID:2742002

  13. Eocene to post-Miocene kinematic evolution of the central Cyclades (Greece)

    NASA Astrophysics Data System (ADS)

    Draganits, E.; Huet, B.; Grasemann, B.; Schneider, D.; Ertl, A.

    2012-04-01

    Due to the extraordinary geotectonic location of the Aegean above an active subduction zone and an exceptional high seismicity, this area and especially the Cyclades have been in the focus of structural investigations for several decades. The present deformation is the result of ongoing plate tectonic movements in this area since at least the Miocene. The ductile structures of the Miocene extension and related metamorphic core type deformation are quite well studied and understood. Equally well investigated are the active tectonic deformation and associated brittle structures through several decades of seismic records. However, due to the difficulties of dating brittle faults, the kinematic evolution from the early to middle Miocene ductile structures, to later Miocene brittle-ductile and brittle faults is much less understood. For these reasons detailed structural fieldwork, combined with Ar-Ar geochronology and P-T studies, have been carried out on the uninhabited island of Despotiko, SW of Antiparos, which is situated virtually in the center of the Cycladic islands. This island has been selected because the existence of metamorphic rocks penetrated by Messinian rhyolite pipes and Pleistocene eolianites provide exceptional age constraints for Eocene to post-Miocene deformation structures. Despotiko is part of lower structural levels of the polymetamorphic Blueschist Unit of the Attic-Cycladic Metamorphic Belt and correlated lithologically with the Parikia gneisses and Marathi unit of Paros. Foliation is shallowly dipping towards the SSW. The main lithologies of the island, from the footwall to the hanging wall, consist of dark to pale grey, strongly foliated, mylonitic granite gneiss with abundant pegmatite dikes. The gneiss is overlain by prominent white, strongly foliated, mylonitic gneiss. Above are medium-grained, white calcite marble followed by greenish-white, mylonitic gneiss and an alternation of mica schist, greenschist, thin marble layers and some small serpentinite lenses. The structurally highest levels, in the south and southwest of the island, comprise several tens of meters of dolomite marble. This metamorphic succession has been cut by six Messinian rhyolitic volcanic vents and all crystalline rocks have been covered by late Pleistocene eolianites. The kinematic evolution of the investigation area can be divided based on the deformation style and age. (1) The ductile deformation results in NE-SW trending stretching lineation and shear senses both top-to NE and top-to SW. Ar-Ar white mica cooling ages indicate an early Miocene age for this ductile deformation. (2) The brittle/ductile structures, which gradually advance from the previous ductile deformation, start with small but pervasive flanking folds, followed by larger shear bands and finally faults with tourmaline slickenlines. The shear sense is consistently top-to SW with middle to late Miocene age constrained by Ar-Ar white mica cooling ages and zircon fission-track data from Paros. (3a) Large, subvertical, sinistral strike-slip faults cross-cut the metamorphic rocks and show up to hundreds of meters displacement. Late Miocene age is constrained by apatite fission-track data from Paros and the observation that these faults are sealed by Messinian rhyolites. (3b) The Messinian volcanic rocks are almost exclusively deformed by E-W striking conjugate brittle normal faults, which started already during the formation of the volcanic rocks. No unequivocal tectonic deformation structures have been observed in the Pleistocene eolianites.

  14. Faunal change in the Turkana Basin during the late Oligocene and Miocene.

    PubMed

    Leakey, Meave; Grossman, Ari; Gutiérrez, Mercedes; Fleagle, John G

    2011-01-01

    Faunal evolution over the last 65 million years of earth's history was dominated by mammalian radiations, but much of this era is poorly represented in Africa. Mammals first appeared early in the Mesozoic, living alongside dinosaurs for millions of years, but it was not until the extinction of dinosaurs 65 myr ago that the first major explosion of mammalian taxa took place. The Cenozoic (65 Ma to Recent) witnessed repeated and dynamic events involving the radiation, evolution, and extinction of mammalian faunas. Two of these events, each marking the extinction of one diverse fauna and subsequent establishment of another equally diverse fauna, both involving advanced catarrhine primates, are recorded in sites in the Turkana Basin, despite the poorly represented record of Cenozoic faunas elsewhere in sub-Saharan Africa. The first of these events occurred at the Oligocene-Miocene transition and the other at the Miocene-Pliocene transition. PMID:22170693

  15. Some palynological aspects of Oligocene to Early Miocene transition Southern Alaska

    SciTech Connect

    Wiggins, V.D.

    1985-04-01

    The Oligocene to early Miocene transition in southern Alaska perhaps represents one of the most dramatic floristic changes in the entire Tertiary of Alaska. The basic modification is from a dominant deciduous, broadleaved forest biome in the late Eocene - early Oligocene (early Zemorrian) to a dominant moist, temperate, coniferous forest biome in the early Miocene (Saucesian). A similar change can be seen between the deciduous broad-leaved forests and the montane boreal coniferous forest of China today. This change in flora - and from a palynological perspective this change in microflora - reflects the onset of global cooling in the Neogene and the concurrent change from a dominant marine transgressive to a dominant nonmarine regressive mode of sedimentation.

  16. Depositional and structural evolution of the Middle Miocene depositional episode, east-central Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Combellas Bigott, Ricardo Ignacio

    Two widespread, transgressive deposits associated with the faunal top Amphistegina B (15.5 Ma) and Textularia W (12.1 Ma) define the Middle Miocene depositional episode. An extensive stratigraphic correlation framework established in this study allowed tracing of the middle Miocene sediment dispersal system from the shelf through the slope to the basin floor in the complex paleogeography of the east-central Gulf of Mexico. The Middle Miocene depositional episode is recorded in four genetic cycles (1 to 2 Ma), bounded by regional maximum flooding surfaces in the shelf and shelf margin setting, and three equivalent seismic sequences punctuated by condensed sections in the slope and basin floor. Two principal, long-lived extrabasinal fluvial/delta axes, the ancestral Mississippi and the Tennessee systems, provided the bulk of sediments that infilled the middle Miocene depocenters. Salt-related structural provinces controlled the configuration of the depocenters. Structural linked systems, dominated by gravity spreading, and a minibasin province, driven by differential subsidence, were established during the Middle Miocene depositional episode. Sediment supply coupled with wave energy flux, high-frequency sea-level changes, and salt tectonism determined the time and space distribution of progradation, aggradation, and retrogradation of system tracts. Middle Miocene shelf margins have prograded 20 to 40 miles from the relict lower Miocene shelf margin. Two depositional systems tracts characterize the constructional shelf margin: (1) a mixed-load fluvial-dominated platform delta/shelf-margin delta/delta-fed apron systems tract; and (2) a strandplain/shelf/muddy slope systems tract. However, the constructional, offlapping shelf margin systems were locally punctuated by a large-scale phase of retreat and erosion, named the Harang collapse system, in which a large volume of sediments bypassed the shelf margin to be deposited on the slope and basin floor. The Harang collapse system is a type of large-scale slope failure produced by massive salt-withdrawal, retreat of major delta systems, and high-frequency sea-level fluctuations. A large volume of sediment bypassed the confined minibasin province and the unconfined Florida slope at the flank of active deltaic depocenters, forming the long-lived MCAVLU submarine fan system (named for its location beneath the Mississippi Canyon, Atwater Valley, and Lund continental shelf (OCS areas) in the linked, primary minibasin corridor of the lower slope and basin floor. The MCAVLU submarine fan system evolved from a structurally-controlled, elongate sand-rich to mixed sand/mud fan to a large radial, mixed sand/mud fan. Significant untapped middle Miocene hydrocarbon resources remain in the confined channel fills and lobes of the Harang collapse system and sand-rich ponded facies assemblages of the MCAVLU submarine fan system.

  17. Geopressured geothermal resource potential of Miocene Bayou Hebert Prospect, Vermilion and Iberia parishes, Louisiana

    SciTech Connect

    McCulloh, R.P.; Pino, M.A.; Bebout, D.G.; Bachman, A.L.

    1981-01-01

    The Bayou Hebert prospect is a fault-bounded block of lower Miocene shale and sandstone which covers a 75-square-mile area in southeastern Vermilion and southwestern Iberia parishes, southwestern Louisiana. The average depth to the top of the geopressured zone is 12,500 feet. Detailed correlation of shale resistivity patterns on well logs from this area has delineated faults, local unconformities, and changes in thickness and facies of lithologic units. Most faults revealed by this method are associated with the boundary fault zones, but the few delineated in the interior of the prospect could reduce the volume of potential reservoir units. Cross sections show that the lower Miocene section thickens across growth faults by addition of new units as well as by expansion. Of the parameters of reservoir volume, salinity, temperature, and permeability, reservoir volume shows the most significant variation and indicates that the eastern fourth of the prospect has the most geopressured geothermal potential.

  18. Sr-isotopic, paleomagnetic, and biostratigraphic calibration of horse evolution: Evidence from the Miocene of Florida

    SciTech Connect

    MacFadden, B.J.; Bryant, J.D.; Mueller, P.A. )

    1991-03-01

    During the middle Miocene an explosive adaptive radiation resulted in the advent of grazing horses with high-crowned teeth in North America. New Sr isotopic, paleomagnetic, and biostratigrahic evidence from the Miocene marine and nonmarine sequence of the Florida panhandle calibrates the base of this adaptive radiation. The transition from the primitive outgroup species 'Parahippus' leonensis to the most primitive high-crowned horse, 'Merychippus' gunteri occured after about 17.7 Ma. After this event, the lowest known stratigraphic level at which diversification (i.e., presence of two or more sympatric species) of grazing merychippine horses occurs is about 16.2 Ma, or within the early part of Chron C5BR. Although this currently is the only sequence where the parahippine-merychippine transition is directly calibrated, biochronologic evidence from other important, contemporaneous localities in Texas, Nebraska, and California indicate that diversification occured rapidly throughout North America between 15 and 16 Ma.

  19. Late Miocene hominin teeth from the Gona Paleoanthropological Research Project area, Afar, Ethiopia.

    PubMed

    Simpson, Scott W; Kleinsasser, Lynnette; Quade, Jay; Levin, Naomi E; McIntosh, William C; Dunbar, Nelia; Semaw, Sileshi; Rogers, Michael J

    2015-04-01

    Since 2000, significant collections of Latest Miocene hominin fossils have been recovered from Chad, Kenya, and Ethiopia. These fossils have provided a better understanding of earliest hominin biology and context. Here, we describe five hominin teeth from two periods (ca. 5.4Million-years-ago and ca. 6.3Ma) that were recovered from the Adu-Asa Formation in the Gona Paleoanthropological Research Project area in the Afar, Ethiopia that we assign to either Hominina, gen. et sp. indet. or Ardipithecus kadabba. These specimens are compared with extant African ape and other Latest Miocene and Early Pliocene hominin teeth. The derived morphology of the large, non-sectorial maxillary canine and mandibular third premolar links them with later hominins and they are phenetically distinguishable and thus phyletically distinct from extant apes. PMID:25795338

  20. Palynology of the Heath Formation (Miocene) from the Progreso Basin, Peru

    SciTech Connect

    Engelhardt, D.W. ); Wood, G.D. )

    1993-02-01

    A diverse and well preserved assemblage of pollen, spores, dinoflagellates, and acritarchs were recovered from outcrop samples of the Heath Formation, exposed along Bocapan Creek near Tumbes, Peru. The pollen and spores include representatives of Arecipites, Bombacacidites, Caryapollenites, Cicatricosisporites, Couperipollis, Cyathidites, Diporisporites, Distaverrusporites, Dyadosporites, Echiperiporites, Faramea, Foveodiporites, Foveotriletes, Fusiformisporites, Gothanipollis, Granitricolpites, Hymenophyllum, Hexpollenties, Involutisporites, Laevigatosporites, Lygodiumsporites, Magniperiporites, Malvacearumpollis, Monocolpopollenites, Perissyncolporites, Peritheciumites, Phragmothyrites, Polyadadporites, Polypodiaceisporites, Polypodiisporites, Retibrevitricolpites, Striadisporites, Tetracolporites, Tricolporopollenties, and Verrucosisporites. Plankton are assignable to Lejeunecysta, Operculodinium, Pterospermella, Selenopemphix, Spiniferites, Sumatradinium, Tythodiscus, and Tuberculodinium. The palynomorph assemblage can be placed in the Early Miocene based on the co-occurrence of Cicatricosisporites dorogensis, Couperipollis rarispinosus, Echiperiporites estelae, Magniperiporites echinatus, Perisyncolporites porkornii, Polypodiaceoisporites minor, P. potoniei, Reticolporites guianesnsis, R. irregularis, Scabriporites asymetricus, Selenopemphix nephroides and Tuberculodinium vancampoae. This is an agreement with foraminiferal evidence which positions the Heath Formation in the Early Miocene Catapsydrax dissimilis, Catapsydrax stainforthi and oldest portion of the Globigerinatella insueta zones.

  1. Basal Adare volcanics, Robertson Bay, North Victoria Land, Antarctica: Late Miocene intraplate basalts of subaqueous origin

    USGS Publications Warehouse

    Mortimer, N.; Dunlap, W.J.; Isaac, M.J.; Sutherland, R.P.; Faure, K.

    2007-01-01

    Late Cenozoic lavas and associated hyaloclastite breccias of the Adare volcanics (Hallett volcanic province) in Robertson Bay, North Victoria Land rest unconformably on Paleozoic greywackes. Abundant hyaloclastite breccias are confined to a paleovalley; their primary geological features, and the stable isotope ratios of secondary minerals, are consistent with eruption in a subaqueous environment with calcite formation probably involving seawater. In contrast, the lavas which stratigraphically overlie the hyaloclastites on Mayr Spur probably were erupted subaerially. K-Ar dating of eight samples from this basal sequence confirms the known older age limit (Late Miocene) of the Hallett volcanic province. Geochemical data reveal an ocean island basalt-like affinity, similar to other Cenozoic igneous rocks of the Hallett volcanic province. If a submarine eruptive paleoenvironment is accepted then there has been net tectonic or isostatic post-Late Miocene uplift of a few hundred metres in the Robertson Bay-Adare Peninsula area

  2. A Toba-scale eruption in the Early Miocene: The Semilir eruption, East Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Smyth, Helen R.; Crowley, Quentin G.; Hall, Robert; Kinny, Peter D.; Hamilton, P. Joseph; Schmidt, Daniela N.

    2011-10-01

    The Indonesian archipelago is well-known for volcanic activity and has been the location of three catastrophic eruptions in the last million years: Krakatau, Tambora and Toba. However, there are no reports of large magnitude eruptions during the earlier Cenozoic despite a long volcanic record in Indonesia during subduction of Indian Ocean lithosphere since the Eocene. Here we report an Early Miocene major eruption, the Semilir eruption, in south Java, the main phase of which occurred at 20.7 ± 0.02 Ma. This major volcanic eruption appears similar in scale, but not in type, to the 74 ka Toba event. Its products can be identified elsewhere in Java and are likely to have been distributed widely in SE Asia and adjacent oceans. The Semilir eruption could have triggered a climate response, but cannot yet be linked with certainty to Early Miocene climatic events such as glaciations.

  3. Terpenoids Preserved in Fossils from Miocene-aged Japanese Conifer Wood.

    PubMed

    Ludwiczuk, Agnieszka; Asakawa, Yoshinori

    2015-06-01

    The compositions of terpenoids from the solvent extracts of two silicified wood samples were analyzed using a GC/MS method. Chromatographic analysis showed that several biomolecules were preserved unaltered in the Miocene-aged Japanese wood. These were ?-terpineol, ?-cedrene, thujopsene, widdrol and ferruginol, among others. In addition to the bioterpenoids, the fossil woods contained a series of geoterpenoids that were generated from their biological precursors before and after burial. These were cadalene, daucalene, pseudowiddrene and cuparene. The chemical composition of both analyzed fossil samples suggest that the silicified woods collected in the Noto Peninsula belong to the Cupressaceae family; this was confirmed by morphological analysis. Both samples were identified as Taxodioxylon cunninghamioides, which is the most common Miocene wood in Japan. PMID:26197549

  4. Sensitivity of climate and Atlantic overturning circulation to uncertain ocean gateway configurations for the late Miocene

    NASA Astrophysics Data System (ADS)

    Bradshaw, C.; Lunt, D. J.; Flecker, R.; Martinez-Mendez, G.

    2013-12-01

    The palaeorecord documents late Miocene (11.6-5.3 Ma) climate to be much warmer and wetter than today yet CO2 reconstructions are similar to modern levels. Given the apparent decoupling between CO2 and warmth for this period we investigate here the role of the oceans. The late Miocene experienced significant tectonic change including the restriction of some of the last ocean gateways to close (Panama Gateway and Indonesian Seaway) and open (Bering Strait and Barents/Kara Sea). However, the timing and configuration of these tectonic changes is uncertain. The final closure of the Panama Gateway is dated to the Pliocene, but continental mammal exchange suggests the existence of a Central American archipelago from the mid-late Miocene. The Bering Strait is typically assumed to have opened at the very end of the late Miocene/early Pliocene based on diatom exchange, but other marine and terrestrial evidence points to a much earlier, perhaps intermittent, opening. The timing of the restriction of the Indonesian Seaway is very poorly constrained at middle Miocene to Pliocene. The Barents Sea and Kara Sea shelves are documented as having being subject to extensive glacial erosion and post-glacial uplift since the Pliocene and throughout the Quaternary but records of uplift and erosion during the earlier Cenozoic are limited. However, the presence of significant preglacial sediments suggests that this region underwent tectonic uplift, volcanism and subsequent erosion during the Eocene-Miocene period although the age assignment of the data remains controversial. The Panama Gateway has been suggested to influence North Atlantic Deep Water (NADW) production through numerous modelling studies, the Bering Strait has been suggested to greatly impact NADW during the Quaternary, and the strength of Indonesian Throughflow is hypothesised to influence Agulhas Leakage, which, in turn, has been speculated to influence Atlantic meridional overturning and thus NADW production. Here, we investigate how the opening and closing of these gateways might influence ocean circulation, and hence climate, with late Miocene boundary conditions using the fully coupled atmosphere-ocean-vegetation GCM HadCM3L with TRIFFID. We show how the model suggests these gateways in different configurations might influence NADW production, with results from all possible combinations of these three gateways presented and compared to the available proxy data. The climatic implications of the presence of the Barents Shelf and Kara Shelf land masses prior to their final erosion has not been the subject of much research, either through modelling or data interpretation, and indeed many model simulations for the Miocene do not include these shelves as land masses at all. Here we also test our hypothesis that these land masses also impact NADW production through the restriction of the exchange of water between the Arctic Ocean and the Greenland-Iceland-Norwegian Sea. We hypothesize that their presence as land masses results in a saltier North Atlantic than occurs after their erosion; without the land masses there, the North Atlantic would experience more influence from the East Greenland Current (colder/fresher) and less influence of the Irminger Current (warmer/saltier).

  5. The interaction between Aegean back-arc extension and Anatolia escape since Middle Miocene

    NASA Astrophysics Data System (ADS)

    Philippon, Mlody; Brun, Jean-Pierre; Gueydan, Frdric; Sokoutis, Dimitrios

    2014-09-01

    The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape of Anatolia. Lithosphere-scale analogue models were employed to display that the overall pattern of Aegean extension requires not only the combination of trench retreat and Anatolia escape since middle Miocene but also the presence of an inherited lithosphere-scale mechanical discontinuity: the Vardar Suture Zone (VSZ). The reactivation in dextral shear of the eastern branch of the VSZ accommodates both the trench retreat (NS stretching) and the westward escape of Anatolia (EW shortening) in the Cyclades area since middle Miocene. Additionally, our model shows that the North Anatolian Fault (NAF) is a late structure in the evolution of the Aegean, initiated around 10 Ma after the onset of Anatolia escape. The displacement field at the surface of the model allows the identification of sub-domains, which result from strain partitioning instead of being rigid microplates, directly comparable to the present-day displacement field (GPS) of the Aegean and western Anatolia. Our model provides a simple but powerful way to look at the dynamics of Aegean extension in two main stages. From middle Eocene to middle Miocene, extension was only driven by the southward retreat of the Hellenic trench at a rate lower than 1 cmy- 1. Since middle Miocene, the combination of slab rollback with Anatolia westward escape resulted in a southwest direction of trench retreat, with an accelerating rate of up to 3 cmy- 1.

  6. A new Late Miocene hominoid from Kenya: Samburupithecus kiptalami gen. et sp. nov.

    NASA Astrophysics Data System (ADS)

    Ishida, Hidemi; Pickford, Martin

    1997-11-01

    A new genus and species of hominoid, Samburupithecus kiptalami, is erected on the basis of a maxillary specimen with complete post canine dentition. Its age is established as upper Miocene (9.5 Ma) on the basis of radioisotopic dating and associated mammalian fauna. The new genus is more closely related to the African ape human clade (AAH) than is any other known extinct hominoid and it may well be on the line leading to hominids.

  7. Paleoenvironmental conditions in the Spanish Miocene-Pliocene boundary: isotopic analyses of Hipparion dental enamel.

    PubMed

    Domingo, Laura; Grimes, Stephen T; Domingo, M Soledad; Alberdi, M Teresa

    2009-04-01

    Expansion of C(4) grasses during Late Miocene and Early Pliocene constitutes one of the most remarkable biotic events of the Cenozoic era. The Teruel-Alfambra region (northeastern Spain) contains one of the most complete Miocene-Pliocene sequences of mammalian fossil sites in the world. In this study, stable isotope (delta (13)C and delta (18)O) analyses have been performed on the tooth enamel from the equid Hipparion from 19 localities spanning a time interval from approximately 10.9 to 2.7 Ma. This time range starts with the first appearance of this genus in Spain and ends at its extinction. An increase in delta (13)C at about 4.2 Ma has been observed, indicative of a shift toward a more open habitat. This shift may be related to a large scale vegetation change which occurred across the Miocene-Pliocene boundary when C(4) grasses expanded. This expansion might in turn be linked to global tectonic events such as the uplift of the Himalaya and/or the closure of the Panama Isthmus. However, other more regional factors may have ultimately enhanced the trend toward more open habitats in the Western Mediterranean Basin. The Messinian Salinity Crisis was a major environmental event that may have been responsible for the isotopic changes seen in the equid Hipparion from the Iberian Peninsula along with an increase in the aridity detected approximately 4.6 Ma ago in the Sahara. Even though the exact factor triggering the isotopic change observed in the Hipparion enamel remains mostly unknown, this study demonstrates that the global environmental changes detected across the Miocene-Pliocene boundary are also recorded in the realm of the Iberian Peninsula. PMID:19190888

  8. A Miocene termite nest from southern Argentina and its paleoclimatological implications

    USGS Publications Warehouse

    Bown, T.M.; Laza, J.H.

    1990-01-01

    A Miocene termitarium attributable to the extant termite Syntermes (Isoptera: Termitidae, Nasutitermitinae) is the first fossil termite nest reported from South America and possibly the oldest record of the Isoptera from that continent. A new ichnogenus and ichnospecies, Syntermesichnus fontanae, is proposed for this distinctive trace fossil. It differs from nests constructed by other members of the Nasutitermitinae in its architectural organization and its large size. -from Authors

  9. The Miocene Cyprideis species flock (Ostracoda; Crustacea) of western Amazonia (Solimões Formation)

    NASA Astrophysics Data System (ADS)

    Gross, Martin; Ramos, Maria Ines F.; Piller, Werner E.

    2015-04-01

    The Miocene mega-wetland of western Amazonia holds a diverse, largely endemic aquatic invertebrate fauna (e.g., molluscs, ostracods). Among ostracods, the genus Cyprideis experienced a remarkable radiation. Micropalaeontologic investigations of a 400-m-long sediment core (~62 km SW Benjamin Constant, Amazonia, Brazil) permitted a taxonomic revision of about two-thirds of hitherto described Cyprideis species. Ostracod index species enabled a biostratigraphic allocation of the well succession to the Cyprideis minipunctata to Cyprideis cyrtoma biozones (late middle to early late Miocene age). The current study underlines once more Cyprideis' remarkable capability to produce species flocks and western Amazonian Cyprideis comply with the criteria of a species flock: i) endemicity: up to now not a single species is recorded in adjacent areas; ii) monophyly: although hardly verifiable to date and probably Amazonian Cyprideis is not monophyletic s.str., several closely related, quite rapidly evolving species are proved; iii) speciosity: due to the present study, 30 formally described species exist; several further species, left in open nomenclature, are recorded in the literature, which strongly hints to a much higher, still unrecorded species richness; iv) ecological diversity: based on rare sedimentologic cross-references, ecological diversity within a highly structured wetland is possible; the current results demonstrate the sympatric occurrence of up to 12 Cyprideis species, which may indicate adaptations to different microhabitats; v) habitat dominance: regularly Cyprideis holds more than >90 % in western Amazonian ostracod assemblages during the early and middle Miocene. Explanations for this extreme habitat monopolisation are still arguable and touch the highly disputed question about the nature of western Amazonia's environments during the Miocene. It seems, however, evident that a strictly actualistic approach to endemic Neogene Amazonian biota is highly problematic. This study was funded by Austrian Science Fund (FWF project P21748-N21).

  10. Miocene to Recent structural evolution of the Nevado de Toluca volcano region, Central Mexico

    NASA Astrophysics Data System (ADS)

    García-Palomo, A.; Macías, J. L.; Garduño, V. H.

    2000-03-01

    Based on aerial photography, satellite imagery, and detailed field work, a geological and structural model of Nevado de Toluca and its surroundings is presented. The Nevado de Toluca volcano is built upon the intersection of three complex fault systems of different age, orientation, and kinematics. These systems from the older to the younger are: (a) The Taxco-Querétaro Fault System (NNW-SSE) with clear expression south of the volcano; (b) The San Antonio Fault System (NE-SW) that runs between the San Antonio and Nevado de Toluca volcanoes; and (c) The Tenango Fault System (E-W) located to the east of Nevado de Toluca volcano. Our field data, supported by previous studies, suggest that these systems have coexisted since the late Miocene. In addition, the stratigraphy, chronology, and kinematics of fault planes point to the existence of at least three main deformation events that have affected the region since the late Miocene. During the early Miocene, an extensional phase with the same deformation style as the Basin and Range tectonics of northern Mexico caused the formation of horsts and grabens south of Nevado de Toluca and allowed the intrusion of sub-vertical dikes oriented NW-SE and NNW-SSE. During the middle Miocene, a transcurrent episode generated NE-SW faults that presented two main motions: the first movement was left-lateral with a σ3 oriented NW-SE and later turned into normal through a counter-clockwise rotation of σ3 up to a N-S position. The latest deformation phase started during the late Pliocene and produced oblique extension ( σ3 oriented NE-SW) along E-W-trending faults that later changed to pure extension by shifting of σ3 to a N-S orientation. These faults appear to control the late Pleistocene to Holocene monogenetic volcanism, the flank collapses of Nevado de Toluca volcano and the seismic activity of the region.

  11. Etisus evamuellerae, a new xanthid crab (Decapoda, Brachyura) from the Middle Miocene of Austria and Hungary

    PubMed Central

    Hyžný, M.; van Bakel, B.W.M.; Guinot, D.

    2015-01-01

    On the basis of several carapaces, a new species of xanthid crab, Etisus evamuellerae, is described from the Middle Miocene of the Vienna (Austria) and Great Hungarian basins. It differs from the coeval xanthids, Xantho moldavicus and Pilodius vulgaris, in having a distinctly protruding front and comparatively longer carapace. Contrary to those two species, the new one makes up for just a small percentage in the decapod crustacean assemblages studied. PMID:25983383

  12. Miocene Antarctic ice sheet simulations using an asynchronously coupled RCM-ISM

    NASA Astrophysics Data System (ADS)

    Gasson, Edward; DeConto, Rob; Pollard, David

    2015-04-01

    Both direct and indirect evidence suggests that there was fluctuation of the Antarctic ice sheet over the past 34 million years. For example, sediment provenance studies suggest retreat into the Wilkes Subglacial Basin during the Pliocene and possibly earlier, in the Miocene. Indirect evidence, such as from the oxygen isotope record from benthic formanifera, suggests fluctuations in ice volume exceeding 50 m in sea level equivalence during the Miocene. Ice sheet models have struggled to achieve such large-scale retreat under the relatively modest atmospheric CO2 concentrations suggested by proxy records. Attempts to resolve this data-model conflict have recently focused on simulating retreat into the marine basins of Antarctica, with retreat into the Wilkes Subglacial Basin during the Pliocene simulated in 2 recent ice sheet modeling studies using different approaches. Although retreat into the subglacial basins may explain approximately 20 m of ice volume fluctuation from Antarctica, it is still lower than the magnitudes suggested by the oxygen isotope record for the Miocene. Here we focus on improving simulation of the Antarctic ablation zone by using an asynchronously coupled RCM to provide climate forcing to an ice sheet model. We use a GCM with a Miocene paleo-geography to provide boundary forcing for the RCM, with atmospheric CO2 at various concentrations. In previous simulations there was limited retreat of the ice sheet away from the continental margin, due to a strong hysteresis mechanism. In these asynchronous simulations there is increased retreat of the Antarctic ice sheet, with continental sectors retreating away from the continental margin. This results in a greater overall decrease in ice volume than for non-asynchronously coupled simulations.

