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1

Sequence stratigraphic principles applied to the Miocene Hawthorn Group, west-central Florida  

SciTech Connect

Sequence boundaries for the Miocene Hawthorn Group in the ROMP 20 drill core from Osprey, Sarasota County, FL were generally delineated by lithologic variations recognized from core slabs, thin section analysis, and geophysical logs. At least six depositional sequences representing third order sea level fluctuations were identified. Depositional environments were determined on the basis of the characteristic lithologic constituents including rip-up clasts, pellets, fossils, laminations, burrow, degree of induration, and grain sorting. The sequence boundaries appear to have formed when the rate of the eustatic fall exceeded basin subsidence rates producing a relative sea level fall at a depositional shoreline break. As a result of the basinward facies shift associated with this sequence type, peritidal facies may directly overlie deeper water facies. Subaerial exposure and erosion can be expected. The sequence of facies representing progressively deeper water depositional environments, followed by a progressive shallowing, were present between bounding surfaces. Among the six sequences recognized, four were clearly delineated as representative of regression, subaerial exposure, and subsequent transgression. Two sequences were less clearly defined and probably represent transitional facies which had exposure surfaces developed. Comparison of the petrologically established sequence stratigraphy with published sea level curves resulted in a strong correlation between the number of sequences recognized and the number of coastal on-lap/off-lap cycles depicted for the early to middle Miocene. This correlation suggests that petrologic examination of core slabs, with supplemental thin section data, can provide useful information regarding the recognition of stratigraphic sequences and relative sea level fluctuations, particularly, in situations where seismic data may not be available.

Norton, V.L.; Randazzo, A.F. (Florida Univ., Gainesville, FL (United States). Dept. of Geology)

1993-03-01

2

Natural Arsenic in the Miocene Hawthorn Group, Florida: Wide Ranging Implications for ASR, Phosphate Mining, Private Well  

NASA Astrophysics Data System (ADS)

In order to understand the mineralogical association and distribution of arsenic (As) in the Hawthorn Group we examined in detail the chemical and mineralogical composition of 370 samples that were collected from 16 cores in central Florida. In our study area the Hawthorn group consists primarily of a basal carbonate unit (the Arcadia Formation) and an upper siliciclastic unit (The Peace River Formation). The Peace River Formation contains appreciable amounts of phosphate and is currently being exploited for phosphate ore. Samples were taken for each Formation at intervals of 25ft. In addition to the interval samples we also took samples that contained visible pyrite crystals, iron oxides, green clays, phosphatic and organic material. These additional samples were collected because of their potential of high As concentrations. Arsenic concentrations were determined by hydride generation - atomic fluorescence spectrometry (HG-AFS) after digestion with aqua regia (3:1 HCl and HNO3). The elements Fe, Na, Al, Si, Mg, Ca, S, P, and K were measured on the same solutions by inductively coupled plasma optical emission spectrometry (ICP-OES). The identification of discrete minerals was aided by scanning electron microscopy (SEM) and chemical compositions were obtained by electron-probe microanalyses (EMPA). Our study indicates that the average As concentrations significantly change from 9.0 ppm in the Peace River Formation to 3.0 ppm in the Tampa Member of the Arcadia Formation. As concentrations for all Hawthorn samples vary from 0.07 to 68.98 ppm ( ? = 5.6, ? = 7.1). Our detailed mineralogical and geochemical study demonstrates that: (1) The As in the Hawthorn group varies from the formation to formation and is mostly concentrated in trace minerals, such as pyrite; (2) Concentrations of the As in pyrite crystals can vary drastically from a minimum of 0 ppm to a maximum of 8260 ppm; (3) Pyrite is an unevenly distributed throughout the Hawthorn Group; (4) Phosphate and organic material, clays, and iron oxides contain lower As concentrations contrasted to pyrite; (5) Pyrite occurs in framboidal and euhedral forms. Because phosphorous, arsenic and sulfur are chemically closely related, they often occur together in nature, thus posing a potential problem for the phosphate industry. There have been several occurrences of swine fatalities due to arsenic poisoning as a result of phosphate feed supplements. Information about the concentration, distribution and mineralogical association of naturally occurring As is important, because this is a first step to forecast its behavior during anthropogenic induced physico-chemical changes in the aquifer. Recently, aquifer storage and recovery (ASR) facilities in central Florida reported As concentrations in excess of 100 ? g/L in recovered water. The ASR storage zone is the Suwannee Limestone, which directly underlies the Hawthorn sediments. It is crucial to the future of ASR in this area to understand the source and distribution of arsenic in the overlying Hawthorn Group and the cycling of arsenic in the Florida platform.

Lazareva, O. V.; Pichler, T.

2004-12-01

3

Origin of dolomite in the phosphatic Hawthorne Group of Florida  

SciTech Connect

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.

Compton, J.S.; Hall, D.L.; Mallinson, D.J. (Univ. of South Florida, St. Petersburg, FL (United States). Dept. of Marine Science); Hodell, D.A. (Univ. of Florida, Gainesville, FL (United States). Dept. of Geology)

1994-07-01

4

Health effects of hawthorn.  

PubMed

Hawthorn medicinal extract has long been a favored herbal remedy in Europe. The active components of this slow-acting cardiotonic agent are thought to be flavonoids and oligomeric procyanidins. The most studied hawthorn extracts are WS 1442 and LI 132. Reviews of placebo- controlled trials have reported both subjective and objective improvement in patients with mild forms of heart failure (New York Heart Association classes I through III). Other studies of hawthorn in patients with heart failure have revealed improvement in clinical symptoms, pressure-heart rate product, left ventricular ejection fraction, and patients' subjective sense of well-being. However, there is no evidence of a notable reduction in mortality or sudden death. Hawthorn is well tolerated; the most common adverse effects are vertigo and dizziness. Theoretic interactions exist with antiarrhythmics, antihypertensives, digoxin, and antihyperlipidemic agents. Proven conventional therapies for heart failure are still recommended until the safety and effectiveness of hawthorn has been proven in long-term studies. PMID:20148500

Dahmer, Stephen; Scott, Emilie

2010-02-15

5

Nathaniel Hawthorne Bicentennial Exhibition  

NSDL National Science Digital Library

Rightly regarded as one of the great figures of American letters, Nathaniel Hawthorne is best known for such works as The House of the Seven Gables, and of course one of America's oft-cited morality tales, The Scarlet Letter. He was part of a wide circle of other notable figures in 19th-century American literature that included Henry David Thoreau, Herman Melville, and Henry Wadsworth Longfellow. Given his strong connection with New England and his birth in Salem, Massachusetts, it is not surprising that the acclaimed Peabody Museum in that same town has mounted a significant exhibit to commemorate the bicentennial of Hawthorne's birth in 1804. For those who cannot make it to Salem in the coming months, this online exhibit is a true delight. The site includes the complete digitized images of "The Spectator", which was a hand-copied newspaper produced by Hawthorne when he was 16. Clearly, those with a penchant for learning about the life of Hawthorne will want to make several trips to this site.

6

Programmed Student Achievement: A Hawthorne Effect?  

ERIC Educational Resources Information Center

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)

Haddad, Nabil F.; And Others

1975-01-01

7

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

ERIC Educational Resources Information Center

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

Gottfredson, Gary D.

1996-01-01

8

Hawthorne's Dating Problem in The Scarlet Letter  

Microsoft Academic Search

This article explores the dating problem in Nathaniel Hawthorne's novel, The Scarlet Letter. In The Custom House, Hawthorne relates how he discovers several foolscap sheets written by a predecessor, Mr. Surveyor Pue, about Hester Prynne. These six sheets supposedly offer two types of accounts about Hester: aged persons, alive in the time of Pue and from whose oral testimony he

Hal Blythe; Charlie Sweet

2003-01-01

9

Hawthorne effects and research into professional practice.  

PubMed

The Hawthorne studies in the 1930s demonstrated how difficult it is to understand workplace behaviour, and this includes professional performance. Studies of interventions to improve professional performance, such as audit, can provide useful information for those considering using such methods, but cannot replace judgement. In particular, there is no single phenomenon that can be labelled 'the Hawthorne effect'. The process of triangulation, considering a subject from different perspectives, might overcome the problems of Hawthorne effects better than using a single method such as controlled trials. PMID:11240840

Holden, J D

2001-02-01

10

Genetic relationships among some hawthorn (Crataegus spp.) species and genotypes.  

PubMed

The genus Crataegus is well distributed in Turkey as a wild plant, with numerous, inherently variable species and genotypes. RAPD markers were used to study 17 hawthorn genotypes belonging to Crataegus monogyna ssp. monogyna Jacq (2 genotypes), C. monogyna ssp. azarella Jacq (1), Crataegus pontica K.Koch (3), Crataegus orientalis var. orientalis Pallas Ex Bieb (3), Crataegus pseudoheterophylla Pojark (1), Crataegus aronia var. dentata Browicz (1), C. aronia var. aronia Browicz (4), and Crateagus x bornmuelleri Zabel (2). The 10 RAPD primers produced 72 polymorphic bands (88% polymorphism). A dendrogram based on Jaccard's index included four major groups and one outgroup according to taxa. The lowest genetic variability was observed within C. aronia var. aronia genotypes. The study demonstrated that RAPD analysis is efficient for genotyping wild-grown hawthorns. PMID:20640884

Yilmaz, Kadir Ugurtan; Yanar, Makbule; Ercisli, Sezai; Sahiner, Hatice; Taskin, Tuncer; Zengin, Yasar

2010-10-01

11

Hawthorn  

MedlinePLUS

... Is CAM? Safety Information For Health Care Professionals Clinical Practice Guidelines Literature Reviews More » Research NCCAM Research ... at NCCAM Division of Intramural Research Policies & Guidelines Clinical Trials Labs at NCCAM More » Grants & Funding Funding ...

12

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

ERIC Educational Resources Information Center

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)

Harshbarger, Scott

1994-01-01

13

The Hawthorne effect and energy awareness  

PubMed Central

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.

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

2013-01-01

14

Validation of the Antidiabetic and Hypolipidemic Effects of Hawthorn by Assessment of Gluconeogenesis and Lipogenesis Related Genes and AMP-Activated Protein Kinase Phosphorylation  

PubMed Central

Since with the increased use of antidiabetic and antihyperlipidemic effect of phytonutrients for daily supplement has gained considerable attention worldwide, we examine the effect and molecular mechanism of Crataegus pinnatifida Bge. var. major N.E. Br. (hawthorn) by quantifying the expression of hepatic gluconeogenesis and lipogenesis on diabetes and dyslipidemia in high-fat (HF)-fed C57BL/6J mice. Firstly, mice were divided randomly into two groups: the control (CON) group was fed with a low-fat diet, whereas the experimental group was fed a 45% HF diet for 8 weeks. Afterwards, the CON group was treated with vehicle, whereas the HF group was subdivided into five groups and was given orally hawthorn extract (including 0.2, 0.5, 1.0?g/kg/day extracts) or rosiglitazone (Rosi) or vehicle for 4 weeks afterward. Diabetic mice showed an increase in plasma glucose and insulin. Glucose lowering was comparable with Rosi-treated mice. This study demonstrated that hawthorn was effective in ameliorating the HF diet-induced hyperglycemia, hypertriglyceridemia and hypercholesterolaemia. Hawthorn extract significantly increases the hepatic protein contents of AMP-activated protein kinase (AMPK) phosphorylation and reduces expression of phosphenol pyruvate carboxykinase (PEPCK) and glucose production. Furthermore, hawthorn decreased in hepatic triacylglycerol and cholesterol synthesis (including sterol regulatory element binding protein-1c (SREBP-1c), fatty acid synthase (FAS), SREBP2). An increase in expressions of apoA-I gene and high-density lipoprotein cholesterol (HDL-C) was detected in HF-fed mice treated with high dose hawthorn. Our data suggest that hawthorn extract are capable of decreasing glucose production and triacylglycerol synthesis by inducing AMPK-phosphorylation and hawthorn is a candidate source of antidiabetic and antihyperlipidemic phytonutrients factors.

Shih, Chun-Ching; Lin, Cheng-Hsiu; Lin, Yih-Jiun; Wu, Jin-Bin

2013-01-01

15

Incremental Compositional Zoning in the Widespread Phonolitic Ayagaures Ignimbrite in Miocene Fataga Group on Gran Canaria (Canary Islands)  

NASA Astrophysics Data System (ADS)

The widespread phonolitic Ayagaures Ignimbrite (AI) (11.8 Ma) is a moderately to highly welded cooling unit of the Miocene Fataga Group (ca 13.3 - ca 9 Ma) on Gran Canaria (GC) (Canary Islands). Most of the up to 20 flow units have been mapped throughout the exposed area of at least 250km2. AI (average thickness 20- 25 m) dips regularly 4-5° in southern to southwestern GC and has reached the sea at many places. Its mapped volume is approximately 4.5 km3. This plus tentatively correlated ODP syn-ignimbrite deposits (Sumita and Schmincke, 1998 and unpubl.) and its probable former widespread distribution over at least western GC suggest a total erupted magma volume of >50km3. Phonolitic AI contains up to 20 vol % of dominantly anorthoclase-sanidine and minor (<1 vol %) biotite, Fe- augite, titanite, haüyne and apatite. The cooling unit is compositionally zoned becoming more mafic upwards. Trace elements and REE show significant magma reservoir zoning in both bulk rock and phenocryst composition, while major elements change little. All phenocryst species were unzoned and their composition within each flow unit extremely homogeneous. The shallow level magma reservoir is interpreted to have been compositionally zoned but thermodynamically equilibrated. Strong mixing preceded the separation of the magma chamber into several small convective layers in which one single growth event of alkali feldspar and biotite occurred. The presence of large haüyne and titanite crystals within the topmost layers of the reservoir (basal flow unit) and a locally preserved highly evolved fallout tephra document a highly fractionated volatile-rich but small-volume cupola. AI represents the most evolved part of a larger partially evacuated magma reservoir. Progressive downward tapping of the reservoir was controlled by incremental caldera collapse. Unzoned phenocrysts, incremental CU zoning and evacuation reversals show that mixing did not occur after separation into layers.

Jutzeler, M.; Schmincke, H.; Sumita, M.

2006-12-01

16

Tissue distribution comparison between healthy and fatty liver rats after oral administration of hawthorn leaf extract.  

PubMed

Hawthorn leaves, a well-known traditional Chinese medicine, have been widely used for treating cardiovascular and fatty liver diseases. The present study aimed to investigate the therapeutic basis treating fatty liver disease by comparing the tissue distribution of six compounds of hawthorn leaf extract (HLE) in fatty liver rats and healthy rats after oral administration at first day, half month and one month, separately. Therefore, a sensitive and specific HPLC method with internal standard was developed and validated to determine chlorogenic acid, vitexin-4''-O-glucoside, vitexin-2''-O-rhamnoside, vitexin, rutin and hyperoside in the tissues including heart, liver, spleen, kidney, stomach and intestine. The results indicated that the six compounds in HLE presented some bioactivity in treating rat fatty liver as the concentrations of the six compounds varied significantly in inter- and intragroup comparisons (healthy and/or fatty liver group). PMID:24254959

Yin, Jingjing; Qu, Jianguo; Zhang, Wenjie; Lu, Dongrui; Gao, Yucong; Ying, Xixiang; Kang, Tingguo

2014-05-01

17

Proprietary Herbal Medicines in Circulatory Disorders: Hawthorn, Ginkgo, Padma 28  

Microsoft Academic Search

A look at the available clinical evidence of herbal preparations from hawthorn (leaves, flowers, fruits), Padma 28 (Swiss-Tibetan\\u000a herbal preparation with 20 herbal drugs) and ginkgo (leaves) in terms of circulatory disorders shows the following: in chronic\\u000a heart failure New York Heart Association (NYHA) II a meta-analysis showed that hydroethanolic extracts from hawthorn leaves\\u000a and flowers, given at a daily

Jörg Melzer; Reinhard Saller

18

Hawthorn (Crataegus spp.) in the treatment of cardiovascular disease  

PubMed Central

The medicinal properties of hawthorn (Crataegus spp., a genus comprising approximately 300 species) have been utilized by many cultures for a variety of therapeutic purposes for many centuries. In the Western world cardiovascular disease (CVD) has become one of the single most significant causes of premature death. Echoing this situation, more recent research into the therapeutic benefits of hawthorn preparations has focused primarily upon its cardiovascular effects. This review covers research into the various mechanisms of action proposed for Crataegus preparations, clinical trials involving Crataegus preparations, and the herb's safety profile. Clinical trials reviewed have been inconsistent in terms of criteria used (sample size, preparation, dosage, etc) but have been largely consistent with regard to positive outcomes. An investigation into data available to date regarding hawthorn preparations and herb/drug interactions reveals that theoretical adverse interactions have not been experienced in practice. Further, adverse reactions relating to the use of hawthorn preparations are infrequent and mild, even at higher dosage ranges. A recent retrospective study by Zick et al. has suggested a negative outcome for the long-term use of hawthorn in the prognosis of heart failure. These findings are examined in this paper. Although further research is needed in certain areas, current research to date suggests that hawthorn may potentially represent a safe, effective, nontoxic agent in the treatment of CVD and ischemic heart disease (IHD).

Tassell, Mary C.; Kingston, Rosari; Gilroy, Deirdre; Lehane, Mary; Furey, Ambrose

2010-01-01

19

Some Fruit Traits of Hawthorn (Crataegus spp.) Genetic Resources from Malatya, Turkey  

Microsoft Academic Search

Hawthorns (Crataegus spp.) are native to Turkey. It is possible to see wild hawthorn bushes or trees in every regions of Turkey. This study deals with evaluating fruit characteristics of 42 genotypes belonging to five different hawthorn species collected from Malatya (eastern Turkey). The mean values of fruit height, fruit diameter, fruit weight, seed height and seed diameter differed statistically

M. Fikret Balta; F. Çelik; N. Turkoglu; K. Ozrenk; F. Ozgokçe

20

The Persistence of Theocracy: Hawthorne's The Scarlet Letter  

Microsoft Academic Search

This article argues that Nathaniel Hawthorne's The Scarlet Letter can provide insight into the persistent appeal of the moral and political certitudes that theocracy offers and that can serve as a corrective to liberal secularism's often myopic tendency to downplay the continuing moral and political appeal of religious belief and authority. Focusing on three puzzles raised in the structure and

Constance C. T. Hunt

2009-01-01

21

Fourth Period Discovers Hester as Mother: Hawthorne's Mother?  

ERIC Educational Resources Information Center

A teacher discusses how she used criticism of "The Scarlet Letter," when studying the book, in her honors class. The students were also intrigued by the biographical information they learned about Hawthorne, and eager to use it in interpreting his novel. (SRT)

Heginbotham, Eleanor

1986-01-01

22

Nathaniel Hawthorne and Herman Melville: A Research Guide.  

ERIC Educational Resources Information Center

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…

Van Noate, Judith, Comp.

23

Triterpenic Acids Present in Hawthorn Lower Plasma Cholesterol by Inhibiting Intestinal ACAT Activity in Hamsters  

PubMed Central

Hawthorn (Crataegus pinnatifida) is an edible fruit used in traditional Chinese medicine to lower plasma lipids. This study explored lipid-lowering compounds and underlying mechanisms of action of hawthorn. Hawthorn powder extracts inhibited acylCoA:cholesterol acyltransferase (ACAT) activity in Caco-2 cells. The inhibitory activity was positively associated with triterpenic acid (i.e., oleanolic acid (OA) and ursolic acid (UA)) contents in the extracts. Cholesterol lowering effects of hawthorn and its potential additive effect in combination with plant sterol esters (PSE) were further studied in hamsters. Animals were fed a semi-synthetic diet containing 0.08% (w/w) cholesterol (control) or the same diet supplemented with (i) 0.37% hawthorn dichloromethane extract, (ii) 0.24% PSE, (iii) hawthorn dichloromethane extract (0.37%) plus PSE (0.24%) or (iv) OA/UA mixture (0.01%) for 4 weeks. Compared to the control diet, hawthorn, PSE, hawthorn plus PSE and OA/UA significantly lowered plasma non-HDL (VLDL + LDL) cholesterol concentrations by 8%, 9%, 21% and 6% and decreased hepatic cholesterol ester content by 9%, 23%, 46% and 22%, respectively. The cholesterol lowering effects of these ingredients were conversely associated with their capacities in increasing fecal neutral sterol excretion. In conclusion, OA and UA are responsible for the cholesterol lowering effect of hawthorn by inhibiting intestinal ACAT activity. In addition, hawthorn and particularly its bioactive compounds (OA and UA) enhanced the cholesterol lowering effect of plant sterols.

Lin, Yuguang; Vermeer, Mario A.; Trautwein, Elke A.

2011-01-01

24

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)

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, ?95 = 4.2°), and R polarity (dec/inc = 178.2°/-59.2°, k = 16, ?95 = 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.

Dominguez, Ada R.; Van der Voo, Rob

2014-06-01

25

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)

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, ?95 = 4.2°), and R polarity (dec/inc = 178.2°/-59.2°, k = 16, ?95 = 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.

Dominguez, Ada R.; Van der Voo, Rob

2014-05-01

26

An extinct mud turtle of the Kinosternon flavescens group (Testudines, Kinosternidae) from the middle Miocene (late Barstovian) of New Mexico  

Microsoft Academic Search

The complete skeleton of a fossil mud turtle, Kinosternon pojoaque, n. sp., is described from the late Barstovian Rodent Pocket, San Ildefonso Locality of Santa Fe County, New Mexico. The new species represents the oldest member of the Kinosternon flavescens group and suggests that this clade first evolved in the southwestern United States, which, along with northern Mexico, is the

Jason R. Bourque

2012-01-01

27

Genetic Relationships Among Some Hawthorn ( Crataegus spp.) Species and Genotypes  

Microsoft Academic Search

The genus Crataegus is well distributed in Turkey as a wild plant, with numerous, inherently variable species and genotypes. RAPD markers were\\u000a used to study 17 hawthorn genotypes belonging to Crataegus monogyna ssp. monogyna Jacq (2 genotypes), C. monogyna ssp. azarella Jacq (1), Crataegus pontica K.Koch (3), Crataegus orientalis var. orientalis Pallas Ex Bieb (3), Crataegus pseudoheterophylla Pojark (1), Crataegus

Kadir Ugurtan Yilmaz; Makbule Yanar; Sezai Ercisli; Hatice Sahiner; Tuncer Taskin; Yasar Zengin

2010-01-01

28

Stratigraphy, Paleomagnetism, and Anisotropy of Magnetic Susceptibility of the Miocene Stanislaus Group, Central Sierra Nevada and Sweetwater Mountains, California and Nevada  

NASA Astrophysics Data System (ADS)

Paleomagnetism and anisotropy of magnetic susceptibility (AMS) reveal pyroclastic flow patterns, stratigraphic correlations, and tectonic rotations in the Miocene Stanislaus Group, an extensive volcanic sequence in the central Sierra Nevada, California, and in the Walker Lane of California and Nevada. The Stanislaus Group is a useful stratigraphic marker in regard to the post-9 Ma uplift of the Sierra Nevada and transtensional tectonics within the central Walker Lane. In ascending order, the Stanislaus Group consists of the Table Mountain Latite, Eureka Valley Tuff, and the Dardanelles Formation with alkali-silica compositions ranging from basaltic trachyandesite to trachyte. The stratigraphy of the Eureka Valley Tuff is refined by detailed geologic mapping of the reference section located at Tollhouse Flat, California. We measured directions of remanent magnetization at 32 sites within the Stanislaus Group. The Table Mountain Latite has a distinctively shallow reversed-polarity direction of I=-26.0° and D=162.8° at sampling sites in the Sierran foothills, although the unit mainly consists of normal-polarity flows near the Sierran crest. The Tollhouse Flat Member of the Eureka Valley Tuff has a reversed-polarity magnetization (I=-62.8°, D=159.9°). The By-Day Member (I=52.4°, D=8.6°) and Upper Member (I=27.9°, D=358.0°) of the Eureka Valley Tuff overlie a polarity transition within the Eureka Valley Tuff. The Dardanelles Formation also has normal polarity. We measured vertical-axis rotations of sites in the Walker Lane and Sweetwater Mountains by establishing a virtual geomagnetic reference pole for the Tollhouse Flat Member of the Eureka Valley Tuff in the relatively stable Sierran block. We infer clockwise vertical-axis rotations of approximately 8.5° to 30° in the central Walker Lane north of Mono Lake, California, and to the east in the Anchorite Hills, Nevada. No significant vertical axis rotations relative to the central Sierra Nevada were indicated within the Sweetwater Mountains, California. The AMS results from 19 sites show that the Eureka Valley Tuff flowed outward from its proposed source area, the Little Walker Caldera, and the flow patterns are consistent with mapped channels in the Sierra Nevada and Walker Lane.

King, N. M.; Hillhouse, J. W.; Gromme, S.; Hausback, B. P.

2006-12-01

29

76 FR 25320 - Hawthorn Water LLC; Notice of Preliminary Permit Application Accepted for Filing and Soliciting...  

Federal Register 2010, 2011, 2012, 2013

...No. 13852-000] Hawthorn Water LLC; Notice of Preliminary...September 30, 2010, Hawthorn Water LLC filed an application, pursuant...otherwise enter upon lands or waters owned by others without the...120-foot-high, 3,000-foot-long earth embankment dam...

2011-05-04

30

76 FR 67103 - Proposed Revision of Class D and Class E Airspace; Hawthorne, CA  

Federal Register 2010, 2011, 2012, 2013

...11-AWP-10] Proposed Revision of Class D and Class E Airspace; Hawthorne, CA AGENCY...SUMMARY: This action proposes to revise Class D and E airspace at Jack Northrop Field/Hawthorne...Regulations (14 CFR) Part 71 by revising Class D airspace and Class E airspace...

2011-10-31

31

THE HAWTHORNE EXPERIMENTS AND THE INTRODUCTION OF JEAN PIAGET IN AMERICAN INDUSTRIAL PSYCHOLOGY, 1929–1932  

Microsoft Academic Search

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

Yeh Hsueh

2002-01-01

32

Miocene deepwater oceanography  

NASA Astrophysics Data System (ADS)

A global synthesis of Miocene benthic foraminiferal carbon and oxygen isotopic and faunal abundance data indicates that Miocene thermohaline circulation evolved through three regimes corresponding approximately to early, middle, and late Miocene times. There is evidence for major qualitative differences between the circulation of the modern ocean and the Miocene ocean prior to 11 Ma. The 13C/12C ratios of the benthic foraminifera Cibicidoides are interpreted in terms of water mass aging, i.e., the progressive depletion of dissolved O2 and lowering of ?13C values as the result of oxidation of organic matter as water flows further from its sources at the surface of the oceans. Both isotopic and faunal data indicate that the early Miocene regime, from 22 to 15 Ma, was the most different from today's. During that interval intermediate and deep waters of both the Atlantic and the Pacific oceans aged in a northward direction, and the intermediate waters of the Indian, the South Atlantic and the South Pacific oceans were consistently the youngest in the global ocean. We speculate that early Miocene global thermohaline circulation may have been strongly influenced by the influx of warm saline water, Tethyan Indian Saline Water, from the Tethys into the northern Indian Ocean. The isotopic and faunal data suggest that flow from the Tethyan region into the Indian Ocean diminished or terminated at about 14 Ma. Isotopic and faunal data give no evidence for North Atlantic Deep Water (NADW) formation prior to about 14.5 Ma (with the exception of a brief episode in the early Miocene). From 14.5 to 11 Ma NADW formation was weak, and circumpolar and Antarctic water flooded the deep South Atlantic and South Pacific as the Antarctic ice cap grew. From about 10 Ma to the end of the Miocene, thermohaline circulation resembled the modern circulation in many ways. In latest Miocene time (6 to 5 Ma) circulation patterns were very similar to today's except that NADW formation was greatly diminished. The distribution pattern of siliceous oozes in Miocene sediments is consistent with our proposed reconstruction of thermohaline circulation. Major changes which occurred in circulation during the middle Miocene were probably related to the closing of the Tethys and may have contributed to rapid middle Miocene growth of the Antarctic ice cap. Appendices 1, 4, 6, and 7 are available withentire article on microfiche. Order fromAmerican Geophysical Union, 2000 FloridaAvenue, N.W., Washington, DC 20009.Document 88P-002; $5.00. Payment mustaccompany order.

Woodruff, Fay; Savin, Samuel M.

1989-02-01

33

Hawthorn extract for treating chronic heart failure: meta-analysis of randomized trials.  

PubMed

The aim of this meta-analysis was to assess the evidence from rigorous clinical trials of the use of hawthorn extract to treat patients with chronic heart failure. We searched the literature using MEDLINE, EMBASE, the Cochrane Library, CINAHL, CISCOM, and AMED. Experts on and manufacturers of commercial preparations containing hawthorn extract were asked to contribute published and unpublished studies. There were no restrictions about the language of publication. Two reviewers independently performed the screening of studies, selection, validation, data extraction, and the assessment of methodological quality. To be included, studies were required to state that they were randomized, double-blind, and placebo controlled, and used hawthorn extract monopreparations. Thirteen trials met all inclusion criteria. In most of the studies, hawthorn was used as an adjunct to conventional treatment. Eight trials including 632 patients with chronic heart failure (New York Heart Association classes I to III) provided data that were suitable for meta-analysis. For the physiologic outcome of maximal workload, treatment with hawthorn extract was more beneficial than placebo (weighted mean difference, 7 Watt; 95% confidence interval [CI]: 3 to 11 Watt; P < 0.01; n = 310 patients). The pressure-heart rate product also showed a beneficial decrease (weighted mean difference, -20; 95% CI: -32 to -8; n = 264 patients) with hawthorn treatment. Symptoms such as dyspnea and fatigue improved significantly with hawthorn treatment as compared with placebo. Reported adverse events were infrequent, mild, and transient; they included nausea, dizziness, and cardiac and gastrointestinal complaints. In conclusion, these results suggest that there is a significant benefit from hawthorn extract as an adjunctive treatment for chronic heart failure. PMID:12798455

Pittler, Max H; Schmidt, Katja; Ernst, Edzard

2003-06-01

34

Hawthorn fruit increases the antioxidant capacity and reduces lipid peroxidation in senescence-accelerated mice  

Microsoft Academic Search

Hawthorn fruit has long been used as a folk medicine with many medicinal benefits. HPLC analysis revealed that hawthorn fruit\\u000a extract (HFE) contained 19.86% procyanidin B2, 15.27% epicatechin, 3.10% chlorogenic acid, 2.91% hyperoside, and 1.34% isoquercitrin.\\u000a Antioxidants are essential for protection of the bodies against the damaging action of free radicals. And we hypothesized\\u000a that HFE could enhance antioxidant defenses

Hao WangZesheng; Zesheng Zhang; Ying Guo; Ping Sun; Xiaoling Lv; Yanbo Zuo

2011-01-01

35

Polyphenolic profile and biological activity of Chinese hawthorn (Crataegus pinnatifida BUNGE) fruits.  

PubMed

Chinese hawthorn (Crataegus pinnatifida Bge.) fruits are rich in polyphenols (e.g., epicatechin, procyanidin B2, procyanidin B5, procyanidin C1, hyperoside, isoquercitrin and chlorogenic acid)--active compounds that exert beneficial effects. This review summarizes all information available on polyphenolic content and methods for their quantification in Chinese hawthorn berries and the relationships between individual polyphenolic compounds as well. The influence of species or cultivars, the locality of cultivation, the stage of maturity, and extract preparation conditions on the polyphenolic content were discussed as well. Currently, only fruits of C. pinnatifida and C. pinnatifida var. major are included in the Chinese Pharmacopoeia. Recent trials have demonstrated the efficacy of Chinese hawthorn fruit in lowering blood cholesterol and the risk of cardiovascular diseases. The fruit has also demonstrated anti-inflammatory and anti-tumour activities. This review deals mainly with the biological activity of the fruit related to its antioxidant properties. PMID:23222867

Jurikova, Tunde; Sochor, Jiri; Rop, Otakar; Mlcek, Jiri; Balla, Stefan; Szekeres, Ladislav; Adam, Vojtech; Kizek, Rene

2012-01-01

36

Energy Engineering Analysis Program, energy survey of Army Industrial Facilities, Western Area Demilitarization Facility Hawthorne Ermy Ammunition Plant Hawthorne, Nevada. Volume 1. Final report  

SciTech Connect

This report summarizes all work for the Energy Survey of Army Industrial Facilities, Energy Engineering Analysis Program (EEAP) at the Western Area Demilitarization Facility (WADF) of the Hawthorne Army Ammunition Plant (HWAAP), Hawthorne, Nevada, authorized under Contract No. DACA03-92-C-0155 with the U.S. Army Corps of Engineers, Sacramento District, California. The purpose of this energy survey is to develop a set of projects and actions that will reduce energy consumption and operating costs of selected facilities at the WADF. A preliminary inspection of facilities at WADF by Keller Gannon that identified potential retrofit opportunities was submitted as the EEAP Study and Criteria Review in December 1993. This document formed the basis of the Detailed Scope of Work for this study. Facilities included in the survey and study, together with operational status, are listed in Table 1 - 1. The complete scope of work appears in Appendix.

NONE

1995-03-17

37

Energy Engineering Analysis Program, energy survey of Army Industrial Facilities, Western Area Demilitarization Facility, Hawthorne Army Ammunition Plant, Hawthorne, Nevada; Volume 1 - energy report. Final report  

SciTech Connect

This report summarizes all work for the Energy Survey of Army Industrial Facilities, Energy Engineering Analysis Program (EEAP) at the Western Area Demilitarization Facility (WADF) of the Hawthorne Army Ammunition Plant (HWAAP), Hawthorne, Nevada, authorized under Contract No. DACA05-92-C-0155 with the U.S. Army Corps of Engineers, Sacramento District, California. The purpose of this energy survey is to develop a set of projects and actions that will reduce energy consumption and operating costs of selected facilities at the WADF. A preliminary inspection of facilities at WADF by Keller Gannon that identified potential retrofit opportunities was submitted as the EEAP Study and Criteria Review in December 1993. This document formed the basis of the Detailed Scope of Work for this study. Facilities included in the survey and study, together with operational status.

NONE

1995-03-17

38

Comparative Protective Effect of Hawthorn Berry Hydroalcoholic Extract, Atorvastatin, and Mesalamine on Experimentally Induced Colitis in Rats  

PubMed Central

Abstract The protective effect of hydroalcoholic extract of hawthorn berries (HBE) on acetic acid (AA)–induced colitis in rats was investigated. Forty-two Wistar rats were divided into seven groups, including control and test groups (n=6). The control animals received saline, and the test animals were treated with saline (sham group), mesalamine (50?mg/kg; M group), atorvastatin (20?mg/kg; A group), HBE (100?mg/kg; H group), mesalamine and HBE (HM group), or atorvastatin plus HBE (HA group), 3 days before and a week after colitis induction. Colitis was induced by administration of 1?mL AA (4%) via a polyethylene catheter intrarectally. High-performance liquid chromatography analyses showed that HBE contained 0.13% and 0.5% oleanolic acid and ursolic acid, respectively. Elevated myeloperoxidase activity and lipid peroxidation were attenuated in the HA group. The H and HM groups showed marked reductions in colitis-induced decreases in total thiol molecules and body weight. The histopathological studies revealed that HBE decreased colitis-induced edema and infiltration of neutrophils. Our data suggest the anti-inflammatory and antioxidant effects of HBE and atorvastatin protect against AA-induced colitis. The anti-inflammatory effect of HBE may be attributable to its ability to decrease myeloperoxidase activity as a biomarker of neutrophil infiltration.

Shafie-Irannejad, Vahid; Hobbenaghi, Rahim; Tabatabaie, Seyed Hamed; Moshtaghion, Seyed-Mehdi

2013-01-01

39

New tie-points for the geomagnetic polarity time scale during the Middle Miocene from the Mogán Group on Gran Canaria and Ocean Drilling Program Leg 157 site 953  

NASA Astrophysics Data System (ADS)

A thick sequence of volcaniclastic sediments drilled at site 953 during Ocean Drilling Program (ODP) Leg 157 northeast of Gran Canaria (Canary Islands) contains an almost complete magneto-stratigraphy back to the shield stage of the island 14.8 Ma ago. Onshore, a sequence of reversals has been identified and dated in 19 dominantly peralkaline rhyolitic ignimbrites, one rhyolitic, and one basaltic lava flow of the Mogán Group (13.35-13.95 Ma), which overlie basalt flows of the island's shield stage (>14 Ma). The magneto-stratigraphy of the ignimbrites onshore has been correlated with the marine magneto-stratigraphy at site 953, determined in syn-ignimbritic volcaniclastic turbidites, which were deposited practically synchronously immediately following the entry of the parent pyroclastic flows into the sea around the circumference of the island. The four polarity intervals recorded in the sequence of the Mogán Group ignimbrites correspond to C5ACr, C5ACn, C5ADr and C5ADn. Single crystal 40Ar/39Ar-age determinations of the ignimbrites bracketing the polarity changes gave the following ages and uncertainties for the reversals C5AD (t) (13.95±0.07 Ma), C5AC(o) (13.89±0.08 Ma), and C5AC(t) (13.47±0.09 Ma). The newly dated polarity changes fit and refine the Miocene age model proposed in the global polarity time scale.

Herr, B.; Fuller, M.; Sumita, M.; van den Bogaard, P.; Schmincke, H.-U.; Heider, F.

