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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

Hawthorn  

MedlinePLUS

... or small tree of the rose family. The species of hawthorn discussed here are native to northern ... include upset stomach, headache, and dizziness. Although drug interactions with hawthorn have not been thoroughly studied, there ...

4

Hawthorne  

Microsoft Academic Search

The Relay Assembly Test Room study in the famous research that produced the Hawthorne effect can be regarded as an early OBM experiment. As was shown in reexamination and analysis more than four decades later, it involved both monetary reinforcement and discriminative feedback and had numerous points in common with contemporary OBM investigations. From that restudy have been derived some

H. McIlvaine Parsons

1991-01-01

5

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

6

Work Groups: From the Hawthorne Studies to Work Teams of the 1990s and Beyond  

Microsoft Academic Search

This article summarizes the Hawthorne studies related to work groups and their legacy and traces applications of work groups and related empirical research through the 1990s. A selective review of empirical studies of work group effectiveness conducted in work settings and published in the last 20 years addresses 4 questions: (a) What identifying features have field researchers used in operationally

Eric Sundstrom; Michael McIntyre; Terry Halfhill; Heather Richards

2000-01-01

7

Detailed geochemical and mineralogical analyses of naturally occurring arsenic in the Hawthorn Group  

Microsoft Academic Search

In order to understand the mineralogical association and distribution of arsenic (As) in the Hawthorn Group in central Florida, I examined in detail the chemical and mineralogical composition of 361 samples that were collected from 16 cores. Geochemical analyses were performed by hydride generation - atomic fluorescence spectrometry (HG-AFS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The identification of

Olesya Lazareva

2004-01-01

8

Hawthorn M1330  

Microsoft Academic Search

Clinical trials in Europe suggest that to be effective Hawthorn leaf and flower extract should contain substantial levels of the important plant constituents: flavonoids and catechin polymers, also known as oligomeric procyanidins (OPCs). In these trials, Hawthorn leaf and flower extract was used to support cardiovascular health. 1,2 Extracts of herbs may be 'standardized' - this means they must contain

Hawthorn M

9

Interpreting Hawthorne: Subjectivity in Biography  

Microsoft Academic Search

:In observing the attentive processes by which I reached interpretations of Nathaniel Hawthorne's life and fiction, I found surprising congruence between Hawthorne's identity themes and my own. Properly tempered psychoanalytic interpretative techniques such as \\

Gloria C. Erlich

1989-01-01

10

Interpreting Hawthorne: Subjectivity in Biography  

Microsoft Academic Search

In observing the attentive processes by which I reached interpretations of Nathaniel Hawthorne's life and fiction, I found surprising congruence between Hawthorne's identity themes and my own. Properly tempered psychoanalytic interpretative techniques such as \\

Gloria C. Erlich

1989-01-01

11

Hawthorne and War  

Microsoft Academic Search

Of the classic antebellum authors who lived to write about the Civil War, none was so artistically disabled by it as Nathaniel Hawthorne. Turning from his biting satire Chiefly About War-Matters to compose a new romance, he struggled with it until he died, no longer capable of beautifying and idealizing our rude, material life.

Randall Fuller

2007-01-01

12

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.

13

Depositional environments and paleogeography of the Upper Miocene Wassuk Group, west-central Nevada  

USGS Publications Warehouse

Fluvial and lacustrine deposits of the Miocene Wassuk Group, exposed in Coal Valley, west-central Nevada, are divided into five lithofacies: (1) diatomite, claystone, siltstone, and carbonaceous siltstone deposited in a lake with paludal conditions at the margin; (2) upward-coarsening sequences of sandstone deposited on a delta and fan-delta; (3) channel-form sandstone deposited on a distal braided alluvial plain; (4) clast-supported conglomerate deposited on a proxial braided alluvial plain or distal alluvial fan; and (5) matrix-supported conglomerate deposited on a distal to middle alluvial fan. Petrographic analysis records an upsection change from a predominantly andesitic to a predominantly plutonic provenance. This change, combined with the overall upward-coarsening of the Wassuk Group and the great thickness (2400 m) of the sequence, suggests active uplift and rapid subsidence during deposition of the group. Facies relationships and paleocurrent directions indicate source areas to the south, southeast and west of Coal Valley. The Miocene Wassuk Group was deposited in an intra-arc basin with penecontemporaneous volcanism and tectonic activity. Syndepositional faulting at the southern margin of Coal Valley between 13 and 11 m.y. ago suggests an early episode of northeast-southwest extension prior to the onset of east-west basin and range extension. ?? 1984.

Golia, R. T.; Stewart, J. H.

1984-01-01

14

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

15

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

16

What Caused the Hawthorne Effect?  

ERIC Educational Resources Information Center

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

Parsons, H. McIlvaine

1978-01-01

17

Diagenetic history of the Surma Group sandstones (Miocene) in the Surma Basin, Bangladesh  

NASA Astrophysics Data System (ADS)

This study examines the various diagenetic controls of the Miocene Surma Group sandstones encountered in petroleum exploration wells from the Surma Basin, which is situated in the northeastern part of the Bengal Basin, Bangladesh. The principal diagenetic minerals/cements in the Surma Group sandstones are Fe-carbonates (with Fe-calcite dominating), quartz overgrowths and authigenic clays (predominantly chlorite, illite-smectite and minor kaolin). The isotopic composition of the carbonate cement revealed a narrow range of ?18O values (-10.3‰ to -12.4‰) and a wide range of ?13C value (+1.4‰ to -23.1‰). The ?13C VPDB and ?18O VPDB values of the carbonate cements reveal that carbon was most likely derived from the thermal maturation of organic matter during burial, as well as from the dissolution of isolated carbonate clasts and precipitated from mixed marine-meteoric pore waters. The relationship between the intergranular volume (IGV) versus cement volume indicates that compaction played a more significant role than cementation in destroying the primary porosity. However, cementation also played a major role in drastically reducing porosity and permeability in sandstones with poikilotopic, pore-filling blocky cements formed in early to intermediate and deep burial areas. In addition to Fe-carbonate cements, various clay minerals including illite-smectite and chlorite occur as pore-filling and pore-lining authigenic phases. Significant secondary porosity has been generated at depths from 2500 m to 4728 m. The best reservoir rocks found at depths of 2500-3300 m are well sorted, relatively coarse grained; more loosely packed and better rounded sandstones having good porosities (20-30%) and high permeabilities (12-6000 mD). These good quality reservoir rocks are, however, not uniformly distributed and can be considered to be compartmentalized as a result of interbedding with sandstone layers of low to moderate porosities, low permeabilities owing to poor sorting and extensive compaction and cementation.

Rahman, M. Julleh Jalalur; McCann, Tom

2012-02-01

18

Lowell on Hawthorne: A Summary Exercise.  

ERIC Educational Resources Information Center

Because Robert Lowell's poem "Hawthorne" focuses on Puritan New England, both as a setting and a subject, and shows the dark side of human nature, and Hawthorne as the alienated artist with a definite place in American literature, it is a most appropriate conclusion for a teaching unit on Hawthorne.

Fanning, Charles

1977-01-01

19

More on the Hawthorne effect  

Microsoft Academic Search

Comments on D. Bramel and R. Friend’s interpretations of the Hawthorne studies of industrial workers and their criticisms of the subsequent work by E. Mayo and G. F. Lombard (1943). It is argued that Bramel and Friend were as selective in their criticisms as they accused F. J. Roethlisberger and W. J. Dickson (1939) of being in their interpretations of

H. McIlvaine Parsons

1982-01-01

20

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

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

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

21

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

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

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

22

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

Microsoft Academic Search

The newly recognized Whiteclay Gravel Beds (WGB) of the Miocene Ogallala Group crop out as a narrow, discontinuous ribbon of sands and gravels in Dawes and Sheridan Counties, northwestern Nebraska, USA. The WGB are exposed in a series of municipal gravel quarries and natural exposures that define a linear trench in underlying strata at least 20 m deep and up to

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

2007-01-01

23

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

Microsoft Academic Search

The newly recognized Whiteclay Gravel Beds (WGB) of the Miocene Ogallala Group crop out as a narrow, discontinuous ribbon of sands and gravels in Dawes and Sheridan Counties, northwestern Nebraska, USA. The WGB are exposed in a series of municipal gravel quarries and natural exposures that define a linear trench in underlying strata at least 20 m deep and up

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

2007-01-01

24

Mitigating the Hawthorne Effect Using Computer Simulations  

Microsoft Academic Search

\\u000a The Hawthorne studies by Roethlisberger and Dickson (1939) that investigated workplace behavior have maintained a consistent\\u000a presence in social science and education research literature (Chiesa & Hobbs, 2008). The Hawthorne Effect has been often noted\\u000a in social experiments describing participants modifying their behavior during the investigation because they know they are\\u000a being studied (G. Payne & J. Payne, 2004). This

Shawn Y. Holmes

25

Isotopic constraints on the genesis and age of autochthonous glaucony in the Oligo-Miocene Torquay Group, south-eastern Australia  

Microsoft Academic Search

The Oligo-Miocene Torquay Group at Bird Rock in south-eastern Australia comprises a sequence of fine-grained skeletal carbonates and argillaceous and glauconitic sandstones, deposited in a cool-water, mid-shelf environment. The Bird Rock glaucony is autochthonous and consists predominantly of randomly interstratified glauconitic smectite, which constitutes bioclast infills and faecal pellet replacements. The results of Rb-Sr and oxygen isotopic analysis of samples

JONATHAN C. K ELLY; JOHN A. W EBB; R OLAND M AAS

2001-01-01

26

Interaction study between digoxin and a preparation of hawthorn (Crataegus oxyacantha).  

PubMed

Hawthorn, an herbal supplement, is currently being evaluated for the treatment of heart failure. The flavonoid components of hawthorn may be responsible for hawthorn's beneficial effects in the treatment of heart failure. However, these components may also affect P-glycoprotein function and cause interactions with drugs that are P-glycoprotein substrates, such as digoxin, which is also used to treat heart failure. Therefore, the purpose of this study was to determine the effect of hawthorn on digoxin pharmacokinetic parameters. A randomized, crossover trial with 8 healthy volunteers was performed evaluating digoxin 0.25 mg alone (D) for 10 days and digoxin 0.25 mg with Crataegus special extract WS 1442 (hawthorn leaves with flowers; Dr. Willmar Schwabe Pharmaceuticals) 450 mg twice daily (D + H) for 21 days. Pharmacokinetic studies were performed for 72 hours. There were no statistically significant differences in any measured pharmacokinetic parameters. The AUC0-infinity, Cmax-Cmin, Cmin, and renal clearance for the D group were 79 +/- 26 mcg.h/L, 1.4 +/- 0.7 mcg/L, 0.84 +/- 0.2 mcg/L, and 74 +/- 10 mL/min versus 73 +/- 20 mcg.h/L, 1.1 +/- 0.1 mcg/L, 0.65 +/- 0.2 mcg/L, and 81 +/- 22 mL/min for the D + H group, respectively (p > 0.05). Following 3 weeks of concomitant therapy, hawthorn did not significantly alter the pharmacokinetic parameters for digoxin. This suggests that both hawthorn and digoxin, in the doses and dosage form studied, may be coadministered safely. PMID:12817526

Tankanow, Roberta; Tamer, Helen R; Streetman, Daniel S; Smith, Scott G; Welton, Janice L; Annesley, Thomas; Aaronson, Keith D; Bleske, Barry E

2003-06-01

27

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

NASA Astrophysics Data System (ADS)

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

Winkler, Dale A.

1987-08-01

28

Hypotensive effects of hawthorn for patients with diabetes taking prescription drugs: a randomised controlled trial  

PubMed Central

Background Hawthorn (Crataegus laevigata) leaves, flowers and berries are used by herbal practitioners in the UK to treat hypertension in conjunction with prescribed drugs. Small-scale human studies support this approach. Aim To investigate the effects of hawthorn for hypertension in patients with type 2 diabetes taking prescribed drugs. Design of study Randomised controlled trial. Setting General practices in Reading, UK. Method Patients with type 2 diabetes (n = 79) were randomised to daily 1200 mg hawthorn extract (n = 39) or placebo (n = 40) for 16 weeks. At baseline and outcome a wellbeing questionnaire was completed and blood pressure and fasting blood samples taken. A food frequency questionnaire estimated nutrient intake. Results Hypotensive drugs were used by 71% of the study population with a mean intake of 4.4 hypoglycaemic and/or hypotensive drugs. Fat intake was lower and sugar intake higher than recommendations, and low micronutrient intake was prevalent. There was a significant group difference in mean diastolic blood pressure reductions (P = 0.035): the hawthorn group showed greater reductions (baseline: 85.6 mmHg, 95% confidence interval [CI] = 83.3 to 87.8; outcome: 83.0 mmHg, 95% CI = 80.5 to 85.7) than the placebo group (baseline: 84.5 mmHg, 95% CI = 82 to 87; outcome: 85.0 mmHg, 95% CI = 82.2 to 87.8). There was no group difference in systolic blood pressure reduction from baseline (3.6 and 0.8 mmHg for hawthorn and placebo groups, respectively; P = 0.329). Although mean fat intake met current recommendations, mean sugar intake was higher and there were indications of potential multiple micronutrient deficiencies. No herb–drug interaction was found and minor health complaints were reduced from baseline in both groups. Conclusions This is the first randomised controlled trial to demonstrate a hypotensive effect of hawthorn in patients with diabetes taking medication.

Walker, Ann F; Marakis, Georgios; Simpson, Eleanor; Hope, Jessica L; Robinson, Paul A; Hassanein, Mohamed; Simpson, Hugh CR

2006-01-01

29

The Hawthorne effect: A reconsideration of the methodological artifact  

Microsoft Academic Search

Reviews the literature on the Hawthorne effect (HE) which originated out of the studies at the Hawthorne Works of the Western Electric Company. This effect is generally defined as the problem in field experiments that Ss' knowledge that they are in an experiment modifies their behavior from what it would have been without the knowledge. An examination of the Hawthorne

John G. Adair

1984-01-01

30

Composition and health effects of phenolic compounds in hawthorn (Crataegus spp.) of different origins.  

PubMed

Epicatechin, aglycons and glycosides of B-type oligomeric procyanidins and flavonols, phenolic acids and C-glycosyl flavones are the major groups of phenolic compounds in hawthorn (Crataegus spp). The total content of phenolic compounds is higher in the leaves and flowers than in the fruits. Procyanidins dominate in the fruits, whereas flavonol glycosides and C-glycosyl flavones are most abundant in the leaves. Genotype and developmental/ripening stage have strong impacts. Procyanidin glycosides and C-glycosyl flavones may be chemotaxonomic markers differentiating species and varieties of hawthorn. Future research shall improve the separation, identification and quantification of procyanidins with degree of polymerisation (DP) ? 6, procyanidin glycosides, C-glycosyl flavones and some flavonol glycosides. In vitro and animal studies have shown cardioprotective, hypolipidaemic, hypotensive, antioxidant, radical-scavenging and anti-inflammatory potentials of hawthorn extracts, suggesting different phenolic compounds as the major bioactive components. However, the varying and insufficiently defined composition of the extracts investigated, as a result of different raw materials and extraction methods, makes comparison of the studies very difficult. Clinical evidence indicates that some hawthorn extracts may increase the exercise tolerance of patients with congestive heart failure. More clinical studies are needed to establish the effects of hawthorn, especially in healthy humans. PMID:22488722

Yang, Baoru; Liu, Pengzhan

2012-04-04

31

The Hawthorne effect and energy awareness.  

PubMed

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

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

2013-09-03

32

The Hawthorne legacy : A reassessment of the impact of the Hawthorne studies on management scholarship, 1930-1958  

Microsoft Academic Search

Purpose – This paper seeks to analyze the contribution that the Hawthorne studies made to the discipline of management. The recent scholarly trend has been to attack the Hawthorne studies on the grounds of methodology and originality. However, the only way to accurately view the Hawthorne studies is to recreate the intellectual environment in which the studies were conducted. Why

Jeffrey Muldoon

2012-01-01

33

Tsuga shimokawaensis , a new species of permineralized conifer leaves from the Middle Miocene Shimokawa Group, Hokkaido, Japan  

Microsoft Academic Search

Silicified pinaceous leaves from the late Middle Miocene bed of Shimokawa Town, central Hokkaido, Japan are described asTsuga shimokawaensis sp. nov. Comparisons with leaves of extant species ofTsuga show that the new species is assigned to sect.Tsuga, resembling the extant speciesT. heterophylla in having usually one-cell-layered hypodermis, andT. sieboldii in having mesophyll cells between the resin canal and the hypodermis.

Midori Matsumoto; Takeshi Ohsawa; Makoto Nishida

1995-01-01

34

Hawthorne Elementary School: The Teachers' Perspective.  

ERIC Educational Resources Information Center

|Describes the Hawthorne Elementary School (Houston, Texas) reform efforts that targeted inner-city, low-income student academic improvement. The forceful use of national and local resources to implement teacher-initiated changes and to further a successful site-based school restructuring is presented. (GR)|

Mentzer, Debra; Shaughnessy, Tricia

1996-01-01

35

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

PubMed

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. PMID:23690849

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

2013-04-16

36

Archeological Overview and Management Plan for the Hawthorne Army Ammunition Plant, Hawthorne, California,  

National Technical Information Service (NTIS)

The Hawthorne Army Ammunition Plant (HWAAP) is situated in the Walker Lake Basin in the western portion of the Great Basin prehistoric culture area which has a suggested time sequence of about 12,000 years. Archeological research on the HWAAP has been lar...

J. H. Cleland D. Johnson C. M. Woods E. C. Johnson J. C. Smith

1987-01-01

37

Michael Anesko - Is James's Hawthorne Really James's Hawthorne? - The Henry James Review 29:1  

Microsoft Academic Search

Henry James's critical biography Hawthorne (1879) has long has since achieved canonical status among students of American literature. Precisely because James's biography has secured that stature, however, it seems surprising that scholars have failed to subject the author's methods and sources to more careful scrutiny. Closer analysis will suggest that James was, if not an outright plagiarist, then at the

Michael Anesko

2008-01-01

38

Hawthorn ( Crataegus spp.) fruit: some physical and chemical properties  

Microsoft Academic Search

The hawthorn (Crataegus spp.) fruits were analysed for some physical (dimensions, geometric mean diameter, sphericity, bulk density, fruit density, volume, terminal velocity, hardness and porosity) and chemical (moisture, crude protein, crude oil, crude energy, crude fiber, ash, pH, acidity, water- and alcohol soluble extract) properties. Mineral content of wild hawthorn growing in Turkey were determined by Inductively Coupled Plasma Atomic

Musa Özcan; Haydar Hac?sefero?ullar?; Tamer Marako?lu; Derya Arslan

2005-01-01

39

What Caused the Hawthorne Effect?A Scientific Detective Story  

Microsoft Academic Search

The studies that produced the Hawthorne effect have been the biggest Rorschach blot in behavioral and social science. Commentators read into them their own identifications of the confounding variable that caused a progressive rise in worker's production rates. But the clues to the real perpetrator of the Hawthorne effect were there all the time. Scientific detective work has yielded hard

H. M

1978-01-01

40

Effects on hawthorn the year after simulated spray drift  

Microsoft Academic Search

This paper describes the effect of a herbicide applied at levels consistent with off target movement on hawthorn the year following exposure. In the experiment, metsulfuron-methyl was applied in five dosages to individual trees in seven different hawthorn hedgerows. Spraying was conducted both at the bud stage and at the early flowering. Five endpoints (i.e. leaves, buds, flowers, green berries

Christian Kjær; Morten Strandberg; Mogens Erlandsen

2006-01-01

41

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

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

42

Intestinal absorption of hawthorn flavonoids – in vitro, in situ and in vivo correlations  

Microsoft Academic Search

Our previous studies identified hyperoside (HP), isoquercitrin (IQ) and epicatechin (EC) to be the major active flavonoid components of the hawthorn phenolic extract from hawthorn fruits demonstrating inhibitory effect on in vitro Cu+2-mediated low density lipoproteins oxidation. Among these three hawthorn flavonoids, EC was the only one detectable in plasma after the oral administration of hawthorn phenolic extract to rats.

Zhong Zuo; Li Zhang; Limin Zhou; Qi Chang; Moses Chow

2006-01-01

43

Energy Engineering Analysis Program, Energy Survey of Army Industrial Facilities, Western Area Demilitarization Facility Hawthorne Army Ammunition Plant Hawthorne, Nevada. Volume 1.  

National Technical Information Service (NTIS)

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, authori...

1995-01-01

44

Energy Engineering Analysis Program, Energy Survey of Army Industrial Facilities, Western Area Demilitarization Facility, Hawthorne Army Ammunition Plant, Hawthorne, Nevada; Volume 1 - Energy Report.  

National Technical Information Service (NTIS)

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, authori...

1995-01-01

45

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

PubMed

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

Loughman, C

1992-12-01

46

Energy Engineering Analysis Program, Limited Energy Study of Steam Distribution Systems, Hawthorne Army Ammunition Depot, Hawthorne, Nevada.  

National Technical Information Service (NTIS)

This report summarizes all work of the Limited Energy Study of Steam Distribution Systems, Energy Engineering Analysis Program, Hawthorne Army Ammunition Depot (HWAAD), Nevada. The purpose of this limited energy study is to evaluate steam distribution and...

1995-01-01

47

Effect of storage temperature on phenolics stability in hawthorn ( Crataegus pinnatifida var. major) fruits and a hawthorn drink  

Microsoft Academic Search

The stability of five major phenolics, namely (?)-epicatechin (EC), procyanidin B2 (PC-B2), chlorogenic acid (ChA), hyperoside (HP) and isoquercitrin (IQ), in hawthorn fruits and a canned hawthorn drink were evaluated during 6 months of storage in the dark at three different temperatures (4, 23 and 40°C). HPLC with a diode-array detector was used to determine the contents of the individual

Qi Chang; Zhong Zuo; Moses S. S. Chow; Walter K. K. Ho

2006-01-01

48

Postdepositional tilt of the Miocene-Pliocene Ogallala Group on the western Great Plains: Evidence of late Cenozoic uplift of the Rocky Mountains  

NASA Astrophysics Data System (ADS)

The Rocky Mountains and adjacent western Great Plains share a common history of late Cenozoic stream incision. Both epeirogenic uplift and climate change (with no associated uplift) have been proposed as the cause of this subcontinental-scale erosional episode. However, the lack of a well-defined Cenozoic paleoelevation history for the region has hampered our ability to distinguish between the two. A tilt analysis of the Cheyenne Tablelands in the western Great Plains of Wyoming and Nebraska provides us with a datum from which postdepositional changes in slope can be determined. Miocene to earliest Pliocene gravels of the Ogallala Group (17.5 5 Ma) cap the tablelands, which currently tilt down to the east at slopes as great as 10-2. However, paleohydraulic analysis of the Ogallala gravels indicates depositional slopes of 10-3 to 10-4, implying a postdepositional increase in tilt. If a hinge point at the eastern edge of the Cheyenne Tablelands is assumed, this tilt translates into differential uplift of 680 m (815 410 m) at the western edge of the Great Plains. Flexural isostatic rebound of the tablelands due to known young erosion in surrounding basins only produces a few hundred meters of uplift. Therefore, even if all of the recent erosion in the region can be attributed to climate change, the resulting rebound is insufficient to account for the observed uplift of the tablelands. Thus, the tilting of the Cheyenne Tablelands is most consistent with broad- wavelength tectonic uplift centered under the Rocky Mountains initiated during Ogallala deposition and continuing since deposition ceased.

McMillan, Margaret E.; Angevine, Charles L.; Heller, Paul L.

2002-01-01

49

American Studies in Review: The Recuperative Trend in Hawthorne Studies: New or Improved?  

Microsoft Academic Search

: This essay reviews two collections of essays (Hawthorne and the Real: Bicentennial Essays, edited by Millicent Bell, and The Cambridge Companion to Nathaniel Hawthorne, edited by Richard Millington) and Brenda Wineapple’s Hawthorne: A Life. These books raise questions about the currency of late-twentieth-century reassessments of Hawthorne’s significance: is “our” Hawthorne still to be read as an anxious conservative, tainted

Luke Bresky

2011-01-01

50

American Studies in Review: The Recuperative Trend in Hawthorne Studies: New or Improved?  