  13. A new Middle Miocene Niveria Jousseaume, 1884 (Mollusca: Gastropoda: Trivioidea) from Hungary

    NASA Astrophysics Data System (ADS)

    Fehse, Dirk

    2011-02-01

    A new species of Niveria from the Middle Miocene (Badenian) of the Paratethys of Borsodbóta, Hungary is described. This species is characterized by its callused dorsum and dorsal depression. Niveria jozefgregoi sp. nov. is discussed with comparative species from the Badenian of Hungary, the Pliocene of the Mediterranean region, Florida and Recent species from Madeira and the Islas Galápagos.

  14. Middle Miocene hiatus in volcanic activity in the Great Basin area of the Western United States

    USGS Publications Warehouse

    McKee, E.H.; Noble, D.C.; Silberman, M.L.

    1970-01-01

    A summary of potassium-argon dates shows that a high level of igneous activity in the Great Basin and adjacent regions during middle Tertiary time (40 to 20 my ago) was followed by a period of relative quiescence in middle Miocene time that lasted for several million years (from 20 to 17 my ago). Volcanism resumed 16 my ago mainly at the margins of the region and has continued to the present. ?? 1970.

  15. Sporopollen evidence for Late Miocene stepwise aridification on the Northeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Liu, J.; Li, J. J.; Song, C. H.; Yu, H.; Peng, T. J.; Hui, Z. C.; Ye, X. Y.

    2015-11-01

    Holding a climatically and geologically key position both regionally and globally, the northeastern Tibetan Plateau provides a natural laboratory for understanding the interactions between tectonic activity and the evolution of Asian aridification. Determining when and how the Late Miocene climate evolved on the northeastern Tibetan Plateau may help us understand better relations between tectonic uplift, global cooling and ecosystem evolution. Previous paleoenvironmental research has focused on the western Longzhong Basin. Late Miocene aridification data derived from sporopollen now requires corroborative evidence from the eastern Longzhong Basin. Here, we present a Late Miocene sporopollen record from the Tianshui Basin in the eastern Longzhong Basin. Our results show a two-stage stepwise aridification: a temperate forest with a more humid climate developed in the basin between 11.4 and 10.1 Ma, followed by a temperate open forest environment with a less humid climate between 10.1 and 7.4 Ma; and an open temperate forest-steppe environment with a relatively arid climate occupied the basin during 7.4 to 6.4 Ma. The vegetation succession demonstrates that Asian aridification occurred after ~ 7-8 Ma, which is confirmed by other evidence from Asia. Furthermore, this persistent aridification on the northeastern Tibetan Plateau parallels the global cooling of the Late Miocene; the stepwise vegetation succession is consistent with the major uplift of the northeastern Tibetan Plateau during this time. These integrated environmental proxies indicate that global cooling may have been a potential driving force for Asian interior aridification, most likely enhanced by stepwise uplift of the Tibetan Plateau.

  16. Plate kinematics of the central Atlantic during the Oligocene and early Miocene

    NASA Astrophysics Data System (ADS)

    Schettino, Antonio; Macchiavelli, Chiara

    2016-04-01

    A new plate motions model for the northwest Africa-North America Plate pair during the Oligocene and early Miocene is presented. The model is accompanied by a high-resolution isochron map for the central Atlantic region, resulting from a re-examination of 423 ship tracks from the NGDC data base for the area between the 15°20' FZ and the Azores triple junction. A new digital model of fracture zones for this region and a set of 309 magnetic profiles crossing the Oligocene to recent oceanic crust within the study area allowed to determine accurate finite reconstruction poles for the North America-northwest Africa conjugate plate pair between the early Miocene (Chron 6) and the early Oligocene (Chron 13). For times older than Chron 7 (˜25 Ma), the finite reconstruction poles were calculated using a reliable data set coming exclusively from the region south of the Canary Islands FZ (˜32°N), which allowed to test the rigidity of the northwest African oceanic lithosphere during the Oligocene-early Miocene phase of Atlas orogeny. A comparison of theoretical magnetic isochrons with observed magnetic lineations systematically shows that anomalously high spreading rates occurred in the area north of the Canary Islands FZ before Chron 7, thereby suggesting that the formation of the Atlas mountain, rather than being a localized intracontinental process, was logically linked to the central Atlantic spreading history. Thus, an independent Moroccan Plate could have existed during the Oligocene-early Miocene time interval, which included both the oceanic lithosphere north of the Canary Islands FZ and the northern Maghrebian areas of Morocco, Algeria and Tunisia. In this eventuality, the Atlas mountain belt should be reinterpreted as a giant flower structure associated with dextral transpression.

  17. Paleomagnetic evidence for Late Miocene counterclockwise rotation of north coast carbonate sequence, Puerto Rico

    SciTech Connect

    Reid, J.A.; Plumley, P.W. ); Schellekens, J.H. )

    1991-03-01

    A paleomagnetic study of the essentially undeformed middle Tertiary carbonate sequence along the north coast of Puerto Rico reveals statistically significant pre-Pliocene discordance of characteristic component directions against those expected from cratonic North America for much of the section. Despite generally weak to moderately weak magnetic intensities, confirmation of the magnetization as primary in origin comes from the presence of two distinct components of magnetization, intrasite bipolarity, and/or the reproducibility of measurements. The mean geographic direction for the upper Oligocene to middle Miocene strata is 335.2{degree}/32.9{degree} and the corrected mean paleomagnetic pole is 207.6{degree}/66.5{degree}, (N = 3, {alpha}95 = 4.3{degree}). This suggests a counter-clockwise (CCW) block rotation of Puerto Rico and its microplate of 24.5{degrees} ({plus minus} 5.8{degrees}) during the late Miocene. Using a width of 250 km for the Northern Caribbean Plate Boundary Zone (NCPBZ) between the North American Plate and Caribbean Plate, the mean left lateral displacement implied is 1.8 to 2.4 cm/yr, which agrees fairly well with published relative motion rates for the two plates. Average rotation rate for 50 Ma to 20 Ma was 0.7{degree}/my but perhaps as great as 4{degree}/my in the Miocene. Resolution of mean paleolatitude indicates northward motion of a degree or less during the period of rotation. Causes of this short-lived rotation may include (1) tectonic escape from the inhibiting presence of the Bahama Banks and Beata Ridge during eastward motion of Puerto Rico along the sinistral transpressive Puerto Rico Trench and Muertos Trough fault systems or (2) changes in relative plate motions of the Caribbean and North American Plate during the late Miocene.

  18. From middle Miocene to late Quaternary spatial and temporal evolution of Cappadocian Volcanism

    NASA Astrophysics Data System (ADS)

    Aydar, E.; Cubukcu, E.; Ersoy, O.; Kabaday?, E.; Duncan, R.

    2009-04-01

    Cappadocian Volcanism, Central Turkey was active from Miocene to upper Holocene, originating from varying sources and presents various dynamics. Central Anatolia constitutes a plateau reaching to 1100-1200 meters from the sea level. From Miocene to Quaternary, the volcanism and/or its relationships with local tectonic targeted in numerous works. Those works can be classified as follows: (i) volcanism-tectonic relationship (Pasquare et al, 1988; Toprak and Goncuoglu, 1993; Toprak, 1998, Dhont et al, 1998; Froger et al, 1998), (ii) volcanological, petrological, geochemical works on stratovolcanoes, monogenetic vents, ignimbrites (Batum, 1978; Ercan, 1985; Aydar, 1992; Aydar and Gourgaud, 1993; Aydar et al, 1994; Aydar et al, 1995; Le Pennec et al, 1994; Druitt et al, 1995; Aydar and Gourgaud, 1998; Deniel et al, 1998, Temel, 1998; Kuzucuoglu et al, 1998; Mouralis et al, 2002; Sen et al, 2003) (iii) Geophysical works on the missing calderas (Ongur, 1978; Ekingen, 1982; Froger et al,1998). Cappadocian landscape is made principally of eroded ignimbirites forming fair chimneys. Apart from the ignimbrites, Cappadocia bears several stratovolcanoes (Mt Erciyes, Mt. Hasan) and numerous monogenetic vents (cinder cones, maars, domes) and some andesitic dacitic relicts of lava fields intercalated within the ignimbritic sequence. Although the stratovolcanoes have some historical activities, their initial eruptions occured in Miocene (Kecikalesi stage of Mt Hasan- 13 My), Pliocene (Kocdag stage of Mt Erciyes). The monogenetic vents demonstrate interestingly bi-modal character which is typically found in rifted regions of the world. Origin of this young volcanism is proposed as collision related transitional alkaline-calcalkaline association (Aydar, 1992, Deniel et al, 1998), is also linked to the subduction (Olanca, 1994). Our preliminary data on the Quaternary rhyolitic glass combined with chemical analysis of the Miocene volcanics exhibit that a slight transition from peraluminious to metaluminious toward a rough peralkaline character of volcanics with time. A Rifting (?) occurs and its evolution is unknown and in the frame of this work, a detailed geochronology and geochemistry will be proposed.

  19. Coconuts in Miocene turbidites in New Zealand Possible evidence for tsunami origin of some turbidity currents

    NASA Astrophysics Data System (ADS)

    Ballance, Peter F.; Gregory, Murray R.; Gibson, Graham W.

    1981-12-01

    Fossil coconuts are recorded in proximal turbidites of middle Miocene age in eastern North Island, New Zealand. This is apparently the first record of coconuts in turbidites. The rocks can be assigned to a mid-submarine-fan environment and are part of the accretionary prism of the late Cenozoic volcanic arc in northern New Zealand. The climate was marginally tropical. These turbidites may have been formed by the surge of sediment and debris carried offshore by tsunamis.

  20. Clay mineralogy indicates a mildly warm and humid living environment for the Miocene hominoid from the Zhaotong Basin, Yunnan, China

    NASA Astrophysics Data System (ADS)

    Zhang, Chunxia; Guo, Zhengtang; Deng, Chenglong; Ji, Xueping; Wu, Haibin; Paterson, Greig A.; Chang, Lin; Li, Qin; Wu, Bailing; Zhu, Rixiang

    2016-02-01

    Global and regional environmental changes have influenced the evolutionary processes of hominoid primates, particularly during the Miocene. Recently, a new Lufengpithecus cf. lufengensis hominoid fossil with a late Miocene age of ~6.2 Ma was discovered in the Shuitangba (STB) section of the Zhaotong Basin in Yunnan on the southeast margin of the Tibetan Plateau. To understand the relationship between paleoclimate and hominoid evolution, we have studied sedimentary, clay mineralogy and geochemical proxies for the late Miocene STB section (~16 m thick; ca. 6.7–6.0 Ma). Our results show that Lufengpithecus cf. lufengensis lived in a mildly warm and humid climate in a lacustrine or swamp environment. Comparing mid to late Miocene records from hominoid sites in Yunnan, Siwalik in Pakistan, and tropical Africa we find that ecological shifts from forest to grassland in Siwalik are much later than in tropical Africa, consistent with the disappearance of hominoid fossils. However, no significant vegetation changes are found in Yunnan during the late Miocene, which we suggest is the result of uplift of the Tibetan plateau combined with the Asian monsoon geographically and climatically isolating these regions. The resultant warm and humid conditions in southeastern China offered an important refuge for Miocene hominoids.

  1. Clay mineralogy indicates a mildly warm and humid living environment for the Miocene hominoid from the Zhaotong Basin, Yunnan, China.

    PubMed

    Zhang, Chunxia; Guo, Zhengtang; Deng, Chenglong; Ji, Xueping; Wu, Haibin; Paterson, Greig A; Chang, Lin; Li, Qin; Wu, Bailing; Zhu, Rixiang

    2016-01-01

    Global and regional environmental changes have influenced the evolutionary processes of hominoid primates, particularly during the Miocene. Recently, a new Lufengpithecus cf. lufengensis hominoid fossil with a late Miocene age of ~6.2 Ma was discovered in the Shuitangba (STB) section of the Zhaotong Basin in Yunnan on the southeast margin of the Tibetan Plateau. To understand the relationship between paleoclimate and hominoid evolution, we have studied sedimentary, clay mineralogy and geochemical proxies for the late Miocene STB section (~16 m thick; ca. 6.7-6.0 Ma). Our results show that Lufengpithecus cf. lufengensis lived in a mildly warm and humid climate in a lacustrine or swamp environment. Comparing mid to late Miocene records from hominoid sites in Yunnan, Siwalik in Pakistan, and tropical Africa we find that ecological shifts from forest to grassland in Siwalik are much later than in tropical Africa, consistent with the disappearance of hominoid fossils. However, no significant vegetation changes are found in Yunnan during the late Miocene, which we suggest is the result of uplift of the Tibetan plateau combined with the Asian monsoon geographically and climatically isolating these regions. The resultant warm and humid conditions in southeastern China offered an important refuge for Miocene hominoids. PMID:26829756

  2. Clay mineralogy indicates a mildly warm and humid living environment for the Miocene hominoid from the Zhaotong Basin, Yunnan, China

    PubMed Central

    Zhang, Chunxia; Guo, Zhengtang; Deng, Chenglong; Ji, Xueping; Wu, Haibin; Paterson, Greig A.; Chang, Lin; Li, Qin; Wu, Bailing; Zhu, Rixiang

    2016-01-01

    Global and regional environmental changes have influenced the evolutionary processes of hominoid primates, particularly during the Miocene. Recently, a new Lufengpithecus cf. lufengensis hominoid fossil with a late Miocene age of ~6.2 Ma was discovered in the Shuitangba (STB) section of the Zhaotong Basin in Yunnan on the southeast margin of the Tibetan Plateau. To understand the relationship between paleoclimate and hominoid evolution, we have studied sedimentary, clay mineralogy and geochemical proxies for the late Miocene STB section (~16 m thick; ca. 6.7–6.0 Ma). Our results show that Lufengpithecus cf. lufengensis lived in a mildly warm and humid climate in a lacustrine or swamp environment. Comparing mid to late Miocene records from hominoid sites in Yunnan, Siwalik in Pakistan, and tropical Africa we find that ecological shifts from forest to grassland in Siwalik are much later than in tropical Africa, consistent with the disappearance of hominoid fossils. However, no significant vegetation changes are found in Yunnan during the late Miocene, which we suggest is the result of uplift of the Tibetan plateau combined with the Asian monsoon geographically and climatically isolating these regions. The resultant warm and humid conditions in southeastern China offered an important refuge for Miocene hominoids. PMID:26829756

  3. Equatorial Precession Drove Mid-Latitude Changes in ENSO-Scale Variation in the Earliest Miocene

    NASA Astrophysics Data System (ADS)

    Fox, B.; D'Andrea, W. J.; Lee, D. E.; Wilson, G. S.

    2014-12-01

    Foulden Maar is an annually laminated lacustrine diatomite deposit from the South Island of New Zealand. The deposit was laid down over ~100 kyr of the latest Oligocene and earliest Miocene, during the peak and deglaciation phase of the Mi-1 Antarctic glaciation event. At this time, New Zealand was located at approximately the same latitude as today (~45°S). Evidence from organic geochemical proxies (δD, δ13C) and physical properties (density, colour) indicates the presence of an 11-kyr cycle at the site. Although it is known that 11-kyr insolation (half-precession) cycles occur between the Tropics, this cycle is rarely seen in sedimentary archives deposited outside the immediate vicinity of the Equator. Records from Foulden Maar correlate well with the amplitude and phase of the modelled equatorial half-precession cycle for the earliest Miocene. High-resolution (50 µm) colour intensity measurements and lamina thickness measurements both indicate the presence of significant ENSO-like (2-8 year) variation in the Foulden Maar sediments. Early results from targeted lamina thickness measurements suggest that ENSO-band variation is modulated by the 11-kyr cycle, with power in the ENSO band increasing during periods of increased insolation at the Equator. This implies that equatorial half-precession had a significant effect on ENSO-like variation in the early Miocene, and that this effect was felt as far afield as the mid-latitudes of the Southern Hemisphere.

  4. Terpenoid Compositions and Botanical Origins of Late Cretaceous and Miocene Amber from China

    PubMed Central

    Shi, Gongle; Dutta, Suryendu; Paul, Swagata; Wang, Bo; Jacques, Frédéric M. B.

    2014-01-01

    The terpenoid compositions of the Late Cretaceous Xixia amber from Central China and the middle Miocene Zhangpu amber from Southeast China were analyzed by gas chromatography-mass spectrometry (GC-MS) to elucidate their botanical origins. The Xixia amber is characterized by sesquiterpenoids, abietane and phyllocladane type diterpenoids, but lacks phenolic abietanes and labdane derivatives. The molecular compositions indicate that the Xixia amber is most likely contributed by the conifer family Araucariaceae, which is today distributed primarily in the Southern Hemisphere, but widely occurred in the Northern Hemisphere during the Mesozoic according to paleobotanical evidence. The middle Miocene Zhangpu amber is characterized by amyrin and amyrone-based triterpenoids and cadalene-based sesquiterpenoids. It is considered derived from the tropical angiosperm family Dipterocarpaceae based on these compounds and the co-occurring fossil winged fruits of the family in Zhangpu. This provides new evidence for the occurrence of a dipterocarp forest in the middle Miocene of Southeast China. It is the first detailed biomarker study for amber from East Asia. PMID:25354364

  5. Molluscan fauna from the Miocene sediments of Kachchh, Gujarat, India Part 3. Gastropods

    NASA Astrophysics Data System (ADS)

    Kulkarni, Kantimati G.; Kapoor, Satarupa Bhattacharjee; Borkar, Vidyadhar D.

    2010-06-01

    Systematic description of 25 gastropod species from the Khari Nadi Formation (Aquitanian) and Chhasra Formation (Burdigalian) from the Kachchh District, Gujarat, India is given. A checklist of 116 forms including those reported by earlier researchers, emending taxonomic identifications wherever necessary, is also provided. Vredenburg had referred these two formations together as the Gaj Beds of Kachchh. He noticed the affinity of molluscs among the Miocene deposits of Kachchh and Kathiawar regions of Gujarat, and Sind province of Pakistan. He also observed that molluscs from his Lower Gaj and Upper Gaj Formations showed relationship respectively with the Rembang (Aquitanian) and Njalindung (Burdigalian) series of the East Indies. Aquitanian and Burdigalian ages assigned by him were later substantiated by Raju on the basis of foraminifera. Present studies corroborated that the molluscan assemblage from the Miocene rocks of Kachchh is closely related to that from the Gaj Beds of Sind and the Ashapura Clay Member of Kathiawar; besides revealing that the fauna from these three formations taken together is essentially endemic. Discovery of certain species from the Quilon Beds in the Miocene of Kachchh evinces a close affinity between these two formations. The present fauna includes five extant forms, while 29 forms have related species in the Recent fauna.

  6. Badenian (Middle Miocene) echinoids and starfish from western Ukraine, and their biogeographic and stratigraphic significance

    NASA Astrophysics Data System (ADS)

    Radwa?ski, Andrzej; Grka, Marcin; Wysocka, Anna

    2014-06-01

    Echinoderms from the Badenian (Middle Miocene) of the Fore-Carpathian Basin of western Ukraine are facies restricted. The Mykolaiv Beds, stratigraphically older, yielded the starfish Astropecten forbesi (complete skeletons), two genera of sand dollars (Parascutella, Parmulechinus), and numerous other echinoids of the genera Psammechinus , Echinocyamus, Spatangus, Hemipatagus, Echinocardium, Clypeaster, Echinolampas, and Conolampas. The stratigraphically younger, calcareous Ternopil Beds yielded Eucidaris (complete coronae, isolated spines), Arbacina , Brissus, and Rhabdobrissus. Sixteen species of echinoids are distinguished and/or commented. A new brissid, Rhabdobrissus tarnopolensis sp. nov., is established. A mass occurrence of some species (Psammechinus dubius and Hemipatagus ocellatus) contrasts with that of mass aggregations (sand dollars and Echinocardium leopolitanum) by dynamic events in selected layers of proximal tempestites. Of special note is the occurrence of very small specimens, interpreted as juveniles (`babies') having been swept out of their restricted biotopes (`nurseries'). Some species hitherto regarded as of Early Miocene age, and the problem of their persistence beyond the Fore-Carpathian Basin and/or migration into that basin during the Middle Miocene transgression are discussed.

  7. Reconstruction of Middle to Late Miocene Events in the Mediterranean Area: Benthic Foraminiferal Evidence

    NASA Astrophysics Data System (ADS)

    Kouwenhoven, T. J.; Krijgsman, W.; van der Zwaan, B. J.; van der Zwaan, B. J.

    2001-12-01

    During the middle and late Miocene the Mediterranean area was subject to changing interactions with major ocean basins, as well as to regional geographic changes. An anti-estuarine circulation probably developed in the proto-Mediterranean at some time after disruption of the connection to the Indo-Pacific. Subsequently, the Mediterranean evolved into a concentration basin. Development of the Italian landmass and the central Mediterranean sill were instrumental in shaping the eastern and western basins. During the late Miocene the Betic and Rifian Corridors were the main connections between the Atlantic and the Mediterranean. During the latest Miocene the restriction of the basin from surrounding major ocean basins led to the deposition of massive evaporates: the Messinian salinity crisis. Our research indicates that constriction of the eastern part of the Rifian Corridor around 7.16 Ma affected the circulation patterns in the Mediterranean basin: the oxygenation of deeper Mediterranean waters diminished dramatically. Although local and regional events are not always easy to separate, the event at 7.16 Ma can be recognized basin-wide. Data suggest that shortly afterwards the bottom water salinity started to increase in the deeper parts of the basin. The 7.16 Ma event is followed by a chain of events, likely triggered by repeated regional sea-level drops. A tentative reconstruction of circulation patterns suggests that these sea-level oscillations were possibly astronomically forced and essential in the stepwise concentration of the deep brine eventually resulting in evaporitization.

  8. First Occurrence of Platycladus from the Upper Miocene of Southwest China and Its Phytogeographic Implications

    PubMed Central

    Li, Qi-Jia; Zhao, Zhen-Rui; Sun, Bai-Nian

    2014-01-01

    Platycladus Spach is native to Central China, but its natural occurrences are very difficult to establish. According to molecular phylogenetic data, this genus might have originated since the Oligocene, but no fossil record has been reported. Here, we describe eight foliage branches from the upper Miocene in western Yunnan, Southwest China as a new species, P. yunnanensis sp. nov., which is characterized by foliage branches spread in flattened sprays, and leaves decussate, imbricate, scale-like and dimorphic. The leaves are amphistomatic, and the stomata are elliptical or oblong, haplocheilic, and monocyclic type. Based on a detailed comparison with the extant genera of Cupressaceae sensu lato, our fossils are classified into the genus Platycladus. The occurrence of P. yunnanensis sp. nov. indicates that this genus had a more southernly natural distribution in the late Miocene than at present. Molecular phylogeny and fossil records support a pre-Oligocene common ancestor for the genera Platycladus, Microbiota and Calocedrus. The separation of the three taxa was most likely caused by the arid belt across Central China during the Oligocene. In addition, the cooling down of the global temperature and the strengthening of Asian monsoon since the Miocene will further promote the migration of these genera. PMID:25517767

  9. Fossil wood from the Miocene and Oligocene epoch: chemistry and morphology.

    PubMed

    Bardet, Michel; Pournou, Anastasia

    2015-01-01

    Fossil wood is the naturally preserved remain of the secondary xylem of plants that lived before the Holocene epoch. Typically, fossil wood is preserved as coalified or petrified and rarely as mummified tissue. The process of fossilization is very complex and it is still unknown why in the same fossil record, wood can be found in different fossilisation forms. In 2007, a fossil forest was found in the Bükkábrány open-pit coal mine in Hungary. The non-petrified forest is estimated to be 7 million years old (Miocene epoch) and its trees were found standing in an upright position. This fossil assemblage is exceptionally rare because wood has been preserved as soft waterlogged tissue. This study aimed to investigate this remarkable way of fossil wood preservation, by examining its chemistry with (13)C CPMAS NMR and its morphology with light and electron microscopy. For comparison reasons, a petrified wood trunk from the Oligocene epoch (30 Myr) found in 2001 at Porrentruy region in Switzerland and two fresh wood samples of the modern equivalents of the Miocene sample were also examined. The results obtained showed that the outstanding preservation state of the Miocene fossil is not owed to petrification or coalification. Mummification is a potential mechanism that could explain Bükkábrány trunks' condition, however this fossilisation process is not well studied and therefore this hypothesis needs to be further investigated. PMID:25294390

  10. Seastacks buried beneath newly reported Lower Miocene sandstone, northern Santa Barbara County, California

    SciTech Connect

    Fritsche, A.E.; Hanna, F.M.

    1985-04-01

    Three large, isolated exposures of a light-gray, coarse-grained, thick-bedded sandstone unit occur in the northern San Rafael Mountains of Santa Barbara County, California. These rocks are moderately fossiliferous and contain Vertipecten bowersi, Amussiopecten vanvlecki, Aequipecten andersoni, Otrea howelli, shark teeth, whale bones, and regular echinoid spines. The fossils indicate that the sandstone unit, although previously reported as upper(.) Miocene, correlates best with the lower Miocene Vaqueros Formation. This unit was deposited in angular unconformity on a Cretaceous, greenish-gray turbidite sequence of interbedded sandstone and shale, and onlaps the unconformity erosion surface from west to east, the unit being thicker in the west and older at its base. The underlying Cretaceous sandstone beds are well indurated, and during the eastward transgression of the early Miocene sea, they resisted wave erosion and stood as seastacks offshore of the advancing coastline, thus creating a very irregular topographic surface upon which the Vaqueros Formation was deposited. Some seastacks were as much as 4 m tall, as indicated by inliers of Cretaceous rock surrounded by 4-m thick sections of the Vaqueros Formation.

  11. Middle Miocene environmental and climatic evolution at the Wilkes Land margin, East Antarctica

    NASA Astrophysics Data System (ADS)

    Sangiorgi, F.; Passchier, S.; Salzmann, U.; Schouten, S.; Pross, J.; Bijl, P.; Tauxe, L.; Bendle, J. A.; Escutia, C.; Brinkhuis, H.

    2012-12-01

    Integrated Ocean Drilling Program (IODP) Expedition 318 successfully drilled a Middle Miocene (~ 17 - 12.5 Ma) record from the Wilkes Land Margin at Site U1356A (6318.6138'S, 13559.9376'E), located at the transition between the continental rise and the abyssal plain at 4003 mbsl. We present a multiproxy palynological (dinoflagellate cyst, pollen and spores), sedimentological and organic geochemical (TEX86, MBT/CBT) study, which unravels the environmental and climate variability across the Miocene Climatic Optimum (MCO, ~17-15 Ma) and the Mid Miocene Climate Transition (MMCT). Several independent lines of evidence indeed suggest a relatively warm climate during the MCO. Dinocyst and pollen assemblage diversity at the MCO is unprecedented for a Neogene Antarctic record and indicates a temperate, sea ice-free marine environment, with woody sub-antarctic vegetation with elements of forest/shrub tundra and peat lands along the coast. These results are further confirmed by relatively warm TEX86-derived Sea Surface Temperatures and mild MBT-derived continental temperatures, and by the absence of glacially derived deposits and very few ice-rafted clasts. A generally colder but highly dynamic environment is suggested for the interval 15-12.5 Ma.

  12. Palynostratigraphy, palaeoclimates and palaeodepositional environments of the Miocene aged Agbada Formation in the Niger Delta, Nigeria

    NASA Astrophysics Data System (ADS)

    Bankole, Samson I.; Schrank, Eckart; Osterloff, Peter L.