2002-08-01

40

Sex, lies and needlework: review of The scarlet letter (Nathaniel Hawthorne; movie directed by Roland Joffe)  

Microsoft Academic Search

I have an image of an extraterrestrial anthropologist holding a copy of Nathaniel Hawthorne's 1850 novel in one hand and a video tape of Roland Joff's 1995 film in the other. I imagine her examining these two versions of The Scarlet Letter as the only artefacts of human culture available to her. I can hear her baffled query: 'what could

A. Sutherland-Kelly

1997-01-01

41

The Market Place of The Scarlet Letter: Hawthorne and Hester as Artist Objects  

Microsoft Academic Search

Like many of Nathaniel Hawthorne's fictional writings, The Scarlet Letter and its introduction ?The Custom House? consider the identity of the artist within both the public world of production and the private interior of the artist's self perception. However, this most celebrated text casts the artist uniquely, doubling the artist character in a purely fictional Hester Prynne and a fictionalized

Kerry Hasler-Brooks

42

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

Federal Register 2010, 2011, 2012, 2013

...Docket No. 11-AWP-10] Revision of Class D and Class E Airspace; Hawthorne, CA AGENCY...SUMMARY: This action revises Class D and Class E airspace at Jack Northrop Field...the FAA. No comments were received. Class D airspace and Class E airspace...

2012-02-13

43

Radioprotective effects of Hawthorn against genotoxicity induced by gamma irradiation in human blood lymphocytes.  

PubMed

The radioprotective effect of hawthorn (Crataegus microphylla) fruit extract was investigated in cultured blood lymphocytes from human volunteers. Peripheral blood samples were collected from five human volunteers 10 min before and 1, 2 and 3 h after a single oral ingestion of 500 mg hawthorn powder extract. At each time point, the whole blood was exposed in vitro to 150 cGy of cobalt-60 gamma irradiation, and then the lymphocytes were cultured with mitogenic stimulation to determine the micronuclei in cytokinesis-blocked binucleated cell. The lymphocytes in the blood samples collected after extract ingestion exhibited a significant decrease in the incidence of binucleated cells containing micronuclei as compared to similarly irradiated lymphocytes collected prior to extract ingestion. The maximum decrease in the frequency of micronuclei-containing cells was observed at 1 h after ingestion of Hawthorn extract (on average a 44% decrease). These data suggest that it may be possible to use Hawthorn extracts in personnel exposed to radiation in order to protect lymphocytes from radiation effects. PMID:18769933

Hosseinimehr, Seyed Jalal; Mahmoudzadeh, Aziz; Azadbakht, Mohammad; Akhlaghpoor, Shahram

2009-02-01

44

Investigation of Hawthorne Army Ammunition Plant Magazine Fire - 9 August 1989.  

National Technical Information Service (NTIS)

A magazine fire involving 30,715 pounds of Navy propelling charges (hazard class 1.3/mass fire) occurred at Hawthorne AAP. The material was stored in Magazine 116-14-E. The propellant was unserviceable (condition code H), awaiting disposal instructions. A...

R. A. Loyd

1990-01-01

45

Miocene Antarctic Terrestrial Realm  

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

46

The Miocene rodents of Serbia  

NASA Astrophysics Data System (ADS)

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, Vra?evi?i, 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.

Markovic, Z.

2009-04-01

47

Miocene reef corals: A review  

SciTech Connect

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.

Frost, S.H.

1988-01-01

48

Calcareous Nannofossil Evolution Vs. Climatic Evolution In The Miocene  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

49

An overview of Miocene reefs  

SciTech Connect

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.

Jordan, C.F. Jr. (Mobil Research and Development Corp., Dallas, TX (USA)); Colgan, M.W. (College of Charleston, SC (USA)); Frost, S.H. (Unocal, Los Angeles, CA (USA)); Glenn, E.C. (Phillips Petroleum, Bartlesville, OK (USA)); Bosence, D. (Royal Holloway and Bedford New College, Egham (England)); Esteban, M. (ERICO Petroleum Information Ltd., London (England))

1990-05-01

50

B. F. Skinner and T. N. Whitehead: a brief encounter, research similarities, hawthorne revisited, what next?  

PubMed

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

Claus, Calvin K

2007-01-01

51

Shark-bitten vertebrate coprolites from the Miocene of Maryland  

Microsoft Academic Search

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

Stephen J. Godfrey; Joshua B. Smith

2010-01-01

52

The comparison of anti-oxidative kinetics in vitro of the fluid extract from maidenhair tree, motherwort and hawthorn.  

PubMed

The aim of the study was to perform a quantitative analysis of fluid extracts of maidenhair tree (Ginkgo biloba L.), motherwort (Leonurus cardiaca L.) and hawthorn (Crataegus monogyna Jacq.), to evaluate their antioxidant activity and to compare their ability to inactivate free radicals. The antioxidant activity was measured using the DPPH*and the ABTS*+ radical scavenging reaction systems. The study showed that the manifestation of the radical scavenging capacity in the DPPH* reaction system was in the following order: the fluid extract of hawthorn (70.37 +/- 0.80%) > the fluid extract of maidenhair tree (82.63 +/- 0.23%) > the fluid extract of motherwort (84.89 +/- 0.18%), while in the ABTS*+ reaction system, the manifestation of the radical scavenging capacity was in the following order: the fluid extract of hawthorn (87.09 +/- 0.55%) > the fluid extract of motherwort (88.28 +/- 1.06%) > the fluid extract of maidenhair tree (88.39 +/- 0.72%). The results showed that in the DPPH* reaction system, fluid extract of motherwort manifested higher antioxidant activity, compared to the fluid extracts of maidenhair tree and hawthorn. By contrast, in the ABTS*+ reaction system, higher antioxidant activity was found in the fluid extract of maidenhair tree, compared to the fluid extracts of motherwort and hawthorn. This would suggest that preparations manufactured from these herbal raw materials could be used as effective preventive means and valuable additional remedies in the treatment of diseases caused by oxidative stress. PMID:19702174

Bernatoniene, Jurga; Kucinskaite, Agne; Masteikova, Ruta; Kalveniene, Zenona; Kasparaviciene, Giedre; Savickas, Arunas

2009-01-01

53

Constitutive and herbivore?induced volatiles in pear, alder and hawthorn trees  

Microsoft Academic Search

Summary.   Qualitative and quantitative differences among pear cultivars were found\\u000a in constitutive and Cacopsylla-induced volatiles, depending on\\u000a experimental treatment of the trees (i.e., uninfested and partly or\\u000a completely infested by psyllids). Blend differences were also found\\u000a between pear cultivars and wild-type pear, alder and hawthorn–the\\u000a latter trees are frequently present in pear orchard\\u000a hedgerows. ¶Interesting differences were found in the

Petru Scutareanu; Jan Bruin; Maarten A. Posthumus; Bas Drukker

2003-01-01

54

Mediterranean Miocene carbonates: facies models and diagenesis  

SciTech Connect

Miocene carbonates can bridge the gap between Holocene and older carbonate sequences, thus enhancing understanding of depositional and diagenetic patterns. Miocene carbonates can bridge this gap because of their similarity to Holocene counterparts and the ease of using these carbonates to reconstruct tectonic, paleogeographic, and paleoclimatic settings. In the Mediterranean, the Miocene provides a superb set of exposures and a wide variety of facies models in different geologic settings.

Esteban, M.E.

1987-11-01

55

Anti-inflammatory effect of the water fraction from hawthorn fruit on LPS-stimulated RAW 264.7 cells.  

PubMed

The hawthorn fruit (Crataegus pinnatifida Bunge var. typica Schneider) is used as a traditional medicine in Korea. The objective of this study was to understand the mechanisms of the anti-inflammatory effects of the water fractionated portion of hawthorn fruit on a lipopolysaccharide (LPS)-stimulated RAW 264.7 cellular model. The level of nitric oxide (NO) production in the water fraction and LPS-treated RAW 264.7 cells were determined with an ELISA. The cytotoxicity of the water fraction and LPS was measured with an MTT assay. Expression of nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF)-?, interleukin 6 (IL-6), and interleukin 1? (IL-1?) mRNA were analyzed with a reverse transcription polymerase chain reaction (RT-PCR). The water fraction of hawthorn fruit was determined to be safe and significantly inhibited NO production in LPS-stimulated RAW 264.7 cells and suppressed COX-2, TNF-?, IL-1?, and IL-6 expression. The observed anti-inflammatory effects of the water fraction of hawthorn fruit might be attributed to the down-regulation of COX-2, TNF-?, IL-1?, and IL-6 expression in LPS-stimulated RAW 264.7 cells. PMID:21556222

Li, Chunmei; Wang, Myeong-Hyeon

2011-04-01

56

Anti-inflammatory effect of the water fraction from hawthorn fruit on LPS-stimulated RAW 264.7 cells  

PubMed Central

The hawthorn fruit (Crataegus pinnatifida Bunge var. typica Schneider) is used as a traditional medicine in Korea. The objective of this study was to understand the mechanisms of the anti-inflammatory effects of the water fractionated portion of hawthorn fruit on a lipopolysaccharide (LPS)-stimulated RAW 264.7 cellular model. The level of nitric oxide (NO) production in the water fraction and LPS-treated RAW 264.7 cells were determined with an ELISA. The cytotoxicity of the water fraction and LPS was measured with an MTT assay. Expression of nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF)-?, interleukin 6 (IL-6), and interleukin 1? (IL-1?) mRNA were analyzed with a reverse transcription polymerase chain reaction (RT-PCR). The water fraction of hawthorn fruit was determined to be safe and significantly inhibited NO production in LPS-stimulated RAW 264.7 cells and suppressed COX-2, TNF-?, IL-1?, and IL-6 expression. The observed anti-inflammatory effects of the water fraction of hawthorn fruit might be attributed to the down-regulation of COX-2, TNF-?, IL-1?, and IL-6 expression in LPS-stimulated RAW 264.7 cells.

Li, Chunmei

2011-01-01

57

Using the Hawthorne eect to examine the gap between a doctor's best possible practice and actual performance  

Microsoft Academic Search

Many doctors in developing countries provide considerably lower levels of quality to their patients than they have been trained to provide. The gap between best practice and actual performance is dicult to measure for individual doctors who dier in levels of training and experience and who face very dierent types of patients. We exploit the Hawthorne eect—in which doctors change

Kenneth L. Leonard; Melkiory C. Masatu

58

Using the Hawthorne Effect to Examine the Gap Between a Doctor's Best Possible Practice and Actual Performance  

Microsoft Academic Search

Many doctors in developing countries provide considerably lower levels of quality to their patients than they have been trained to provide. The gap between best practice and actual performance is difficult to measure for individual doctors who differ in levels of training and experience and who face very different types of patients. We exploit the Hawthorne effect—in which doctors change

Kenneth L. Leonard; Melkiory C. Masatu

2008-01-01

59

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

PubMed Central

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.

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

2013-01-01

60

Miocene benthic foraminiferal isotope records: A synthesis  

USGS Publications Warehouse

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.

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

1981-01-01

61

Shark-bitten vertebrate coprolites from the Miocene of Maryland  

Microsoft Academic Search

Coprolites (fossilized feces) preserve a wide range of biogenic components, from bacteria and spores to a variety of vertebrate\\u000a tissues. Two coprolites from the Calvert Cliffs outcrop belt (Miocene-aged Chesapeake Group), MD, USA, preserve shark tooth\\u000a impressions in the form of partial dental arcades. The specimens are the first known coprolites to preserve vertebrate tooth\\u000a marks. They provide another example

Stephen J. Godfrey; Joshua B. Smith

2010-01-01

62

Miocene reefs in western Mediterranean  

SciTech Connect

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.

Esteban, M.

1988-01-01

63

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

PubMed Central

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 Folin–Ciocalteu 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.

Caliskan, Oguzhan; Gunduz, Kazim; Serce, Sedat; Toplu, Celil; Kamiloglu, Onder; Sengul, Memnune; Ercisli, Sezai

2012-01-01

64

Effect of hawthorn standardized extract on flow mediated dilation in prehypertensive and mildly hypertensive adults: a randomized, controlled cross-over trial  

PubMed Central

Background Hawthorn extract has been used for cardiovascular diseases for centuries. Recent trials have demonstrated its efficacy for the treatment of heart failure, and the results of several small trials suggest it may lower blood pressure. However, there is little published evidence to guide its dosing. The blood pressure lowering effect of hawthorn has been linked to nitric oxide-mediated vasodilation. The aim of this study was to investigate the relationship between hawthorn extract dose and brachial artery flow mediated dilation (FMD), an indirect measure of nitric oxide release. Methods We used a four-period cross-over design to evaluate brachial artery FMD in response to placebo or hawthorn extract (standardized to 50 mg oligomeric procyanidin per 250 mg extract). Randomly sequenced doses of hawthorn extract (1000 mg, 1500 mg, and 2500 mg) and placebo were assigned to each participant. Doses were taken twice daily for 3 1/2 days followed by FMD and a 4-day washout before proceeding to the next dosing period. Results Twenty-one prehypertensive or mildly hypertensive adults completed the study. There was no evidence of a dose-response effect for our main outcome (FMD percent) or any of our secondary outcomes (absolute change in brachial artery diameter and blood pressure). Most participants indicated that if given evidence that hawthorn could lower their blood pressure, they would be likely to use it either in conjunction with or instead of lifestyle modification or anti-hypertensive medications. Conclusion We found no evidence of a dose-response effect of hawthorn extract on FMD. If hawthorn has a blood pressure lowering effect, it is likely to be mediated via an NO-independent mechanism. Trial Registration This trial has been registered with ClinicalTrials.gov, a service of the U.S. National Institutes of Health: NCT01331486.

2012-01-01

65

New primate genus from the Miocene of Argentina  

PubMed Central

Killikaike blakei is a new genus and species of anthropoid from the late Early Miocene of southeastern Argentina based on the most pristine fossil platyrrhine skull and dentition known so far. It is part of the New World platyrrhine clade (Family Cebidae; Subfamily Cebinae) including modern squirrel (Saimiri) and capuchin monkeys (Cebus) and their fossil relatives known from Early to Middle Miocene and subrecent periods. Living cebines are relatively large-brained, adroit predatory foragers and live within complex social groups, and wild capuchins exhibit a wide range of behaviors associated with enhanced intelligence. We show that K. blakei lacks diagnostic derived characteristics of the lower face and premolar dentition that are shared by modern cebines, but its strongly vaulted frontal bone and capacious anterior cranial fossa indicate the early evolution of an enlarged forebrain.

Tejedor, Marcelo F.; Tauber, Adan A.; Rosenberger, Alfred L.; Swisher, Carl C.; Palacios, Maria E.

2006-01-01

66

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

PubMed Central

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 1981–2010 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.

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

2012-01-01

67

Updated chronology for the Miocene hominoid radiation in Western Eurasia  

PubMed Central

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 (16.3–16.5 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.

Casanovas-Vilar, Isaac; Alba, David M.; Garces, Miguel; Robles, Josep M.; Moya-Sola, Salvador

2011-01-01

68

Nanomechanics and Sodium Permeability of Endothelial Surface Layer Modulated by Hawthorn Extract WS 1442  

PubMed Central

The endothelial glycocalyx (eGC) plays a pivotal role in the physiology of the vasculature. By binding plasma proteins, the eGC forms the endothelial surface layer (ESL) which acts as an interface between bloodstream and endothelial cell surface. The functions of the eGC include mechanosensing of blood flow induced shear stress and thus flow dependent vasodilation. There are indications that levels of plasma sodium concentrations in the upper range of normal and beyond impair flow dependent regulation of blood pressure and may therefore increase the risk for hypertension. Substances, therefore, that prevent sodium induced endothelial dysfunction may be attractive for the treatment of cardiovascular disease. By means of combined atomic force - epifluorescence microscopy we studied the impact of the hawthorn (Crataegus spp.) extract WS 1442, a herbal therapeutic with unknown mechanism of action, on the mechanics of the ESL of ex vivo murine aortae. Furthermore, we measured the impact of WS 1442 on the sodium permeability of endothelial EA.hy 926 cell monolayer. The data show that (i) the ESL contributes by about 11% to the total endothelial barrier resistance for sodium and (ii) WS 1442 strengthens the ESL resistance for sodium up to about 45%. This mechanism may explain some of the vasoprotective actions of this herbal therapeutic.

Peters, Wladimir; Drueppel, Verena; Kusche-Vihrog, Kristina; Schubert, Carola; Oberleithner, Hans

2012-01-01

69

DNA-based discrimination and frequency of phytoplasma infection in the two hawthorn-feeding species, Cacopsylla melanoneura and Cacopsylla affinis, in northwestern Italy.  

PubMed

A molecular tool, focused on the mitochondrial Control Region (CR), was developed to discriminate the two hawthorn-feeding psyllid species, Cacopsylla melanoneura (Förster) and C. affinis (Löw), and to estimate their frequencies in mixed populations. The test was carried out in paired and single-tube amplifications and validated analysing 52 male specimens previously determined by morphological analysis. The frequencies of the two species in mixed populations in the Aosta Valley (northwestern Italy) were analysed. The presence and type of 16SrX-group phytoplasmas was detected by nested PCR and RFLP tests in both species. C. melanoneura was the predominant species (86.5%; 80.4-91.2 CI); of these, 0.9% of the samples were positive for 'Ca. Phytoplasma mali' and 1.8% for 'Ca. Phytoplasma pyri'. One of 21 specimens of C. affinis was positive for 'Ca. Phytoplasma pyri'. The test also allowed us to identify two genetic variants of C. melanoneura, depending on the presence or absence of a 56 bp indel; these were named WI (with indel) and WOI (without indel), respectively. Further analyses were carried out on C. melanoneura specimens collected in apple orchards at six different locations in northern Italy where different levels of transmission efficiency have been described. Our preliminary observations suggest that some differences might exist between the two genetic variants in their ability to transmit phytoplasmas and to colonise different host plants. PMID:20569524

Tedeschi, R; Nardi, F

2010-12-01

70

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

PubMed Central

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.

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

2007-01-01

71

Miocene marine incursions and marine/freshwater transitions: Evidence from Neotropical fishes  

NASA Astrophysics Data System (ADS)

Amazonian rivers contain a remarkable fauna of endemic species derived from taxa that generally occur in oceans and seas. Several hypotheses have been proposed to explain the origin of marine-derived lineages, including opportunistic invasions via estuaries, vicariance related to uplift of the Andes, and vicariance related to Miocene marine incursions and connections. Here, we examine available data for marine-derived lineages of four groups: stingrays (Myliobatiformes), drums (Sciaenidae), anchovies (Engraulididae), and needlefish (Belonidae). Geographic distributions, age estimates (determined using fossils, biogeography, and molecular data sets), and phylogenies for these taxa are most compatible with origination during the Miocene from marine sister groups distributed along the northern coast of South America. We speculate that unique ecological and biogeographic aspects of the Miocene upper Amazonian wetland system, most notably long-term connections with marine systems, facilitated the evolutionary transition from marine to freshwater habitats.

Lovejoy, Nathan R.; Albert, James S.; Crampton, William G. R.

2006-03-01

72

Miocene reef carbonates of Mariana Islands  

SciTech Connect

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.

Siegrist, H.G. Jr.

1988-02-01

73

Shark-bitten vertebrate coprolites from the Miocene of Maryland.  

PubMed

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. PMID:20213300

Godfrey, Stephen J; Smith, Joshua B

2010-05-01

74

Shark-bitten vertebrate coprolites from the Miocene of Maryland  

NASA Astrophysics Data System (ADS)

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.

Godfrey, Stephen J.; Smith, Joshua B.

2010-05-01

75

Geomagnetic Reversals and Crustal Spreading Rates during the Miocene.  

National Technical Information Service (NTIS)

Statistical analysis of the geomagnetic time scale suggests that the rate of reversals was anomalously low during the Miocene. To determine whether undetected reversals actually occurred in the Miocene, 14 magnetic profiles from a survey of the northeast ...

R. J. Blakely

1973-01-01

76

Phenolic constituents and antioxidant capacities of Crataegus monogyna (Hawthorn) callus extracts.  

PubMed

Crataegus (Hawthorn) has long been used as a folk medicine and is widely utilized in pharmaceutical preparations mainly because of its neuro- and cardiosedative actions and its low toxicity. The pharmacological effects of Crataegus have mainly been attributed to the polyphenolic contents. In this study, the production of polyphenols by ten-year-old Crataegus monogyna calli was studied in relation to growth variation and antioxidant capacity within a subculture period. Assays based on the Trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP) and stability in oil-in-water emulsion were used to characterize the antioxidant actions of the callus cultures. High TEAC (3.66 micromol/g dry weight) and FRAP (208.19 micromol Fe2+/g dry weight) values were observed when maximal growth was reached(days 30-35), and this seemed to be influenced by optimum total phenol (47.40 mg/g dry weight), proanthocyanidin (20.81 mg/g dry weight), flavonoid (7.01 mg/g dry weight), anthocyanin (6.18 mg/g dry weight), (-)-epicatechin (1.77 mgl/g dry weight), procyanidin B2 (3.97 mg/g dry weight), and chlorogenic acid (1.11 mg/g dry weight) production during that period. The TEAC values were strongly associated with total flavonoids and to a lesser extent with total phenols, anthocyanins and total proanthocyanidins. The FRAP antioxidant values correlated to total phenols, proanthocyanidins and flavonoids, respectively. The polyphenolic rich calli were as effective as butylated hydroxytoluene (BHT) in preventing hydroperoxide and conjugated diene formation in a 30% oil-in-water emulsion prepared with stripped sunflower oil, during 7days storage at 30 degrees C. Crataegus monogyna cell culture represents an important alternative source for natural antioxidants. PMID:12866623

Bahorun, Theeshan; Aumjaud, Esha; Ramphul, Hemlata; Rycha, Maheshwaree; Luximon-Ramma, Amitabye; Trotin, Francis; Aruoma, Okezie I

2003-06-01

77

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

PubMed Central

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 (?) 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.

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

2010-01-01

78

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

PubMed

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

Lee, Raymond M

2011-01-01

79

A sphenodontine (Rhynchocephalia) from the Miocene of New Zealand and palaeobiogeography of the tuatara (Sphenodon)  

PubMed Central

Jaws and dentition closely resembling those of the extant tuatara (Sphenodon) are described from the Manuherikia Group (Early Miocene; 19–16 million years ago, Mya) of Central Otago, New Zealand. This material is significant in bridging a gap of nearly 70 million years in the rhynchocephalian fossil record between the Late Pleistocene of New Zealand and the Late Cretaceous of Argentina. It provides the first pre-Pleistocene record of Rhynchocephalia in New Zealand, a finding consistent with the view that the ancestors of Sphenodon have been on the landmass since it separated from the rest of Gondwana 82–60?Mya. However, if New Zealand was completely submerged near the Oligo-Miocene boundary (25–22?Mya), as recently suggested, an ancestral sphenodontine would need to have colonized the re-emergent landmass via ocean rafting from a currently unrecorded and now extinct Miocene population. Although an Early Miocene record does not preclude that possibility, it substantially reduces the temporal window of opportunity. Irrespective of pre-Miocene biogeographic history, this material also provides the first direct evidence that the ancestors of the tuatara, an animal often perceived as unsophisticated, survived in New Zealand despite substantial local climatic and environmental changes.

Jones, Marc E.H.; Tennyson, Alan J.D.; Worthy, Jennifer P.; Evans, Susan E.; Worthy, Trevor H.

2009-01-01

80

The Effect of Group Counseling upon the Classroom Behavior and on the Manifest Anxiety of Elementary School Student Teachers. Final Report.  

ERIC Educational Resources Information Center

This study assesses the effectiveness of a group counseling treatment on the classroom behaviors and on the manifest anxiety levels of elementary school student teachers. The subjects were 44 volunteer student teachers, randomly assigned to three groups: 1) an experimental counseling group, 2) a Hawthorne seminar control group, and 3) a control…

Eder, Sidney Charles

81

Miocene sediments distribution in the central and northern parts of the Vienna Basin, central Europe  

NASA Astrophysics Data System (ADS)

The Vienna Basin is a Miocene sedimentary basin situated at the Alpine-Carpathian transition and spreading from Austria in the South to the Czech Republic and Slovakia in the north. The basin primarily developed as a piggy-back basin during the Lower Miocene (~18 - 16 Ma) on top of the NW-ward moving Eastern Alpine and West Carpathians thrust sheets. In the late Lower Miocene, the local stress regime changed by the lateral extrusion of the Eastern Alps towards the Pannonian area. It leads to the developing of the basin between two left stepping sinistral strike-slip faults of the Vienna Basin faults system during the Middle and Upper Miocene (~16 - 8 Ma). Structures related with this pull-apart stage are extensional sinistral strike-slip duplexes connected with large scale listric normal fraults. Our study area mainly covers the central and northern Vienna Basin that is not yet studied well for the stratigraphy. The goal of this study is the characterization and distribution of the Miocene sediments. For this purpose we investigated approximately 200 wells in 17 well-groups in order to obtain details on the Miocene sediments. Among them 84 wells drilled down to the Northern Calcareous Alps and the flysch units in the pre-Neogene basin subcrop. The initial phase of the Miocene deposition was related to the transgression and is characterized by the deposition of coarse clastic and marly clay sediments. These sediments are distributed locally in the northern part of the basin. The overlying sediments are more widely distributed than the underlying ones. During the late Lower Miocene, the depocenters shifted towards the south and sedimentation was dominated by marly clay intercalated with sand. An unconformity depicted for the regional stage boundary fits well with the regressive phase and the subsequent transgression. From Middle to Upper Miocene, sediments were deposited over a wide area of the Vienna Basin. The sedimentation was governed by combination of pull-apart kinematics, eustatic global sea-level changes and sediment supply mostly from deltas. Figure 1. Tectonic sketch map of the Vienna Basin and location of studied area.

Lee, E.; Wagreich, M.; Decker, K.

2012-12-01

82

Aquifer characteristics and water quality of Miocene–Pleistocene sediments, Kuwait  

Microsoft Academic Search

Al-Atraf is one of the water well fields of Kuwait supplying Kuwait City with the brackish groundwater obtained from the Kuwait Group aquifer of Miocene–Pleistocene age. The study determined the hydrogeological and hydrochemical characteristics of the groundwater in order to identify the major chemical processes that influence the groundwater quality of the study area. The results of the aquifer test

F. M. Al-Ruwaih; H. A. Qabazard

2005-01-01

83

Miocene reef carbonates of Mariana Islands  

SciTech Connect

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.

Siegrist, H.G. Jr.

1988-01-01

84

Murky details of the Miocene Atlantic Ocean  

NASA Astrophysics Data System (ADS)

We examine Atlantic Ocean circulation during the Miocene based on published modelling and data. It has long been recognised that the Atlantic Ocean played a key role in climate changes throughout the Quaternary and determining whether this was the case earlier in the Cenozoic may be important for understanding the details of Miocene climate evolution. Current geochemical, sedimentological and micropaleontologic evidence allows for multiple interpretations of deep water activity, which is further hampered by a lack of precise dating of ocean gateway closures. Previous ocean modelling studies have shown strong increases in deep water formation due to closure of the Panama gateway but have disagreed on the oceanographic importance of the Tethys gateway and bathymetry of the far North Atlantic. This combination of ambiguous data and conflicting modelling results leaves the current state of knowledge of the Miocene ocean lacking. We propose several avenues of research to improve our knowledge of the Miocene Atlantic Ocean, which will ultimately improve our understanding of its response to climate change and vice versa.

Herold, N. K.; Huber, M.; Shevenell, A.; Müller, D.

2013-12-01

85

The new LOCI digoxin assay on the Vista 1500 analyzer is virtually free from interferences of herbal supplements hawthorn and ashwagandha (Indian ginseng).  

PubMed

Herbal supplements hawthorn and ashwagandha (Indian ginseng) are indicated for cardiac illnesses and may be taken by patients receiving digoxin therapy. Because both hawthorn and ashwagandha are known to interfere with serum digoxin measurements using certain digoxin immunoassays, we investigated potential interference of these two herbal supplements with the new homogenous sequential chemiluminescent assay for digoxin based on the luminescent oxygen channeling technology (LOCI digoxin) for application on the Dimension and Vista platform. When aliquots of a drug-free serum pool were supplemented with various amounts of hawthorn (three different commercial preparations) or ashwagandha (two different commercial preparations) and apparent digoxin values were measured using LOCI digoxin assay on Dimension Vista 1500 analyzer we observed none-detected values except when aliquots were supplemented with very high amounts of the herbal extracts. When aliquots of a serum digoxin pool (prepared by pooling specimens from patients receiving digoxin) where further supplemented with various amounts of these supplements and digoxin concentrations were remeasured, statistically significant falsely higher digoxin values were observed only in specimens containing very high amounts of these supplements. Such interference may not be clinically significant. We conclude that new LOCI digoxin assay is virtually free from interferences of herbal supplements, hawthorn, and ashwagandha. PMID:22811353

Dasgupta, Amitava; Johnson, Myrtle J; Wahed, Amer

2012-07-01

86

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

NASA Astrophysics Data System (ADS)

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.

Metzger, C. A.

2013-12-01

87

Global Miocene tectonics and the modern world  

NASA Astrophysics Data System (ADS)

An amazing congruence of seemingly unrelated, diverse global events began in the Middle and Upper Miocene and established our modern world. Two global orogenic belts were active, mostly in the Middle and Upper Miocene, while backarc basins formed along the eastern margin of Asia. Coincident with these events global temperatures cooled in both the ocean and atmosphere, desertification occurred from Central Asia into and across most of northern Africa and also in Australia, and in southern South America. Coincident with the expansion of the Antarctic ice cap at 14 Ma, there was initial widespread deep sea erosion and changes in patterns of deep sea sedimentation. Muddy pelagic sedimentation increased six-fold in the North and Central Atlantic and Pacific Oceans and global changes in circulation lead to more diatomites in the Pacific and fewer in the Atlantic. By the end of the Miocene most of the Mediterranean Sea had evaporated. Broadly coincident with these events, many old, large river systems were destroyed and new ones formed as much of the world's landscape changed. Collectively, these global on-shore tectonic and ocean-atmospheric events provide the foundation for our modern world—a mixture of new and rejuvenated orogenic belts and their far-field effects (distant epiorogenic uplift, rain-shadow deserts, large alluvial aprons, and distant deltas) as inherited Gondwanan landscapes persisted remote from plate boundaries. Thus at the end of the Miocene much of the world's landscape, except for that changed by Pleistocene continental glaciation, would be recognizable to us today. We argue that all of these events had the same ultimate common cause-an internal Earth engine-that drove plate motions in two broad ways: first, the opening and closing of seven key gateways to deep-water oceanic currents radically altered global heat transfer and changed a lingering Greenhouse to an Icehouse world; secondly, these events were in part coincident with renewed heat flow in the African and Pacific Superplumes that energized global plate motions in the Middle and Upper Miocene. We hope this global synthesis will stimulate more research on the many global events of the Miocene—to understand better both our modern world and earlier global orogenies.

Potter, Paul Edwin; Szatmari, Peter

2009-11-01

88

The westernmost tarsier: a new genus and species from the Miocene of Pakistan.  

PubMed

As the closest living sister group of anthropoids, tarsiers (Family Tarsiidae) are an important group in primate evolution. However, their fossil record is poor: only four species have been described, two from the Eocene of China and two from the Miocene of Thailand. All are from outside the range of the living species, which occur only on islands off Southeast Asia. Here, we describe a new fossil tarsier from Pakistan, a significant range extension. This record consists of two lower molars, an upper molar, and a lower premolar found in the Miocene Manchar Formation (~18-16 Ma [millions of years ago]) of Sindh Province, southern Pakistan. The Pakistani tarsier is morphologically distinct from all living and fossil tarsiers, but most similar to the middle Miocene Thai species Tarsius thailandicus. Though living tarsiers have traditionally been classified in a single genus, a recent revision proposed a division into three genera, which is strongly supported by molecular data. The Pakistani species is not referable to any of these genera, and we create for it and T. thailandicus a new tarsiid genus. This discovery broadens our understanding of the geographic range and morphological diversity of Miocene tarsiers and helps to put the living tarsiers into their evolutionary context. PMID:23928350

Zijlstra, Jelle S; Flynn, Lawrence J; Wessels, Wilma

2013-11-01

89

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

PubMed Central

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.

Moya-Sola, Salvador; Alba, David M.; Almecija, Sergio; Casanovas-Vilar, Isaac; Kohler, Meike; De Esteban-Trivigno, Soledad; Robles, Josep M.; Galindo, Jordi; Fortuny, Josep

2009-01-01

90

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)

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

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

2008-12-01

91

Late Oligocene-Early Miocene thrusting in southern East Kunlun Mountains, northern Tibetan plateau  

Microsoft Academic Search

Southward thrusting occurred in Late Oligocene-Early Miocene in southern East Kunlun (??) Mountains formed the South Kunlun\\u000a thrust (SKT). Permian strata and Triassic rocks were thrusted over the Paleocene-Eocene red-beds of Fenghuoshan (???) Group\\u000a and Oligocene brownish red conglomerate and sandstone of Yaxicuo (???) Group along SKT faults, formed tectonic slices, low-angle\\u000a thrust faults, multi-scaled outliers, and nappe structures in

Zhenhan Wu; Peisheng Ye; Barosh J. Patrick; Daogong Hu; Wenjin Zhao; Zhonghai Wu

2009-01-01

92

Grouping  

NSDL National Science Digital Library

This interactive Flash applet models the measurement interpretation of division. A child or teacher chooses a total number of objects and a divisor representing the size of equal groups. The applet allows the user to move the objects into equal groups and links the process to jumps on a number line. The applet can be used to introduce children to remainders and to reinforce the language and notation of division. It works well on an interactive white board or projector. A teacher's guide to this collection of applets is cataloged separately.

2006-01-01

93

Miocene mass-transport sediments, Troodos Massif, Cyprus  

USGS Publications Warehouse

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.

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

2009-01-01

94

Miocene paleotopography of the Central Alps  

NASA Astrophysics Data System (ADS)

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.

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

2012-07-01

95

Petrogenesis of the Miocene volcanism along the ?zmir-Bal?kesir Transfer Zone in western Anatolia, Turkey: Implications for origin and evolution of potassic volcanism in post-collisional areas  

NASA Astrophysics Data System (ADS)

The Miocene volcanic rocks along the ?zmir-Bal?kesir Transfer Zone along the western margin of the Menderes Core Complex (MCC) in western Anatolian Volcanic Province (WAVP), where strike-slip deformation is dominant, comprise: (Group 1) early-middle Miocene high-K to shoshonitic rocks with high-Mg# and relatively low SiO2, (Group 2) middle Miocene phonolitic rocks with low-Mg# and intermediate SiO2, (Group 3) early-middle Miocene medium- to high-K series from andesites to rhyolites, (Group 4) middle Miocene rhyolites with distinct trace element compositions; and (Group 5) late Miocene high-MgO basalts, K-trachybasalts and (Group 6) late Miocene high-MgO basaltic andesites. The geochemical features of these rocks are comparable with the other Oligocene to Miocene volcanic rocks, but differ from the Eocene volcanic rocks in WAVP. The geochemical features of the most primitive early-middle Miocene Group 1 rocks indicate that they were derived from an anomalously metasomatized lithospheric mantle. The mineralogical and geochemical properties of garnet-amphibole peridotite from the Ulten Zone (UZP), Eastern Alps, which is thought to represent a fossil metasomatic mantle wedge contaminated by continental subduction, is similar to the model mantle composition previously proposed for the genesis of the mafic rocks. Together with the presence of Eocene to early Miocene continental subduction beneath the Aegean-west Anatolia region, this strongly suggests that continental subduction was an important factor in the genesis of the high-MgO shoshonitic to ultrapotassic volcanism in this post-collisional area. The origin of the Group 3 andesitic to rhyolitic rocks includes; (1) lower crustal melting, (2) mixing between lower crustally-derived and mantle-derived melts, and (3) FC-AFC processes. The late Miocene Group 5 and 6 rocks, however, derived from a more depleted mantle source, indicating that the mantle became depleted over time. The rhyolites of Group 4 are most probably crustally-derived. OIB-type Quaternary Kula volcanics (QKV) were emplaced near the centre of the MCC. Among the late Miocene basalts in the region, only the basalts located close to the QKV show transitional geochemistry between the Miocene volcanic rocks and QKV, indicating that asthenospheric contribution to lavas in the region occurred only near the centre of the MCC.

Ersoy, Yalç?n E.; Helvac?, Cahit; Uysal, ?brahim; Karao?lu, Özgür; Palmer, Martin R.; Dindi, Fulya

2012-10-01

96

Molluscan radiations and landscape evolution in Miocene Amazonia  

Microsoft Academic Search

This PhD study aims to exploit the rich archive provided by the Miocene mollusc fauna of the Pebas Formation and other inland Miocene Amazonian formations to reconstruct landscape evolution and biotic development in lowland Amazonia during the Neogene. Over 160 samples from more than 70 Pebas Formation outcrops mostly collected by the author were processed for this study. Additional samples

F. P. Wesselingh

2008-01-01

97

Miocene sequence biostratigraphy of the northern Gulf of Mexico  

Microsoft Academic Search

The Miocene floral pulse model of Jiang and Watkins is revised. The new revision suggests that the Gulf of Mexico Miocene floral pulses, corresponding to the traditional foraminiferal tops, are transgression surfaces of the fourth-order sequences. These pulses show diverse magnitudes and when they are plotted on a depth (or time) tract, their relative magnitudes show an orderly wavy pattern

1993-01-01

98

Highly magnetic Upper Miocene sandstones of the San Francisco Bay area, California  

Microsoft Academic Search

A high-resolution aeromagnetic survey of the San Francisco Bay area shows prominent positive anomalies over distinctive blue sandstones of Late Miocene age. The total-field survey was measured at a nominal height of 300 m above the land surface along flight lines spaced 0.5 km apart. Anomalies with amplitudes up to 200 nT correlate with sandstones of the San Pablo Group,

John W. Hillhouse; Robert C. Jachens

2005-01-01

99

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

USGS Publications Warehouse

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.