Microsoft Academic Search

This essay reviews two collections of essays (Hawthorne and the Real: Bicentennial Essays, edited by Millicent Bell, and The Cambridge Companion to Nathaniel Hawthorne, edited by Richard Millington) and Brenda Wineapple’s Hawthorne: A Life. These books raise questions about the currency of late-twentieth-century reassessments of Hawthorne’s significance: is “our” Hawthorne still to be read as an anxious conservative, tainted by

Luke Bresky

2011-01-01

51

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

Federal Register 2010, 2011, 2012, 2013

...proposes to revise Class D and E airspace at Jack Northrop Field/Hawthorne Municipal Airport...biennial review, along with a study of the Jack Northrop Field/Hawthorne Municipal Airport...an extension to Class D surface area at Jack Northrop Field/Hawthorne Municipal...

2011-10-31

52

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

Federal Register 2010, 2011, 2012, 2013

...revises Class D and Class E airspace at Jack Northrop Field/Hawthorne Municipal Airport...biennial review, along with a study of the Jack Northrop Field/Hawthorne Municipal Airport...an extension to Class D surface area at Jack Northrop Field/Hawthorne Municipal...

2012-02-13

53

Interaction Study between Digoxin and a Preparation of Hawthorn [Crataegus oxyacantha  

Microsoft Academic Search

Hawthorn, an herbal supplement, is currently being evaluated for the treatment of heart failure. The flavonoid components of hawthorn may be responsible for hawthorn's beneficial effects in the treatment of heart failure. However, these components may also affect P-glycoprotein function and cause interactions with drugs that are P-glycoprotein substrates, such as digoxin, which is also used to treat heart failure.

Roberta Tankanow; Helen R. Tamer; Daniel S. Streetman; Scott G. Smith; Janice L. Welton; Thomas Annesley; Keith D. Aaronson; Barry E. Bleske

2003-01-01

54

The structure and rate of late Miocene expansion of C4 plants: Evidence from lateral variation in stable isotopes in paleosols of the Siwalik Group, northern Pakistan  

Microsoft Academic Search

This study uses stable isotope variation within individual Mio-Pliocene paleosols to investigate subkilometer-scale phytogeog- raphy of late Miocene vegetation change in southeast Asia between ca. 8.1 and 5 Ma, a time interval that coincides with dramatic global vegetation change. We examine trends through time in the distribution of low-lati- tude grasses (C 4 plants) and forest (C 3 plants) on

Anna K. Behrensmeyer; Jay Quade; Thure E. Cerling; John Kappelman; Imran A. Khan; Peter Copeland; Lois Roe; Jason Hicks; Phoebe Stubblefield; Brian J. Willis; Claudio Latorre

2007-01-01

55

Identification of Host Fruit Volatiles from Hawthorn ( Crataegus spp.) Attractive to Hawthorn-Origin Rhagoletis pomonella Flies  

Microsoft Academic Search

Solid-phase microextraction (SPME) and gas chromatography coupled with electroantennographic detection (GC-EAD) were used to identify volatile compounds from hawthorn fruit (Crataegus spp.) acting as behavioral attractants for hawthorn-infesting Rhagoletis pomonella flies. Consistent EAD activity was obtained for six chemicals: ethyl acetate (94.3%), 3-methylbutan- 1-ol (4.0%), isoamyl acetate (1.5%), 4,8-dimethyl-1,3(E),7-nonatriene (0.07%), butyl hexanoate (0.01%), and dihydro-ß-ionone (0.10%). In a flight-tunnel bioassay,

Satoshi Nojima; Bruce Morris; Aijun Zhang; Wendell Roelofs

2003-01-01

56

Impact of the Hawthorne Effect in a Longitudinal Clinical Study  

Microsoft Academic Search

Clinical research can be influenced by many factors that are capable of invalidating results, and one of these factors is known as the Hawthorne effect: the mere awareness of being under observation can alter the way in which a person behaves. In experimental research this effect can be the undesired effect of the experiments themselves, and the stronger its presence,

Donatella De Amici; Catherine Klersy; Felice Ramajoli; Loretta Brustia; Pierluigi Politi

2000-01-01

57

Immunomodulatory effect of Hawthorn extract in an experimental stroke model  

PubMed Central

Background Recently, we reported a neuroprotective effect for Hawthorn (Crataegus oxyacantha) ethanolic extract in middle cerebral artery occlusion-(MCAO) induced stroke in rats. The present study sheds more light on the extract's mechanism of neuroprotection, especially its immunomodulatory effect. Methods After 15 days of treatment with Hawthorn extract [100 mg/kg, pretreatment (oral)], male Sprague Dawley rats underwent transient MCAO for 75 mins followed by reperfusion (either 3 or 24 hrs). We measured pro-inflammatory cytokines (IL-1?, TNF-?, IL-6), ICAM-1, IL-10 and pSTAT-3 expression in the brain by appropriate methods. We also looked at the cytotoxic T cell sub-population among leukocytes (FACS) and inflammatory cell activation and recruitment in brain (using a myeloperoxidase activity assay) after ischemia and reperfusion (I/R). Apoptosis (TUNEL), and Bcl-xL- and Foxp3- (Treg marker) positive cells in the ipsilateral hemisphere of the brain were analyzed separately using immunofluorescence. Results Our results indicate that occlusion followed by 3 hrs of reperfusion increased pro-inflammatory cytokine and ICAM-1 gene expressions in the ipsilateral hemisphere, and that Hawthorn pre-treatment significantly (p ? 0.01) lowered these levels. Furthermore, such pre-treatment was able to increase IL-10 levels and Foxp3-positive cells in brain after 24 hrs of reperfusion. The increase in cytotoxic T cell population in vehicle rats after 24 hrs of reperfusion was decreased by at least 40% with Hawthorn pretreatment. In addition, there was a decrease in inflammatory cell activation and infiltration in pretreated brain. Hawthorn pretreatment elevated pSTAT-3 levels in brain after I/R. We also observed an increase in Bcl-xL-positive cells, which in turn may have influenced the reduction in TUNEL-positive cells compared to vehicle-treated brain. Conclusions In summary, Hawthorn extract helped alleviate pro-inflammatory immune responses associated with I/R-induced injury, boosted IL-10 levels, and increased Foxp3-positive Tregs in the brain, which may have aided in suppression of activated inflammatory cells. Such treatment also minimizes apoptotic cell death by influencing STAT-3 phosphorylation and Bcl-xL expression in the brain. Taken together, the immunomodulatory effect of Hawthorn extract may play a critical role in the neuroprotection observed in this MCAO-induced stroke model.

2010-01-01

58

Energy Engineering Analysis Program, Limited Energy Study of Steam Distribution Systems, Hawthorne Army Ammunition Depot, Hawthorne, Nevada.  

National Technical Information Service (NTIS)

This report summarizes all work of the Limited Energy Study of Steam Distribution Systems, Energy Engineering Analysis Program, Hawthorne Army Ammunition Depot (HWAAD), Nevada. The project is authorized under Contract No. DACA05-92-C-0155 with the U.S. Ar...

1995-01-01

59

Energy Engineering Analysis Program, Limited Energy Study of Steam Distribution Systems, Hawthorne Army Ammunition Depot, Hawthorne, Nevada: Programming Documents.  

National Technical Information Service (NTIS)

The project is a significant part of Hawthorne Army Ammunition Depot's effort to achieve a 20-percent reduction in energy consumption by FY2000 versus FY1985 baseline levels. The project will also assure that heating services are provided to Industrial Ar...

1995-01-01

60

The Miocene Atlantic Ocean  

NASA Astrophysics Data System (ADS)

We model paleoclimate and ocean circulation during the Miocene climatic optimum (~17 ¬ 14.5 Ma) using the Community Climate System Model 3 (CCSM3), focussing particularly on the effect of Miocene model boundary conditions including reconstructed topography, bathymetry, and vegetation. The modelled Miocene climate exhibits broad increases in mean annual precipitation over central and northern Africa, northern Eurasia, northern North America and Greenland compared to the present. In northern Africa, summer precipitation is significantly higher in the Miocene due to the replacement of desert with broadleaf vegetation, consistent with previously published sensitivity studies. Our results qualitatively support interpretations of carbon and neodymium isotope records indicating NCW formation in the North Atlantic as well as a dominant bottom water source in the Southern Ocean. Major tectonic changes in our Miocene Atlantic bathymetry compared to the present day are the severe constriction of the Fram Strait, closure of the Panama Strait and the less elevated Greenland-Scotland Ridge. We find that the structure of ocean circulation in the Miocene Atlantic is somewhat opposite to the present day, with the primary region of Miocene bottom water formation in the Weddell Sea. The strength of Weddell Sea bottom water and North Component Water (NCW) formation are moderated by atmospheric CO2 levels, which suggests that very weak NCW formation could have existed under significantly higher concentrations than the present-day CO2 concentration used in our model. Such a state would be consistent with the hypothesis of negligible NCW formation in the early Miocene, suggested previously. In our model, the NCW is relatively warm and saline compared to modern North Atlantic Deep Water (NADW). This is likely a robust result, caused by a northward deflection of North Atlantic subtropical water below the mixed-layer, a weakening of the subpolar gyre and weaker convection, as opposed to warm Tethys outflow. An interesting model result concerns the importance of the geometry of reconstructed gateways. Regarding the Panama gateway we find only a small eastward throughflow, in contrast in contrast with other published estimates. The difference appears to be related to the exact orientation of the reconstructed gateway. A gateway oriented in a zonal direction results in a natural extension of the equatorial countercurrent, whereas a more meridionally oriented gateway, as in our reconstruction, largely prohibits such a current, emphasizing the effect of subtle model boundary conditions. A decreased northern hemisphere ocean heat transport in the Miocene compared to the present is a result of a significant weakening of North Atlantic Deep Water formation. Modelled flow into the Arctic Ocean is consistent with the idea of an enclosed estuarine sea. Coupled with a relatively deeper Greenland-Scotland Ridge it permits substantial Miocene ocean warming. Determining how this warming varied under changes in modelled bathymetry may elucidate ways in which near ice-free Arctic conditions were sustainable.

Müller, R. D.; Herold, N.; Huber, M.

2012-04-01

61

Miocene Coralline algae  

SciTech Connect

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

Bosence, D.W.J.

1988-01-01

62

Review of Miocene larger foraminifera  

SciTech Connect

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

Glenn, E.C.

1988-01-01

63

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

PubMed Central

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

Ford, Emily; Adams, Jon; Graves, Nicholas

2012-01-01

64

Hawthorn Fruit Is Hypolipidemic in Rabbits Fed a High Cholesterol Diet1  

Microsoft Academic Search

The present study examined the hypolipidemic activity of hawthorn fruit. New Zealand white rabbits were fed one of three diets, a reference diet with no cholesterol added (NC), a high cholesterol diet (1 g\\/100 g, HC) and a HC diet supplemented with 2 g\\/100 g hawthorn fruit powder (HC-H). After 12 wk, serum total cholesterol (TC) and triacylglycerols (TG) were

Zesheng Zhang; Walter K. K. Ho; Yu Huang; Anthony E. James; Lik Wang Lam; Zhen-Yu Chen

65

Metsulfuron spray drift reduces fruit yield of hawthorn ( Crataegus monogyna L.)  

Microsoft Academic Search

This study was carried out to investigate whether spray drift of metsulfuron has a potential to negatively affect hawthorn (Crataegus monogyna) hedgerows near agricultural fields. For this purpose four doses of metsulfuron ranging from 5% to 40% of the field dose (4 g metsulfuron per hectare) were sprayed on trees in seven different hawthorn hedgerows. The actual deposition on the

Christian Kjær; Morten Strandberg; Mogens Erlandsen

2006-01-01

66

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

67

Miocene reefs of Dominican Republic  

SciTech Connect

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

Evans, C.C.

1988-01-01

68

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

69

Fluvial systems in the Siwalik Miocene and Wyoming Paleogene  

Microsoft Academic Search

The 3 km thick Miocene Siwalik Group (Himalayan foredeep in northern Pakistan) and the 2 km thick Paleogene Fort Union\\/Willwood formations (Bighorn Basin in Wyoming) both preserve long records of fluvial deposition adjacent to rising mountain belts. Depositional environments and associated habitats change across large basins along with changing physiography and with the location of different river systems that may

B. J. Willis; A. K. Behrensmeyer

1995-01-01

70

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

71

Regulation of lipoprotein lipase expression by effect of hawthorn flavonoids on peroxisome proliferator response element pathway.  

PubMed

To investigate the possibility that natural medicines affect lipid metabolism by regulating lipoprotein lipase (LPL) expression, a green fluorescent protein (GFP) gene was constructed downstream of the peroxisome proliferator response element (PPRE) and the constructed plasmid was microinjected into Xenopus oocytes to establish a PPRE regulatory reporter system. Using this system, hawthorn flavonoids were quickly selected from a panel of natural medicines and found to up-regulate GFP expression by an effect on PPRE. To confirm the effect of hawthorn flavonoids, we treated mice orally with water (control), hawthorn flavonoids, and pioglitazone and measured the LPL levels in serum, adipose tissue, and muscle by an enzyme-linked immunosorbent assay. The serum LPL levels were no different from the controls after treatment with either hawthorn flavonoids or pioglitazone, but LPL increased significantly in muscular tissues and decreased in adipose tissues. These results demonstrate that hawthorn flavonoids meditate LPL expression in mice with tissue-specific differences. A novel PPRE regulatory report system was established for rapid and effective selection and evaluation of LPL-mediating drugs. PMID:16404131

Fan, Chunlei; Yan, Jin; Qian, Ying; Wo, Xingde; Gao, Liping

2006-01-11

72

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

73

Headspace solid-phase microextraction analysis of volatile compounds in hawthorn vinegars fermented by two strains of Acetobacter  

Microsoft Academic Search

Hawthorn (Crataegus oxyacantha), which is wildly distributed in northern China, has a long history as a medicinal substance, for the treatment of digestive ailments, dyspnea, kidney stones and cardiovascular disorders, etc. Today, it is currently used for the juice production and is used as the raw material for hawthorn wine and vinegar production. However, the flavor of fruit vinegars diversifies

Yu Zheng; Hongxiang Liu; Keping Zhang; Min Wang

2010-01-01

74

Effect of hawthorn ( Crataegus oxycantha) crude extract and chromatographic fractions on multiple activities in a cultured cardiomyocyte assay  

Microsoft Academic Search

Extracts of hawthorn (Crataegus oxycantha) have become popular herbal supplements for their well-recognized cardiotonic effects. Many commercial preparations have been used successfully in the treatment of congestive heart failure, although the active principles within these extracts have yet to be conclusively identified. Several hawthorn preparations were studied and found to have negative chronotropic effects in a cultured neonatal murine cardiomyocyte

S. R. Long; R. A. Carey; K. M. Crofoot; P. J. Proteau; T. M. Filtz

2006-01-01

75

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

PubMed

The apple maggot fly, Rhagoletis pomonella, infests apple (Malus domestica) and hawthorn species (most notably the downy hawthorn, Crataegus mollis) in the eastern USA. Evidence suggests that the fly was introduced into the western USA sometime in the last 60 years. In addition to apple, R. pomonella also infests two species of hawthorns in the western USA as major hosts: the native black hawthorn (C. douglasii) and the introduced ornamental English hawthorn, C. monogyna. Apple and downy hawthorn-origin flies in the eastern USA use volatile blends emitted from the surface of their respective ripening fruit to find and discriminate among host trees. To test whether the same is true for western flies, we used coupled gas chromatography and electroantennographic detection (GC-EAD) and developed a 7-component apple fruit blend for western apple-origin flies, an 8-component black hawthorn fruit blend for flies infesting C. douglasii, and a 9-component ornamental hawthorn blend for flies from C. monogyna. Crataegus douglasii and C. monogyna-origin flies showed similar levels of upwind directed flight to their respective natal synthetic fruit blends in flight tunnel assays compared to whole fruit adsorbent extracts, indicating that the blends contain all the behaviorally relevant fruit volatiles to induce maximal response levels. The black and ornamental hawthorn blends shared four compounds in common including 3-methylbutan-1-ol, which appears to be a key volatile for R. pomonella populations in the eastern, southern, and western USA that show a preference for fruit from different Crataegus species. However, the blends also differed from one another and from domesticated apple in several respects that make it possible that western R. pomonella flies behaviorally discriminate among fruit volatiles and form ecologically differentiated host races, as is the case for eastern apple and hawthorn flies. PMID:22399441

Cha, Dong H; Yee, Wee L; Goughnour, Robert B; Sim, Sheina B; Powell, Thomas H Q; Feder, Jeffrey L; Linn, Charles E

2012-03-08

76

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

2012-12-06

77

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

SciTech Connect

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

Weedman, S.D. (Pennsylvania State Univ., Univ. Park, PA (United States)); McCartan, L. (Geological Survey, Reston, VA (United States))

1993-03-01

78

Comparative protective effect of hawthorn berry hydroalcoholic extract, atorvastatin, and mesalamine on experimentally induced colitis in rats.  

PubMed

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. PMID:23875899

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

2013-07-01

79

Curtobacterium flaccumfaciens septic arthritis following puncture with a Coxspur Hawthorn thorn.  

PubMed

Curtobacterium species are recognized plant pathogens. We report the first well-documented case of Curtobacterium human infection, a child with septic arthritis following puncture with a Coxspur Hawthorn plant thorn. The organism isolated from synovial tissue and the plant thorn was identified as Curtobacterium flaccumfaciens by 16S rRNA gene sequence analysis. PMID:21562106

Francis, Michelle J; Doherty, Richard R; Patel, Minoo; Hamblin, John F; Ojaimi, Samar; Korman, Tony M

2011-05-11

80

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

81

Illuminating the history of psychology: tips for teaching students about the Hawthorne studies  

Microsoft Academic Search

Imagine that you are a student enrolled in a research methods or organisational psychology course. In your textbook you read that an important research project took place during the 1920s at the Hawthorne Works manufacturing plant in the mid-western US, where researchers attempted to investigate the effects of lighting levels on worker productivity. To the astonishment of researchers, worker performance

LINDSEY HOGAN; LINDSEY SANTOS

82

Hawthorne, the myth of the docile worker, and class bias in psychology  

Microsoft Academic Search

Contends that the experimental studies performed at the Hawthorne plant of Western Electric were fundamental for the development of human relations in industry. They have also been cited frequently in social psychology and research methodology. Despite the appearance over the years of a number of well-argued critiques, it is felt that many psychologists show an undeserved respect for the conclusions

Dana Bramel; Ronald Friend

1981-01-01

83

Miocene precursors to Great Barrier Reef  

Microsoft Academic Search

Huge reefs of Miocene age are present in the Gulf of Papua north of the present-day Great Barrier Reef and to the east on the Marion and Queensland Plateaus. In the Gulf of Papua, Miocene barrier reefs formed the northern forerunner of the Great Barrier Reef, extending for many hundreds of kilometers along the eastern and northern margin of the

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

1988-01-01

84

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

85

El Nino-like events during Miocene  

Microsoft Academic Search

El Nino-like events have been recorded from the Miocene laminated siliceous facies of the Monterey Formation. These El Nino-like Miocene events are compared to El Nino events recorded from Holocene varved sediments deposited within the anoxic Santa Barbara basin. Strong El Nino events can be recognized from Holocene Santa Barbara basin sediments by increases in radiolarian flux to the sea

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

1988-01-01

86

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

87

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

88

Differences in the electroantennal responses of apple- and hawthorn-infesting races of Rhagoletis pomonella to host fruit volatile compounds  

Microsoft Academic Search

Summary.   Domestic apple (Malus pumila)- and hawthorn (Crataegus sp.)-infesting races of Rhagoletis pomonella, Walsh (Diptera: Tephritidae) provide an excellent model to examine the role that host plant specificity plays during sympatric\\u000a speciation (i.e., divergence in the absence of geographic isolation). Previous work has shown that these races differ in their propensities\\u000a to accept apple and hawthorn fruits in behavioral choice

Jürg E. Frey; Jeffrey L. Feder; Joanne Palma; Guy L. Bush

1998-01-01

89

First diatomyid rodent from the Early Miocene of Arabia  

NASA Astrophysics Data System (ADS)

The Asian family Diatomyidae is known from the Early Oligocene to the present. Among living rodents, this group comprises only the recently discovered Laonastes aenigmamus from Laos. Fossil diatomyids are known from only a few sites, in which they are often rare. The discovery of Pierremus explorator gen. nov. sp. nov. in the Lower Miocene of As-Sarrar (Saudi Arabia) raises to ten the number of extinct diatomyid species recognized. Pierremus explorator is the first record of a diatomyid from the Afro-Arabian plate. This discovery provides evidence that, together with other rodents (ctenodactylids, zapodids…), the diatomyids took advantage of the corridor that was established between Afro-Arabia and Eurasia in Early Miocene times.

López-Antoñanzas, Raquel

2011-02-01

90

First diatomyid rodent from the Early Miocene of Arabia  

NASA Astrophysics Data System (ADS)

The Asian family Diatomyidae is known from the Early Oligocene to the present. Among living rodents, this group comprises only the recently discovered Laonastes aenigmamus from Laos. Fossil diatomyids are known from only a few sites, in which they are often rare. The discovery of Pierremus explorator gen. nov. sp. nov. in the Lower Miocene of As-Sarrar (Saudi Arabia) raises to ten the number of extinct diatomyid species recognized. Pierremus explorator is the first record of a diatomyid from the Afro-Arabian plate. This discovery provides evidence that, together with other rodents (ctenodactylids, zapodids…), the diatomyids took advantage of the corridor that was established between Afro-Arabia and Eurasia in Early Miocene times.

López-Antoñanzas, Raquel

2010-12-01

91

Phenylpropanoid-substituted procyanidins and tentatively identified procyanidin glycosides from hawthorn (Crataegus spp.).  

PubMed

The rational use of hawthorn leafs and flowers from Crataegus spp. for declining cardiac performance is mainly due to flavon-C-glycosides and oligomeric procyanidins (OPC). From OPC-enriched extracts from different batches, a dimeric phenylpropanoid-substituted procyanidin (cinchonain II?b, 1) was isolated and characterized by MS, CD, and NMR. Also the presence of higher oligomeric cinchonains (degree of polymerization 3 to 8) in hawthorn extracts was shown by a specific ultrahigh-pressure liquid chromatography-ESI-qTOF-MS method. Interestingly, strong evidence for the occurrence of oligomeric procyanidin hexosides was found by ultrahigh-pressure liquid chromatography-ESI-qTOF-MS analysis which additionally revealed the presence of peaks indicative of dimeric procyanidin hexosides by their exact mass, which were clearly distinguishable from the cinchonain II type peaks. PMID:23154843

Sendker, Jandirk; Petereit, Frank; Lautenschläger, Marcus; Hellenbrand, Nils; Hensel, Andreas

2012-11-15

92

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

93

Miocene stratigraphy and fossils, Cape Blanco, Oregon.  

USGS Publications Warehouse

A summary of the stratigraphic occurrence of the Miocene molluscan faunas exposed in marine sandstone seacliffs on the SW Oregon coast. The more common and biostratigraphically significant species are illustrated. - Philip Harris

Adicott, W. O.

1980-01-01

94

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

95

Modeling the Miocene climatic optimum: Ocean circulation  

NASA Astrophysics Data System (ADS)

Ocean circulation is investigated using the Community Climate System Model 3 (CCSM3) forced with early to middle Miocene (˜20-14 Ma) topography, bathymetry, vegetation and modern CO2. Significant bottom water formation is modeled in the Weddell Sea along with intermediate North Component Water formation in the North Atlantic. This is attributed primarily to stronger- and weaker-than-modern convective preconditioning in the Weddell and Labrador Seas, respectively. Global meridional overturning and gyre circulation is weaker in the Miocene due to weaker midlatitude westerlies in the southern hemisphere, caused by lowering of the meridional surface temperature gradient, in addition to regional influences on convection. Subsurface temperatures in the Miocene are significantly higher in the far North Atlantic, Greenland-Norwegian Seas and Arctic basin compared to the present. Ocean heat transport is symmetrical about the equator and resembles that simulated for late Cretaceous and early Cenozoic climates, suggesting the northern hemisphere dominated ocean heat transport active today developed after the middle Miocene. Simulated deep water warming in the Miocene is more than an order of magnitude lower than indicated by proxies. This discrepancy is not reconciled by higher CO2 due to the persistence of sea-ice at sites of deep water formation. This suggests that either the CCSM3 is insufficiently sensitive to Miocene boundary conditions, greater greenhouse forcing existed than is currently reconstructed, or that proxy records of warming are exaggerated. Given the diversity of global Miocene proxy records and their near-unanimous estimate of a significantly warmer Earth, the first two options are more likely.