    2014-07-01

    A diverse assemblage of palynomorphs dominated by terrestrially derived pollen and spores is reported from three wells penetrating the Miocene Agbada Formation. The pteridophyte and bryophyte spores which form the background assemblages in the three wells are good indicators of humid tropical climates which might have prevailed in the Niger Delta during the Miocene. The abundance and variations of climate-sensitive taxa including mangrove affiliated pollen and spore types Acrostichumsporites, Psilatricolporites crassus, Zonocostites ramonae and Graminidites annulatus representing the savannah vegetation cover indicate a complex interplay between periods of wetter and drier climates. Marine-derived dinoflagellate cysts and foraminiferal test linings are significantly present in the three wells. Taxa indicating freshwater contributions including Botryococcus spp., Chomotriletes minor, Ovoidites parvus and Pediastrum spp. are also represented numerically across the three wells. The presence of age diagnostic palynomorphs such as Crassoretitriletes vanraadshooveni, Retibrevitricolporites obodoensis, Tuberculodinium vancampoae, Zonocostites ramonae and Tuberculodinium vancampoae recovered in the three sections studied suggest a Miocene age for the investigated Agbada Formation. The proposed age is supported by the ranges of key palynomorphs in contemporaneous basins in Africa, northern South America and other parts of the World.

  13. Fire and fire-adapted vegetation promoted C4 expansion in the late Miocene.

    PubMed

    Scheiter, Simon; Higgins, Steven I; Osborne, Colin P; Bradshaw, Catherine; Lunt, Dan; Ripley, Brad S; Taylor, Lyla L; Beerling, David J

    2012-08-01

    Large proportions of the Earth's land surface are covered by biomes dominated by C(4) grasses. These C(4)-dominated biomes originated during the late Miocene, 3-8 million years ago (Ma), but there is evidence that C(4) grasses evolved some 20 Ma earlier during the early Miocene/Oligocene. Explanations for this lag between evolution and expansion invoke changes in atmospheric CO(2), seasonality of climate and fire. However, there is still no consensus about which of these factors triggered C(4) grassland expansion. We use a vegetation model, the adaptive dynamic global vegetation model (aDGVM), to test how CO(2), temperature, precipitation, fire and the tolerance of vegetation to fire influence C(4) grassland expansion. Simulations are forced with late Miocene climates generated with the Hadley Centre coupled ocean-atmosphere-vegetation general circulation model. We show that physiological differences between the C(3) and C(4) photosynthetic pathways cannot explain C(4) grass invasion into forests, but that fire is a crucial driver. Fire-promoting plant traits serve to expand the climate space in which C(4)-dominated biomes can persist. We propose that three mechanisms were involved in C(4) expansion: the physiological advantage of C(4) grasses under low atmospheric CO(2) allowed them to invade C(3) grasslands; fire allowed grasses to invade forests; and the evolution of fire-resistant savanna trees expanded the climate space that savannas can invade. PMID:22712748

  14. Late Miocene sedimentary environments in south-western Amazonia (Solimes Formation; Brazil)

    NASA Astrophysics Data System (ADS)

    Gross, Martin; Piller, Werner E.; Ramos, Maria Ines; Douglas da Silva Paz, Jackson

    2011-08-01

    In Miocene times a vast wetland existed in Western Amazonia. Whereas the general development of this amazing ecosystem is well established, many questions remain open on sedimentary environments, stratigraphical correlations as well as its palaeogeographical configuration. Several outcrops located in a barely studied region around Eirunep (SW Amazonas state, Brazil) were investigated to obtain basic sedimentological data. The observed deposits belong to the upper part of the Solimes Formation and are biostratigraphically dated to the Late Miocene. Vertically as well as laterally highly variable fine-grained clastic successions were recorded. Based on the lithofacies assemblages, these sediments represent fluvial deposits, possibly of an anastomosing river system. Sand bodies formed within active channels and dominant overbank fines are described (levees, crevasse splays/channels/deltas, abandoned channels, backswamps, floodplain paleosols). Lacustrine environments are restricted to local floodplain ponds/lakes. The mollusc and ostracod content as well as very light ?18O and ?13C values, measured on ostracod valves, refer to exclusively freshwater conditions. Based on palaeontological and geological results the existence of a long-lived lake (Lake Pebas) or any influx of marine waters can be excluded for that region during the Late Miocene.

  15. New magnetochronology of Late Miocene mammal fauna, NE Tibetan Plateau, China: Mammal migration and paleoenvironments

    NASA Astrophysics Data System (ADS)

    Ao, Hong; Zhang, Peng; Dekkers, Mark J.; Roberts, Andrew P.; An, Zhisheng; Li, Yongxiang; Lu, Fengyan; Lin, Shan; Li, Xingwen

    2016-01-01

    Lanzhou Basin lies on the northeastern margin of the Tibetan Plateau in western China and is a rich source of Oligocene-Miocene mammalian fossils. Obtaining precise age determinations for these fossils is important to address key questions concerning mammalian and environmental evolution in Asia associated with stepwise Tibetan Plateau uplift. Here we report a new magnetostratigraphic record for the Xingjiawan fluvio-lacustrine section from the northwestern margin of Lanzhou Basin that can be correlated to the geomagnetic polarity timescale with two options. The Late Miocene Xingjiawan Fauna is located either at the boundary between reversed polarity chron C4r.1r and normal polarity chron C4n.2n or at the boundary between subchrons C5r.1r and C5n.2n, with an estimated age of at least ∼8 Ma or perhaps as early as ∼11 Ma. Both age estimations imply that the fossil Stegodon in the Lanzhou Basin is the oldest known record of Stegodon worldwide; it predates the formerly oldest Stegodon find from Africa by at least one million years and perhaps by as many as four million years. This provides new evidence for an Asian origin of Stegodon. Together with other faunal components, a mixed woodland/grassland setting existed in the Lanzhou Basin during the Late Miocene, in contrast to its modern arid environment.

  16. Miocene honey bees from the Randeck Maar of southwestern Germany (Hymenoptera, Apidae)

    PubMed Central

    Kotthoff, Ulrich; Wappler, Torsten; Engel, Michael S.

    2011-01-01

    Abstract The Miocene Randeck Maar (southwestern Germany) is one of the only sites with abundant material of fossil honey bees. The fauna has been the focus of much scrutiny by early authors who recognized multiple species or subspecies within the fauna. The history of work on the Randeck Maar is briefly reviewed and these fossils placed into context with other Tertiary and living species of the genus Apis Linnaeus (Apinae: Apini). Previously unrecorded specimens from Randeck Maar were compared with earlier series in an attempt to evaluate the observed variation. A morphometric analysis of forewing venation angles across representative Recent and Tertiary species of Apis as well as various non-Apini controls was undertaken to evaluate the distribution of variation in fossil honey bees. The resulting dendrogram shows considerable variation concerning the wing venation of Miocene Apini, but intergradation of other morphological characters reveals no clear pattern of separate species. This suggests that a single, highly variable species was present in Europe during the Miocene. The pattern also supports the notion that the multiple species and subspecies proposed by earlier authors for the Randeck Maar honey bee fauna are not valid, and all are accordingly recognized as Apis armbrusteri Zeuner. PMID:21594072

  17. Late Miocene sedimentary environments in south-western Amazonia (Solimes Formation; Brazil)

    PubMed Central

    Gross, Martin; Piller, Werner E.; Ramos, Maria Ines; Douglas da Silva Paz, Jackson

    2011-01-01

    In Miocene times a vast wetland existed in Western Amazonia. Whereas the general development of this amazing ecosystem is well established, many questions remain open on sedimentary environments, stratigraphical correlations as well as its palaeogeographical configuration. Several outcrops located in a barely studied region around Eirunep (SW Amazonas state, Brazil) were investigated to obtain basic sedimentological data. The observed deposits belong to the upper part of the Solimes Formation and are biostratigraphically dated to the Late Miocene. Vertically as well as laterally highly variable fine-grained clastic successions were recorded. Based on the lithofacies assemblages, these sediments represent fluvial deposits, possibly of an anastomosing river system. Sand bodies formed within active channels and dominant overbank fines are described (levees, crevasse splays/channels/deltas, abandoned channels, backswamps, floodplain paleosols). Lacustrine environments are restricted to local floodplain ponds/lakes. The mollusc and ostracod content as well as very light ?18O and ?13C values, measured on ostracod valves, refer to exclusively freshwater conditions. Based on palaeontological and geological results the existence of a long-lived lake (Lake Pebas) or any influx of marine waters can be excluded for that region during the Late Miocene. PMID:26523089

  18. Marine transgression and regression in Miocene sequences of northern Pegu (Bago) Yoma, Central Myanmar

    NASA Astrophysics Data System (ADS)

    Khin, Kyi; Myitta

    1999-06-01

    Neogene strata of the northern part of the Pegu (Bago) Yoma Range, Central Myanmar, contain a series of shallow marine clastic sediments with stratigraphic ages ranging from the Early to Late Miocene. The studied succession (around 750 m thick) is composed of three major stratigraphic units deposited during a major regression and four major transgressive cycles in the Early to Late Miocene. The transgressive deposits consist of elongate sand-bars and broad sand-sheets that pass headward into mixed-flats of tidal environments. Marine flooding in transgressive deposits is associated with coquina beds and allochthonous coral-bearing sandy limestone bands. Major marine regressions are associated with lowstand progradation of thick estuary point-bars passing up into upper sand-flat sand bodies encased within the tidal flat sequences and lower shoreface deposits with local unconformities. The succession initially formed in a large scale incised-valley system, and was later interrupted by two major marine transgressions in the generally regressive or basinward-stepping stratigraphic sequences. Successive sandbodies were formed during a sea-level lowstand and early stage of the subsequent relative rise of sea level in a tide-dominated estuary system in the eastern part of the Central Myanmar Tertiary Basin during Early to Late Miocene times.

  19. Middle Miocene environmental and climatic evolution at the Wilkes Land margin, East Antarctica

    NASA Astrophysics Data System (ADS)

    Sangiorgi, Francesca; Bijl, Peter; Passchier, Sandra; Salzmann, Ulrich; Schouten, Stefan; Pross, Jörg; Escutia, Carlota; Brinkhuis, Henk

    2015-04-01

    Integrated Ocean Drilling Program (IODP) Expedition 318 successfully drilled a Middle Miocene (~ 17 - 12.5 Ma) record from the Wilkes Land Margin at Site U1356A (63°18.6138'S, 135°59.9376'E), located at the transition between the continental rise and the abyssal plain at 4003 mbsl. We present a multiproxy palynological (dinoflagellate cyst, pollen and spores), sedimentological and organic geochemical (TEX86, MBT/CBT) study, which unravels the environmental and climate variability across the Miocene Climatic Optimum (MCO, ~17-15 Ma) and the Mid Miocene Climate Transition (MMCT). Several independent lines of evidence suggest a relatively warm climate during the MCO. Dinocyst and pollen assemblage diversity at the MCO is unprecedented for a Neogene Antarctic record and indicates a temperate, sea ice-free marine environment, with woody sub-antarctic vegetation with elements of forest/shrub tundra and peat lands along the coast. These results are further confirmed by relatively warm TEX86-derived Sea Surface Temperatures and mild MBT-derived continental temperatures, and by the absence of glacially derived deposits and very few ice-rafted clasts. A generally colder but highly dynamic environment is suggested for the interval 15-12.5 Ma.

  20. Regional implications of geochemistry and style of emplacement of Miocene I-type diorite and granite, Delos, Cyclades, Greece

    NASA Astrophysics Data System (ADS)

    Pe-Piper, Georgia; Piper, David J. W.; Matarangas, Dionysis

    2002-01-01

    The Miocene plutons of the Cyclades were emplaced in a subduction setting during regional back-arc extension of continental crust, that led to flat-lying mid-crustal detachment faulting. Mapping of the island of Delos shows that quartz diorite and tonalite were emplaced as dykes in country rock of schist and marble within shear zones parallel to the extension direction. Mafic magmas were followed by numerous small batches of felsic magma, with magmatic and ductile deformation synchronous with magma emplacement. Late granite dykes occupy brittle fractures in the more deformed rocks. Mafic and intermediate rocks show a bimodal distribution of incompatible trace elements, with one group of broadly tholeiitic character and the other with substantial enrichment in Sr, Nb, and HFSE, but low Th and Ba. These differences appear to be inherited from two distinct mafic sources that are different from the mafic source for the plutons of the eastern Cyclades. Voluminous granodiorite results from these mafic magmas fractionating and/or mixing with felsic crustal material, some of which was derived by anatexis of a sedimentary protolith, indicated by high B and Mn. Some late granites appear derived from partial melting of Hercynian paragneiss. Regionally, the shear zones appear to be feeders to more extensive granitic plutons located at space produced at ramps in detachment fault zones. The shear zones parallel the Mid-Cycladic Lineament, a broad zone of displacement between two crustal blocks rotating in opposing directions as rollback took place at the Hellenic subduction zone. Distinctive geochemical features in Miocene igneous rocks suggests that these two blocks had quite different geological histories. The localisation of plutonism and core complexes near the Mid Cycladic Lineament suggests that this crustal-scale shear played a role in bringing subduction-derived magmas to mid-crustal levels. The heat supplied by the mafic magmas promoted ductile deformation high in the crust, where extension was concentrated, leading to the formation of core complexes. The regional extension resulted in progressive shallowing of the position of the granite solidus within the crust, leading to welding of the Mid-Cycladic Lineament, which is no longer seismically active.

  1. Thermochronologic constraints on the Miocene slip history of the South Tibetan detachment system in the Everest region, central Himalaya

    NASA Astrophysics Data System (ADS)

    Schultz, M.; Hodges, K. V.; Van Soest, M. C.; Wartho, J. A.

    2014-12-01

    North-dipping, low-angle normal faults of the South Tibetan detachment system (STDS) can be traced for a distance of more than 2000 km along strike and represent an important tectonic characteristic of the Miocene Himalayan-Tibetan orogenic system. Nowhere is the STDS better exposed than the N-S-trending Rongbuk Valley in southern Tibet, where it can be traced down dip from the summit of Everest for a distance of over 30 km before disappearing beneath the valley floor. This places a minimum constraint on Miocene displacement on the feature in this area, but some research groups have suggested ~200 km of displacement based on the difference in metamorphic pressures across the STDS and the very low (< 15?) primary dip of the structure. We are exploring this issue further using developing (U-Th)/He and 40Ar/39Ar datasets from deformed footwall sillimanite gneisses and leucogranites. Data obtained thus far indicate relatively rapid cooling of the footwall after the intrusion of deformed leucogranites at ca. 16.7 Ma to muscovite 40Ar/39Ar closure temperatures (ca. 15.5-14.2 Ma) and zircon (U-Th)/He closure temperatures (ca. 14.5-11 Ma). We attribute this cooling to tectonic denudation related to ca. 16 Ma STDS slip. Although the (U-Th)/He systematics of apatites from these rocks is complex, our current interpretation of available data places cooling through the ca. 75?C closure isotherm at ca. 8-9 Ma, which would suggest a significant reduction in cooling rate that is observed in our inverse model runs of the 1D program, HeFTy. Ongoing analyses of footwall samples from ~8 km to the north of our Rongbuk sample localities in the Ra Chu river valley will greatly strengthen our datasets. With the Ra Chu analyses, our datasets will constrain the cooling history of the footwall for more than 20 km perpendicular to the strike of the detachment. Our presentation will also incorporate results from the program Pecube that will contribute to our calculation of the slip rate by specifying the appropriate exhumation rate.

  2. Dated molecular phylogenies indicate a Miocene origin for Arabidopsis thaliana.

    PubMed

    Beilstein, Mark A; Nagalingum, Nathalie S; Clements, Mark D; Manchester, Steven R; Mathews, Sarah

    2010-10-26

    Dated molecular phylogenies are the basis for understanding species diversity and for linking changes in rates of diversification with historical events such as restructuring in developmental pathways, genome doubling, or dispersal onto a new continent. Valid fossil calibration points are essential to the accurate estimation of divergence dates, but for many groups of flowering plants fossil evidence is unavailable or limited. Arabidopsis thaliana, the primary genetic model in plant biology and the first plant to have its entire genome sequenced, belongs to one such group, the plant family Brassicaceae. Thus, the timing of A. thaliana evolution and the history of its genome have been controversial. We bring previously overlooked fossil evidence to bear on these questions and find the split between A. thaliana and Arabidopsis lyrata occurred about 13 Mya, and that the split between Arabidopsis and the Brassica complex (broccoli, cabbage, canola) occurred about 43 Mya. These estimates, which are two- to threefold older than previous estimates, indicate that gene, genomic, and developmental evolution occurred much more slowly than previously hypothesized and that Arabidopsis evolved during a period of warming rather than of cooling. We detected a 2- to 10-fold shift in species diversification rates on the branch uniting Brassicaceae with its sister families. The timing of this shift suggests a possible impact of the Cretaceous-Paleogene mass extinction on their radiation and that Brassicales codiversified with pierid butterflies that specialize on mustard-oil-producing plants. PMID:20921408

  3. From Problem Taxa to Problem Solver: A New Miocene Family, Tranatocetidae, Brings Perspective on Baleen Whale Evolution.

    PubMed

    Gol'din, Pavel; Steeman, Mette Elstrup

    2015-01-01

    Miocene baleen whales were highly diverse and included tens of genera. However, their taxonomy and phylogeny, as well as relationships with living whales, are still a subject of controversy. Here, "Mesocetus" argillarius, a poorly known specimen from Denmark, is redescribed with a focus on the cranial anatomy. It was found to represent not only a new genus, Tranatocetus gen. nov., but also a new family; Tranatocetidae. The whales of this family have the rostral bones either overriding or dividing the frontals; the rostral bones are contacting the parietals and nasals dividing the maxillae on the vertex; the occipital shield is dorsoventrally bent. The tympanic bulla is particularly characteristic of this family featuring a short, narrow anterior portion with a rounded or squared anterior end and a wider and higher posterior portion that is swollen in the posteroventral area. A phylogenetic analysis including 51 taxa supports a monophyletic group comprising most Neogene and modern whales, with Tranatocetidae being possibly closer related to Balaenopteridae (rorquals) than to Cetotheriidae. Tranatocetidae exhibit a charahteristic bulla shape. In fact, all Neogene and modern mysticete families examined have a unique shape of the tympanic bulla that is diagnostic at family-level. Inclusion of problematic taxa like Tranatocetus argillarius in phylogenies brings new understanding of the distribution and diagnostic value of character traits. This underlines the need for re-examination of earlier described specimens in the light of the wealth of new information published in later years. PMID:26331471

  4. Chewing through the Miocene: an examination of the feeding musculature in the ground sloth Hapalops from South America (Mammalia: Pilosa)

    PubMed Central

    Naples, Virginia L.; McAfee, Robert K.

    2014-01-01

    Hapalops, a smaller-sized and early sloth of the Megatheroidea, appeared in the middle Miocene Santa Cruz formation of Argentina. This genus is part of the group from which later, larger megatheroids arose, i.e., Nothrotheriops and Megatherium. Many cranial characters support this idea; however Hapalops is not merely a smaller antecedent of the later forms. Specifically, Hapalops retains short anterior caniniform teeth, and a temporomandibular joint elevated above the cheek tooth row; a combination distinct among sloths. An elevated temporomandibular joint occurs in Bradypus, a tree sloth with anterior chisel-shaped teeth instead of caniniforms, and the tree sloth Choloepus, which is aligned with the megalonychids, has anterior caniniforms. Hapalops has an elongated zygomatic ascending process that is reminiscent of that in Bradypus; however, the Bradypus skull is extremely foreshortened while that of Hapalops is elongated, as in nothrotheres, but not deepened as in megatheres. Previous work identified many sloth cranial character complexes, and functional limitations on skull feature combinations. The unique Hapalops character patterns indicate a selective feeder with a mediolaterally oriented grinding stroke during mastication. PMID:25075299

  5. A multi-gene dataset reveals a tropical New World origin and Early Miocene diversification of croakers (Perciformes: Sciaenidae).

    PubMed

    Lo, Pei-Chun; Liu, Shu-Hui; Chao, Ning Labbish; Nunoo, Francis K E; Mok, Hin-Kiu; Chen, Wei-Jen

    2015-07-01

    Widely distributed groups of living animals, such as the predominantly marine fish family Sciaenidae, have always attracted the attention of biogeographers to document the origins and patterns of diversification in time and space. In this study, the historical biogeography of the global Sciaenidae is reconstructed within a molecular phylogenetic framework to investigate their origin and to test the hypotheses explaining the present-day biogeographic patterns. Our data matrix comprises six mitochondrial and nuclear genes in 93 globally sampled sciaenid species from 52 genera. Within the inferred phylogenetic tree of the Sciaenidae, we identify 15 main and well-supported lineages; some of which have not been recognized previously. Reconstruction of habitat preferences shows repeated habitat transitions between marine and euryhaline environments. This implies that sciaenids can easily adapt to some variations in salinity, possibly as the consequence of their nearshore habitats and migratory life history. Conversely, complete marine/euryhaline to freshwater transitions occurred only three times, in South America, North America and South Asia. Ancestral range reconstruction analysis concomitant with fossil evidence indicates that sciaenids first originated and diversified in the tropical America during the Oligocene to Early Miocene before undergoing two range expansions, to Eastern Atlantic and to the Indo-West Pacific where a maximum species richness is observed. The uncommon biogeographic pattern identified is discussed in relation to current knowledge on origin of gradients of marine biodiversity toward the center of origin hypothesis in the Indo-West Pacific. PMID:25848970

  6. From Problem Taxa to Problem Solver: A New Miocene Family, Tranatocetidae, Brings Perspective on Baleen Whale Evolution

    PubMed Central

    Gol’din, Pavel; Steeman, Mette Elstrup

    2015-01-01

    Miocene baleen whales were highly diverse and included tens of genera. However, their taxonomy and phylogeny, as well as relationships with living whales, are still a subject of controversy. Here, “Mesocetus” argillarius, a poorly known specimen from Denmark, is redescribed with a focus on the cranial anatomy. It was found to represent not only a new genus, Tranatocetus gen. nov., but also a new family; Tranatocetidae. The whales of this family have the rostral bones either overriding or dividing the frontals; the rostral bones are contacting the parietals and nasals dividing the maxillae on the vertex; the occipital shield is dorsoventrally bent. The tympanic bulla is particularly characteristic of this family featuring a short, narrow anterior portion with a rounded or squared anterior end and a wider and higher posterior portion that is swollen in the posteroventral area. A phylogenetic analysis including 51 taxa supports a monophyletic group comprising most Neogene and modern whales, with Tranatocetidae being possibly closer related to Balaenopteridae (rorquals) than to Cetotheriidae. Tranatocetidae exhibit a charahteristic bulla shape. In fact, all Neogene and modern mysticete families examined have a unique shape of the tympanic bulla that is diagnostic at family-level. Inclusion of problematic taxa like Tranatocetus argillarius in phylogenies brings new understanding of the distribution and diagnostic value of character traits. This underlines the need for re-examination of earlier described specimens in the light of the wealth of new information published in later years. PMID:26331471

  7. Soft-sediment deformation structures in seismically affected deep-sea Miocene turbidites (Cilento Basin, southern Italy)

    NASA Astrophysics Data System (ADS)

    Valente, Alessio; ?l?czka, Andrzej; Cavuoto, Giuseppe

    2014-07-01

    Soft-sediment deformation structures (SSDS) are widespread in the upper part of the S. Mauro Formation (Cilento Group, Middle-Late Miocene). The succession is represented mainly by thick and very thick, massive, coarse-grained sandstones, deposited by rapid sedimentation of high-density turbidity currents. The most common SSDS are short pillars, dishes, sedimentary sills and convolutions. They occur mostly in the upper parts of sandstone beds. Vertical tubes of 4-5 cm in diameter and up to 50 cm long constitute the most striking structures. They begin in the middle part of sandstone beds, which are basically massive or contain faint dish structures. These tubes can bifurcate upwards and/ or pass into bedding-parallel veins or dikes. The vertical tubes sometimes form sand volcanoes on the then sedimentary surface. The SSDS are interpreted as the result of earthquake-triggered liquefaction and/or fluidisation of the turbidites that were affected by the seismic shocks. This implies that the deformed layers should be considered as seismites.

  8. Geological and Hydrodynamical Examination of the Bathyal Tsunamigenic Origin of Miocene Conglomerates in Chita Peninsula, Central Japan

    NASA Astrophysics Data System (ADS)

    Tachibana, Toru; Tsuji, Yoshinobu

    2011-06-01

    A conglomerate appears on a rocky coast called "Tsubutega-ura Coast", located on the southwestern coast near the southern tip of the Chita Peninsula, Aichi Prefecture, central Japan. The conglomerate belongs to Miocene sedimentary rocks termed the Morozaki Group. The conglomerate includes meter-scale boulders, indicating that it was formed by an extraordinary event. In the geological investigation, we observed that the conglomerate shows alternate changes of paleocurrent directions between seaward and landward. This feature is supposed to be formed by tsunami currents. In the hydrodynamical investigation, we obtained following results: (1) the lowest limit of a current velocity to move a boulder of about 3 m in diameter would be about 2-3 m/s, (2) the speed of tsunami currents reproduced by tsunami simulation exceeds 3 m/s at 300 m in depth when the tsunami is generated by a gigantic earthquake with magnitude 9.0 or more, (3) the transport distance of the boulder would be several hundred meters to several kilometers by one tsunami event caused by a gigantic earthquake. We conclude that tsunamis best explain the formation of the conglomerate deposited in upper bathyal environments about 200-400 m depth, both from geological and hydrodynamical viewpoints.

  9. Early evidence for complex social structure in Proboscidea from a late Miocene trackway site in the United Arab Emirates

    PubMed Central

    Bibi, Faysal; Kraatz, Brian; Craig, Nathan; Beech, Mark; Schuster, Mathieu; Hill, Andrew

    2012-01-01

    Many living vertebrates exhibit complex social structures, evidence for the antiquity of which is limited to rare and exceptional fossil finds. Living elephants possess a characteristic social structure that is sex-segregated and multi-tiered, centred around a matriarchal family and solitary or loosely associated groups of adult males. Although the fossil record of Proboscidea is extensive, the origin and evolution of social structure in this clade is virtually unknown. Here, we present imagery and analyses of an extensive late Miocene fossil trackway site from the United Arab Emirates. The site of Mleisa 1 preserves exceptionally long trackways of a herd of at least 13 individuals of varying size transected by that of a single large individual, indicating the presence of both herding and solitary social modes. Trackway stride lengths and resulting body mass estimates indicate that the solitary individual was also the largest and therefore most likely a male. Sexual determination for the herd is equivocal, but the body size profile and number of individuals are commensurate with those of a modern elephant family unit. The Mleisa 1 trackways provide direct evidence for the antiquity of characteristic and complex social structure in Proboscidea. PMID:22357934

  10. Palinspastic reconstruction of southeastern California and southwestern Arizona for the Middle Miocene

    NASA Astrophysics Data System (ADS)

    Richard, Stephen M.

    1993-08-01

    A paleogeographic reconstruction of southeastern California and southwestern Arizona at 10 Ma has been made based on available geologic and geophysical data. Clockwise rotation of 39 has been reconstructed in the eastern Transverse Ranges, consistent with paleomagnetic data from late Miocene volcanic rocks, and with slip estimates for left-lateral faults within the eastern Transverse Ranges and NW-trending right-lateral faults in the Mojave Desert. This domain of rotated rocks is bounded by the Pinto Mountain fault on the north. The model requires that the western part of the late Miocene Pinto Mountain fault was a thrust fault, which gained displacement to the west, because of the absence of evidence for rotation of the San Bernardino Mountains or for significant right slip faults within the San Bernardino Mountains. The Squaw Peak thrust system of Meisling and Weldon (1989) may be a western continuation of this fault system. The Sheep Hole fault bounds the rotating domain on the east. East of this fault an array of NW-trending right slip faults and south-trending extensional transfer zones has produced a basin and range physiography while accumulating up to 16 km of right slip. This maximum is significantly less than the 37.5 km of right slip required in this region by a recent reconstruction of the central Mojave Desert (Dokka and Travis, 1990a). Geologic relations along the southern boundary of the rotating domain are poorly known, but this boundary is interpreted to involve a series of curved strike slip faults and linking normal faults that accommodated noncoaxial extension. Quaternary movement on the Pinto Mountain and nearby faults is unrelated to the rotation of the eastern Transverse Ranges, and a hiatus during part of Pliocene time followed the deformation which produced the rotation. The reconstructed Clemens Well fault in the Orocopia Mountains, proposed as a major early Miocene strand of the San Andreas fault, projects eastward towards Arizona, where early Miocene rocks and structures are continuous across its trace, making large displacements on this structure unlikely. The model predicts a 14 clockwise rotation and 32% extension during late Miocene and early Pliocene time along a NW-trending line parallel to the present trace of the San Andreas fault. Palinspastic reconstructions of the San Andreas system based on this proposed reconstruction may be significantly modified from current models.