Quinones-Aponte, Vicente; Wexler, Eliezer J.

1995-01-01

100

Paleomagnetic evidence for the Miocene counter-clockwise rotation of Northeast Japan-rifting process of the Japan arc  

Microsoft Academic Search

Paleomagnetic results have been obtained from more than 700 oriented samples in igneous rocks of Cretaceous to Miocene age from Northeast Japan. The remanent magnetizations of welded tuffs with age between 32 Ma and 21 Ma old from 17 widely distributed sampling sites in Northeast Japan are fairly well grouped with a mean of D = -41.2°, I = 56.5°,

Yo-Ichiro Otofuji; Takaaki Matsuda; Susumu Nohda

1985-01-01

101

Paleomagnetic directional dispersion produced by plastic deformation in a thick Miocene welded tuff, southern Nevada: Implications for welding temperatures  

Microsoft Academic Search

Two voluminous rhyolitic to quartz-latitic ash flow sheets, the Tiva Canyon and Topopah Spring members of the Paintbrush Tuff, were erupted from the Miocene Claim Canyon cauldron in southern Nevada. Although lithologically similar, these units differ greatly in their recording of the ancient geomagnetic field. The reversely magnetized Tiva Canyon Member yields remanent directions that are well grouped both within

J. G. Rosenbaum

1986-01-01

102

Fossil Woodwardia virginica Foliage From the Middle Miocene Yakima Canyon  

NSDL National Science Digital Library

Fossil Woodwardia virginica foliage from the middle Miocene Yakima Canyon flora of central Washington State, USA. Vegetative and fertile features of this fossil are remarkably similar to those of the modern ""Virginia chain fern"" of the Atlantic coastal region, USA.

Kathleen B. Pigg (Arizona State University;Department of Plant Biology ADR;POSTAL)

2004-03-09

103

Oceanographic Significance of Pacific Late Miocene Calcareous Nannoplankton.  

National Technical Information Service (NTIS)

An analysis of the variability in the composition and distribution of Pacific Late Miocene calcareous nannoplankton about their average biogeography shows that there are primarily two environmental factors causing that variability, climate and dissolution...

G. P. Lohmann J. J. Carlson

1980-01-01

104

Sepiolite Associated with Miocene Diatomite, Santa Cruz Basin, California.  

National Technical Information Service (NTIS)

Sepiolite has been found as veinlets in Middle Miocene diatomite recovered in a dredge haul made on the southeast wall of Santa Cruz Basin, California Continental Borderland. The sepiolite is moderately well crystallized and of normal chemical composition...

P. Fleischer

1971-01-01

105

Paleofaunal and Environmental Research on Miocene Fossil Sites TVOR SE and TVOR S on Fort Polk, Louisiana, with Continued Survey, Collection, Processing, and Documentation of other Miocene Localities.  

National Technical Information Service (NTIS)

Focus of paleontological research on the Miocene of Fort Polk is currently the marine locality TVOR SE, which also has yielded large and small terrestrial Miocene vertebrates, and a single Cretaceous dinosaur tooth, reworked from older beds outside the lo...

J. A. Schiebout S. Ting M. Williams G. Boardman W. Gose

2004-01-01

106

Geomagnetic Reversals and Crustal Spreading Rates During the Miocene  

Microsoft Academic Search

Statistical analysis of the geomagnetic time scale suggests that the rate of reversals was anomalously low during the Miocene. To determine whether undetected reversals actually occurred in the Miocene, 14 magnetic profiles from a survey of the northeast Pacific by NOAA are analyzed by signal-averaging techniques. The data suggest that during the time period 7.3 to 22.7 m.y., eight short-wavelength

Richard J. Blakely

1974-01-01

107

Miocene upwelling events: Neritic foraminiferal evidence from southern Australia  

Microsoft Academic Search

The neritic stratigraphic section in the Lakes Entrance oil shaft in Gippsland, Victoria, southeastern Australia, records four major upwelling events at the third?order or 10 years scale. The first and second occurred during the Janjukian (latest Oligocene to Early Miocene; at about 24.5 and 22 Ma); the third in the late Longfordian (late Early Miocene; 17.5–17 Ma); and the fourth

Q. Li; B. McGowran

1994-01-01

108

Biomarkers challenge early Miocene loess and inferred Asian desertification  

NASA Astrophysics Data System (ADS)

Fine-grained Miocene sediments from Tianshui Basin, northeastern Tibetan Plateau, have received intense attention recently because these sediments were identified as loess. The presence of early Miocene loess pushes the timing of initiation of inland Asian desertification from 8 Ma back to 22 Ma. However, mudflat/distal fan and shallow lake sediments of Miocene have also been reported in Tianshui Basin. Consequently, the origin of these fine-grained Miocene sediments in this area remains controversial. Here we investigate the n-alkane biomarker characteristics of Neogene sediments from a north-south transect of exposures within Tianshui Basin and compare these molecular distributions with those published Quaternary loess to help resolve the disputed origin. We found that n-C23 and n-C25 alkanes, sourced from either aquatic macrophytes or palustrine plants, are ubiquitous in the Miocene sediments from Tianshui Basin but are largely absent in Quaternary loess. This striking difference between n-alkane distributions in the Tianshui samples and the Quaternary loess casts doubt on an eolian origin for the Tianshui samples and challenges the hypothesis of an early Miocene onset of Asian interior desertification.

Peng, Tingjiang; Li, Jijun; Song, Chunhui; Zhao, Zhijun; Zhang, Jun; Hui, Zhengchuang; King, John W.

2012-03-01

109

Oligocene early Miocene Antarctic nearshore diatom biostratigraphy  

NASA Astrophysics Data System (ADS)

Lower Oligocene (ca. 31 Ma) to lower Miocene (ca. 18.5 Ma) biosiliceous microfossils recovered from the Cape Roberts Project (CRP-2/2A) drill cores provide both paleoenvironmental and biostratigraphic information, enhancing our understanding of the geological history of the Victoria Land Basin, Antarctica. The biochronostratigraphic record obtained provides key data with which time-space-facies models may be developed. Assemblages of neritic and pelagic microfossils such as those from the CRP-2/2A drill cores provide links between the primarily pelagic microfossil-derived chronostratigraphy of the Southern Ocean and the facies models of the neritic zone. The CRP-2/2A holes drilled in the Victoria Land Basin, Antarctica during 1998 [Barrett, P.J., et al. (Eds.), 2001. Studies from the Cape Roberts Project, Ross Sea, Antarctica, Scientific Results of CRP-2/2A, Parts I and II: Terra Antartica, vol. 7(4/5), 665pp] include several sections that contain well-preserved and relatively abundant biosiliceous microfossils. Scherer et al. [2001. Oligocene and Lower Miocene Siliceous Microfossil Biostratigraphy of Cape Roberts Project Core CRP-2/2A, Victoria Land Basin, Antarctica. In: Barrett, P.J., Ricci, C.A. (Eds.) Studies from the Cape Roberts Project, Ross Sea, Antarctica, Scientific Report of CRP-2/2A, Terra Antartica, vol. 7(4), pp. 417-442] produced a biostratigraphic zonal framework consisting of 10 biozones; two of the zonal boundaries were correlated with the magnetostratigraphically calibrated Southern Ocean diatom biozonation. Many of the taxa observed and utilized in the above framework could not be assigned categorically to existing taxa, leading to use of informal nomenclature. We present an updated biostratigraphy and zonation scheme based on the latest taxonomic concepts and on new quantitative and qualitative siliceous microfossil data from the CRP-2/2A drill core, including formal description of four new diatom taxa used in the definition of Antarctic nearshore diatom zonal boundaries. New taxa formally proposed are Fragilariopsis truncata, Cymatosira palpebraforma, Rhizosolenia fidicularis, and Hemiaulus angustobrachiatus.

Olney, Matthew P.; Scherer, Reed P.; Harwood, David M.; Bohaty, Steven M.

2007-10-01

110

Miocene reef facies of Pelagian Block, central Mediterranean  

SciTech Connect

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.

Pedley, H.M.

1988-01-01

111

Marine Biotic Responses to Miocene Climate Change  

NSDL National Science Digital Library

This activity is part of a collection under development by participants in a June 2006 workshop. Tested versions will be available in Spring 2007. During the Miocene the Earth plunged into its present "icehouse" state, with glaciers at North and South Poles. In this activity, students investigate biotic responses to this climate change using microfossil data from the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP). These data are analyzed and displayed using the CHRONOS information technology system, building information technology skills while strengthening understanding of biostratigraphic principles. The activity integrates geochemical and biotic data, reinforcing the notion that understanding Earth History requires a multidisciplinary approach. Students use Time Scale Creator to examine how sediments are correlated and dated. DSDP and ODP core data in the Neptune database is used to create age-distribution histograms for foraminifers and calcareous nannofossils, and compare these data to the record of climate change based on oxygen isotope analyses. Students synthesize and compare their discoveries regarding marine microfossil responses to global climate change, and evaluate the assumptions and biases inherent in these results. Step-by-step instructions for using the CHRONOS interface are provided, formatted as a student handout. References to related primary literature are included, and may be used to adapt the exercise for more advanced undergraduates or graduate students.

Grossman, Ethan; Mccarville, Katherine; Clark, Kendra; Hemmesch, Nikki T.

112

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)

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.

Böhme, M.; Ilg, A.; Ossig, A.; Küchenhoff, H.

2006-06-01

113

Late Miocene “washhouse” climate in Europe  

NASA Astrophysics Data System (ADS)

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 Ceará 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.

Böhme, Madelaine; Ilg, August; Winklhofer, Michael

2008-11-01

114

A molecular organic carbon isotope record of miocene climate changes  

SciTech Connect

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.

Schoell, M. (Chevron Petroleum Technology Co., La Habra, CA (United States)); Schouten, S.; Sinninghe Damste', J.S.; Leeuw, J.W. de (Netherlands Institute of Sea Research, Texel (Netherlands)); Summons, R.E. (Australian Geological Survey Organization, Canberra (Australia))

1994-02-25

115

The Late Miocene climate response to a modern Sahara desert  

NASA Astrophysics Data System (ADS)

The climate cooling and vegetation changes in the Miocene/Pliocene are generally well documented by various proxy data. Some important ecosystem changes occurred at that time. Palaeobotanical evidence suggests that the Sahara desert first appeared in the Pliocene, whereas in the Miocene North Africa was green. In the present study, we investigate the Late Miocene climate response to the appearance of the Sahara desert from a climate modelling sensitivity experiment. We compare a model experiment, which includes a full set of Late Miocene boundary conditions, with another one using the same boundary conditions except that the North African vegetation refers to the present-day situation. Our sensitivity study demonstrates that the introduction of the Sahara desert leads to a cooling and an aridification in Africa. In addition, we observe teleconnection patterns related to the North African desertification at around the Miocene/Pliocene boundary. From our sensitivity experiment, we observe that the Sahara contributes to a cooling in Central Asia and in North America. As compared to hypsodonty data for Central Asia, an increased aridity is underestimated in the Sahara experiment. Finally, we observe that the introduction of the Sahara leads to a cooling in the northern high latitudes. Hence, our sensitivity experiment indicates that the appearance of the Sahara desert is one piece to better understand Late Cenozoic climate cooling being most pronounced in the high latitudes.

Micheels, Arne; Eronen, Jussi; Mosbrugger, Volker

2009-06-01

116

Miocene isotope chronostratigraphy: North-central Gulf of Mexico  

SciTech Connect

Isotope chronostratigraphy has proven extremely useful in providing high resolution stratigraphic correlations and detailed information relating to the complex nature of sediment accumulation rates in Plio-Pleistocene exploration wells of the north-central Gulf of Mexico (GOM). Current research on the isotopic composition of foraminifera recovered from Miocene age sediments in the north-central GOM indicate that the glacio-eustatic cycles documented in the Plio-Pleistocene are found to continue into the late Miocene. During the middle Miocene ample isotopic signals (3 per mil) exist to provide a high resolution stratigraphy. {delta}{sup 18}O data from the planktonic foraminifera Orbulina universa from Eureka core 66-73 in the Desoto Canyon form a relatively complete record from approximately 8.5-16 Ma. The record displays a greater than 3 per mil range in {delta}{sup 18}O values through the middle Miocene. This Miocene {delta}{sup 18}O record from E66-73 is compared to exploration wells from the following areas: Mississippi Canyon, central GOM, East Breaks, South Galveston, and the Green Canyon. In the downdip, deeper water sections, the primary water column signal appears to be well preserved through the middle Miocene. When working updip in shallower water depths, there appears to be some diagenetic zones displaying extremely negative {delta}{sup 18}O values ({gt}-6 per mil) that could be related to fluid migration events or possibly related to sand occurrence. Also found in these updip wells is a zone of consistent diagenetic overprint in the lower section of the well. In this interval, the base line for the {delta}{sup 18}O values is shifted by as much as 3-4 per mil in the negative direction.

Trainor, D.M.; Williams, D.F. (Univ. of South Carolina, Columbia (United States))

1991-03-01

117

Seismic geomorphology and growth architecture of a Miocene barrier reef, Browse Basin, NW-Australia  

Microsoft Academic Search

The Cenozoic succession of Browse Basin is characterized by a carbonate system, that developed from a non-tropical ramp in Eocene-lower Miocene times to a tropical rimmed platform in the middle Miocene. The evolution of the platform was unraveled through the interpretation of the seismic geomorphology and borehole data of the middle Miocene tropical reef system. The first reef structures developed

Beke Rosleff-Soerensen; Lars Reuning; Stefan Back; Peter Kukla

118

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

NASA Astrophysics Data System (ADS)

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).

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

2012-04-01

119

ARTICLE Miocene hominoid biogeography: pulses of dispersal and differentiation  

Microsoft Academic Search

Aim To test the hypothesis that the ancestor of the hominines (African apes and humans) had an African origin by comparing the historical biogeographical patterns of hominoids with those of two other large land mammal clades, namely the hyaenids and proboscideans. Location Global, primarily the Old World over the last 25 Myr (Miocene to present). Methods Creation of a general

Kaila E. Folinsbee; Daniel R. Brooks

120

Benthic foraminifera of a Miocene canyon and fan  

Microsoft Academic Search

We present benthic foraminiferal assemblage data from an exhumed Miocene canyon and fan system from the Tabernas Basin (SE Spain). The presence of good indicator taxa and unique assemblages occupying specific environments allows the distinction of slope, canyon and fan environments within the Tabernas Basin by foraminiferal assemblages alone. Five assemblages are defined on the basis of the occurrence of

M. Rogerson; T. J. Kouwenhoven; G. J. van der Zwaan; B. J. O'Neill; C. J. van der Zwan; G. Postma; K. Kleverlaan; H. Tijbosch

2006-01-01

121

Flavonoids and other chemical constituents of fossil miocene zelkova (ulmaceae).  

PubMed

Organic solvent extractions of Zelkova oregoniana, a Miocene angiosperm compression fossil, indicate the chemical preservation of kaempferol, dihydrokaempferol, an n-alkane chain length range of 10 to 32 carbons, hydroxy acids, steranes, triterpenoids, and methyl pheophorbide a. This appears to be the oldest occurrence of flavonoids in fossil sediments reported. PMID:17821805

Niklas, K J; Giannasi, D E

1977-05-20

122

A new crane (Aves: Gruidae) from the Miocene of Germany  

Microsoft Academic Search

Described here is a new fossil species of crane (Aves: Gruidae), Palaeogrus mainburgensis, sp. nov., from the early middle Miocene fossil site of Sandelzhausen in Bavaria, southern Germany. The study includes morphological and metric comparisons with all known Tertiary gruids from Eurasia, along with a discussion of the taxonomic distribution of morphological characters in fossil gruids. The new species is

Ursula B. Göhlich

2003-01-01

123

Oligocene and Miocene arc volcanism in northeastern California  

NASA Astrophysics Data System (ADS)

The Warner Range in northeastern California exposes over 3 km of Tertiary rocks and offers a unique opportunity to study the long-term history of Cascade arc volcanism in an area typically covered by younger lavas. The oldest locally-sourced volcanic rocks in the Warner Range are Oligocene (26-30 Ma) and include a sequence of basalt and basaltic andesite lava flows overlain by hornblende and pyroxene andesite pyroclastic flows and minor lava flows. Both sequences vary in thickness (0-1 km) along strike and are inferred to be the erosional remnants of one or more large, partly overlapping composite volcanoes, possibly derived from the same magma chamber. A largely amagmatic period lasted from about 25-16 Ma, although distally-derived silicic tuffs were deposited in the region during this time. Arc volcanism resumed at about 16 Ma with basalt and basaltic andesite lavas sourced from local eruptive centers 5-10 km south of the relict Oligocene centers. Post-16 Ma volcanism continued into the late Miocene and Pliocene, forming numerous eroded but well-preserved shield volcanoes to the west and south of the Warner Range. Geochemically, Oligocene through late Miocene volcanic rocks in and around the Warner Range are calc-alkaline basalts to andesites (48-61% SiO2) that display negative Ti, Nb, and Ta anomalies consistent with an arc setting. Middle Miocene lavas in the Warner Range are distinctly different from the Steens Basalt (with which they were previously correlated), which has higher Ti, lower Al, and flatter REE patterns. Middle to late Miocene shield volcanoes west of the Warner Range consist of homogenous basaltic andesites (53-57% SiO2) that are geochemically similar to older rocks in the Warner Range. They are distinctly different from younger (late Miocene to Pliocene) high-Al, low-K olivine tholeiites, which are more mafic (46-49% SiO2), did not build large edifices, and are thought to be related to back-arc extension. The Warner Range is about 100 km east of the axis of the modern arc in northeastern California, suggesting that the arc was either more broad in the middle Miocene, or migrated west during the late Miocene due to a change in dip of the subducting slab.

Colgan, J.; Egger, A.; John, D.

2008-12-01

124

The early to mid-Miocene environment of Antarctica  

NASA Astrophysics Data System (ADS)

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.

Ashworth, A. C.; Lewis, A.

2012-12-01

125

Miocene terrestrial climate of southern New Zealand from floral proxies  

NASA Astrophysics Data System (ADS)

Southern New Zealand is situated in the mid-latitude south-west Pacific near the convergence zone of the Sub-Antarctic Front and the Subtropical Front. Climate records from this region are therefore of considerable importance for the understanding of the development of the Antarctic Ice Sheet and the consequences of the possible future retreat of the West Antarctic Ice Sheet. Well-preserved, diverse floral assemblages from several Miocene lake deposits have been discovered in southern New Zealand: they include one from the Aquitanian (23 Ma), two from the Burdigalian (16-18 Ma) and two from the Serravallian-Early Tortonian (10-12 Ma). Climatic proxies such as Climate Leaf Analysis Multivariate Program (CLAMP) and Bioclimatic Analysis provide a robust framework with which to reconstruct the terrestrial climate of southern New Zealand through the Miocene. CLAMP employs a set of physiognomic characteristics of fossil leaves and correlates these with a large physiognomic dataset of modern floral collections and associated climate variables. Bioclimatic Analysis is a mutual climate range method using the climatic envelopes of the nearest living relatives of a fossil flora to determine the climatic range in which the flora could co-occur. It employs a comprehensive dataset of modern living taxa of the major floral components from Australia, New Zealand and New Caledonia. New Zealand was a low-lying landmass throughout the Miocene, most likely of a comparable size to modern day New Zealand. Most floral assemblages were deposited close to sea-level and climate would have been regulated by the surrounding ocean. Subtropical climatic conditions prevailed throughout the Early and Middle Miocene with mean annual temperatures (MAT) around 18-20°C and precipitation rates at around 1500-2000 mm-yr. By comparison modern day coastal southern New Zealand has a MAT of between 8-10°C and annual precipitation ranges from 600-900 mm-yr on the east coast, to well over 4000 mm-yr on the southwest coast. The temperature difference between summer and winter in the Early to Middle Miocene was less than 10°C. Towards the Late Miocene, the MAT dropped to around 15°C and the temperature during the cold season was significantly cooler, with a cold month mean of ~13-14°C in the Early and Middle Miocene and ~6°C in the Late Miocene; close to modern day New Zealand winter temperatures. Precipitation rates remained the same at around 1500-2000mm-yr. The development of the West Antarctic Ice Sheet in the Miocene was the main driver that pushed the Sub-Antarctic Front northward, while southern New Zealand's latitudinal position remained stable at close to 45°S. Antarctic southerlies would not have played a role in New Zealand's climatic system during the Early and Middle Miocene, when the average temperature of the coldest months very rarely dropped below 10°C. By the Tortonian, Antarctic southerlies would have played a significant role in cooling southern New Zealand during winter.

Reichgelt, T.; Kennedy, E.; Conran, J. G.; Lee, D.

2013-12-01

126

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

USGS Publications Warehouse

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.

Drobniak, A.; Mastalerz, M.

2006-01-01

127

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

NASA Astrophysics Data System (ADS)

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 ?13C 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 ?13C 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.

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

2009-10-01

128

Paleosecular variation record of geomagnetic full vector during late Miocene, from the Nayarit area, Mexico  

NASA Astrophysics Data System (ADS)

We have sampled a sequence of 45 late Miocene consecutive lava flows in the Tepic area (Nayarit State, Mexico). The age of the volcanic units lies between 8 and 9 million years (Ma) according to available radiometric data. All samples were stepwise demagnetized, partly with alternating field (AF), partly thermally with very similar results. Most of the rocks exhibited well-defined one component remanent magnetisation with high unblocking temperatures (mostly above 525 °C) and high median destructive fields (MDF) (40-50 mT). Rock-magnetic experiments combined with microscopy show that, in most cases, the main magnetic mineral is Ti-poor titanomagnetite associated with exsoluted ilmenite. Continuous susceptibility measurements with temperature and hysteresis experiments yield in most cases nearly reversible curves with Curie points close to that of magnetite and pseudo-single-domain characteristics. Characteristic remanent magnetisations (ChRM) isolated after the first steps of demagnetisation are all normal polarity. According to the dispersion of virtual geomagnetic pole (VGP) directions, paleosecular variation was abnormally lower than the one observed in general during Miocene. Considering our paleomagnetic results together with available radiometric data, it seems that the volcanic units have been emplaced during a very short time span of about 0.08 million years. The mean paleomagnetic directions obtained from this study do not differ significantly from that expected for the middle Miocene. Thirty-one samples from eight individual flows yielded acceptable paleointensity estimates. The site mean paleointensities range from 27.8±0.9 to 42.0±7.9 ?T. The virtual dipole moments (VDM) range from 5.9 to 9.5×10 22 Am 2. This corresponds to a mean value of 7.6±1.4×10 22 Am 2, which is higher than the average VDM value for late Miocene. Altogether our data suggest the existence of relatively high geomagnetic field strength undergoing low fluctuations. These results support the theoretical suggestion about an inverse relationship between secular variation and local field strength as result of electromagnetic coupling between the solid inner core and liquid outer core, with the inner core tending to stabilise core convection, and hence the field, when intensity is high. Some fluctuation of absolute intensity was detected within the same directional group (DG) indicating that the intensity of the geomagnetic field varies faster than its direction.

Goguitchaichvili, Avto; Alva Valdivia, Luis M.; Elguera, Jose Rosas; Fucugauchi, Jaime Urrutia; Cervantes, Miguel Angel; Morales, Juan

2002-11-01

129

Mid Miocene Terrestrial Ecosystems: Information from Mammalian Herbivore Communities.  

NASA Astrophysics Data System (ADS)

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.

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

2001-05-01

130

Miocene characid fishes from Colombia: evolutionary stasis and extirpation.  

PubMed

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

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

1986-10-10

131

Late Miocene biogeography and paleoclimatology of the central North Atlantic  

USGS Publications Warehouse

Quantitative analyses of planktonic foraminiferal assemblages from Deep Sea Drilling Project (DSDP) Holes 334 and 410 demonstrate that subpolar and subtropical faunal provinces existed in the North Atlantic during the late Miocene. Climatic oscillations are clearly recorded in Hole 410 by variations in abundance of the Neogloboquadrina subpolar assemblage. These climatic oscillations have a period of about 1 m.y. Higher frequency oscillations with a periodicity of one to several hundred thousand years are evident from about 6.5 to 7.5 m.y. and are probably present throughout the entire late Miocene. A revised age of 7.0 m.y. is proposed for the first occurrence of the calcareous nannofossil Amaurolithus primus (the Amaurolithus datum). ?? 1981.

Poore, R. Z.

1981-01-01

132

Upper Miocene reef complex of Mallorca, Balearic Islands, Spain  

SciTech Connect

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.

Pomar, L.

1988-02-01

133

New proconsuloid postcranials from the early Miocene of Kenya  

Microsoft Academic Search

New early Miocene forelimb fossils have been recovered from the Songhor and Lower Kapurtay localities in southwestern Kenya.\\u000a We describe four specimens that are similar in size and functional capabilities. Their specific allocation is problematic\\u000a but these forelimb specimens must belong to either Rangwapithecus gordoni or Proconsul africanus. If these new postcranial specimens should belong to R. gordoni, on the basis

Daniel L. Gebo; Nasser R. Malit; Isaiah Odhiambo Nengo

2009-01-01

134

Across the Pacific: Climate Evolution in the Middle Miocene  

NASA Astrophysics Data System (ADS)

We present the first high-resolution (3 kyr) astronomically-tuned record of ?18O and ?13C 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.

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

2013-12-01

135

Across the Pacific: Climate Evolution in the Middle Miocene  

NASA Astrophysics Data System (ADS)

We present the first high-resolution (3 kyr) astronomically-tuned record of ?18O and ?13C 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.

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

2014-05-01

136

Preservation of Miocene glacier ice in East Antarctica  

Microsoft Academic Search

ANTARCTIC climate during the Pliocene has been the subject of considerable debate. One view holds that, during part of the Pliocene, East Antarctica was largely free of glacier ice and that vegetation survived on the coastal mountains1á¤-4. An alternative viewpoint argues for the development of a stable polar ice sheet by the middle Miocene, which has persisted since then5á¤-10. Here

David E. Sugden; David R. Marchant; Noel Potter; Roland A. Souchez; George H. Denton; Carl C. Swisher III; Jean-Louis Tison

1995-01-01

137

Astronomical calibration age for the Oligocene-Miocene boundary  

Microsoft Academic Search

The stratotype section for the base of the Miocene is at a reversed (below) to normal (above) magnetic transition that is claimed to represent magnetic chron C6Cn.2n (o). Deep Sea Drilling Project (DSDP) Site 522 is the only location we are aware of that unambiguously records the three normal events of C6Cn. We have quantitatively determined the range of the

Nicholas J. Shackleton; Michael A. Hall; Isabella Raffi; Lisa Tauxe; James Zachos

2000-01-01

138

Extending the astronomical (polarity) time scale into the Miocene  

Microsoft Academic Search

An astronomical time scale is presented for the late Miocene based on the correlation of characteristic sedimentary cycle patterns in marine sections in the Mediterranean to the 65°N summer insolation curve of La90[1,2] with present-day values for the dynamical ellipticity of the Earth and tidal dissipation by the moon. This correlation yields ages for all sedimentary cycles and hence also

F. J. Hilgen; W. Krijgsman; C. G. Langereis; L. J. Lourens; A. Santarelli; W. J. Zachariasse

1995-01-01

139

Late Miocene hominids from the Middle Awash, Ethiopia  

Microsoft Academic Search

Molecular studies suggest that the lineages leading to humans and chimpanzees diverged approximately 6.5-5.5 million years (Myr) ago, in the Late Miocene. Hominid fossils from this interval, however, are fragmentary and of uncertain phylogenetic status, age, or both. Here I report new hominid specimens from the Middle Awash area of Ethiopia that date to 5.2-5.8 Myr and are associated with

Yohannes Haile-Selassie

2001-01-01

140

Middle Miocene paleoaltimetry of the southern Altiplano, central Andes  

NASA Astrophysics Data System (ADS)

The central Andean plateau is both high (mean elevation ~4 km) and broad (>300 km wide). Constraining the elevation history of the Andes is necessary to understand the effects of a high, broad mountain range on regional and global climate and the tectonic processes responsible for the creation and maintenance of such mountain plateaus. Recent paleoelevation estimates based on paleobotanical, stable isotope, and geomorphologic data suggest that the northern part of the central Andes experienced ~2.5 ± 1 km of surface uplift since ca. 10 Ma. Middle Miocene sedimentary sections were measured in two localities in the southern Altiplano and Eastern Cordillera. The depositional environment of Cerdas (~4000 m, ~16.3 to <15.105 Ma) in the Altiplano basin was dominantly fluvial floodplain and volcaniclastic-rich gravity flows; Quebrada Honda (~3500 m, >12.83 to <11.96 Ma) in the Eastern Cordillera consists of fluvial floodplain and ephemeral lacustrine environments. Sedimentation rates are on the order of 100-200 m/Myr, which is comparable to other middle Miocene basins in the central Andes. Carbonate nodules from paleosols within floodplain deposits were analyzed for stable isotopes. We employ a ?18O-altitude relationship based on modern rainfall (Gonfiantini et al., 2001) and surface water data to estimate paleoelevation from pedogenic carbonates. Data from Cerdas yield a mean ?18O of -10.8‰ and a paleoelevation estimate of 2458 ± 1000 m; data from Quebrada Honda produce a mean of -7.2‰ and a paleoelevation estimate of 757 ± 1000 m. These low elevations (relative to the modern elevations) in the southern Altiplano are consistent (within error) with published middle Miocene elevations for the northern Altiplano, suggesting a common plateau-wide elevation history prior to <11.96 Ma. If changes in paleoelevation of the southern Altiplano show synchronous late Miocene surface uplift as compared with the northern Altiplano, this would suggest that a regional tectonic process was responsible for the ~2 km of surface uplift since middle Miocene time.

Auerbach, D. J.; Garzione, C. N.; Smith, J. J.; MacFadden, B. J.

2008-12-01

141

12. STRONTIUM-ISOTOPIC CORRELATION OF OLIGOCENE TO MIOCENE SEQUENCES, NEW JERSEY AND FLORIDA1  

Microsoft Academic Search

We use Sr-isotopic age estimates to date siliciclastic, carbonate, and mixed siliciclastic-carbonate Oligocene and Miocene sequences for the New Jersey Coastal Plain and Florida Peninsula and to correlate sequence boundaries with the deep-sea ?18O record and the inferred eustatic record of Exxon. The New Jersey onshore Oligocene to lower Miocene sequences correlate rea- sonably well with the Florida Miocene sequences.

Peter J. Sugarman; Lucy McCartan; Kenneth G. Miller; Mark D. Feigenson; Stephen Pekar; Ronald W. Kistler; A. G. Robinson

142

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

143

Early Miocene benthic foraminifera and biostratigraphy of the Qom Formation, Deh Namak, Central Iran  

NASA Astrophysics Data System (ADS)

A total of 165 samples were collected from the Qom Formation investigated in a stratigraphic section north of Deh Namak, in Central Iran. From these, 35 genera and 47 species of benthic foraminifera were identified. The age of the studied section is Early Miocene (Aquitanian to Early Burdigalian) based on the occurrence of Borelis melo curdica, Meandropsina anahensis, Meandropsina iranica, Elphidium sp. 14, Peneroplis farsensis, and Triloculina tricarinata. The thickness of the Qom Formation is 401 m of which 161.2 m is early Burdigalian in age. Foraminiferal assemblages in the Deh Namak section are referable to the Borelis melo group- Meandropsina iranica Assemblage Zone and Miogypsinoides- Archaias-Valvulinid Assemblage Zone of [Adams, T.D., Bourgeois, F., 1967. Asmari biostratigraphy. Iranian Oil Operating Companies, Geological and Exploration Division, Report1074 (unpublished) 1-37.] described originally from the Asmari Formation.

Daneshian, Jahanbakhsh; Dana, Leila Ramezani

2007-03-01

144

Early Miocene Tectonic Activity in the western Ross Sea (Antarctica)  

NASA Astrophysics Data System (ADS)

In the framework of the Rossmap Italian PNRA work objectives to compile extended and revised digital maps of the main unconformities in Ross Sea, Antarctica, much additional seismic reflection data, that were not available to previous ANTOSTRAT compilation, were incorporated into a new ROSSMAP interpretation. The correlation across almost all of Ross Sea, from DSDP Site 270 and Site 272 in Eastern Basin to northern Victoria Land Basin, of additional early Miocene and late Oligocene horizons that were not part of ANTOSTRAT allows interpretations to be made of fault activity and glacial erosion or deposition at a finer time resolution. New conclusions include that extensional or transtensional fault activity within the zone between Victoria Land Basin and Northern Basin, initiated by 23 Ma or earlier, and continued after 18 Ma. Steep parallel-striking faults in southern Victoria Land Basin display both reverse and normal separation of 17.5 Ma (from Cape Roberts Program-core 1) and post-16 Ma horizons, suggesting an important strike-slip component. This result may be compared with published papers that proposed post-17 Ma extension in southern Victoria Land Basin, 16-17 Ma extension in the AdareTrough, north of the Ross Sea continental shelf, but no Miocene extension affecting the Northern Basin (Granot et al., 2010). Thus, our evidence for extension through the early Miocene is significant to post-spreading tectonic models. Reference Granot R., Cande S. C., Stock J. M., Davey F. J. and Clayton R. W. (2010) Postspreading rifting in the Adare Basin, Antarctica: Regional tectonic consequences. Geochem. Geophys. Geosyst., 8, Q08005, doi:10.1029/2010GC003105.

Sauli, C.; Sorlien, C. C.; Busetti, M.; Geletti, R.; De Santis, L.

2012-12-01

145

Multiple Miocene Melastomataceae dispersal between Madagascar, Africa and India.  

PubMed Central

Melastomataceae sensu stricto (excluding Memecylaceae) comprise some 3000 species in the neotropics, 1000 in Asia, 240 in Africa, and 230 in Madagascar. Previous family-wide morphological and DNA analyses have shown that the Madagascan species belong to at least three unrelated lineages, which were hypothesized to have arrived by trans-oceanic dispersal. An alternative hypothesis posits that the ancestors of Madagascan, as well as Indian, Melastomataceae arrived from Africa in the Late Cretaceous. This study tests these hypotheses in a Bayesian framework, using three combined sequence datasets analysed under a relaxed clock and simultaneously calibrated with fossils, some not previously used. The new fossil calibration comes from a re-dated possibly Middle or Upper Eocene Brazilian fossil of Melastomeae. Tectonic events were also tentatively used as constraints because of concerns that some of the family's fossils are difficult to assign to nodes in the phylogeny. Regardless of how the data were calibrated, the estimated divergence times of Madagascan and Indian lineages were too young for Cretaceous explanations to hold. This was true even of the oldest ages within the 95% credibility interval around each estimate. Madagascar's Melastomeae appear to have arrived from Africa during the Miocene. Medinilla, with some 70 species in Madagascar and two in Africa, too, arrived during the Miocene, but from Asia. Gravesia, with 100 species in Madagascar and four in east and west Africa, also appears to date to the Miocene, but its monophyly has not been tested. The study afforded an opportunity to compare divergence time estimates obtained earlier with strict clocks and single calibrations, with estimates based on relaxed clocks and different multiple calibrations and taxon sampling.

Renner, Susanne S

2004-01-01

146

Miocene reef facies of pelagian block, central Mediterranean  

SciTech Connect

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.

Pedley, H.M.

1988-02-01

147

Early Miocene mylonitization and detachment faulting, South Mountains, central Arizona  

SciTech Connect

The South Mountains of central Arizona are one of the geologically simplest metamorphic core complexes of the North American Cordillera. An early Miocene age of mylonitization is indicated by crosscutting relationships between mylonitic fabric and a composite pluton dated at 22-25 Ma by Rb-Sr, U-Th-Pb, and K-Ar techniques. The kinematic agreement and close temporal association of mylonitization and detachment faulting support models in which the two processes are related to an evolving crustal shear zone that accommodated mid-Tertiary continental extension. 19 references, 3 figures, 2 tables.

Reynolds, S.J.; Shafiqullah, M.; Damon, P.E.; DeWitt, E.

1986-04-01

148

The beaver Anchitheriomys from the Miocene of Central Europe  

SciTech Connect

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.

Stefen, C.; Mors, T. [Museum Tierkunde, Dresden (Germany)

2008-09-15

149

Miocene shale tectonics in the Moroccan margin (Alboran Sea)  

NASA Astrophysics Data System (ADS)

The Betic (Southern Spain) and Rif (Morocco) mountains form an arcuate belt that represents the westernmost termination of the peri-mediterranean Alpine mountain chain. The Miocene Alboran Basin and its subbasins is located in the hinterland of the Betic-Rif belt. It is considered to be a back-arc basin that developed during the coeval westward motion of the Alboran domain and the extensional collapse of previously thickened crust of the Betic-Rif belt. The Western Alboran Basin (WAB) is the major sedimentary depocenter with a sediment thickness in excess of 10 km, it is bordered by the Gibraltar arc, the volcanic Djibouti mounts and the Alboran ridge. Part of the WAB is affected by shale tectonics and associated mud volcanism. High-quality 2D seismic profiles acquired on the Moroccan margin of the Alboran Basin during the last decade reveal the multiple history of the basin. This study deals with the analysis of a number of these seismic profiles that are located along and orthogonal to the Moroccan margin. Seismic stratigraphy is calibrated from industrial wells. We focus on the interactions between the gravity-driven tectonic processes and the sedimentation in the basin. Our seismic interpretation confirms that the formation of the WAB began in the Early Miocene (Aquitanian - Burdigalian). The fast subsidence of the basin floor coeval to massive sedimentation induced the undercompaction of early miocene shales during their deposition. Downslope migration of these fine-grained sediments initiated during the deposition of the Langhian siliciclastics. This gravity-driven system was accompanied by continuous basement subsidence and induced disharmonic deformation in Mid Miocene units (i.e. not related to basement deformation). The development of shale-cored anticlines and thrusts in the deep basin is the result of compressive deformation at the front of the gravity-driven system and lasted for ca. 15 Ma. The compressive front has been re-activated by strong siliciclastic deposition, such as in the Serravalian-Tortonian period or more recently during the Quaternary contourites deposition. The Messinian dessication of the Mediterranean Sea and the following catastrophic Pliocene reflooding caused or enhanced re-activation of the deformation.