Herold, N.; Huber, M.; Müller, R. D.; Seton, M.

2012-03-01

96

The late early Miocene Sabine River  

SciTech Connect

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

Manning, E. (Louisiana State Univ., Baton Rouge (USA))

1990-09-01

97

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

98

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

99

Prospective research in health service settings: health psychology, science and the 'Hawthorne' effect.  

PubMed

Health service providers sometimes express concern about the impact of prospective survey research upon patient behaviour. To date, there is little available evidence from which to estimate the likelihood of any 'Hawthorne' effect on patient behaviour in health service settings. We analysed data from one of our own surveys to investigate whether inviting people to participate in research had any impact on their subsequent uptake of a screening service. Findings showed that people sent a questionnaire were slightly faster to take up screening than those not sent a questionnaire. We obtained no significant difference in absolute service uptake rate at six months. PMID:15117535

O'Sullivan, Ian; Orbell, Sheina; Rakow, Tim; Parker, Ron

2004-05-01

100

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

101

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

PubMed

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. PMID:19203920

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

2009-01-20

102

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

103

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

104

Optimization of ultrasound-assisted extraction (UAE) of flavonoids compounds (FC) from hawthorn seed (HS).  

PubMed

Hawthorn seed (HS), an important by-product of the Hawthorn industry, is rich in potentially health-promoting flavonoids compounds. In this paper, the ultrasound-assisted extraction (UAE) of FC from HS was investigated. Important variables and their levels were obtained using Plackett-Burman (PB) design and Box-Behnken (BB) design. A mathematical model was developed to show the effects of each variable and their combinatorial interactions on extraction yield of FC. A high coefficient of determination (R(2) = 91.26%) indicated good agreement between the experimental and predicted values of FC yield. The optimum levels of these significant parameters were determined using response surface methodology (RSM), which revealed these as follows: ultrasound temperature 65 °C, ultrasonic time 37 min, extraction temperature 91 °C, extraction time 1.5h, solid-liquid ratio of 1:18, and 72% ethanol. Under the optimum condition, the UAE rate of FC was up to 91.7%, and the yield of FC was 16.45 ± 0.02 mg/g (P<0.05) that was 1.32-fold the yield of conventional reflux extraction (CRE). PMID:22142939

Pan, Guangyan; Yu, Guoyong; Zhu, Chuanhe; Qiao, Julin

2011-11-20

105

Late eocene to early Miocene vegetation and climate history of New Zealand  

Microsoft Academic Search

There were some major shifts in species dominance in the vegetation of the Late Eocene to Early Miocene in New Zealand. In the Middle Eocene (Bortonian) the vegetation was dominated by Casuarina and several species of Proteaceae. This association was replaced in the Late Eocene (Kaiatan) by one dominated by the Nothofagus fusca group, in which Casuarina was of minor

David T. Pocknall

1989-01-01

106

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

107

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

PubMed

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

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

2013-09-05

108

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

109

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

110

Paleomagnetism of Miocenic Rocks Around Chalcatzingo, Morelos, Mexico: A Revaluation  

NASA Astrophysics Data System (ADS)

The Chalcatzingo domes southeast of Mexico City have been recently 40Ar/39Ar dated to be around 20.7 Ma old. These rocks and the surrounding Tepexco Volcanic Group are defined in a previous study as showing strongly discordant paleomagnetic directions, about 50 west from the expected Miocene geomagnetic field direction; which prompted the hypothesis of a counter clockwise crustal block rotation, related to a regional left lateral fault system along the Transmexican Volcanic Belt. This rotation is the largest proposed so far for central Mexico, and it is in contrast to data from the nearby Basin of Mexico, which are concordant with the expected field directions. In view of the limited previous sampling and relatively complex remanence record, we have re-sampled the Chalcatzingo and Tepexco rocks to verify the validity of the proposed block rotation. For that purpose samples were collected from 26 sites. Reflected light and scanning electron microscopy were used to determine composition and texture of magnetic minerals, and IRM acquisition and thermomagnetic experiments to determine the rock magnetic properties. Detailed demagnetization was carried out using mainly the AF method to determine the characteristic remanence directions, to calculate site mean directions and VGPs. These are compared to the Miocene reference direction and pole for stable North America, and interpreted in terms of potential tectonic movements of the study area.

Vazquez-Duarte, A.; Bohnel, H.; Yutsis, V.

2009-05-01

111

Miocene reef carbonates of Mariana Islands  

Microsoft Academic Search

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

Siegrist; H. G. Jr

1988-01-01

112

Miocene reef carbonates of Mariana Islands  

Microsoft Academic Search

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

Siegrist; H. G. Jr

1988-01-01

113

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

2013-08-05

114

El Nino-like events during Miocene  

SciTech Connect

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

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

1988-03-01

115

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

116

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

117

Standardized extracts from hawthorn leaves and flowers in the treatment of cardiovascular disorders--preclinical and clinical studies.  

PubMed

Extracts from different parts of hawthorn plants (Crataegus spp.) are used worldwide for the treatment of cardiovascular diseases. So far, almost all clinical studies have been conducted with standardized hydroalcoholic extracts from leaves and flowers. These trials with more than 4000 patients have provided evidence for clinical benefits in the therapy of mild chronic heart failure. Besides cardiotonic effects, recent pharmacological investigations indicate that hawthorn extracts also possess cardio- and vasoprotective properties. Thus, these extracts may also be employed in the prophylactic and therapeutic treatment of such conditions as endothelial dysfunction, atherosclerosis, coronary heart disease, or prevention of restenosis/reocclusion following peripheral endovascular treatment. In this review the pharmacological and clinical data relating to these standardized extracts are summarized. PMID:21384315

Koch, Egon; Malek, Fathi Abdul

2011-03-07

118

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

PubMed

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. PMID:23451979

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

2012-01-01

119

Ventilation of the Miocene Arctic Ocean: An idealized model study  

Microsoft Academic Search

A model study of an idealized early Miocene Arctic Ocean has been undertaken. The work is motivated by the first drill core retrieved from the Lomonosov Ridge in the central Arctic Ocean, which suggests a transition from anoxic to oxic condition during the early Miocene, a feature presumably related to the opening of the Fram Strait. Here, the ventilation in

Bijoy Thompson; Johan Nilsson; Jonas Nycander; Martin Jakobsson; Kristofer Döös

2010-01-01

120

Late Miocene magnetostratigraphy, biostratigraphy and cyclostratigraphy in the Mediterranean  

Microsoft Academic Search

A new chronology for the late Miocene of the Mediterranean is presented by combining magnetostratigraphic, biostratigraphic (planktonic foraminifera and dinoflagellates) and cyclo-stratigraphic data. Long and continuous upper Miocene sections on Gavdos (Metochia section) and Sicily (Gibliscemi section) display cyclic alternations of homogeneous marls and sapropels and can be correlated on the basis of their distinct cyclic patterns. The Metochia section

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

1995-01-01

121

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

PubMed

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

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

2011-09-02

122

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

123

Integrated Sr-isotope and bio-chronology of Oligocene-Miocene sequences, onshore and offshore New Jersey  

NASA Astrophysics Data System (ADS)

Sr isotopes provide a valuable means for developing chronology in nearshore sediments where biostratigraphic markers are often lacking or suffer environmental exclusion. This approach is most precise when rates of change in seawater Sr-isotopes were high (e.g., Oligocene to early Miocene). Sr-isotope stratigraphy is potentially limited by carbonate diagenesis, reworking, and intervals of low resolution (e.g., later Miocene). Integration of Sr-isotopes and biostratigraphy provide a relatively precise chronology (better than 1 Myr resolution) in onshore and offshore New Jersey strata. We previously developed a chronology for onshore Oligocene-Miocene sequences and correlated them with sequences cored on the continental slope. IODP Expedition 313 cored three sites on the nearshore shallow shelf of New Jersey that link the onshore and offshore studies, focusing on thick lower to lower middle Miocene sections imaged on seismic profiles. At least four Oligocene sequences and one uppermost Eocene-lowermost Oligocene sequence occur at Site M27, where the Oligocene section is unusually thick (>129 m) compared to onshore. From youngest to oldest these are: 1) a sequence dated by bio- and Sr-isotope stratigraphy straddling the Oligocene/Miocene boundary; 2) a well-dated mid-Oligocene sequences with high sedimentation rate (~92 m/m.y.); 3) a poorly dated ca. 30 Ma sequence; 4) one or more lower Oligocene sequences; and 5) a basal Oligocene sequence boundary correlated with isotopic increase Oi1. Several early Miocene sequences are also well constrained: 1) sequence m5.8 is well dated at Site M27; 2) sequence 5.45 is dated at Sites M27 and M28; and 3) sequence m5.2 is well dated at Site M29. A series of relatively thin (<25 m) sequences (m5.3, m5.32, m5.4) span the lower/middle Miocene boundary (16.2 Ma). Preliminary ages for these sequences appear to be younger at Site M27 than at Sites M28 and M29, which we attribute to the early disappearance of taxa at this updip sandy site. Middle Miocene sequences are poorly dated by Sr isotopes due to reworking and low resolution, but diatom and other fossil groups indicate a major hiatus associated with sequence boundary m5 and imply extremely high sedimentation rates (>200 m/Myr) above this. This influx of sediments was associated with the major middle Miocene oxygen isotopic increases.

Browning, J. V.; Miller, K. G.; Sugarman, P.; Kulhanek, D. K.; Huang, B.; McCarthy, F. M.; Barron, J. A.; Scienceparty, E.

2010-12-01

124

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

125

Nanomechanics and sodium permeability of endothelial surface layer modulated by hawthorn extract WS 1442.  

PubMed

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. PMID:22253842

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

2012-01-10

126

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

127

Screening and structural characterization of alpha-glucosidase inhibitors from hawthorn leaf flavonoids extract by ultrafiltration LC-DAD-MS(n) and SORI-CID FTICR MS.  

PubMed

In vitro alpha-glucosidase inhibition assays and ultrafiltration liquid chromatography with photodiode array detection coupled to electrospray ionization tandem mass spectrometry (ultrafiltration LC-DAD-ESI-MS(n)) were combined to screen alpha-glucosidase inhibitors from hawthorn leaf flavonoids extract (HLFE). As a result, four compounds were identified as alpha-glucosidase inhibitors in the HLFE, and their structures were confirmed to be quercetin-3-O-rha- (1-4)-glc-rha and C-glycosylflavones (vitexin-2"-O-glucoside, vitexin-2"-O-rhamnoside and vitexin) by high-resolution sustained off resonance irradiation collision-induced dissociation (SORI-CID) data obtained by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). Several other C-glycosylflavones (vitexin, isovitexin, orientin, isooriention) and their aglycones apigenin and luteolin were evaluated by in vitro assays, and were found to possess strong alpha-glucosidase inhibitory activities as well. Moreover, the substituent groups on the flavones had a great impact on the enzyme inhibition activity. C-3'-OH of the B-ring of flavones in particular increased the alpha-glucosidase inhibition activity, whereas C-glycosylations at C-6 or C-8 of the A ring weakened the inhibition activity. PMID:19443236

Li, Huilin; Song, Fengrui; Xing, Junpeng; Tsao, Rong; Liu, Zhiqiang; Liu, Shuying

2009-04-14

128

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

NASA Astrophysics Data System (ADS)

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

Hassett, W.; Leech, M. L.

2007-12-01

129

Geographic and stratigraphic distribution of Miocene palynomorphs in north Idaho  

NASA Astrophysics Data System (ADS)

Acetolysis of Early and Middle Miocene sediments from the Clarkia, Idaho, area yielded 3,477 palynomorphs representing 37 taxa from eighteen samples for assemblage analysis. Relative pollen frequency data from various study sites suggest an older Coniferae-Mixed Dicotyledoneae-Pteridophyte Palynomorph Assemblage Zone, and a younger Fagaceae-TCT-Platanus Pollen Assemblage Zone. Two pollen based chronostratigraphic stages are proposed for at least part of the Miocene epoch: an older Clarkian Stage, and a younger Oviattian Stage. Palynomorph stratigraphic range charts document the youngest regional occurrence of Lygodium. Two palynomorph taxa are possible index fossils in the Pacific Northwest: (1) Sigmopollis (Incertae Sedis) for the Oligocene, and (2) Elaeagnus (Elaeagnaceae) for the Late Oligocene-Early Miocene. Palynostratigraphic and assemblage analyses of the fossil bearing sediments confirms prior models for the infilling of Miocene Clarkia Lake, and a regional change from a warm temperature to temperate climate.

Jorstad, R. B.

1983-02-01

130

Detailed foraminiferal biostratigraphy of the Danish marine Miocene formations.  

National Technical Information Service (NTIS)

The Miocene strata of eighteen boreholes from onshore Denmark have been investigated for their foraminiferal content. A dense sampling with intervals of about 0.5 metres has resulted in a very detailed biostratigraphy. Some of the boreholes were analyzed ...

G. V. Laursen F. N. Kristoffersen

1995-01-01

131

Palynostratigraphy of Oligocene-Miocene continental deposits in Southwestern Siberia  

NASA Astrophysics Data System (ADS)

Data on spores, pollen, and dinoflagellate cysts studied in composite section of Oligocene-Miocene deposits in southern part of West Siberia are presented. Eleven biostratigraphic units distinguished in the section are ranked as palynozones and beds with palynological assemblages. Palynological data substantiate age of deposits and specify ranges and boundaries of palynozones. Based on dinocyst assemblages first studied in sediments of the Zhuravka and Abrosimovo horizons (upper Oligocene, lower Miocene), the Pseudokomewuia Beds are included into local stratigraphic scheme. According to results of comparative analysis, similar and distinctive features of Oligocene-Miocene dinocyst assemblages from West Siberia, China and North America are elucidated. Based on palynological data, the local stratigraphic scheme of higher resolution is suggested for subdivision of Oligocene and Miocene deposits in southern part of West Siberia (Baraba and Kulunda lithofacies regions).

Kuz'mina, O. B.; Volkova, B. S.

2008-10-01

132

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

133

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

134

Climate impact of high northern vegetation: Late Miocene and present  

Microsoft Academic Search

The Late Miocene belongs to the late phase of the Cenozoic. Climate at that time was still warmer and more humid as compared\\u000a to today, especially in the high latitudes. Corresponding to the climate situation, palaeobotanical evidences support that\\u000a vegetation in the high northern latitudes changed significantly from the Late Miocene until today. To quantify the climate\\u000a impact of this

Rainer Schneck; Arne Micheels; Volker Mosbrugger

2011-01-01

135

"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

136

GROUP  

Microsoft Academic Search

In this paper we continue the study ofalg 1 (S) for minimal surfaces of general type S satisfying K2 S < 3?(S). We show that, if K 2 S = 3?(S) 1 and |?alg 1 (S)| = 8, then S is a Campedelli surface. In view of the results of (MP1) and (MP2), this implies that the fundamental group of

CIRO CILIBERTO; MARGARIDA MENDES LOPES; RITA PARDINI

137

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

NASA Astrophysics Data System (ADS)

Western Amazonia's landscape and biota were shaped by an enormous wetland during the Miocene epoch. Among the most discussed topics of this ecosystem range the question on the transitory influx of marine waters. Inter alia the occurrence of typically brackish water associated ostracods is repeatedly consulted to infer elevated salinities or even marine ingressions. The taxonomical investigation of ostracod faunas derived from the upper part of the Solimões Formation (Eirunepé; W-Brazil) documents a moderately diverse assemblage (19 species). A wealth of freshwater ostracods (mainly Cytheridella, Penthesilenula) was found co-occurring with taxa (chiefly Cyprideis) usually related to marginal marine settings today. The observed faunal compositions as well as constantly very light ?18O- and ?13C-values obtained by measuring both, the freshwater and brackish water ostracod group, refer to entirely freshwater conditions. These results corroborate with previous sedimentological and palaeontological observations, which proposed a fluvial depositional system for this part of western Amazonia during the Late Miocene. We demonstrate that some endemic, "brackish" water ostracods (i.e., Cyprideis) have been effectively adapted to freshwater conditions. Thus, their occurrence is no univocal evidence for the influence of brackish or marine waters in western Amazonia during the Miocene.

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

2013-03-01

138

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

PubMed

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

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

2010-06-14

139

Miocene deformation of the central Vienna Basin (Austria-Slovakia)  

NASA Astrophysics Data System (ADS)

The project KARPATIAN TECTONICS SLOVAKIA aims at the creation of a comprehensive geologic model of the structural evolution of the Vienna Basin area before the onset of major subsidence related to pull-apart deformation, i.e., during the Lower Miocene. Seismic data acquired by OMV from the central Vienna Basin and from the region east fo the Drösing depression, as well as outcrop data provide the basis for structural geologic interpretation of the entire central Vienna Basin. In this study, we focus on the complex structural evolution that can be mapped from these seismic datasets complementing the deformation geometry and history of the region east of the Spannberg ridge. The structural inventory found in the central Vienna Basin consist of (i) ENE and WSW dipping normal faults, (ii) SE- to ESE-dipping thrust faults, (iii) NW - SE-striking sinistral strike-slip faults (Hölzel et al., in press). These structural features can be found above the nappes of the Austroalpine Calcareous Alps, the nappes of the Tirolic and Bajuvaric superunits. In this study, we can complement the structures from East to West as follows: (1) The continution of the Lassee negative flower structure reaches up along the Lab fault system to the Laksary elevation. Here, it widens and branches off into at least two major branches engulfing the Laksary elevation. (2) N - S striking strike-slip faults penetrating the accoustic basement as well as Karpatian strata possibly form a continuing system that branches off of the Zwerndorf transform fault system. (3) In the center of the Gajary depression, normal faults offset the accoustic basement above sediments of the Upper Cretaceous Gosau Group. These features can be dated by Karpatian growth strata. However, the normal faults were not always active at the same time as indicated by the geometry of the sedimentary strata bounded by the normal faults. (4) At the western boundary of the Gajary depression, smaller scale normal faults deform the Aderklaa Conglomerate (Top Karpatian). (5) NW - SE trending grabens in the basement and Karpatian strata occur in the center and SE corner of the Gajary depression. (6) The entire Karpatian sedimentary stack including the Top Karpatian is tilted towards the West forming the central part of the Levare depression to the North of the Gajary depression. Hölzel, M., Decker, K., Zámolyi, A., Strauss, P., Wagreich, M. (in press): Lower Miocene structural evolution of the central Vienna Basin (Austria). Marine and Petroleum Geology

Zámolyi, András.; Lee, Eun Young; Beidinger, Andreas; Hoprich, Maria; Strauss, Philipp; Decker, Kurt

2010-05-01

140

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

141

Low-temperature hydrothermal alteration of intra-caldera tuffs, Miocene Tejeda caldera, Gran Canaria, Canary Islands  

Microsoft Academic Search

The Miocene Tejeda caldera on Gran Canaria erupted ~20 rhyolite–trachyte ignimbrites (Mogán Group 14–13.3 Ma), followed by ~20 phonolitic lava flows and ignimbrites (Fataga Group 13–8.5 Ma). Upper-Mogán tuffs have been severely altered immediately within the caldera margin, whereas extra-caldera Mogán ignimbrites, and overlying Fataga units, are apparently unaltered. The altered intra-caldera samples contain minerals characteristic of secondary fluid–rock interaction (clays, zeolites,

Eleanor Donoghue; Valentin R. Troll; Chris Harris; Aoife O'Halloran; Thomas R. Walter; Francisco J. Pérez Torrado

2008-01-01

142

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

143

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

144

Modeling geologically abrupt climate changes in the Miocene  

NASA Astrophysics Data System (ADS)

The gradual cooling of the Cenozoic, including the Miocene epoch, was punctuated by many geologically abrupt warming and cooling episodes - strong deviations from the cooling trend with time span of ten to hundred thousands of years. Our working hypothesis is that some of those warming episodes at least partially might have been caused by dynamics of the emerging Antarctic Ice Sheet, which, in turn, might have caused strong changes of sea surface salinity in the Miocene Southern Ocean. Feasibility of this hypothesis is explored in a series of coupled ocean-atmosphere computer experiments. The results suggest that relatively small and geologically short-lived changes in freshwater balance in the Southern Ocean could have significantly contributed to at least two prominent warming episodes in the Miocene. Importantly, the experiments also suggest that the Southern Ocean was more sensitive to the salinity changes in the Miocene than today, which can attributed to the opening of the Central American Isthmus as a major difference between the Miocene and the present-day ocean-sea geometry.

Haupt, B. J.; Seidov, D.

2010-12-01

145

Miocene sequence biostratigraphy of the northern Gulf of Mexico  

SciTech Connect

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 comparable to the Haq et al.'s third-order cycles in the Miocene. After iterative comparison, the condensed intervals of these Miocene third-order sequences have been determined as, in descending order, Cyclammina 3, the second Cibicides carstensi, the second Textularia W, Cristellaria I, Robulus 43, Discorbis B, the third Marginulina A, and Textularia panamensis (= fauna unit II). The least prominent pulses suggesting the third-order cycle highstands (or shelf-margin wedges) are suggested as, in descending order, Textularia X, Bolivina thalmanni, Globorotalia fohsi robusta, Bigenerina humblei, Cibicides opima, Saracenaria schencki, Marginulina A (= second Robulus chambersi), and Siphonina davisi. Redeposited Cretaceous nanno species are an important component in the Gulf of Mexico middle and lower Miocene. Significant concentrations of these species are found primarily in the third-order cycle highstands, one exception being the Marginulina A third-order cycle highstand that in the High Island and West Cameron areas contained only rare redeposited Cretaceous nannos.

Jiang, M.M. (ARCO Oil and Gas Company, Houston, TX (United States))

1993-09-01

146

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

147

Interpretive mineralogy: examples from Miocene coastal plain sediments  

SciTech Connect

Gulf Coast Miocene sediments are among the most lithologically complex in the entire nation. This varied lithology stems in part from multiple source areas that were active during this interval; but also if reflects major tectonic events that influenced depositional patterns throughout the Gulf Coast during the Miocene. Because fossils are scarce or lacking in many of the units, important questions relating to a number of geologic problems have been discussed illustrating how such analyses can be used to: (1) clarify stratigraphic relationships between units in contact, (2) define environmental conditions in the depositional basin, (3) reconstruct paleoclimate conditions, and (4) identify provenance area. A major anomaly in the mineralogy of central Gulf Coast Miocene sediments is explained by postulating a major ancestral Tennessee River originating in the southern Appalachians and flowing southwestward across Alabama and Mississippi to a terminus in the ancient Gulf of Mexico.

Isphording, W.C.

1983-09-01

148

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

149

Middle Miocene tectonic boundary conditions for use in climate models  

NASA Astrophysics Data System (ADS)

Utilizing general circulation models (GCMs) for paleoclimate study requires the construction of appropriate model boundary conditions. We present a middle Miocene paleotopographic and paleobathymetric reconstruction geographically constrained at 15 Ma for use in GCMs. Paleotopography and paleogeography are reconstructed using a published global plate rotation model and published geological data. Paleobathymetry is reconstructed through application of an age-depth relationship to a middle Miocene global digital isochron map, followed by the overlay of reconstructed sediment thickness and large igneous provinces. Adjustments are subsequently made to ensure our reconstruction may be utilized in GCMs.

Herold, N.; Seton, M.; Müller, R. D.; You, Y.; Huber, M.

2008-10-01

150

Late miocene tidal deposits in the amazonian foreland basin.  