  11. Do Ecosystems Ever Converge? Evidence From Faunal Size Distributions Of Late Miocene North American Mammals

    NASA Astrophysics Data System (ADS)

    Lambert, W. David

    2005-03-01

    There is disagreement among geologists as to whether ecosystem system behavior in general is the net result of all of the complex internal system interactions (bottom-driven) or if the behavior is driven by a limited number of key processes (top-driven). If ecosystems are primarily bottom-driven in nature, then it is unlikely that any two complex ecosystems will ever behaviorally converge as a simple matter of probability, or that their behaviors will ever be predictable. Conversely, evidence of ecosystem convergence would suggest that the systems are top-driven, with the corollary that their behaviors can be understood (and therefore in principle predicted) without a complete understanding of their internal workings. Research has demonstrated that body mass distributions of terrestrial animals broadly reflect ecosystem function. Thus, comparable but causally disconnected terrestrial ecosystems that demonstrate similar body mass distributions would suggest ecosystem convergence. To look for this possible convergence, I generated body mass distributions in a time series for late Miocene North American mammal faunas from the Gulf Coastal Plains, Great Plains, and Pacific coastal region, and compared them with data from the modern Serengeti savanna region. The data show that during the early late Miocene Gulf Coastal Plain faunas resembled each other but were distinctly different from that of the Serengeti, the Great Plains fauna resembled the Serengeti, while the Pacific Coast fauna showed no resemblance to any of the others. However, during the latest Miocene the Gulf Coastal Plain faunas were transformed so as to strongly resemble the Serengeti fauna. The resemblance with the Serengeti was maintained by the Great Plains faunas until at least the end of the Miocene, while the Pacific Coast faunas remained distinctly different from the others. These findings suggest that the late Miocene ecosystems of the Gulf Coastal Plain and Great Plains regions (but not the Pacific Coast region) converged with that of the Serengeti savanna fauna and thus that these ecosystems were/are top-driven rather than bottom-driven in nature.

  12. High resolution sequence stratigraphic analysis of the Late Miocene Abu Madi Formation, Northern Nile Delta Basin

    NASA Astrophysics Data System (ADS)

    Sarhan, Mohammad Abdelfattah

    2015-12-01

    Abu Madi Formation represents the Upper Miocene Messinian age in the Nile Delta basin. It consists mainly of sandstones and shale intercalations and because of its richness in hydrocarbon, it has been subdivided by the petroleum companies into Level-I, Level-II and Level-III, respectively according to the increase in the sandstone to the shale ratio. The Miocene cycle in the northern subsurface section of the Nile Delta encompasses three main formations namely from the base; Sidi Salim formation, Qawasim Formation and Abu Madi Formation at the top. The high resolution sequence stratigraphic analysis, using gamma ray responses, has been done for the Late Miocene formation in the northern part of the Nile delta subsurface section. For this purpose, the gamma-ray logs of ten deep wells, arranged in four cross-sections trending in almost north-south direction throughout the northern region of the Nile Delta, were analyzed. The analysis has revealed that the interpreted 4th order depositional cycles within Abu Madi Formation display great variations in both number and gamma ray responses in each investigated well, and cannot be traced laterally, even in the nearest well. These variations in the interpreted 4th order depositional sequences could be attributed to the presence of normal faults buried in the inter-area laying between the investigated wells. This finding matches with the conclusion of that Abu Madi Formation represents a part of the Upper Miocene Nile Delta syn-rift megasequence, developed during the Upper Miocene rift phase of the Red Sea - Gulf of Suez province in Egypt. Accordingly, in the sequence stratigraphic approach, the depositional history of Abu Madi Formation was strongly overprinted by the tectonic controls rather than the relative sea-level changes which are assumed to be of a secondary influence. Regarding the hydrocarbon aspects of the Abu Madi Formation, the present work recommends to direct the drilling efforts into the stratigraphic traps in the sandy intervals of the LST, TST and HST within the 4th order interpreted depositional sequences in both level-II and/or level-III.

  13. Palinspastic reconstruction of southeastern California and southwestern Arizona for the middle Miocene

    NASA Technical Reports Server (NTRS)

    Richard, Stephen M.

    1992-01-01

    A paleogeographic reconstruction of southeastern California and southwestern Arizona at 10 Ma was made based on available geologic and geophysical data. Clockwise rotation of 39 deg was reconstructed in the eastern Transverse Ranges, consistent with paleomagnetic data from late Miocene volcanic rocks, and with slip estimates for left-lateral faults within the eastern Transverse Ranges and NW-trending right lateral faults in the Mojave Desert. This domain of rotated rocks is bounded by the Pinto Mountain fault on the north. In the absence of evidence for rotation of the San Bernardino Mountains or for significant right slip faults within the San Bernardino Mountains, the model requires that the late Miocene Pinto Mountain fault become a thrust fault gaining displacement to the west. The Squaw Peak thrust system of Meisling and Weldon may be a western continuation of this fault system. The Sheep Hole fault bounds the rotating domain on the east. East of this fault an array of NW-trending right slip faults and south-trending extensional transfer zones has produced a basin and range physiography while accumulating up to 14 km of right slip. This maximum is significantly less than the 37.5 km of right slip required in this region by a recent reconstruction of the central Mojave Desert. Geologic relations along the southern boundary of the rotating domain are poorly known, but this boundary is interpreted to involve a series of curved strike slip faults and non-coaxial extension, bounded on the southeast by the Mammoth Wash and related faults in the eastern Chocolate Mountains. Available constraints on timing suggest that Quaternary movement on the Pinto Mountain and nearby faults is unrelated to the rotation of the eastern Transverse Ranges, and was preceded by a hiatus during part of Pliocene time which followed the deformation producing the rotation. The reconstructed Clemens Well fault in the Orocopia Mountains, proposed as a major early Miocene strand of the San Andreas fault, projects eastward towards Arizona, where early Miocene rocks and structures are continuous across its trace. The model predicts a 14 deg clockwise rotation and 55 km extension along the present trace of the San Andreas fault during late Miocene and early Pliocene time. Palinspastic reconstructions of the San Andreas system based on this proposed reconstruction may be significantly modified from current models.

  14. Palaeoecological construction from the Oligo-Miocene coal deposits of Gelibolu Peninsula, NW Turkey.

    NASA Astrophysics Data System (ADS)

    Demirta?, Ferdi; Ko?un, Erdal; Serkan Akkiraz, Mehmet; Bozcu, Mustafa; Ko, Koray

    2015-04-01

    The palynomorph composition of the Upper Oligocene and Miocene coal deposits from Gelibolu peninsula, NW Turkey, was analyzed to determine the palaeoclimate conditions. The samples were collected from two different abandoned coal mines. Also two different palynological assemblages were reported. The first one belongs to the Late Oligocene (Osmancik Formation). The other one is the Miocene (Gazhanedere Formation). The Late Oligocene palynological assemblage consist mainly of Alnus, Myricaceae, Cyrillaceae-Clethraceae, Calamus and Castanea. Riparian vegetation or wetland forest community incorporate high amounts of Alnus, and low percentages of deciduous Salix, Pterocarya and Carya. Calamus, which is a stratigraphical marker for the Late Oligocene of the Thrace Basin, was also recorded in high quantities. The content of the Miocene palynological assemblage is different from the Late Oligocene assemblage, and is mainly made up of Polypodiaceae, Poaceae, Chenopodiaceae, Myricaceae, Oleaceae, Cyrillaceae-Clethraceae and Sapotaceae. Calamus and Alnus totally disappear here. In contrast, open vegetation elements such Poaceae and Chenopodiaceae occur frequently. The palaeoclimate calculations were made by the help of coexistence approach method. The late Oligocene association contains a total of 18 taxa, 11 of which were used for calculating the coexistence intervals. The values obtained 15.6 to 21.1 C for annual temperature, 5.0 to 13.3 C for winter temperature, 24.7 to 28.1 C for summer temperature and, 1096 to 1355 mm annual rainfall. In the Miocene palynological assemblage 23 taxa were identified. The palaeoclimate calculation is based on the 21 taxa. Quantitative data indicate the values for the mean annual temperature 15.6-21.3 C, for the winter temperature 5.0 to 13.3 C, 24.7- 27.9 C for summer temperature and 823-1520 mm for the annual rainfall. The palaeoclimate was warm and contained dry seasons due to lower boundary of annual precipitation lying at 823 mm during the Miocene. This may be linked ecological dominance of open-habitat grasses such as Poaceae and Chenopodiaceae.

  15. The strontium isotope seawater curve during the early Middle Miocene and its relation to paleoceanographic events

    SciTech Connect

    Hodell, D.A. . Dept. of Geology); Woodruff, F. . Dept. Geological Sciences)

    1992-01-01

    Breaks in slope of the strontium isotope seawater curve signal fundamental changes in either rates of continental weathering, seafloor spreading (i.e., tectonic reorganizations), or submarine dissolution of marine carbonates. The authors conducted a detailed study of the change in slope of the strontium isotopic seawater curve that occurred during the early middle Miocene in three Pacific DSDP sites (289, 574, and 588). The change in slope from the rapid rise in Sr-87/Sr-86 of the early Miocene (60 ppm/Ma) to the less rapid increase of the mid- and late Miocene (22 ppm/Ma) occurred between two periods of maximum [delta]C-13 values dated between 15.5 and 15.2 Ma. This internal was followed by relatively constant Sr-87/Sr-86 values (averaging 0.70878) between 15.2 and 14.2 Ma. Sr-87/Sr-86 ratios began to increase again after 14.2 Ma, but at a reduced rate compared to the early Miocene. The break in slope in Sr-87/Sr-86 preceded the mid-Miocene increase in [delta]O-18 that represents ice growth on Antarctica, which began at 14.9 Ma and increased rapidly after 14.2 Ma. In 2 out of 3 of the sites, the break in Sr-slope between 15.5 and 15.2 Ma is accompanied by a small, but significant, decrease in Sr-87/Sr-86 values. They speculate, that this decrease in Sr-87/Sr-86 may have been related to massive dissolution of older carbonate on the sea floor associated with NH2B (Neogene Hiatus 2 of Keller and Barron, 1983). This event may have important implications for changes in carbonate chemistry of the oceans. Numerical modeling of the strontium isotope budget will be used to test the feasibility of this mechanism and to estimate the volume and age of dissolved carbonate needed to produce the observed decrease in Sr-87/Sr-86.

  16. Southeast Atlantic upwelling intensity changes influencing late Miocene C4 plant expansion?

    NASA Astrophysics Data System (ADS)

    Rommerskirchen, F.; Condon, T.; Mollenhauer, G.; Schefu, E.

    2009-04-01

    The Late Miocene epoch (about 15 to 5 Myrs BP) is characterised by fundamental changes in Earth's climate system: turnovers in marine and terrestrial biota, sea-level variability, changes in surface- und deep-water circulations, and increase in upwelling intensities along the coasts [1,2]. During the transition period the Antarctic ice sheets expanded and were permanently established, while additionally ice volumes began to fluctuate [1]. Plants acting with the C4 concentrating mechanism of CO2 fixation for photosynthesis expanded nearly simultaneous at different places in the world, whereas the global CO2 levels exhibit no corresponding change [1,3]. However, C4 plants are also known to have a competitive advantage in habitats of higher temperature, light and fire intensities as well as of limited water supply, compared to the almost ubiquitous C3 plants. This study tries to give insights to Miocene climatic conditions in Southwest Africa and how these conditions may be linked to the C4 plant expansion. We focused on data from a sediment core of the Ocean Drilling Program (Leg 175, ODP 1085A), which span about 10 Myrs of the late Miocene. The core is situated in the Cape basin at the south-western African continental margin in the upwelling zone of the Benguela coastal current. The current brings cold, nutrient-rich waters from South Atlantic and the Antarctic circumpolar current to the surface water along the coast of Southwest Africa. Miocene sea surface temperatures (SST) were reconstructed by two indices, tetraether index (TEX86) and an alkenone based index (U37K'). Both trends exhibit a shift to cooler temperatures from around 27 to 18? C, but are different in rate and timing. Especially by TEX86 reconstructed SSTs exhibit a similar trend as found for ice volume changes shown by the ?18O curve [4]. These findings may reflect an intensification of the Benguela upwelling current during the late Miocene, probably in association with the formation of West Antarctic ice sheet. The increased upwelling enhances the marine primary production shown by a small overall shift in the total organic carbon (TOC) content (

  17. Thrust faults and extensional detachment faults in Cretan tectono-stratigraphy: Implications for Middle Miocene extension

    NASA Astrophysics Data System (ADS)

    Papanikolaou, Dimitrios; Vassilakis, Emmanuel

    2010-06-01

    The revised tectono-stratigraphy of Crete and especially of the "Phyllites-Quartzites" complex demonstrated the distinction of the probable Paleozoic low-medium grade metamorphic rocks of the Arna unit from the underlying Permo-Triassic phyllites and associated carbonate sediments (Trypali facies) of Western Crete unit as well as the overlying Permo-Triassic phyllites and associated sediments of the Tyros/Ravdoucha Beds at the base of the Tripolis unit. The pre-existing mixture of the above tectono-stratigaphic units in a single complex created a number of misinterpretations as far as stratigraphy, metamorphism and interpretation of low angle faults as thrusts or detachments. Especially in cases where the inferred tectonic contact concerns the transition between the Tyros Beds and the base of the Tripolis carbonate platform there is no structural omission and therefore the contact represents a minor disharmonic sliding surface and not a detachment. Based on the revised tectono-stratigraphic analysis the determination of the structural omission for each tectonic contact was possible and several detachments were described for the first time. Footwall rocks of the detachments comprised several tectonic units usually from the lower nappes and hanging wall rocks comprised several tectonic units usually from the upper nappes. The detachment may separate not only metamorphosed units in the footwall (Mani, Western Crete, Arna) from non metamorphosed units in the hanging wall (Tripolis, Pindos and higher nappes) but also all other possible combinations from the Cretan nappe pile. Extension in Crete started in the Middle-Late Miocene with the formation of extensional detachment faults. The reported extensional structures of Oligocene to Early Miocene age do not correspond to crustal extension of Crete but to localized shear zones related to nappe stacking and the exhumation of metamorphic rocks. Extensional detachments in Crete form a tectonic horst through two oppositely dipping E-W-trending zones; one dipping north, related to the opening of the Cretan basin, and the other dipping south, related to the formation of the Messara supra-detachment basin. The deformation history of units within Crete can be summarized as: (i) compressional deformation producing arc-parallel east-west-trending south-directed thrust faults in Oligocene to Early Miocene time; (ii) extensional deformation along arc-parallel, east-west-trending detachment faults in Middle Miocene time, with hanging wall motion to the north and south; and (iii) Late Miocene-Quaternary transtensional deformation along high-angle normal and oblique normal faults that disrupt the older arc-parallel structures.

  18. Palynology, paleoclimatology and correlation of middle Miocene beds from Porcupine River (locality 90-1), Alaska

    USGS Publications Warehouse

    White, J.M.; Ager, T.A.

    1994-01-01

    Beds in the Upper Ramparts Canyon of the Porcupine River, Alaska (67?? 20' N, 141?? 20' W), yielded a flora rich in pollen of hardwood genera now found in the temperate climates of North America and Asia. The beds are overlain or enclosed by two basalt flows which were dated to 15.2 ?? 0.1 Ma by the 40Ar 39Ar method, fixing the period of the greatest abundance of warm-loving genera to the early part of the middle Miocene. The assemblage is the most northern middle Miocene flora known in Alaska. Organic bed 1 underlies the basalt and is older than 15.2 Ma, but is of early to middle Miocene age. The pollen assemblage from organic bed 1 is dominated by conifer pollen from the pine and redwood-cypress-yew families with rare occurrences of temperate hardwoods. Organic bed 2 is a forest floor containing redwood trees in life position, engulfed by the lowest basalt flow. A pine log has growth rings up to 1 cm thick. Organic beds 3 and 4 comprise lacustrine sediment and peat between the two basalt flows. Their palynoflora contain conifers and hardwood genera, of which about 40% have modern temperate climatic affinities. Hickory, katsura, walnut, sweet gum, wingnut, basswood and elm pollen are consistently present, and beech and oak alone make up about 20% of the pollen assemblage. A warm high latitude climate is indicated for all of the organic beds, but organic bed 3 was deposited under a time of peak warmth. Climate data derived by comparison with modern east Asian vegetation suggest that, at the time of deposition of organic bed 3, the Mean Annual Temperature (MAT) was ca. 9??C, the Warm Month Mean Temperature (WMMT) was ??? 20??C and the Cold Month Mean Temperature (CMMT) was ca. -2??C. In contrast, the modern MAT for the region is -8.6??C, WMMT is 12.6??C and CMMT is -28??C. Organic beds 3 and 4 correlate to rocks of the middle Miocene-late Seldovian Stage of Cook Inlet and also probably correlate to, and more precisely date, the lower third of the Suntrana Formation in the Alaska Range, beds at Unalaklect, part of the upper Mackenzie Bay sequence in the Beaufort-Mackenzie basin, and the Mary Sachs gravel of Banks Island. This suggests that forests with significant percentages of temperate deciduous angiosperms existed between latitudes 60?? and 72??N during the early middle Miocene. ?? 1994.

  19. The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system

    NASA Astrophysics Data System (ADS)

    Latrubesse, Edgardo M.; Cozzuol, Mario; da Silva-Caminha, Silane A. F.; Rigsby, Catherine A.; Absy, Maria Lucia; Jaramillo, Carlos

    2010-05-01

    On the basis of paleontological content (vertebrates and palynology) and facies analysis from river banks, road cuts, and three wells, we have assigned the uppermost levels of the Solimes Formation in western Amazonia, Brazil, to the Late Miocene. The vertebrate fossil record from outcropping sediments is assigned to the Huayquerian-Mesopotamian mammalian biozones, spanning 9-6.5 Ma. Additionally, we present results that demonstrate that deposits in Peruvian Amazonia attributed to Miocene tidal environments are actually fluvial sediments that have been misinterpreted (both environmentally and chronologically) by several authors. The entire Late Miocene sequence was deposited in a continental environment within a subsiding basin. The facies analysis, fossil fauna content, and palynological record indicate that the environment of deposition was dominated by avulsive rivers associated with megafan systems, and avulsive rivers in flood basins (swamps, lakes, internal deltas, and splays). Soils developed on the flatter, drier areas, which were dominated by grasslands and gallery forest in a tropical to subtropical climate. These Late Miocene sediments were deposited from westward of the Purus arch up to the border of Brazil with Peru (Divisor Ranges) and Bolivia (Pando block). Eastward of the Iquitos structural high, however, more detailed studies, including vertebrate paleontology, need to be performed to calibrate with more precision the ages of the uppermost levels of the Solimes Formation. The evolution of the basin during the late Miocene is mainly related to the tectonic behavior of the Central Andes ( 3-15S). At approximately 5 Ma, a segment of low angle of subduction was well developed in the Nazca Plate, and the deformation in the Subandean foreland produced the inland reactivation of the Divisor/Contamana Ranges and tectonic arrangements in the Eastern Andes. During the Pliocene southwestern Brazilian Amazonia ceased to be an effective sedimentary basin, and became instead an erosional area that contributed sediments to the Amazon fluvial system. At that time, the lowland fluvial systems of southwestern Amazonia (the Purus, Jurua and Javar basins) become isolated from the Andes by the newly formed north-flowing Ucayali system and south-east flowing Madre de Dios System. It was during the early Pliocene that the Amazon fluvial system integrated regionally and acquired its present appearance, and also when it started to drain water and sediments on a large scale to the Atlantic Ocean.

  20. The Cenozoic Diversity of Agglutinated Foraminifera - Evidence for a late Oligocene to early Miocene diversification event

    NASA Astrophysics Data System (ADS)

    Kaminski, Michael; Setoyama, Eiichi; Kender, Sev; Cetean, Claudia

    2014-05-01

    The agglutinated foraminifera are among the most abundant micro-organisms in the deep marine environment and have a diversity record extending back to the late Precambrian. We present an updated diversity curve for agglutinated foraminiferal genera based on the stratigraphic ranges of all the agglutinated genera recognized as valid in the classification of Kaminski (2014). The data set for this analysis is based on the stratigraphic ranges of agglutinated genera published in Foraminiferal Genera and their Classification, which has been subsequently updated based on published studies and our new observations. The mean standing diversity of agglutinated foraminiferal genera was compiled by counting the number of boundary crossers rather than the number of genera in each stage. In this study, we report the stratigraphic and geographical occurrence of a benthic foraminiferal diversification event that has previously received little attention. In the latest Oligocene to earliest Miocene a number of trochospiral agglutinated genera with alveolar or canaliculate walls first appeared in the fossil record. Our studies of late Oligocene of the Congo fan, offshore Angola (Kender et al., 2008; Cetean and Kaminski, 2011) have revealed a diverse assemblage that includes new taxa of deep-water agglutinated foraminifera. In a biostratigraphic study of the Miocene foraminiferal assemblages Kender et al. (2008) noted steadily increasing diversity and proportions of infaunal agglutinated foraminiferal morphotypes over the lower Miocene interval. The proportion of infaunal agglutinated foraminifera assigned to the order Textularida increased dramatically in the lower mid-Miocene, suggesting expansion of the oxygen minimum zone into deeper waters. In addition to the trochospiral alveolar genera, several species of Reticulophragmium and Cyclammina display rapid diversification into numerous separate lineages that are at present not reflected in our generic diversity record owing to their poorly established taxonomy. Genera such as Alveovalvulina, Guppyella, Goesella, and Alveovalvulinella, are typical of assemblages found in subtropical oxygen minimum zones, especially in West Africa and the Caribbean. These agglutinated genera are not found in coeval assemblages from the northern high latitudes (Kaminski et al. 2005), suggesting they are restricted to the low-latitude OMZ. It is likely that the global warming of the latest Oligocene to Early Miocene contributed to intensification of dysoxic conditions in low-latitude upwelling regions, possibly from enhanced productivity and reduced deep-sea ventilation, creating an expanded niche for these organisms that flourished in low-oxygen conditions with high particulate organic matter input. We believe a more detailed phylogenetic approach to these agglutinated genera would result in the description of new genera for individual lineages and refinement of the foraminiferal diversity record.

  1. Paleomagnetic quantification of upper-plate deformation during Miocene detachment faulting in the Mohave Mountains, Arizona

    USGS Publications Warehouse

    Pease, V.; Hillhouse, J.W.; Wells, R.E.

    2005-01-01

    Paleomagnetic data from Miocene (???20 Ma) volcanic rocks and dikes of west central Arizona reveal the tilt history of Proterozoic crystalline rocks in the hanging wall of the Chemehuevi-Whipple Mountains detachment fault. We obtained magnetization data from dikes and flows in two structural blocks encompassing Crossman Peak and Standard Wash in the Mohave Mountains. In the Crossman block the dike swarm records two components of primary magnetization: (1) CNH, a normal polarity, high-unblocking-temperature or high-coercivity component (inclination, I = 48.5??, declination, D = 6.4??), and (2) CRHm, a reversed polarity, high-temperature or high-coercivity component (I = -33.6??, D = 197.5??). Argon age spectra imply that the dikes have not been reheated above 300??C since their emplacement, and a baked-contact test suggests that the magnetization is likely to be Miocene in age. CRHm deviates from the expected direction of the Miocene axial dipole field and is best explained as a result of progressive tilting about the strike of the overlying andesite flows. These data suggest that the Crossman block was tilted 60?? to the southwest prior to intrusion of the vertical dike swarm, and the block continued to tilt during a magnetic field reversal to normal polarity (CNH). Miocene dikes in the Crossman block are roughly coplanar, so the younger dikes with normal polarity magnetization intruded along planes of weakness parallel to the earlier reversed polarity swarm. An alternative explanation involves CNH magnetization being acquired later during hydrothermal alteration associated with the final stages of dike emplacement. In the Standard Wash block, the primary component of magnetization is a dual-polarity, high-temperature or high-coercivity component (SWHl, I = 7.2??,D= 0.7??). To produce agreement between the expected Miocene magnetic direction and the SWH component requires (1) correcting for a 56?? tilt about the strike of flow bedding and (2) removing a counterclockwise vertical-axis rotation of 20??. The two rotations restore the Standard Wash dikes to vertical, make parallel the dike layering in the Crossman and Standard Wash blocks, and align the strikes of bedding in both blocks. Geologic mapping, geochemical evidence, and paleomagnetic data are consistent with the upper plate of the Mohave Mountains having tilted in response to formation of the underlying detachment fault.

  2. Episodic exhumation of the Greater Himalayan Sequence since the Miocene constrained by fission track thermochronology in Nyalam, central Himalaya

    NASA Astrophysics Data System (ADS)

    Wang, An; Garver, John I.; Wang, Guocan; Smith, Jacqueline A.; Zhang, Kexin

    2010-12-01

    The Greater Himalayan Sequence (GHS), which makes up the core of the Himalayan orogen, has an uppermost tectonic contact defined by the South Tibetan Detachment System (STDS) and a lower tectonic contact defined by the Main Central Thrust (MCT). The GHS occurs as one of the most important tectostratigraphic units for deciphering processes related to tectonic and climatic exhumation across the orogen. Zircon and apatite fission track (ZFT, AFT) dating were carried out along a transect in Nyalam, central Himalaya in southern Tibet to constrain cooling driven by orogenic process since the middle Miocene. The hanging wall of the STDS yields an essentially unreset Jurassic ZFT age in the Jurassic strata. However, below the STDS within the GHS there is a clear and distinct thermal signal of cooling related to exhumation. In the footwall and within the GHS, the rocks have ZFT ages of middle Miocene to Pliocene, and AFT ages of late Miocene to Quaternary that get younger downward and away from the STDS. In combination with thermal structure modeling, a two-part episodic model, which is widely compatible with existing thermochronological data, is proposed for cooling and exhumation of the GHS since the middle Miocene: [1] middle Miocene; and [2] Pliocene to Quaternary (Recent). The middle Miocene cooling is suggested to have resulted from a rapid tectonic unroofing by down-to-the-north slip on the STDS. The tectonic exhumation was also recorded by several other thermochronological systems (e.g. biotite 40Ar/ 39Ar) with concordant middle Miocene cooling ages in different structural positions across the GHS. Post middle Miocene ZFT and AFT cooling ages in the lower part of the GHS suggest accelerated cooling by climate-enhanced erosional exhumation, which was initiated in the late Miocene to Pliocene and was dramatic in the Quaternary to Recent. Thermochronological data and modeling further imply that the present Himalayan topographic front may have been shaped essentially by surface erosion since the late Miocene, when the Himalayan divide might have been some 20-30 km to the south of its present position. However, these data do not preclude the possibility that the intense erosional exhumation may have triggered rock uplift to approach and/or maintain a steady topography in the GHS.

  3. Paleo-environment in the upper amazon basin during early to middle Miocene times

    NASA Astrophysics Data System (ADS)

    van Soelen, Els; Hoorn, Carina; Santos, Roberto V.; Dantas, Elton L.; Sinninghe Damst, Jaap S.; Kim, Jung-Hyun

    2014-05-01

    The Amazon River has the largest catchment in the world and is responsible for the largest water discharge from land to the ocean. The river system that flows from the Andes to the Atlantic Equatorial Margin exists since the late Miocene, and results from Andean uplift which strongly affected erosion/deposition and major flow patterns in northern South-America. Two outcrop sites from the Solimes basin, Mariame (17.7-16.1 Ma) and Los Chorros (14.2-12.7 Ma), may shed light on the inland paleo-environmental conditions during a period of active Andean uplift in the early to middle Miocene. Earlier works revealed the Mariame outcrops to represent a river born in Amazonia. Instead the Los Chorros outcrops are relics of the Amazon River system, characterized by extensive wetlands consisting of swamps, shallow lakes, crevasse splays channels and crevasse-delta lakes (e.g. Hoorn et al., 2010). The freshwater ecosystems alternate with some intervals that are rich in marine palynomorphs (such as dinocysts), mangrove pollen, brackish tolerant molluscs and ostracods, which indicate brackish conditions and a marine influence. It is thought that these marine incursion are related to phases of global sea-level rise and rapid subsidence in the Andean foreland (Marshall & Lundberg, 1996). Still, much remains unknown about the Miocene river systems, like the extent and diversity of the wetland system and the nature of the marine incursions. To get a better understanding of the sources of the (in)organic material, geochemical methods were used. Strontium (Sr) and Neodymium (Nd) isotopes were analyzed on bulk sediments, and used for a paleo-provenance study. The Sr and Nd isotopic signature in the older section (Mariame) is in general more radiogenic compared to the Los Chorros section. The most radiogenic values are comparable to those found nowadays in the the Precambrian Guyana shield. A Guyana sediment source would suggest a distinctly different flow direction of the major rivers during early-middle Miocene. The younger Los Chorros sediments show Sr and Nd values comparable to those nowadays found in the Solimes region, indicating an Andean source existed already during early-middle Miocene times. Lipid biomarkers were identified and quantified and carbon isotopic compositions of organic matter for whole samples were determined to identify the sources of organic matter. Ratio's between typically terrestrial and aquatic GDGTs indicate shifts between more terrestrial settings and more aquatic settings. Intervals which suggest a more aquatic setting often contain marine palynomorphs and thus could result from a marine incursion at the time. Changes in the overall composition of biomarker lipids at each site reflects the diversity and dynamic features of the wetland. Differences in both provenance and biomarker composition between the two sites demonstrate the diversity within the basin. This diversity could either be geographical diversity since the two sites are located about 380 km from each other. Or, considering the differences in age between the two sites of 2-5 Myrs, it could also reflect the fast changing environmental conditions as a result of Andean uplift. Hoorn, C. et al (2010). The Development of the Amazonian Mega-Wetland (Miocene; Brazil, Colombia, Peru, Bolivia). In: C. Hoorn and F. Wesselingh (eds) Amazonia: Landscape and Species Evolution: A look into the past. Wiley-Blackwell Publishing Ltd., pp. 123- 142. Marshall, L.G., Lundberg, J.G. (1996) Miocene deposits in the Amazonian Foreland Basin. Science 273, 123-124.