Do Couto, D.; El Abbassi, M.; Ammar, A.; Gorini, C.; Estrada, F.; Letouzey, J.; Smit, J.; Jolivet, L.; Jabour, H.

2011-12-01

150

Paleoceanographic implications of Miocene deep-sea hiatuses.  

USGS Publications Warehouse

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

Keller, G.; Barron, J. A.

1983-01-01

151

The stable isotope archive of Lake Pannon as a mirror of Late Miocene climate change  

Microsoft Academic Search

Lake Pannon was a long-lived Miocene and Pliocene lake system in Central Europe with a famous endemic mollusc fauna. The radiation of melanopsid gastropods and dreissenid bivalves has been explained simply by the opportunity to settle empty ecological niches after the extinction of marine life at the end of the Middle Miocene. This model, however, fails to explain the offset

Mathias Harzhauser; Christine Latal; Werner E. Piller

2007-01-01

152

Geochemistry of Miocene basaltic rocks recovered by the Ocean Drilling Program from the Japan Sea  

Microsoft Academic Search

Ocean Drilling Program Leg 127 drilling at site 797 in the Yamato Basin of the Japan Sea indicated that the basement is composed of early Miocene (?19 Ma) basaltic-doleritic rocks, whereas at site 795 in the northern Japan Basin the basement is composed of middle Miocene (?15 Ma) calc-alkali basalt and basaltic andesite lava flows. The basaltic rocks from Hole

Ju-chin Chen; Kuo-Lin Lee

1996-01-01

153

Palaeoenvironmental Shifts Drove the Adaptive Radiation of a Noctuid Stemborer Tribe (Lepidoptera, Noctuidae, Apameini) in the Miocene  

PubMed Central

Between the late Oligocene and the early Miocene, climatic changes have shattered the faunal and floral communities and drove the apparition of new ecological niches. Grassland biomes began to supplant forestlands, thus favouring a large-scale ecosystem turnover. The independent adaptive radiations of several mammal lineages through the evolution of key innovations are classic examples of these changes. However, little is known concerning the evolutionary history of other herbivorous groups in relation with this modified environment. It is especially the case in phytophagous insect communities, which have been rarely studied in this context despite their ecological importance. Here, we investigate the phylogenetic and evolutionary patterns of grass-specialist moths from the species-rich tribe Apameini (Lepidoptera, Noctuidae). The molecular dating analyses carried out over the corresponding phylogenetic framework reveal an origin around 29 million years ago for the Apameini. Ancestral state reconstructions indicate (i) a potential Palaearctic origin of the tribe Apameini associated with a major dispersal event in Afrotropics for the subtribe Sesamiina; (ii) a recent colonization from Palaearctic of the New World and Oriental regions by several independent lineages; and (iii) an ancestral association of the tribe Apameini over grasses (Poaceae). Diversification analyses indicate that diversification rates have not remained constant during the evolution of the group, as underlined by a significant shift in diversification rates during the early Miocene. Interestingly, this age estimate is congruent with the development of grasslands at this time. Rather than clade ages, variations in diversification rates among genera better explain the current differences in species diversity. Our results underpin a potential adaptive radiation of these phytophagous moths with the family Poaceae in relation with the major environmental shifts that have occurred in the Miocene.

Toussaint, Emmanuel F. A.; Condamine, Fabien L.; Kergoat, Gael J.; Capdevielle-Dulac, Claire; Barbut, Jerome; Silvain, Jean-Francois; Le Ru, Bruno P.

2012-01-01

154

Facies Analysis and Depositional environment of the Oligocene-Miocene Qom Formation in the Central Iran (Semnan area)  

NASA Astrophysics Data System (ADS)

The Qom formation was formed in the Oligo-Miocene during the final sea transgression in Central Iran. This Formation in the Central Iran Basin Contains oil and gas. Organic geochemical analysis in previous studies indicated that the hydrocarbons migrated from deeper source rocks, likely of Jurassic age. In the Central Iran Basin, the Qom Formation is 1,200m thick and is abounded by the Oligocene Lower Red Formation and the middle Miocene Upper Red Formation. In previous studies, the Qom Formation was divided into nine members designated from oldest to youngest: a, b, c1 to c4, d, e, and f, of which "e" is 300m thick and constitutes the main reservoir. Our study focused on a Qom Section located in the Arvaneh (Semnan) region of Central Iran that is 498m thick. The lower part of the formation was not deposited, and only the following four members of early Miocene age (Aquitanian-Burdigalian) was identified between the lower and upper Red Formation. The studied section mainly consist of limestone, marl, sandy limestone, sandy marl and argillaceous limestone.According to this study(field and laboratory investigations), 9 carbonate microfacies were recognized which are grouped into four facies associations (microfacies group). These facies associations present platform to basin depositional setting and are nominated as: A (Tidal-flat), B (Lagoon), C (Slope) and D (Open marine). Based on paleoecology and Petrographic analysis, it seems the Qom Formation was deposited in a Carbonate shelf setting. The Qom formation constitutes a regional transgressive-regressive sequence that is bounded by two continental units (Lower and Upper Red Formation).

Sabouhi, Mostafa; Sheykh, Morteza; Darvish, Zohreh; Naghavi Azad, Maral

2010-05-01

155

From latest miocene thrusting to quaternary transpression and transtension in the Interandean Valley, Ecuador  

NASA Astrophysics Data System (ADS)

Field studies of folds and striated fault planes were carried out in the Interandean Valley (IV) of Ecuador, a NNE-SSW elongated depression lying between the Cordillera Occidental and the Cordillera Real. Four tectonic events were recognized: (a) at the end of Miocene the continental deposits of Chota Group were involved in cylindrical folds characterized by a WNW-ESE direction of shortening; (b) a second compressive pulse occurred during Pliocene or early Pleistocene when lava flows dated 6 Ma were affected by NNE trending right-lateral strike-slip faults and fluvial deposits of 1.7 Ma were involved in N-S trending folds; (c) lacustrine, fluvial and volcanic intermontane deposits dating up to the middle Pleistocene were deformed during late Pleistocene by a system of strike-slip and reverse faults, consistent with a N-S direction of the greatest principal stress (?1), and by en-échelon folds with an average E-W axis, oblique to the NNE trend of the Cordilleras; (d) a last tectonic pulse involved also volcano-sedimentary deposits dating up to the Holocene, which were affected by an en-échelon NNE left-lateral normal and N-S pure normal faults responding to an E-W least principal stress (?3). The en-échelon arrangement of the post-Miocene structures, the predominance of strike-slip and oblique-slip motions and the presence of strike-slip faulting in the Cordilleras, lead us to interpret the Plio-Quaternary tectonic events in the frame of transpressive and transtensive deformation regimes. This evolution of the deformation styles is thought to be the result of the reactivation of the early Tertiary suture zone, laying beneath the volcano-sedimentary filling of the IV, by the differential motions between the Cordillera Occidental and Cordillera Real crustal blocks during Plio-Quaternary times.

Tibaldi, A.; Ferrari, L.

1992-06-01

156

Relationship of Mediterranean type lamproites to large shoshonite volcanoes, Miocene of Lesbos, NE Aegean Sea  

NASA Astrophysics Data System (ADS)

Shoshonites, which are high-K trachyandesitic rocks, are found in many orogenic belts and are commonly of post-collisional origin. The petrogenesis of shoshonites has been widely debated. Small lava flows and dykes of lamproite and related lamproitic rocks of early Miocene age in Lesbos are coeval with voluminous shoshonite volcanoes. Their distinctive petrology and isotope geochemistry provide an exceptional opportunity to assess the petrogenetic relationship between lamproites and shoshonites. The lamproitic rocks contain phenocrysts of forsteritic olivine (as high as Fo93) and clinopyroxene, both with inclusions of chrome spinel (Cr# ~ 0.9 or ~ 0.6) and carbonate melt inclusions, indicating the presence of carbonatite melts. Some complexly zoned clinopyroxene from lamproitic rocks have salite cores with chemical composition suggesting they formed in the upper mantle in a melt strongly enriched in LILE and LREE. Both lamproites and shoshonites show continuous trends of trace elements and their isotopic compositions overlap. Lack of variation in K with Mg# or SiO2 for particular temporal-spatial groups of shoshonites suggests derivation from particular inhomogeneous mantle rather than fractionation processes. In contrast to other peri-Mediterranean lamproites, the Lesbos lamproites and shoshonites have unusual Pb isotope composition that requires a common origin from subcontinental lithospheric mantle enriched in LILE in the Paleozoic. This enrichment process involved partial melting of subducted carbonate-bearing pelites. Triassic rift-related volcanism and formation of Jurassic small ocean basins produced extreme depletion of parts of the mantle. Lamproitic magma was derived from melting of enriched refractory harzburgite, whereas enriched lherzolite, wehrlite and pyroxenite partially melted to supply larger volumes of shoshonitic and related magmas. The NE Aegean Miocene shoshonite province is thus not directly related to contemporary subduction, but may have been triggered by related back-arc extension.

Pe-Piper, Georgia; Zhang, Yuanyuan; Piper, David J. W.; Prelevi?, Dejan

2014-01-01

157

Alkenone producers during late Oligocene-early Miocene revisited  

NASA Astrophysics Data System (ADS)

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).

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

2012-03-01

158

Upper Miocene reef complex of Mallorca, Balearic Islands, Spain  

SciTech Connect

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.

Pomar, L.

1988-01-01

159

Plate-induced Miocene extension in southern California  

SciTech Connect

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.

Stuart, W.D. (Geological Survey, Pasadena, CA (United States) Univ. of California, Santa Barbara, CA (United States))

1992-01-01

160

Millennial scale climatic responses through a Late Miocene precession cycle  

NASA Astrophysics Data System (ADS)

Late Miocene (11.61-5.33 Ma) climate is thought to have been warmer and wetter than the present, with nearly ice-free conditions over the Northern Hemisphere, and significant differences in vegetation distribution. There still is considerable uncertainty in the reconstructed CO2 levels for this time period, fostered by the temporally and spatially biased distribution of the available proxy record. Previous model-data comparison studies (i.e. Bradshaw et al., 2012; Pound et al., 2011) highlighted the mismatch between model results and proxy data for this time period. Here, we investigate how taking into account the variability due to changes in orbital forcing can account for some of these differences. We also explore the orbital control on the monsoonal systems at millennial scale resolution, as well as the impact of background CO2 on orbital sensitivity. Long-term changes in seasonal and latitudinal solar insolation are generated by periodic oscillations in the Earth's orbit and tilt relative to the Sun. These cycles have a modulating effect on climate and ocean circulation patterns. A record of this signal can be found in a number of terrestrial and marine sedimentary sequences. A series of 22 fully coupled atmosphere-ocean-vegetation simulations has been run through an entire precession cycle during the Late Miocene (~6.5 Ma). These experiments were performed using HadCM3L (Hadley Centre Coupled Model, Version 3 - Low resolution ocean) with TRIFFID (Top-down Representation of Interactive Foliage and Flora Including Dynamics) to test the climatic response to changes in orbital forcing. The Mediterranean Sea provides a remarkable geological record for this time slice. Several sequences around the basin margins have been astronomically tuned so that high resolution geological data can be directly compared with our model results. However, this is not the case for the rest of the world, where the distribution of climate proxy data for the Late Miocene is sparse, patchy and is typically constrained by a low-resolution age model. Model results show the effect of different orbital configurations on the North African summer monsoon, with highly intensified precipitation patterns over these regions at times of minimum precession (maximum insolation), triggering significant changes in vegetation belts. Our simulations are compared quantitatively with the palaeorecord and show that orbital forcing could explain some, but not all, of the published model-data mismatch. Bradshaw, C. D., Lunt, D. J., Flecker, R., Salzmann, U., Pound, M. J., Haywood, A. M., and Eronen, J. T.: The relative roles of CO2 and palaeogeography in determining late Miocene climate: results from a terrestrial model-data comparison, Clim. Past, 8, 1257-1285, 2012. Pound, M. J., Haywood, A. M., Salzmann, U., Riding, J. B., Lunt, D. J., and Hunter, S. J.: A Tortonian (late Miocene, 11.61-7.25 Ma) global vegetation reconstruction, Palaeogeogr. Palaeocl., 300, 29-45, 2011.

Marzocchi, Alice; Lunt, Dan; Flecker, Rachel; Bradshaw, Catherine

2014-05-01

161

A Synthesis of Late Miocene Through Pliocene Evolution of Glaciation as Inferred From Deep Sea Geochemical Records  

Microsoft Academic Search

During the Miocene through Pliocene climate evolved from an early Miocene climatic optimum (~16 Ma) followed by major expansion of the Antarctic ice sheet during the middle Miocene (~15 Ma), to an early Pliocene interval of relative global warmth (5 to 3.5 Ma) followed by the onset of wide spread Northern Hemisphere Glaciation during the late Pliocene (~3 Ma). Here

K. Billups

2008-01-01

162

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

USGS Publications Warehouse

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.

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

2008-01-01

163

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

NASA Astrophysics Data System (ADS)

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 2-4°C 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.

Belanger, C. L.

2012-12-01

164

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

USGS Publications Warehouse

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.

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

1980-01-01

165

Large tectonic rotations since the Early Miocene in a convergent plate-boundary zone, South Island, New Zealand  

NASA Astrophysics Data System (ADS)

A palaeomagnetic study in part of the New Zealand plate-boundary zone provides new constraints on the temporal and spatial distribution of Neogene and Quaternary tectonic rotations. Thermal demagnetization of samples from Cretaceous basaltic dykes, Palaeocene-Oligocene micritic limestone, and Miocene and Pliocene siltstones in the Marlborough region, South Island, have defined stable, high-temperature magnetic components, which are interpreted as the primary magnetization. Declination anomalies, after tectonic corrections, are interpreted as rigid body rotations about a vertical axis of sample sites relative to the Pacific plate. All palaeomagnetic data from Marlborough cluster into three main groups. A 60-100° clockwise rotation affected Palaeocene to Middle Miocene sedimentary sequences across Marlborough between ˜ 18 Ma and ˜ 8 Ma, coeval with a phase of low-angle thrusting. The absence of this rotation in a Late Cretaceous dyke swarm defines the present western limit of the early rotating zone. A regional ˜ 20° clockwise rotation occurred in the last 4 Ma during the development of the Marlborough Fault System in a zone of dextral transpression, although locally clockwise rotations ? 40° may have occurred near some of the major dextral strike-slip faults. However, a negligible rotation is observed in the same period in the region to the southeast of the major Kekerengu dextral strike-slip fault, which appears to have acted as a hinge zone, accommodating relative rotation by dextral strike-slip on an arcuate fault, bending, and internal deformation. The observed tectonic rotations record the overall clockwise rotation of the trend of the southern end of the Hikurangi margin from W to NW in the Early Miocene to ˜ NE today, determined independently from the long-term relative plate motion data for the Pacific and Australian plates.

Vickery, Sara; Lamb, Simon

1995-11-01

166

Systematics of early and middle Miocene Old World monkeys.  

PubMed

New information about the early cercopithecoids Prohylobates tandyi (Wadi Moghra, Egypt) and Prohylobates sp. indet. (Buluk and Nabwal, Kenya) is presented. Comparisons are made among all major collections of Early and Middle Miocene catarrhine monkeys, and a systematic revision of the early Old World monkeys is provided. Previous work involving the systematics of early Old World monkeys (Victoriapithecidae; Cercopithecoidea) has been hampered by a number of factors, including the poor preservation of Prohylobates material from North Africa and lack of comparable anatomical parts across collections. However, it is now shown that basal cercopithecoid species from both northern and eastern Africa can be distinguished from one another on the basis of degree of lower molar bilophodonty, relative lower molar size, occlusal details, symphyseal construction, and mandibular shape. Results of particular interest include: 1) the first identification of features that unambiguously define Prohylobates relative to Victoriapithecus; 2) confirmation that P. tandyi is incompletely bilophodont; and 3) recognition of additional victoriapithecid species. PMID:19640562

Miller, E R; Benefit, B R; McCrossin, M L; Plavcan, J M; Leakey, M G; El-Barkooky, A N; Hamdan, M A; Abdel Gawad, M K; Hassan, S M; Simons, E L

2009-09-01

167

Ruminant diets and the Miocene extinction of European great apes  

PubMed Central

The successful evolutionary radiations of European hominoids and pliopithecoids came to an end during the Late Miocene. Using ruminant diets as environmental proxies, it becomes possible to detect variations in vegetation over time with the potential to explain fluctuations in primate diversity along a NW–SE European transect. Analysis shows that ruminants had diverse diets when primate diversity reached its peak, with more grazers in eastern Europe and more browsers farther west. After the drop in primate diversity, grazers accounted for a greater part of western and central European communities. Eastwards, the converse trend was evident with more browsing ruminants. These opposite trends indicate habitat loss and an increase in environmental uniformity that may have severely favoured the decline of primate diversity.

Merceron, Gildas; Kaiser, Thomas M.; Kostopoulos, Dimitris S.; Schulz, Ellen

2010-01-01

168

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

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

169

Eocene-early Miocene foreland basin development and the history of Himalayan thrusting, western and central Nepal  

NASA Astrophysics Data System (ADS)

Sedimentologic, petrographic, and U-Pb detrital zircon ages from middle Eocene through early Miocene sedimentary rocks in the Lesser Himalayan zone of western and central Nepal indicate that a peripheral foreland basin system had developed in the eastern Himalayan collision zone by middle Eocene time. The shallow-marine, Eocene Bhainskati Formation accumulated in a back-bulge depozone between a southward migrating forebulge and the Indian craton. Migration of the forebulge through this region during Eocene-Oligocene time produced a regional unconformity that spans ˜15-20 Myr. By early Miocene time, the forebulge unconformity was onlapped by the distal fringes of the southward migrating foredeep depozone, represented by fluvial deposits of the Dumri Formation. Continued southward migration of the foredeep during the Neogene accommodated the fluvial Siwalik Group. Light mineral provenance data and U-Pb detrital zircon ages suggest that the Bhainskati was derived partly from Tethyan sedimentary rocks of the Tibetan Himalayan zone during initial growth of the Himalayan fold-thrust belt. The Dumri was derived from metasedimentary and crystalline rocks of the Greater Himalayan zone during emplacement of the Main Central thrust and contemporaneous tectonic unroofing by normal faulting along the South Tibetan detachment system. The Lesser Himalayan crystalline thrust sheets were emplaced soon after deposition of the Dumri Formation, ˜15-10 Ma. Paleocurrent and lithofacies data from the Dumri Formation indicate deposition by west-southwestward flowing rivers that drained into the Indus portion of the Himalayan foreland basin system during the early Miocene. Thick channel sandstones in the lower Dumri may represent the early Miocene counterpart of the modern Ganges River. Eastward diversion of the Ganges drainage system to near its present location had occurred by ˜15 Ma, as the high-standing Aravalli Range on the northern Indian shield approached the front of the fold-thrust belt. Assuming reasonable values for the flexural rigidity of Indian lithosphere, the time span of the forebulge unconformity yields a velocity of ˜14-33 mm/yr for the southward migration of the fold-thrust belt relative to India. This range of values is consistent with Neogene and present-day estimates and suggests that only one third to one half of India-Eurasia convergence has been accommodated by shortening in the Himalayan fold-thrust belt since the onset of collision.

Decelles, Peter G.; Gehrels, George E.; Quade, Jay; Ojha, T. P.

1998-10-01

170

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

PubMed Central

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.

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

2012-01-01

171

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

172

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

NASA Astrophysics Data System (ADS)

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).

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

2013-12-01

173

Phylogeny and rapid northern and southern hemisphere speciation of goldfinches during the Miocene and Pliocene epochs.  

PubMed

Mitochondrial cytochrome b (cyt b) from 25 out of 31 extant goldfinches, siskins, greenfinches and redpolls (genus Carduelis) has been sequenced from living samples taken around the world, specimens have also been photographed. Phylogenetic analysis consistently gave the same groups of birds, and this grouping was generally related to geographical proximity. It has been supposed that Pleistocene glaciations played a crucial role in the origin of extant diversity and distribution of Northern Hemisphere vertebrates. Molecular comparison of most extant songbird species belonging to the genus Carduelis does not support this assertion. The fossil record of chicken and pheasant divergence time has been used to calibrate the molecular clock; cyt b DNA dendrograms suggest that speciation in Carduelinae birds occurred during the Miocene and Pliocene Epochs (9-2 million years ago) in both the Northern and Southern Hemispheres. Only about 4% average amount of nucleotide substitution per lineage is found between the most distant Carduelis species; this suggests a remarkably rapid radiation when compared with the radiation of other passerine songbird genera. In addition, a continuum of small songbird speciation may be found during the Miocene Epoch in parallel with speciation of other orders (i.e. Galliformes, chicken/pheasant). Pleistocene glaciations may have been important in subspeciation (i.e. Eastern European grey-headed goldfinches/Western European black-headed goldfinches) and also in ice-induced vicariance (isolation) (i.e. siskin in Western Europe vs. siskin in Far East Asia) around the world. European isolated Serinus citrinella (citril finch) is not a canary, but a true goldfinch. South American siskins have quickly radiated in the last 4 million years coinciding with the emergence of the Isthmus of Panama; probably, a North American siskin related to C. notata invaded a suitable and varied biotope (the South American island) for Carduelis birds. North American goldfinches may be renamed as siskins, because they have a distant genetic relationship with European goldfinches. Genus Acanthis could be dropped, and thus redpolls should be separated from twite and linnet, the latter (Europeans) probably being related to American goldfinches. Also, reproductive barriers are observed between closely related species and not between other more distant ones. Finally, a tentative classification for genus Carduelis species is suggested. PMID:9791543

Arnaiz-Villena, A; Alvarez-Tejado, M; Ruíz-del-Valle, V; García-de-la-Torre, C; Varela, P; Recio, M J; Ferre, S; Martínez-Laso, J

1998-09-01

174

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

PubMed

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

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

2014-07-01

175

A new Middle Miocene tarsier from Thailand and the reconstruction of its orbital morphology using a geometric-morphometric method  

PubMed Central

Tarsius is an extant genus of primates endemic to the islands of Southeast Asia that is characterized by enormously enlarged orbits reflecting its nocturnal activity pattern. Tarsiers play a pivotal role in reconstructing primate phylogeny, because they appear to comprise, along with Anthropoidea, one of only two extant haplorhine clades. Their fossils are extremely rare. Here, we describe a new species of Tarsius from the Middle Miocene of Thailand. We reconstructed aspects of its orbital morphology using a geometric–morphometric method. The result shows that the new species of Tarsius had a very large orbit (falling within the range of variation of modern Tarsius) with a high degree of frontation and a low degree of convergence. Its relatively divergent lower premolar roots suggest a longer mesial tooth row and therefore a longer muzzle than in extant species. The new species documents a previous unknown Miocene group of Tarsius, indicating greater taxonomic diversity and morphological complexity during tarsier evolution. The current restriction of tarsiers to offshore islands in Southeast Asia appears to be a relatively recent phenomenon.

Chaimanee, Yaowalak; Lebrun, Renaud; Yamee, Chotima; Jaeger, Jean-Jacques

2011-01-01

176

Late Miocene (Pannonian) Gastropods of Lake Pannon with Special Emphasis on Early Ontogenetic Development  

Microsoft Academic Search

Summary An extraordinarily well-preserved brackish to freshwater gastropod fauna of the Early Pannonian (Late Miocene) is described. The assemblage derives from the Austrian part of the Eisenstadt-Sopron Basin (sand pit \\

Mathias HARZHAUSER; Thorsten KOWALKE; Oleg MANDIC

2004-01-01

177

Intracontinental Miocene: Climate and paleolake volumes in the Forez Basin, France (Part I)  

NASA Astrophysics Data System (ADS)

European Tertiary sedimentary basins as the Forez Graben, France, are potential records of continental paleoclimates. The Forez Basin hosts deposited and precipitated sediments of Oligocene to Miocene age. Geochemical data of carbonates indicate strictly continental origin starting at Eocene-Oligocene with tropical to temperate climate conditions, then during the Middle Miocene a temperate continental climate prevails. Combining volume of calcite deposits and their geochemical data, volumes of large lakes and evaporation/inflow ratios were reconstructed. The Late Miocene in the Forez Graben has been affected by dissolution and secondary precipitation of calcite, barite, which is the result of wetter and colder climate conditions. These lake volume calculations represent the first estimation of large lakes volumes in Western Europe during the Miocene.

Renac, C.; Michon, G.; Gonord, H.; Gerbe, M.-C.

2013-04-01

178

Miocene–Quaternary structural evolution of the Uyuni–Atacama region, Andes of Chile and Bolivia  

Microsoft Academic Search

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

A. Tibaldi; C. Corazzato; A. Rovida

2009-01-01

179

Whiting-related sediment export along the Middle Miocene carbonate ramp of Great Bahama Bank  

Microsoft Academic Search

Modern aragonite needles are present all along the modern leeward margin of Great Bahama Bank (ODP Leg 166), while Middle\\u000a Miocene sediments contain needles only in more distal areas (Sites 1006 and 1007). In contrast to the rimmed, flat-topped\\u000a platform topography during the Plio-Pleistocene, the Miocene Great Bahama Bank morphology is a carbonate ramp profile. This\\u000a might imply a different

Mélanie Turpin; Laurent Emmanuel; John J. G. Reijmer; Maurice Renard

2011-01-01

180

Magmatic evolution of the Sarapiqui Miocene Arc, Costa Rica, Central America  

Microsoft Academic Search

The Sarapiqui Miocene Arc (22.2-11.4 Ma) is located in the modern back-arc region of northern Costa Rica, Central America. The arc basement is represented by serpentinized peridotites, Albian silicic pelagites, and Paleocene to Middle Eocene turbidites. Magmatic units vary from basalts to rhyolites and include lavas, pyroclastic deposits, and a few subvolcanic bodies. The magmatic evolution of the Sarapiqui Miocene

E. Gazel; G. E. Alvarado; M. J. Carr; J. Obando; A. Alfaro

2005-01-01

181

Development of Miocene-Pliocene reef trend, St. Croix, U. S. Virgin Islands  

Microsoft Academic Search

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

I. Gill; D. E. Eby; D. K. Hubbard; S. H. Frost

1988-01-01

182

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

Microsoft Academic Search

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

Ricardo Ignacio Combellas Bigott

2003-01-01

183

Origin of secondary potash deposits; a case from Miocene evaporites of NW Central Iran  

Microsoft Academic Search

In early Miocene times, an extensive carbonate shelf developed in Central Iran and during several cycles of sea-level fluctuations, evaporite-bearing carbonate sequences of the Qom Formation were deposited. However, in the early-middle Miocene, development of restricted marine conditions led to a facies change from shelf carbonates of the Qom Formation to the evaporite series of the M1 member of the

H. Rahimpour-Bonab; Z. Kalantarzadeh

2005-01-01

184

Kerogen and biomarker compositions of uranium-rich coaly shales from Miocene sequence at Kanamaru, Japan  

Microsoft Academic Search

We obtained a continuous 40 m-long core from the Miocene sedimentary sequence and basement Cretaceous granite at Kanamaru, northeast Japan. The Miocene sequence intercalates with a uranium-rich coaly shale seam (U = 25-100 ppm; Th = 23-42 ppm). We have analyzed the kerogen macerals and biomarkers in the core to characterize the organic matter in the uranium-rich seam. Visual kerogen

M. Yamamoto; Y. Watanabe

2005-01-01

185

Miocene unroofing of the Canyon Range during extension along the Sevier Desert Detachment, west central Utah  

Microsoft Academic Search

Apatite fission track results from Neoproterozoic and Lower Cambrian quartzites collected from the Canyon Range in west central Utah reveal a significant early to middle Miocene cooling event (~19-15 Ma). Preextensional temperatures estimated from multicompositional apatite fission track data suggest ~4.5 to >5.6 km of unroofing during the early to middle Miocene, assuming a geothermal gradient of ~25°C\\/km. The spatial

Daniel F. Stockli; Jonathan K. Linn; J. Douglas Walker; Trevor A. Dumitru

2001-01-01

186

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

USGS Publications Warehouse

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

Barron, J. A.; Keller, G.

1982-01-01

187

Oligocene-Miocene Bu Khang extensional gneiss dome in Vietnam: Geodynamic implications  

Microsoft Academic Search

A large Oligocene-Miocene extensional gneiss dome in Vietnam has implications for the kinematics of the Ailao Shan Red River shear zone and rifting of the South China Sea. A major northeast-dipping extensional shear zone separates the Bu Khang dome from less-metamorphosed units above. Shearing deformation occurred during the exhumation of high-pressure rocks. 40Ar-39Ar ages on micas reveal Oligocene-Miocene ages, from

Laurent Jolivet; Henri Maluski; Olivier Beyssac; Bruno Goffé; Claude Lepvrier; Phan Truong Thi; Nguyen van Vuong

1999-01-01

188

Reservoir Properties of Miocene Sandstones in Rzeszow Area (Carpathian Foredeep, Poland)  

Microsoft Academic Search

An integrated sedimentological, petrophysical and petrological study has been carried out in the Miocene succession in the\\u000a southern Carpathian Foredeep basin of SE Poland, involving examination of ca. 800 m of cores combined with analysis of wire\\u000a line logs from 14 wells. Our main goal was to identify regional trends in development of reservoir properties of the Miocene.\\u000a Very good

Grzegorz Le?niak; Piotr Such; Piotr Dziadzio

189

Case for Upper Miocene continental break-up in western Afar, southern Red Sea rift  

NASA Astrophysics Data System (ADS)

We describe the distribution, nature and timing of extension in the youthful Western Afar in order to infer mechanisms for continental break-up. New and existing remote sensing, fieldwork and structural analyses calibrated by geochronology were integrated to define rift stages and the distribution and nature of volcanic units and structures that accommodate extension. Oligo-Miocene continental rift basins of the Southern Red Sea rift, Ethiopia are typical steep-sided continental rift graben, but contain almost exclusively volcanic fill. Rift segmentation was defined by border faults that were the locus of strain, but strain migrated to magmatic centres within the basins in the Upper Miocene. Widespread basaltic volcanism in the Upper Miocene led to extension, burial, riftward rotation and seismic reactivation of Oligo-Miocene rift basins. These basalts were sourced from linear magmatic segments that are independent of the older border fault segmentation. Cycles of subsidence and volcanism gave the basalt successions a concave-down profile similar to seaward-dipping reflectors (SDRs) on buried volcanic margins. Mid-Miocene propagation of the Main Ethiopian rift (MER) arm into the Afar Depression led to overprinting of the early Red Sea rift structures. We suggest that the locus of strain in western Afar jumped from Upper Miocene Southern Red Sea magmatic segments to Plio-Quaternary MER magmatic segments. The distribution of strain across the western Afar margin, and age of SDR-like basalts and the intersecting Southern Red Sea and Main Ethiopian rifts suggests that the Southern Red Sea magmatic segments were abandoned in the Upper Miocene leaving SDRs stranded above Oligo-Miocene rift basins, possibly due to the northward propagation of the seismically and volcanically active MER.

Wolfenden, E.; Ebinger, C.; Yirgu, G.; Kelley, S.; Deino, A.; Renne, P.

2003-04-01

190

Quantitative climate reconstructions of the late Miocene Xiaolongtan megaflora from Yunnan, southwest China  

Microsoft Academic Search

The late Miocene Xiaolongtan megaflora from Kaiyuan in southeast Yunnan (23°48?45?N, 103°11?52?E, 1050 m a.s.l.) was chosen for palaeoclimatic reconstruction using three quantitative techniques, i.e. the Coexistence Approach (CA), Leaf Margin Analysis (LMA), and the Climate–Leaf Analysis Multivariate Program (CLAMP). The reconstructed climatic parameters are also compared with those of the two adjacent Miocene floras currently available in Yunnan, i.e. the

Ke Xia; Tao Su; Yao-Wu Xing; Frédéric M. B. Jacques; Zhe-Kun Zhou

2009-01-01

191

Oligo-Miocene foraminiferal record (Miogypsinidae, Lepidocyclinidae and Nummulitidae) from the Western Taurides (SW Turkey): Biometry and implications for the regional geology  

NASA Astrophysics Data System (ADS)

The marine Oligo-Miocene units of western Taurides, deposited under different tectonic regimes (in Bey Da?lar? platform in foreland and coeval sequences in hinterland), were studied to establish a high-resolution biostratigraphic framework. Biometric study of the full spectrum of larger foraminifera in a regional scale allowed us correlating them with the shallow benthic zonation (SBZ) system introduced by [Cahuzac, B., Poignant, A., 1997. Essai de biozonation de l'Oligo-Miocène dans les bassins européens à l'aide des grands foraminifères néritiques. Bulletin de la Société géologique de France 168, 155-169], and to determine the ages of these sites on zonal precision for the first time. In correlating these assemblages to standard shallow benthic zones, planktonic data were also used whenever possible. Taxa, classified under the genera Nummulites, Miogypsina, Miolepidocyclina, Nephrolepidina, Eulepidina, Heterostegina, Operculina and Cycloclypeus (?) and their assemblages, closely resemble to the fauna described from European basins. These groups characterize the SBZ 22B to 25 zones referring to a time interval from early Chattian to Burdigalian. However, a main gap in late Chattian (SBZ 23) and in early part of the Aquitanian (SBZ 24) is also recorded in the platform succession. In the meantime, rare Eulepidina in the Burdigalian levels suggest a clear Indo-Pacific influence. Based on the discovery of early Chattian (SBZ 22B) deposits (previously mapped under Eocene/Miocene units), the Oligo-Miocene stratigraphy of the Bey Da?lar? platform is also revised. A more precise chronology for regional Miocene transgression is presented based on the miogypsinid evolutionary scale.

Özcan, Ercan; Less, György; Báldi-Beke, Mária; Kollányi, Katalin; Acar, Ferhat

2009-05-01

192

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

SciTech Connect

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.

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

1986-07-01

193

Early Miocene origin and cryptic diversification of South American salamanders  

PubMed Central

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.

2013-01-01

194

Evolution of a Miocene sag basin in the Alboran Sea  

NASA Astrophysics Data System (ADS)

The Alboran domain represents the westernmost termination of the peri-Mediterranean Alpine orogen. Its arcuate shape, delimited to the North by the Betic range and to the South by the Rif range, is the result of subduction, collision and slab migration processes. During the Neogene, several sedimentary basins formed on the Betics metamorphic basement, mainly due to the extensional collapse of the previously thickened crust of the Betic-Rif belt. The major sedimentary depocentre, the Western Alboran Basin (WAB), is surrounded by the Gibraltar arc, the volcanic Djibouti mounts and the Alboran ridge, and is partly affected by shale tectonics and associated mud volcanism. High-quality 2-D seismic profiles acquired along the Moroccan margin during the last decade reveal a complete history of the basin. Our study deals with the analysis of seismic profiles oriented parallel and orthogonal to the Mediterranean Moroccan margin. The stratigraphy was calibrated using well data from offshore Spain and Morocco. Our study focuses particularly on the tectono-stratigraphic reconstruction of the basin. The formation of the WAB began in the Early Miocene (Aquitanian - Burdigalian). A massive unit of Early Miocene to Lower Langhian shales and olistostromes forms a thick mobile décollement layer that controls and accommodates deformation of the basin fill. From the Upper Langhian to the Upper Tortonian, the basin is filled by a thick sequence of siliciclastic deposits. Stratigraphic geometries identified on seismic data clearly indicate that deformation of the basin fill started during deposition of Upper Langhian to the Upper Tortonian clastics. Shale tectonic deformation was re-activated recently, during the Messinian desiccation of the Mediterranean Sea (and the following catastrophic Pliocene reflooding) or during the Quaternary contourite deposition The sedimentary layers gently dip towards the basin centre and "onlaps" onto the basin margin, especially onto the basement high that bounds the basin toward the East. The contacts observed between the sediment and the basement reflectors are purely stratigraphic. These observations confirm that the geometry is essentially that of a sag basin. We discuss all these stratigraphic observations in the scope of the geodynamic evolution of the eastern and western Alboran basin and the extension recorded onshore during the basin development time interval.

Do Couto, D.; Gorini, C.; Jolivet, L.; Letouzey, J.; Smit, J.; d'Acremont, E.; Auxietre, J. L.; Le Pourhiet, L.; Estrada, F.; Elabassi, M.; Ammar, A.; Jabour, H.; Vendeville, B.

2012-04-01

195

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

PubMed

Cypridoidean ostracods are one of a number of animal taxa that reproduce with giant sperm, up to 10 000 µm 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

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

2014-07-01

196

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

PubMed

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

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

2012-05-01

197

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

SciTech Connect

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.