PubMed

Late Miocene tidal sediments of Acre, Brazilian Amazonia, were deposited in an embayment or interior seaway located in the sub-Andean zone. This late Tertiary embayment system may once have connected the Caribbean with the South Atlantic. The tidal coasts of the embayment-seaway have provided an avenue for the earliest waif (over water) dispersal phases of the great American biotic interchange in the late Miocene. The subsequent change from semimarine to terrestrial environments is of value in assessing the importance of earlier hypotheses on the evolution of the westem Amazonian landscape and gives insight into the formation of several observed biogeographic patterns, especially of aquatic biota. PMID:17841262

Räsänen, M E; Linna, A M; Santos, J C; Negri, F R

1995-07-21

151

Middle Miocene tectonic boundary conditions for use in climate models  

Microsoft Academic Search

Utilizing general circulation models (GCMs) for paleoclimate study requires the construction of appropriate model boundary conditions. We present a middle Miocene paleotopographic and paleobathymetric reconstruction geographically constrained at 15 Ma for use in GCMs. Paleotopography and paleogeography are reconstructed using a published global plate rotation model and published geological data. Paleobathymetry is reconstructed through application of an age-depth relationship to

N. Herold; M. Seton; R. D. Müller; Y. You; M. Huber

2008-01-01

152

A Miocene basanite peperitic dyke at Stanley, northwestern Tasmania, Australia  

Microsoft Academic Search

A Miocene basanite dyke at Stanley, northwestern Tasmania, Australia, displays well preserved peperite texture. The dyke is 2 m wide and has intruded basaltic breccia (“host sediment”). One contact of the dyke is fluidally shaped, and amoeboid apophyses 10–25 cm long extend into the host sediment, whereas the other contact is characterized by blocky peperite texture comprising tabular to wedge-shaped

Yoshihiko Goto; Jocelyn McPhie

1996-01-01

153

Ptychoptera deleta Nov?k, 1877 from the Early Miocene of the Czech Republic: redescription of the first fossil attributed to Ptychopteridae (Diptera)  

PubMed Central

Abstract The first fossil that was described in Ptychopteridae, Ptychoptera deletaNovák, 1877 from the classical Early Miocene locality Mok?ina (Krottensee) in western Bohemia is re-examined. The re-description of the holotype including a new line drawing and remarks summarizing the scarce fossil record of this group is provided.

Krzeminski, Wieslaw; Prokop, Jakub

2011-01-01

154

On Miocene Coenothecalia Heliopora Coerulea (Pallas)of Coral Reefs from The Tanzawa MountainsSouthern Kanto MountainsCentral Japan  

Microsoft Academic Search

Miocene Tanzawa Group is distributed in the Tanzawa Mountains of the southern Kantocentral Japanand is composed of thick green tuff strata. Limestone lenses in the strata are intercalated in multiple sizesin thichness from a few meters to 50meters. Fossil of coral reef creatures yielded in the limestone. We found a couple of very interesting fossils in one of these limestones

Masahito KADOTA; Yoshifumi MISAWA

155

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

156

Continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries after the study period: Was this the Hawthorne effect?  

Microsoft Academic Search

BackgroundThe incidence of birth trauma and birth asphyxia related to instrumental deliveries in our obstetric unit was high (2.8%) in 1998–1999. A study was performed in 2000 to identify the risk factors. Unexpectedly, the incidence (0.6%) was reduced significantly during the study period. We attributed this phenomenon to the famous Hawthorne effect (tendency to improve performance because of awareness of

W. C. Leung; B. C. P. Chan; G. Ma; K. W. Lam; K. Y. Leung; T. C. Pun; T. T. Lao; C. P. Lee

2007-01-01

157

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

158

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

PubMed Central

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

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

2011-01-01

159

Magnetostratigraphy of the Miocene Chiang Muan Formation, northern Thailand: Implication for revised chronology of the earliest Miocene hominoid in Southeast Asia  

Microsoft Academic Search

A paleomagnetic study has been conducted on the Miocene Chiang Muan Formation in northern Thailand, in order to provide a chronology for the earliest large-bodied Miocene hominoid in Southeast Asia. The Chiang Muan Formation is mainly composed of clay, silt and sand beds, indicating lacustrine and fluvial environments. Paleomagnetic samples were collected from 124 horizons along an approximately 150 m

Y. Suganuma; T. Hamada; S. Tanaka; M. Okada; H. Nakaya; Y. Kunimatsu; H. Saegusa; S. Nagaoka; B. Ratanasthien

2006-01-01

160

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

161

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

162

Systematics and evolution of the Australian knob-tail geckos (Nephrurus, Carphodactylidae, Gekkota): plesiomorphic grades and biome shifts through the Miocene.  

PubMed

Clades that predate the origin of biomes that they inhabit provide unique opportunities to examine both when major environmental transitions occurred, and how lineages adapted to these changes. The isolated island continent Australia has undergone a profound environmental transition through the Miocene, from relatively mesic to predominantly arid; however, we have much to learn about both the timing of this change, and how organisms may have responded to it. The family Carphodactylidae is an ancient Gondwanan group of geckos that occurs across all major Australian biomes. A multilocus (ND2, Rag-1, c-mos) phylogenetic and dating analysis of the most ecologically diverse clade within this group, the genus Nephrurus (sensuBauer, 1990) reveals that two of three morphological taxa historically recognized (the 'spiny knob-tails' and 'Underwoodisaurus') are relatively species depauperate, pleisomorphic basal grades that diversified through the late Oligocene and early Miocene, and are now absent from most of the arid biome. Based on their deep divergence and morphological distinctiveness we recognize two lineages (milii and sphyrurus) as monotypic genera, the later of which is named herein (Uvidicolus nov. gen). In contrast, a third morphological group, the 'smooth knob-tails,' is a monophyletic group of five exclusively arid zone burrowing species that has radiated relatively recently (mid-Miocene). Our phylogeny indicates that successful colonization of this novel and challenging biome by Nephrurus correlates with an initial shift to terrestriality and adaptation to at least seasonally arid conditions around the early Miocene, and the eventual evolution and subsequent mid-Miocene radiation of a lineage specialized for burrowing. PMID:21421065

Oliver, Paul M; Bauer, Aaron M

2011-03-21

163

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

Microsoft Academic Search

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

Stephen J. Reynolds; M. Shafiqullah; Paul E. Damon; Ed DeWitt

1986-01-01

164

Diagenesis in upper Miocene sandstones, Louisiana Gulf Coast  

SciTech Connect

Study of diagenesis in upper Miocene sandstones of coastal Louisiana documents depth-related cementation and geochemical changes of primary detrital mineralogy. Samples were collected from depths of 8000-20,000 ft (2600-6500 m) in an area roughly corresponding to the upper Miocene depocenter in the Terrebonne trough of southeast Louisiana. Sandstones are primarily subarkoses and sublitharenites with minor amounts of feldspathic litharenites and lithic arkoses. Plagioclase feldspar (oligoclase/andesine composition) composes approximately 60% of the detrital feldspar. Dominant rock fragments are siltstone or mudstone, silicified volcanic rock, and chert. Authigenic minerals and cements occur in the following order: dolomite, chlorite grain coats, albite overgrowths on plagioclase and K-feldspar, quartz, calcite, kaolinite, and ankerite. Calcite composition remains nearly constant with depth, but ankerite composition differs both with depth and within individual samples. In general, the mineralogy and order of cements resemble that of the lower Tertiary sandstones of the Texas Gulf Coast; however, in the upper Miocene, the volume of each cement is much less and the depth of first occurrence is greater. Feldspars have reacted substantially with pore fluids. With increasing depth, feldspar becomes more sodic because of albitization and dissolution of calcic plagioclase. At approximately 20,000 ft, 75% of the plagioclase is nearly pure albite. Alteration of K-feldspar is not common above 17,000 ft; below 17,000 ft occurrences are rare because of dissolution.

Gold, P.B.

1985-02-01

165

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

USGS Publications Warehouse

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

Scarborough, Robert Bryan; Wilt, Jan Carol

1979-01-01

166

Simultaneous determination of three polyphenols in rat plasma after orally administering hawthorn leaves extract by the HPLC method.  

PubMed

A simple and sensitive HPLC method was developed to simultaneously determine three active compounds, vitexin-4?-O-glucoside (VG), vitexin-2?-O-rhamnoside (VR) and hyperoside (HP), in rat plasma after administering the hawthorn leaves extract (HLE). An HPLC assay with baicalin as the internal standard was carried out using a Phenomsil C?? analytical column with UV detection at 332?nm. The mobile phase consisted of methanol-acetonitrile-tetrahydrofuran-1% glacial acetic acid (6?:?1.5?:?18.5?:?74, v/v/v/v). The calibration curves were linear over the range of 2.5-500, 0.2-25 and 0.25-12.5?µg?mL?¹ for VG, VR and HP, respectively. The method was reproducible and reliable, with relative standard deviations of the intra- and inter-day precision between 1.2% and 13.2% for the analysis of the three analytes. The validated HPLC method herein described was successfully applied to the pharmacokinetic study of VG, VR and HP after oral administration of HLE to rats over the dose range of 2.5-10 ?mL?kg?¹. PMID:21867394

Ying, Xixiang; Meng, Xiansheng; Wang, Siyuan; Wang, Dong; Li, Haibo; Wang, Bing; Du, Yang; Liu, Xun; Zhang, Wenjie; Kang, Tingguo

2011-08-25

167

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

168

Biofacies zonation of middle Miocene benthic foraminifera, southeastern San Joaquin basin, California  

SciTech Connect

The quantitative distribution of benthic foraminifera across the middle Miocene margin of the southeastern San Joaquin basin constitutes a useful tool in applying benthic biofacies zonation to the interpretation of marine paleoenvironments. A middle Miocene transect (near the Luisian/Relizian boundary) was completed across the margin of the southeastern San Joaquin basin near Bakersfild, California. Surface and subsurface fauna encompass strandline through bathyal environments. Quantitative analyses of these fauna result in a useful biofacies zonation for the middle Miocene which can be applied to the interpretation of middle Miocene paleobathymetric and paleogeographic reconstructions, basin analysis, and subsidence histories of the San Joaquin basin. In addition, these data suggest that vertical faunal migration of continental slope fauna has occurred between the middle Miocene and Recent. During the early and middle Miocene, marine temperatures were warmer than today and lower latitudinal gradients prevailed. Stepwise climatic cooling since the middle Miocene has been accompanied by the latitudinal adjustment of surface isotherms, strengthening of the permanent thermocline, and the associated migration of temperature-sensitive planktonic and benthic biofacies. Sedimentologic and seismic evidence in the southeastern San Joaquin basin suggests that present-day lower bathyal biofacies may have been at shallower depths during the middle Miocene. Such migrations would have a significant impact on paleoenvironmental interpretations. Middle Miocene faunal transects from the southeastern San Joaquin basin are compared with equivalent Holocene transects from the eastern Pacific, and differences are discussed in light of this proposal.

Olson, H.C.

1987-05-01

169

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

170

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

171

A new solid-phase extraction and HPLC method for determination of patulin in apple products and hawthorn juice in China.  

PubMed

A new solid-phase extraction (SPE) pretreatment method using a home-made polyvinylpolypyrrolidone-florisil (PVPP-F) column was developed for the analysis of patulin in apple and hawthorn products in China. Fifty samples (25 apple juices, 12 apple jams, and 13 hawthorn juices) were prepared using the new method and then analyzed by high performance liquid chromatography with diode array detection (HPLC-DAD) on an Agela Venusil MP C(18) reversed-phase column (4.6 mm × 250 mm, 5 ?m). The cleanup results for all samples using home-made PVPP-F column were compared with those obtained using a MycoSep®228 AflaPat column. The correlation coefficient R (0.9998) fulfilled the requirement of linearity for patulin in the concentration range of 2.5-250 ?g/kg. The limits of detection (LODs) and quantification (LOQs) of patulin were 3.99 and 9.64 ?g/kg for PVPP-F column, and 3.56 and 8.07 ?g/kg for MycoSep®228 AflaPat column, respectively. Samples were spiked with patulin at levels ranging from 25 to 250 ?g/kg, and recoveries using PVPP-F and MycoSep®228 AflaPat columns were in the range of 81.9-100.9% and 86.4-103.9%, respectively. Naturally occurring patulin was found in 2 of 25 apple juice samples (8.0%) and 1 of 13 hawthorn juice samples (7.7%) at concentrations ranging from 12.26 to 36.81 ?g/kg. The positive results were further confirmed by liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS). PMID:22517639

Zhou, Yuchun; Kong, Weijun; Li, Yan; Logrieco, Antonio F; Xu, Jun; Yang, Meihua

2012-03-01

172

Screening and structural characterization of ? -glucosidase inhibitors from hawthorn leaf flavonoids extract by ultrafiltration LC-DAD-MS n and SORI-CID FTICR MS  

Microsoft Academic Search

In vitro ?-glucosidase inhibition assays and ultrafiltration liquid chromatography with photodiode array detection coupled to electrospray\\u000a ionization tandem mass spectrometry (ultrafiltration LC-DAD-ESI-MS\\u000a n\\u000a ) were combined to screen ?-glucosidase inhibitors from hawthorn leaf flavonoids extract (HLFE). As a result, four compounds\\u000a were identified as ?-glucosidase inhibitors in the HLFE, and their structures were confirmed to be quercetin-3-O-rha- (1-4)-glc-rha\\u000a and C-glycosylflavones

Huilin Li; Fengrui Song; Junpeng Xing; Rong Tsao; Zhiqiang Liu; Shuying Liu

2009-01-01

173

Volcanic and Glacial Geology of the Miocene Minna Bluff Volcanic Complex, Antarctica  

Microsoft Academic Search

Minna Bluff is a 45-km long, 5-km wide Miocene alkaline volcanic peninsula that extends SE into the Ross Ice Shelf from the Mt. Discovery stratovolcano. Minna Bluff is a significant topographic barrier that has effectively blocked the Ross Ice Shelf and former grounded marine ice sheets from flowing southward into McMurdo Sound. In the late Miocene, Minna Bluff likely was

T. I. Wilch; W. C. McIntosh; K. S. Panter; N. W. Dunbar; J. L. Smellie; A. Fargo; M. Scanlan; M. J. Zimmerer; J. Ross; M. E. Bosket

2008-01-01

174

Dietary resource partitioning in ruminant communities of Miocene wetland and karst palaeoenvironments in Southern Germany  

Microsoft Academic Search

Ruminants made up a major component in Early and Middle Miocene European land mammal faunas. Hypotheses are tested which concern the diversity of feeding niches in Miocene ruminants and their resource partitioning. Because teeth are the basis of taxonomic work in the biota investigated here, the tooth-based mesowear method of dietary evaluation is applied. Dental wear equilibria as evaluated using

Thomas M. Kaiser; Gertrud E. Rössner

2007-01-01

175

An objective statistical test for eccentricity forcing of Oligo-Miocene climate  

Microsoft Academic Search

We seek a maximally objective test for the presence of orbital features in Oligocene and Miocene delta18O records from marine sediments. Changes in Earth's orbital eccentricity are thought to be an important control on the long term variability of climate during the Oligocene and Miocene Epochs. However, such an important control from eccentricity is surprising because eccentricity has relatively little

C. Proistosescu; P. Huybers; A. C. Maloof

2008-01-01

176

Wetland paradise lost: Miocene community dynamics in large herbivorous mammals from the German Molasse Basin  

Microsoft Academic Search

Questions: What was the distribution of fossil mammal taxa in the Miocene German Molasse Basin? Were there changes in community structure during the terrestrial development of the Molasse Basin? Were community dynamics similar in the Molasse Basin to those in the rest of Europe? Data: We gathered the available Miocene large mammal herbivore occurrences from the southern German Molasse Basin

Jussi T. Eronen; Gertrud E. Rössner

2007-01-01

177

Modelling the climate impact of high-latitude vegetation in the Late Miocene  

Microsoft Academic Search

During the Cenozoic, global climate got successively colder. The Late Miocene belongs to the late phase of the Cenozoic cooling. The climate at that time was still warmer and more humid as compared to today. Especially, high latitudes were warmer. Corresponding to the climate situation, palaeobotanical evidences support that vegetation in the high latitudes changed significantly from the Late Miocene

R. Schneck; A. Micheels; V. Mosbrugger

2009-01-01

178

Middle Miocene extension in the Gulf Extensional Province, Baja California: Evidence from the southern Sierra Juarez  

Microsoft Academic Search

New geologic mapping, structural stud- ies, and geochronology of Miocene volcanic and sedimentary rocks in the southern Si- erra Juarez, Baja California, shed light on the extensional history of the Gulf Exten- sional Province prior to sea-floor spreading in the Gulf of California. The southern Si- erra Juarez is underlain by lower-middle Miocene rocks including fluvial strata, in- termediate composition

Jeffrey Lee; M. Meghan Miller; Robert Crippen; Bradley Hacker; Jorge Ledesma Vazquez

1996-01-01

179

Miocene diatom biostratigraphy of DSDP (Deep Sea Drilling Project) hole 272: Stratigraphic relationship to the underlying Miocene of DSDP hole 270, Ross Sea  

SciTech Connect

Diatoms are the best biostratigraphic tool for high-resolution dating the Ross Sea Miocene. Discussed here are: previous diatom investigations of DSDP hole 272; new diatom data from the Ross Sea, including re-study of diatoms in DSDP 272 and the first report of pre-Pleistocene diatoms from DSDP site 270; and estimation of the temporal and stratigraphic gap separating the bottom of DSDP hole 272 from the top of the underlying Miocene of DSDP hole 270.

Steinhauff, D.M.; Renz, M.E.; Harwood, D.M.; Webb, P.N. (Ohio State Univ., Columbus (USA))

1987-01-01

180

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

181

Dynamics of ~100-kyr glacial cycles during the early Miocene  

NASA Astrophysics Data System (ADS)

Here, we present high-resolution stable isotope records from ODP Site 1264 in the South-Eastern Atlantic Ocean, which resolve the latest Oligocene to early Miocene (23.7-18.9 Ma) climate changes. Using an inverse modelling technique, we decomposed the oxygen isotope record into temperature and ice volume and found that the Antarctic ice sheet expanded during distinct episodes (e.g., Mi zones) of low short-term (~100-kyr) eccentricity forcing, which occur two to four long-term (400-kyr) eccentricity cycles apart. We argue that a~non-linear mechanism, such as the merging of (several) large East Antarctic ice sheets, caused the build-up of a larger ice sheet. During the termination phases of these larger ice sheets, on the contrary, we find a more linear response of ice-sheet variability to orbital forcing and climate became highly sensitive to the ~100-kyr eccentricity cycle. At the Oligocene-Miocene transition the model output indicates a decrease in Northern Hemisphere temperatures such that a small ice cap could develop on Greenland. This Supports the hypothesis of a threshold response for the development of Northern Hemisphere land ice to decreasing pCO2.

Liebrand, D.; Lourens, L. J.; Hodell, D. A.; de Boer, B.; van de Wal, R. S. W.

2010-12-01

182

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

183

Tropical sea surface temperature variability near the Oligocene - Miocene boundary  

NASA Astrophysics Data System (ADS)

The Oligocene/Miocene (O-M) boundary is characterized by a period of rapid and intense glaciation labeled Mi-1 at ~ 23.1 Ma. An abrupt 1.5‰ increase in the benthic foraminifera oxygen isotope composition that characterizes Mi-1 may indicate a (1) significant deep-water temperature decrease; (2) major ice-sheet expansion, or the combination of both. Current coarse Mg/Ca-based temperature estimations for the early Miocene suggests that deep-ocean temperatures were ~2°C warmer than Today [1, 2]. However, Mg/Ca based temperatures can also be influenced by changes in the carbonate ion concentration, vital effects, and diagenesis. In particular, recent evidence from mid-ocean ridge flank carbonate veins shows dramatic seawater Mg/Ca ratio changes during the Neogene (Mg/Ca from ~2.2 to 5.3, [3]), which further challenges the application of Mg/Ca thermometry. Owing to poor temperature constraints, current ice volume estimations for the late Oligocene/early Miocene range from 125% of the present-day East Antarctic Ice Sheet (EAIS) to a nearly complete collapse of the Antarctic glaciers [4]. Here we present tropical sea surface temperatures (SSTs) records based on TEX86 and alkenone UK37 near the O-M boundary. Sediment samples from Ocean Drilling Program (ODP) Site 926 in the Ceara Rise (tropical Atlantic) and Site 1148 in the South China Sea (tropical Pacific) were subject to lipid extraction, separation, gas chromatography, and liquid chromatography-mass spectrometry analysis. TEX86-based SST indicates that the tropics were ~3-4°C warmer than today and relatively stable during Mi-1. This suggests that ice-sheet dynamics, rather than temperature, might be responsible for the observed oxygen isotope changes during the O-M boundary. Further, O-M boundary averaged temperatures recorded at site 926 is ~ 0.5°C higher relative to the late Eocene from site 925 (a nearby site [5]). Given late Oligocene benthic ?18O that suggests at least 1‰ enrichment relative to the late Eocene (e.g. ODP 1218 [2]), our records suggest major Antarctic ice build-up in the Oligocene. Additional work across high-latitude sites is necessary to evaluate how the extratropics responded to climate change during Mi-1, as well as modeling efforts to quantitatively resolve ice volume from temperature. [1] K. Billups, D.P. Schrag, Paleotemperatures and ice volume of the past 27 Myr revisited with paired Mg/Ca and 18O/16O measurements on bethic foraminifera, Paleoceanography 17(2002). [2] C.H. Lear, Y. Rosenthal, H.K. Coxall, P.A. Wilson, Late Eocene to early Miocene ice sheet dynamics and the global carbon cycle, Paleoceanography 19(2004). [3] R.M. Coggon, D.A.H. Teagle, C.E. Smith-Duque, J.C. Alt, M.J. Copper, Reconstructing past seawater Mg/Ca and Sr/Ca from Mid-Ocean Ridge flank calcium carbonate veins, Science 327(2010) 1141-1147. [4] S.F. Pekar, R.M. DeConto, High-resolution ice-volume estimates for the early Miocene: Evidence for a dynamic ice sheet in Antarctica, Palaeogeogr. Palaeoclimatol. Palaeoecol. 231(2006) 101-109. [5] Z. Liu, M. Pagani, D. Zinniker, R. DeConto, M. Huber, H. Brinkhuis, S.R. Shah, R.M. Leckie, A. Pearson, Global Cooling During the Eocene-Oligocene Climate Transition, Science 323(2009) 1187-1190.

Zhang, Y.; Pagani, M.

2010-12-01

184

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

185

Biostratigraphic sequence analysis of two Lower Miocene to Pliocene sections, Eastern Falcon, Northwestern Venezuela  

SciTech Connect

The eastern region of the Falcon Basin in northwestern Venezuela comprises a thick sedimentary sequence deposited from a deep marine bathyal to neritic environment, ranging in age from the Middle Eocene to the Pliocene. A detailed biostratigraphic study (foraminifera and calcareous nannoplankton) was carried out in two sedimentary sequences outcropping in Cumarebo and Piritu, adjacent areas of eastern Falcon, representing: platform, slope and basinal settings. The Cumarebo section is continuous in the studied interval, from the Middle Miocene to the Pliocene. The Piritu section is continuous from the Lower to the lower Upper Miocene, terminating unconformably beneath a thin interval of middle Pliocene platform sediments, indicating tectonism during the latest Miocene. The sequence stratigraphical interpretation was based on the biostratigraphic analysis of the benthic and planktonic fossils, facies distribution and sedimentological data. Systems tracts, sequence boundaries and maximum flooding surfaces from cycles TB2.4 to TB3.5 of the cycle chart were identified. In the Cumarebo section, the upper Middle and Upper Miocene is mostly composed of shales, with some turbiditic sands belonging to a LSW system tract. The upper most Miocene contains a thick carbonate buildup (HST), and it is overlain by a Pliocene section that shallows upward from upper slope to outer shelf depositional environments. In the basinal (Piritu) section, most of the sediments are deep-water shales belonging to a LSW system tract, with some turbiditic sands in the upper Lower Miocene. TST and HST sediments, with scattered carbonate buildups in the upper Middle Miocene were also identified.