  4. Post-Miocene Right Separation on the San Gabriel and Vasquez Creek Faults, with Supporting Chronostratigraphy, Western San Gabriel Mountains, California

    USGS Publications Warehouse

    Beyer, Larry A.; McCulloh, Thane H.; Denison, Rodger E.; Morin, Ronald W.; Enrico, Roy J.; Barron, John A.; Fleck, Robert J.

    2009-01-01

    The right lateral San Gabriel Fault Zone in southern California extends from the northwestern corner of the Ridge Basin southeastward to the eastern end of the San Gabriel Mountains. It bifurcates to the southeast in the northwestern San Gabriel Mountains. The northern and older branch curves eastward in the range interior. The southern younger branch, the Vasquez Creek Fault, curves southeastward to merge with the Sierra Madre Fault Zone, which separates the San Gabriel Mountains from the northern Los Angeles Basin margin. An isolated exposure of partly macrofossiliferous nearshore shallow-marine sandstone, designated the Gold Canyon beds, is part of the southwest wall of the fault zone 5.5 km northwest of the bifurcation. These beds contain multiple subordinate breccia-conglomerate lenses and are overlain unconformably by folded Pliocene-Pleistocene Saugus Formation fanglomerate. The San Gabriel Fault Zone cuts both units. Marine macrofossils from the Gold Canyon beds give an age of 5.2+-0.3 Ma by 87Sr/86Sr analyses. Magnetic polarity stratigraphy dates deposition of the overlying Saugus Formation to between 2.6 Ma and 0.78 Ma. Distinctive metaplutonic rocks of the Mount Lowe intrusive suite in the San Gabriel Range are the source of certain clasts in both the Gold Canyon beds and Saugus Formation. Angular clasts of nondurable Paleocene sandstone also occur in the Gold Canyon beds. The large size and angularity of some of the largest of both clast types in breccia-conglomerate lenses of the beds suggest landslides or debris flows from steep terrain. Sources of Mount Lowe clasts, originally to the north or northeast, are now displaced southeastward by faulting and are located between the San Gabriel and Vasquez Creek faults, indicating as much as 12+-2 km of post-Miocene Vasquez Creek Fault right separation, in accord with some prior estimates. Post-Miocene right slip thus transferred onto the Vasquez Creek Fault southeast of the bifurcation. The right separation on the Vasquez Creek Fault adds to the generally accepted 22-23 km of middle-late Miocene right separation established for the San Gabriel Fault east of the bifurcation, resulting in total right separation of 34-35 km northwest of the bifurcation. Clast sizes and lithologies in Saugus Formation deformed alluvial fan deposits in the Gold and Little Tujunga Canyons area indicate that alluvial stream flow was from the north or north-northeast. The alluvial fan complex is beheaded at the San Gabriel Fault Zone, and no correlative deposits have been found north of the fault zone. Likely sources of several distinctive clast types are east of the bifurcation and north of the Vasquez Creek Fault. Combining these data with right slip caused by the 34 deg +-6 deg of clockwise local block rotation suggests that post-Saugus Formation (<2.6 to 0.78 Ma) right separation along the fault zone is 4+-2 km. The fossils, lithology, and age of the Gold Canyon beds correlate with the basal Pico Formation. The beds presumably connected southward or southwestward to a more open marine setting. A search for correlative strata to the south and southwest found that some strata previously mapped as Towsley Formation correlate with the Modelo Formation. Oyster spat in some Modelo Formation beds are the first recorded fossil occurrences and are especially remarkable because of associations with Miocene bathyal benthic foraminifers, planktonic calcareous nannofossils, and diatoms. Topanga Group basalt resting on basement rocks between Little and Big Tujunga Canyons gives an age of 16.14+-0.05 Ma from 40Ar/39Ar analysis. Improved understanding of the upper Miocene stratigraphy indicates large early movement on the eastern Santa Susana Fault at about 7-6 Ma.

  5. Early to middle Miocene vegetation history of Antarctica supports eccentricity-paced warming intervals during the Antarctic icehouse phase

    NASA Astrophysics Data System (ADS)

    Griener, Kathryn W.; Warny, Sophie; Askin, Rosemary; Acton, Gary

    2015-04-01

    Recent palynological evidence from the upper section (< 664 mbsf) of the Miocene ANDRILL 2A (AND-2A) core in the Ross Sea indicated a brief warm period during the Mid Miocene Climatic Optimum (MMCO), during Antarctica's icehouse phase. The nature of other Miocene climate fluctuations in Antarctica remains poorly resolved. Here, we present new palynological data from the lower section of the AND-2A core (> 664 mbsf) that reveal additional intervals of increased palynomorph abundance and diversity during the Antarctic early to middle Miocene. This evidence is consistent with a relatively dynamic early Miocene Antarctic icehouse climate with intervals of increased temperature and moisture, prior to the MMCO. Comparison with previous AND-2A studies indicates that periods of increased palynomorph abundance in the lower stratigraphic section largely coincide with ice sheet minima, distal ice conditions, and the presence of freshwater (i.e. increased precipitation, meltwater run-off, and freshwater ponds). Decreases in plant productivity mostly coincide with increased glaciation, decreased freshwater, and ice-proximal conditions during the Antarctic Miocene. Comparing the palynological data with other AND-2A data and global climate proxies (e.g., pCO2, ?18O, relative sea level, Milankovitch cycles) helps to resolve questions regarding the driving forces behind climate and vegetation change. We found that palynomorph assemblages reflecting generally warmer conditions are largely associated with 400-kyr eccentricity maxima, while assemblages indicative of colder conditions coincide with 400-kyr eccentricity minima. These data are consistent with other findings that indicate the early to middle Miocene climate was eccentricity-paced.

  6. Depositional patterns and hydrocarbon occurrence in middle to upper Miocene strata in part of the western Niger Delta Basin, Nigeria

    NASA Astrophysics Data System (ADS)

    Agyingi, C. M.; Agagu, O. K.; Fozao, K. F.; Njoh, O. A.; Ngalla, N.

    2013-04-01

    The relation of depositional patterns to hydrocarbon occurrence in middle to upper Miocene strata of part of the western Niger Delta Basin is postulated from the study of electrical logs, radiometric logs, lithologic logs, bottom hole temperatures, intervals of hydrocarbon occurrence and paleontological data. Alternating sands and shales of the Agbada Formation were deposited in the area (up to 720 m, middle Miocene and 510 m, upper Miocene) mainly as regressive off lap sequences in a paralic environment with depo-centers located in the south of the study area. Three deltaic facies can be recognized based on the relative amounts of shale and sand including, proximal delta front facies (>70% sand), distal delta front facies (30-70% sand) and prodelta facies (<30% sand). The upper Miocene is generally sandier than the middle Miocene as a result of south-westerly progradation of delta front facies from middle to upper Miocene. Geothermal gradients in the area range from 2.5 C/100 m to 4.4 C/100 m. Isothermal maps show that some middle to upper Miocene shales could have undergone catagenesis to become mature source rocks. Three depositional zones (A, B, C) corresponding to dominant depositional facies i.e., proximal delta, distal delta and prodelta respectively, have been delineated from sand percentage maps. There is a progression of these zones from A through B to C in a generally south-westerly direction (the direction of delta progradation). Data for hydrocarbon intervals reveal the predominance of hydrocarbons in Zone C due to high entrapment potentials and to a lesser extent in Zone B. Zone A is barren as a result of poor entrapment potentials. The juxtaposition of distal delta front sands and prodelta mud could have initiated growth faults which constitute the major types of traps in the basin.

  7. The palaeoclimatic significance of Eurasian Giant Salamanders (Cryptobranchidae: Zaissanurus, Andrias) - indications for elevated humidity in Central Asia during global warm periods (Eocene, late Oligocene warming, Miocene Climate Optimum)

    NASA Astrophysics Data System (ADS)

    Vasilyan, Davit; Böhme, Madelaine; Winklhofer, Michael

    2010-05-01

    Cryptobranchids represent a group of large sized (up to 1.8 m) tailed amphibians known since the Middle Jurassic (Gao & Shubin 2003). Two species are living today in eastern Eurasia: Andrias davidianus (China) and A. japonicus (Japan). Cenozoic Eurasian fossil giant salamanders are known with two genera and two or three species from over 30 localities, ranging from the Late Eocene to the Early Pliocene (Böhme & Ilg 2003). The Late Eocene species Zaissanurus beliajevae is restricted to the Central Asian Zaissan Basin (SE-Kazakhstan, 50°N, 85°E), whereas the Late Oligocene to Early Pliocene species Andrias scheuchzeri is distributed from Central Europe to the Zaissan Basin. In the latter basin the species occur during two periods; the latest Oligocene and the late Early to early Middle Miocene (Chkhikvadse 1982). Andrias scheuchzeri is osteological indistinguishable from both recent species, indicating a similar ecology (Westfahl 1958). To investigate the palaeoclimatic significance of giant salamanders we analyzed the climate within the present-day distribution area and at selected fossil localities with independent palaeoclimate record. Our results indicate that fossil and recent Andrias species occur in humid areas where the mean annual precipitation reach over 900 mm (900 - 1.300 mm). As a working hypothesis (assuming a similar ecology of Andrias and Zaissanurus) we interpret occurrences of both fossil Eurasian giant salamanders as indicative for humid palaeoclimatic conditions. Based on this assumption the Late Eocene, the latest Oligocene (late Oligocene warming) and the late Early to early Middle Miocene (Miocene Climatic Optimum) of Central Asia (Zaissan Basin) are periods of elevated humidity, suggesting a direct (positive) relationship between global climate and Central Asian humidity evolution. Böhme M., Ilg A. 2003: fosFARbase, www.wahre-staerke.com/ Chkhikvadze V.M. 1982. On the finding of fossil Cryptobranchidae in the USSR and Mongolia. Vertebrata Hungarica, 21: 63-67. Gao K.-Q., Shubin N.H. 2003. Earliest known crown-group Salamanders. Nature, 422: 424-428. Westphal F. 1958. Die Tertiären und rezenten Eurasiatischen Riesensalamander. Palaeontolographica Abt. A, 110: 20-92.

  8. CONTROLS OF EXTENSION ON MIOCENE ARC MAGMATISM IN THE CENTRAL SIERRA NEVADA (CA)

    NASA Astrophysics Data System (ADS)

    Busby, C.; Putirka, K. D.; Hagan, J. C.; Koerner, A.; Melosh, B. L.

    2009-12-01

    Ancestral Cascades arc volcanism in the central Sierra Nevada occurred in three Miocene pulses, at about 16-13 Ma, 11-9 Ma, and 7-6 Ma. Our work in the Carson Pass to Sonora Pass areas shows that range-front faults clearly controlled the positions of volcanic centers during the second and third magmatic pulses. Voluminous high-K volcanic rocks of the 11-9 Ma Stanislaus Group record the onset of transtensional calving of the Sierra Nevada microplate off the western edge of the Nevadaplano. The Little Walker Caldera or Center formed at a releasing stepover in range-front faults at Sonora Pass, and erupted widesperad trachydacite ignimbrite in three distinct phases (Eureka Valley Tuff). Interstratified with these ignimbrites are widespread trachyandesite (latite), basaltic-trachyandesite (shoshonite) and trachydacite lava flows, in sections up to 500 m thick, whose vents have never been discovered (e.g. Table Mountain Latite). Although some of these lavas may have erupted from vents buried beneath the Little Walker Center, we recognize intrusions and vent facies for them along Sierran range-front and range-crest faults that emanate northwestward from the Little Walker Center between Sonora Pass and Ebbetts Pass. The biggest volcanic centers of the third magmatic pulse also include silicic volcanic rocks, and are sited along normal faults; they include the Markleeville Center southeast of Carson Pass, and the Ebbetts Pass Center. The 8 km diameter Markleeville Center consists of andesites and dacites that formed within the Hope Valley graben. The next fault to the east of the Hope Valley graben, which we name the Grover Hot Springs fault, extends southward to Ebbetts Pass, where it forms an overlapping right (releasing) step with the Noble Canyon fault to the west. The Ebbetts Pass Center lies above this releasing step along the Sierran crest. The base of the Ebbetts Pass Center is 10 km in diameter and is formed of radially-dipping basaltic andesite lava flows and overlying scoria fall deposits with internal slide and slump features, preserved on the Silver Peak-Highland Peak area; these pass outward into block-and-ash flow tuffs of the same composition preserved along the crest another 8 km to the northwest at Reynolds Peak. The basal basaltic andesite core is intruded by silicic plugs on Silver Peak-Highland-Peak, with eruptive equivalents represented by silicic block-and ash-flow tuffs that cap the crest at Reynolds Peak. Rhyolite lava flows up to 300 m thick fill a paleocanyon on the south flank of the center. The Ebbetts Pass Center evidently occupies a deep pull-apart basin, since thick, distinctive strata of magmatic pulse 2 (Stanislaus Group) that map continuously from Sonora Pass northward to the Ebbetts Pass center along the Sierran crest drop abruptly out of view beneath it.

  9. Strontium, Lead, and Oxygen Isotopic Signatures of Mid-Miocene Silicic Volcanism in Eastern Oregon

    NASA Astrophysics Data System (ADS)

    Hess, Emily Nancy

    Widespread, mid-Miocene rhyolite volcanism of eastern Oregon that are coeval or slightly postdate flood basalts of the Columbia River Basalt Province allows for mapping crustal domains using radiogenic and stable isotopes. Rhyolites are thought to be derived in large part by partial melting of the crust and thus yield direct information on the composition of the crust. Silicic volcanism is expressed in the form of numerous domes and tuffs exposed over a wide area (~300 km in N-S dimension and ~200 km in E-W dimension) west of the presumed craton boundary, which runs parallel but mostly east of the Oregon-Idaho state border as delineated by geophysical characteristics and isotopic transitions, including the 87Sr/86Sri =0.7060 line (MSL) and 87Sr/86Sri =0.7040 line (CSL). 87Sr/86Sri of twenty-seven silicic units are variable and some are high. Sr isotopic ratios are inconsistent with the location of the traditional MSL and CSL boundaries. A primary control on the 87Sr/86Sri isotope variations may reflect changes in the crustal make-up of Paleozoic accreted terranes of a particular area rather than arising from a westward-dipping decollement that moved cratonic lithosphere below accreted terranes in eastern Oregon. A secondary control on observed isotopic ratios may be related to the amount and composition of basalt involved in the generation of rhyolites. This could lead to higher or lower 87Sr/86Sri relative to the surrounding crust because de facto coeval mafic magmas of the Columbia River Basalt Group have a wide range of Sr isotopic signatures. While Pb isotope data is incomplete for all samples of this study, the available data indicate a significant range in Pb isotopes. Yet, data of individual regions tend to plot close to one another relative to the entire data distribution. Comparison of samples from this study in a more regional view indicates the samples generally fall within the previously defined lead isotope boundaries of the main-phase Columbia River Basalt Group lavas. delta18O values range from below 2‰ to above 9‰. In addition, there is a crude trend of rhyolites having lower delta 18O and more radiogenic 87Sr/86Sri ratios. The lowest oxygen ratios (<2‰) are found in rhyolites ~80 km west of the cratonic margin, potentially reflecting remelting or assimilation of hydrothermally altered crust. Low delta18O of selected rhyolite flows cannot be explained by remelting of Cretaceous plutons of the Idaho Batholith and appear irreconcilable with remelting of altered silicic rocks at centers of multiple, confocal caldera cycles-- both processes that have been proposed to explain low delta18O of rhyolites of the Snake River Plain--Yellowstone area.

  10. DNA barcodes from four loci provide poor resolution of taxonomic groups in the genus Crataegus

    PubMed Central

    Zarrei, Mehdi; Talent, Nadia; Kuzmina, Maria; Lee, Jeanette; Lund, Jensen; Shipley, Paul R.; Stefanović, Saša; Dickinson, Timothy A.

    2015-01-01

    DNA barcodes can facilitate identification of organisms especially when morphological characters are limited or unobservable. To what extent this potential is realized in specific groups of plants remains to be determined. Libraries of barcode sequences from well-studied authoritatively identified plants represented by herbarium voucher specimens are needed in order for DNA barcodes to serve their intended purpose, where this is possible, and to understand the reasons behind their failure to do so, when this occurs. We evaluated four loci, widely regarded as universal DNA barcodes for plants, for their utility in hawthorn species identification. Three plastid regions, matK, rbcLa and psbA-trnH, and the internal transcribed spacer 2 (ITS2) of nuclear ribosomal DNA discriminate only some of the species of Crataegus that can be recognized on the basis of their morphology etc. This is, in part, because in Rosaceae tribe Maleae most individual plastid loci yield relatively little taxonomic resolution and, in part, because the effects of allopolyploidization have not been eliminated by concerted evolution of the ITS regions. Although individual plastid markers provided generally poor resolution of taxonomic groups in Crataegus, a few species were notable exceptions. In contrast, analyses of concatenated sequences of the 3 plastid barcode loci plus 11 additional plastid loci gave a well-resolved maternal phylogeny. In the ITS2 tree, different individuals of some species formed groups with taxonomically unrelated species. This is a sign of lineage sorting due to incomplete concerted evolution in ITS2. Incongruence between the ITS2 and plastid trees is best explained by hybridization between different lineages within the genus. In aggregate, limited between-species variation in plastid loci, hybridization and a lack of concerted evolution in ITS2 all combine to limit the utility of standard barcoding markers in Crataegus. These results have implications for authentication of hawthorn materials in natural health products. PMID:25926325

  11. DNA barcodes from four loci provide poor resolution of taxonomic groups in the genus Crataegus.

    PubMed

    Zarrei, Mehdi; Talent, Nadia; Kuzmina, Maria; Lee, Jeanette; Lund, Jensen; Shipley, Paul R; Stefanović, Saša; Dickinson, Timothy A

    2015-01-01

    DNA barcodes can facilitate identification of organisms especially when morphological characters are limited or unobservable. To what extent this potential is realized in specific groups of plants remains to be determined. Libraries of barcode sequences from well-studied authoritatively identified plants represented by herbarium voucher specimens are needed in order for DNA barcodes to serve their intended purpose, where this is possible, and to understand the reasons behind their failure to do so, when this occurs. We evaluated four loci, widely regarded as universal DNA barcodes for plants, for their utility in hawthorn species identification. Three plastid regions, matK, rbcLa and psbA-trnH, and the internal transcribed spacer 2 (ITS2) of nuclear ribosomal DNA discriminate only some of the species of Crataegus that can be recognized on the basis of their morphology etc. This is, in part, because in Rosaceae tribe Maleae most individual plastid loci yield relatively little taxonomic resolution and, in part, because the effects of allopolyploidization have not been eliminated by concerted evolution of the ITS regions. Although individual plastid markers provided generally poor resolution of taxonomic groups in Crataegus, a few species were notable exceptions. In contrast, analyses of concatenated sequences of the 3 plastid barcode loci plus 11 additional plastid loci gave a well-resolved maternal phylogeny. In the ITS2 tree, different individuals of some species formed groups with taxonomically unrelated species. This is a sign of lineage sorting due to incomplete concerted evolution in ITS2. Incongruence between the ITS2 and plastid trees is best explained by hybridization between different lineages within the genus. In aggregate, limited between-species variation in plastid loci, hybridization and a lack of concerted evolution in ITS2 all combine to limit the utility of standard barcoding markers in Crataegus. These results have implications for authentication of hawthorn materials in natural health products. PMID:25926325

  12. Late cenozoic evolution of Fortymile Ash: Major change in drainage pattern in the Yucca Mountain, Nevada region during late miocene volcanism

    SciTech Connect

    Lundstrom, S.C.; Warren, R.G.

    1994-12-31

    Analysis of sedimentary provenance and altitude distribution of volcanic strata along Fortymile Wash, the primary desert wash east of Yucca Mountain, NV, indicates a major change in surface drainage basins related to late Miocene volcanic disruption. This event resulted in the establishment of the modern Fortymile Wash basin before 3 Ma, and probably by latest Miocene time. An understanding of this event is useful for evaluation of extensive alluviation east of Yucca Mountain and its relation to paleoclimate, hydrology and tectonics. To the northeast of Yucca Mountain, Fortymile Wash provides southward surface drainage from 60% of the area of the 11 Ma Timber Mountain caldera via Fortymile Canyon, a major breach in the caldera wall. In the southeast caldera moat, the distribution of volcanic units that predate and include the 9.4 Ma Thirsty Canyon Group and the characteristics of intercalated sediments indicate a northward paleoslope and sediment transport from a major drainage divide near Dome Mountain, a shield volcano now deeply incised by Fortymile Canyon. Eruption of the Thirsty Canyon Group from the Black Mountain area, 10 km northwest of the Timber Mountain caldera, is likely to have dammed a counterclockwise drainage system of the east moat. Following drainage disruption, the east moat filled with sediment up to the level of a new southward outlet at the saddle between Dome Mountain and the onlapping rhyolite of Shoshone Mountain. An older canyon south of this saddle received the overflow from the east moat and became the throughgoing Fortymile Canyon, integrating the east moat basin with a lower base level in Jackass Flats. Well-integrated southward drainage existed by the time the trachybasalt flows of Buckboard Mesa (2.8 Ma) were emplaced, because basal elevations of these flows slope southward about 100 m above modern Fortymile Wash.

  13. Effects of antecedent topography on reefal carbonate deposition: Early-Middle Miocene of the Adana Basin, S Turkey

    NASA Astrophysics Data System (ADS)

    Gl, Murat

    2007-08-01

    Early-Middle Miocene reefal limestones and other shallow marine sedimentary sequences were important components of Neogene Basins (especially the Adana Basin) in Southern Turkey. The most important controlling factors of sedimentation were antecedent topography and substratum type, clastic input and sea level changes of different scales. The effects of these factors can be observed on the southwest extension of the Adana Basin. Miocene sediments unconformably overlie the older limestones, ophiolite and ophiolitic melange. Lithological variations and structural properties of Pre-Miocene rocks caused an irregular sea floor topography development that was initially filled by local terrestrial conglomerates. During the Early Miocene transgression, these terrestrial clastics transitionally passed into shallow marine clastics, and also new pebbly conglomerate-sandstone bearing deposits observed in local depressions of Pre-Miocene topography. Remaining low lying areas were filled by claystones and sandy-clayey limestones. At the same time, reef limestone deposition developed over the higher areas where a hard-substratum was available for red algae and other reef builders. Large shelled organisms in the clastics created a suitable substratum for successive reef level development. The carbonate deposition shifted landwards due to continuous transgression (intermediate sea level changes) causing backstepping reef development. Small sea level changes in the study area controlled the energy of the environment, lithological variations in the clastics and lateral facies changes in each reef body.

  14. A drastic lower Miocene regolith evolution triggered by post obduction slab break-off and uplift in New Caledonia

    NASA Astrophysics Data System (ADS)

    Sevin, Brice; Cluzel, Dominique; Maurizot, Pierre; Ricordel-Prognon, Caroline; Chaproniere, George; Folcher, Nicolas; Quesnel, Florence

    2014-09-01

    A lower Miocene coarse conglomerate that crops out in the Npoui Peninsula does not represent the base of the marine transgression that followed obduction in New Caledonia. Instead, the conglomeratic alluvial fan that contains peridotite cobbles and reworked weathering products records a short-lived episode of terrestrial erosion intercalated between two intervals of subsidence marked by marine carbonate deposition. Considering the Miocene sea level evolution reported in the literature, it is concluded that neither lower Miocene transgression nor erosion were driven by sea level variation. In contrast, a southeastward propagating slab tear that initiated at the latitude of the high pressure/low temperature metamorphic complex of northern New Caledonia likely generated east to west tilting of New Caledonia, subsidence along the West Coast and hence fringing reef development together with moderate erosion of older regolith. Coincidence between conglomerate deposition and hence prominent erosion that closely followed emplacement of postobduction granitoids influenced by a slab window suggests a genetic link. Therefore, it is concluded that short-lived lower Miocene erosion was due to slab breakoff and subsequent uplift that occurred at ~ 22 Ma. Lower Miocene erosion profoundly dissected the Peridotite Nappe and in the northern half of New Caledonia only left isolated klippes along the West Coast.

  15. Fossil wood from the upper Miocene Mpesida Beds at Cheparain (Baringo District, Kenya): Botanical affinities and palaeoenvironmental implications

    NASA Astrophysics Data System (ADS)

    De Franceschi, Dario; Bamford, Marion; Pickford, Martin; Senut, Brigitte

    2016-03-01

    Seven wood samples from a petrified forest, in situ in ash flow deposits at Cheparain in the Tugen Hills (Kenya) in the Mpesida Beds, were discovered and studied. The age of the Mpesida Formation is estimated to be about 6.3 Ma on the basis of radio-isotope age determinations on the volcanic deposits, which overlie and underlie the sedimentary levels. The wood samples are mineralized with obvious sectors of differential mineralization, and different degrees of silica impregnation. All samples show heteroxylous structures corresponding to angiosperm dicotyledon trees. One sample consists in a half cylinder showing a well preserved mineralized structure of heteroxylous wood and probably corresponds to a fragment of root. This wood, with solitary (or in radial group) vessels, heterocellular multiseriate rays, paratracheal parenchyma in wide bands, and partly storied fusiform cells, clearly shows affinities with the genus Erythrina (Fabaceae). A slightly compressed branch, partly disturbed by injuries and highly mineralized shows solitary (or in short radial group) vessels, the rays uni-(bi) seriate are heterocellular, and the apotracheal parenchyma is in thin tangential bands. The closest affinities are with the genus Spirostachys (Euphorbiaceae). The other structures are poorly preserved (highly mineralized) and precise botanical affinities cannot be accessed. But the growth rings are distinct or diversely marked and the samples show semi-ring porous structures. They exhibit two different patterns. The growth rings reveal the presence of seasonal climate, and numerous injuries, a disturbance of the vegetation by animals and/or strong climatic events. Erythrina and Spirostachys are present in the extant vegetation of the Tana River Valley, in Kenya, which could represent a modern analogue for the vegetation of the Mpesida Beds prior to the major uplift of the Tugen Hills at the end of the Miocene.