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

1980-02-01

198

New gadiform fishes (Teleostei, Gadiformes) from the Miocene of Algeria  

NASA Astrophysics Data System (ADS)

As part of the completion of studies on the Miocene fishes of the Chelif Basin (north-western Algeria), this paper represents a contribution to the knowledge of the Messinian gadiform diversity of this western Mediterranean, semi-enclosed, Neogene basin. A new genus and species of the family Macrouridae is erected ( Razelainia paradoxa n. gen. et sp.), two specimens are tentatively referred to already existing taxa ( Gadiculus cf. jonas; Merluccius cf. merluccius), and a species formerly assigned to the gadid genus Brosme is transferred to the genus Gaidropsarus ( Gaidropsarus murdjadjensis). The macrourid Razelainia paradoxa n. gen. et sp. is characterized by an unusual combination of: plesiomorphic gadiform features, such as low vertebral number (presumed), well-developed caudal-fin rays, presence of a single continuous dorsal fin originating just posterior to the neurocranium, anal-fin rays slightly longer than dorsal-fin rays; and derived, typically macrourid features, such as the presence of spinoid scales and the anterior anal-fin pterygiophores extending forward over the abdominal wall. A paleoecological analysis reveals that the Messinian gadiform assemblage of the Chelif Basin had a subtropical/warm temperate affinity, with a marked north-eastern Atlantic-Mediterranean biogeographic character.

Carnevale, Giorgio

2007-02-01

199

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

USGS Publications Warehouse

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.

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

1998-01-01

200

Resource partitioning among top predators in a Miocene food web  

PubMed Central

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 (?13C) values from tooth enamel imply the presence of a woodland ecosystem dominated by C3 plants. ?13C 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 ?13C 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, ?13C 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.

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

2013-01-01

201

Dinoflagellates from the Miocene Rudeis and Kareem formations borehole GS78-1, Gulf of Suez, Egypt  

Microsoft Academic Search

The Miocene Rudeis and the Kareem formations encountered in the Neogene part of the GS-78-1 borehole, Gulf of Suez produced diverse assemblages of dinoflagellate cysts, spores and pollen. The Early Miocene (Burdigalian) age assigned to the Rudeis Formation and the Early-?Middle Miocene (Langhian–Serravallian) age postulated for the Kareem formation is based on the presence of dinoflagellate cysts. These offer a

Salah Y. El Beialy; Ali S. Ali

2002-01-01

202

New insights to the middle Miocene pCO2 problem (Invited)  

NASA Astrophysics Data System (ADS)

The climate of the middle Miocene was substantially different to today with a much warmer world with boundary conditions (plate configurations, ocean circulation etc) that were very different to the present. The sustained warmth of the 'Middle Miocene Climate Optimum' prevailed prior to the second step of the descent into the ice-house - with the major expansion of Antarctic ice sheet and global cooling at the middle Miocene Climate Transition. Coincident with these major changes in global temperatures and the cryosphere were substantial perturbations of the carbon cycle, as documented by the large fluctuations in oceanic carbonate ?13C values during the 'Monterey Excursion' as well as the various 'CM' events superimposed upon it. Critical to our understanding of Miocene climate and carbon cycle dynamics is a full understanding of atmospheric pCO2 during this fascinating time. A number of Miocene atmospheric pCO2 estimates are now available (Kürschner, Kva?ek and Dilcher, 2008; Foster, Lear and Rae, 2012; Badger et al., 2013) that help to better understand this relationship but differences between these new records and older published records (ie Pagani et al., 1999; Pearson and Palmer, 2000) raise interesting questions as to the drivers of Miocene climate and carbon cycling. Here we will discuss the implications of our records for the Monterey Excursion and the CM events, as well as presenting a novel probabilistic re-assessment of new and existing atmospheric pCO2 records. The combination of a larger dataset and more quantitative approach allows us to answer some of the outstanding questions about the operation of the Miocene climate system, and help to explain the apparent disparity between atmospheric pCO2 records and proxy temperature estimates.

Badger, M. P.; Foster, G. L.; Lear, C. H.; Pancost, R. D.; Bailey, T. R.; Leng, M. J.; Abels, H. A.

2013-12-01

203

Computer modeling a Miocene carbonate platform, Mallorca, Spain  

SciTech Connect

This paper describes a computer model based on algorithms that simulate processes of carbonate sediment production, deposition, erosion and redeposition, and sequence stratigraphy of carbonate platforms. We use the well-exposed cliff sections through the reef-rimmed Miocene carbonate platform of Mallorca, Spain, to test the ability of our program to simulate an outcropping stratigraphy. When an outcrop-derived sea level curve and the average Holocene rates of production and erosion are used in our model, we can precisely match the natural and the synthetic stratigraphies. In addition, we can reconstruct the nonoutcropping parts of the platform. This modeling indicates the ability of our program to simulate the sequence stratigraphy, stratal geometries, and facies of a real carbonate platform. This model also strongly suggests that the processes for which we have no field evidence and that we are not modeling, i.e., compaction, differential subsidence, and three-dimensional sedimentary processes, are unimportant factors in the development of the Llucmajor Platform of Mallorca. Modeling has contributed to three advances in carbonate platform analysis. First, this method is probably the best way to study the many effects that the different controlling parameters have on platform evolution. Secondly, if some parameters can be quantified from field analysis, then the other parameters can be bracketed from modeling. Thirdly, this method strongly suggests that the parameters we are not modeling have no important control on platform evolution. Accurate forward modeling of carbonate stratigraphies allows petroleum geologists to independently test sequence stratigraphic interpretations, reconstruct partially exposed or imaged carbonate stratigraphies, locate and quantify the cross sections of likely reservoir facies, illustrate the development and possible interconnections of reservoir facies, and predict stratigraphies around the basin rim. 41 refs., 9 figs., 1 tab.

Bosence, D.W.J.; Waltham, D.A.; Lankester, T.H.G. (Royal Holloway Univ., London (United Kingdom)); Pomar, L. (Universitat de les Illes Balears (Spain))

1994-02-01

204

Sedimentology of tidally deposited Miocene Bear Lake formation, Alaskan Peninsula  

SciTech Connect

The Miocene Bear Lake Formation - chiefly sandstone, shale, and conglomerate - crops out on the Alaskan Peninsula between Port Heiden and Pavlof Bay. As thick as 1600 m in outcrop and 2368 m in subsurface, the Bear Lake Formation appears to have been deposited mostly by tidal processes in a semi-enclosed back-arc basin that was bordered to the southeast by volcanic uplands of the Aleutian arc. To the northeast, the basin originally extended beneath Britstol Bay as part of the North Aleutian basin. The Bear Lake Formation, which rests unconformably on Oligocene volcanogenic sedimentary rocks and is unconformably overlain by Pliocene volcanic rocks, contains few, if any, interbedded volcanic rocks. Sandstone of the Bear Lake Formation contains more quartz, locally as much as 65%, than most Tertiary strata of the Alaska Peninsula. Rounded clasts of granitic rocks as large as 25 cm were probably derived from large batholithic complexes to the southeast. Sandstone beds are characterized by large-scale trough and tangential tabular cross-strata, herringbone cross-strata, shale drapes on cross-strata, reactivation surfaces, channeling, superposition of small-scale cross-strata or current ripple markings on large-scale cross-strata with reversal flow directions, scattered megafossils, local coquinas, and local burrows that include Ophiomorpha. Shaly sequences are characterized by flaser bedding, current and oscillation ripple markings, starved ripple markings, abundant small-scale bioturbation, load coasts, abundant mica and plant fragments, and synsedimentary slumps. Coarse-grained fluvial deposits at the base and fine-grained marine shelf deposits at the top of many sections suggest deposition during a major transgression, possibly as a result of subsidence of the Aleutian arc during an interval of relative volcanic quiescene.

Nilsen, T.H.

1985-04-01

205

Miocene/pliocene boundary and the terminal flood  

SciTech Connect

The boundary stratotype for the Miocene/Pliocene boundary, located at Capo Rosello, Sicily, occurs at a distinct lithostratigraphic change from Messinian evaporites to Zanclean open-marine sediments. Because bio- and magnetostratographic correlations of the stratotype with deep-sea sections have proven difficult, the authors propose to use strontium- and oxygen-isotope stratigraphies to correlate the earliest Pliocene at Capo Rosello with a marine sequence from the South Atlantic, DSDP Site 519. The Sr-isotope value of the sediments increases progressively between 6 and 4 Ma from approximately 0.708895 to 0.709026 with the M/P boundary at about 0.708948. Three cycles of rapid O-isotope fluctuations of 1.2 per thousand were recorded in the planktic forams between 5.10 and 4.96 Ma, which have been interpreted as an indication of unstable surface-current patterns related to a destabilization of the Antarctic ice sheet. The lowermost 11 m of the earliest Pliocene Trubi Fm. at Capo Rosello contains the MP1-1 and lowermost part of the MP1-2 zones and have an average Sr-isotope value of 0.708968, correlating them with the earliest Pliocene of Site 519. The sequence also contains 3 planktic cycles of O-isotope fluctuations of about 1.0 per thousands, which the authors correlate with the Site 519 cycles and interpret as global warmings and coolings related to climatic instability. They conclude that the terminal flooding of the Mediterranean at the M/P boundary resulted in global climatic disturbances possibly associated with a reorganization of oceanic circulation due to the renewed injection of Mediterranean bottom waters into the Atlantic Ocean.

McKenzie, J.A.; Mueller, P.; Mueller, D.

1985-01-01

206

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

NASA Astrophysics Data System (ADS)

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.

xu, J.

2013-12-01

207

Sequence stratigraphy, basin dynamics, and petroleum geology of the Miocene from eastern Tunisia  

SciTech Connect

On the eastern margin of Tunisia, Miocene limestones, marl, and siliciclastic deposits crop out poorly and are lacking in age-diagnostic faunal content. The biostratigraphic and lithostratigraphic subdivisions of these series are not clearly defined. A regional study of subsurface sequences of this margin (Cap Bon, Gulf of Hammamet, and Sahel) by means of sequence stratigraphy and subsurface structural analyses permits the identification of seven third-order sedimentary sequences of inferred Langhian to Messinian age, the boundaries of which are characterized by downlap and onlap/toplap relationships. These sequences include turbidites, sands, and sandstones deposited in connection with eustatic sea level changes and tectonic movements of east-west and south-north deep-seated faults due to the Alpine and Atlassic paroxysm. Stratal sequences are organized around Miocene syndepositional grabens, half-grabens, platforms, and folds occurring inside and outside of regional tectonic corridors. The geodynamic evolution of Miocene basins has led to the deposition of turbiditic black argillaceous source rocks, and sandstone and carbonate reservoirs that present new Miocene petroleum targets. The basin subsidence in response to the Alpine/Atlassic orogeny has permitted the maturation of Miocene source rocks, oil generation, and the formation of oil traps, stratigraphic pinch-outs, and structural enclosures on the flanks of folds and on the borders of grabens.

Bedir, M. [Campus Universitaire, Tunis (Tunisia)]|[Unite des Ressources Naturelles et Environnement, Hammam-Lif (Tunisia); Tlig, S. [Campus Universitaire, Tunis (Tunisia); Bobier, C. [Universite Bordeaux, Talence (France)] [and others

1996-01-01

208

Lithostratigraphy and vertebrate biostratigraphy of the early Miocene Himalayan Foreland, Zinda Pir Dome, Pakistan  

NASA Astrophysics Data System (ADS)

Deposits in the Sulaiman foothills and Zinda Pir Dome in west-central Pakistan provide new insight into the critical early Miocene record of Himalayan Foreland sedimentation and paleobiology. The Chitarwata Formation, which underlies the Vihowa Formation in the Sulaiman foothills predates the Siwalik deposits on the Potwar Plateau of north-central Pakistan and provides a record of mammals spanning the interval between the early Miocene Bugti fauna and middle Miocene to Pleistocene Siwalik faunas. Siwalik deposits on the Potwar Plateau are no older than middle Miocene; they represent fluvial environments. In contrast, the Chitarwata and Lower Vihowa Formations in the Zinda Pir Dome represent coastal-delta plain and fluvial environments, respectively. Biostratigraphic information from the Chitarwata Formation, coupled with paleomagnetic data (reported by Friedman et al., 1992) from coincident strata, suggest that coastal environments persisted in the area of the Sulaiman foothills until about 18.6 Ma when they were replaced by fluvial environments, probably representing the ancestral Indus River system. Apparently, during the early Miocene when sediments of the Chitarwata Formation were accumulating on the western portion of the Himalayan Foreland Basin much of the area of the Potwar Plateau to the north was being eroded. The overlying Vihowa Formation, along with the relatively contemporaneous Kamlial Formation on the Potwar Plateau, represent the appearance of widespread terrestrial sedimentation in the Himalayan Foreland Basin.

Downing, Kevin F.; Lindsay, Everett H.; Downs, William R.; Speyer, Stephen E.

1993-09-01

209

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

210

A generalized genetic framework for the development of sinkholes and Karst in Florida, U.S.A  

Microsoft Academic Search

Karst topography in Florida is developed on the Tertiary limestones of the Floridan aquifer Post-depositional diagenesis and\\u000a solution have made these limestones highly permeable, T=ca. 50,000 m2\\/d. Zones of megaporosity have formed at unconformities, and dissolution has enlarged joints and fractures Erosion of the\\u000a overlying clastic Miocene Hawthorn group strata on one flank of a structural arch has exposed the

Barry F. Beck

1986-01-01

211

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

USGS Publications Warehouse

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

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

1993-01-01

212

A new species of Shaanxispira (Bovidae, Artiodactyla) from the upper Miocene of China.  

PubMed

A new species of the bovid Shaanxispira, from the upper Miocene deposits of the Linxia Basin, Gansu Province, China, is described here. Shaanxispira is endemic to Northern China and was previously known only from the Lantian area, Shaanxi Province, by two species, S. chowi and S. baheensis. The new species, S. linxiaensis nov. sp., is of early Bahean in age, slightly older than the species from the Lantian area. The horn-cores of the new species are more derived, with large wing-shaped antero-medial keels, suggesting the occurrence of a different lineage of Shaanxispira in the Linxia Basin. Although Shaanxispira has homonymously twisted horn-cores, it is not closely related to other late Miocene bovids with homonymously twisted horn-cores, like Oioceros and Samotragus. Its phylogenetic status is still in debate, but might be more closely related to the late Miocene "ovibovines."  PMID:24870338

Shi, Qinqin; He, Wen; Chen, Shanqin

2014-01-01

213

The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of terrestrial ecosystems  

PubMed Central

The Miocene is characterized by a series of key climatic events that led to the founding of the late Cenozoic icehouse mode and the dawn of modern biota. The processes that caused these developments, and particularly the role of atmospheric CO2 as a forcing factor, are poorly understood. Here we present a CO2 record based on stomatal frequency data from multiple tree species. Our data show striking CO2 fluctuations of ?600–300 parts per million by volume (ppmv). Periods of low CO2 are contemporaneous with major glaciations, whereas elevated CO2 of 500 ppmv coincides with the climatic optimum in the Miocene. Our data point to a long-term coupling between atmospheric CO2 and climate. Major changes in Miocene terrestrial ecosystems, such as the expansion of grasslands and radiations among terrestrial herbivores such as horses, can be linked to these marked fluctuations in CO2.

Kurschner, Wolfram M.; Kvacek, Zlatko; Dilcher, David L.

2008-01-01

214

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

SciTech Connect

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.

Cullen, A.B. [Univ. of Oklahoma, Norman, OK (United States)

1996-05-01

215

Paleoceanographic change during the Middle Miocene climate revolution: An Antarctic stable isotope perspective  

NASA Astrophysics Data System (ADS)

Ocean circulation and atmospheric pCO2 variations have been cited as potential mechanisms driving middle Miocene cooling and Antarctic cryosphere expansion. Well-dated high latitude (˜55°S) benthic foraminifer stable isotope records from the South Tasman Rise (STR; ODP Sites 1170 and 1171) exhibit familiar patterns of long and short term middle Miocene climate change and inferred carbon cycle dynamics. STR records illustrate the major middle Miocene ?18O increase (1.2‰) between 14.01 and 13.77 Ma. STR ?18O and ?13C records covary between 16.5 and 13.5 Ma. Integrated STR and southwest Pacific (0-55°S) stable isotope time series and time slice data indicate regional ocean circulation changes (>1500 m) commensurate with the middle Miocene global climate transition (16.8-12 Ma). STR stable isotopes and southwest Pacific meridional ?13C gradients suggest that Warm Saline Deep Water from the Tethys Sea dominated regional bottom waters (>1500 m) between 16.8 and 16.2 Ma, during the peak of the Miocene Climatic Optimum (MCO), and exerted intermittent influence on the STR (˜55°S) until the end of the MCO (˜13.8 Ma). A shift from low to high latitude sourced intermediate and deep waters occurred at ˜16.2 Ma. Southern Ocean derived Southern Component Water influenced the STR (>1500 m) beginning at 16.2 Ma and dominated the southwest Pacific (1500-2100 m; 0-55°S) from 14.9 to 14.2 Ma and 13.8 to 12 Ma. Although ?18O and ?13C coherence suggests some role for pCO2, these findings support hypotheses relating middle Miocene cooling and Antarctic cryosphere development to reorganization of oceanic circulation and meridional heat flux.

Shevenell, A. E.; Kennett, J. P.

216

Miocene hydrovolcanism in NW Colorado, USA, fuelled by explosive mixing of basic magma and wet unconsolidated sediment  

Microsoft Academic Search

The Yampa and Elkhead Mountains volcanic fields were erupted into sediment-filled fault basins during Miocene crustal extension in NW Colorado. Post-Miocene uplift and erosion has exposed alkali basalt lavas, pyroclastic deposits, volcanic necks and dykes which record hydrovolcanic and strombolian phenomena at different erosion depths. The occurrence of these different phenomena was related to the degree of lithification of the

P. T. Leat; R. N. Thompson

1988-01-01

217

A new early species of the aquatic sloth Thalassocnus (Mammalia, Xenarthra) from the Late Miocene of Peru  

Microsoft Academic Search

Thalassocnus antiquus, sp. nov., is a marine nothrothere from the late Miocene Aguada de Lomas vertebrate horizon (ca. 7 to 8 Ma) of the Pisco Formation in the Sacaco area of the southern coast of Peru. It is similar to the slightly younger latest Miocene Thalassocnus natans, but smaller and distinctly more gracile. The sloping morphology of the lateral border

Christian De Muizon; H. Gregory Mcdonald; Rodolfo Salas; Mario Urbina

2003-01-01

218

14. EARLY TO MIDDLE MIOCENE SEQUENCES, SYSTEMS TRACTS, AND BENTHIC FORAMINIFERAL BIOFACIES, NEW JERSEY COASTAL PLAIN 1  

Microsoft Academic Search

We identified and dated nine lower to middle Miocene sequences at the Island Beach, Atlantic City, and Cape May, New Jersey boreholes, integrating Sr-isotopic, lithofacies, log, and benthic foraminiferal biofacies data in a sequence stratigraph ic framework. Miocene sequences typically shallow upsection, representing three major lithofacies: (1) thin, shelly, glauconite sands of the Transgressive Systems Tracts deposited in inner-middle (0-

Kenneth G. Miller; Scott Rufolo; Peter J. Sugarman; Stephen F. Pekar; James V. Browning; David W. Gwynn

219

Four new species of benthonic foraminifera from the Miocene of Trinidad, West Indies, and their palaeobiogeographic importance  

Microsoft Academic Search

Four new species of benthonic foraminifera (Textularia carrbrowni, T. framptoni, T. sawhi and Bolivina jiattongi) are described from the middle and upper Miocene of Trinidad, West Indies. Textularia carrbrowni n. sp. has previously been illustrated from the Miocene of Puerto Rico as T. articulata D?ORBIGNY, in turn originally described from the Vienna Basin, Austria. The recognition of T. carrbrowni as

Brent WILSON

220

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

PubMed Central

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.

2012-01-01

221

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

SciTech Connect

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.

Ratcliff, C.D.; Geissman, J.W.; Perry, F.V. (Univ. of New Mexico, Albuquerque, NM (United States)); Crowe, B.M. (Los Alamos National Lab., Las Vegas, NV (United States))

1993-04-01

222

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

PubMed

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

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

2006-09-12

223

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

USGS Publications Warehouse

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.

Gibson, T. G.

1965-01-01

224

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

USGS Publications Warehouse

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. ?? 1984 Springer-Verlag New York Inc.

McLean, H.; Howell, D. G.

1984-01-01

225

Amber from western Amazonia reveals Neotropical diversity during the middle Miocene  

PubMed Central

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.

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

2006-01-01

226

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

227

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

NASA Astrophysics Data System (ADS)

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 Anadón 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.

Ortí, Federico; Rosell, Laura; Anadón, Pere

2010-07-01

228

Mediterranean proto-sapropels in the Middle Miocene: implications for the strength of the African monsoon and link to Miocene glaciations  

NASA Astrophysics Data System (ADS)

The strength of the African monsoon is known to have played a major role in determining sedimentation patterns in the Mediterranean during the Plio-Pleistocene. Increased meteoric water input by strong monsoons reduced surface water salinity, and the resulting slower water-mixing rate triggered the deposition of organic-rich layers called "sapropels". Here we present some proxy data coming from a mixed siliciclastic-carbonate section outcropping on the Maltese Islands that suggests that sapropels deposits already existed in the Middle Miocene. This implies that an enhanced monsoonal climate was likely active at that time. Our primary evidences for the existence of "proto-sapropels" are runoff proxies (clay mineral assemblages and abundance) coupled with oxygen isotopes. These indicate that a direct link existed between increased runoff regarded here as a proxy for the strength of the Monsoon- and Miocene global climate (Antarctic glaciation). Each Miocene phase of glaciation is reflected in the section as an increased flux of continental-derived material. Moreover, stable isotopes of carbon and Corg:Norg ratio analyses of organic matter revealed a higher mixing rate of terrigenous and marine organic matters during times of increased sedimentation. This is in good agreement with a monsoon model where increased sedimentation is linked to increased continental runoff. Spectral analysis of the section revealed the presence of Milankovitch-scaled cycles with a strong 100 k.y. frequency. Astronomically calibrated age model for the section shows that the African monsoon has probably initiated around 16.7 Ma and underwent a major strengthening around 13.8 Ma, a time corresponding to enhanced siliciclastic deposition on the Malta-Ragusa platform and to the global cooling phase of the Mi3 Antarctic ice-buildup phase. We argue that the strong coherence between Miocene glaciation phases and increased runoff into the Mediterranean is due to a link between Antarctic cooling, Northward migration of the ITCZ due to increased thermal gradient, and enhances precipitation over North Africa.

John, C. M.; Mutti, M.; Adatte, T.; Laskar, J.

2003-04-01

229

Carbonate platform growth and demise offshore Central Vietnam: Effects of Early Miocene transgression and subsequent onshore uplift  

NASA Astrophysics Data System (ADS)

Miocene carbonate platforms cover a large part of the Central Vietnamese South China Sea margin. Early carbonate deposition took place on two regional platforms separated by a narrow depression developed along the trace of the East Vietnam Boundary Fault Zone. West of the East Vietnam Boundary Fault Zone, the Tuy Hoa Carbonate Platform fringes the continental margin between Da Nang and Nha Trang. Here, platform growth initiated during the Early Miocene and continued until Middle Miocene time when regional uplift led to subaerial exposure, termination of platform growth and karstification. East of the fault zone, the Triton Carbonate Platform was also initiated during the Early Miocene. Carbonate growth thrived during Early and part of Middle Miocene time and a thick, clean Lower and Middle Miocene carbonate succession cover the Triton Horst and the Qui Nhon Ridge. During the Middle Miocene, partial drowning resulted in the split-up of the Triton Carbonate Platform. Repeated partial drowning events throughout the Middle and Late Miocene resulted in westwards retreat of platform growth and eventual platform drowning and termination of carbonate deposition. Modern carbonate growth continues on isolated platforms hosting the Paracel Islands farther seawards. The onset of widespread carbonate deposition largely reflects the Early Miocene transgression of the area linked with early post-rift subsidence and the opening of the South China Sea. The mid-Neogene shift in carbonate deposition is interpreted as a consequence of regional uplift and denudation of central and south Indochina starting during Middle Miocene time when the Tuy Hoa Carbonate Platform became subaerially exposed. Stressed carbonate growth conditions on the Triton Carbonate Platform probably resulted from increased inorganic nutrient input derived from the uplifted mainland, possibly enhanced by deteriorated climatic conditions and rapid sea-level fluctuations promoting platform drowning.

Fyhn, Michael B. W.; Boldreel, Lars O.; Nielsen, Lars H.; Giang, Tran C.; Nga, Le H.; Hong, Nguyen T. M.; Nguyen, Nguyen D.; Abatzis, Ioannis

2013-10-01

230

High-resolution record of Early to Middle Miocene climate variability from Site 1195, Marion Plateau, NE Queensland margin  

NASA Astrophysics Data System (ADS)

Constraining and quantifying eustatic variations has been a priority for stratigraphers since the publication of the first global sea level curves by the Exxon research group in the late 1970s. Quantifying the glacio-eustatic component of sea level signals has become a greater focus as more recent work has demonstrated that far-field effects like ice-sheet gravitation and isostasy imprint on the "true" eustatic signal of waxing and waning ice sheets so that coeval signals from disparate sites may show significantly different local sea level variations. To this end, the Miocene sediments on the Marion Plateau, a drowned carbonate platform on the Queensland margin of Australia, were drilled by ODP Leg 194 to provide an independent, southern hemisphere test of the sea level record of the New Jersey Margin of North America, the most complete and oft-cited record of Cenozoic sea level variability. A high-resolution record is critical to compare sea level variations across hemispheres. Natural Gamma Ray (NGR) logs of core holes can provide a complete, high-resolution record independent of any problems with core recovery or sampling interval. We here present a NGR record of ODP Site 1195 tied to recently completed nannofossil assemblage data, planktic/benthic foraminiferal ratios, sedimentary particle counts, and benthic foraminifera stable isotopes. Peaks in glauconite and clay content correspond to peaks in NGR. The largest of these peaks correspond to sequence boundaries (lowstands), as glauconite accumulates during periods of low sedimentation along this carbonate-dominated margin. These sequence boundaries, in turn, are each associated with marine oxygen isotope events ("Mi Events") and correlate to sequences on the New Jersey margin, the Gulf of Papua, Great Australian Bight, and McMurdo Sound, indicating that these sequences are eustatically controlled. Although sedimentary particle counts only show strong peaks of glauconite at sequence boundaries, the NGR record shows long-period, low-amplitude variations in NGR between 20 and 18 Ma, a time corresponding to a pre-platform muddy ramp, short-period, high-amplitude variations between 18 and 14.8 Ma, a period of higher sea levels during the Miocene Climatic Optimum (MCO) and a dramatic spike corresponding to Mi3a at 14.8 Ma during the Middle Miocene Climate Transition (MMCT) followed by a slow decrease in the amplitude and frequency of variation during subsequent Antarctic ice growth and the drowning of the Marion Plateau. The variations in the NGR profile correspond directly (at a higher resolution) to variations in the oxygen isotope record, allowing us to create a cyclostratigraphic record that reflects fluctuations in oxygen isotopes. Calcareous nannofossil populations respond to variations in surface water nutrient availability and temperature; these changes coincide with climatic events of the early Miocene, including the MCO, the MMCT and the stepwise formation of ice sheets on Antarctica (<13.6 Ma). Calcareous nannofossil data show evidence for significantly cooler surface water at the Marion Plateau coinciding with the end of the MCO.

Lowery, C.; Browning, E.; Leckie, R. M.; John, C. M.

2012-12-01

231

Paleogeographic evolution of the Late Miocene Lake Pannon in Central Europe  

Microsoft Academic Search

The paleogeographic evolution of Lake Pannon within the Pannonian basin is reconstructed with eight maps, ranging from the Middle Miocene to the Early Pliocene. The maps are based on the distribution of selected biozones and specific fossils, and on complementary sedimentological and seismic information. Our reconstruction shows that the history of Lake Pannon can be divided into three distinct intervals:

Imre Magyar; Dana H Geary; Pál Müller

1999-01-01

232

Miocene basalts in northwestern Taiwan: Evidence for EM-type mantle sources in the continental lithosphere  

NASA Astrophysics Data System (ADS)

Cenozoic extension around the Taiwan Strait resulted in intraplate basalt volcanism in the Fujian-Taiwan region of the southeastern China continental margin. In northwestern Taiwan, the basalt volcanism took place in two distinct periods: the early Miocene (23-20 Ma), with the eruption of alkali basalt only, and the late Miocene (13-9 Ma), marked by the emplacement of various basalt types. The early Miocene basalts have uniform Sr?Nd?Pb isotope compositions comparable with those of the other Fujian-Taiwan basalts, which are believed to have originated from a "plum-pudding" type convecting mantle. These basalts display EM2-type lead isotope signature like that observed in seamount basalts from the South China Sea. By contrast, the late Miocene basalts show distinctive isotope characteristics indicating additional involvement of an EM1-type mantle source that has never been identified before for any volcanics in southern China. We propose that the "enriched mantle" components (EMI and EM2) reside in different levels of the continental lithospheric mantle. Reactivation of the unique EM1 source may be ascribed to the arc-continent collision in Taiwan during the last 12 million years which terminated the intraplate volcanism around this region.

Chung, Sun-Lin; Jahn, Bor-Ming; Chen, Shu-Jen; Lee, Typhoon; Chen, Cheng-Hong

1995-02-01

233

Oligocene\\/Miocene Beds and Faunas from Tieersihabahe in the Northern Junggar Basin of Xinjiang  

Microsoft Academic Search

A mid-Tertiary rock sequence at the Tieersihabahe locality from the Ulungur River area in the northern Junggar Basin, Xinjiang Province, China, is described. The study introduces three late Oligocene\\/Early Miocene faunas from the continuous section of the ''Ulunguhe'' and Suosuoquan formations within the sequence, and discusses the age determination, faunal cor- relation, and existing problems concerning the formations and faunas.

YE JIE; MENG JIN; WU WENYU

2003-01-01

234

Post-evaporitic restricted deposition in the Middle Miocene Chokrakian-Karaganian of East Crimea (Ukraine)  

Microsoft Academic Search

In the Middle Miocene of East Crimea, gypsum evaporites formed in a shallow basin from mixed seawater–nonmarine waters are overlain by marl, siltstone and claystone which contain a few horizons of stromatolitic limestone. The thickness and abundance of the stromatolitic horizons increase up the section. In the siliciclastic portion of the section, a very poor and taxonomically impoverished assemblage of

Tadeusz Marek Peryt; Danuta Peryt; Marek Jasionowski; Andriy V Poberezhskyy; Tomasz Durakiewicz

2004-01-01

235

Postcranial skeleton of the Miocene marsupial Palaeothentes (Paucituberculata, Palaeothentidae): paleobiology and phylogeny  

Microsoft Academic Search

This contribution presents a morphofunctional analysis of the previously unknown appendicular skeleton of the paucituberculatans Palaeothentes minutus and Palaeothentes lemoinei from the Santa Cruz Formation (late early Miocene, Santa Cruz province, Argentina), performed in order to infer their locomotor behavior. In addition, a cladistic analysis was conducted to explore the phylogenetic information of postcranial features of Palaeothentes in the context

MARÍA ALEJANDRA ABELLO; ADRIANA MAGDALENA CANDELA

2010-01-01

236

Spatangoid-produced ichnofabrics (Bateig Limestone, Miocene, Spain) and the preservation of spatangoid trace fossils  

Microsoft Academic Search

A spatangoid-produced ichnofabric is described from the Miocene Bateig Limestone, SE Spain. This ichnofabric is characterized by the dominant presence of large meniscate burrows (Bichordites) produced by irregular echinoids. This constitutes an unusual mode of occurrence for spatangoid bioturbation, as their traces are most typically preserved in bases and tops of sandstone event beds. In fact, despite their important role

J. M. de Gibert; Roland Goldring

2008-01-01

237

Trace fossils on penguin bones from the Miocene of Chubut, southern Argentina  

Microsoft Academic Search

Several traces of biological interaction were found on penguin bones from the basal levels (Aquitanian) of the Miocene Gaiman Formation in the lower Chubut valley of the Provincia del Chubut, Argentina. The fossil-bearing beds were deposited in littoral to sublittoral environments within sediments of mostly pyroclastic origin. We interpret many traces to have been produced by predators and\\/or scavengers while

Alberto Luis Cione; Carolina Acosta Hospitaleche; Leandro Martín Pérez; Jose Herminio Laza; Inés César

2010-01-01

238

Migration of sharks into freshwater systems during the Miocene and implications for Alpine paleoelevation  

Microsoft Academic Search

Trace-element and isotopic compositions of fossilized shark teeth sampled from Miocene marine sediments of the north Alpine Molasse Basin, the Vienna Basin, and the Pannonian Basin generally show evidence of formation in a marine environment under conditions geochemically equivalent to the open ocean. In contrast, two of eight shark teeth from the Swiss Upper Marine Molasse locality of La Molière

László Kocsis; Torsten W. Vennemann; Denis Fontignie

2007-01-01

239

Miocene sharks in the Kendeace and Grand Bay formations of Carriacou, The Grenadines, Lesser Antilles  

Microsoft Academic Search

The Miocene chondrichthyan fauna from the Kendeace and Grand Bay formations consists of five species which have been identified from the remains of teeth. These are Carcharias taurus (sand-tiger shark), Isurus oxyrinchus (shortfin mako shark), Carcharocles megalodon (mega-tooth shark), Carcharhinus obscurus (requiem shark) and Hemipristis serra (extinct snaggletooth shark). No further skeletal fish remains, Chondrichthyes or Actinopterygii, were discovered. Teeth

ROGER W. PORTELL; G ORDON HUBBELL; S TEPHEN K. DONOVAN; J EREMY L. GREEN; DAVID A. T. HARPER; RON PICKERILL

240

Sequence stratigraphy, basin dynamics, and petroleum geology of the Miocene from eastern Tunisia  

Microsoft Academic Search

On the eastern margin of Tunisia, Miocene limestones, marl, and siliciclastic deposits crop out poorly and are lacking in age-diagnostic faunal content. The biostratigraphic and lithostratigraphic subdivisions of these series are not clearly defined. A regional study of subsurface sequences of this margin (Cap Bon, Gulf of Hammamet, and Sahel) by means of sequence stratigraphy and subsurface structural analyses permits

M. Bedir; S. Tlig; C. Bobier

1996-01-01

241

Lower Miocene Stratigraphy along the Panama Canal and Its Bearing on the Central American Peninsula  

Microsoft Academic Search

Before the formation of the Central American Isthmus, there was a Central American Peninsula. Here we show that southern Central America existed as a peninsula as early as 19 Ma, based on new lithostratigraphic, biostratigraphic and strontium chemostratigraphic analyses of the formations exposed along the Gaillard Cut of the Panama Canal. Land mammals found in the Miocene Cucaracha Formation have

Michael Xavier Kirby; Douglas S. Jones; Bruce J. MacFadden; Ken Campbell

2008-01-01

242

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

SciTech Connect

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.

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

1988-02-01

243

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

USGS Publications Warehouse

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.

Barron, J. A.

1976-01-01

244

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

PubMed

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

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

2006-06-01

245

The Biomarker Properties and Comparisons of ?ahinali, Beypazari and Karapinar (Turkey) Coaly Plio-Miocene Depositions  

NASA Astrophysics Data System (ADS)

The distribution values of m/z 191 triterpane and m/z 217 sterane of coaly Plio-Miocene units determined by GC-MS were used to compare biomarker properties of ?ahinali, Beypazar? and Karap?nar areas located in Ayd?n, Ankara and Konya (Turkey) regions within this study. In the ?ahinali (Ayd?n) region the Miocene units consist of conglomerate, coal, clayey coal, sandstone, siltstone, claystone, clayey limestone and silicified limestone. Middle-Upper Miocene units of the Beypazar? (Ankara) Basin are represented by conglomerate, agglomerate, sandstone, siltstone, claystone, coal, bituminous shale, limestone, and tuff. The Pliocene Karap?nar (Konya) area of interest, which is characterized by sandstone, siltstone, claystone, mudstone, lake and river bed coal deposits. When all the biomarker values are considered, it can be concluded that the organic matter is not mature. In two areas - except ?ahinali - gammacerane is present indicating salinity. According to the C27, C28 ve C29 sterane distribution, it can be observed that the dominant organic matter is terrestrial based and accompanied by simple herbaceous and alg. The deposition conditions are seen to be anoxic even though some oxic depositions are found in areas. All the areas had oleananes indicating angiosperm presence. C29/C30 hophane ratio and decrease in C31-C35 peak height indicated detrial facies in all the areas. Key Words: Plio-Miocene, Coal, Biomarker, Turkey

Unal, Neslihan; Hokerek, Selin; Altunsoy, Mehmet; Ozcelik, Orhan; Yalcin Erik, Nazan

2014-05-01

246

Paleomagnetism of the Miocene Grotto and Snoqualmie Batholiths, Central Cascades, Washington  

Microsoft Academic Search

Palcomagnetic data have been obtained from granitic rocks of the Miocene Grotto and Snoqualmie batholiths in the Central Cascades, Washington. Alternating field magnetic dleaning demonstrated that a wide range of magnetic stability was present and that many specimens were unsuitable for palcomagnetic analysis. A simple statistic (Qa'), defined as the ratio of remanent magnetic intensity of the entire sample after

Suzanne J. Beske; Myrl E. Beck; Linda Noson

1973-01-01

247

Circum-Mediterranean Oligo–Miocene biogeographic evolution – the gastropods’ point of view  

Microsoft Academic Search

Based on studies in Iran (Qom Basin, Esfahan–Sirjan Basin, Zagros Mountains), in Turkey (Mut and Sivas basins), in the Mesohellenic Basin, and in northeastern Egypt, a new palaeobiogeographic concept for the Oligocene and Miocene in the circum-Mediterranean area with special emphasis on the distribution patterns of gastropod faunas is presented. A very strict biogeographic terminology is proposed to avoid the

Mathias Harzhauser; Werner E. Piller; Fritz F. Steininger

2002-01-01

248

Early Miocene benthic foraminifera and biostratigraphy of the Qom Formation, Deh Namak, Central Iran  

Microsoft Academic Search

A total of 165 samples were collected from the Qom Formation investigated in a stratigraphic section north of Deh Namak, in Central Iran. From these, 35 genera and 47 species of benthic foraminifera were identified. The age of the studied section is Early Miocene (Aquitanian to Early Burdigalian) based on the occurrence of Borelis melo curdica, Meandropsina anahensis, Meandropsina iranica,

Jahanbakhsh Daneshian; Leila Ramezani Dana

2007-01-01

249

Late Miocene Coral faunas of Iran (Zagros, Aghar, Firuz abad, Fars) palaeoecology and palaeobiogeography  

Microsoft Academic Search

Late Miocene Corals assemblage from Zagros Iran are investigated with respect to their palaeoecology and palaeobiogeography implications. This Corals are compared with fauna from Mediterranean Tethys and the Indopacific. Small foraminifers are used for biogeography and to support paleoecology interpretation. The studied section situated in the Zagros Mishan F.m is last depositions sea. A distinct horizon characterized by Porites- Antiguastrea

M. Dehbozorgi; M. Yazdi; H. Torabi

2009-01-01

250

Late Miocene Coral faunas of Iran (Zagros, Aghar, Firuz abad, Fars) palaeoecology and palaeobiogeography  

NASA Astrophysics Data System (ADS)

Late Miocene Corals assemblage from Zagros Iran are investigated with respect to their palaeoecology and palaeobiogeography implications. This Corals are compared with fauna from Mediterranean Tethys and the Indopacific. Small foraminifers are used for biogeography and to support paleoecology interpretation. The studied section situated in the Zagros Mishan F.m is last depositions sea. A distinct horizon characterized by Porites- Antiguastrea assemblage associated Milliolid and Rotalia is interpreted a shallow bioclastic shoal. Patch reef with a porites and faviidae assemblage are a common feature of Oligocene and Miocene coral occurrence and indicate water depth of less than 20m. The diversity of corals in this area are low and all corals are hematypic. Miocene Corals from Mishan F.m Comprise 7 genera and occur in the single horizon or patch reef. This Corals and patch reefs are compared with corals and patch reefs in Qom F.m Central Iran. This corals report from this section: Antiguastrea sp., Monastrea sp., Favites sp., Porites sp., Dichocoenia sp., Asterohelia sp., Leptoria sp. Keywords: Miocene- Iran- Mishan-Zagros- Formation- Tethys seaway- Corals- Palaeoecology- palaeobiogeography.