Diaz De Gamero, M.L. (Universidad Central de Venezuela, Caracus (Venezuela)); Giffuni, G.; Castro Mora, M. (Lagoven S.A., Caracus (Venezuela))

1993-02-01

186

Simultaneous Miocene Extension and Shortening in the Himalayan Orogen  

NASA Astrophysics Data System (ADS)

The South Tibetan detachment system separates the high-grade metamorphic core of the Himalayan orogen from its weakly metamorphosed suprastructure. It is thought to have developed in response to differences in gravitational potential energy produced by crustal thickening across the mountain front. Geochronologic data from the Rongbuk Valley, north of Qomolangma (Mount Everest) in southern Tibet, demonstrate that at least one segment of the detachment system was active between 19 and 22 million years ago, an interval characterized by large-scale crustal thickening at lower structural levels. These data suggest that decoupling between an extending upper crust and a converging lower crust was an important aspect of Himalayan tectonics in Miocene time.

Hodges, K. V.; Parrish, R. R.; Housh, T. B.; Lux, D. R.; Burchfiel, B. C.; Royden, L. H.; Chen, Z.

1992-11-01

187

A Miocene submarine volcano at Low Layton, Jamaica  

NASA Astrophysics Data System (ADS)

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

Wadge, G.

188

Miocene foraminifera from DSDP site 272, Ross Sea  

SciTech Connect

At site 272 a major decrease in foraminiferal abundance and diversity is noted between approximately 138 and 148 meters subbottom. This roughly corresponds to the subunit 2A/2B boundary and occurs at the level of a proposed 4-million-year hiatus which separates Lower and Middle Miocene sediments. Only sporadic occurrences of robust thick-walled forms such as Islandiella spp., Epistominella exigua, Globocassidulina subglobosa, and Nonionella iridea occur below 147 meters (in subunit 2B) and much of the lower succession is barren of foraminifera. Absence of fauna is attributed to dissolution contemporaneous with deposition, or post-depositional diagenesis. Site 272 foraminiferal assemblages may have been subjected to glacial transport and redeposition and/or bottom current reworking. The wide size range of foraminifera at any stratigraphic level suggests size sorting is not a significant factor.

Steinhauff, D.M. (Univ. of Tennessee, Knoxville (USA)); Webb, P.N. (Ohio State Univ., Columbus (USA))

1987-01-01

189

Miocene ocean circulation inferred from marine carbon cycle modeling combined with benthic isotope records  

NASA Astrophysics Data System (ADS)

In a modeling sensitivity study we investigate the evolution of the ocean circulation and of marine carbon isotope (?13C) records during the Miocene (about 23-5 million years ago). For this purpose we ran an ocean-circulation carbon cycle model of intermediate complexity (Large Scale Geostrophic- Hamburg Ocean Carbon Cycle Model, version 2s) exploring various seaway configurations. Our investigations confirm that the Central American Seaway played a decisive role in the history of the Miocene ocean circulation. In simulations with a deep Central American Seaway (depth range 1-3 km), typical for the early to middle Miocene, deep water production in the North Atlantic is absent or weak, while the meridional overturning circulation is dominated by water mass formation in the Southern Ocean. Deep water formation in the North Atlantic begins when the Central American Seaway shoals to a few hundreds of meters, which is typical for the late Miocene. Our results do not support ideas that the mid-Miocene closing of the Eastern Tethys contributed to Antarctic glaciation. On the other hand, we find some water exchange between the Indian Ocean and the Atlantic via the Eastern Tethys during the early Miocene. Our model results for the Atlantic meridional overturning circulation and for Atlantic ?13C during the late Miocene are largely independent from depth variations of the Greenland-Scotland Ridge. To a large extent, the evolution of Miocene deep-sea ?13C records can be explained with large-scale ocean circulation changes. Our model-data comparison for the middle and early Miocene suggests that during the early Neogene the seaway effect on benthic ?13C may have been superimposed by further factors such as climate regime shifts and/or terrestrial carbon cycle changes.

Butzin, Martin; Lohmann, Gerrit; Bickert, Torsten

2011-02-01

190

Reservoir development in Miocene carbonates, Central Luconia Province, offshore Sarawak  

SciTech Connect

The broad platform of the central Luconia province of offshore Sarawak is characterized by extensive development of Miocene carbonates. Their distribution was controlled by paleostructures that formed earlier during Oligocene-middle Miocene faulting. Platform-type buildings formed on fault-bounded regional highs, whereas pinnacle types formed in basinal areas. Relief of the pinnacles was controlled by fault reactivation of the structures during deposition, and some buildups in structurally stable areas ceased to develop because they could not keep pace with rising sea levels. Seismic, well-log, and rock data of several buildups from different stratigraphic levels (Cycles III-VI) were integrated in formulating a model for reservoir development in the Luconia carbonates. Depositional and diagenetic cycles due to eustatic sea level changes exerted strong influence on the internal architecture of the buildups. Cycling depositional patterns, represented by alternating layers with good and poor porosities, include small-scale units (<3 m thick) recognized in cores and reservoir-scale successions (>63 m thick) identifiable in well logs and seismic data. Cycle V carbonates, for instance, consist of three Tortonian-Messinian depositional sequences. Two layers of dolomite formed in all buildups, each contemporaneous with a period of emergence. The Messinian diagenetic cycle, related to the 5.5 Ma sea level lowstand, partially overprinted the Tortonian diagenetic cycle that occurred during the 6.3 Ma lowstand. Superposition of these diagenetic cycles, with leaching, chalkification, and dolomitization, is responsible for a complex pore geometry in the carbonate reservoirs. This model can be applied to map the reservoir units in the carbonate buildups within the entire basin.

Ali, M.Y. (Petronas Research and Scientific Services, Kuala Lumpur (Malaysia))

1994-07-01

191

Middle Miocene climate and vegetation modelling with PLASIM and CARAIB  

NASA Astrophysics Data System (ADS)

In a long-term climatic cooling trend, the Middle Miocene represents one of the last warm periods of the Neogene, culminating with the Miocene Climatic Optimum, MCO (17-15 My). Palynological studies suggest that the warmer climatic conditions prevailing during the MCO allowed warm forests to expand poleward of the subtropical zone, with evergreen forests proliferating in North America and Europe (Jimenez-Moreno and Suc, 2007, Palaeogeogr. Palaeoclimatol. Palaeoecol. 253: 208-225). In this work, we used the Planet Simulator (Fraedrich et al., 2005, Meteorol. Z. 14: 299-304 and 305-314), an Earth system model of intermediate complexity, to carry out several simulation experiments, where we have assessed the effects of the absence of ice on the continents, the opening of the Central American and Eastern Tethys seaways, the lowering of the topography on land and the effect of various atmospheric CO2 concentrations, in agreement with the values reported in the litterature. We then produced several vegetation distributions, using the dynamic vegetation model CARAIB (Galy et al., 2008, Quat. Sci. Rev. 27: 1396-1409), to analyse if the climatic forcings considered are sufficient to explain the expansion of warmer forest types to higher latitudes. Our results indicate that an increase of atmospheric CO2 concentration, higher than the present-day one, is necessary to allow subtropical forest types to expand poleward. This result agrees wih recent paleo-atmospheric CO2 reconstruction from stomatal frequency analysis, which suggests 500 ppmv of CO2 during the MCO. However, the required warming may be due to processes not considered in our setup (e.g. full oceanic circulation or other greenhouse gases).

Henrot, A.-J.; François, L.; Munhoven, G.; Favre, E.; Butzin, M.

2009-04-01

192

Silica diagenesis in Santa Cruz mudstone, Late Miocene, California  

SciTech Connect

The silica-rich upper Miocene Santa Cruz Mudstone is similar to the Miocene Monterey Formation. Previous studies have suggested the Santa Cruz Mudstone was not buried deeply nor had it undergone extensive diagenesis. Because opaline diagenesis is temperature dependent, the author examined the silica diagenesis of the Santa Cruz Mudstone using scanning electron microscopy and x-ray diffraction methods to study its burial history. In a series of samples from Santa Cruz to Davenport, California (over 16 km), opal-CT is the dominant silica phase present and clay minerals are notably absent. The d(101)-spacing values of opal-CT range from 4.11 A (Santa Cruz area) to 4.06 A (north of Santa Cruz), exhibiting the complete range of d(101)-spacing values found in opal-CT zones. Scanning electron micrographs of crystalline microtextures show rosettes of opal-CT (lepispheres) in cavities of samples with medium to high d(101)-spacing values. The morphology of lepisphere crystallites grades from bladed to spiny with decreasing d(101)-spacing values, reflecting an internal crystal ordering with increased diagenesis. Further diagenetic changes occurred in a sample with 4.06 A d(101)-spacing where incipient quartz crystals signal the initial conversion of opal-CT to microcrystalline quartz. Silica diagenesis demonstrates that burial temperatures surpassed the range of opal-A to opal-CT conversion and approached conversion temperatures (55/sup 0/C to 110/sup 0/C) of opal-CT to microcrystalline quartz. The conversion occurred when the Santa Cruz Mudstone was buried over 1900 m (depth calculated from a geohistory diagram). This burial temperature brings the Santa Cruz Mudstone within the oil generation window, and could account for the presence of hydrocarbons in the unit.

El-Sabbagh, D.

1987-05-01

193

Modelling Miocene vegetation in Europe: New results of the CARAIB model  

NASA Astrophysics Data System (ADS)

The aim of this study is to present a new simulation of the vegetation with the CARAIB (CARbon Assimilation In the Biosphere) dynamic vegetation model for the Miocene in Europe. During this period, subtropical and tropical species were present in this area due to warmer climatic conditions. In order to better take in consideration these kinds of vegetations, we propose in this work a new classification of 26 groups. This adapted classification and the corresponding climatic tolerance parameters are based on the study of Dubois-Laurent et al. (J. Veg. Sci., 15, 739-746, 2004) for the tree types currently present in Europe, on the distributions of analogue species in south-eastern Asia and on some species distributions around the world. In the new classification 3 groups are devoted to herbs and 15 for trees including cold/cool/warm temperate, subtropical and tropical types. The 8 remaining groups are new ones and concern shrubs from arctic to tropical conditions. The new classification with the addition of shrubs will be used to improve the vegetation simulations with CARAIB for past, present an future periods.

Francois, L.; Favre, E.; Utescher, T.; Suc, J.-P.; Dubois-Laurent, J.-M.; Huang, K.; Cheddadi, R.

2009-04-01

194

Late Miocene teeth from Middle Awash, Ethiopia, and early hominid dental evolution.  

PubMed

Late Miocene fossil hominid teeth recovered from Ethiopia's Middle Awash are assigned to Ardipithecus kadabba. Their primitive morphology and wear pattern demonstrate that A. kadabba is distinct from Ardipithecus ramidus. These fossils suggest that the last common ancestor of apes and humans had a functionally honing canine-third premolar complex. Comparison with teeth of Sahelanthropus and Orrorin, the two other named late Miocene hominid genera, implies that these putative taxa are very similar to A. kadabba. It is therefore premature to posit extensive late Miocene hominid diversity on the basis of currently available samples. PMID:15001775

Haile-Selassie, Yohannes; Suwa, Gen; White, Tim D

2004-03-01

195

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

196

Correlation of Miocene North Sea sequences with the Danish land area based on foraminifera.  

National Technical Information Service (NTIS)

In the present study comparisons are made between the Miocene North Sea sequences and the Danish onshore formations based on foraminiferal biostratigraphy. Foraminiferal faunas of four onshore borings previously analyzed have been reviewed. Biozones NSB 9...

G. V. Laursen F. N. Kristoffersen

1995-01-01

197

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

198

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

199

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

200

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

201

Organic?geochemical characteristics of the Miocene Lycian Basin, western Taurides, Turkey  

Microsoft Academic Search

In the Lycian Basin (SW Turkey), the Miocene Karabay?r and Karaku?tepe formations consist of algal limestone, conglomerate, sandstone, shale and limestone. Total organic carbon (TOC) analysis of the Miocene units show that these formations are poor in organic matter. TOC values are generally between 0.02 and 0.51%, but reach 3.47% in the Karabay?r Formation. Hydrogen indices (HI) are mostly below

O. Özçelik; M. Altunsoy; F. Acar; N. Y. Erik

2009-01-01

202

SEDIMENTOLOGY AND STRATIGRAPHY OF THE UPPER MIOCENE EL BOLEO FORMATION, SANTA ROSALÍA, BAJA CALIFORNIA, MEXICO  

Microsoft Academic Search

The transtensional Upper Miocene Santa Rosalía basin, located in the east-central part of the Baja California Peninsula, consists of almost 500 m of non-marine to marine sedimentary deposits, and interbedded tuffaceous beds. The Santa Rosalía basin is a NW-SE elongated fault-bounded depocenter that records the sedimentation from Upper Miocene to Pleistocene time. The sequence is divided in El Boleo, La

Lucas Ochoa-Landín; Joaquín Ruiz; Thierry Calmus; Efrén Pérez-Segura; Francisco Escandón

203

Miocene paleomagnetism and tectonic setting of the Baja California Peninsula, Mexico  

Microsoft Academic Search

A paleomagnetic pole calculated from 64 virtual geomagnetic poles for Miocene volcanic rocks of the Baja California Peninsula (86.1°N, 142.6°E, alpha95=3.9°), is simular to a reference pole for the North American craton (87°N, 129.7°E, alpha95=3.0°), consistent with the Baja Peninsula having been adjacent to the Mexican mainland in its pre-Gulf of California position from at least early Miocene time to

J. T. Hagstrum; M. G. Sawlan; B. P. Hausback; J. G. Smith; C. S. Grommé

1987-01-01

204

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

PubMed

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

Dong, Wenjiang; Ni, Yongnian; Kokot, Serge

2013-01-11

205

Andean tectonics as a cause for changing drainage patterns in Miocene northern South America  

NASA Astrophysics Data System (ADS)

New data from Neogene strata in northern South America suggest that Miocene tectonism in the northeastern Andes was responsible for the genesis of the Amazon River and changes in the drainage patterns of other major rivers such as the Magdalena and the Orinoco. Here we present a new model for the paleogeographic evolution of northern South America during the Miocene. In the early Miocene, a large part of the drainage of northwest Amazonia was directed northward along the paleo Orinoco river system to a delta in Lake Maracaibo. Uplift of the Eastern Cordillera in the late middle Miocene caused the first development of the Amazon River; however, no connection with the Atlantic was established, and the Amazon fed the paleo Orinoco river system, which drained toward the Caribbean. Substantial Andean uplift in the late Miocene resulted in major changes in paleogeography: the Orinoco changed its course, the Amazon established a connection to the Atlantic, causing the drowning of carbonate platforms, and the Amazon Caribbean connection was closed. Thus the drainage and paleogeography of northern South America in the Miocene were strongly controlled by tectonic movements in the northeastern Andes.

Hoorn, Carina; Guerrero, Javier; Sarmiento, Gustavo A.; Lorente, Maria A.

1995-03-01

206

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

207

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

208

The record of Miocene impacts in the Argentine Pampas  

NASA Astrophysics Data System (ADS)

Argentine Pampean sediments represent a nearly continuous record of deposition since the late Miocene (˜10 Ma). Previous studies described five localized concentrations of vesicular impact glasses from the Holocene to late Pliocene. Two more occurrences from the late Miocene are reported here: one near Chasicó (CH) with an 40Ar/39Ar age of 9.24 ± 0.09 Ma, and the other near Bahía Blanca (BB) with an age of 5.28 ± 0.04 Ma. In contrast with andesitic and dacitic impact glasses from other localities in the Pampas, the CH and BB glasses are more mafic. They also exhibit higher degrees of melting with relatively few xenoycrysts but extensive quench crystals. In addition to evidence for extreme heating (>1700 °C), shock features are observed (e.g., planar deformation features [PDFs] and diaplectic quartz and feldspar) in impact glasses from both deposits. Geochemical analyses reveal unusually high levels of Ba (˜7700 ppm) in some samples, which is consistent with an interpretation that these impacts excavated marine sequences known to be at depth. These two new impact glass occurrences raise to seven the number of late Cenozoic impacts for which there is evidence preserved in the Pampean sediments. This seemingly high number of significant impacts over a 106 km2 area in a time span of 10 Myr is consistent with the number of bolides larger than 100 m expected to enter the atmosphere but is contrary to calculated survival rates following atmospheric disruption. The Pampean record suggests, therefore, that either atmospheric entry models need to be reconsidered or that the Earth has received an enhanced flux of impactors during portions of the late Cenozoic. Evidence for the resulting collisions may be best preserved and revealed in rare dissected regions of continuous, low-energy deposition such as the Pampas. Additionally, the rare earth element (REE) concentrations of the target sediments and impact melts associated with the Chasicó event resemble the HNa/K australites of similar age. This suggests the possibility that those enigmatic tektites could have originated as high-angle, distal ejecta from an impact in Argentina, thereby accounting for their rarity and notable chemical and physical differences from other Australasian impact glasses.

Schultz, Peter H.; Zárate, Marcelo; Hames, Willis E.; Harris, R. Scott; Bunch, T. E.; Koeberl, Christian; Renne, Paul; Wittke, James

2006-05-01

209

Hydrocarbon migration and diagenesis in Miocene marine-shelf deposits  

SciTech Connect

Miocene marine-shelf deposits typically found in the Gulf Coast basin are composed of thin (0.1-10.0 cm), horizontally bedded or cross-stratified quartzarenites to subarkoses, laminated silty clays up to 50 cm thick, and bioturbated admixtures of these 2 end members. Some of the coarser grained sand units may contain appreciable quantities (up to 50%) of shell fragments. These lithotypes exert a significant control on the diagenetic mineral products and amount of secondary porosity observed in specimens that have been subjected to temperatures in excess of 120/sup 0/C. Low-magnesium calcite, maximum microcline, high albite, and a kaolin mineral (possibly dickite) are the major diagenetic products in the sandstones. A regular mixed-layered illite/smectite (rectorite) is dominant in the clay-rich materials. Secondary porosity is most common in those rocks that originally contained numerous shell fragments. Quartz overgrowths are ubiquitous. The diagenetic differences are striking when the closeness of the sand and clay association is considered. The thin clay seams may have obtained small quantities of potassium from some of the associated sands. The sands illustrate considerable reaction with connate fluids, during the albitization process. Kaolinitic minerals are most abundant in the sand with the highest original porosity. The original composition and diagenetic products define the optimum conditions for hydrocarbon migration.

Ferrell, R.E. Jr.; Drew, A.H.

1985-02-01

210

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

211

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

212

Foraminiferal biostratigraphy and paleoenvironments of Eastover Formation (late Miocene), Virginia  

SciTech Connect

Foraminifera from 50 samples taken from the Eastover Formation (Miocene) in Virginia are used in a study of biostratigraphy and paleoecology. The Eastover Formation contains two members: the lower Claremont Manor Member, a clayey, silty, poorly sorted, fine-grained sand which contains abundant foraminifera; and the upper Cobham Bay Member, a well-sorted, shelly, fine-grained sand that contains less abundant foraminifera. Planktonic species are used to establish a biochronology of the Eastover, while benthic species are used to interpret paleoecology, using the distribution of modern foraminifera as a basis. Evidence of changes in environments through time and varying sea margins is searched for by examination of samples taken from vertical sections and samples taken from different geographic locations within the study area. Additional evidence of paleoenvironments is gained by a grain size analysis of sediments from the formation. Synthesis of this information allows for reconstruction of the geologic history of the Eastover Formation in terms of environments changing through time and space. Cluster analysis and canonical variate analysis are used to clarify differences in foraminiferal content between and within the two members and to identify the taxa which cause such differences. Analysis of this type is helpful in revealing and foraminiferal assemblage zones present as well as quantifying data derived from the study.

Goshorn, J.H.

1984-04-01

213

Miocene drowning of temperate (Foramol) carbonate platform: upper Miami Terrace  

SciTech Connect

Oligocene neritic rocks dredged from 350 m on the upper Miami Terrace exhibit repeated phosphatization as well as a filled void system containing post-Burdigalian foraminifera. During drowning, a neritic hardground was subjected to both pelagic deposition (infills) and repeated marine exposure (borings, P-coatings, etc). The neritic grainstone-packstone contains large benthic foraminifera, red algae, bryozoans, pelecypods, ahermatypic corals, echinoids, and some planktonic foraminifera. This composition association is the Foramol type characteristic of temperate to subtropical neritic environments such as the present Mediterranean, Brazilian, and New Zealand shelves. These temperate sediments derive from the local biocoenose, and accumulate slowly in deep sheets of loose skeletal debris. They become relict seaward where they are often bored, corroded, stained, glauconitized, and cemented into hardgrounds. Locally, hemipelagic cover might produce a palimpsest sequence. Recent Foramol-type platforms are undergoing drowning. The Miami Terrace is compared to very similar Miocene Foramol-type platforms now exposed in the southern Apennines. Both are characterized by neritic sequences passing upward into hemipelagics, via a palimpsest interval marked by glauconitic, phosphatic, iron-stained grains often mineralized into hardgrounds. The drowning of the Miami Terrace hence coincided with and, the authors suppose, was a result of the shift from a rapid, oligotrophic, tropical accumulation to a slow, temperate, eutrophic carbonate accumulation caused in turn by a temporary paleo-oceanographic shift to cooler, richer, neritic conditions within the history of this now subtropical setting.

Carannante, G.; Simone, L.; Neumann, C.

1986-05-01

214

The biostratigraphic basis for Gulf Coast Miocene sequence stratigraphy  

SciTech Connect

A chronostratigraphic framework was developed as a prelude to a regional sequence stratigraphic and associated systems tracts analysis of the offshore Louisiana and Texas Miocene. The integrated data base for this study included over 10,000 line mi of seismic data, 230 wireline logs, and detailed biostratigraphic analyses on 35 wells. The objective of the study was to map systems tracts and facies that may help delineate prospective areas. Because they are a fundamental stratigraphic unit within a sequence, this framework emphasizes condensed sections and their calibration by microfossil highest occurrence datums. Condensed sections have been delineated utilizing planktonic foraminiferal and calcareous nannofossil abundance and species diversity patterns, as well as detailed paleo-water depth determinations based on benthic foraminiferal biofacies. Pitfalls in the use of condensed sections may arise in shallow paleoshelf settings where datums may be unreliable, and in deeper environments where multiple abundance/diversity peaks may occur. However, an event stratigraphic scheme is generally the most satisfactory method for overcoming correlation problems inherent in the Gulf Coast unstable prograding shelf margin.

Shaffer, B.L.; Pacht, J.A.; Bowen, B.E. (Calibre Consulting Services, Inc., Houston, TX (United States))

1991-03-01

215

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

2012-01-05

216

The Quilon Limestone (Kerala Basin/India) - an archive for Miocene Indo-Pacific seagrass beds  

NASA Astrophysics Data System (ADS)

The Quilon Formation of the Kerala Basin (SW India) is characterized by carbonate rocks which belong to the Warkalli Group and are interbedded between siliciclastic formations. It comprises at least 2 horizons of fossiliferous limestone with marine fauna. The lower limestone horizon is characterized by colonial corals, while the upper horizon represents a larger foraminiferal Pseudotaberina malabarica facies which is well developed at the type locality, the coastal cliffs of Ashtamudi Lake at Padappakkara in SW India. The sediment there is either a weakly cemented carbonate sand rich in foraminifers and gastropods or a fossiliferous limestone. Facies and faunal composition clearly indicate a seagrass environment. Recent seagrasses have their centre of generic richness in the Indo-Pacific where they cover wide areas in the tidal and shallow subtidal zones. However, their geological record is only fragmentary and their palaeobiogeographic record has a big gap in the Western Indo-Pacific region. The newly reported nannoplankton flora and planktonic foraminifers from the Quilon Formation demonstrate that the deposition of the studied seagrass bed occurred in nannoplankton biozone NN3. This timing suggests a formation during the closure of the Tethyan Seaway. It designates the Quilon Limestone as an early Western Indo-Pacific seagrass bed and documents an important step in the history of seagrass communities. The large discoidal soritid foraminifer Pseudotaberina malabarica is considered as proxy for Miocene seagrass communities in the Indo-Pacific region.