  16. On Mesopithecus habitat: Insights from late Miocene fossil vertebrate localities of Bulgaria.

    PubMed

    Clavel, Julien; Merceron, Gildas; Hristova, Latinka; Spassov, Nikolaï; Kovachev, Dimitar; Escarguel, Gilles

    2012-07-01

    The aim of this study is to describe the environments where the cercopithecid Mesopithecus was found during latest Miocene in Europe. For this purpose, we investigate the paleoecology of the herbivorous ungulate mesofauna of three very rich late Miocene fossil localities from southwestern Bulgaria: Hadjidimovo, Kalimantsi and Strumyani. While Mesopithecus has been found in the two first localities, no primate remains have yet been identified in Strumyani. Comparison between localities with and without primates using the herbivore mesofauna allows the cross-corroboration of paleoenvironmental conditions where this primate did and did not live. A multi-parameter statistical approach involving 117 equid and 345 bovid fossil dental and postcranial (phalanges, metapodia, astragali) remains from these three localities provides species to generic-level diet and locomotor habit information in order to characterize the environment in which Mesopithecus evolved. The analysis of dental mesowear indicates that the bovids were mainly mixed feeders, while coeval equids were more engaged in grazing. Meanwhile, postcranial remains show that the ungulate species from Hadjidimovo and Kalimantsi evolved in dry environments with a continuum of habitats ranging from slightly wooded areas to relatively open landscapes, whereas the Mesopithecus-free Strumyani locality was in comparison reflecting a rather contrasted mosaic of environments with predominant open and some more closed and wet areas. Environments in which Mesopithecus is known during the late Miocene were not contrasted landscapes combining open grassy areas and dense forested patches, but instead rather restricted to slightly wooded and homogeneous landscapes including a developed grassy herbaceous layer. PMID:22677560

  17. Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama

    PubMed Central

    Pimiento, Catalina; Ehret, Dana J.; MacFadden, Bruce J.; Hubbell, Gordon

    2010-01-01

    Background As we know from modern species, nursery areas are essential shark habitats for vulnerable young. Nurseries are typically highly productive, shallow-water habitats that are characterized by the presence of juveniles and neonates. It has been suggested that in these areas, sharks can find ample food resources and protection from predators. Based on the fossil record, we know that the extinct Carcharocles megalodon was the biggest shark that ever lived. Previous proposed paleo-nursery areas for this species were based on the anecdotal presence of juvenile fossil teeth accompanied by fossil marine mammals. We now present the first definitive evidence of ancient nurseries for C. megalodon from the late Miocene of Panama, about 10 million years ago. Methodology/Principal Findings We collected and measured fossil shark teeth of C. megalodon, within the highly productive, shallow marine Gatun Formation from the Miocene of Panama. Surprisingly, and in contrast to other fossil accumulations, the majority of the teeth from Gatun are very small. Here we compare the tooth sizes from the Gatun with specimens from different, but analogous localities. In addition we calculate the total length of the individuals found in Gatun. These comparisons and estimates suggest that the small size of Gatun's C. megalodon is neither related to a small population of this species nor the tooth position within the jaw. Thus, the individuals from Gatun were mostly juveniles and neonates, with estimated body lengths between 2 and 10.5 meters. Conclusions/Significance We propose that the Miocene Gatun Formation represents the first documented paleo-nursery area for C. megalodon from the Neotropics, and one of the few recorded in the fossil record for an extinct selachian. We therefore show that sharks have used nursery areas at least for 10 millions of years as an adaptive strategy during their life histories. PMID:20479893

  18. Antarctic Ice Sheet dynamics in the Ross Sea during the Early to Middle Miocene

    NASA Astrophysics Data System (ADS)

    Levy, Richard; Harwood, David; Florindo, Fabio; DeConto, Robert; Golledge, Nicholas; Hoffmann, Stefan; Kuhn, Gerhard; McKay, Robert; Naish, Timothy; Pollard, David; Sangiorgi, Francesca; von Eynatten, Hilmar

    2015-04-01

    A 1138-meter sediment core (AND-2A) recovered from the Southern McMurdo Sound sector of the Ross Sea comprises a near-continuous record of Antarctic climate and ice sheet variability through the Early to early Middle Miocene (20.2 to 14.5 million years ago), including an interval of inferred sustained global warmth known as the Miocene Climatic Optimum (MCO). The record preserves 55 sedimentary sequences that reflect cycles of glacial advance and retreat. A new analysis of proxy environmental data from the AND-2A core, and synthesis with regional geological information, show that the early to middle Miocene Antarctic climate ranged from cold polar conditions, similar to Antarctica during the Holocene, to those that characterise modern sub-polar environments. Four disconformities that punctuate the sedimentary sequence coincide with regionally mapped seismic discontinuities and reflect transient expansion of marine-based ice across the Ross Sea. The timing of these major marine-based ice sheet advances correlates with shifts in highly-resolved deep sea isotope records and major drops in eustatic sea-level indicating the global nature of these events. In contrast, three distinct intervals in the core indicate that this high latitude site was periodically influenced by an ice sheet margin that had retreated beyond the coastline. These relatively large-scale changes in climate and ice sheet extent occurred under atmospheric carbon dioxide concentrations that generally varied between 300 to 500 ppm. Therefore, our reconstructions suggest that Antarctica's climate and ice sheets were sensitive to modest changes in greenhouse gas forcing and support previous studies, which indicate that marine-based portions of the WAIS and EAIS can retreat under climatic conditions that were similar to those projected for our future under current levels of atmospheric CO2.

  19. Correlating Mediterranean shallow water deposits with global OligoceneMiocene stratigraphy and oceanic events?

    PubMed Central

    Reuter, Markus; Piller, Werner E.; Brandano, Marco; Harzhauser, Mathias

    2013-01-01

    Shallow-marine sediment records have the strong potential to display sensitive environmental changes in sedimentary geometries and skeletal content. However, the time resolution of most neritic carbonate records is not high enough to be compared with climatic events as recorded in the deep-sea sediment archives. In order to resolve the paleoceanographic and paleoclimatic changes during the OligoceneMiocene transition in the Mediterranean shallow water carbonate systems with the best possible time resolution, we re-evaluated the Decontra section on the Maiella Platform (central Apennines, Italy), which acts as a reference for the correlation of OligoceneMiocene shallow water deposits in the Mediterranean region. The 120-m-thick late Oligocenelate Miocene carbonate succession is composed of larger foraminiferal, bryozoan and corallinacean limestones interlayered with distinct planktonic foraminiferal carbonates representing a mostly outer neritic setting. Integrated multi-proxy and facies analyses indicate that CaCO3 and total organic carbon contents as well as gamma-ray display only local to regional processes on the carbonate platform and are not suited for stratigraphic correlation on a wider scale. In contrast, new biostratigraphic data correlate the Decontra stable carbon isotope record to the global deep-sea carbon isotope record. This links relative sea level fluctuations, which are reflected by facies and magnetic susceptibility changes, to third-order eustatic cycles. The new integrated bio-, chemo-, and sequence stratigraphic framework enables a more precise timing of environmental changes within the studied time interval and identifies Decontra as an important locality for correlating not only shallow and deep water sediments of the Mediterranean region but also on a global scale. PMID:25844021

  20. Miocene-Quaternary structural evolution of the Uyuni-Atacama region, Andes of Chile and Bolivia

    NASA Astrophysics Data System (ADS)

    Tibaldi, A.; Corazzato, C.; Rovida, A.

    2009-06-01

    We describe the Miocene-Quaternary geological-structural evolution of the region between the Salar de Uyuni and de Atacama, Andes of Chile and Bolivia. We recognized four main tectonic events based on fold geometry, fault kinematics and stratigraphic data. The oldest event, of Miocene age, is characterized by folding and reverse faulting of the sedimentary successions with an E-W direction of shortening in the northern part of the studied area and a WNW-ESE shortening in the southern part. The following two events, of Pliocene age, are characterized by lower shortening amounts; they occurred first by reverse faulting with a NW-SE-trending greatest principal stress ( σ1, computed with striated fault planes) and a vertical least principal stress ( σ3), followed by pervasive strike-slip faulting with the same NW-SE-trending σ1 and a horizontal NE-SW σ3. The fourth event, dating to the late Pliocene-Quaternary is characterized by normal faulting: the σ3 still trends NE-SW, whereas the intermediate principal stress σ2 exchanged with σ1. Volcanism accompanied both the contractional, transcurrent and extensional tectonic phases. The Mio-Pliocene compression appears directly linked to a rapid convergence and an apparently important coupling between the continental and oceanic plates. The E-W to WNW-ESE direction of shortening of the Miocene structures and the NW-SE σ1 of the Pliocene structures seem to be more linked to an intra-Andean re-orientation of structures following the WNW-directed absolute motion of the South-American Plate. The extensional deformations can be interpreted as related to gravity forces affecting the highest parts of the volcanic belt in a sort of asymmetrical (SW-ward) collapse of the belt.

  1. Late Miocene northward propagation of the northeast Pamir thrust system, northwest China

    NASA Astrophysics Data System (ADS)

    Thompson, Jessica A.; Burbank, Douglas W.; Li, Tao; Chen, Jie; Bookhagen, Bodo

    2015-03-01

    Piggyback basins on the margins of growing orogens commonly serve as sensitive recorders of the onset of thrust deformation and changes in source areas. The Bieertuokuoyi piggyback basin, located in the hanging wall of the Pamir Frontal Thrust, provides an unambiguous record of the outward growth of the northeast Pamir margin in northwest China from the Miocene through the Quaternary. To reconstruct the deformation along the margin, we synthesized structural mapping, stratigraphy, magnetostratigraphy, and cosmogenic burial dating of basin fill and growth strata. The Bieertuokuoyi basin records the initiation of the Pamir Frontal Thrust and the Takegai Thrust ~5-6 Ma, as well as clast provenance and paleocurrent changes resulting from the Pliocene-to-Recent uplift and exhumation of the Pamir to the south. Our results show that coeval deformation was accommodated on the major structures on the northeast Pamir margin throughout the Miocene to Recent. Furthermore, our data support a change in the regional kinematics around the Miocene-Pliocene boundary (~5-6 Ma). Rapid exhumation of NE Pamir extensional domes, coupled with cessation of the Kashgar-Yecheng Transfer System on the eastern margin of the Pamir, accelerated the outward propagation of the northeastern Pamir margin and the southward propagation of the Kashi-Atushi fold-and-thrust belt in the southern Tian Shan. This coeval deformation signifies the coupling of the Pamir and Tarim blocks and the transfer of shortening north to the Pamir frontal faults and across the quasi-rigid Tarim Basin to the southern Tian Shan Kashi-Atushi fold-and-thrust system.

  2. Atmosphere, ecology and evolution: what drove the Miocene expansion of C4 grasslands?

    PubMed Central

    Osborne, Colin P

    2008-01-01

    Grasses using the C4 photosynthetic pathway dominate today's savanna ecosystems and account for ∼20% of terrestrial carbon fixation. However, this dominant status was reached only recently, during a period of C4 grassland expansion in the Late Miocene and Early Pliocene (4–8 Myr ago). Declining atmospheric CO2 has long been considered the key driver of this event, but new geological evidence casts doubt on the idea, forcing a reconsideration of the environmental cues for C4 plant success. Here, I evaluate the current hypotheses and debate in this field, beginning with a discussion of the role of CO2 in the evolutionary origins, rather than expansion, of C4 grasses. Atmospheric CO2 starvation is a plausible selection agent for the C4 pathway, but a time gap of around 10 Myr remains between major decreases in CO2 during the Oligocene, and the earliest current evidence of C4 plants. An emerging ecological perspective explains the Miocene expansion of C4 grasslands via changes in climatic seasonality and the occurrence of fire. However, the climatic drivers of this event are debated and may vary among geographical regions. Uncertainty in these areas could be reduced significantly by new directions in ecological research, especially the discovery that grass species richness along rainfall gradients shows contrasting patterns in different C4 clades. By re-evaluating a published data set, I show that increasing seasonality of rainfall is linked to changes in the relative abundance of the major C4 grass clades Paniceae and Andropogoneae. I propose that the explicit inclusion of these ecological patterns would significantly strengthen climate change hypotheses of Miocene C4 grassland expansion. Critically, they allow a new series of testable predictions to be made about the fossil record. Synthesis. This paper offers a novel framework for integrating modern ecological patterns into theories about the geological history of C4 plants. PMID:18784799

  3. Paleomagnetism of the Miocene dikes in Bare Mountain, southwest Nevada: Implications for regional tectonics

    SciTech Connect

    Zhang, Y.; Gillett, S.L.; Karlin, R.E.; Schweickert, R.A. . Dept. of Geological Sciences)

    1993-04-01

    Paleomagnetic studies of N-striking Miocene quartz latite dikes (13.9 Ma), within Proterozoic and Paleozoic sedimentary rocks of Bare Mountain, have been conducted in an effort to determine the sense of post-middle Miocene tectonic tilting and rotation in the Bare Mountain region. A total of 56 oriented samples of dikes and wallrocks were collected from Tarantula Canyon (TC) and south of Joshua Hollow (JH), where the dikes intruded N-dipping Mississippian-Devonian limestone beds. Progressive thermal demagnetization and principal component analyses reveal a stable high temperature component of remanent magnetization that is carried by magnetite or hematite in different samples. Petrographic investigations, combined with thermal demagnetization analysis, indicate that magnetite is a primary phase and that hematite is secondary. Hematitic alteration in both wallrocks and dikes is probably hydrothermal following intrusion as the mean direction of both minerals overlap. The in situ mean magnetization directions from all dikes exhibit negative inclinations that correspond to a Tertiary reversed field. The data indicate that magnetization acquisition in the wallrocks and dikes postdates tilting of the beds and the no major remagnetization event has occurred since the intrusion. The results from TC imply that there has been no significant rotation of the northeast part of Bare Mountain since [minus]14 Ma. The authors further suggest that the E-W structural trends of Proterozoic and Paleozoic rocks at Bare Mountain are older than the middle Miocene dikes. Paleomagnetic data from dikes of JH show steeper inclinations and westerly declinations compared to the dike of TC. There are two interpretations to explain the differences: The dikes may have formed at different times in the same magmatic event and the directional differences are due to secular variation. Alternatively, the dikes at JH were tilted slightly to the north around a sub-horizontal axis.

  4. Late Miocene-Pleistocene Stability of upper Ferrar Glacier, Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Staiger, J. W.; Marchant, D. R.; Schaefer, J. M.; Johnson, J. V.; Oberholzer, P.

    2005-12-01

    Vernier Valley (78o S, 161o E) opens onto a peripheral lobe of upper Ferrar glacier in the Dry Valleys of southern Victoria Land, Antarctica. The areal distribution of Ferrar drifts, along with a relative and numerical chronology afforded by surface-weathering characteristics and 3He - 21Ne exposure-age data, are used to reconstruct the Late Miocene-to-Pleistocene history of upper Ferrar Glacier. Applying a modest erosion rate correction of 10 cm Ma-1, our results show that the glacial record provided by Ferrar (1, 2, 3, and 4) drifts in Vernier Valley extends back into late Miocene time. Cosmogenic ages for clasts on the modern, ice-cored Ferrar 1 moraine suggest that nuclide inheritance is negligible. The development of weathering pits and desert varnish on surface cobbles varies linearly with cosmogenic age. Ice-surface profiles reconstructed from the moraine distribution and exposure-ages of boulders atop the moraines indicate that the ice-surface elevation of upper Ferrar Glacier has lowered roughly 50 m throughout the Quaternary Period and roughly 125 m since late Miocene time. Conversely, during MIS 2, the ice-surface elevation of upper Ferrar Glacier was likely no higher than today and may have been below modern levels. The moraine now forming through ice sublimation and debris accumulation at the modern, cold-based Ferrar Glacier margin is texturally similar to older drifts up-valley. The slow recession of cold-based glacier ice (and without surface melting ablation zones) in lower Vernier Valley implies enduring cold-desert conditions, much like those of today, for at least the last ~6.5 Ma. Results from a 2-D glacier flow-band model also demonstrate that upper Ferrar Glacier lacked basal-melting zones even during the Pliocene optimum. The overall stability of this glacial system has implications for the response of ice in this sector of Antarctica to future polar warming.

  5. Provenance of the upper Miocene-Pliocene red clay deposits of the Chinese Loess Plateau

    NASA Astrophysics Data System (ADS)

    Nie, J.; Stevens, T.; Song, Y.; Moeller, A.; Stockli, D. F.; Horton, B. K.; Fang, X.

    2013-12-01

    A clear understanding of the provenance of late Cenozoic Chinese loess and the underlying red-clay deposits will shed light on the history and mechanisms of Asian aridification. Although much progress has been made in understanding the source of Quaternary loess in the Chinese Loess Plateau (CLP), the provenance of the underlying upper Miocene-Pliocene red-clay sequence is largely unknown. Here we present a provenance history of the red-clay sequence based on zircon U-Pb ages from the central CLP. Non-metric multi-dimensional scaling (MDS) statistical analyses of the U-Pb age populations allow clear identification of sediment source trends and reveal that the red-clay deposited during 5.5-3 Ma has a western Kunlun provenance, suggesting that the distal Taklimakan desert was the principal source and that dusts were transported to the CLP via westerly winds. By contrast, late Quaternary loess appears to have source signatures from more proximal regions such as NE Tibet, West Mu Us desert, and Qaidam desert, as well as the Yellow River and distal Taklimakan desert, suggesting that dusts were transported to the CLP via winter monsoon, the Yellow River, and westerly winds. Furthermore, MDS analyses reveal that the East Mu Us desert is less likely to be major source region for the CLP during the past 8 Ma. These results demonstrate that 1) Asian desertification has a pattern of eastward expansion since the late Miocene and 2) the provenance shift from the upper Miocene-Pliocene red-clay to the late Quaternary loess is associated with formation of the proximal deserts and Yellow River.

  6. Simulating the climate impact of Large Igneous Provinces: A mid-Miocene case-study

    NASA Astrophysics Data System (ADS)

    Armstrong McKay, David I.; Tyrrell, Toby; Wilson, Paul A.; Foster, Gavin L.; Müller, Simon A.

    2013-04-01

    Large Igneous Provinces (LIPs) can result in significant degassing of mantle-derived CO2 into the ocean-atmosphere system, but only the largest LIPs are considered to have had a significant impact on global climate. However, some smaller LIPs also coincide with times of global warmth and carbon cycle perturbations. Here we use biogeochemical box models to investigate the possibility of one such minor LIP, the Columbia River Basalts (CRB), warming climate during the mid-Miocene. An advantage of studying this fairly recent event is the more rigorous model-data comparison made possible by the relative wealth of palaeorecords. Comparing our model results to reconstructions of mid-Miocene carbonate compensation depth, benthic foraminifera δ13C and pCO2 suggests an emissions scenario of 2000-4000 Pg C between ~16.2 and 15.8 Ma fits the palaeorecords best, though additional mechanisms are required to match the CCD reconstruction after this. This emission range is nearly an order of magnitude greater than estimates for extrusive basalt degassing alone, but is within the estimated range when including degassing from intrusive and underplated material or the potential incorporation of pyroxenite-rich oceanic crust into the CRB's magma supply. When including these extra CO2 sources we conclude that the CRB could have played a significant role in the mid-Miocene Climatic Optimum if the additional emissions actually occurred. This can be extrapolated to other LIPs and we consider whether they could have also had a greater impact than currently accepted.

  7. A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia.

    PubMed

    Rybczynski, Natalia; Dawson, Mary R; Tedford, Richard H

    2009-04-23

    Modern pinnipeds (seals, sea lions and the walrus) are semi-aquatic, generally marine carnivores the limbs of which have been modified into flippers. Recent phylogenetic studies using morphological and molecular evidence support pinniped monophyly, and suggest a sister relationship with ursoids (for example bears) or musteloids (the clade that includes skunks, badgers, weasels and otters). Although the position of pinnipeds within modern carnivores appears moderately well resolved, fossil evidence of the morphological steps leading from a terrestrial ancestor to the modern marine forms has been weak or contentious. The earliest well-represented fossil pinniped is Enaliarctos, a marine form with flippers, which had appeared on the northwestern shores of North America by the early Miocene epoch. Here we report the discovery of a nearly complete skeleton of a new semi-aquatic carnivore from an early Miocene lake deposit in Nunavut, Canada, that represents a morphological link in early pinniped evolution. The new taxon retains a long tail and the proportions of its fore- and hindlimbs are more similar to those of modern terrestrial carnivores than to modern pinnipeds. Morphological traits indicative of semi-aquatic adaptation include a forelimb with a prominent deltopectoral ridge on the humerus, a posterodorsally expanded scapula, a pelvis with relatively short ilium, a shortened femur and flattened phalanges, suggestive of webbing. The new fossil shows evidence of pinniped affinities and similarities to the early Oligocene Amphicticeps from Asia and the late Oligocene and Miocene Potamotherium from Europe. The discovery suggests that the evolution of pinnipeds included a freshwater transitional phase, and may support the hypothesis that the Arctic was an early centre of pinniped evolution. PMID:19396145

  8. Early and Middle Miocene Antarctic Ice Sheet Behavior: results from the ANDRILL SMS Project

    NASA Astrophysics Data System (ADS)

    Harwood, D. M.; Florindo, F.; Levy, R. H.; SMS Project Science Team http://andrill. org/projects/sms/team. html

    2011-12-01

    A 1138-meter sediment drillcore (AND-2A) recovered by the SMS Project of the ANDRILL Program from the McMurdo Sound sector of the western Ross Sea contains a near-continuous, coastal record of Antarctic climate and ice sheet variability through the early Miocene (20.2 to ~14.5 million years ago), including an interval of global warmth known as the Mid-Miocene Climatic Optimum (MMCO). The AND-2A drillcore was deposited in the subsiding Victoria Land Basin, during a period of relatively steady thermal subsidence, on the coastal plain and continental shelf seaward of the rising Transantarctic Mountains. Analysis of this drillcore indicates prolonged periods when the ice sheet margin remained retreated from the coastline, and other periods when the ice sheet was highly dynamic, advancing and retreating on orbital timescales. It preserves a record of the pace and scale of climate and ice sheet variation, and allows for the evaluation of climate sensitivity through data and numerical modeling integration. Stratigraphic sequences and facies interpretations reveal a cyclical history of climate changes, glacial advance and retreat cycles. Under warm, equable climate conditions recorded in a variety of climate indicators, the behavior of the early Miocene Antarctic ice sheet evident in the AND-2A core was varied, ranging between two modes: (1) persistent absence/retreat of low elevation ice sheets from coastal regions, and (2) periods of dynamic but subdued fluctuations with the ice margin of larger volume ice sheets entering across the coastal zone. The glacial regime varied from sub-polar with significant meltwater through proximal and distal high-latitude temperate glacial conditions with abundant meltwater. A well-developed chronostratigraphic framework allows for the comparison of events recognized in this drillcore with events identified in distal proxy records from deep-sea stable isotope studies. This dynamic response of Antarctic climate during times when CO2 levels were only slightly higher than today, and greenhouse gas forcing was relatively modest, presents a serious challenge for numerical climate and ice sheet models that generally fail to produce the range of variability at the relatively low levels of atmospheric CO2 presumed to have existed in the Miocene.

  9. Miocene ostracod (Crustacea) biostratigraphy of the upper Amazon Basin and evolution of the genus Cyprideis

    NASA Astrophysics Data System (ADS)

    Muoz-Torres, F. A.; Whatley, R. C.; Harten, D. van

    2006-03-01

    The Ostracoda in this study come from an area in the Western Amazon river region shared by Peru, Colombia, and Brazil. Fauna was recovered from 125 samples collected at 26 outcrop localities of the Pebas Formation. Five ostracod zones are proposed and referred mainly to the Middle Miocene. The zonation is based on the stratigraphical distribution of 21 endemic species of the euryhaline genus Cyprideis, probably the largest brackish-water ostracod evolutionary radiation of the American Neogene. This study illustrates that Ostracoda can constitute a useful biostratigraphical tool in such environments as those obtained in the Neogene of the upper Amazon Basin.

  10. Depositional setting and hydrocarbon source potential of the Miocene Gulf of Suez syn-rift evaporites

    SciTech Connect

    Richardson, M.; Arthur, M.A.; Quinn, J.S.; Whelan, J.K.; Katz, B.J. )

    1988-08-01

    The Red Sea rift basin and its northern continuation, the Gulf of Suez, has experienced continuous deposition of marine evaporites throughout much of its development from the early Miocene to the Pliocene resulting in the accumulation of up to 5 km of evaporite strata in the rift. In this paper, the geologic history of these evaporites are discussed, along with their petroleum source rock potential. The authors hypothesize that rapid deposition of organic matter occurred during episodic storms and freshening events in which a less saline surface layer developed.

  11. A molecular stable carbon isotope study of organic matter in immature Miocene Monterey sediments, Pismo basin

    NASA Astrophysics Data System (ADS)

    Schouten, Stefan; Schoell, Martin; Rijpstra, W. Irene C.; Sinninghe Damst, Jaap S.; de Leeuw, Jan W.

    1997-05-01

    The 300 m section of the Miocene Monterey Formation outcropping at Shell Beach (Pismo basin; ca. 15-11 Ma) is composed of calcareous phosphatic (15.1-14.5 Ma) and siliceous facies (14.5-11.0 Ma). An objective of this paper is to document lateral paleoenvironmental changes in the Miocene Moneterey Formation by comparing the Shell Beach (SB) profile with the Naples Beach (NB) section in the Santa Barbara-Ventura basin (Schouten et al., 1997) which is 80 km to the south. Eight samples (one sample representing, on average, a time period of ca. 2000 y) from this section were analyzed for variations of extractable biomarkers and their carbon isotopic signatures as indicators for paleoenvironmental change during the Miocene. Saturated hydrocarbons present include 28,30-dinorhopane, phytane, n-alkanes (C 17sbnd C 31), lycopane, and 17?,21?(H)-homohopane. The biomarkers released after desulfurization of the polar fractions predominantly consist of phytane, 2,6,10,14-tetramethyl-7-(3-methylpentyl)pentadecane, C 17sbnd C 31n-alkanes, regular 5?- and 5?-steranes, dinosteranes, and (22R)-17?,21?(H)-pentakishomohopane. Steranes have similar carbon isotopic compositions (-25 to -27) throughout the section and are isotopically similar at both sites, indicating laterally similar and vertically stable environmental conditions for algae living in the upper part of the photic zone. Free and S-bound n-alkanes at SB mainly originate from marine organisms and not from terrestrial sources as in the NB section. S-bound pentakishomohopane is ca. 1-4 depleted compared to the steranes and is thought to be derived from the deeper water dwelling cyanobacteria. These findings are consistent with stable carbon isotopic data obtained for these compounds from Middle Miocene Monterey sediments at Naples Beach and indicates similar environmental conditions in the depositional environments of the Santa Barbara-Ventura and the Pismo basin. S-bound highly branched isoprenoids have, at both sites, different isotopic compositions indicating the presence of different diatom species, special growth conditions, or different bloom periods in the Pismo basin. The carbon isotopic composition of 28,30-dinorhopane shifts to more depleted values up section, suggesting that the dinorhopane-synthesizing organism or organisms live on CO 2, which is isotopically influenced by methane production and oxidation. The C 31 hopane is enriched by 1-4 in 13C compared to other hopanes and steranes. Specific bacteria, possibly heterotrophs, may have been the organisms producing this compound.

  12. Biostratigraphy and paleoenvironment of Miocene- Pliocene hemipelagic limestone: Kingshill Seaway, St. Croix, US Virgin Islands.

    USGS Publications Warehouse

    Lidz, B.H.

    1982-01-01

    The Kingshill Limestone and younger carbonate rocks constitute the central portion of St. Croix, forming the remains of an ancient seaway that was flanked by emergent highlands. The seaway has been filled with thick epipelagic sediments alternating with carbonate turbidites and ash falls and capped with shallow-water reefal and terrigenous debris. Planktonic foraminifera indicate that ages of these rocks range sequentially in a SW direction from the middle Miocene to lower Pliocene. Scanning electron micrographs illustrate 42 species and subspecies of pelagic foraminifera and 13 selected paleoenvironmentally significant aberrant forms.-from Author

  13. Miocene oceanographic changes of the western equatorial Atlantic (Ceara Rise) based on calcareous dinoflagellate cysts

    NASA Astrophysics Data System (ADS)

    Heinrich, S.; Zonneveld, K. A. F.; Willems, H.