Dehbozorgi, M.; Yazdi, M.; Torabi, H.

2009-04-01

251

Anthracothere dental anatomy reveals a late Miocene Chado-Libyan bioprovince  

PubMed Central

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.

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

2006-01-01

252

Miocene vegetation pattern and climate change in the northwestern Central Paratethys domain (Czech and Slovak Republic)  

NASA Astrophysics Data System (ADS)

The case study area covers the slopes of the tectonically quiet European platform and foreland of the tectonically active Carpathian mountain chain (Carpathian Foredeep and Vienna Basin). Therefore the research on pollen spectra mirrors not only the evolution of landscape in two areas with different geodynamics, but also climatic changes in the Central Paratethys domain during the studied time interval. According to the pollen data, the Early to Middle Miocene vegetation reflects subtropical climate with very mild (negligible) cooling events during this period. This is indicated by common occurrence of thermophilous taxa in the whole sedimentary record. The Middle Miocene landscape evolution, conditioned by uplift of the Carpathian mountain chain and subsidence of adjacent lowlands, led to commencement of the altitudinal zonation. The terrestrial and aquatic ecosystems confirm a subtropical climate (Miocene Climatic Optimum, Mi3 event) with some possible long term changes in humidity. The Late Miocene paleogeographical changes, but also general climatic oscillations in the northwestern Central Paratethys realm, resulted in decrease of the number of thermophilous taxa during this time (change in latitudinal position of the vegetation cover). Variously high mountain relief of the uplifted mountain chains (altitudinal zonality) created ideal conditions for mixed mesophytic forests (to open woodland — open grassland type), still with presence of evergreen taxa. A subtropical climate with gradual transition to warm temperate climatic conditions is supposed on the basis of the reconstructed vegetation cover.

Ková?ová, Marianna; Doláková, Nela; Ková?, Michal

2011-06-01

253

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

Microsoft Academic Search

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

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

2010-01-01

254

Levoglucosan and other cellulose and lignin markers in emissions from burning of Miocene lignites  

Microsoft Academic Search

Levoglucosan (L), mannosan (M), galactosan (G) and other cellulose and lignin markers from burn tests of Miocene lignites of Poland were determined by gas chromatography–mass spectrometry (GC–MS) to assess their distributions and concentrations in the smoke. Their distributions were compared to those in the pyrolysis products of the lignites. Levoglucosan and other anhydrosaccharides are products from the thermal degradation of

Daniele Fabbri; Cristian Torri; Bernd R. T. Simoneit; Leszek Marynowski; Ahmed I. Rushdi; Monika J. Fabia?ska

2009-01-01

255

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

NASA Astrophysics Data System (ADS)

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.

Cheneval, Jacques; Ginsburg, Léonard; Mourer-Chauvire, Cécile; Ratanasthien, Benjavun

256

Fossil Mushrooms from Miocene and Cretaceous Ambers and the Evolution of Homobasidiomycetes  

Microsoft Academic Search

Two species of fossil mushrooms that are similar to extant Tricholomataceae are described from Cretaceous and Miocene ambers. Archaeomarasmius leggettigen. 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

David S. Hibbett; David Grimaldi; Michael J. Donoghue

1997-01-01

257

Tectonic control on the evolution of the fluvial systems of the Vinchina Formation (Miocene), northwestern Argentina  

Microsoft Academic Search

The Miocene Vinchina Formation accumulated in a large foreland basin is related to the uplift of the Andes Mountains. This 5100m thick unit was mostly deposited in fluvial environments, but short episodes of eolian and lacustrine sedimentation also occurred. Low-angle intraformational unconformities and dramatic facies changes define three depositional sequences. Sequence S1 is composed of sandstones and mudstones deposited in

C. Limarino; A. Tripaldi; S. Marenssi; L. Net; G. Re; A. Caselli

2001-01-01

258

Biogeographical and phylogenetic implications of an early Miocene wren (Aves: Passeriformes: Acanthisittidae) from New Zealand  

Microsoft Academic Search

A new species and genus of acanthisittid wren (Aves: Passeriformes: Acanthisittidae) is described from the Early Miocene (19–16 Ma) St Bathans Fauna from Otago, New Zealand, based on four fossil bones. The first Tertiary fossil passerine to be described from New Zealand, it is similar in size to New Zealand's smallest extant bird, the Rifleman Acanthisitta chloris. A phylogenetic analysis

Trevor H. Worthy; Suzanne J. Hand; Jacqueline M. T. Nguyen; Alan J. D. Tennyson; Jennifer P. Worthy; R. Paul Scofield; Walter E. Boles; Michael Archer

2010-01-01

259

Microbial community structure and biogeochemistry of Miocene subsurface sediments: implications for long-term microbial survival  

Microsoft Academic Search

Thirty closely spaced cores were obtained from Miocene-aged fluvial, lacustrine and palaeosol subsurface sediments ranging in depth from 173 to 197 m at a site in south- central Washington to investigate the size and composition of the microbial community in relation to sediment geochemical and geophysical properties. Total phospholipid fatty acid (PLFA) analysis indicated that the greatest concentrations of microbial

J. K. FREDRICKSON; J. P. MCKINLEY; S. A. NIERZWICKI-BAUER; D. C. WHITE; D. B. RINGELBERG; S. A. RAWSON; SHU-MEI LI; F. J. BROCKMAN; B. N. BJORNSTAD

1995-01-01

260

An rbcL Sequence from a Miocene Taxodium (Bald Cypress)  

Microsoft Academic Search

During the past decade, ancient DNAs from both animals and plants have been successfully extracted and analyzed. Recently, the age 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

Pamela S. Soltis; Douglas E. Soltis; Charles J. Smiley

1992-01-01

261

A new Miocene pinniped in the genus Prototaria (Carnivora: Odobenidae) from the Moniwa Formation, Miyagi, Japan  

Microsoft Academic Search

A new fossil odobenid skull from the late early or early middle Miocene age Moniwa Formation, Miyagi Prefecture, northern Japan, represents a new species of the genus Prototaria Takeyama and Ozawa, 1984. Prototaria planicephala, sp. nov., is distinguished from P. primigena Takeyama and Ozawa, 1984, by having a dorsoventrally flattened cranium with a wider rostrum, more derived cheek teeth, and

Naoki Kohno

1994-01-01

262

NEW LATE MIOCENE ELEPHANTOID (MAMMALIA: PROBOSCIDEA) FOSSILS FROM LEMUDONG'O, KENYA  

Microsoft Academic Search

The late Miocene marked a time of significant geographic dispersal and radiation for many mammalian taxa within Africa, including the proboscidean lineages. The ,6.1 Ma site of Lemudong'o, Kenya, yielded two elephantoid specimens. The first is a mandibular fragment with the third molar. This specimen represents a primitive member of the Anancus kenyensis lineage, with similarities to a specimen from

HARUO SAEGUSA; LESLEA J. HLUSKO

263

Functional Morphological Similarities in the Locomotor Skeleton of Miocene Catarrhines and Platyrrhine Monkeys  

Microsoft Academic Search

Noncercopithecid Miocene catarrhines share numerous features of their postcranial skeleton with extant platyrrhines, particularly pitheciines, cebines, and atelines. For any given fossil taxon, these similarities do not extend throughout the skeleton. Also there may be similarities to more than one platyrrhine taxon, within different parts of the postcranium, or even within a single bone. These similarities are of two types.

M. D. Rose

1996-01-01

264

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

NASA Astrophysics Data System (ADS)

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.

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.; González, J. J.; Escutia, C.

2013-12-01

265

Tectono-stratigraphic evolution of the continental Miocene basins in southern Anatolia  

NASA Astrophysics Data System (ADS)

The exposed portion of the Tauride fold-thrust belt in southern Turkey is flanked and overlain by Neogene sedimentary basins. To the south and on top of the high ranges, these basins are mainly marine, whereas previously poorly studied intra-montane basins dominated by continental deposits are exposed to the north. We have studied the stratigraphy and structure of these continental basins - the Alt?napa, Yalvaç and Ilg?n Basins. Their stratigraphy displays overall fining upward sequences of fluvio-lacustrine sediments, deposition of which interrupted by basin-wide unconformities; similar hiatuses seems to exist in each basin. The most prominent unconformity surface occurred during the Middle Miocene and corresponds to the timing of volcanic activity in the region. 40Ar/39Ar dating of the volcaniclastic samples from the Alt?napa and Ilg?n basins yielded 11.8-11.6 Ma ages. The main basin forming regional deformation phase was extensional and occurred during the Middle Miocene. The extension directions obtained from paleostress inversion techniques indicate multidirectional extension under vertical uniaxial stress which are compatible with the recent seismic activity and available focal mechanism solutions. The main basin-bounding faults, however, are constrained mainly N-S to NW-SE implying that they are reactivated structures. The Middle Miocene and onwards extensional history of these basins occurs behind and atop a thrust front along the Cyprus arc, extending towards the Antalya nappes and Aksu thrust in the heart of the Isparta angle. The synchrounous, curved pairs of thrust fronts associated with subduction and overriding plate extension suggests that the Cyprus subduction zone has been retreating relative to central Anatolia since, at least, the Middle Miocene time. In addition to extensional history of the region, these continental basins contain evidence for the post-Late Miocene differential uplift of the Taurides in southern Anatolia. All of these continental basins were above sea level during the Middle and Late Miocene and are now found at an elevation of 1 km. On the other hand, the upper Miocene marine deposits just south of the study area currently are at an elevation of ~2 km, and have therefore been uplifted at least 1 km more than the continental basins to the north. We conclude that the current high elevation of the Taurides is synchronous with, and at least in part related to late Neogene extension and vertical differential uplift, likely related to the dynamics of the Cyprian subduction zone.

Koç, Ayten; Kaymakci, Nuretdin; van Hinsbergen, Douwe J. J.; Kuiper, Klaudia F.; Vissers, Reinoud L. M.

2014-05-01

266

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

NASA Astrophysics Data System (ADS)

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 Gölü 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.

Fernández-Blanco, David; Bertotti, Giovanni

2010-05-01

267

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

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

268

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

PubMed

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

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

2010-07-01

269

?18O and Marion Plateau backstripping: Combining two approaches to constrain late middle Miocene eustatic amplitude  

NASA Astrophysics Data System (ADS)

?18Obenthic values from Leg 194 Ocean Drilling Program Sites 1192 and 1195 (drilled on the Marion Plateau) were combined with deep-sea values to reconstruct the magnitude range of the late middle Miocene sea-level fall (13.6 11.4 Ma). In parallel, an estimate for the late middle Miocene sea-level fall was calculated from the stratigraphic relationship identified during Leg 194 and the structural relief of carbonate platforms that form the Marion Plateau. Corrections for thermal subsidence induced by Late Cretaceous rifting, flexural sediment loading, and sediment compaction were taken into account. The response of the lithosphere to sediment loading was considered for a range of effective elastic thicknesses (10 < Te < 40 km). By overlapping the sea-level range of both the deep-sea isotopes and the results from the backstripping analysis, we demonstrate that the amplitude of the late middle Miocene sea-level fall was 45 68 m (56.5 ± 11.5 m). Including an estimate for sea-level variation using the ?18Obenthic results from the subtropical Marion Plateau, the range of sea-level fall is tightly constrained between 45 and 55 m (50.0 ± 5.0 m). This result is the first precise quantitative estimate for the amplitude of the late middle Miocene eustatic fall that sidesteps the errors inherent in using benthic foraminifera assemblages to predict paleo water depth. The estimate also includes an error analysis for the flexural response of the lithosphere to both water and sediment loads. Our result implies that the extent of ice buildup in the Miocene was larger than previously estimated, and conversely that the amount of cooling associated with this event was less important.

John, Cédric M.; Karner, Garry D.; Mutti, Maria

2004-09-01

270

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

USGS Publications Warehouse

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.

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

2008-01-01

271

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

USGS Publications Warehouse

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.

Abbott, W. H.

1978-01-01

272

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

273

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

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.

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

2000-01-01

274

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

NASA Astrophysics Data System (ADS)

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.

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

2000-01-01

275

Late Miocene - Pliocene Evolution of the Pacific Warm Pool and Cold Tongue: Implications for El Niño  

NASA Astrophysics Data System (ADS)

The Western Pacific Warm Pool of the tropical Pacific Ocean retains the largest and warmest sea surface water body on Earth, while the eastern equatorial Pacific is characterized by strong upwelling of cold, nutrient-rich deep waters, termed the Pacific cold tongue. Evolution of the Pacific warm pool and cold tongue are important because they control the circum-Pacific climate and impact the globe via El Niño - Southern Oscillation (ENSO) teleconnections. Sea surface temperature (SST) reconstructions using a single site from the warm pool (ODP 806) and two sites from the cold tongue (ODP 846, 847) suggest that the temperature of the warm pool was "stable" throughout the Plio-Pleistocene, whereas the cold tongue was much warmer in the Pliocene and subsequently cooled. The absence of an east-west Pacific temperature gradient during the early Pliocene is the basis for the "permanent El Niño" hypothesis. However, annually-resolved fossil coral and evaporite records found 3-7 years climate variability during the Pliocene warm period and late Miocene, challenging a "permanent" or invariant climate state. Here we present a multi-proxy (TEX86, UK37, Mg/Ca), multi-site reconstruction of the late Miocene - Pliocene (ca. 12 Ma - 3 Ma) SST in the Pacific warm pool (ODP 806, ODP 769 in the Sulu Sea, ODP 1143 in the South China Sea) and the cold tongue (ODP 850, 849, 846). Our results show that the cold tongue was even warmer in the late Miocene than the Pliocene, and that the warm pool cooled 2-3°C from the late Miocene into the Pliocene - in contrast to the invariant character previously assumed. Temperature comparison between different sites suggests that the warm pool may have expanded in size in the late Miocene. Although eastern and western ends of the tropical Pacific were warmer, a persistent, but low east-west temperature gradient (~3°C) is apparent. This agrees with recent studies which have shown ENSO-related frequency of climate change in the late Miocene and early Pliocene.

Zhang, Y.; Pagani, M.

2011-12-01

276

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

NASA Astrophysics Data System (ADS)

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 ?11B-pCO2 records, both new published, to evaluate the role of CO2 in modulating Miocene climate. Calculated ?11B-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 ?11B based CO2 reconstruction over these long timescales (e.g. variable ?11B 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

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

2013-12-01

277

The antiquity of riverine adaptations in Iniidae (Cetacea, Odontoceti) documented by a humerus from the late Miocene of the Ituzaingó Formation, Argentina.  

PubMed

"River dolphins" are a paraphyletic group of toothed whales (Odontoceti) that represent independent secondary invasions of freshwater habitats. Different "river dolphin" lineages display suites of convergent morphological specializations that commonly reflect adaptations to riverine and freshwater environments, such as longirostry, reduced orbits, and wide, paddle-like flippers. One lineage, the Iniidae, is presently endemic to South America, and includes several extinct Neogene taxa along with their sole extant genus, Inia (the Amazon River dolphin). We report here a humerus recovered from the late Miocene deposits of the Ituzaingó Formation in the Paraná Basin of Argentina. The specimen exhibits diagnostic features of the family Iniidae, including a scapular-sternal joint of the humerus, which is a unique anatomical connection among mammals. This joint permits enhanced parasagittal adduction of the flipper as a control surface, relative to other odontocetes, providing Inia with a high degree of maneuverability in its structurally complex and heterogenous riverine habitat. This unique anatomical connection, here documented from the late Miocene (?9 million years-6.5 million years old), not only provides the oldest diagnostic record for Iniidae, but it also indicates a similar habitat use for this lineage, a finding coincident with the current paleoenvironmental interpretation for the Ituzaingó Formation. PMID:24585575

Gutstein, Carolina Simon; Cozzuol, Mario Alberto; Pyenson, Nicholas D

2014-06-01

278

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

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.

Critelli, S. [Consiglio Nazionale delle Ricerche, Roges di Rende (Italy). Istituto di Ricerca per la Protezione Idrogeologica nell`Italia Meridionale ed Insulare; Rumelhart, P.E.; Ingersoll, R.V. [Univ. of California, Los Angeles, CA (United States). Dept. of Earth and Space Sciences

1995-10-02

279

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)

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).

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

2013-05-01

280

Ozakia, a new genus of winged fruit shared between the Miocene of Japan and western North America.  

PubMed

A new genus is recognized based on winged fruits with a single species shared between the Miocene of southwestern Honshu, Japan, and the Miocene of Oregon and Idaho, USA. Calyces of Ozakia emryi gen. et sp. n. were formerly attributed to Heptacodium (Caprifoliaceae) and Amelanchier (Rosaceae); however, newly recovered specimens reveal additional characters that contradict these assignments. The pedicellate fruits are obovate, tapering basally and truncate apically, with about 10 longitudinal ribs, a prominent epigynous synsepalous calyx of five lobes, each with a midvein and a pair of weaker, ascending intramarginal primary veins. The single style has a capitate stigma. Ozakia is considered to represent an extinct eudicot genus, the familial affinities of which remain uncertain. The eastern Asian-western North American disjunction of Ozakia occurrences suggests that this plant traversed the Beringia land bridge during or prior to the Middle Miocene. Relatively few extinct angiosperm genera are known as late as the Miocene. PMID:24306324

Manchester, Steven R; Uemura, Kazuhiko

2014-03-01

281

A new species of long-necked turtle (Pleurodira: Chelidae: Chelodina) from the late Miocene Alcoota Local Fauna, Northern Territory, Australia  

PubMed Central

The new species Chelodina (Chelodina) murrayi is described from the late Miocene Alcoota Local Fauna of central Australia, in the Northern Territory. The new species is based on shell fragments and can be diagnosed by a ventrally reflexed anterior margin of the plastron, a ventrally narrowed cervical scute and strongly dorsally curved margins of the carapace extending from approximately peripheral two to peripheral nine or ten as well as by a unique combination of characters. Within Chelodina the new species is part of the nominal subgenus and within that subgenus it is most closely related to the Chelodina (Chelodina) novaeguineae species group. This is not only the oldest record but also the most southerly occurrence of this species group.

2013-01-01

282

Miocene-Pleistocene volcanism and tectonics in southern Korea and their relationship to the opening of the Japan Sea  

Microsoft Academic Search

Miocene-Pleistocene volcanism and tectonics in southern Korea are discussed. The Miocene volcanism and related tectonics are represented by the Eoil Orogeny, which occurred in the Yangnam and Pohang basins in the southeastern corner of the Korean Peninsula. The Yangnam and Pohang basins represent the uplifted central part of the Pohang-Ulsan Graben which was rifted between the Proto-Korean Peninsula and Paleo-Ulleung

Sun Yoon

1997-01-01

283

The species richness of Miocene browsers, and implications for habitat type and primary productivity in the North American grassland biome  

Microsoft Academic Search

Abstract We have documented elsewhere, and briefly reviewed here, the anomalously high species richness of browsing ungulates (hoofed mammals),in the mid Miocene (f18–12 Ma) woodland,savanna habitats of North America. In the mid Miocene these habitats supported substantially more brachydont,(browsing) species than do any present-day savanna,habitats. We present some preliminary data to show,that such species-rich browser communities,are not observed after the

Christine M. Janis; John Damuthsupbsu; Jessica M. Theodor

2004-01-01

284

Planktonic foraminiferal biostratigraphy of the Miocene sequence in the area between Wadi El-Tayiba and Wadi Sidri, west central Sinai, Egypt  

NASA Astrophysics Data System (ADS)

The present work deals with the study of lithostratigraphy and the planktonic foraminiferal biostratigraphy of the Early-Middle Miocene sequence in six measured stratigraphical surface sections in west central Sinai. They are namely, from north to south: Wadi El-Tayiba, Gabal Sarbut El-Gamal, Wadi Nukhul, Wadi Baba, Gabal Abu Alaqa and Wadi Sidri. The Miocene sequence, exposed in the study area, is represented lithostratigraphically by four rock units, arranged from base to top as follows: the Nukhul and Rudeis Formations (Early Miocene), the Sarbut El-Gamal Formation and the Hammam Faraun Member of the Belayim Formation (Middle Miocene). The planktonic foraminiferal biostratigraphical studies led to the recognition of 51 planktonic foraminiferal species. They are illustrated with the scanning electron microscope. Five planktonic foraminiferal biozones and one large benthonic foraminiferal zone have been recognised. They are arranged from top to bottom as follows: Orbulina suturalis/Globorotalia siakensis Zone (Middle Miocene); Borelis melo Zone (larger foraminiferal zone) (Middle Miocene); Globigerinoides sicanus Zone (Early Miocene); Globigerinoides trilobus Zone (Early Miocene); Globigerinoides altiaperturus-Catapsydrax dissimifis Zone (Early Miocene); Globigerinoides primordius Zone (Early Miocene). Correlation of these biozones with others from Egypt and the world is also attempted.

Phillip, G.; Imam, M. M.; Abdel Gawad, G. I.

1997-10-01

285

Ionic Liquid-Based One-Step Micellar Extraction of Multiclass Polar Compounds from Hawthorn Fruits by Ultrahigh-Performance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Tandem Mass Spectrometry.  

PubMed

An ionic liquid (IL)-based one-step micellar extraction procedure was developed for the extraction of multiclass polar analytes (protocatechuic acid, chlorogenic acid, epicatechin, hyperoside, isoquercitrin, quercetin) from hawthorn fruits and their determination using ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF/MS). Compared to conventional organic solvent extractions, this newly proposed method was much easier, more sensitive, environmentally friendly, and effective as well. Several important parameters influencing the micellar extraction efficiency are discussed, such as selection of ILs, surfactant concentration, and extraction time. Under the optimal conditions, good linearity was achieved for each analyte with correlation coefficients (r(2)) ranging from 0.9934 to 0.9999, and the recovery values ranged from 89.3 to 106% with relative standard deviations lower than 5.5%. Results suggest that the IL-based one-step micellar extraction could be an alternative and promising means in future food analysis. PMID:24845828

Hu, Shuai-Shuai; Yi, Ling; Li, Xing-Ying; Cao, Jun; Ye, Li-Hong; Cao, Wan; Da, Jian-Hua; Dai, Han-Bin; Liu, Xiao-Juan

2014-06-11

286

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

SciTech Connect

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.

MacFadden, B.J.; Bryant, J.D.; Mueller, P.A. (Univ. of Florida, Gainesville (USA))

1991-03-01

287

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

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

288

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

NASA Astrophysics Data System (ADS)

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).

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

2013-12-01

289

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

PubMed

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

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

2011-01-01

290

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

NASA Astrophysics Data System (ADS)

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.

Combellas Bigott, Ricardo Ignacio

291

REE geochemistry of late Miocene lavas from Pioneertown, Fry Mountain and Ruby Mountain, California  

SciTech Connect

A series of flows, dikes and cinder cones of alkaline and subalkaline basalts erupted in late Miocene time along the northeastern flank of the San Bernardino Mountains and in contiguous parts of the Mojave Desert. Previous studies of lavas from the region yielded K-Ar ages of 6 to 9 Ma, and reported that lavas from the Ruby Mountain locality often contain ultramafic inclusions of probable mantle origin. This study (1) characterizes the rare earth element (REE; light = LREE; heavy = HREE) and trace element compositions of the young lavas from this region, (2) discusses the relationship of the Pioneertown lavas with the hot-spring ( ) deposits stratigraphically beneath the lava flows, (3) speculates on the possible volcanic conduit for the Pioneertown lavas, and (4) discusses the petrogenesis of these late Miocene lavas.

Mehegan, J.M.; Thorpe, R. (California State Univ., San Bernardino, CA (United States))

1993-04-01

292

The Middle Miocene climate as modeled in an atmosphere-ocean-biosphere model  

NASA Astrophysics Data System (ADS)

We present the first simulations for the Middle Miocene using a fully coupled atmosphere-ocean-biosphere model. The Middle Miocene topography, which alters both large-scale ocean and atmospheric circulation, causes a global warming of 0.7 K compared to a modern control climate. Compared to temperature proxies this warming is too small. Applying higher CO2 concentrations of 480 and 720 ppm, we are able to simulate a global warming of 2.8 K and 4.9 K compared to present-day, which is in line with proxy records. Still, a flatter equator-to-pole temperature gradient, as it is suggested by marine and terrestrial proxies, cannot be realized. One reason is that atmospheric and oceanic heat transport compensate leaving the total poleward heat transport nearly unchanged. In our contribution we will show the mechanisms that are responsible for these compensating effects in the atmosphere-ocean system.

Krapp, M.; Jungclaus, J. H.

2011-12-01

293

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

294

Slowing extrusion tectonics: Lowered estimate of post-Early Miocene slip rate for the Altyn Tagh fault  

USGS Publications Warehouse

Determination of long-term slip rate for the Altyn Tagh fault is essential for testing whether Asian tectonics is dominated by lateral extrusion or distributed crustal shortening. Previous slip-history studies focused on either Quaternary slip-rate measurements or pre-Early Miocene total-offset estimates and do not allow a clear distinction between rates based on the two. The magmatic and metamorphic history revealed by SHRIMP zircon dating of clasts from Miocene conglomerate in the Xorkol basin north of the Altyn Tagh fault strikingly matches that of basement in the southern Qilian Shan and northern Qaidam regions south of the fault. This match requires that the post-Early Miocene long-term slip rate along the Altyn Tagh fault cannot exceed 10 mm/year, supporting the hypothesis of distributed crustal thickening for post-Early Miocene times. This low long-term slip rate and recently documented large pre-Early Miocene cumulative offset across the fault support a two-stage evolution, wherein Asian tectonics was dominated by lateral extrusion before the end of Early Miocene, and since then has been dominated by distributed crustal thickening and rapid plateau uplift. ?? 2003 Elsevier B.V. All rights reserved.

Yue, Y.; Ritts, B. D.; Graham, S. A.; Wooden, J. L.; Gehrels, G. E.; Zhang, Z.

2004-01-01

295

Oxygen-related facies in Lake Pannon deposits (Upper Miocene) at Budapest-Köbánya  

Microsoft Academic Search

Oxygen availability is considered to have been a major factor in shaping the sedimentary facies and biofacies of a Late Miocene (8–8.5 Ma old) Lake Pannon sequence studied in the Kozma-street outcrop in Budapest-Köbánya. The sequence contains blue clays deposited in low-oxygen conditions between the storm and the fair-weather wave bases and thin intercalations of laminated fine sand interpreted as

Imre Magyar; Pál Mihály Müller; Miklós Lantos

2006-01-01

296

The muddy bottom of Lake Pannon – a challenge for dreissenid settlement (Late Miocene; Bivalvia)  

Microsoft Academic Search

The Late Miocene dreissenids of Lake Pannon – a long existing eastern-central European lake – bear witness to two very different modes of life, which allowed these bivalves to successfully settle in what appears to be an inhospitable environment. One guild is restricted to the genera MytilopsisConrad, 1858 and SinucongeriaLõrenthey, 1894. These representatives are extreme r-strategists which tend to produce

Mathias Harzhauser; Oleg Mandic

2004-01-01

297

First hominoid from the Miocene of Ethiopia and the evolution of the catarrhine elbow  

Microsoft Academic Search

The first known fossil ape from the early-middle Miocene of Fejej, Ethiopia, is described here. The specimen, FJ-18SB-68, is a partial ulna from a locality dated by 40Ar\\/39Ar and paleomagnetic methods to a minimum age of 16.18 MYA. Compared to a variety of extant and fossil ulnae, FJ-18SB-68 is most similar to Turkanapithecus, Proconsul, and Pliopithecus, and appears to have

Brian G. Richmond; John G. Fleagle; John Kappelman; Carl C. Swisher

1998-01-01

298

A new chronology for the middle to late Miocene continental record in Spain  

Microsoft Academic Search

The first detailed chronology for the middle to late Miocene continental record in Spain is presented, based on high-resolution magnetostratigraphic data of mammal-bearing sections which were studied in several basins (Calatayud-Daroca, Teruel, Vallès-Penedès, Duero and Júcar-Cabriel). Our results indicate that these sections compose an almost complete magnetostratigraphic succession from the lower Aragonian (MN4) to the middle Turolian (MN12). Seven successive

W. Krijgsman; M. Garcés; C. G. Langereis; R. Daams; J. van Dam; A. J. van der Meulen; J. Agustí; L. Cabrera

1996-01-01

299

Regional depositional history of the Miocene-Pleistocene Louisiana Slope, Green Canyon and Mississippi Canyon  

Microsoft Academic Search

A regional sequence-stratigraphic analysis was recently completed for the Tertiary slope sediments in Green Canyon, Ewing Bank, and Mississippi Canyon to provide a chronostratigraphic framework for basin reconstructions and predict lithofacies distributions of reservoir and seal rocks. Sixteen third-order sequences of lowstand deep-water deposits were interpreted for the middle Miocene-Pleistocene section. Thirty regional lithofacies maps were made of predominantly lowstand

D. L. Risch; A. N. Chowdhury; A. E. Hannan

1994-01-01

300

Eustatic implications of late Miocene depositional sequences in the Melilla Basin, northeastern Morocco  

Microsoft Academic Search

The age (?5.78 Ma or lower chron C3r) of the major drawdown of the Paleo-Mediterranean Sea during the Messinian Salinity Crisis has been established by combining results from stratigraphy, paleontology, magnetostratigraphy, and argon dating for a late Miocene sedimentary succession in the Melilla Basin, NE Morocco. This event is inferred from a marine-to-continental series of carbonate and siliciclastic rocks that

Kevin J. Cunningham; Richard H. Benson; Kruna Rakic-El Bied; Larry W. McKenna

1997-01-01

301

Searching for the Africa–Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)  

Microsoft Academic Search

We present new results from the MARADJA'03 cruise depicting the geological structures offshore central and western Algeria. Using swath bathymetry and seismic reflection data, we map and discuss the offshore limits of the Internal Zones corresponding to relics of the AlKaPeCa domain that drifted and collided the African plate during the Miocene. We identify large reverse faults and folds that

Anne Domzig; Karim Yelles; Charlotte Le Roy; Jacques Déverchère; Jean-Pierre Bouillin; Rabah Bracène; Bernard Mercier de Lépinay; Pascal Le Roy; Eric Calais; Abdelaziz Kherroubi; Virginie Gaullier; Bruno Savoye; Henri Pauc

2006-01-01

302

A molecular stable carbon isotope study of organic matter in immature Miocene Monterey sediments, Pismo basin  

SciTech Connect

The 300 m section of the Miocene Monterey Formation outcropping at Shell Beach 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 Monterey Formation by comparing the Shell Beach (SB) profile with the Naples Beach (NB) section in the Santa Barbara-Ventura basin. 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{sub 17}-C{sub 31}), lycopane, and 17{beta}, 21{beta}(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{sub 17}-C{sub 31} n-alkanes. regular 5{alpha}- and 5{beta}-steranes, dinosteranes, and (22R)-17{beta},21{beta}(H)-pentakishomohopane. Steranes have similar carbon isotopic compositions (-25 to -27{per_thousand}) 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. 1-49{per_thousand} 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. 64 refs., 14 figs., 6 tabs.

Schouten, S.; Rijpstra, I.C.; De Leeuw, J.W. [Netherlands Institute for Sea Research, Texel (Netherlands)] [and others] [Netherlands Institute for Sea Research, Texel (Netherlands); and others

1997-05-01

303

The Lower Miocene siliceous zone: a marker in the palaeogeographic evolution of the northern Apennines  

Microsoft Academic Search

The occurrence of coeval silica-rich and volcaniclastic layers within diverse tectonic domains of the northern Apennines provides the opportunity to discuss and redefine the old term “lithozone” in a modern light, showing its interest when used for stratigraphic correlation of genetically related deposits.Silica-rich horizons (bedded cherts and nodules) have been reported in the Lower Miocene strata of circum-Mediterranean countries as

A. Amorosi; F. Ricci Lucchi; F. Tateo

1995-01-01

304

Middle Miocene ice sheet expansion in the Arctic: Views from the Barents Sea  

Microsoft Academic Search

Revised core data from Ocean Drilling Program (ODP Leg 151, Hole 909C) and preglacial paleorelief and bathymetric reconstructions in the Barents Sea and the Arctic gateway region indicate that large-scale glaciations were already developed in the northern Barents Sea during the Middle Miocene Climate Transition (MMCT), ?15–14 million years ago. Our findings show that subsequent to an ice-free period during

Jochen Knies; Carmen Gaina

2008-01-01

305

Middle Miocene ice sheet expansion in the Arctic: Views from the Barents Sea  

Microsoft Academic Search

Revised core data from Ocean Drilling Program (ODP Leg 151, Hole 909C) and preglacial paleorelief and bathymetric reconstructions in the Barents Sea and the Arctic gateway region indicate that large-scale glaciations were already developed in the northern Barents Sea during the Middle Miocene Climate Transition (MMCT), ~15-14 million years ago. Our findings show that subsequent to an ice-free period during

Jochen Knies; Carmen Gaina

2008-01-01

306

Paleomagnetism of miocene east african rift sediments and the calibration of the geomagnetic reversal time scale  

Microsoft Academic Search

Paleomagnetic stratigraphy and K-Ar age determinations are reported for the type section of the middle Miocene Ngorora Formation, found in the Kenya rift valley. The magnetostratigraphy is well correlated to the geomagnetic reversal time scale (GRTS) and spans from the lower part of Chron C5 (9) to Chron C5AB-r (14). K-Ar dates were determined for euhedral sanidines, hand-picked from sevel

L. Tauxe; H. Staudigel; M. Monaghan; R. Drake; G. Curtis

1985-01-01

307

A Miocene Forest Assemblage in the Columbia River Basalts of Washington State, USA  

NSDL National Science Digital Library

This report describes a fossil locality in Washington State in which fossil trees are preserved standing upright in a Miocene basalt flow. Topics include the Columbia River Flood Basalts (one of which inundated the trees), a description of the fossil site, the ages of the basalt and the underlying clay, analyses of the fossil wood to determine tree species, and a discussion of the depositional environment in which the trees are preserved.