Piller, Werner E.; Reuter, Markus; Harzhauser, Mathias; Kroh, Andreas; Rögl, Fred; Coric, Stjepan

2010-05-01

217

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

218

Apatite fission-track data for the Miocene Arabia-Eurasia collision  

NASA Astrophysics Data System (ADS)

The collision between the Eurasian and Arabian plates along the 2400-km-long Bitlis-Zagros thrust zone isolated the Mediterranean from the Indian Ocean and has been linked to extension of the Aegean, rifting of the Red Sea, and the formation of the North and East Anatolian fault systems. However, the timing of the collision is poorly constrained, and estimates range from Late Cretaceous to late Miocene. Here, we report the first apatite fission track (AFT) ages from the Bitlis-Zagros thrust zone. The AFT samples are distributed over the 450 km length of the Bitlis thrust zone in southeast Turkey and include metamorphic rocks and Eocene sandstones. Despite the disparate lithology and large distance, the AFT ages point consistently to exhumation in the Early to Mid Miocene between 18 and 13 Ma. Tectonostratigraphic analysis of sedimentary successions along the facing converging margins of the Arabian and Eurasian plates can provide additional constraints on the timing of collision. Along the northern margin of the Arabian plate in southeast Anatolia, widespread shallow-marine carbonate deposition during the Eocene was followed by an Oligocene regression, and Oligocene deposits are missing over much of the region. A marine transgression at the beginning of the Miocene led to the deposition of Lower Miocene (Aquitanian-Burdigalian) reefal carbonates, which crop out close to the Bitlis thrust zone. The carbonates pass upward and northward to siliciclastic marine turbidites, again of Lower Miocene age. The turbidites, which are 800 m thick, were deposited in a peripheral foreland basin during its phase of underfilling and are at present partly overthrust by the Bitlis Massif and the Eocene series. The Lower Miocene series represent the last marine sequence on the northern margin of the Arabian plate and are followed by the deposition of continental conglomerate, sandstone and evaporites of late Miocene-Pliocene age. North of the Bitlis suture in the eastern Anatolia on the Eurasian plate, a thick succession of Oligocene turbidites crops out north of Mu?; these are overlain by shallow marine sandstone, shale, and limestone of early Miocene (Aquitanian-Burdigalian) age. The Oligocene-Miocene succession was deposited in a retroarc foreland basin associated with northward subduction of the Arabian plate. Lower Miocene (Lower Burdigalian) shallow-marine limestones also crop out widely west of Lake Van, where they are unconformably overlain by Pliocene to Holocene volcanic rocks. The AFT ages, along with an appraisal of regional stratigraphy, indicate that the last oceanic lithosphere between the Arabian and Eurasian plates was consumed by the early Miocene (ca. 20 Ma). The early to mid-Miocene Arabia-Eurasia collision supports a temporal link between collision and the formation of the late Miocene North Anatolian fault. However, extension in the Aegean domain, related to the slab retreat, dates back to the Oligocene. This and the recent recognition of major Oligocene dextral strike-slip faults in Anatolia suggest that the westward translation of Anatolia started in the Oligocene and predated the Miocene Arabia-Eurasia collision.

Okay, Aral; Zattin, Massimiliano; Cavazza, William

2010-05-01

219

Miocene ungulates and terrestrial primary productivity: Where have all the browsers gone?  

PubMed Central

Progressive changes are observed in both the composition of mammal faunas and vegetation during the Miocene epoch [24–5 mega-annum (Ma)]. These changes are usually interpreted as a response to climatic changes. In the traditional view, forests or woodlands gradually gave way to more open habitats, with grazing (grass-eating) ungulate (hoofed) mammal species replacing the browsing (leafy-vegetation-eating) species as grasslands expanded. However, data from fossil assemblages in the Great Plains region of North America show that this faunal change was not a one-for-one replacement of browsers by grazers, as usually thought. Typical late early Miocene (17 Ma) fossil communities included extraordinarily high numbers of browsing ungulate species, comprising a fauna that cannot be directly analogized with any present-day community. Both maximum species richness of all ungulates and the proportion of browsers declined steadily in ungulate communities through the middle Miocene, to levels comparable to those of the present by the late Miocene. The resulting dramatic, cumulative loss of browsing species constitutes one of the strongest faunal signals of the late Tertiary (but was not a single “event”). We suggest that the early Miocene browser-rich communities may reflect higher levels of primary productivity in Miocene vegetation, compared with equivalent present-day vegetation types. The observed decline in species richness may represent a gradual decline in primary productivity, which would be consistent with one current hypothesis of a mid-Miocene decrease in atmospheric CO2 concentrations from higher mid-Cenozoic values.

Janis, Christine M.; Damuth, John; Theodor, Jessica M.

2000-01-01

220

Regional biostratigraphy and paleoenvironmental history of Miocene of onshore and offshore Alabama  

SciTech Connect

Subsurface Miocene sediments of coastal Alabama and the adjoining state and federal waters consist of a clastic wedge varying in thickness from less than 1,000 ft in southern Alabama to a maximum of about 6,000 ft in the northeastern portion of the Main Pass area. Relatively deep-water and open-marine transgressive basal Miocene clays and shales unconformably overlie a gently southwestward-dipping late Oligocene-earliest Miocene carbonate platform. Middle and late Miocene sediments consist of a regressive offlapping sequence of sand and shale deposited in varying neritic paleoenvironments. Analysis of planktonic and benthonic foraminifera has resulted in a refined biostratigraphic zonation of these sediments, permitting the recognition of several regional time-equivalent datum levels, or biohorizons. These biohorizons are shown on a series of subsurface cross sections that show the dramatic southwestward thickening of middle and late Miocene sediments as well as illustrate the relationships of the producing intervals within the Cibicides carstensi and Discorbis 12 interval zones. The paleoenvironmental history of the Miocene has been reconstructed on a series of paleobathymetric maps drawn for selected regional biohorizons. Among other features, these maps have proven the existence and outlined the margins of previously unrecognized shallow-meritic deltaic sediments in southeastern Mobile County and in the Chandeleur and Viosca Knoll (north) areas. Analysis of sedimentation rates, which range from less than 25 to 1,370 ft/m.y., further aids in understanding the coastal shelf, deltaic, and open-marine depositional history of the Miocene of Alabama and the adjoining state and federal waters.

Smith, C.C. (Geological Survey of Alabama, Tuscaloosa (USA))

1989-09-01

221

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

NASA Astrophysics Data System (ADS)

The Rabigh area, a coastal region north of Jeddah city, Saudi Arabia contains raised Quaternary coral reefal terraces and reworked coral fragments mixed with sand and gravel. This area has a thin exposure Lower Miocene shallow marine carbonate rocks that laterally pass into evaporites. The Miocene carbonate and evaporite rocks conformably overly the Lower Miocene siliciclastic sequence, are in turn capped by the Harrat basaltic boulders. The Miocene carbonates are made up of dolomitic packstone, wackestone and mudstone, whereas the overlying Quaternary reefal terraces are composed of coral boundstone and grainstones.

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

2013-11-01

222

Miocene Coral Skeleton Rare Earth Element Patterns Reflect River Discharge  

NASA Astrophysics Data System (ADS)

Rare Earth Element (REE) patterns of modern coral skeletons usually reflect the REE composition of ambient seawater which is characterized by heavy REE enriched relative to light REE with NASC (North American Shale Composite) normalized La/Lu ratios of typically <0.4. The REE concentration in coral aragonite is enriched by 3 to 4 orders of magnitude compared to ambient seawater. Here we report trace element data including REE of coral skeletons of Late Miocene age (~9 Ma, Tortonian) from Crete (Eastern Mediterranean). Analyses were done using a 213 nm Nd:YAG laser coupled to an Element2 ICP-MS along the growth axis of the coral skeletons. The profiles show that Ba/Ca ratios have a seasonally induced pattern with high values around the winter months which are identified by ?18O analyses. REE/Ca ratios co-vary with Ba/Ca ratios. Since the Ba/Ca ratio is a proxy used to monitor river discharge, the co-variation suggests the REE/Ca ratio to be a proxy of comparable quality. NASC-normalized REE patterns of the Tortonian corals have negative Ce anomalies like modern corals. However, the Tortonian corals have REE patterns highly enriched in LREE with (La/Lu)N ratios of 4 to 30 which is 1 to 2 orders of magnitude higher compared to modern corals. Al concentrations are low (<10 ppm) and do not correlate with REE concentrations indicating an insignificant fraction of terrigenous material included in the skeleton. Applying distribution coefficients typical for modern corals, the REE composition of the Tortonian ambient water yields (La/Lu)N of about 2 to 16. This range can be explained by binary mixing of modern Eastern Mediterranean sea surface water ((La/Lu)N=0.35, sea surface salinity (SSS) ~38 ‰) with highly LREE-enriched river water ((La/Lu)N >3, salinity ~0.5 ‰) transporting suspended and colloid phases, also highly enriched, especially in LREE, at a ratio of ~9 (seawater):1 (river water). The river water component is considered because paleoenvironmental reconstructions suggest the reef to have grown close to a river mouth. The calculated mixing ratio corresponds to a SSS of the ambient water >34 ‰ compatible with environmental conditions favorable for coral growth. As possible sources of the REE transported by river water, weathering products of Cretan hinterland rocks must be considered. During the Miocene, drained hinterland was formed by a diversity of magmatic, metamorphic and sedimentary lithologies, essentially represented by granitoids, ophiolitic rocks, siliciclastic sediments and carbonates. A detailed identification of sources as well as quantification of corresponding fractions of REE contributing to the bulk river water component is principally possible in cases where the drained system shows a more limited variation in rock lithologies, however, is difficult to apply to the complex Cretan situation. This study demonstrates that the REE patterns of coral skeletons can be suitable to reconstruct the bulk REE composition of the drainage system in the reef’s hinterland. Also, we suggest to use REE/Ca and Ba/Ca ratios likewise in order to identify fluctuations in river discharge to marine environments.

Mertz-Kraus, R.; Brachert, T. C.; Jochum, K. P.

2010-12-01

223

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

SciTech Connect

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

Orzag-Sperber, F.; Rouchy, J.M. (Universite Paris XI, Orsay (France))

1988-08-01

224

Effect of abyssal circulation changes on Oligocene to Miocene benthic foraminifera in the North Atlantic  

SciTech Connect

Benthic foraminiferal ranges at western North Atlantic Sites 563 and 558 show: 1) gradual Oligocene last occurrences in response to subsidence from the upper to lower abyssal zones; 2) a preponderance of extinctions in the early middle Miocene (about 15.5-13.5 Ma). Comparison of relative and absolute abundance changes at Site 563 sows that percentages of some taxa (e.g. Nuttallides umbonifera) reliably reflect their accumulations while percentages of others vary independently. Regional abundance changes include: 1) maxima N. umbonifera in the middle Oligocene of the deepest sites (10 and 119); 2) increased Planulina wuellerstorfi in the early middle Miocene; 3) increased N. umbonifera in the late middle Miocene. Seismic stratigraphic and delta/sup 13/C evidence indicates a northern bottom-water source for the North Atlantic throughout much of the Oligocene and Miocene. Benthic foraminifera apparently responded to bottom-water changes inferred from carbon isotopic comparisons. The extinction of relict Paleogene taxa and the ascendancy of P. wuellerstorfi in the middle Miocene apparently correlate with increased advection into the eastern Atlantic, subsidence of the Iceland-Faeroe Ridge and increased North Atlantic carbonate sedimentation. The authors speculate that this faunal reorganization was in response to global ocean chemistry changes resulting from increased ventilation of the North Atlantic.

Katz, M.E.; Miller, K.G.

1985-01-01

225

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

SciTech Connect

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

Sari, A.; Geze, Y. [Ankara University, Ankara (Turkey). Faculty of Engineering

2008-07-01

226

Distribution history and climatic controls of the Late Miocene Pikermian chronofauna  

PubMed Central

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

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

2009-01-01

227

The flora of the early Miocene Brandon Lignite, Vermont, USA. VIII. Caldesia (Alismataceae).  

PubMed

Caldesia, a genus of aquatic monocotyledons, is represented by four living species, which are widely distributed in the temperate and tropical Old World. The genus has an extensive Oligocene through Pleistocene fossil record in Eurasia. We survey the morphology of the extant and fossil fruits of the Alismataceae, and provide a detailed review of the morphology and anatomy of living and fossil Caldesia fruits. The latter exhibit substantial similarity, making the recognition of separate species on the basis of fruit morphology difficult. We erect the new species Caldesia brandoniana from the Early Miocene Brandon Lignite of Vermont primarily on the basis of its geographic isolation; careful revision of all fossil fruiting material of Caldesia might require placement of the Brandon specimens in a more inclusive form species. Together with leaves of Caldesia from the Miocene Clarkia flora of Idaho, this occurrence indicates that Caldesia was in the New World as recently as the Early Miocene. PMID:21712204

Haggard, K; Tiffney, B

1997-02-01

228

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

229

Relation of peralkaline magmatism to heterogeneous extension during the Middle Miocene, southeastern Nevada  

USGS Publications Warehouse

Volcanism migrated southward in the northern Basin and Range province in the Oligocene and early Miocene to produce voluminous calcalkaline silicic ash flow tuffs. Alkaline volcanism became dominant by middle Miocene (17-14 Ma) as smaller volumes of rhyolite-trachyte-basalt suites were erupted from the relatively small Kane Springs Wash caldera complex in southeastern Nevada. Only minor extension affected the Kane Wash area before the end of calcalkaline activity, but extension expressed by rate of progressive stratal tilt peaked (15-13.5 Ma) with peralkaline magmatism (14.7-14.4 Ma). Variations in distribution, degree, style, and timing of deformation demonstrate heterogeneous extension in the Kane Wash area. Only minor extension and tilting persisted post-middle Miocene (<12 Ma). All major eruptive sources overlap domains of rapid extension. -from Authors

Scott, R. B.

1995-01-01

230

Geochemical characteristics of the Miocene eolian deposits in China: Their provenance and climate implications  

NASA Astrophysics Data System (ADS)

In the Loess Plateau in northern China, the Quaternary loess-soil sequences, the Hipparion Red Earth of eolian origin (Red Clay), and the Miocene loess-soil sequences constitute a near-continuous terrestrial record of paleoclimates for the past 22 Ma. In this study, Miocene loess and paleosol samples from Qinan (QA-I) were analyzed for their major, trace, and rare earth element chemistry and compared with the Plio-Pleistocene samples from Xifeng with emphasis on their provenance and paleoclimatic implications. The results show similar geochemical signatures for the eolian deposits of different ages, and they are also comparable to the average composition of the upper continental crust. These suggest that the dust materials were all derived from well-mixed sedimentary protoliths which had undergone numerous upper crustal recycling processes. They also support the notion of broadly similar source areas and dust-transporting trajectories for different periods since the early Neogene. The slightly higher K2O, Fe2O3, and MgO concentrations and loss on ignition values and the lower Na2O content in the Miocene loess samples compared to their Quaternary counterparts are attributable to the finer grain size of the Miocene loess associated with weaker dust-carrying winds. In comparison with some loess in Europe and America with less extensive sources, eolian deposits from northern China show higher Cs and lower Zr and Hf content. This is attributable to the sorting processes from remoter sources during transportation and could be regarded as an indication of the desert origin of the loess deposits. Miocene paleosol samples show higher chemical index of alteration values and lower CaO, MgO, and Na2O concentrations than does the intervening loess, indicating stronger weathering of the paleosols. However, the moderate chemical weathering of the paleosol samples indicates a constant semiarid and subhumid climatic range in northern China since the early Miocene.

Liang, Meiyan; Guo, Zhengtang; Kahmann, A. Julia; Oldfield, Frank

2009-04-01

231

The evolution of pCO2, ice volume and climate during the middle Miocene  

NASA Astrophysics Data System (ADS)

The middle Miocene Climatic Optimum (17-15 Ma; MCO) is a period of global warmth and relatively high CO2 and is thought to be associated with a significant retreat of the Antarctic Ice Sheet (AIS). We present here a new planktic foraminiferal ?11B record from 16.6 to 11.8 Ma from two deep ocean sites currently in equilibrium with the atmosphere with respect to CO2. These new data demonstrate that the evolution of global climate during the middle Miocene (as reflected by changes in the cyrosphere) was well correlated to variations in the concentration of atmospheric CO2. What is more, within our sampling resolution (˜1 sample per 300 kyr) there is no evidence of hysteresis in the response of ice volume to CO2 forcing during the middle Miocene, contrary to what is understood about the Antarctic Ice Sheet from ice sheet modelling studies. In agreement with previous data, we show that absolute levels of CO2 during the MCO were relatively modest (350-400 ppm) and levels either side of the MCO are similar or lower than the pre-industrial (200-260 ppm). These new data imply the presence of either a very dynamic AIS at relatively low CO2 during the middle Miocene or the advance and retreat of significant northern hemisphere ice. Recent drilling on the Antarctic margin and shore based studies indicate significant retreat and advance beyond the modern limits of the AIS did occur during the middle Miocene, but the complete loss of the AIS was unlikely. Consequently, it seems that ice volume and climate variations during the middle Miocene probably involved a more dynamic AIS than the modern but also some component of land-based ice in the northern hemisphere.

Foster, Gavin L.; Lear, Caroline H.; Rae, James W. B.

2012-08-01

232

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

233

Changes in Deep Water Circulation in the Pacific during and after the Miocene carbonate crash based on Nd isotopes  

Microsoft Academic Search

Shoaling of the Isthmus of Panama and onset of Northern Component Water (NCW) production affected circulation patterns in the eastern Pacific Ocean and has been proposed as the cause of the middle Miocene carbonate crash in this region. To better understand the impact of these events on circulation we have constructed Nd isotopic records from the middle Miocene to Pliocene

D. Newkirk; E. E. Martin

2009-01-01

234

Facies partitioning and sequence stratigraphy of cool-water, mixed carbonate-siliciclastic sediments (Upper Miocene Guadalquivir Domain, southern Spain)  

Microsoft Academic Search

During the late Miocene, the Guadalquivir Basin and its satellite basin, the Ronda Basin, were under Atlantic cool-water influence. The aim of our study is to develop a sequence stratigraphic subdivision of the Ronda Basin fill and to provide models for the cool-water carbonates. The Upper Miocene of the Ronda Basin can be divided into three depositional sequences. Sequence 1

I. Gläser; C. Betzler

2002-01-01

235

Hyaenictitherium minimum, a new ictithere (Mammalia, Carnivora, Hyaenidae) from the Late Miocene of Toros-Menalla, Chad  

Microsoft Academic Search

A new species of Hyaenidae, Hyaenictitherium minimum, is described in the carnivore fauna of the Late Miocene layers of Toros-Menalla (Chad). Its size is similar to that of a jackal and it had probably a similar ecological niche. It is found in several fossil-bearing localities of this area. The genus Hyaenictitherium is known from the early Late Miocene in Eurasia

Louis de Bonis; Stéphane Peigné; Andossa Likius; Hassane Taïsso Mackaye; Patrick Vignaud; Michel Brunet

2005-01-01

236

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

237

Miocene-Early Pliocene diatomaceous sedimentation patterns in the Pacific: A response to paleooceanography and paleoclimatic change  

Microsoft Academic Search

Biosiliceous sediments greatly expanded their distribution in the North Pacific during the late early to early middle Miocene (18-15 Ma), at least partly due to enhanced basin-basin fractionation of deep waters between the North Atlantic and North Pacific, which began in 17 Ma. Subsequently, in the late middle and late Miocene, diatomaceous sedimentation responded to the following series of successive

John A. Barron

1990-01-01

238

Location of the River Euphrates in the Late Miocene; dating of terrace gravel at Shireen, Syria  

NASA Astrophysics Data System (ADS)

We report gravel of the River Euphrates, capped by basalt that is Ar-Ar dated to ~9 Ma, at Shireen in northern Syria. This gravel, preserved by the erosion-resistant basalt, allows us for the first time to reconstruct the history of this major river during the Late Miocene. In response to progressive regional surface uplift, the Euphrates extended SE by ~800 km between the early Middle Miocene, when the coast was near Kahramanmara? in southern Turkey, and the Pliocene, when it lay in western Iraq, east of the Arabian Platform uplands.

Demir, T.; Pringle, M.; Yurtmen, S.; Westaway, R.; Bridgland, D.; Beck, A.; Challis, K.; Rowbotham, G.

2007-04-01

239

Location of the River Euphrates in the Late Miocene; dating of terrace gravel at Shireen, Syria  

NASA Astrophysics Data System (ADS)

We report gravel of the River Euphrates, capped by basalt that is Ar-Ar dated to 9 Ma, at Shireen in northern Syria. This gravel, preserved by the erosion-resistant basalt, allows us for the first time to reconstruct the history of this major river during the Late Miocene. In response to progressive regional surface uplift, the Euphrates extended SE by 800 km between the early Middle Miocene, when the coast was near Kahramanmara?in southern Turkey, and the Pliocene, when it lay in western Iraq, east of the Arabian Platform uplands.

Demir, T.; Pringle, M.; Yurtmen, S.; Westaway, R.; Bridgland, D.; Beck, A.; Challis, K.; Rowbotham, G.

2006-12-01

240

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

NASA Astrophysics Data System (ADS)

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.

McLean, Hugh; Howell, D. G.

1984-06-01

241

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

NASA Astrophysics Data System (ADS)

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

Engel, Michael S.; Gross, Martin

2009-02-01

242

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

243

The earliest record of birch mice from the Early Miocene Nei Mongol, China  

NASA Astrophysics Data System (ADS)

The earliest species of birch mouse, Sicista primus sp. nov., was recovered from the 17-Ma-old (Early Miocene) Gashunyinadege locality, central Nei Mongol, China. It is ~9 Ma older than the previous first appearance datum of Sicista in Eurasia. This study indicates that North American Macrognathomys is a synonym of Eurasian Sicista, having 12 shared dental characters. As a result, the biogeography of dipodids indicates that Asian Sicista dispersed to North America as opposed to the hypothesis that Sicista originated from the North American clade. Sicista is one of the few extant rodent genera that originated as early as the Early Miocene.

Kimura, Yuri

2011-01-01

244

From transpression to transtension: Oligocene-Miocene structural evolution of the Vienna basin and the East Alpine-Western Carpathian junction  

Microsoft Academic Search

Palaeostress analysis in the easternmost Alps and westernmost Carpathians revealed the existence of four different stress fields during Oligocene-Miocene times. The generalized Oligocene-late Middle Miocene maximal horizontal stress axis changes gradually from WNW-ESE to ENE-WSW and the Late Miocene axis trends to NNE-SSW. Except for the late Middle Miocene (late Sarmatian, 11 Ma) weak, transient stress field, the others reflect

L. Fodor

1995-01-01

245

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

246

Paleomagnetic Study of a Miocene Deformation in a Region Close to the Camargo Volcanic Field, Chihuahua, Mexico  

NASA Astrophysics Data System (ADS)

The Sierra the Aguachile is a Miocene volcanic sequence located in the SE of Chihuahua State NW of the Camargo volcanic field and belongs to the Agua Mayo Group, which unconformably overlays Mesozoic calcareous units. The Sierra de Aguachile sequence defines a structure that may be interpreted as a plunging fold, which could be the result of a reactivation of the San Marcos Fault. This major fault is well known more to the east but may extend into the study area where it would be covered by the younger volcanic sequences; its main activity has been reported to be during the the Neocomian with reactivation phases in the Paleogene and Miocene. To test if the observed structure is the result of a tectonic deformation that happened after the emplacement of the volcanic sequence, a paleomagnetic study was carried out. A total of 14 sites were sampled from different parts of the structure, all in the capping ignimbrite layers. Site mean directions were determined using AF demagnetization. The fold test was applied to analyze if the remanence was acquired in situ or before the proposed folding. Precision parameters k before and after application of the tectonic corrections are 25.38 and 31.43, respectively. This indicates that the Sierra de Aguachile indeed was folded after emplacement of the ignimbrites, which restricts the age of the corresponding tectonic event to be younger than 31.3 +/- 0.7 Ma. Due to the gentle folding though, the difference in precision parameters is not significant at the 95% probability level.