    2010-09-01

    The middle- and upper Miocene represent a time-interval of major changes in palaeoceanography that favoured the cooling of the climate and culminated in the Northern Hemisphere Glaciation (NHG). The basis for the development of the modern deepwater circulation pattern, e.g. thermohaline circulation, was hereby established. Tectonic events played a key role in the progressing Miocene oceanography, such as the narrowing of the Panama gateway (e.g. Duque-Caro 1990) and the possible linked changes in North Atlantic Deep Water formation (Lear et al. 2003). However, the complex interaction between the closing of the Panama Gateway, the development of NADW, and thus the oceanographic progression towards our present day circulation is far from being fully understood. We want to improve the understanding of these processes by establishing a detailed palaeoceanographic reconstruction of the western equatorial Atlantic Ocean on the basis of calcareous dinoflagellate cyst (dinocyst) associations. Within this study, we investigated sediment samples from ODP Site 926A by defining the calcareous dinocyst assemblage. Site 926A is located at the southwestern flank of the Ceara Rise, an area of highest sensitivity to global deep water circulation changes. At about 12 Ma, when NADW production increased (e.g. Wright et al. 1992), we see a distinct increase in the absolute abundances of the calcareous dinocysts. This might be related to enhanced productivity or to better carbonate preservation. At 11.3 Ma, Leonella granifera, a species known to be strongly related to terrestrial input occurs. This could be a signal for the initiation of the Amazon River as a transcontinental river with the development of the Amazon fan (11.8 - 11.3 Ma; Figueiredo et al. 2009) in relation to Andean tectonism. References: Duque-Caro, H. (1990): Neogene stratigraphy, paleoceanography and palebiology in Northwest South America and the evolution of the Panama Seaway. Palaeogeography, Palaeoclimatology, Palaeoecology 77, 203-234. Figueiredo, J., Hoorn, C., van der Veen, P., Soares, E. (2009): Late Miocene onset of the Amazon River and the Amazon deep-sea fan: Evidence from the Foz do Amazonas Basin. Geology; v. 37, no. 7; p. 619-622. Lear, C.H., Rosenthal, Y., Wright, J.D. (2003): The closing of a seaway: ocean water masses and global climate change. Earth and Planetary Science Letters 210, 425-436. Wright, J.D., Miller, K.G., Fairbanks, R.G. (1992): Early and middle Miocene stable isotopes: implications for deepwater circulation and climate. Paloceanography 7(3): 357-398.

  14. Miocene oceanographic changes of the western equatorial Atlantic (Ceara Rise) based on calcareous dinoflagellate cysts

    NASA Astrophysics Data System (ADS)

    Heinrich, Sonja; Zonneveld, Karin A. F.; Willems, Helmut

    2010-05-01

    The middle- and upper Miocene represent a time-interval of major changes in palaeoclimate leading to global cooling forming the precursor of the onset of Northern Hemisphere Glaciations (NHG). These climate changes are thought to be strongly controlled by oceanographic modifications although the nature of the relationship between ocean and climate change is far from clear. It has for instance been observed that in this time interval the modern deepwater circulation system; the thermohaline circulation was established. It is thought that tectonic events, such as the narrowing of the Panama gateway, played a key role in the progressing of these Miocene oceanographic changes (e.g. Duque-Caro 1990; Lear et al. 2003). However, the complex interaction between the closing of the Panama Gateway, the development of NADW, and thus the oceanographic progression towards our present day circulation is far from being fully understood. A key region to study these interactions is the Caribbean region, notably the Ceara Rise since it is an area of highest sensitivity to global deep water circulation changes. Here we intent to improve the understanding of these processes by establishing a detailed palaeoceanographic reconstruction of the western equatorial Atlantic Ocean on the basis of calcareous dinoflagellate cyst (dinocyst) associations. For this, we investigated sediment samples from ODP Site 926A by defining the calcareous dinocyst assemblage. Site 926A is located at the southwestern flank of the Ceara Rise, an area of highest sensitivity to global deep water circulation changes. At about 11 Ma, we see a distinct increase in the absolute abundances of the calcareous dinocysts suggesting enhanced productivity and better carbonate preservation that can be related to the intensification of NADW formation (Woodruff & Savin 1989). At 11.3 Ma, Leonella granifera, a species known to be strongly related to terrestrial input increases. This could be a signal for the initiation of the Amazon River as a transcontinental river (11.8 - 11.3 Ma; Figueiredo et al. 2009) in relation to Andean tectonism. References: Duque-Caro, H. (1990): Neogene stratigraphy, paleoceanography and palebiology in Northwest South America and the evolution of the Panama Seaway. Palaeogeography, Palaeoclimatology, Palaeoecology 77, 203-234. Figueiredo, J., Hoorn, C., van der Veen, P., Soares, E. (2009): Late Miocene onset of the Amazon River and the Amazon deep-sea fan: Evidence from the Foz do Amazonas Basin. Geology; v. 37, no. 7; p. 619 - 622. Lear, C.H., Rosenthal, Y., Wright, J.D. (2003): The closing of a seaway: ocean water masses and global climate change. Earth and Planetary Science Letters 210, 425-436. Woodruff, F., Savin, S.M. (1989): Miocene deepwater oceanography. Paloceanography 4, 87-140.

  15. New constrains on the thermal history of the Miocene Jarando basin (Southern Serbia)

    NASA Astrophysics Data System (ADS)

    Andri?, Nevena; ivoti?, Dragana; Fgenschuh, Bernhard; Cvetkovi?, Vladica

    2013-04-01

    The Jarando basin, located in the internal Dinarides, formed in the course of the Miocene extension affecting the whole Alpine-Carpathian-Dinaride system (Schmid et al., 2008). In the study area Miocene extension led to the formation of a core-complex in the Kopaonik area (Schefer et al., 2011) with the Jarando basin located in the hanging wall of the detachment fault. The Jarando basin is characterized by the presence of bituminous coals, whereas in the other intramontane basins in Serbia coalification did not exceed the subbituminous stage within the same stratigraphic level. Furthermore, the basin hosts boron mineralizations (borates and howlite) and a magnesite deposit, which again implies elevated temperatures. This thermal overprint is possibly due to post-magmatic activity related to the emplacement of Oligocene I-type Kopaonik and Miocene S-type Polumir granitoid (Schefer et al., 2011.). This research project is aimed at providing new information about the thermal history of the Jarando basin. Fifteen core samples from three boreholes and 10 samples from the surrounding outcrops were processed for apatite fission-track analysis. Additionally, vitrinite reflectance was measured for 11 core samples of shales from one borehole and 5 samples of coal from an underground mine. VR data of Early to Middle Miocene sediments reveal a strong post-depositional overprint. Values increase with the depth from 0.66-0.79% to 0.83-0.90%. Thus organic matter reached the bituminous stage and experienced temperatures of around 110-120?C (Barker and Pawlewicz, 1994). FT single grain ages for apatite scatter between 45 Ma to 10 Ma with a general trend towards younger ages with depth. Both, the spread in single grain ages together with the bimodal track lengths distribution clearly point to partial annealing of the detrital apatites. With the temperature given from the VR values the partial annealing points to a rather short-lived thermal event. This is assisted by thermal modelling of our fission track data indicating that maximum temperatures of <120C around 15-12 Ma. We correlate the thermal event with the extension and core-complex formation followed by the syn-extensional intrusion of the Polumir granite. Later cooling from 10 Ma onwards is related to basin inversion and erosion.

  16. Global climate and monsoons response to orbital forcing in the Late Miocene

    NASA Astrophysics Data System (ADS)

    Marzocchi, A.; Lunt, D. J.; Flecker, R.; Farnsworth, A.; Bradshaw, C.

    2014-12-01

    Global climate during the Late Miocene (11.61-5.33 Ma) is thought to have been generally warmer and wetter than at present day. The Northern Hemisphere was characterised by nearly ice-free conditions (with respect to the extent of the Greenland ice sheet) and some of the main marine gateways were undergoing opening or closure (e.g. Central American gateway, Bering Strait, and Indonesian Throughflow). Vegetation distribution was also generally more extensive than it is today, both at high and low latitudes. There is geological evidence of orbitally-forced cyclicity in sedimentary sections throughout the globe, especially in marginal basins such as the Mediterranean Sea. In the Late Miocene the entire North African catchment drained in the Eastern Mediterranean, constituting the main fresh water input into the basin, regulated by the North African monsoon. In addition, the Tibetan Plateau underwent substantial uplift throughout this time period, which strengthened the Asian monsoon system. The Late Miocene therefore represents an ideal scenario to investigate the impact of orbital forcing on the North African and Asian monsoon systems, the establishment of their teleconnections, and the associated vegetation changes. There still is considerable uncertainty in the reconstructed atmospheric CO2 levels for this time period, due to the patchy distribution (both spatially and temporally) of the available proxy record. Hence, we also explore the sensitivity of global climate to changing CO2 levels with different orbital configurations. We carried out a new series of 22 fully coupled atmosphere-ocean-vegetation numerical simulations, run at evenly spaced intervals (1kyr) through a full late Miocene precession cycle (~6.5 Ma), using a full-complexity general circulation model (HadCM3L). These model results show substantial changes to sea surface temperatures and regional atmospheric circulation on sub-precessional time scales. This triggers responses in the North African and Asian monsoon systems, which modify their timing, onset, intensity and seasonality. This has important consequences for vegetation distribution, with highly intensified precipitation patterns at times of minimum precession (maximum insolation) resulting in a greening of both the Sahel and Indian regions.

  17. Two flat-backed polydesmidan millipedes from the Miocene Chiapas-amber Lagersttte, Mexico.

    PubMed

    Riquelme, Francisco; Hernndez-Patricio, Miguel; Martnez-Dvalos, Arnulfo; Rodrguez-Villafuerte, Mercedes; Montejo-Cruz, Maira; Alvarado-Ortega, Jess; Ruvalcaba-Sil, Jos L; Ziga-Mijangos, Luis

    2014-01-01

    Two species of fossil polydesmidan millipedes (Diplopoda: Polydesmida) embedded in amber are described from Miocene strata near Simojovel, in the Chiapas Highlands, Mexico. Maatidesmus paachtun gen. et sp. nov., placed into Chelodesmidae Cook, 1895, and Anbarrhacus adamantis gen. et sp. nov., assigned in the family Platyrhacidae Pocock, 1895. Morphological data from fossil specimens have been recovered using 3D X-ray micro-computed tomography and regular to infrared-reflected microscopy. Both fossil species are recognizable as new primarily but not exclusively, by collum margin modification and remarkable paranotal and metatergite dorsal sculpture. PMID:25162220

  18. Incremental growth and mineralogy of Pannonian (Late Miocene) sciaenid otoliths: paleoecological implications

    NASA Astrophysics Data System (ADS)

    Kern, Zoltn; Kzmr, Mikls; Bosnakoff, Mariann; Vczi, Tams; Bajnczi, Bernadett; Katona, Lajos

    2012-04-01

    Ontogenetic age and body dimensions were studied on three extremely well-preserved sciaenid fish otoliths from sublittoral marls of Lake Pannon from Doba, Bakony Mts, Hungary. Macroscopic and microscopic observations offered clear evidence for the preservation of the genuine structural characteristics, for instance the bipartite incremental features. Ontogenetic ages were assigned for the three specimens as 16, 7 and 6 years by counting the annuli of the sagittae. Analytical results prove that the original aragonitic mineralogy has been preserved making them, and probably other Late Miocene teleost fossils, suitable for future microchemical analysis to reconstruct the past physicochemical environment.

  19. Geology of a new Late Miocene mammal locality in central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Kazanci, Nizamettin; Sen, Sevket; Seyitoglu, Gürol; de Bonis, Louis; Bouvrain, Geneviève; Araz, Hakan; Varol, Baki; Karadenizli, Levent

    1999-10-01

    The new mammal locality of Akkasdagi yielded a rich fauna dated as Middle Turolian. It is situated in the southern part of the Çankiri-Çorum Basin in central Anatolia. In the Akkasdagi area, the sedimentary deposits, mapped as the Kizilirmak Formation, consist of tuffs and lacustrine limestones intercalated with clastic deposits, whilst in its type section situated to the north near Kizilirmak town, this formation is mainly formed of fluviatile deposits. Facies distribution and geological observations led to conclude that during the Miocene, depositional centers migrated from the north to the south of this basin.

  20. Mid-Miocene Silicic Volcanism of the Three Fingers - Mahogany Mountain Area, SE Oregon - Revisited

    NASA Astrophysics Data System (ADS)

    Marcy, P.; Streck, M. J.; Ferns, M.

    2013-12-01

    Earlier work identified two adjacent caldera systems, the Mahogany Mountain and Three Fingers calderas as the centerpiece of voluminous rhyolitic volcanism on the eastern margin of the Oregon-Idaho graben during the mid-Miocene. Silicic volcanism of Three Fingers-Mahogany Mtn. area is part of the Lake Owyhee volcanic field, Oregon and belongs to widespread rhyolites associated with the Columbia River Basalt province. Here we revisit field evidence and establish relationships between intra-caldera units of Three Fingers and Mahogany Mtn. calderas, and their outflow facies, the tuffs of Spring Creek and Leslie Gulch. In addition, we assess the distribution of entrained mafic clasts and their often anomalously high, nearly ore-grade concentrations of rare earth elements (REE). Previous mapping identified two groups of intra-caldera rhyolite units: 1) intra-caldera tuffs of Spring Creek and Leslie Gulch and 2) younger rhyolite lavas (Trp) within Three Fingers Caldera and cross-cutting rhyolite dikes within the core of Mahogany Mtn. Caldera. Our mapping determines that devitrified Trp of Three Fingers area is equivalent to surrounding often glassy, pumiceous to dense or brecciated rhyolite flows mapped before as intra-caldera tuff of Spring Creek, and all are compositionally indistinguishable from cross-cutting dikes within Mahogany Mtn. Reinterpreted rhyolites of Three Fingers Caldera lack vitroclastic textures and are geochemically distinct from outflow tuff of Spring Creek which in turn can be distinguished from the tuff of Leslie Gulch. Outflow tuff of Spring Creek is Fe-rich, low silica rhyolite (~74 wt.% SiO2, 3 wt.% FeO, ~1600 ppm Ba) as compared to less Fe rich, high-silica rhyolite (~77 wt.% SiO2, 2 wt.% FeO, ~200 ppm Ba) of intra-caldera units. Outflow tuff of Leslie Gulch is also high-silica rhyolite but Ba rich (~1500 ppm). We interpret the investigated Three Fingers area as a rhyolite dome field, erupting subsequent to caldera collapse. There, abundant post-collapse rhyolite volcanism resulted in a complex stratigraphic overlap of rhyolite flows and clastic debris issued from closely-spaced domes. The predominance of high-standing dome interiors reflects the more resistant nature of dense devitrified rhyolite as compared to pumiceous, glassy, or brecciated rhyolite. New 40Ar/39Ar data reveal intra-caldera rhyolites and outflow tuff of Spring Creek to be indistinguishable at 15.64 × 0.08 Ma yet field evidence indicates eruption of post-caldera rhyolites occurred after sedimentation within the caldera. The existence of two outflow tuff units suggests two collapse structures and ages indicate the Mahogany Mtn. Caldera preceded the younger rhyolites by ~200,000 years. Mafic clasts present in dense glassy or porous intra-caldera rhyolites of Three Fingers are reworked fragments of preexisting lava flows that were entrained by subsequent eruptions. Ore-grade REE enrichment of over 2400 ppm Nd in these clasts is likely facilitated by mobilization of REE from earlier rhyolites during renewed rhyolite magmatism and subsequent deposition.

  1. Miocene woods from the Qaidam Basin on northern Qinghai-Tibet Plateau with implications for paleoenvironmental change

    NASA Astrophysics Data System (ADS)

    Cheng, Ye-Ming; Yang, Xiao-Nan

    2016-02-01

    The Qaidam Basin with the most complete Cenozoic sedimentary preservation in northern Qinghai-Tibet Plateau is a key area for studying uplift and environmental change of the plateau. Three types of woods, Ulmus (Ulmaceae), Leguminosae (?) (angiosperm) and Cupressaceae (gymnosperm) were recognized from the large-scale preservation of fossil woods in late Miocene Shang Youshashan Formation in northern Qaidam Basin on the Qinghai-Tibet Plateau. Both investigations of their Nearest Living Relatives (NLRs) and previous grassland mammal evidences suggest that there have been temperate deciduous broad-leaved forest and needle-leaved forest with grass in northern Qaidam Basin during the late Miocene in contrast to the desert vegetation found there nowadays. The presence of the ancient forest steppe further implies that the southern part of the plateau used to be adequately low, so that the Indian and East Asian monsoons could approach the northern area and to accommodate the vegetation in late Miocene.

  2. Subtropical forest expansion in the middle Miocene Europe: pCO2, Antarctic ice volume and oceanic changes

    NASA Astrophysics Data System (ADS)

    Hamon, N.; Sepulchre, P.; Donnadieu, Y.; Ramstein, G.

    2012-04-01

    The middle Miocene is a crucial period for ape's evolution and corresponds to their appearance in Europe. The dispersion of apes was made possible by tectonic changes and the expansion of their habitat, which is tropical to subtropical forest, in Europe. The context in which the Middle Miocene Climatic Optimum occurred still lacks constraints in terms of atmospheric pCO2 and Antarctic ice sheet volume and extent. Using the coupled atmosphere - ocean GCM FOAM and the dynamic vegetation model CARAIB, we investigate the sensitivity of Miocene climate and vegetation to pCO2 levels and Antarctic ice sheet configurations. We performed sensitivity experiments to test the impact of varying pCO2 (280 ppmv, 560 ppmv and 700 ppmv) and Antarctic albedo (ice and tundra) on the European vegetation during the Middle Miocene Climatic Optimum. Our results indicate that higher than present pCO2 is necessary to simulate subtropical forest in Western and Central Europe during the middle Miocene. However, a threshold between 560 and 700 ppmv makes subtropical forest partly collapse, which is due to colder and slightly dryer conditions in Europe. This can be explained by the fact that CO2-induced warming of the high latitudes strongly reduces North Atlantic Deep Water formation, therefore reducing the heat transport in this region. Moreover, the albedo change over Antarctica, which is directly linked to the ice surface, leads to further warming in Europe, and the expansion of subtropical forest. These results suggest that a small East Antarctic Ice Sheet (25% of present-day ice volume) together with higher than present pCO2 are in better agreement with available European middle Miocene data.

  3. Relationships of seismic amplitudes and gas content of the Miocene Amos Sand, Mobile Bay area, offshore Alabama

    SciTech Connect

    Reif, L.T. ); Kinsland, G.L. )

    1993-09-01

    Mobil Oil Company has collected three-dimensional (3-D) seismic data over Mary Ann field in the Mobile Bay area, Alabama. Although the survey was designed and collected so as to image the deeper Norphlet Sands, amplitude anomalies in the image of the shallow Miocene Amos Sand are evident. Relationships are developed between the seismic amplitudes and net feet of gas in the Amos Sand at the few existing wells. These relationships are used to predict net feet of gas everywhere in the area of the seismic survey. The result is a contoured map of net feet of gas in the Miocene Amos Sand in Mary Ann field.

  4. Age and stratigraphic context of Pliopithecus and associated fauna from Miocene sedimentary strata at Damiao, Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Kaakinen, Anu; Abdul Aziz, Hayfaa; Passey, Benjamin H.; Zhang, Zhaoqun; Liu, Liping; Salminen, Johanna; Wang, Lihua; Krijgsman, Wout; Fortelius, Mikael

    2015-03-01

    Since the discovery of mammalian fossils in Central Inner Mongolia in the beginning of the 20th century, this area has produced a rich and diverse record of Miocene faunas. Nevertheless, the stratigraphy has remained poorly constrained owing to scattered faunal horizons and lack of continuous vertical exposures. Consequently, most age estimates of these Miocene sites are based on paleontological evidence alone, with very few sites having been dated independently. Our field investigations in Damiao, in Siziwang Qi, Inner Mongolia have yielded more than 30 new fossiliferous localities from three horizons, including a pliopithecid fauna. This study presents the litho-, bio- and magnetostratigraphy of the Damiao area and provides age estimates for the three fossil-bearing horizons. The sedimentary sequence is interpreted as the remains of a fluvial system comprising channels, subaerially exposed floodplains and floodbasin environments. The two local stratigraphic sections measured and sampled for paleomagnetic analysis coincide with species-rich vertebrate fossil localities. The paleomagnetic results and faunal evidence suggest a correlation of lowermost fossil horizon (DM16) producing relatively rich small mammal assemblage to the early Miocene chron C6Ar or C6An.1r, roughly in 20-21 Ma age range. The pliopithecid locality level (DM01) represents latest middle Miocene and has an age estimate of about 12.1 Ma while the youngest localities (DM02) with cervoids and abundant and diverse small mammal fauna represents the earliest late Miocene with an age estimate of about 11.6 Ma. Our magnetostratigraphic results confirm that the Damiao strata constitute one of the best sequences in Inner Mongolia with early, middle and late Miocene mammalian faunas in stratigraphic superposition. The results also provide constraints on the paleoenvironmental evolution and bioevents of the area. The occurrence of pliopithecid primates in the middle Miocene of Inner Mongolia suggests humid habitats and challenges the scenarios suggesting arid and highly seasonal conditions for Central Asia since Early Miocene. The presence of pliopithecids may also bear witness to locally humid environments and greater habitat heterogeneity than previously known in central Inner Mongolia.

  5. An rbcL sequence from a Miocene Taxodium (bald cypress).

    PubMed Central

    Soltis, P S; Soltis, D E; Smiley, C J

    1992-01-01

    During the past decade, ancient DNAs from both animals and plants have been successfully extracted and analyzed. Recently, the age of DNA that can be recovered and sequenced was increased manyfold by the amplification and sequencing of a DNA fragment from a Magnolia fossil obtained from the Miocene Clarkia deposit (17-20 million yr old). However, the validity of this report has been questioned based on models predicting that DNA should be completely degraded after 4 million yr. We report here the successful amplification, sequencing, and analysis of a 1320-base-pair portion of the chloroplast gene rbcL from a Miocene Taxodium specimen, also from the Clarkia site. These data not only validate the earlier report of sequence data for a Magnolia species from the same site but also suggest that it may be possible to isolate and sequence DNAs routinely from the Clarkia deposit. The ability to recover and sequence DNAs of such age offers enormous research possibilities in the areas of molecular evolution, biogeography, and systematics. PMID:1729716

  6. Late Miocene to recent plate tectonic history of the southern Central America convergent margin

    NASA Astrophysics Data System (ADS)

    Morell, Kristin D.

    2015-10-01

    New plate reconstructions constrain the tectonic evolution of the subducting Cocos and Nazca plates across the southern Central American subduction zone from late Miocene to recent. Because of the strong relationships between lower and upper (Caribbean) plate dynamics along this margin, these constraints have wide-ranging implications for the timing and growth of upper plate deformation and volcanism in southern Central America. The reconstructions outline three important events in the Neogene history of this margin: (1) the coeval development of the Panama Triple Junction with the initiation of oblique subduction of the Nazca plate at ˜8.5 Ma; (2) the initiation of seamount and rough crust subduction beginning at ˜3-4 Ma; and (3) Cocos Ridge subduction from ˜2 to 3 Ma. A comparison of these events with independent geologic, geomorphic, volcanic, and stratigraphic data sets reveals that the timing, rates, and origin of subducting crust directly impacted the Neogene growth of upper plate deformation and volcanism in southern Central America. These analyses constrain the timing, geometry, and causes of a number of significant tectonic and volcanic processes, including rapid Plio-Quaternary arc-fore arc contraction due to Cocos Ridge subduction, the detachment of the Panama microplate at ˜1-3 Ma, and the late Miocene cessation of mantle-wedge-derived volcanism across ˜300 km of the subduction zone.

  7. Snake fangs from the Lower Miocene of Germany: evolutionary stability of perfect weapons

    NASA Astrophysics Data System (ADS)

    Kuch, Ulrich; Müller, Johannes; Mödden, Clemens; Mebs, Dietrich

    2006-02-01

    There is a general consensus that most of today’s nonvenomous snakes are descendants of venomous snakes that lost their venomous capabilities secondarily. This implies that the evolutionary history of venomous snakes and their venom apparatus should be older than the current evidence from the fossil record. We compared some of the oldest-known fossil snake fangs from the Lower Miocene of Germany with those of modern viperids and elapids and found their morphology to be indistinguishable from the modern forms. The primary function of recent elapid and viperid snake fangs is to facilitate the extremely rapid, stab-like application of highly toxic venoms. Our findings therefore indicate that the other components of the venom-delivery system of Early Miocene vipers and elapids were also highly developed, and that these snakes used their venom in the same way as their modern relatives. Thus, the fossil record supports the view that snakes used their venoms to rapidly subdue prey long before the mid-Tertiary onset of the global environmental changes that seem to have supported the successful radiation of venomous snakes.

  8. Magnetostratigraphy of the Miocene Las Arcas Formation, Santa María Valley, northwestern Argentina

    NASA Astrophysics Data System (ADS)

    Spagnuolo, Cecilia M.; Georgieff, Sergio M.; Rapalini, Augusto E.

    2015-11-01

    The first magnetostratigraphic study of the Las Arcas Formation (Late Miocene) was carried out in Las Totoritas creek (26º12‧S; 65º47‧W, NW Argentina), a key place in between of two geological provinces: Northwestern Pampean Ranges and Eastern Cordillera, in northwestern Argentina. This was accompanied by isotopic dating (9.01 ± 0.12 Ma, 40Ar-39Ar in amphibole) of the unit, obtained from a 3.4 m thick tuff intercalated at ∼45 m above the base. The Las Arcas Formation is 810 m thick at the sampling locality and it is mainly composed of tabular reddish conglomerates, sandstones and siltstones in both coarsening- and thickening-upward arrangements. The exposed section was sampled at 48 sites, 26 of which are interpreted as carrying primary magnetization. The new magnetostratigraphic column was correlated with the Geomagnetic Polarity Time Scale (GPTS), and suggests that deposition of the Las Arcas Formation strata started at around 9.1 Ma and ended around 6.8 Ma. The paleomagnetic pole obtained for this unit (Dec = 8.7° Inc = -43.9° dp = 14.9 dm 9.3) indicates that this area underwent non-significant rotation (11.0° ± 13.6°) since the Late Miocene.

  9. Geology and palaeontology of the Late Miocene Middle Awash valley, Afar rift, Ethiopia.

    PubMed

    WoldeGabriel, G; Haile-Selassie, Y; Renne, P R; Hart, W K; Ambrose, S H; Asfaw, B; Heiken, G; White, T

    2001-07-12

    The Middle Awash study area of Ethiopia's Afar rift has yielded abundant vertebrate fossils (approximately 10,000), including several hominid taxa. The study area contains a long sedimentary record spanning Late Miocene (5.3-11.2 Myr ago) to Holocene times. Exposed in a unique tectonic and volcanic transition zone between the main Ethiopian rift (MER) and the Afar rift, sediments along the western Afar rift margin in the Middle Awash provide a unique window on the Late Miocene of Ethiopia. These deposits have now yielded the earliest hominids, described in an accompanying paper and dated here to between 5.54 and 5.77 Myr. These geological and palaeobiological data from the Middle Awash provide fresh perspectives on hominid origins and early evolution. Here we show that these earliest hominids derive from relatively wet and wooded environments that were modulated by tectonic, volcanic, climatic and geomorphic processes. A similar wooded habitat also has been suggested for the 6.0 Myr hominoid fossils recently recovered from Lukeino, Kenya. These findings require fundamental reassessment of models that invoke a significant role for global climatic change and/or savannah habitat in the origin of hominids. PMID:11449271

  10. Fossil mushrooms from Miocene and Cretaceous ambers and the evolution of Homobasidiomycetes.

    PubMed

    Hibbett, D; Grimaldi, D; Donoghue, M

    1997-07-01

    Two species of fossil mushrooms that are similar to extant Tricholomataceae are described from Cretaceous and Miocene ambers. Archaeomarasmius leggetti gen. et sp. nov., from mid-Cretaceous amber of New Jersey, resembles the extant genera Marasmius and Marasmiellus. Two fruiting bodies of Archaeomarasmius were found. One consists of a complete pileus with stipe, and the other consists of a fragment of a pileus. The latter was accidentally exposed, and zxsubsequently was used for molecular systematics studies (attempts to amplify ribosomal DNA were unsuccessful) and electron microscopy. The spores are smooth and broadly elliptic with a distinct hilar appendage. Protomycena electra gen. et sp. nov., which is represented by a single complete fruiting body from Miocene amber of the Dominican Republic, is similar to the extant genus Mycena. Based on comparison to extant Marasmieae and Myceneae, Archaeomarasmius and Protomycena were probably saprophytes of leaf litter or wood debris. The poor phylogenetic resolution for extant homobasidiomycetes limits the inferences about divergence times of homobasidiomycete clades that can be drawn from Archaeomarasmius and Protomycena. The ages of these fossils lend support to hypotheses that the cosmopolitan distributions of certain mushroom taxa could be due to fragmentation of ancestral ranges via continental drift. Anatomical and molecular studies have suggested that there has been extensive convergence and parallelism in the evolution of homobasidiomycete fruiting body form. Nevertheless, the striking similarity of these fossils to extant forms suggests that in certain lineages homobasidiomycete macroevolution has also involved long periods during which there has been little morphological change. PMID:21708653

  11. Long-term evolution of an Oligocene/Miocene maar lake from Otago, New Zealand

    NASA Astrophysics Data System (ADS)

    Fox, B. R. S.; Wartho, J.; Wilson, G. S.; Lee, D. E.; Nelson, F. E.; Kaulfuss, U.