308

Miocene to recent eolian dust record from the Southwest Pacific Ocean at 40° S latitude  

Microsoft Academic Search

A 14-meter long pelagic clay core recovered at Marlin Rise (40°00.531?S, 154°2.601?W; 4775 m water depth) in the Southwest Pacific Basin contains a record of eolian dust deposited since the early Miocene. Downcore analysis of detrital minerals reveals a dominantly eolian signature with relatively constant proportions of quartz, feldspar and illite and trace amounts of chlorite, kaolinite and smectite, consistent with

Andrea M. Stancin; James D. Gleason; Steven A. Hovan; David K. Rea; Robert M. Owen; Theodore C. Moore Jr.; Chris M. Hall; Joel D. Blum

2008-01-01

309

DNA Sequences from a Fossil Termite in Oligo-Miocene Amber and Their Phylogenetic Implications  

Microsoft Academic Search

DNA was extracted from the fossil termite Mastotermes electrodominicus preserved in Oligo-Miocene amber (25 million to 30 million years old). Fragments of mitochondrial [16S ribosomal DNA (rDNA)] and nuclear (18S rDNA) genes were amplified by polymerase chain reaction. Phylogenetic analysis of fossil and extant 18S rDNA confirmed morphological cladistic analyses of living dictyopterans (termites, cockroaches, and mantids). The fossil termite

Rob Desalle; John Gatesy; Ward Wheeler; David Grimaldi

1992-01-01

310

Geology and geochronology of the middle Miocene Kipsaramon site complex, Muruyur Beds, Tugen Hills, Kenya  

Microsoft Academic Search

The Muruyur Beds are a substantial sedimentary deposit within a middle Miocene sequence of mafic volcanic flows associated with early stages of rifting in the central Kenyan Rift Valley. They are best represented in the Muruyur region, near Bartabwa, north of Kipsaramon, where dates range from 16·0 to 13·4Ma. At Kipsaramon, located about 10km south of Muruyur along the crest

Anna K. Behrensmeyer; Alan L. Deino; Andrew Hill; John D. Kingston; Jeffrey J. Saunders

2002-01-01

311

Oligocene and Early Miocene coral faunas from Iran: palaeoecology and palaeobiogeography  

Microsoft Academic Search

Oligocene and Early Miocene coral assemblages from three sections of central Iran are investigated with respect to their\\u000a palaeoecological and palaeobiogeographic implications. These corals are compared with faunas from the Mediterranean Tethys\\u000a and the Indopacific. Associated larger foraminifers are used for biostratigraphy and to support the palaeoecological interpretation.\\u000a The studied sections are situated in the foreland basins of the Iranian

F. Schuster; U. Wielandt

1999-01-01

312

Depositional environment and sequence stratigraphy of the Oligo-Miocene Asmari Formation in SW Iran  

Microsoft Academic Search

The Asmari Formation, a thick carbonate succession of the Oligo-Miocene in Zagros Mountains (southwest Iran), has been studied\\u000a to determine its microfacies, paleoenvironments and sedimentary sequences. Detailed petrographic analysis of the deposits\\u000a led to the recognition of 10 microfacies types. In addition, five major depositional environments were identified in the Asmari\\u000a Formation. These include tidal flat, shelf lagoon, shoal, slope

Hossein Vaziri-Moghaddam; Masoud Kimiagari; Azizolah Taheri

2006-01-01

313

40. MIOCENE-PLIOCENE SURFACE-WATER HYDROGRAPHY OF THE EASTERN EQUATORIAL ATLANTIC 1  

Microsoft Academic Search

Stable isotope analyses of four species of planktonic foraminifers and the benthic foraminifer, Cibicides wuellerstorfi, from Ocean Drilling Program Site 959 show that the Gulf of Guinea had a strong, shallow thermocline during the latest Miocene and early Pliocene prior to the first appearance of the Guinea Current at about 4.9 Ma. Gradients of ?18O between the surface-water species, Globigerinoides

Richard D. Norris

314

Oxygen isotopic constraints on the geneses of the Miocene Outer Zone granitoids in Japan  

Microsoft Academic Search

Miocene ilmenite-series granitoids of the Outer Zone of southwest Japan have been classified mineralogically into the southern S-type and the northern I-type. Oxygen isotopic ratios, ?18OSMOW, were determined on 45 representative samples from 17 granitic plutons. The results indicate that the Outer Zone granitoids have much higher ?18O values than magnetite-series granitoids of similar ages, confirming a contribution from crustal

Shunso Ishihara; Yukihiro Matsuhisa

1999-01-01

315

The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system  

Microsoft Academic Search

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 Solimões 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 9–6.5Ma. Additionally, we present results that demonstrate

Edgardo M. Latrubesse; Mario Cozzuol; Silane A. F. da Silva-Caminha; Catherine A. Rigsby; Maria Lucia Absy; Carlos Jaramillo

2010-01-01

316

Snake fangs from the Lower Miocene of Germany: evolutionary stability of perfect weapons  

Microsoft Academic Search

There is a general consensus that most of today’s nonvenomous snakes are descendants of venomous snakes that lost their venomous\\u000a capabilities secondarily. This implies that the evolutionary history of venomous snakes and their venom apparatus should be\\u000a older than the current evidence from the fossil record. We compared some of the oldest-known fossil snake fangs from the Lower\\u000a Miocene of

Ulrich Kuch; Johannes Müller; Clemens Mödden; Dietrich Mebs

2006-01-01

317

Levoglucosan and other cellulose markers in pyrolysates of Miocene lignites: geochemical and environmental implications  

Microsoft Academic Search

Using the pyrolysis-gas chromatography-mass spectrometry and off-line pyrolysis\\/silylation methods for lignites from three Miocene brown coal basins of Poland resulted in the characterization of many organic compounds, including dominant cellulose degradation products such as levoglucosan, 1,6-anhydro--D-glucofuranose, and 1,4:3,6-dianhydroglucopyranose. Levoglucosan is a general source-specific tracer for wood smoke in the atmosphere and recent sediments. The presence of unusually high levels of

Daniele Fabbri; Leszek Marynowski; Monika J. Fabianska; Micha? Zaton?; Bernd R. T. Simoneit

2008-01-01

318

Termination of the Arabian shelf sea: stacked cyclic sedimentary patterns and timing (Oligocene/Miocene, Oman)  

NASA Astrophysics Data System (ADS)

The collision of Africa and Eurasia during the Oligo-Miocene and the resultant closure of the marine passage between the eastern and western Tethys (Terminal Tethyan Event) had far-reaching consequences for the distribution of shallow water areas and the course of ocean currents. It was therefore one of the major events for the distribution and evolution of terrestrial, as well as marine faunas during the Cenozoic. The exact timing of the Terminal Tethyan Event is thus crucial for palaeobiogeographic questions. In this context, the emersion of the Arabian Shelf during the Early Miocene was an important step because of a drastic reduction of shallow-water areas. The collapse of the Arabian Shelf was initiated by the opening of the Gulf of Aden during the Oligocene. In the Janahbah region of southeastern Oman, Oligocene/Miocene limestones of the Shuwayr, Warak and Ghubbarrah formations are widely exposed. They were deposited on an extensive shallow carbonate platform that was part of the Arabian Shelf and located on the Gulf of Aden's northeastern rift shoulder. The uppermost part of the studied sedimentary succession developed immediately before the permanently subaerial exposure of the carbonate platform during the Early Miocene. Cyclic changes of intertidal and subtidal facies document a fluctuating relative sea level at different frequencies and a continuous decline of accommodation space. Single erosive surfaces with palaeokarst cavities and caliche crusts separate larger depositional cycles. These disconformities imply relatively long episodes of subaerial exposure and are interpreted to have been formed during lowstands of third-order sea-level cycles that denuded the platform. Taxonomic studies of the accompanying mollusc faunas and certain benthic foraminifers allow a correlation of the recognised subaerial disconformities with the Ru4/Ch1 to Ch4/Aq1 sequence boundaries of Hardenbol et al. (1998). This demonstrates that the termination of the Arabian shelf sea must be back-dated from the middle Burdigalian to the early Aquitanian.

Piller, W. E.; Reuter, M.; Harzhauser, M.; Kroh, A.

2009-04-01

319

Stable isotope composition of the Miocene Dinaride Lake System deduced from its endemic mollusc fauna  

Microsoft Academic Search

The aragonite shells of 55 mollusc specimens from the late Early and early Middle Miocene of two palaeolakes of the Dinaride\\u000a Lake System (DLS) are analysed for their ?18O and ?13C signatures. The data set has a bimodal distribution with a prominent peak between ?3 and ?4‰ for both isotopes and a second\\u000a much weaker peak at more depleted values of

Mathias Harzhauser; Oleg Mandic; Christine Latal; Andrea Kern

320

OLIGOCENE-MIOCENE PLANKTONIC FORAMINIFER BIOSTRATIGRAPHY, SITE 1148, NORTHERN SOUTH CHINA SEA1  

Microsoft Academic Search

Over 30 first and last occurrence (FO and LO, respectively) plank- tonic foraminifer datums were recognized from the Oligocene-Miocene section of Ocean Drilling Program (ODP) Site 1148. Most datum levels occur in similar order as, and are by correlation as probably synchro- nous with, their open-ocean records. Several datum levels represent lo- cal bioevents resulting from dissolution and Site 1148's

Qianyu Li; Zhimin Jian; Baohua Li

321

FOSSIL BLOOD DROPLETS IN MIOCENE DOMINICAN AMBER YIELD CLUES TO SPEED AND DIRECTION OF RESIN SECRETION  

Microsoft Academic Search

Two spiders (Filistatidae) in Miocene Dominican Republic amber, one newly identified and only the second known fossil of this family, have autospasized legs (detached at a predetermined locus of weakness when restrained by a non-self-induced source) at the patella-tibia joint. In both specimens, droplets of haemolymph (blood) are preserved exiting the patellae. The autospasized legs and the presence of haemolymph

DAVID PENNEY

2005-01-01

322

Late Miocene Pliocene intensification of the East Asian monsoon linked to Antarctic ice-sheet development  

NASA Astrophysics Data System (ADS)

Recent evidence indicates that an East Asian monsoon broadly similar to the present may have occurred in China as early as the late Oligocene or early Miocene, but its variability and possible driving forces prior to the Quaternary epoch remain poorly known, due to rare reconstructions of continuous long-term East Asian monsoon records extending to the earlier periods. Here we report Late MiocenePliocene records of magnetic property variations of an eolian red clay sequence on the eastern Chinese Loess Plateau, which is dated using magnetostratigraphy. The high-resolution magnetic records indicate a long-term increasing trend in the East Asian summer monsoon intensity from ca 8 to 2.6 Ma. This is supported by studies from central Chinese Loess Plateau and South China Sea. We further find that this Late MiocenePliocene monsoon intensification is broadly correlated the long-term increasing trend in the Southern Hemisphere ice volume, suggesting a possible linkage between them. Combing a numerical climate-model experiment that simulates the East Asian summer monsoonal responses to the idealized stepwise increases of ice sheets from East to West Antarctic, we suggested that the Southern Hemisphere ice-sheet development is a driver of this late MiocenePliocene intensification of the East Asian summer monsoon. The Southern Hemisphere ice-sheet development could have intensified the East Asian monsoon mainly via weakening the low pressures over Asia and enhancing the high pressures over western Pacific Ocean and Australia, implying sensitivity of the Asian monsoon to the interhemispheric temperature gradient modulated by Southern Hemisphere climate.

Ao, H.; An, Z.; Dekkers, M. J.; Liu, X.

2013-12-01

323

Fossils reveal an early Miocene presence of the aberrant gruiform Aves: Aptornithidae in New Zealand  

Microsoft Academic Search

A member of the New Zealand endemic family (Aves: Aptornithidae) is described from the Early Miocene St Bathans Fauna of Central\\u000a Otago, South Island, New Zealand. The new species, based on two thoracic vertebrae, is provisionally referred to the highly\\u000a distinctive Late Pleistocene–Holocene extinct genus Aptornis Mantell, 1848 (in Quart J Geol Soc Lond 4:225–238, 1848). It differs from both

Trevor H. WorthyAlan; Alan J. D. Tennyson; R. Paul Scofield

2011-01-01

324

Seismic-core integration of nearshore-onshore New Jersey early Miocene sequences  

Microsoft Academic Search

Lower Miocene sequences on the New Jersey margin provide excellent examples of prograding seismic clinoform geometry. Drilling both onshore and offshore has sampled updip and downdip locations 10's of km from intervening clinoform rollover points observed in high-resolution MCS profiles. This unsampled interval, where sequences are thickest and best developed, has been imaged using Lamont-Doherty's HiRes MCS seismic system aboard

D. H. Monteverde; K. G. Miller; J. V. Browning

2005-01-01

325

First joint record of Mesopithecus and cf. Macaca in the Miocene of Europe.  

PubMed

Cercopithecid fossil remains from the post-evaporitic Messinian (5.40-5.33 Ma, MN13, latest Turolian, latest Miocene) locality of Moncucco Torinese (Tertiary Piedmont Basin, NW Italy) are described. A talus is assigned to the fossil colobine Mesopithecus pentelicus, while a proximal fragment of ulna and a male lower canine are attributed to cf. Me. pentelicus. An isolated I(2) and M3 are assigned to the papionin cf. Macaca sp., and two cercopithecid phalanges are left unassigned even to the subfamily level. The record of Mesopithecus at Moncucco Torinese agrees well with the previously-known range of this species in Italy and elsewhere in Europe, whereas that of cf. Macaca constitutes only the second occurrence of macaques in the Miocene of Eurasia. Although the co-occurrence of these two genera in a single locality had been previously reported in the Pliocene, this is the first instance in which macaques are associated with the Late Miocene M. pentelicus instead of Mesopithecus monspessulanus. The record of cf. Macaca and Mesopithecus-and especially the latter's talar morphology, similar to that of extant arboreal colobines-fits well with paleoenvironmental reconstructions of Moncucco Torinese based on the associated fauna, which indicate a humid and densely-forested environment, probably with more open and drier habitats nearby. From a paleobiogeographic viewpoint, the record of Macaca at Moncucco Torinese, together with the previously reported occurrence at Almenara-Casablanca M (Spain), supports the contention that macaques dispersed from Africa into Europe during the latest Miocene (ca. 5.9-5.3 Ma) at the same time as the sea level drop associated with the Messinian Salinity Crisis. PMID:24342451

Alba, David M; Delson, Eric; Carnevale, Giorgio; Colombero, Simone; Delfino, Massimo; Giuntelli, Piero; Pavia, Marco; Pavia, Giulio

2014-02-01

326

Palynostratigraphy, palaeoclimates and palaeodepositional environments of the Miocene aged Agbada Formation in the Niger Delta, Nigeria  

NASA Astrophysics Data System (ADS)

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.

Bankole, Samson I.; Schrank, Eckart; Osterloff, Peter L.

2014-07-01

327

Middle Miocene environmental and climatic evolution at the Wilkes Land margin, East Antarctica  

NASA Astrophysics Data System (ADS)

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 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.

Sangiorgi, F.; Passchier, S.; Salzmann, U.; Schouten, S.; Pross, J.; Bijl, P.; Tauxe, L.; Bendle, J. A.; Escutia, C.; Brinkhuis, H.

2012-12-01

328

Middle Miocene marine and continental climate and environments at the Wilkes Land margin, Antarctica (IODP 318)  

NASA Astrophysics Data System (ADS)

Integrated Ocean Drilling Program (IODP) Expedition 318 accomplished successful drilling of the Wilkes Land margin (East Antarctica) in early 2010. Understanding the development and the dynamics of the cryosphere during the Cenozoic and obtaining high-resolution records of climate variability during the Neogene and the Quaternary were among the main targets. Samples from Site U1356 Hole A, between ~400 (across unconformity U5) and ~100 mbsf are analysed for dinoflagellate assemblages, pollen and spores, TEX86 and MBT in order to unravel marine and terrestrial climate variability during the early to middle Miocene. Results show that dinoflagellate assemblages, dominated by autotrophic species, are indicative of warm ice-free surface waters during the Middle Miocene Climatic Optimum (MMCO). TEX86-derived Sea Surface Temperatures (SSTs) confirm this interpretation. Continental temperatures based on pollen and Mean Annual Temperatures (MATs) as derived from MBT organic proxy indicate a vegetated Antarctic margin with temperate conditions. A clear climate deterioration occurs during the Mid Miocene Climate Transition (MMCT), when dinocyst and pollen assemblages indicate (year-round) sea-ice development and ice-sheets advance, respectively. Notably, SSTs and MATs markedly decrease.

Sangiorgi, F.; Schouten, S.; Bendle, J. A.; Salzmann, U.; Brinkhuis, H.; Escutia, C.; IODP Expedition 318 Science Party

2011-12-01

329

Oligocene and Early Miocene coral faunas from Iran: palaeoecology and palaeobiogeography  

NASA Astrophysics Data System (ADS)

Oligocene and Early Miocene coral assemblages from three sections of central Iran are investigated with respect to their palaeoecological and palaeobiogeographic implications. These corals are compared with faunas from the Mediterranean Tethys and the Indopacific. Associated larger foraminifers are used for biostratigraphy and to support the palaeoecological interpretation. The studied sections are situated in the foreland basins of the Iranian Plate which is structured into a fore-arc and a back-arc basin separated by a volcanic arc. The coral assemblages from Abadeh indicate a shallowing-upward trend. Infrequently distributed solitary corals at the base of the section indicate a turbid environment. Above, a distinct horizon characterised by a Leptoseris-Stylophora assemblage associated with lepidocyclinids and planktonic foraminifers is interpreted as maximum flooding surface. Small patch reefs with a Porites-Faviidae assemblage are a common feature of Late Oligocene to Early Miocene coral occurrences and indicate water depths of less than 20m. The diversity of the coral faunas shows marked differences. Oligocene corals from the Esfahan-Sirjan fore-arc basin comprise more than 45 species of 32 genera and occur in a wide range of environments. Early Miocene corals from the Qom back-arc basin are less frequent, show a lower diversity (13 genera with 15 species) and occur in single horizons or small patch reefs.

Schuster, F.; Wielandt, U.

330

Molluscan fauna from the Miocene sediments of Kachchh, Gujarat, India — Part 3. Gastropods  

NASA Astrophysics Data System (ADS)

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.

Kulkarni, Kantimati G.; Kapoor, Satarupa Bhattacharjee; Borkar, Vidyadhar D.

2010-06-01

331

Miocene honey bees from the Randeck Maar of southwestern Germany (Hymenoptera, Apidae)  

PubMed Central

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.

Kotthoff, Ulrich; Wappler, Torsten; Engel, Michael S.

2011-01-01

332

Petroleum potential of the frontal zone of the Miocene thrust belt of southeast Turkey  

SciTech Connect

The area of study lies directly south of the main front of the Miocene thrust belt and is crossed by a series of anticlinal structures of Miocene age which trend northwest-southeast. Many of the anticlinal structures are associated with one or two major thrust faults that border the anticlinal structures. In addition to the compressional features, the western part of the study area shows pre-, syn-, and post-Maastrichtian-Campanian deposition normal faulting. The postcompressional faults are probably relaxation features. Therefore, the structural development of the region has resulted in three superimposed structural trends in the study area. The local stratigraphic sequence ranges from the Paleozoic through the Miocene with some localized Quaternary basalts and alluvial deposits. The primary petroleum potential of the area and the emphasis of this paper is the Upper Cretaceous Maastrichtian-Campanian sequences, including the Beloka, Kiradag, Garzan, and lower Germav/Sinian formations. Additionally the Mardin formation of Cenomanian-Turonian age is an oil and gas-producing horizon. This paper presents the regional structural development, gross stratigraphy of the Maastrichtian-Campanian, and a specific 2-D seismic interpretation project in the area, illustrating these aspects of geology as well as citing specific examples of prospective structures.

Perincek, D.; Davis, C.S. (Turkish Oil Corp., Ankara)

1988-08-01

333

Location and migration of Miocene-Quaternary volcanic arcs in the SW Pacific region  

NASA Astrophysics Data System (ADS)

We report new Ar-Ar and U-Pb ages from ten rocks in the SW Pacific region. Our results (1) establish a northward Late Miocene Australian plate movement rate of 57 mm/a for the Lord Howe hotspot chain; (2) reinforce the previously established widespread nature of Early Miocene subduction-related volcanism in onland and nearshore northern New Zealand; (3) indicate that leucotonalite xenoliths from Raoul Island are the products of Quaternary Kermadec arc magmatism rather than being Cretaceous-Pliocene basement. A synthesis of available SW Pacific data emphasises that while there is a reasonably complete record of subduction-related volcanism from at least 23 Ma to the present day, the process of back-arc basin formation is highly episodic and asymmetric. Subduction-related arcs stabilised along the Taupo-Kermadec-Tonga arc from 2 Ma to the present, along the Taranaki-Colville-Lau trend from 17-6 Ma and along the Three Kings Ridge-Northland Plateau-Northland trend from 23-18 Ma. South of latitude 25°S, back-arc basin opening occurred during the Early Miocene and Quaternary arc volcanic episodes, but does not appear to have accompanied the 17-5 Ma volcanism.

Mortimer, N.; Gans, P. B.; Palin, J. M.; Meffre, S.; Herzer, R. H.; Skinner, D. N. B.

2010-02-01

334

A simple petrogenetic model for the formation of Miocene Low-?18O rhyolites of the Yellowstone Hotspot track, USA  

NASA Astrophysics Data System (ADS)

The inland northwest of the United States contains a large intraplate igneous province that was initiated at ~16.6 Ma and is still active at the present. Its products include the Miocene Columbia River Basalt Group (CRBG), Miocene to Quaternary basalts and rhyolites of the High Lava Plains and the Snake River Plain, and the Quaternary Yellowstone volcanic plateau. The total volume of magma produced is uncertain, but approximately 2.5 x 105 km3 of basalts were erupted during the first million years of activity; applying magma supply rates calculated for the Snake River Plain, the total volume of mantle-derived basalt represented by the entire province may be twice that figure. Snake River Plain rhyolites are notable for the abundance of 18O-depleted units (<6‰) compared to most volcanic rocks on Earth. Low-?18O rhyolitic magma requires a source component that has exchanged oxygen at high temperatures with surface derived meteoric fluids; the degree of 18O-depletion seen in Snake River Plain rhyolites therefore requires a dominant proportion of meteoric-hydrothermally altered shallow crust among their source materials. No previous modeling has attempted to simultaneously satisfy constraints from O, Nd, Pb, and Sr isotopes for both rhyolites and basalts of the Snake River Plain using unmodified end member compositions from real surface samples. Any model for low ?18O Snake River Plain rhyolites must first account for O isotopes, because oxygen is ~50% of any silicate rock. We avoid the assumption that the geochemical character of the Snake River Plain basalts is wholly inherited from the mantle. Instead, we choose crustal materials that are abundantly exposed in proximity to the province (i.e. Idaho Batholith granitoids) and basalts that are generally accepted as primitive mantle-derived compositions (i.e. Steens basalts). The influence of continental crust on the chemistry of hotspot eruptives has been well documented. We assume this as a starting point, and construct mass balance models in order to find the simplest possible explanation for the observed features of the Snake River Plain rhyolites. We show that, when the Yellowstone hotspot track including the Columbia River and Steens basalts is treated as a single province derived ultimately from a common mantle source, the isotope geochemistry of these lavas and tuffs can be explained to a first order by simple mixing of asthenosphere-derived basalt (10%-40%) and granitic crust of the Idaho batholith (60%-90%). This model is consistent with, but does not require, a stationary mantle plume as the origin of the province.

Boroughs, S.; Wolff, J. A.; Starkel, W. A.

2012-12-01

335

Chewing through the Miocene: an examination of the feeding musculature in the ground sloth Hapalops from South America (Mammalia: Pilosa)  

PubMed Central

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.

Naples, Virginia L.; McAfee, Robert K.

2014-01-01

336

Chewing through the Miocene: an examination of the feeding musculature in the ground sloth Hapalops from South America (Mammalia: Pilosa).  

PubMed

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

Naples, Virginia L; McAfee, Robert K

2014-01-01

337

Geological and Hydrodynamical Examination of the Bathyal Tsunamigenic Origin of Miocene Conglomerates in Chita Peninsula, Central Japan  

NASA Astrophysics Data System (ADS)

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.

Tachibana, Toru; Tsuji, Yoshinobu

2011-06-01

338

Early evidence for complex social structure in Proboscidea from a late Miocene trackway site in the United Arab Emirates  

PubMed Central

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.

Bibi, Faysal; Kraatz, Brian; Craig, Nathan; Beech, Mark; Schuster, Mathieu; Hill, Andrew

2012-01-01

339

The Cenozoic Diversity of Agglutinated Foraminifera - Evidence for a late Oligocene to early Miocene diversification event  

NASA Astrophysics Data System (ADS)

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.

Kaminski, Michael; Setoyama, Eiichi; Kender, Sev; Cetean, Claudia

2014-05-01

340

Palinspastic reconstruction of southeastern California and southwestern Arizona for the middle Miocene  

NASA Astrophysics Data System (ADS)

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.

Richard, Stephen M.

1992-12-01

341

Controls and evolution of fan delta systems in the Miocene Pohang Basin, SE Korea  

NASA Astrophysics Data System (ADS)

The Miocene Pohang Basin, southeastern Korea, occurs in the eastern part of the NE-SW-trending Yangsan Fault which has experienced right-lateral strike-slip deformation since the Eocene. During the Miocene, however, the strike-slip movement was negligible and instead was under extensional regime. Large-scale drainage systems were developed at the junction between the strike-slip zone and the oblique transfer faults, acting as major sources for coarse-grained sediments. High rate of sediment supply and rapid subsidence of the hanging wall resulted in the progradation of large-scale Gilbert-type fan deltas (Doumsan, Duksung and Gohyun systems) which all show a radial distributional pattern. Along the steeply inclined footwall scarps, created by NE-SW-trending faults, the drainage systems were relatively small. Here, low rate of sediment supply formed scree-apron-type (Malgol and Yugye systems) and steep-faced slope-type (Maesan system) fan deltas. Based on variations in sedimentary facies and distribution, architecture and overlapping patterns, the fan delta systems in the Pohang Basin can be divided into four stages of evolution. During the early stage (Early Miocene), alluvial fans prograded into shallow-marine setting. In the Doumsan and Duksung systems, high rate of sediment supply and rapid rise of relative sea level resulted in the transformation of shoal-water-type to Gilbert-type foresets. In the Malgol and Maesan systems, rapid sea-level rise accompanied with low rate of sediment supply caused transformation of alluvial fans to scree-apron-type and steep-faced slope-type fan deltas, respectively. In the second stage, subsidence of the hanging wall formed large-scale truncation surfaces in the Doumsan and Duksung fan deltas. Coarse-grained sediments were continuously supplied in the Doumsan system, whereas only fine-grained sediments were deposited in the Duksung system. In the Malgol system, sediment supply was almost terminated in this stage. In the third stage (Middle Miocene), sediment supply rate of the Doumsan fan delta decreased abruptly and the system was overlain by fine-grained Gilbert-type deposits. The Duksung fan delta was overlain by the Maesan and Gohyun systems. The Maesan system prograded further basinward. During the last stage (Late Miocene), sediment supply of the Doumsan and Maesan systems was also terminated and the entire basin was draped by fine-grained biogenic materials (mainly diatoms).

Hwang, I. G.; Chough, S. K.; Hong, S. W.; Choe, M. Y.

1995-08-01

342

Palynology, paleoclimatology and correlation of middle Miocene beds from Porcupine River (locality 90-1), Alaska  

USGS Publications Warehouse

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.

White, J. M.; Ager, T. A.

1994-01-01

343

Pacific warm pool and cold tongue evolution since late Miocene: Implications for El Niño  

NASA Astrophysics Data System (ADS)

El Niño - Southern Oscillation (ENSO) is a consequence of tropical Pacific ocean-atmosphere dynamics and exerts control on Earth's interannual climate variability. Sea surface temperatures (SSTs) in the Pacific warm pool and cold tongue have been shown to be diagnostic for the strength of the Walker Circulation and ENSO conditions. Ancient SST reconstructions suggest that the temperature of the Pacific warm pool was invariant during the Plio-Pleistocene, whereas the cold tongue was much warmer in the Pliocene and then subsequently cooled. The appearance of a negligible east-west equatorial Pacific Ocean temperature gradient during the Pliocene is used to infer substantially reduced cold water equatorial upwelling, a weak Walker Circulation, and a "permanent" El Niño. Some recent records suggest otherwise. For example, high-resolution records in Pacific and Mediterranean region show quasi-periodic climate variability (2-7 years) during the late Miocene - Pliocene, consistent with ENSO conditions and in conflict with the prevailing climate paradigm. Here we show a multi-proxy (TEX86, Uk'37), multi-site reconstruction of SSTs in the Pacific warm pool (ODP Sites 806 and 1143) and cold tongue (ODP 846 and 850) since late Miocene (~12 Ma). TEX86 temperatures from both sites show long-term cooling of the western warm pool since late Miocene, in contrast to an apparent invariant temporal character previously assumed. At Site 850, cold tongue temperatures from both TEX86 and Uk'37 also show a cooling trend, with TEX86 much more variable than Uk'37. Further, TEX86-calculated temperatures are consistently cooler than Uk'37 temperatures since ~6 Ma, and suggest different production depths or seasons, whereas deviations of TEX86 and Uk'37 signals might be recording physical/chemical property changes in the cold tongue (e.g., the strength and seasonality of upwelling, stratification and nutrient supply). When all records are stacked, a ~3°C zonal temperature gradient persists between 12 and 6 Ma, and then increases toward modern-day conditions. Considering sedimentary records that show interannual variability during late Miocene - Pliocene, a ~3°C mean zonal gradient might be large enough to sustain El Niño - La Niña variability and thus directly challenges the notion of a permanent El Niño state during warmer global conditions. The persistence a significant and consistent zonal gradient during warmer Miocene conditions suggests that the Pliocene evolution of stronger E-W equatorial SST gradients was driven by non-linear effects related to declining global temperatures or resulted from threshold effects related to the tectonic evolution of the region.

Zhang, Y.; Pagani, M.

2012-12-01

344

Dated molecular phylogenies indicate a Miocene origin for Arabidopsis thaliana  

PubMed Central

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.

Beilstein, Mark A.; Nagalingum, Nathalie S.; Clements, Mark D.; Manchester, Steven R.; Mathews, Sarah

2010-01-01

345

Dated molecular phylogenies indicate a Miocene origin for Arabidopsis thaliana.  

PubMed

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

Beilstein, Mark A; Nagalingum, Nathalie S; Clements, Mark D; Manchester, Steven R; Mathews, Sarah

2010-10-26

346

Post-Miocene Right Separation on the San Gabriel and Vasquez Creek Faults, with Supporting Chronostratigraphy, Western San Gabriel Mountains, California  

USGS Publications Warehouse

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.

Beyer, Larry A.; McCulloh, Thane H.; Denison, Rodger E.; Morin, Ronald W.; Enrico, Roy J.; Barron, John A.; Fleck, Robert J.

2009-01-01

347

Paleo-environment in the upper amazon basin during early to middle Miocene times  

NASA Astrophysics Data System (ADS)

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 Solimões basin, Mariñame (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 Mariñame 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 (Mariñame) 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 Solimões 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.

van Soelen, Els; Hoorn, Carina; Santos, Roberto V.; Dantas, Elton L.; Sinninghe Damsté, Jaap S.; Kim, Jung-Hyun

2014-05-01

348

Relating Major Surface Processes to the Deep Earth — The Importance of the Miocene  

NASA Astrophysics Data System (ADS)

Many global scale tectonic, oceanic and climate changes began in the Tertiary with global tectonics as the underlying driving force and changed the world. In full flower by the beginning of the Middle Miocene around 16 Ma, these changes continued through the Late Miocene into the present so we can firmly say that most of our modern world, continental glaciations excepted, began in the Middle and Late Miocene. We summarize in a flow diagram how the major earth surface processes active in the Miocene are related to the Deep Earth as understood by recent advances in seismic tomography. This 11 Ma interval had two global orogenic zones, the Alpine-Tethyan orogen from Gibraltar across southern Asia into Vietnam and around the Pacific Rim, both crustal expressions of downwellings taking place, especially in the upper mantle. These downwellings are balanced by upwellings in the lower mantle in and on the rim of the African and Pacific superplumes, which are large, low-shear velocity provinces; part of the rising plumes originated from the most extensively melted regions of the core-mantle boundary layer, D", where heat flow from the outer core is highest. Together these up-and downwellings indicate that mantle convection extended, at least periodically, through the whole mantle and reflected lateral variations in convection and heat flow in the cooling and slowly crystallizing outer core. Correlation of mantle convection with surface features is most evident in the uppermost mantle whose dynamic topography is readily reflected by the subsidence and tilting of continents moving toward the downwelling zones. Because they are closely synchronous, these two orogenic belts had enormous consequences for the earth's surface, and because they are close to us in time, they are easy to study and sample. Thus the Miocene is ideal to study for both its many global intra connections and for their link to the Deep Earth. As these two orogenies developed, they changed a global warm water ocean into our present cooler, more fragmented system with a cooler atmosphere. Higher plateaus and uplifted mountains deflected jet streams, expanded rain shadows promoting desertification, favored initial mountain glaciation, and helped cool air temperatures. Upwelling was enhanced on both sides of the Pacific basin, silica production shifted from the Atlantic to the Pacific and Indian Oceans, more mud and sand were brought to the ocean causing many passive margins to prograde, and hemipelagic mud became more abundant off continental margins. At the very end of the Miocene even the Mediterranean dried up, as it was isolated by the Alpine orogeny at Gibraltar. Onshore, epeirogenic uplift was widespread both in the interiors of the continents and along many of their margins. Active convergent margins changed continental tilts, completely altered some rivers, and formed new ones with new deltas, some on the other side of a continent. The above changes greatly altered the surface environment and induced many significant changes in flora and fauna and their distribution and have great economic importance. Many of the major geochemical cycles of the ocean and atmosphere also experienced major changes at this time. We posit that the generalizations ultimately emerging from the Miocene will apply to all the Phanerozoic and far back into the Precambrian and that are all tied to Deep Earth.

Potter, P. E.; Szatmari, P.

2012-12-01

349

History of the development of the temperate forest flora in Kazakhstan, U.S.S.R. from the Oligocene to the Early Miocene  

Microsoft Academic Search

Exact dating of the floras existing in western Kazakhstan during the Oligocene and Early Miocene permits a detailed examination\\u000a of the formation of a temperate flora during the Rupelian (Early Oligocene), Chattian (Late Oligocene), Aquitanian (the beginning\\u000a of Early Miocene) and the Burdigalian (end of Early Miocene) Ages and at the same time an establishment of the sequence in\\u000a the

Sergey G. Zhilin

1989-01-01

350

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)

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.

Vasilyan, Davit; Böhme, Madelaine; Winklhofer, Michael

2010-05-01

351

Miocene and Pliocene lacustrine and fluvial sequences, Upper Ramparts and Canyon village, Porcupine river, east-central Alaska  

USGS Publications Warehouse

Cenozoic strata exposed along the Porcupine River between the Upper Ramparts and Canyon Village, Alaska, can be divided into five unconformity-bounded units (sequences) which are: lower and middle Miocene unit A, the white sandy fluvial sequence with peat beds; middle Miocene unit B, the basalt sequence-part B1 is basalt, and part B2 is organic-rich sedimentary beds; upper Miocene unit C, mudrock-dominated lake sequence; late Miocene or Pliocene to Pleistocene unit D, terrace gravels, detrital organic matter and associated sediments, and Holocene unit E, mixed sand and gravel-rich sediment and other sedimentary material including peat and eolian silt. The sequence (unit A) of lower and middle Miocene fluvial deposits formed in streams and on flood plains, just before the inception of local volanism. Fossil pollen from unit A suggests conifer-dominated regional forests and cool temperate climates. Peat beds and lake deposits from unit B contain pollen that indicates a warmer temperate climate coinciding with the middle Miocene thermal maximum. The lake deposits (unit C) downstream from the basalts accumulated in a small basin which resulted from a hydrologic system that was dammed in the late Miocene but breached soon thereafter. The lower part of the terrace gravels (unit D) expresses breaching of the dammed hydrologic system (of unit C). The Porcupine River became a major tributary of the Yukon River in late Pleistocene time when Laurentide ice blocked drainage from the Yukon interior basins causing meltwater to spill over the low divide separating it from the Porcupine River drainage initiating erosion and capture of the Yukon interior basins. ?? 1994.

Fouch, T. D.; Carter, L. D.; Kunk, M. J.; Smith, C. A. S.; White, J. M.

1994-01-01

352

CONTROLS OF EXTENSION ON MIOCENE ARC MAGMATISM IN THE CENTRAL SIERRA NEVADA (CA)  

NASA Astrophysics Data System (ADS)

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.

Busby, C.; Putirka, K. D.; Hagan, J. C.; Koerner, A.; Melosh, B. L.

2009-12-01

353

Assessment of East Antarctic ice flow directions, ice grounding events, and glacial thermal regime across the middle Miocene climate transition from the ANDRILL-SMS and CRP drill holes  

NASA Astrophysics Data System (ADS)

Here we present a synthesis of early and middle Miocene ice sheet development based on facies analyses and multiple compositional studies on the AND-2A and CRP drillcores from the Ross Sea, ca. 10 km off the coast of East Antarctica. The middle Miocene is characterized by one of the three largest shifts in deep-sea oxygen isotope records. During this time the East Antarctic ice sheet became dry-based at high elevation in the Transantarctic Mountains and advanced across the Ross Sea continental shelf to create widespread glacial unconformities. However, detailed proxy records also indicate that ice development was complex and may have occurred in a stepwise fashion, instead of one major episode. Our analyses of “grounded ice” diamictites from both the CRP and AND-2A cores show a significant change in composition across the middle Miocene transition. More detailed analyses of the stratigraphic distribution of facies, heavy mineral provenance, particle size, and major and trace element geochemistry in AND-2A show that relatively large polythermal ice-sheets similar in size to the modern were already present between 17.6 and 17.1 Ma. These results are in agreement with proxy records suggesting that Antarctic ice volumes were larger than today’s volume during the Mi-1b glaciation. Between 17.1 and 15.6-14.9 Ma, a predominance of iceberg debris sourced from the Ferrar Group in the Transantarctic Mountains suggests vigorous glacial erosion and fjord incision by East Antarctic outlet glaciers. The facies characteristics and comparison with compositional data from Neogene tills in the Transantarctic Mountains further suggest that the East Antarctic ice sheet may have been smaller than today during the Miocene climatic optimum (~17-15 Ma) with ice possibly reaching sea level only near the central Transantarctic Mountains. Advance of the grounding line and the development of glacial flow patterns compatible with a larger ice sheet than the modern commenced between 15.6 and 14.7 Ma and was established prior to 14.2 Ma. These results suggest an earlier onset of Antarctic ice growth across the middle Miocene climate transition than is generally inferred from geochemical proxy records.

Passchier, S.; Hauptvogel, D.; Hansen, M.; Falk, C.; Martin, L.