Wogau-Chong, K.; Bohnel, H.; Aranda Gomez, J.

2009-05-01

247

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

248

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

249

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

250

Tracking Arabia-India motion from Miocene to Present  

NASA Astrophysics Data System (ADS)

Although small, the present-day Arabia-India motion has been captured by several global and regional geodetic surveys that consistently show dextral motion of a few mm/yr, either transpressive or transtensive (Fournier et al., 2008). This motion is accommodated along the Owen Fracture Zone, an active strike-slip boundary that runs for more than 700 km from the Somalia-India-Arabia triple junction in the south to the Dalrymple trough in the north. Two recent marine cruises conducted along this fault aboard the BHO Beautemps-Beaupré (AOC 2006 and OWEN 2009) using a high resolution multibeam sounder (Simrad EM120, 10 m vertical resolution) provided a complete map of the active fault and confirmed a present-day pure dextral motion. The surface breaks closely follow a small circle of the Arabia-India motion, with several pull-part basins at the junctions between the main segments of the fault. Geomorphologic offsets reach 10 km, suggesting that the mapped fault has been active with the same style for past several million years. When did this motion start? The difficulty in tracking the past Arabia-India motion is that there is no direct kinematic indicator available, since the boundary has been strike-slip and/or convergent during the Tertiary. Motion was most probably sinistral during the rapid northward travelling of India towards Eurasia in the early Tertiary, Arabia being rigidly attached to Africa until the opening of the Gulf of Aden. However, the nature and location of the Arabia-India boundary at that time remain speculative. Throughout the Miocene, the relative motion between India and Arabia has been indirectly recorded at the Sheba and Carslberg ridges, the former recording Arabia-Somalia motion (opening of the Gulf of Aden) and the latter India-Somalia motion (Indian Ocean opening). Both ridges have been studied with some details recently, using up to date magnetic lineations identification (Merkouriev and DeMets, 2006; Fournier et al., 2009). We combine these studies to derive Arabia/India kinematics for the past 20 Myrs. As observed today, opening rates at Sheba ridge and at Carlsberg ridge remained closed since Chron 5D (17.2 Ma), thus pointing to small differential motion between Arabia and India. However, our kinematic model suggests that dextral shearing prevailed since the very beginning of opening of the Gulf of Aden. This has significant implications for the forces that drive the Arabia plate and Arabia-India coupling at their transform boundary. Fournier et al., 2008, In-situ evidence for dextral active motion at the Arabia-India plate boundary, Nature Geoscience, doi:10.1038/ngeo.2007.24. Fournier et al., 2009, Arabia-Somalia plate kinematics, evolution of the Aden-Owen-Carlsberg triple junction, and opening of the Gulf of Aden, J. Geophys. Res., in revision. Merkouriev and DeMets, 2006, Constraints on Indian plate motion since 20 Ma from dense Russian magnetic data: Implications for Indian plate dynamics, Geochem. Geophys. Geosyst., doi:10.1029/2005GC001079.

Chamot-Rooke, N. R.; Fournier, M.

2009-12-01

251

Astronomical forcing of sedimentary cycles in the middle to late Miocene continental Calatayud Basin (NE Spain)  

Microsoft Academic Search

A high-resolution cyclostratigraphic and magnetostratigraphic study was carried out on cyclically bedded successions of middle Miocene lacustrine to distal alluvial fan-floodplain deposits from the Calatayud basin, in northeast Spain. Eight (partially overlapping) subsections near the village of Orera are correlated in detail using distinct sedimentary cycle patterns or by following marker beds in the field. Together they form the Orera

H. Abdul Aziz; F. J. Hilgen; W. Krijgsman; E. Sanz; J. P. Calvo

2000-01-01

252

Fruits and Leaflets of Wisteria (Leguminosae, Papilionoideae) from the Miocene of Shandong Province, Eastern China  

Microsoft Academic Search

Well-preserved legume fruits and associated leaflets are described from the middle Miocene Shanwang Formation of Shandong Province, eastern China. They are assigned to the extant temperate genus Wisteria (Leguminosae, Papilionoideae), which is a deciduous climbing vine native to eastern Asia and eastern North America. Wisteria is one of many genera with an eastern Asian and eastern North American disjunct distribution.

Qi Wang; David L. Dilcher; Terry A. Lotty

2006-01-01

253

Late Eocene to early Miocene ice sheet dynamics and the global carbon cycle  

Microsoft Academic Search

Paired benthic foraminiferal trace metal and stable isotope records have been constructed from equatorial Pacific Ocean Drilling Program Site 1218. The records include the two largest abrupt (<1 Myr) increases in the Cenozoic benthic oxygen isotope record: Oi-1 in the earliest Oligocene (?34 Ma) and Mi-1 in the earliest Miocene (?23 Ma). The paired Mg\\/Ca and oxygen isotope records are

C. H. Lear; Y. Rosenthal; H. K. Coxall; P. A. Wilson

2004-01-01

254

A new species of hippopotamus Hexaprotodon lothagamensis (Mammalia: Hippopotamidae) from the late Miocene of Kenya  

Microsoft Academic Search

A new small to medium-sized hippopotamus, Hexaprotodon lothagamensis is described from the late Miocene of northern Kenya. The material was recovered from Lothagam, a site southwest of Lake Turkana. This narrow-muzzled hippopotamus differs from other Hexaprotodon species in terms of its small size and shallow symphysis. The six incisors are arranged in a straight line across the front of the

E. M. Weston

2000-01-01

255

Miocene stable isotope record: a detailed deep Pacific Ocean study and its paleoclimatic implications  

Microsoft Academic Search

Deep Sea Drilling Project site 289 in the western equatorial Pacific has yielded an extremely detailed record of the carbon and oxygen isotopic changes in the Miocene deep ocean. The isotopic record reflects major changes in paleoclimate and paleoceanography, probably dominated by a major phase of Antarctic ice-cap growth.

F. Woodruff; S. M. Savin; R. G. Douglas

1981-01-01

256

Morphology of hydrocarbon droplets during migration: Visual example from the Monterey Formation (Miocene), California  

Microsoft Academic Search

In this paper, we describe the various morphologies of hydrocarbon residue found in the Miocene Monterey Formation in California. Scanning electron microscope photomicrographs clearly show various shapes of hydrocarbon droplets in microchannels in the Monterey Formation and hence provide insight not only into the shape of hydrocarbon droplets during migration, but also about the migration pathways themselves. The small (5-10

G. D. Thyne; R. M. Slatt

1996-01-01

257

Middle Miocene vertebrates from the Amazonian Madre de Dios Subandean Zone, Perú  

NASA Astrophysics Data System (ADS)

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

Antoine, Pierre-Olivier; Roddaz, Martin; Brichau, Stéphanie; Tejada-Lara, Julia; Salas-Gismondi, Rodolfo; Altamirano, Ali; Louterbach, Mélanie; Lambs, Luc; Otto, Thierry; Brusset, Stéphane

2013-03-01

258

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

259

Late Miocene–Early Pliocene temperature estimates in Europe using rodents  

Microsoft Academic Search

Studies of mammal communities, and in particular of rodents, provide useful information on palaeoenvironments and palaeoclimates. Based on the relationship between species richness and climatic parameters, we propose three models, using arvicolines, murines or sigmodontines in order to quantify past temperatures. Based on rodents, temperatures are estimated here for Late Miocene–Early Pliocene (MN 9 to MN 15) European faunas at

Sophie Montuire; Olivier Maridet; Serge Legendre

2006-01-01

260

Further observations on the primate community at Rudabánya II (late Miocene, early Vallesian age), Hungary  

Microsoft Academic Search

It has been proposed that the pliopithecid Anapithecus hernyaki was hunted by the ape Dryopithecus brancoi based on analyses of the age and sex distribution of 25 individuals from the late Miocene site of Rudabánya, Hungary (ca. 10Ma). In this study, the minimum number of individuals (MNI) and age distribution of the assemblage are recalculated and considered in relation to

Miranda Armour-Chelu; Peter Andrews; Raymond L. Bernor

2005-01-01

261

Recent Advances on Multidisciplinary Research at Rudabánya, Late Miocene (MN9), Hungary: a compendium  

Microsoft Academic Search

Rudabánya is a rich late Miocene fossil locality first exploited for its vertebrate remains by Pethö in 1902. The first fossil primate was discovered by the local Chief Mining Geologist, Gabor Hernyák. Professor Miklos Kretzoi made Rudabánya famous in 1969 by publishing a manuscript on the new hominoid primate, Rudapithecus hungaricus, recognized herein as Dryopithecus brancoi. In 1991 L. Kordos

RAYMOND L. BERNOR; LÁSZLÓ KORDOS; LORENZO ROOK; JORDI AGUSTÍ; P ETER ANDREWS; MIRANDA ARMOUR-CHELU; DAVID R. BEGUN; DAVID W. C AMERON; JOHN DAMUTH; GUDRUN DAXNER-HÖCK; LOUIS DE BONIS; OLDRICH FEJFAR; NARDOS FESSAHA; MIKAEL FORTELIUS; JENS FRANZEN; MIHÁLY GASPARIK; ALAN GENTRY; KURT HEISSIG; GABOR HERNYAK; THOMAS KAISER; GEORGE D. KOUFOS; ENDRE KROLOPP; DÉNES JÁNOSSY; MANUEL LLENAS; PAL MÜLLER; PAUL RENNE; SEVKET SEN; ROBERT SCOTT; ZBIGNIEW SZYNDLAR; PETER S. UNGAR; TORSTEN UTESCHER; JAN A. VAN DAM; LARS WERDELIN; REINHARD ZIEGLER

2006-01-01

262

Miocene stable isotope record: a detailed deep Pacific Ocean study and its paleoclimatic implications  

SciTech Connect

Deep Sea Drilling Project site 289 in the western equatorial Pacific has yielded an extremely detailed record of the carbon and oxygen isotopic changes in the Miocene deep ocean. The isotopic record reflects major changes in paleoclimate and paleoceanography, probably dominated by a major phase of Antarctic ice-cap growth.

Woodruff, F. (Univ. of Southern California, Los Angeles); Savin, S.M.; Douglas, R.G.

1981-05-08

263

Miocene Paleogeography of Southwestern California and Its Implications Regarding Basin Terminology  

Microsoft Academic Search

A new palinspastic reconstruction for the latest Oligocene of southwestern California is created by: (1) backsliding the eastern part of the western Transverse Ranges west of the curved San Gabriel-Sierra Madre fault in a counterclockwise, rotational, left-slip direction in order to close the gap created by medial Miocene transrotational extension of the easternmost Los Angeles basin; and (2) bending the

A. Eugene Fritsche

1998-01-01

264

Miocene Burrows of Extinct Bear Dogs: Indication of Early Denning Behavior of Large Mammalian Carnivores  

Microsoft Academic Search

Partial skeletons of four species of extinct carnivores have been found in their dens excavated in the floodplain of an early Miocene ephemeral braided stream at Agate Fossil Beds National Monument, Nebraska. Bear dogs (Carnivora: Amphicyonidae) were the principal occupants; their den dimensions and body size are similar to those of living wolves and hyenas. Discovery of this predator community

Robert M. Hunt; Xue Xiang-Xu; Joshua Kaufman

1983-01-01

265

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

266

Oligo-Miocene rift of Sardinia and the early history of the Western Mediterranean Basin  

NASA Astrophysics Data System (ADS)

The geodynamic evolution of the Western Mediterranean Basin, in spite of many studies, is still uncertain. There is some consensus for interpreting this basin as a kind of small oceanic marginal basin. Its opening has generally been related to a subduction process which was active during the Oligocene-Miocene somewhere east of Sardinia-Corsica1-7. As the margins of the basin are deeply buried below Miocene-to-present sediments, direct lithological and stratigraphical data which could explain the events responsible for its formation are rare8-10 or missing altogether. To obtain such data, detailed field studies have been undertaken in Sardinia (Fig. 1), and the first results are presented here. This approach is justified by the fact that in that island, Oligocene and Miocene sediments were deposited in a rift (fossa tettonica sarda of Verdabasso11), which is the easternmost arm of the complex rift system that affected the European plate during Oligocene and Miocene times. One of these arms evolved towards a small oceanic basin-the Western Mediterranean or Algero-Provençal Basin-while others such as the Gulf of Valencia and the Sardinia rift aborted and remained at the rift stage. Its exceptional exposures make it possible to examine the Sardinia rift to clarify the sequence of events which created it, and to establish a sedimentological model which we believe is directly applicable to the Western Mediterranean Basin.

Cherchi, A.

1982-08-01

267

Foraminiferal record of Oligocene-Miocene shales from the Limon Basin, eastern Costa Rica  

SciTech Connect

Foraminiferal analysis of an unusually thick and continuous section of Tertiary shales from the western margin of the Limon Basin, Costa Rica, indicates that rocks from this section are older than similar facies elsewhere in the basin. Approximately 620 meters of silty shales from the Quebrada Terciopelo belong to zones N3 through N9 while the oldest shales from the rest of the basin are in N12 to N13. The lowermost N3 zone is characterized by the presence of the Late Oligocene larger foraminifera Lepidocyclina waylandvaughani and Heterostegina antillea associated with oncolite clasts in a siltstone. Shales above contain typical Early to Middle Miocene planktonic foraminifera, including Catapsydrax stainforthi, Globorotalia kugleri, G. sicanus, and G. peripheroronda. The first two species, used widely as Early Miocene markers and reported to have nonoverlapping stratigraphic ranges, are found together within a short interval in this section. This Quebrada Terciopelo sedimentary section shows the transition from a shallow nearshore environment in the Late Oligocene to an open marine outer shelf or upper slope in the Miocene. The biostratigraphic analysis demonstrates than an approximately 70 meter thick Late Oligocene (N3) to Early Miocene (N5) section is repeated. This is apparently related to normal faulting associated with the uplift of the Talamanca Mountains.

Cassell, D.T.; Sen Gupta, B.K.

1985-01-01

268

An integrated stratigraphy of the Pannonian (Late Miocene) in the Vienna Basin  

Microsoft Academic Search

The Upper Miocene Pannonian stage is represented in the Vienna Basin by an up to 1200 m thick siliciclastic succession comprising lacustrine and terrestrial deposits. The Pannonian is a crucial time in the development of the Vienna Basin as it is characterised by the retreat of Lake Pannon from the Vienna Basin giving place to terrestrial-fluvial settings. Here, for the

Vienna Basin; Mathias HARZHAUSER; Gudrun DAXNER-HÖCK; Werner E. PILLER

269

Petrified wood from the Miocene volcanic sequence of Coromandel Peninsula, northern New Zealand  

Microsoft Academic Search

Petrified (silicified) wood is found throughout the Miocene sub?aerial volcanic sequence of Coromandel Peninsula. The identification of 160 samples, mostly collected from geological formations of known age, shows that over the period from 18–6 Ma the majority of trees within local forests were angiosperms, particularly southern beech (Nothofagus spp.) and casuanna (Casuarinaceae). A species close to modern Weinmanma and Lauretta

P. R. Moore; R. Wallace

2000-01-01

270

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

271

A diverse ichnofauna from Eocene?Miocene rocks of the Makran Range (S.E. Iran)  

Microsoft Academic Search

A diverse assemblage of trace fossils has been collected from Lower Eocene to Upper Miocene strata during regional geological mapping of 75,000 km of the Makran Range of southeastern Iran. Almost all are excellently preserved and this allows detailed descriptions, which in some cases can be used as a basis for taxonomic revisions of much used but inadequately analysed ichnogenera.27

T. P. Crimes; G. J. H. McCall

1995-01-01

272

The development of the Amazonian mega-wetland (Miocene; Brazil, Colombia, Peru, Bolivia)  

Microsoft Academic Search

The scenery of Western Amazonia once consisted of fluvial systems that originated on the Amazonian Craton and were directed towards the sub-Andean zone and the Caribbean. In the course of the Early Miocene these fluvial systems were largely replaced by lakes, swamps, tidal channels and marginal marine embayments, forming a mega-wetland. In this chapter we will review the characteristics of

C. Hoorn; F. P. Wesselingh; J. Hovikoski; J. Guerrero

2010-01-01

273

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

274

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

275

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

Microsoft Academic Search

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

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

2009-01-01

276

Fossil pollen grains of Asteraceae from the Miocene of Patagonia: Nassauviinae affinity  

Microsoft Academic Search

Fossil pollen grains with morphological features unique in the subtribe Nassauviinae (tribe Mutisieae, Asteraceae) occur in Miocene marine deposits of eastern Patagonia, southern South America. A new morphogenus and two morphospecies are proposed to assemble fossil pollen grains characterized by having a complex bilayered exine structure with delicate columellae, separated by an internal tectum. Subprolate specimens with Trixis exine type

Viviana Barreda; Luis Palazzesi; María Cristina Tellería

2008-01-01

277

Foraminiferal biostratigraphy of the post mid-Miocene in two boreholes in the Danish North Sea.  

National Technical Information Service (NTIS)

Cutting samples from two exploration wells, Cleo-1 and Kim-1, in the central Trough area in the northwestern part of the Danish North Sea, have been investigated for foraminiferal content in the section above the prominent mid-Miocene event. Benthonic for...

P. B. Konradi

1995-01-01

278

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

279

A Miocene Halictine Bee from Rubielos de Mora Basin, Spain (Hymenoptera: Halictidae)  

Microsoft Academic Search

A new species of halictine bee (Apoidea: Anthophila: Halictidae) is described and figured from laminated mudstones of Early Miocene age from Rubielos de Mora Basin, Teruel, Spain. Halictus petrefactus, new species, is the first bee from these deposits to be formally described. The geological history of the Halictidae and of the bees as a whole is briefly reviewed.

MICHAEL S. ENGEL; ENRIQUE PEñALVER

2006-01-01

280

Gypsum karstification in the Middle Miocene Fatha Formation, Mosul area, northern Iraq  

Microsoft Academic Search

Karstified Middle Miocene sediments are widely exposed in northern Iraq particularly in the area surrounding the city of Mosul. The unit is dominated by gypsum and exposed in thirteen anticlinal structures within the investigated area of about 1600 square kilometers. Synclines, though containing the same sequence, are not karstified due to a Quaternary cover. Karst features were located from air

Saad Z. Jassim; Antwanet S. Jibril; Nazar M. S. Numan

1997-01-01

281

Detrital chromian spinels from Miocene and Holocene sediments of northern Iraq: provenance implications  

Microsoft Academic Search

* Corresponding author The study integrates mineralogical and chemical characteristics of the chromian spinels from northern Iraq using standard petrographic and scanning microscope techniques as well as electron microprobe analyses in order to better understand their provenance, and the implications thereof. Detrital chromian spinels are found as one of the predominant acces- sory heavy minerals within fluviatile Miocene and Holocene

Ali I. Al-JubOury; Mohsin M. GhAzAl; Tom MccAnn

2009-01-01

282

Paleobiology and paleoecology of an arid–semiarid Miocene South American ichnofauna in anastomosed fluvial deposits  

Microsoft Academic Search

Miocene deposits of the Toro Negro Formation in La Rioja province, Argentina, host a rich vertebrate and invertebrate ichnofauna. Trace fossils are recorded from the lower part of the Lower Member of the Toro Negro Formation at Quebrada de La Troya. This succession consists of sandstone, intraformational breccia, mudstone and few conglomerate deposited in sandy anastomosing fluvial systems developed under

Verónica Krapovickas; Patricia L. Ciccioli; M. Gabriela Mángano; Claudia A. Marsicano; Carlos O. Limarino

2009-01-01

283

A Closer Look at the Late Miocene-Early Pliocene,Biogenic Bloom  

Microsoft Academic Search

A late Miocene-early Pliocene increase in marine biological productivity has been recorded in equatorial upwelling areas of the Indo-Pacific Ocean as well as in the Benguela coastal upwelling area. Before proposing possible causes of the biogenic bloom, we ask two questions: 1) was the biogenic bloom a global event? 2) was the onset of the biogenic bloom simultaneous in different

L. Diester-Haass; K. Billups

2003-01-01

284

A new genus of kentriodontid (Cetacea: Odontoceti) from the Miocene of south Italy  

Microsoft Academic Search

The holotype of Priscodelphinus squalodontoides Capellini, 1878 and a second, more complete skull both derive from Miocene sediments of the Salento Peninsula (southern Italy). They are ascribed to Rudicetus, a new genus within the Kentriodontidae (Odontoceti, Cetacea). Rudicetus is characterized by a nearly symmetrical skull, condylobasal skull length of about 450 mm, rostrum 60 percent of the condylobasal length of

Giovanni Bianucci

2001-01-01

285

Early Miocene Subglacial Basalts, the East Antarctic Ice Sheet, and Uplift of the Transantarctic Mountains  

NASA Astrophysics Data System (ADS)

Subglacially erupted volcanic rocks from Mount Early and Sheridan Bluff, Antarctica, yield whole-rock potassium-argon dates and argon-40/argon-39 release spectra of Early Miocene age. Field associations suggest the existence of the East Antarctic ice sheet and significant uplift of the Transantarctic Mountains by that time.

Stump, Edmund; Sheridan, Michael F.; Borg, Scott G.; Sutter, John F.

1980-02-01

286

Rifting, recurrent landsliding and Miocene structural reorganization on NW-Tenerife (Canary Islands)  

Microsoft Academic Search

We studied mechanisms of structural destabilization of ocean island flanks by considering the linkage between volcano construction and volcano destruction, exemplified by the composite Teno shield volcano on Tenerife (Canary Islands). During growth, Tenerife episodically experienced giant landslides, genetically associated with rifting and preferentially located between two arms of a three-armed rift system. The deeply eroded late Miocene Teno massif

T. Walter; H.-U. Schmincke

2002-01-01

287

Tropical Planktonic Zones and Calcareous Nannoplankton Correlations in Part of the California Miocene  

Microsoft Academic Search

THE material used in this study is from exposures along the east shore of Newport Bay, California (Fig. 1). This section contains good assemblages of benthonic foramini-fera of Kleinpell's upper Luisian and lower Mohnian stages1. The Luisian and Mohnian stages are represented by the upper middle and the lower upper part of the Miocene Monterey Shale. These stages are traditionally

J. A. Wilcoxon

1969-01-01

288

Origin of dolomite in Miocene Monterey Shale and related formations in the Temblor Range, California  

Microsoft Academic Search

Dolomites in thick sections of Miocene Monterey Shale and related formations in the Temblor Range of California acquired their isotopic compositions as they formed at shallow depth in the original sediment rich in organic matter, and retained the composition against the vicissitudes of burial diagenesis. The oxygen isotopes of dolomites of successive beds record changes in temperature of bottom water

Irving Friedman; K. J. Murata

1979-01-01

289

Morphology and propagation styles of Miocene submarine basanite lavas at Stanley, northwestern Tasmania, Australia  

Microsoft Academic Search

Miocene submarine basanite pillows, lava lobes, megapillows and sheet lavas in the Stanley Peninsula, northwestern Tasmania, Australia, are well-preserved in three dimensions. The pillows have ropy wrinkles, transverse wrinkles, symmetrical wrinkles, contraction cracks and three types of spreading cracks on their surfaces, and concentric and radial joints in the interior. The lava lobes have ropy wrinkles and contraction cracks on

Yoshihiko Goto; Jocelyn McPhie

2004-01-01

290

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

291

Enamel hypoplasia in Miocene rhinoceroses (Teleoceras) from Nebraska: evidence of severe physiological stress  

Microsoft Academic Search

Quarry samples of lower cheek teeth of the Miocene rhinoceros Teleoceras are analyzed for the presence of enamel hypoplasia using macroscopic, thin-section, and scanning electron microscopic techniques. The presence of enamel pits, furrows, and grooves is noted predominantly on, but not limited to, the buccal side of dp4s. The enamel defect is not as common on permanent teeth, but does

Alfred J. Mead

1999-01-01

292

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

2008-01-01

293

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

NASA Astrophysics Data System (ADS)

We present simulations with a coupled ocean-atmosphere-biosphere model for the Middle Miocene 15 million years ago. The Middle Miocene topography, which alters both large-scale ocean and atmospheric circulations, causes a global warming of 0.7 K compared to present-day. Higher than present-day CO2 levels of 480 and 720 ppm cause a global warming of 2.8 and 4.9 K, thereby matching proxy-based Middle Miocene global temperature estimates of 3-6 K warming. Higher CO2 levels and the associated water vapour feedback enhance the greenhouse effect and lead to a polar amplification of the warming. Although oceanic and atmospheric poleward heat transport are individually altered by 10-30 % in the mid and high latitudes, changes of the total heat transport account only for 4-8 %, pointing toward a compensation between oceanic and atmospheric heat transport. Our model reproduces a denser vegetation in agreement with fossil records. These results suggest that higher than present-day CO2 levels are essential to drive the warm Middle Miocene climate.