    2015-01-01

    Maar is a highly resolved maar lake deposit from the South Island of New Zealand comprising laminated diatomite punctuated by numerous diatomaceous turbidites. Basaltic clasts found in debris flow deposits near the base of the cored sedimentary sequence yielded two new 40Ar/39Ar dates of 24.51 ± 0.24 and 23.38 ± 0.24 Ma (2σ). The younger date agrees within error with a previously published 40Ar/39Ar date of 23.17 ± 0.19 Ma from a basaltic dyke adjacent to the maar crater. The diatomite is inferred to have been deposited over several tens of thousands of years in the latest Oligocene/earliest Miocene, and may have been coeval with the period of rapid glaciation and subsequent deglaciation of Antarctica known as the Mi-1 event. Sediment magnetic properties and SEM measurements indicate that the magnetic signal is dominated by pseudo-single domain pyrrhotite. The most likely source of detrital pyrrhotite is schist country rock fragments from the inferred tephra ring created by the phreatomagmatic eruption that formed the maar. Variations in magnetic mineral concentration indicate a decrease in erosional input throughout the depositional period, suggesting long-term (tens of thousands of years) environmental change in New Zealand in the latest Oligocene/earliest Miocene.

  12. Geology and tectonic setting of early miocene travertine deposits, Dominican Republic

    SciTech Connect

    Rodriguez, J.; Llinas, R.; Lebron, M.C.

    1985-01-01

    An extensive, ancient travertine deposit occurs immediately above a major unconformity within early Miocene carbonate rocks (Sombrerito Fm.) in the western Enriquillo Basin, Dominican Republic. The authors have mapped the area at a scale of 1:20,000 in order to better understand the geology and economic potential of the travertine which is widely used as an ornamental building stone in the Dominican Republic. The travertine occurs as a discontinuous tabular layer up to 15 m thick that outcrops within the complexly faulted Canoa Dome that forms the western plunging end of the reverse fault-bounded Sierra Martin Garcia. The measured stratigraphy of the dome from the oldest rocks in the center outwards consists of: 1) 100 m of grey to buff, chalky to crystalline limestones: 2) slight angular unconformity with 0 to 0.5 m of overlying conglomerate with limestone cobble clasts; 3) 0.5 to 15 m of grey to buff, indurated, microcrystalline travertine with zones of .1 to 1 cm, elongate cavities parallel to bedding; and 4) 250 m of interbedded siltstones and calcarenties. The genesis of the travertine deposit appears related to a previously unrecognized, widespread deformational, uplift, and thermal event that affected a shallow marine carbonate shelf in early Miocene time.

  13. Early and Middle Miocene Antarctic Climate and Ice Sheet variability: ANDRILL SMS Project results

    NASA Astrophysics Data System (ADS)

    Harwood, David; Florindo, Fabio; Levy, Richard; Talarico, Franco; Sms Project Science Team Members

    2010-05-01

    The sedimentary archive recovered during the ANDRILL Southern McMurdo Sound Project (SMS) comprises an expanded early and middle Miocene section deposited in a high-accommodation continental margin location, proximal to glacial ice influence from the West Antarctic Ice Sheet, East Antarctic Ice Sheet, and local ice in the Transantarctic Mountains. The AND-2A drillhole reached a total depth of 1138.54 mbsf, and obtained an excellent quality core with 98% recovery through the cored interval. Stratigraphic sequences and facies interpretations reveal a cyclical history of environmental variation influenced by climate, glacial advance/retreat cycles, and water depth variation. These lower and middle Miocene shallow marine sediments were deposited in the subsiding Victoria Land Basin, during a period of relatively steady thermal subsidence, on the coastal plain and continental shelf seaward of the rising Transantarctic Mountains. A well-developed chronostratigraphic framework developed through integrated diatom biostratigraphy, magnetostratigraphy, Sr isotope geochemistry, and radiometric dating of volcanic materials, allows for the comparison of events recognized in this drillcore with events identified in distal proxy records from deep-sea stable isotope studies, and in sea-level reconstructions based on continental shelf sequence stratigraphy. More than 60 sequences recognized in the AND-2A drillcore represent repeating lithological changes in glacimarine, terrigenous, volcanic and biogenic sediments, deposited during a dynamic climate regime, that appear to reflect a variable pace of Milankovitch forcing.

  14. Rapid diversification of falcons (Aves: Falconidae) due to expansion of open habitats in the Late Miocene.

    PubMed

    Fuchs, Jérôme; Johnson, Jeff A; Mindell, David P

    2015-01-01

    Understanding how and why lineages diversify is central to understanding the origins of biological diversity. The avian family Falconidae (caracaras, forest-falcons, falcons) has an uneven distribution of species among multiple well-supported clades, and provides a useful system for testing hypotheses about diversification rate and correlation with environmental changes. We analyzed eight independent loci for 1-7 individuals from each of the 64 currently recognized Falconidae species, together with two fossil falconid temporal calibrations, to assess phylogeny, absolute divergence times and potential shifts in diversification rate. Our analyses supported similar diversification ages in the Early to Middle Miocene for the three traditional subfamilies, Herpetotherinae, Polyborinae and Falconinae. We estimated that divergences within the subfamily Falconinae began about 16mya and divergences within the most species-rich genus, Falco, including about 60% of all Falconidae species, began about 7.5mya. We found evidence for a significant increase in diversification rate at the basal phylogenetic node for the genus Falco, and the timing for this rate shift correlates generally with expansion of C4 grasslands beginning around the Miocene/Pliocene transition. Concomitantly, Falco lineages that are distributed primarily in grassland or savannah habitats, as opposed to woodlands, and exhibit migratory, as opposed to sedentary, behavior experienced a higher diversification rate. PMID:25256056

  15. Development of Miocene-Pliocene reef trend, St. Croix, U. S. Virgin Islands

    SciTech Connect

    Gill, I.; Eby, D.E.; Hubbard, D.K.; Frost, S.H.

    1988-01-01

    The Miocene-Pliocene reef trend on St. Croix, U.S. Virgin Islands, rims the present southern western coasts of the island and includes accompanying lagoonal and forereef facies. The reef trend was established on a foram-algal bank facies that represents basinal shallowing from the deep-water pelagic and hemipelagic facies of the Miocene Kingshill Limestone. Information on facies distribution and thickness is derived from rock exposures and 22 test wells drilled to a maximum depth of 91 m. The greatest thickness of the reef facies exists in a subsidiary graben on the south coast of St. Croix. The thickness of the reef section in this locality is due to preservation of the section in a downdropped block. Reef faunas include extant corals, as well as several extinct genera. Extant corals (e.g. Montastrea annularis, Diploria sp., and Porites porites) and extinct corals (e.g., Stylophora affinis, Antillea bilobata, and Thysanus sp.) are the main reef frame-builders. Coralline algea and large benthic foraminifera are significant contributors to the sediments both prior to and during scleractinian reef growth. Dolomitization and calcite cementation occur prominantly in an area corresponding to a Holocene lagoon. The spatial distribution of the dolomite suggests that the lagoon is a Tertiary feature directly related to the dolomitization process. Stable isotopic values suggest dolomitization of fluids of elevated salinity.

  16. Biostratigraphic sequence analysis of Oligocene-Lower Miocene sections in the Orocual Field, Eastern Venezuela Basin

    SciTech Connect

    Giffuni, G.; Castro-Mora, M.

    1996-08-01

    A detailed biostratigraphic study of the Oligocene-Miocene boundary was carried out in sections 1000 ft thick of ten wells of the Orocual Field, Eastern Venezuela, The sequences under investigation carry a rich microfauna of benthic and planktonic foraminifera and calcareous nannoplankton. About 500 samples were analyzed and nearly 150 species of foraminifera and 60 of nannoplankton calcareous were identified. The planktonic assemblages allow the identification of zones N3 and N4 of Blow, 1969; zones NP23, NP24, NP25 and NN1 of Martini, 1971; and zones F and E of Stainforth et al., 1959 of the Carapita Formation. The paleoenvironments of these sediments were determined rather precisely and vary from inner shelf to middle slope. Paleobathymetric curves of several wells are included. High and low fossil abundance and diversity peaks were used to recognize two sequences of the third order and five of the fourth order between 24.8 Ma and 26.5 Ma. A generalized transgressive trend is evident from the Late Oligocene to the Early Miocene.

  17. Rock Magnetic Record of the Middle Miocene Climatic Transition at ODP Site 747, Southern Ocean

    NASA Astrophysics Data System (ADS)

    Abrajevitch, A.; Roberts, A. P.; Kodama, K.

    2013-12-01

    ODP Site 747, located on the central Kerguelen Plateau, contains a compete record of the Middle Miocene Climatic Transition (MMCT) - a major cooling event that followed the warm mid-Miocene Climatic Optimum and culminated in an 'icehouse' climate regime. Because of its unusually well preserved and rich foraminiferal assemblages, the MMCT interval at Site 747 has been a focus of several high-resolution paleoclimatic studies that have effectively established this sequence as a reference for the Southern Ocean. Major changes in species abundances across the MMCT are conventionally interpreted to reflect changes in water temperature and salinity. Our XRF and rock magnetic study reveals a good correlation between terrigenous input (likely from local volcanic sources) and the abundances of the dominant planktonic foraminiferal species. Such a correlation suggests that nutrient flux (iron fertilization) played a significant role in controlling microplankton communities during the MMCT at Site 747. Concentration-dependent rock magnetic parameters appear to be a useful proxy for nutrient flux in this pelagic marine environment.

  18. Amazonian amphibian diversity is primarily derived from late Miocene Andean lineages.

    PubMed

    Santos, Juan C; Coloma, Luis A; Summers, Kyle; Caldwell, Janalee P; Ree, Richard; Cannatella, David C

    2009-03-10

    The Neotropics contains half of remaining rainforests and Earth's largest reservoir of amphibian biodiversity. However, determinants of Neotropical biodiversity (i.e., vicariance, dispersals, extinctions, and radiations) earlier than the Quaternary are largely unstudied. Using a novel method of ancestral area reconstruction and relaxed Bayesian clock analyses, we reconstructed the biogeography of the poison frog clade (Dendrobatidae). We rejected an Amazonian center-of-origin in favor of a complex connectivity model expanding over the Neotropics. We inferred 14 dispersals into and 18 out of Amazonia to adjacent regions; the Andes were the major source of dispersals into Amazonia. We found three episodes of lineage dispersal with two interleaved periods of vicariant events between South and Central America. During the late Miocene, Amazonian, and Central American-Chocoan lineages significantly increased their diversity compared to the Andean and Guianan-Venezuelan-Brazilian Shield counterparts. Significant percentage of dendrobatid diversity in Amazonia and Chocó resulted from repeated immigrations, with radiations at <10.0 million years ago (MYA), rather than in situ diversification. In contrast, the Andes, Venezuelan Highlands, and Guiana Shield have undergone extended in situ diversification at near constant rate since the Oligocene. The effects of Miocene paleogeographic events on Neotropical diversification dynamics provided the framework under which Quaternary patterns of endemism evolved. PMID:19278298

  19. Origin of smectite cement in Miocene-age sands of deep Gulf of Mexico basin

    SciTech Connect

    Whynot, J.D.; Tieh, T.T.

    1988-01-01

    Miocene-age sands from Deep Sea Drilling Project (DSDP) Site 90, located on the Sigsbee Abyssal Plain, are cemented by authigenic smectite. These sands are medium to coarse-grained and contain abundant volcanic and plutonic rock fragments. In contrast, similar Miocene-age sands from DSDP Site 91, also located on the Sigsbee Abyssal Plain, do not show development of smectite cement. Smectite cement development was controlled by early post-depositional fluid flow, as the cemented Site 90 and uncemented Site 91 sands are similar in age, texture, composition, burial depth and initial pore-water composition. Cemented sands at Site 90 are thin (<1m thick) and bounded by low-permeability interlaminated fine-grained sand and mud that acted to reduce the rate of fluid flow through the coarser grained sand. Reduction in fluid flow allowed the concentrations of alumino-silicate polymers, alkali, and alkali-earth cations, supplied by the alteration and dissolution of volcanic rock fragments, to reach levels necessary for the precipitation of smectite. Uncemented sands at Site 91 are thicker (>1m thick) and not bounded by interlaminated sand and mud. Thus, fluid flow through sands at Site 91 was not impeded, and dissolution products were removed before they could reach concentrations necessary to precipitate cements.

  20. Ribosomal RNA gene fragments from fossilized cyanobacteria identified in primary gypsum from the late Miocene, Italy.

    PubMed

    Panieri, G; Lugli, S; Manzi, V; Roveri, M; Schreiber, B C; Palinska, K A

    2010-03-01

    Earth scientists have searched for signs of microscopic life in ancient samples of permafrost, ice, deep-sea sediments, amber, salt and chert. Until now, evidence of cyanobacteria has not been reported in any studies of ancient DNA older than a few thousand years. Here, we investigate morphologically, biochemically and genetically primary evaporites deposited in situ during the late Miocene (Messinian) Salinity Crisis from the north-eastern Apennines of Italy. The evaporites contain fossilized bacterial structures having identical morphological forms as modern microbes. We successfully extracted and amplified genetic material belonging to ancient cyanobacteria from gypsum crystals dating back to 5.910-5.816 Ma, when the Mediterranean became a giant hypersaline brine pool. This finding represents the oldest ancient cyanobacterial DNA to date. Our clone library and its phylogenetic comparison with present cyanobacterial populations point to a marine origin for the depositional basin. This investigation opens the possibility of including fossil cyanobacterial DNA into the palaeo-reconstruction of various environments and could also be used to quantify the ecological importance of cyanobacteria through geological time. These genetic markers serve as biosignatures providing important clues about ancient life and begin a new discussion concerning the debate on the origin of late Miocene evaporites in the Mediterranean. PMID:20059556

  1. Late Miocene episodic lakes in the arid Tarim Basin, western China

    PubMed Central

    Liu, Weiguo; Liu, Zhonghui; An, Zhisheng; Sun, Jimin; Chang, Hong; Wang, Ning; Dong, Jibao; Wang, Huanye

    2014-01-01

    The Tibetan Plateau uplift and Cenozoic global cooling are thought to induce enhanced aridification in the Asian interior. Although the onset of Asian desertification is proposed to have started in the earliest Miocene, prevailing desert environment in the Tarim Basin, currently providing much of the Asian eolian dust sources, is only a geologically recent phenomenon. Here we report episodic occurrences of lacustrine environments during the Late Miocene and investigate how the episodic lakes vanished in the basin. Our oxygen isotopic (δ18O) record demonstrates that before the prevailing desert environment, episodic changes frequently alternating between lacustrine and fluvial-eolian environments can be linked to orbital variations. Wetter lacustrine phases generally corresponded to periods of high eccentricity and possibly high obliquity, and vice versa, suggesting a temperature control on the regional moisture level on orbital timescales. Boron isotopic (δ11B) and δ18O records, together with other geochemical indicators, consistently show that the episodic lakes finally dried up at ∼4.9 million years ago (Ma), permanently and irreversibly. Although the episodic occurrences of lakes appear to be linked to orbitally induced global climatic changes, the plateau (Tibetan, Pamir, and Tianshan) uplift was primarily responsible for the final vanishing of the episodic lakes in the Tarim Basin, occurring at a relatively warm, stable climate period. PMID:25368156

  2. Evidence for deep-water evaporite deposition in the Miocene Kareem Formation, Gemsa basin, eastern Egypt

    SciTech Connect

    May, J.A.; Stonecipher, S.A.; Steinmetz, J.C. ); Dyess, J.N. )

    1991-03-01

    The correct interpretation of intercalated Miocene siliciclastics and evaporites of Gemsa basin is crucial for understanding early rift tectonics of the Gulf of Suez, pinpointing the timing of isolation of the Gulf from the Mediterranean, and developing exploration plays. Evaporites of the Kareem Formation comprise celestites and massive, 'chicken-wire,' and laminated anhydrites. Although previously interpreted as sabkha deposits; sedimentologic, petrographic, and paleontologic analyses indicate these evaporites more likely formed in a submarine setting. Marls that encase the evaporites contain a diverse and abundant assemblage of nannoplankton, planktonic foraminifera, diatoms, pteropods, and fish scales indicative of basinal deposition. Associated turbidites also denote deep-water sedimentation. The paucity of benthic diatoms and foraminifera, plus the presence of unburrowed shales, phosphate nodules, early ferroan carbonate cements, and authigenic pyrite, suggest periodic anoxic, or at least disaerobic, bottom waters. These sequences probably represent partial isolation of the Gulf of Suez by middle Miocene, producing periodic basin restriction and evaporative drawdown. Episodes of increasing salinity likely caused the progressive decreases in foram abundance and diversity in marls beneath the anhydrites, culminating in subaqueous evaporite formation. Diverse, indigenous nannoplankton assemblages from shale seams within the anhydrites suggest Gemsa basin was stratified; shallow open-marine conditions coexisted with anhydrite crystallization from deeper hypersaline waters.

  3. Lower Miocene plant assemblage with coastal-marsh herbaceous monocots from the Vienna Basin (Slovakia)

    NASA Astrophysics Data System (ADS)

    Kva?ek, Zlatko; Teodoridis, Vasilis; Kov?ov, Marianna; Schlgl, Jn; Sitr, Viliam

    2014-06-01

    A new plant assemblage of Cerov-Lieskov from Lower Miocene (Karpatian) deposits in the Vienna Basin (western Slovakia) is preserved in a relatively deep, upper-slope marine environment. Depositional conditions with high sedimentation rates allowed exceptional preservation of plant remains. The plant assemblage consists of (1) conifers represented by foliage of Pinus hepios and Tetraclinis salicornioides, a seed cone of Pinus cf. ornata, and by pollen of the Cupressaceae, Pinaceae, Pinus sp. and Cathaya sp., and (2) angiosperms represented by Cinnamomum polymorphum, Platanus neptuni, Potamogeton sp. and lauroid foliage, by pollen of Liquidambar sp., Engelhardia sp. and Craigia sp., and in particular by infructescences (so far interpreted as belonging to cereal ears). We validate genus and species assignments of the infructescences: they belong to Palaeotriticum Sitr, including P. mockii Sitr and P. carpaticum Sitr, and probably represent herbaceous monocots that inhabited coastal marshes, similar to the living grass Spartina. Similar infructescences occur in the Lower and Middle Miocene deposits of the Carpathian Foredeep (Slup in Moravia), Tunjice Hills (ale in Slovenia), and probably also in the Swiss Molasse (Lausanne). This plant assemblage demonstrates that the paleovegetation was represented by evergreen woodland with pines and grasses in undergrowth, similar to vegetation inhabiting coastal brackish marshes today. It also indicates subtropical climatic conditions in the Vienna Basin (central Paratethys), similar to those implied by other coeval plant assemblages from Central Europe

  4. The early Miocene onset of a ventilated circulation regime in the Arctic Ocean.

    PubMed

    Jakobsson, Martin; Backman, Jan; Rudels, Bert; Nycander, Jonas; Frank, Martin; Mayer, Larry; Jokat, Wilfried; Sangiorgi, Francesca; O'Regan, Matthew; Brinkhuis, Henk; King, John; Moran, Kathryn

    2007-06-21

    Deep-water formation in the northern North Atlantic Ocean and the Arctic Ocean is a key driver of the global thermohaline circulation and hence also of global climate. Deciphering the history of the circulation regime in the Arctic Ocean has long been prevented by the lack of data from cores of Cenozoic sediments from the Arctic's deep-sea floor. Similarly, the timing of the opening of a connection between the northern North Atlantic and the Arctic Ocean, permitting deep-water exchange, has been poorly constrained. This situation changed when the first drill cores were recovered from the central Arctic Ocean. Here we use these cores to show that the transition from poorly oxygenated to fully oxygenated ('ventilated') conditions in the Arctic Ocean occurred during the later part of early Miocene times. We attribute this pronounced change in ventilation regime to the opening of the Fram Strait. A palaeo-geographic and palaeo-bathymetric reconstruction of the Arctic Ocean, together with a physical oceanographic analysis of the evolving strait and sill conditions in the Fram Strait, suggests that the Arctic Ocean went from an oxygen-poor 'lake stage', to a transitional 'estuarine sea' phase with variable ventilation, and finally to the fully ventilated 'ocean' phase 17.5 Myr ago. The timing of this palaeo-oceanographic change coincides with the onset of the middle Miocene climatic optimum, although it remains unclear if there is a causal relationship between these two events. PMID:17581581

  5. A geochemical study of macerals from a Miocene lignite and an Eocene bituminous coal, Indonesia

    USGS Publications Warehouse

    Stankiewicz, B.A.; Kruge, M.A.; Mastalerz, Maria

    1996-01-01

    Optical and chemical studies of maceral concentrates from a Miocene lignite and an Eocene high-volatile bituminous C coal from southeastern Kalimantan, Indonesia were undertaken using pyro-Lysis, optical, electron microprobe and FTIR techniques Pyrolysis products of vitrinite from bituminous coal were dominated by straight-chain aliphatics and phenols. The huminite of the Miocene lignite produced mostly phenolic compounds upon pyrolysis. Differences in the pyrolysis products between the huminite and vitrinite samples reflect both maturation related and paleobotanical differences. An undefined aliphatic source and/or bacterial biomass were the likely contributors of n-alkyl moieties to the vitrinite. The resinite fraction in the lignite yielded dammar-derived pyrolysis products, as well as aliphatics and phenols as the products of admixed huminite and other liptinites. The optically defined resinite-rich fraction of the bituminous coal from Kalimantan produced abundant n-aliphatic moieties upon pyrolysis, but only two major resin markers (cadalene and 1,6-dimethylnaphthalene). This phenomenon is likely due to the fact that Eocene resins were not dammar-related. Data from the electron microprobe and Fourier transform infrared spectrometry strongly support the results obtained by Py GC MS and microscopy.

  6. Gratkorn - A new late Middle Miocene vertebrate fauna from Styria (Late Sarmatian, Austria)

    NASA Astrophysics Data System (ADS)

    Gross, M.; Böhme, M.; Prieto, J.

    2009-04-01

    Integrated stratigraphic approaches provide precise correlations of global standard stages with regional Paratethys stages. Nevertheless, higher resolution stratigraphic matching of terrestrial deposits remains challenging due to the lack of a practical continental biostratigraphy. The mostly used tool for biostratigraphic correlation of non-marine deposits in the Old World is still the concept of Neogene Mammal-zones (MN-zones). However, at higher biostratigraphic resolution (<1 million years) this concept looses its practicability and has to be replaced by a taxon-range-zonation. To solve this problem a higher number of independently dated small-mammal localities are needed. This is especially crucial for the late Middle to earliest Late Miocene, for which vertebrate faunas in the (Central-)Paratethyan area rare. Recently, a new vertebrate fauna was discovered at the locality Gratkorn (clay pit St. Stefan) just beyond the northwestern margin of the Styrian Basin (Gratkorn Basin; 10 km NW Graz; 15°20'55"E/47°08'15"N). The fauna originates from a c. 0.5 m thick hydromorphic paleosol, underlain by fluvial sands and gravels and topped by c. 15 m thick limnic pelites (Gross, 2008). Sedimentological data as well as the gastropod (Harzhauser et al., 2008) and vertebrate faunas point to a highly structured, more or less vegetated alluvial fan/braided river landscape. Active and abandoned fluvial channels, moist floodplain-soils and ephemeral ponds but also nearby dryer open areas and limestone screes of the up-lifting Palaeozoic basement offered a wide range of habitats. The occurrence of xero- and thermophile terrestrial gastropods and ectothermic vertebrates correspond well with the late Middle/early Late Miocene dry-spell in Central Europe (Böhme et al., 2008). Furthermore, an overall semiarid climate is supported by the development of a calcrete horizon c. 0.6 m below the fossiliferous horizon. The vertebrate remains are irregularly distributed throughout the paleosol. Although articulated skeletons are missing, skeletal elements belonging to the same individual were found frequently close to each other. Many bones are broken and display imprints of gnawing structures. These taphonomic features point to a longer surface exposure before burial without considerable transportation. Trampling and the activity of scavengers (crunching, displacement of cadavers) are probable. Locally small- and medium-sized mammal remains (jaws and postcranial elements) of e.g., hamsters, flying squirrels, gymnures and shrews are concentrated, perhaps demonstrating feeding places of carnivores or more probably of birds of prey. Nonetheless, from geologic point of view, this paleosol represents an event horizon, which accumulated rapidly maybe within tens or hundreds of years. The vertebrate fauna comprises of scattered fishes (e.g. cyprinids, gobiids, ?channids), amphibians (e.g. salamandrids, ranids, discoglossids, bufonids, pelobatids,), reptiles (scincids, lacertids, gekkonids, anguids, varanids, colubrids, testudinids, emydids), birds (coliiformes), rodents and lagomorphs (cricetids, glirids, eomyids, sciurids, castorids), insectivores and chiropterans (erinaceids, soricids, talpids), and large mammals (suids, tragulids, moschids, cervids, ?palaeomerycids, equids, chalicotheriids, rhinos, proboscidians, carnivors). Litho- and biostratigraphy (terrestrial gastropods) as well as magnetostratigraphic data and the sequence stratigraphic and geodynamic frame indicate an age of 12-12.2 Ma (early Late Sarmatian s.str., chron 5An.1n) for the locality. Therefore, Gratkorn is one of richest and most complete fauna of the late Middle Miocene of Central Europe and will be confidentially one of the key faunas for a high-resolution continental biostratigraphy and the comprehension of the faunal succession and interchanges near the Middle/Late Miocene transition. Acknowledgements This is a preliminary overview of the Gratkorn vertebrate fauna. Several taxa are still under investigation. We are especially grateful to Gudrun Daxner-Höck, Ursula Göhlich (both Natural History Museum Vienna) and Getrud Rössner (University of Munich) for their comments to the rodents, ruminants, proboscidians and bird remains. References Böhme, M., Ilg, A., Winklhofer, M. 2008. Late Miocene "washhouse" climate in Europe.- Earth and Planetary Science Letters, 275: 393-401. Gross, M., 2008. A limnic ostracod fauna from the surroundings of the Central Paratethys (Late Middle Miocene/Early Late Miocene; Styrian Basin; Austria).- Palaeogeography, Palaeoclimatology, Palaeoecology, 264/3-4: 263-276. Harzhauser, M., Gross, M. & Binder, H., 2008. Biostratigraphy of Middle Miocene (Sarmatian) wetland systems in an Eastern Alpine intramontane basin (Gratkorn Basin, Austria): the terrestrial gastropod approach.- Geologica Carpathica, 59/1: 45-58.

  7. Diversity dynamics of Miocene mammals in relation to the history of tectonism and climate

    PubMed Central

    Finarelli, John A.; Badgley, Catherine

    2010-01-01

    Continental biodiversity gradients result not only from ecological processes, but also from evolutionary and geohistorical processes involving biotic turnover in landscape and climatic history over millions of years. Here, we investigate the evolutionary and historical contributions to the gradient of increasing species richness with topographic complexity. We analysed a dataset of 418 fossil rodent species from western North America spanning 25 to 5 Ma. We compared diversification histories between tectonically active (Intermontane West) and quiescent (Great Plains) regions. Although diversification histories differed between the two regions, species richness, origination rate and extinction rate per million years were not systematically different over the 20 Myr interval. In the tectonically active region, the greatest increase in originations coincided with a Middle Miocene episode of intensified tectonic activity and global warming. During subsequent global cooling, species richness declined in the montane region and increased on the Great Plains. These results suggest that interactions between tectonic activity and climate change stimulate diversification in mammals. The elevational diversity gradient characteristic of modern mammalian faunas was not a persistent feature over geologic time. Rather, the Miocene rodent record suggests that the elevational diversity gradient is a transient feature arising during particular episodes of Earth's history. PMID:20427339

  8. Late Miocene episodic lakes in the arid Tarim Basin, western China.

    PubMed

    Liu, Weiguo; Liu, Zhonghui; An, Zhisheng; Sun, Jimin; Chang, Hong; Wang, Ning; Dong, Jibao; Wang, Huanye

    2014-11-18

    The Tibetan Plateau uplift and Cenozoic global cooling are thought to induce enhanced aridification in the Asian interior. Although the onset of Asian desertification is proposed to have started in the earliest Miocene, prevailing desert environment in the Tarim Basin, currently providing mu