2010-12-01

354

S concentrations and its speciation in Miocene basaltic magmas north and south of Gran Canaria (Canary Islands): constraints from glass inclusions in olivine and clinopyroxene  

NASA Astrophysics Data System (ADS)

We report S concentrations and relative proportions of SO 42- and S 2- in OL- and CPX-hosted glass inclusions and in host glassy lapilli from Miocene basaltic hyaloclastites drilled north and south of Gran Canaria during ODP Leg 157. Compositions of glass inclusions and lapilli resemble those of subaerial Miocene shield basalts on Gran Canaria and comprise mafic to more evolved tholeiitic to alkali basalt and basanite (10.3-3.7 wt.% MgO, 44.5-56.9 wt.% SiO 2). Glass inclusions fall into three groups based on their S concentrations: a high-sulfur group (1050 to 5810 ppm S), an intermediate-sulfur group (510 to 1740 ppm S), and a low-sulfur group (<500 ppm S). The most S-rich inclusions have the highest and nearly constant proportion of sulfur dissolved as sulfate determined by electron microprobe measurements of S K? peak shift. Their average S 6+/S total value is 0.75 ± 0.09, unusually high for ocean island basalt magmas. The low-sulfur group inclusions have low S 6+/S total ratios (0.08 ± 0.05), whereas intermediate sulfur group inclusions show a wide range of S 6+/S total (0.05-0.83). Glassy lapilli and their crystal-hosted glass inclusions with S concentrations of 50 to 1140 ppm S have very similar S 6+/S total ratios of 0.36 ± 0.06 implying that sulfur degassing does not affect the proportion of SO 42- and S 2- in the magma. The oxygen fugacities estimated from S 6+/S total ratios and from Fe 3+/Fe 2+ ratios in spinel inclusions range from NNO-1.1 to NNO+1.8. The origin of S-rich magmas is unclear. We discuss (1) partial melting of a mantle source at relatively oxidized fO 2 conditions, and (2) magma contamination by seawater either directly or through magma interaction with seawater-altered Jurassic oceanic crust. The intermediate sulfur group inclusions represent undegassed or slightly degassed magmas similar to submarine OIB glasses, whereas the low-sulfur group inclusions are likely to have formed from magmas significantly degassed in near-surface reservoirs. Mixing of these degassed magmas with stored volatile-rich ones or volatile-rich magma replenishing the chamber filled by partially degassed magmas may produce hybrid melts with strongly varying S concentrations and S 6+/S total ratios.

Gurenko, Andrey A.; Schmincke, Hans-Ulrich

2000-07-01

355

The Owen Ridge uplift in the Arabian Sea: implications for the sedimentary record of Indian monsoon in Late Miocene  

NASA Astrophysics Data System (ADS)

The pelagic cover of the Owen Ridge in the Arabian Sea recorded the evolution of the Indian monsoon since the Middle Miocene. The uplift of the Owen Ridge resulted from tectonic processes along the unidentified fossil Miocene India-Arabia plate boundary. Based on seismic reflection data tied with deep-sea drillings to track the Miocene India-Arabia plate boundary, we propose a new timing for the uplift of the Owen Ridge and highlight its impact on the record of climate changes in pelagic sediments. The new dataset reveals a fracture zone east of the Owen Ridge corresponding to the fossil plate boundary, and documents that the main uplift of the Owen Ridge occurred close to ~8.5 Ma, and is coeval with a major uplift of the east Oman margin. Late Miocene deformation at the India-Arabia plate boundary is also coeval with the onset of intra-plate deformation in the Central Indian Ocean, suggesting a kinematic change of India and surrounding plates in the Late Miocene. The uplift of the Owen Ridge above the lysocline at ~8.5 Ma accounts for a better preservation of Globigerina bulloides in the pelagic cover, previously misinterpreted as the result of a monsoon intensification event.

Rodriguez, Mathieu; Chamot Rooke, Nicolas; Huchon, Philippe; Fournier, Marc; Delescluse, Matthias

2014-05-01

356

The Owen Ridge uplift in the Arabian Sea: Implications for the sedimentary record of Indian monsoon in Late Miocene  

NASA Astrophysics Data System (ADS)

The pelagic cover of the Owen Ridge in the Arabian Sea recorded the evolution of the Indian monsoon since the Middle Miocene. The uplift of the Owen Ridge resulted from tectonic processes along the previously unidentified Miocene India-Arabia plate boundary. Based on seismic reflection data tied with deep-sea drilling to track the Miocene India-Arabia plate boundary, we propose a new timing for the uplift of the Owen Ridge and highlight its impact on the record of climate changes in pelagic sediments. The new dataset reveals a fracture zone east of the Owen Ridge corresponding to the fossil plate boundary, and documents that the main uplift of the Owen Ridge occurred close to ˜8.5 Ma, and is coeval with a major uplift of the east Oman margin. Late Miocene deformation at the India-Arabia plate boundary is also coeval with the onset of intra-plate deformation in the Central Indian Ocean, suggesting a kinematic change of India and surrounding plates in the Late Miocene. The uplift of the Owen Ridge above the lysocline at ˜8.5 Ma accounts for a better preservation of Globigerina bulloides in the pelagic cover, previously misinterpreted as the result of a monsoon intensification event.

Rodriguez, Mathieu; Chamot-Rooke, Nicolas; Huchon, Philippe; Fournier, Marc; Delescluse, Matthias

2014-05-01

357

Plate tectonic significance of Late Oligocene/Early Miocene deep sea sedimentation at Maewo, Vanuatu (New Hebrides)  

NASA Astrophysics Data System (ADS)

Eight lithofacies representing a westward trending, deep sea fan, dominantly deposited from mass flow mechanisms, are recognised in geologic sections in the lower part of the Sarava Formation, of Late Oligocene/Early Miocene age, on Maewo Island, Vanuatu, New Hebrides. Also present representing the floor on which the deep sea fan prograded are non-calcareous, red siltstone and minor green siltstone which indicate deposition beyond the calcareous compensation depth, i.e. a depth greater than 4.25 km, and rare thin airfall ash. Previous workers proposed that rifting occurred in the area now occupied by Maewo during the Mid Miocene. However, the great depth at which the Late Oligocene/Early Miocene strata were deposited suggests that rifting occurred prior to the Late Oligocene. Rifting may have occurred even earlier because Pentecost Island, which lies south of Maewo, has a dismembered ophiolite suite which ranges in age from 35-28 Ma (Oligocene). The ophiolite suite may have formed in an interarc environment. The writer's reconstruction of the Oligocene arc system of the New Hebrides is an analogue of the present day Mariana Arc System. Interarc rifting ceased by the Early Miocene and during the Mid-Late Miocene the subduction of zone may have migrated westwards to lie along the Maewo-Pentecost axis.

Neef, G.

1982-08-01

358

Miocene-Quaternary structural evolution of the Uyuni-Atacama region, Andes of Chile and Bolivia  

NASA Astrophysics Data System (ADS)

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 ( ?1, computed with striated fault planes) and a vertical least principal stress ( ?3), followed by pervasive strike-slip faulting with the same NW-SE-trending ?1 and a horizontal NE-SW ?3. The fourth event, dating to the late Pliocene-Quaternary is characterized by normal faulting: the ?3 still trends NE-SW, whereas the intermediate principal stress ?2 exchanged with ?1. 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 ?1 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.

Tibaldi, A.; Corazzato, C.; Rovida, A.

2009-06-01

359

Paleomagnetic reversals in Miocene dikes, and tectonic evolution of the Crossman block, Mohave Mountains, Arizona  

SciTech Connect

Paleomagnetic data, isotopic ages, and compositions all suggest a common, coeval magmatic source for early Miocene volcanic rocks and a large dike swarm in the Crossman block (CB), central Mohave Mountains, AZ, Colorado River extensional corridor. The CB is a coherent 12-to-15-km-thick piece of crust in the upper plate of the Whipple detachment fault, which tilted by 90 to 100 to the SW in response to movements on the fault. A swarm of early Miocene dikes dip shallowly to the NE, and account for 20% or more of CB thickness. Compositions of dikes and lavas from the CB ranged from basaltic to rhyolitic. A calk-alkaline trend is evident in spite of widespread alteration, and a few of the dikes can be traced into the flow sequence. Reliable dike ages are between 20 and 18 Ma, and those for lavas range from 21.5 to 17.9 Ma. Dikes in the CB show both normal and reversed magnetic polarities contained in high temperature and high coercivity components. Tests of stability in a baked contact supports a Miocene age for the magnetizations. This interpretation supports and adds detail to a two-stage model for tilting of the CB at 19.9[+-]0.5 Ma, based on an unconformity in the volcanic stratigraphy. An explanation for such a rapid tilting of a large crustal fragment may be that friction between lower and upper plate was lowered by a large volumes of magmas that either were generated or ponded at the level of the Whipple detachment fault, at about 20 Ma.

Nielson, J.E.; Nakata, J.K. (Geological Survey, Menlo Park, CA (United States)); Pease, V.L.

1993-04-01

360

Paleomagnetism of the Miocene dikes in Bare Mountain, southwest Nevada: Implications for regional tectonics  

SciTech Connect

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.

Zhang, Y.; Gillett, S.L.; Karlin, R.E.; Schweickert, R.A. (Univ. of Nevada, Reno, NV (United States). Dept. of Geological Sciences)

1993-04-01

361

Sedimentary facies, mineralogy, and geochemistry of the sulphate-bearing Miocene Dam Formation in Qatar  

NASA Astrophysics Data System (ADS)

The Miocene deposits of the Dam Formation were deposited in a narrow seaway stretching along the western edge of the Qatar Arch. During the initial stages of basin evolution the rising Zagros Mts. delivered debris in this fore deep basin. The paleocurrent and paleogeographic zonation are reflected by the heavy mineral assemblage, by the spatial distribution of phyllosilicates and the various types of sulphate. From NW towards the SE, the contents of smectite and palygorskite increase, whereas the illite and kaolinite contents decrease. Mega crystals of gypsum are found in the NW and massive fine-grained gypsum in the SE of the basin. During the waning stages of basin subsidence, the Arabian Shield became more and more important as a source for the Miocene sediments. In this study, the Dam Formation was subdivided into 7 members/lithofacies associations (lower, middle, upper Salwa, and Al Nakhsh Members, Abu Samrah Member). The Salwa Members at the base of the Dam Formation consists of heterolithic siliciclastic-calcareous sediments which were laid down under meso- to microtidal conditions. The Al Nakhsh Members formed under macrotidal conditions with sub- to supratidal depositional environments passing into continental ones. Celestite, gypsum, and microbial mats (stromatolites) are very widespread in these sabkha sediments. Crystals of gypsum and the thickness of stromatolites tremendously increase towards younger sediments indicating thereby a close genetic link between growth of microbial domes and gypsum precipitation. Throughout the Abu Samrah Member marine calcareous sediments were deposited in a microtidal wave-dominated environment. Dissolution of Eocene evaporites at depth governed the lithofacies differentiation in the Miocene Dam Formation.

Dill, H. G.; Botz, R.; Berner, Z.; Stüben, D.; Nasir, S.; Al-Saad, H.

2005-01-01

362

Miocene fossil hydrothermal system associated with a volcanic complex in the Andes of central Chile  

NASA Astrophysics Data System (ADS)

Cenozoic deposits in the Andes of central Chile have been affected by very low-grade burial metamorphism. At about 33°S in the Cuesta de Chacabuco area, approximately 53 km north of Santiago, two Oligocene and Miocene volcanic units form a ca. 1300-m-thick rock pile. The Miocene unit corresponds to a volcanic complex composed of two eroded stratovolcanoes. Secondary mineral assemblages in both units were studied petrographically and using X-ray diffraction and electron microprobe analyses. Most of the igneous minerals are wholly or partially preserved, and the ubiquitous secondary minerals are zeolites and mafic phyllosilicates. The alteration pattern observed is characterized by a lateral zonation in secondary mineralogy related to a lateral increase in temperature but not to stratigraphic depth. The following three zones were established, mainly based on the distribution of zeolites: zone I comprises heulandite, thomsonite, mesolite, stilbite and tri-smectite; zone II contains laumontite, yugawaralite, prehnite, epidote and chlorite; and zone III comprises wairakite, epidote, chlorite, diopside, biotite and titanite. For each zone, the following temperature ranges were estimated: zone I, 100-180 °C; zone II, 180-270 °C; and zone III, 245-310 °C. The alteration episode was characterized by a high Pfluid/ Ptotal ratio (ca. 1.0), although slightly variable, a high geothermal gradient of ca. 160 °C km -1 and fluid pressures below 500 bars. Although temperature was the main control on the mineral zonation, several interrelated parameters, mainly fluid composition, porosity and permeability, were also important. Hot, near neutral to slightly alkaline pH, alkali chloride hydrothermal fluids with very low dissolved CO 2 contents deposited the secondary minerals. The alteration pattern is the result of depositing fluids in outflow regions from a hydrothermal system developed inside a volcanic complex during the Miocene. The hydrothermal system has been eroded to a maximum depth of 1.7 km.

Fuentes, Francisco; Aguirre, Luis; Vergara, Mario; Valdebenito, Leticia; Fonseca, Eugenia

2004-11-01

363

Small mammal carbon isotope ecology across the Miocene-Pliocene boundary, northwestern Argentina  

NASA Astrophysics Data System (ADS)

The late Miocene expansion of plants using the C4 photosynthetic pathway in South America has been documented by tooth enamel carbon isotope ratios (?13Cen). However, a more detailed understanding of this ecological event is hampered by poor chronological control on the widespread fossil localities from which isotopic data are derived. This study develops a ?13Cen record from a single 2500 m-thick stratigraphic section in subtropical South America. Strata at Puerta de Corral Quemado (PCQ), northwestern Argentina, span 9 to 3.5 Ma in age, and existing paleosol carbonate data (?13Cpc) document C4 expansion across the Miocene-Pliocene boundary. Comparison of ?13Cen data with ?13Cpc data at high stratigraphic resolution refines understanding of this ecological event in South America. Small mammal ?13Cen data in particular are complementary to that of large mammal and paleosol ?13C data. Small mammal teeth integrate isotopic data over much shorter temporal and spatial scales than large mammal teeth, providing a sensitive measure of local vegetation and placing constraints on the landscape distribution of C3 and C4 plants. Explicit consideration of the distinctive carbon isotope enrichment factor between enamel and diet for rodents (?*en-diet = 11‰, as opposed to 14‰ for large mammals) allows for unequivocal inference of C4 vegetation ~ 1 Ma prior to that inferred from large mammal ?13Cen data, and ~ 2 Ma prior to ?13Cpc data. This multiproxy record demonstrates that C4 plants were a stable component of the ecosystem hundreds of thousands of years prior to their major ecological expansion, and that the expansion of C4 plants was pulsed at PCQ. Two periods of ecological change are demonstrated by ?13C and ?18O data at ~ 7 Ma and 5.3 Ma (coincident with the Miocene-Pliocene boundary). Development of small mammal ?13Cen records on other continents may provide similar insight into the early stages of the global C4 event.

Hynek, Scott A.; Passey, Benjamin H.; Prado, José Luis; Brown, Francis H.; Cerling, Thure E.; Quade, Jay

2012-03-01

364

Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama  

PubMed Central

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.

Pimiento, Catalina; Ehret, Dana J.; MacFadden, Bruce J.; Hubbell, Gordon

2010-01-01

365

A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia.  

PubMed

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

Rybczynski, Natalia; Dawson, Mary R; Tedford, Richard H

2009-04-23

366

Late Miocene decoupling of oceanic warmth and atmospheric carbon dioxide forcing.  

PubMed

Deep-time palaeoclimate studies are vitally important for developing a complete understanding of climate responses to changes in the atmospheric carbon dioxide concentration (that is, the atmospheric partial pressure of CO(2), p(co(2))). Although past studies have explored these responses during portions of the Cenozoic era (the most recent 65.5 million years (Myr) of Earth history), comparatively little is known about the climate of the late Miocene (?12-5 Myr ago), an interval with p(co(2)) values of only 200-350?parts per million by volume but nearly ice-free conditions in the Northern Hemisphere and warmer-than-modern temperatures on the continents. Here we present quantitative geochemical sea surface temperature estimates from the Miocene mid-latitude North Pacific Ocean, and show that oceanic warmth persisted throughout the interval of low p(co(2)) ?12-5 Myr ago. We also present new stable isotope measurements from the western equatorial Pacific that, in conjunction with previously published data, reveal a long-term trend of thermocline shoaling in the equatorial Pacific since ?13?Myr ago. We propose that a relatively deep global thermocline, reductions in low-latitude gradients in sea surface temperature, and cloud and water vapour feedbacks may help to explain the warmth of the late Miocene. Additional shoaling of the thermocline after 5?Myr ago probably explains the stronger coupling between p(co(2)), sea surface temperatures and climate that is characteristic of the more recent Pliocene and Pleistocene epochs. PMID:22678287

LaRiviere, Jonathan P; Ravelo, A Christina; Crimmins, Allison; Dekens, Petra S; Ford, Heather L; Lyle, Mitch; Wara, Michael W

2012-06-01

367

Incremental growth and mineralogy of Pannonian (Late Miocene) sciaenid otoliths: paleoecological implications  

NASA Astrophysics Data System (ADS)

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.

Kern, Zoltán; Kázmér, Miklós; Bosnakoff, Mariann; Váczi, Tamás; Bajnóczi, Bernadett; Katona, Lajos

2012-04-01

368

Genetic stratigraphy of a part of the Miocene Congo Fan, West Africa  

NASA Astrophysics Data System (ADS)

The stratigraphic framework and reservoir distribution are essential factors controlling the accumulation of petroleum in the Miocene Congo Fan. Analysis of cores, well logs, and seismic data suggest that the submarine fan autocycle (genetic cycle) is presented by sequence of slump, debrite, densite currents, and turbidites, whereas allocycles (long-term cycles) may be composed of several autocycles (short-term cycles) that, appear as a stacking pattern or retrogradational fan. Scour surfaces at the base of gravity flow channel, stable hemipelagic mudstone section, and the surface between fan retrogradation and progradation can be used for the correlations.

Jiang, Zhenglong; Wang, Rong; Zheng, Wenbo

2014-07-01

369

Blake Plateau: control of Miocene sedimentation patterns by large- scale shifts of the Gulf Stream axis.  

USGS Publications Warehouse

The distribution of buried channel networks within Cenozoic sequences of the Blake Plateau and their correlation with global sea-level oscillations indicate that the Gulf Stream axis shifted landward against the Florida-Hatteras Slope during sea-level highstands and seaward across the central Blake Plateau during sea-level lowstands. A sedimentation model incorporating axial shifts of the Gulf Stream successfully predicts the Miocene stratigraphy of the Florida-Hatteras Slope and Blake Plateau as defined by seismic and drill-hole data. -Authors Cenozoic sequences Blake Plateau sea level oscillations North Atlantic

Pinet, P. R.; Popenoe, P.

1982-01-01

370

Aragonian stratigraphy reconsidered, and a re-evaluation of the middle Miocene mammal biochronology in Europe  

NASA Astrophysics Data System (ADS)

The recently collected fauna of Armantes 1A in Chron C5Br of the Armantes section necessitates reinterpretation of the previous bio- and magnetostratigraphical correlations between the Armantes and Vargas sections (Calatayud-Daroca Basin, Central Spain) [W. Krijgsman, M. Garcés, C.G. Langereis, R. Daams, J. van Dam, A.J. van der Meulen, J. Agust?´, L. Cabrera, A new chronology for the Middle to Late Miocene continental record in Spain, Earth Planet. Sci. Lett. 142 (1996) 367-380]. The long reversal in the Vargas section is now correlated to C5Br, instead of to C5Cr, on the basis of the biostratigraphical correlation of Armantes 1A to the faunas of Fuente Sierra 2 and 3 (in the Vargas section), which are situated in the basal part of the Middle Aragonian (MN5). This leads to the revised age of 16.0 Ma for the Early-Middle Aragonian (MN 4/5) boundary. Our age estimate of the MN5/6 boundary is maintained at ca. 13.75 Ma. The Vargas section is now considered to start in Chron C5Cn.2r and to end in C5Bn.1n. As a result of the revised correlation the duration of the time gap between the fossiliferous parts of Vargas and the younger Aragón section, previously estimated as ca. 1.5 Myr, is now reduced to less than 200,000 years. The tie points of the European mammal units (MN4-MN6) to the geomagnetic polarity time scale [F.F. Steininger, W.A. Berggren, D.V. Kent, R.L. Bernor, S. Sen, J. Agust?´, Circum-Mediterranean Neogene (Miocene and Pliocene) marine-continental chronologic correlations of European mammal units, in: R.L Bernor, V. Fahlbusch, H.-W. Mittmann (Eds.), The Evolution of Western Eurasian Neogene Mammal Faunas, Columbia Univ. Press, New York, 1996, pp. 7-46] are evaluated. Our age estimates of the MN4/5 and MN5/6 boundaries are compatible with the new magnetostratigraphic calibration of middle Miocene mammal zones in the Swiss Molasse basin [O. Kempf, T. Bolliger, D. Kälin, B. Engesser, A. Matter, New magnetostratigraphic calibration of Early to Middle Miocene mammal biozones of the North Alpine foreland basin, in: J.-P. Aguilar, S. Legendre, J. Michaux (Eds.), Actes du Congrès BiochroM '97, Mém. Trav. E.P.H.E. 21 (1997) 547-562].

Daams, R.; van der Meulen, A. J.; Alvarez Sierra, M. A.; Peláez-Campomanes, P.; Krijgsman, W.

1999-02-01

371

Mandible of Ouranopithecus macedoniensis (Hominidae, Primates) from a new late miocene locality of Macedonia (Greece).  

PubMed

In 1990, a new late Miocene locality named "Nikiti 1" or NKT, was discovered near the village of Nikiti (Chalkidiki, Macedonia, Greece) about 100 km east of Thessaloniki City. The locality is situated in the Nikiti Formation, which consists of yellowish sands, gravels and pebbles and has been dated to late Vallesian-early Turolian. Among the initially collected fossils there is a mandible of a hominoid primate, which is described, compared, and attributed to Ouranopithecus macedoniensis. A short review of the species in Macedonia and its phylogenetic relationships are also given. PMID:8317563

Koufos, G D

1993-06-01

372

Mid-Miocene Silicic Volcanism of the Three Fingers - Mahogany Mountain Area, SE Oregon - Revisited  

NASA Astrophysics Data System (ADS)

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.

Marcy, P.; Streck, M. J.; Ferns, M.

2013-12-01

373

Hyperreflection groups  

Microsoft Academic Search

We introduce the concept of hyperreflection groups, which are a generalization of Coxeter groups. We prove the Deletion and Exchange Conditions for hyperreflection groups, and we discuss special subgroups and fundamental sectors of hyperreflection groups. In the second half of the paper, we prove that Coxeter groups and graph products of groups are examples of hyperreflection groups.

David G. Radcliffe

2010-01-01

374

Petrology of the Miocene igneous rocks in the Altar region, main Cordillera of San Juan, Argentina. A geodynamic model within the context of the Andean flat-slab segment and metallogenesis  

NASA Astrophysics Data System (ADS)

The Altar porphyry Cu-(Au-Mo) deposit (31° 29' S, 70° 28' W) is located in the Andean Main Cordillera of San Juan Province (Argentina), in the southern portion of the flat-slab segment (28-33°S), 25 km north of the world-class porphyry Cu-Mo deposits of Los Pelambres and El Pachón. Igneous rocks in the area have been grouped into the Early Miocene Lower Volcanic Complex -composed of intercalations of lava flows and thin volcaniclastic units that grade upwards to a thick massive tuff- and the Middle-Late Miocene Upper Subvolcanic Suite that consists of a series of porphyritic stocks and dikes and magmatic and hydrothermal breccias. The Lower Volcanic Complex represents an Early Miocene arc (20.8 Ma ± 0.3 Ma; U-Pb age) erupted over a steep subduction zone. Their magmas equilibrated with an assemblage consisting of plagioclase- and pyroxene-dominated mineral residues, and experienced fractional crystallization and crustal contamination procesess. Their radiogenic signatures are interpreted to indicate conditions of relatively thickened continental crust in Altar during the Early Miocene, compared to the south and west. The Upper Subvolcanic Suite represents the development of a Middle-Late Miocene arc (11.75 ± 0.24 Ma, 10.35 ± 0.32 Ma; U-Pb ages) emplaced over a shallow subduction zone. A magmatic gap in Altar area betwen the Lower Volcanic Complex and Upper Subvolcanic Suite correlates with documented higher rates of compression in this period, that may have favored the storage of the USS magmas in cameras within the crust. Magmas of the Upper Subvolcanic Suite require a hornblende-bearing residual mineral assemblage that is interpreted to reflect their higher water contents. The relatively uniform radiogenic isotope compositions of the Upper Subvolcanic Suite magmas suggest a homogeneously mixed crust-mantle contribution in the source region. They have similar REE signatures as other fertile intrusives of the flat-slab. The differences observed in their isotopic signatures reflect an increase in the amount of crustal components incorporated into magmas from south (El Teniente) to north (El Indio) which correlate with an increase of crustal thickness. U-Pb ages of Altar rocks confirm a temporal connection between the ridge arrival and the magmatism associated with mineralization in this zone of the flat-slab segment. We argue that since the Middle-Late Miocene, mantle and lower crust may have been hydratated by fluids from the slab and from the Juan Fernández Ridge at the latitude of Altar, which favored the generation of the Middle-Late Miocene magmas. We also suggest that at this latitude the collision ridge-trench at ˜11 Ma and the subduction of the Juan Fernández Ridge beneath Altar region at ˜11-10 Ma may have promoted changes in the tectonic stress regime, allowing the USS magmas to rise to shallower levels in the crust. This may explain the location of a cluster of contemporaneous giant porphyry Cu-Mo deposits including El Pachón-Los Pelambres, the Altar Cu (Mo-Au) deposit, and other nearby recently discovered Cu prospects such as Piuquenes, La Coipa, Rincones de Araya and Los Azules.

Maydagán, Laura; Franchini, Marta; Chiaradia, Massimo; Pons, Josefina; Impiccini, Agnes; Toohey, Jeff; Rey, Roger

2011-07-01

375

En echelon Miocene rifting in the southwestern United States and model for vertical-axis rotation in continental extension  

SciTech Connect

Two areas of intense early Miocene crustal extension in the southwestern United States, the Colorado River trough and the central Mojave Desert, are separated by a weakly deformed area in the eastern Mojave Desert. The authors propose that these areas form a left-stepping en echelon rift system linked by a ductile detachment at depth. The en echelon geometry explains the southward loss of displacement in the central Mojave Desert and northward loss of coeval displacement in the Colorado River trough, and it incorporates seismic reflection evidence that mid-crustal Tertiary extensional mylonites continue beneath the weakly deformed area. This geometry also explains clockwise paleomagnetic declination anomalies from lower Miocene rocks as recording thin-skinned, detached rotations; large-scale block rotations are not required. Obliquity of the northeast-trending crustal-extension vector to the east-west-trending early Miocene synextensional volcanic belt may have caused the en echelon pattern to develop.

Bartley, J.M. (Univ. of Utah, Salt Lake City (United States)); Glazner, A.F. (Univ. of North Carolina, Chapel Hill (United States))

1991-12-01

376

Oxygen, strontium, and neodymium isotope composition of fossil shark teeth as a proxy for the palaeoceanography and palaeoclimatology of the Miocene northern Alpine Paratethys  

Microsoft Academic Search

The Upper Marine Molasse sediments of southern Germany were deposited during the Early to Middle Miocene, a period of significant change for the global Miocene palaeoceanography, palaeoclimate, and the regional palaeogeography because of the ongoing Alpine–Himalayan orogeny. To address the influence of the Alpine uplift on climate and oceanography of the northern Alpine molasse basin, a combined O-, Sr-, and

Torsten W. Vennemann; Ernst Hegner

1998-01-01

377

Micromorphological and geochemical characterization of Tertiary ‘freshwater carbonates’ locally preserved north of the edge of the Miocene Molasse Basin (SW Germany)  

Microsoft Academic Search

Miocene carbonates intercalated in a deposit of Upper Freshwater Molasse (Middle Miocene), exposed in a limestone quarry at Heidenheim-Mergelstetten (Germany), were analysed geochemically and micromorphologically. The heavy minerals (fine sand) and clay minerals confirm the sedimentary interpretation of the formation as a sequence of Paleogene soil residues overlain by younger Neogene soil horizons developed in sediments of the Upper Freshwater

Peter Kallis; Klaus E Bleich; Karl Stahr

2000-01-01

378

Exceptionally preserved lacustrine ostracods from the Middle Miocene of Antarctica: implications for high-latitude palaeoenvironment at 77? south  

PubMed Central

A newly discovered Konservat-Lagerstätte from the Middle Miocene of the western Olympus Range, Dry Valleys, Antarctica, yields cypridoidean ostracods complete with preserved body and appendages. This is the first record of three-dimensionally fossilized animal soft tissues from the continent. The ostracods are preserved in goethite, secondary after pyrite, representing a novel mode of exceptional preservation. They signal a high-latitude (greater than 77°?south) lake setting (Palaeolake Boreas) viable for benthic animal colonization prior to 14?Myr ago. Their presence supports the notion of warmer, tundra-like environmental conditions persisting in the Dry Valleys until the Middle Miocene.

Williams, Mark; Siveter, David J; Ashworth, Allan C; Wilby, Philip R; Horne, David J; Lewis, Adam R; Marchant, David R

2008-01-01

379

Pre-Miocene extension within the Southern Snake Range: insights from preliminary mapping of the Red Ledges Quadrangle, NV  

NASA Astrophysics Data System (ADS)

Displacement on the Southern Snake Range décollement (SSRD) must have initiated prior to the Miocene based on the presence of an Oligocene, or older, clastic unit deposited on the upper plate of the décollement that contains clasts derived from the footwall of the SSRD (Miller et al., 1999). However, the timing of displacement on the SSRD prior to the Miocene is poorly constrained by current data. We calculated 2-9 km of extension along the SSRD prior to the Miocene based on data from McGrew (1993) and Miller et al. (1999). An integrated sedimentological, structural, and thermochronologic investigation of the upper plate clastic units is in progress to determine the link between these deposits and movement along the SSRD prior to the Miocene. New geologic mapping at the 1:24,000 scale of the Red Ledges Quadrangle located in the southern portion of the Southern Snake Range (SSR) is also ongoing to determine if brittle structures within the hanging wall of the SSRD were active prior to the Miocene. Our geologic mapping identified a west-dipping normal fault, herein named the Red Ledges Fault, in the hanging wall of the SSRD. This fault cut and tilted volcanic deposits we correlate to the Cottonwood Wash Tuff, the Wah Wah Springs Formation, and the Lund Formation based on a comparison of our calculated phenocryst modal percentages and previously published data (Best et al., 1989). The youngest identified tuff cut and rotated by the Red Ledges Fault, the Lund Formation, was deposited at ~27.9 Ma (Best et al., 1989). Radiometric dating of an unidentified ash flow tuff exposed in the area is in progress, and may better constrain the timing of motion along the fault. These new data will hopefully constrain any pre-Miocene extension along the Red Ledges Fault within the hanging wall of SSRD. Other future work to constrain a pre-Miocene period of extension within the SSR will include low-temperature thermochronometric analysis of granitic clasts within the upper plate conglomerate, and of samples from an intrusion exposed in the footwall of the SSRD. Ultimately, results from this ongoing study will contribute to our understanding of pre-Miocene extension within the northern Basin and Range Province.

Evans, S.; Hanson, A.; Sefein, K.

2012-12-01

380

Post-Miocene diagenetic and eustatic history of Enewetak Atoll: Model and data comparison  

SciTech Connect

The post-Miocene diagenetic and eustatic history of Enewetak Atoll was investigated using a one-dimensional forward model. Comparison of model and data suggests that the post-Miocene history of Enewetak Atoll was dominated by multiple episodes of meteoric phreatic diagenesis attendant with high-frequency (10{sup 4} to 10{sup 5} yr) fluctuations in sea level and a subsidence rate of 39.0 m/m.y. Sensitivity testing indicates that subaerial erosion results in the preservation of additional subaerial unconformities because stratigraphic shortening permits a succeeding sea-level rise to flood the exposure surface and deposit sediment, whereas without subaerial erosion this sea-level rise would be recorded as a paleophreatic lens. Model results indicate that less then 10% of lapsed time is recorded by sediment deposition during periods of high-frequency changes in sea level. Incompleteness of the stratigraphic record suggest that magnetostratigraphy may give erroneous ages for shallow-marine carbonate sequences deposited during times of high-frequency changes in sea level and frequent magnetic polarity reversals.

Quinn, T.M.; Matthews, R.K. (Brown Univ., Providence, RI (USA))

1990-10-01

381

Sedimentology and diagenesis of Miocene Lirio Limestone, Isla de Mona, Puerto Rico  

SciTech Connect

Isla de Mona is a carbonate plateau, 50 mi west of Puerto Rico. The island lies on the southern portion of the Mona Platform. It is composed mostly of two Miocene carbonate units: Isla de Mona Dolomite overlain by Lirio Limestone. The Lirio Limestone was deposited on a sloping erosional surface over the Isla de Mona Dolomite. The Miocene Lirio Limestone consists mostly of backreef sands (packstones) with a reefal sequence (boundstones and grainstones) present in the southwestern portion of the island. The reefal sequence is made up mostly of Stylophora, Porites, and Millepora. Thin, discreet pockets of carbonate mud, rich in planktonic foraminifera and radiolarians and mixed with shallow benthic fauna/flora (foraminifera, echinoderms, red algae, and corals) interpreted as storm deposits, are found throughout the unit. An extensive reefal zone can be inferred to be present throughout the southwestern to southern portions of the Mona Platform. The Lirio Limestone is heavily karstified and is riddled with sinkholes on the plateau surfaces and caves around the periphery of the island. Caves are exposed around the periphery of the island, radiating from a depression in the central portions of the Lirio Limestone, near contacts with the Isla de Mona Dolomite, are partially dolomitized. The southwestern outcrops exhibit partial dolomitization throughout. The distribution of sinkholes, seaward caverns, and partial dolomitization of the lowermost Lirio Limestone suggests diagenetic modifications by meteoric fluids in central exposed portions of the island and by marine-meteoric fluids in the lowermost portions of the phreatic lens.

Ruiz, H.; Gonzalez, L.A.; Budd, A.F. (Univ. of Iowa, Iowa City (United States))

1991-03-01

382

The early Miocene onset of a ventilated circulation regime in the Arctic Ocean.  

PubMed

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

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

383

Migration of sharks into freshwater systems during the Miocene and implications for Alpine paleoelevation  

NASA Astrophysics Data System (ADS)

Trace-element and isotopic compositions of fossilized shark teeth sampled from Miocene marine sediments of the north Alpine Molasse Basin, the Vienna Basin, and the Pannonian Basin generally show evidence of formation in a marine environment under conditions geochemically equivalent to the open ocean. In contrast, two of eight shark teeth from the Swiss Upper Marine Molasse locality of La Molière have extremely low ?18O values (10.3‰ and 11.3‰) and low 87Sr/86Sr ratios (0.707840 and 0.707812) compared to other teeth from this locality (21.1‰ 22.4‰ and 0.708421 0.708630). The rare earth element (REE) abundances and patterns from La Molière not only differ between dentine and enameloid of the same tooth, but also between different teeth, supporting variable conditions of diagenesis at this site. However, the REE patterns of enameloid from the “exotic” teeth analyzed for O and Sr isotopic compositions are similar to those of teeth that have O and Sr isotopic compositions typical of a marine setting at this site. Collectively, this suggests that the two “exotic” teeth were formed while the sharks frequented a freshwater environment with very low 18O-content and Sr isotopic composition controlled by Mesozoic calcareous rocks. This is consistent with a paleogeography of high-elevation (˜2300 m) Miocene Alps adjacent to a marginal sea.

Kocsis, László; Vennemann, Torsten W.; Fontignie, Denis

2007-05-01

384

New species of Agriotherium (Mammalia, Carnivora) from the late Miocene to early Pliocene of central Myanmar  

NASA Astrophysics Data System (ADS)

Here we describe a new species of giant short-faced fossil bears, Agriotheriummyanmarensis sp. nov. (Ursidae, Carnivora), from the latest Miocene to early Pliocene Irrawaddy sediments in the Chaingzauk area, central Myanmar. A. myanmarensis has a short mandible and a deep premasseteric fossa, both of which are the typical feature of Agriotherium. There are two specimens discovered so far: in the type specimen the inferior border of the mandibular corpus is rectilinearly-shaped, the m1 talonid is rather reduced, m1 metaconid larger than the entoconid-entoconulid ridge, the diastema between canine and p4 is very short, and the postcanine teeth are so reduced that existing cheek teeth are very crowded. Agriotherium had been widely distributed from the late Miocene through Pleistocene in Europe, East Asia (China), North America, and South Africa, but no fossil record has been reported from Southeast Asia. Except its extreme short snout, A. myanmarensis is most similar to that of the European form, Agriotheriuminsigne, rather than to the Asian species from Siwalik or China, such as Agriotheriumpalaeindicus, Agriotheriumsivalensis, and Agriotheriuminexpetans, suggesting the phylogenetic closeness to the European rather than to the South/East Asian forms.

Ogino, Shintaro; Egi, Naoko; Zin-Maung-Maung-Thein; Thaung-Htike; Takai, Masanaru

2011-08-01

385

Development of Miocene-Pliocene reef trend, St. Croix, U. S. Virgin Islands  

SciTech Connect

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.

Gill, I.; Eby, D.E.; Hubbard, D.K.; Frost, S.H.

1988-01-01

386

Biostratigraphic sequence analysis of Oligocene-Lower Miocene sections in the Orocual Field, Eastern Venezuela Basin  

SciTech Connect

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.