Krapp, M.; Jungclaus, J. H.

2011-06-01

294

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

NASA Astrophysics Data System (ADS)

We present simulations with a coupled atmosphere-ocean-biosphere model for the Middle Miocene 15 million years ago. The model is insofar more consistent than previous models because it captures the essential interactions between ocean and atmosphere and between atmosphere and vegetation. The Middle Miocene topography, which alters both large-scale ocean and atmospheric circulations, causes a global warming of 0.7 K compared to present day. Higher than present-day CO2 levels of 480 and 720 ppm cause a global warming of 2.8 and 4.9 K. The associated water vapour feedback enhances the greenhouse effect which leads to a polar amplification of the warming. These results suggest that higher than present-day CO2 levels are necessary to drive the warm Middle Miocene climate, also because the dynamic vegetation model simulates a denser vegetation which is in line with fossil records. However, we do not find a flatter than present-day equator-to-pole temperature gradient as has been suggested by marine and terrestrial proxies. Instead, a compensation between atmospheric and ocean heat transport counteracts the flattening of the temperature gradient. The acclaimed role of the large-scale ocean circulation in redistributing heat cannot be supported by our results. Including full ocean dynamics, therefore, does not solve the problem of the flat temperature gradient during the Middle Miocene.

Krapp, M.; Jungclaus, J. H.

2011-11-01

295

New hominid skull material from the late Miocene of Macedonia in Northern Greece  

Microsoft Academic Search

MIOCENE hominoid material is very scarce1-7 and has previously only been reported as cranial fragments in the Old World. Here we describe a new specimen of Ouranopithecus macedoniensis, which consists of the right part of the face of an adult male with a portion of the frontal bone, a portion of the left part of the face and the maxilla

L. de Bonis; G. Bouvrain; D. Geraads; G. Koufost

1990-01-01

296

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

297

Preliminary report on the geology and vertebrate fauna of the Miocene Manchar Formation, Sind, Pakistan  

Microsoft Academic Search

The Manchar Formation, a middle and upper Miocene fluvial sequence of sandstones, silts, and conglomerates, is exposed in a narrow north–south belt in the Lower Indus Basin of Sind Province, Pakistan. The formation, as measured in geological sections near Lake Manchar, can be divided into three parts differing in the proportions of the sandstones and silts. The contact with the

S. Mahmood Raza; John C. Barry; Grant E. Meyer; Lawrence Martin

1984-01-01

298

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

299

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

300

Confined deep water system development on the accretionary wedge (Miocene, Kahramanmara? Foreland Basin, S turkey)  

NASA Astrophysics Data System (ADS)

According to theoretical studies, the foreland basin consists of: accretionary wedge (including wedge top or piggyback basin), foredeep, forebulge and backbulge depozones. All of them are parallel to the orogenic belts of the overlying and underlying plates. The closure of the southern branch of the Neotethys during the Late Cretaceous led to an oblique collision of the Arabian Plate and the Anatolide-Taurides Platform, leading to the development of the Miocene Kahramanmara? Foreland Basin (KFB). Thus, the promontory shape of the Arabian Plate prevented the development of an accretionary wedge parallel to the orogenic belt. The accretionary wedge of the KFB includes blocks of various sizes and age (mainly Mesozoic limestone) scattered within an Early Tertiary matrix (mass wasting deposits and shallow to deep marine sediments). At the beginning of the Miocene, transtensional tectonism led to the development of half-graben basins on top of the accretionary wedge. These basins (namely; the Tekir and Çukurhisar) also cut the foredeep of the KFB obliquely (in contrast with the theoretical study). This paper focuses on the evolution and fillings of those basins. Initially, claystone and basin margin reef deposits filled the half-graben basins as a consequence of the Lower Miocene sea invasion. Then, long and narrow conglomeratic channels starting from the northern edge of the basins (fan-delta) progressed southwards, passing into sandy lobes, then into claystones. An activation of the boundary faults of the wedge top basin stopped the progression of the Lower-Middle Miocene sediments and led to their deformation. Then, the sedimentation of the KFB shifted towards the basin centre during the Middle Miocene.

Gül, Murat; Cronin, Bryan T.; Gürbüz, Kemal

2012-09-01

301

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

NASA Astrophysics Data System (ADS)

Modern aragonite needles are present all along the modern leeward margin of Great Bahama Bank (ODP Leg 166), while Middle Miocene sediments contain needles only in more distal areas (Sites 1006 and 1007). In contrast to the rimmed, flat-topped platform topography during the Plio-Pleistocene, the Miocene Great Bahama Bank morphology is a carbonate ramp profile. This might imply a different location and precipitation type for Miocene aragonite needles. In this study, aragonite needles in Miocene sediments were isolated using a granulometric separation method. Furthermore, the isolation of the various carbonate components enables the identification of primary versus diagenetic components. The Miocene aragonite needles are concentrated in the finest granulometric sediment fractions (<12 ?m). The fraction-specific geochemical analyses (?13C, ?18O and Sr elemental abundance) represent useful tools to assess the possible sources of the aragonite mud. The geochemical variation of the fractions, rich in pristine aragonite needles, and the characteristics of the needle morphology point to whiting phenomena as the main sediment source and algal fragmentation as a minor component. Both components indicate shallow-water environments as the main sediment source area. Ramp-top-related fine-grained particles now present at distal sites were likely exported as suspended material similar to present-day transport mechanisms. The scarcity of needles at proximal sites is probably linked to hydrodynamic processes but dissolution and recrystallization processes cannot be excluded. The granulometric separation approach applied here enables a better characterization of the finest carbonate particles representing an important step towards the discrimination between primary and diagenetic fine-grained components.

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

2011-11-01

302

Paleogeographic and structural setting of Miocene strata in central western Nevada  

SciTech Connect

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

Stewart, J.H. (Geological Survey, Menlo Park, CA (United States))

1993-04-01

303

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

304

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

305

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, M. R.; John, D. A.; Conrad, J. E.; McKee, E. H.

2000-01-01

306

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

307

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

308

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

NASA Astrophysics Data System (ADS)

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

Rojay, B.; Özsay?n, E.; Çiner, A.

2012-04-01

309

Paleodietary reconstruction of Miocene faunas from Pa?alar, Turkey using stable carbon and oxygen isotopes of fossil tooth enamel  

Microsoft Academic Search

Miocene-age (? 15 Ma) deposits at Pa?alar in northwest Turkey contain abundant and well-preserved dental remains from a variety of herbivores. We used the carbon and oxygen isotopic compositions of inorganic carbonate in enamel from these teeth to reconstruct the paleodiet and sources of body water, respectively, of Miocene mammals. The ?13C (PDB) values of carbonate in the enamel fall

Jay Quade; Thure E. Cerling; Peter Andrews; Berna Alpagut

1995-01-01

310

Detrital zircon U-Pb isotopic constraints on the source provenance of the Eocene-Miocene sedimentary rocks, northern Taiwan  

NASA Astrophysics Data System (ADS)

U-Pb ages of detrital zircons from Eocene-Miocene sedimentary rocks in the northern Taiwan were determined in order to picture their provenance in Southeastern China. The studied formations have been well reported as the Eocene formations in the Northern Cross-Island Highway (the Hsitsun and Szuleng formations) and the Oligocene-Miocene formations in the northeastern coast area (the Wuchihshan, Mushan, Taliao, Shihti, Nankang, Nanchuang, Tapu, and the Erhchiu formations). LA-ICPMS U-Pb results of zircon indicate that the Eocene sandstones from the Hsitsun and Szuleng formations display age patterns with main peaks at ca. 200-100 Ma and 540-250 Ma. Meanwhile, the Oligocene (Wuchihshan Fm.)-Late Miocene sandstones (Tapu Fm.) show main peaks at ca. 2.0-1.8 Ga and 2.6-2.4 Ga (account for 30-50%). The Late Miocene sandstone (Erhchiu Fm.), however, shows main peak at ca. 200-100 Ma. In general, the Eocene-Miocene strata in the northern Taiwan have recorded two changing episodes of their source provenance: 1) sometime between Eocene and Oligocene; 2) the Late Miocene. Zircon ages from the Eocene formations indicate that the sources are dominantly derived from Yanshanian (200-65 Ma) and Paleozoic (540-250 Ma) granitic plutons in SE China, and with minor Paleoproterozoic components. On the contrary, zircon ages from the Oligocene to the Late Miocene formations indicate that the sources are dominantly Paleoproterozoic in age, hence we speculate that the sediments are very likely derived from Cathaysia basement exposed in the northwest Fujian and Zhejiang province, or alternatively the Precambrian metasedimentary rocks exposed in the SE China. Nevertheless, in the Late Miocene (Erhchiu Fm.), the resulted age spectra are similar to those from the Eocene formation, the similar patterns suggest that the sources have shifted back to Yanshanian plutons again.

Shao, W.; Chen, W.; Chung, S.

2009-12-01

311

High-frequency Miocene sequence stratigraphy, offshore Louisiana: Cycle framework and influence on production distribution in a mature shelf province  

Microsoft Academic Search

The regressive Miocene succession of offshore Louisiana comprises 10 third-order sequences and no fewer than 58 fourth-order se- quences, which average approximately 1.1 and 0.19 m.y. in dura- tion, respectively, comparable to durations measured in the Gulf Coast Basin and basins worldwide. Upper lower to middle Miocene distal third-order sequences comprise mostly lowstand prograding- wedge, slope-fan, and basin-floor-fan deposits. In

Tucker F. Hentz; Hongliu Zeng

2003-01-01

312

Fohn lamproite and a possible Late Eocene — pre?Miocene diatreme field, Northern Bonaparte Basin, Timor Sea  

Microsoft Academic Search

Seismic profiles in the Northern Bonaparte Basin, Timor Sea, northern Australia, disclose an east?northeast?trending 120 × 25 km swathe of over 40 circular to subcircular features excavated in the pre?Miocene erosional surface and buried by Lower Miocene sediments. The larger structures, typified by the Fohn Structure, include central structural highs overlying narrow vertical corridors of upward?bulging seismic horizons (bulge?forms). Associated

J. D. Gorter; A. Y. Glikson

2002-01-01

313

High Frequency/High Magnitude Middle Miocene Sea Level Cycles Recorded in Carbonate Bank Margins in the Maldives  

NASA Astrophysics Data System (ADS)

The beginning of the middle Miocene marks an abrupt change from aggradation to intense progradation of the Maldives carbonate platform. 2D seismic data from the Maldives, equatorial Indian Ocean, shows that isolated carbonate bank margins of middle Miocene age are composed of five prograding sequences. Based on the interpretation of stratal patterns along separate transects, a qualitative relative sea level curve for the middle Miocene was constructed. Each sequence is interpreted to represent a complete sea level cycle. Each cycle begins with a relative sea level fall recorded in downstepping geometries, followed by flooding and a subsequent highstand. The duration of each cycle are estimated to be about 1 Ma or less, and the amplitude of the falls as high as 100 m. The subsequent sea level rises appear to be of high magnitude also, almost always restoring to the previous position. The terminal middle Miocene sequence in the Maldives contains massive gravity-flow deposits at the toe of slope interpreted as a result of a significant sea level drop. Located in the tectonically stable setting and removed from pulses of siliciclastic sediments, the Maldives middle Miocene relative sea level record must contain a strong eustatic component. Oxygen isotope record in the middle Miocene shows a stepwise increase in heavy isotopes implying growth of continental ice. Growth of the East Antarctica Ice Sheet and probably initiation of the West Antarctica Ice Sheet occurred in the middle Miocene. These records point to a eustatic sea level fall in the middle Miocene but do not show high frequency/high magnitude cycles as recorded in the Maldives margins. The Maldives record demonstrates a transition from a dominantly greenhouse world with small frequency and magnitudes cycles to the ice-house world with high frequency/high magnitude cycles.

Belopolsky, A. V.; Belopolsky, A. V.; Droxler, A. W.

2001-05-01

314

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

NASA Astrophysics Data System (ADS)

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 biostratigraphic 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 occurred 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 occurred rapidly throughout North America between about 15 and 16 Ma.

MacFadden, Bruce J.; Bryant, J. Daniel; Mueller, Paul A.

1991-03-01

315

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

316

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

317

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

318

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

319

Variation in silicate weathering across the Oligocene-Miocene boundary: evidence from lithium and neodymium isotopes  

NASA Astrophysics Data System (ADS)

Changes in global silicate weathering have a profound effect on the global carbon cycle and Earth's climate on multi-million year timescales. They may also be associated with short-term (<105 yrs) climatic aberrations: for example, temperature anomalies observed across the Oligocene-Miocene (O/M) boundary (~23 Ma) have been linked to changes in silicate rock exposure on Antarctica. To explore this idea further, we present trace element data along with lithium and neodymium isotope data measured in the carbonate tests of O/M-aged planktic foraminifera. These temporal records of the Li and Nd isotopic composition (?7Li and ?Nd) of seawater generated from deep-sea sediment core material (ODP Site 926, Ceara Rise) require large samples of mono-specific foraminifera (~20 mg). Therefore we first assess the geochemical utility of the large, abundant taxa, Dentoglobigerina venezuelana, for the purposes of ?7Li and ?Nd analysis. Three morphotypes of D. venezuelana are defined based on the morphology of the final chamber and aperture architecture. We find that the palaeoecology of these morphotypes based on their Mg/Ca, ?18O, and ?13C compositions is suitably similar to allow them to be grouped for the purpose of generating "sample-hungry" continental weathering records. Because the ?7Li and ?Nd of seawater are influenced by changes in continent-derived fluvial input to the oceans, records of seawater ?7Li and ?Nd have the potential to help constrain past changes in continental weathering. Li isotopes fractionate strongly during weathering processes, with ?7Li values becoming lower as weathering reactions tend towards completion. Nd sourced from ancient continental material typically possesses distinctively unradiogenic compositions (low ?Nd) relative to younger, mantle-derived sources. Finally, local vs. global signals of weathering input can be evaluated through utilisation of the differing oceanic residence times of Li (~1 Myrs) and Nd (~1 kyrs). To this end, we present a 4 Myr isotopic and trace element record for the O/M boundary, and we use these new data to better constrain the links between weathering and climate during this interval of significant climate change.

Stewart, J.; James, R. H.; Wilson, P. A.; Anand, P.; Edgar, K. M.

2011-12-01

320

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

321

Middle Miocene to Pleistocene sedimentary record of rift evolution in the southern Albert Rift (Uganda)  

Microsoft Academic Search

This study presents an almost complete Middle Miocene to Pleistocene sequence of synrift sediments in the western branch of\\u000a the East African Rift. The studied succession is exposed in several patches on an eastward tilted block between the northern\\u000a tip of the Rwenzori Block and the eastern shoulder of the Albert Rift. In this position, it reaches a maximum thickness

S. Roller; J. Hornung; M. Hinderer; I. Ssemmanda

2010-01-01

322

Post-Miocene Faulting and Folding in the Southwestern Transverse Ranges, Santa Monica Bay, California  

Microsoft Academic Search

We investigate patterns and timing of post-Miocene deformation, including folding and uplift of the Santa Monica Mountains, by mapping high-and low-angle faults and submerged geomorphic features in northeast Santa Monica Bay, California. Our multidisciplinary approach utilizes deep industry seismic reflection data, shallow high-resolution data, and USGS multibeam and NOAA point bathymetric data. We mapped a blind, north-dipping low-angle fault that

K. G. Broderick; C. C. Sorlien; M. J. Kamerling; L. Seeber; B. P. Luyendyk

2002-01-01

323

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

324

Late Miocene biomarker and pollen records in Southeast Atlantic Ocean sediments indicate environmental changes  

Microsoft Academic Search

The Late Miocene epoch is characterized by fundamental changes in Earth`s climate system: sea-level variability, changes in surface- and deep-water circulation, increase in upwelling intensity along the coasts and turnover in marine and terrestrial biota [1,2]. It is thought that plants using the CO2 concentrating C4 mechanism for photosynthesis potentially evolved during times of a global drop in atmospheric CO2

Florian Rommerskirchen; Lydie Dupont; Tegan Condon; Gesine Mollenhauer; Enno Schefuß

2010-01-01

325

Environmental changes in Southwest Africa during the Miocene C4 plant expansion  

Microsoft Academic Search

The Late Miocene epoch is characterized by fundamental changes in Earth's climate system: sea-level variability, changes in surface- and deep-water circulation, increase in upwelling intensity along the coasts and turnover in marine and terrestrial biota [1,2]. It is thought that plants using the CO2 concentrating C4 mechanism for photosynthesis potentially evolved during times of a global drop in atmospheric CO2

L. M. Dupont; F. Rommerskirchen; T. Condon; G. Mollenhauer; E. Schefuss

2009-01-01

326

Miocene seawater 187Os\\/ 188Os ratios inferred from metalliferous carbonates  

Microsoft Academic Search

Seawater 187Os\\/188Os ratios for the Middle Miocene were reconstructed by measuring the 187Os\\/188Os ratios of metalliferous carbonates from the Pacific (DSDP 598) and Atlantic (DSDP 521) oceans. Atlantic and Pacific 187Os\\/188Os measurements are nearly indistinguishable and are consistent with previously published Os isotope records from Pacific cores. The Atlantic data reported here provide the first direct evidence that the long-term

Douglas N Reusch; Greg Ravizza; Kirk A Maasch; James D Wright

1998-01-01

327

Paleomagnetic evidence for Late Miocene counterclockwise rotation of north coast carbonate sequence, Puerto Rico  

SciTech Connect

A paleomagnetic study of the essentially undeformed middle Tertiary carbonate sequence along the north coast of Puerto Rico reveals statistically significant pre-Pliocene discordance of characteristic component directions against those expected from cratonic North America for much of the section. Despite generally weak to moderately weak magnetic intensities, confirmation of the magnetization as primary in origin comes from the presence of two distinct components of magnetization, intrasite bipolarity, and/or the reproducibility of measurements. The mean geographic direction for the upper Oligocene to middle Miocene strata is 335.2{degree}/32.9{degree} and the corrected mean paleomagnetic pole is 207.6{degree}/66.5{degree}, (N = 3, {alpha}95 = 4.3{degree}). This suggests a counter-clockwise (CCW) block rotation of Puerto Rico and its microplate of 24.5{degrees} ({plus minus} 5.8{degrees}) during the late Miocene. Using a width of 250 km for the Northern Caribbean Plate Boundary Zone (NCPBZ) between the North American Plate and Caribbean Plate, the mean left lateral displacement implied is 1.8 to 2.4 cm/yr, which agrees fairly well with published relative motion rates for the two plates. Average rotation rate for 50 Ma to 20 Ma was 0.7{degree}/my but perhaps as great as 4{degree}/my in the Miocene. Resolution of mean paleolatitude indicates northward motion of a degree or less during the period of rotation. Causes of this short-lived rotation may include (1) tectonic escape from the inhibiting presence of the Bahama Banks and Beata Ridge during eastward motion of Puerto Rico along the sinistral transpressive Puerto Rico Trench and Muertos Trough fault systems or (2) changes in relative plate motions of the Caribbean and North American Plate during the late Miocene.

Reid, J.A.; Plumley, P.W. (Syracuse Univ., NY (United States)); Schellekens, J.H. (Univ. of Puerto Rico, Mayaguez (Puerto Rico))

1991-03-01

328

Preliminary study on enamel microstructure of Yuanmou Miocene hominoids of China  

Microsoft Academic Search

Preliminary study on enamel microstructure of 5 lower permanent incisors of Late Miocene Yuanmou hominoids was conducted using\\u000a a scanning electron microscope (SEM). The enamel incremental markings, as well as perikymata spacing and its periodicity were\\u000a observed and counted. Using the perikymata number and periodicity, the crown formation times of the incisors are estimated.\\u000a The transverse and longitudinal microstructures of

Lingxia Zhao; Liang Zheng; Feng Gao; Chu Jiang

2003-01-01

329

Marine biological productivity, carbon cycling, and climate cooling during the Oligocene to Miocene transition  

NASA Astrophysics Data System (ADS)

The Oligocene to Miocene boundary (the so-called Mi1 event) marks one of the major Cenozoic cooling steps. A corresponding but slightly out of phase ?13C maximum has been attributed to increased organic matter burial associated with global climate cooling (e.g., Zachos et al., 2001). To test this idea we have constructed records of marine biological productivity (based on benthic foraminiferal accumulation rates, BFAR) to parallel the stable isotope records from 20-25 Ma at three sites from the Atlantic Ocean sampling different hydrographic regimes. Our data show that the ?18O and ?13C maximum that characterize the Oligocene/Miocene boundary is accompanied by a pronounced maximum in BFAR derived paleoproductivity at all sites. In the subtropical Atlantic (Site 1265) and the Southern Ocean (Site 1090), productivity increases about 500 kyr prior to Mi1 in tune with the beginning of enhanced amplitude variations in the benthic foraminiferal ?13C record. In the tropical Atlantic (Site 926), where we have appropriate sampling resolution (~10 kyr), eccentricity-scale variations in paleoproductivity are coherent with the stable isotope records and in-phase with the ?18O values. Paleoproductivity leads ?13C at the 400 kyr period in agreement with the lead of ?18O values with respect to ?13C values. These results illustrate that the link between Oligocene to Miocene climate transition and the carbon cycle is one of marine primary productivity both during the glacial event of Mi1 as well as on eccentricity time scales. The late Oligocene (24 Ma) increase of productivity suggests that a reduction of atmospheric CO2 levels mediated by increased biological productivity may have lead to climate cooling at the Oligocene to Miocene boundary.

Diester-Haass, Liselotte; Billups, Katharina; Emeis, Kay-Christian

2010-05-01

330

Late Miocene lacustrine sedimentation in the Mytilinii Basin, Samos Island, Greece  

Microsoft Academic Search

The Mytilinii Basin, eastern Samos Island, Greece, is one of many basins that developed in southeastern Europe during the\\u000a Upper Neogene. The oldest lacustrine portion is of Late Miocene age, and besides tuffs, includes bituminous limestones, marlstones,\\u000a dolostones and porcelanites of the Pythagorion Formation, and the limestones and diatomites of the overlying Hora Beds. Younger\\u000a sedimentary rocks of Turolian through

R. Bernhart Owen; Robin W. Renaut; Michael G. Stamatakis

2011-01-01

331

A Miocene termite nest from southern Argentina and its paleoclimatological implications  

USGS Publications Warehouse

A Miocene termitarium attributable to the extant termite Syntermes (Isoptera: Termitidae, Nasutitermitinae) is the first fossil termite nest reported from South America and possibly the oldest record of the Isoptera from that continent. A new ichnogenus and ichnospecies, Syntermesichnus fontanae, is proposed for this distinctive trace fossil. It differs from nests constructed by other members of the Nasutitermitinae in its architectural organization and its large size. -from Authors

Bown, T. M.; Laza, J. H.

1990-01-01

332

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

333

Geology and geochronology of type Chasicoan (late Miocene) mammal-bearing deposits of Buenos Aires (Argentina)  

Microsoft Academic Search

The late Miocene Chasicoan mammal-bearing deposits exposed along the lower reach of Arroyo Chasicó are composed of cross-bedded, very fine sandstones interpreted as a channel-bar deposit (lithofacies association 1) grading upward into sandy siltstones (lithofacies association 2), probably accumulated through relatively high-density flows in a marginal channel and\\/or floodplain environment. The uppermost levels are dominantly composed of mudstones and sandy

Marcelo A. Zárate; Peter H. Schultz; Adriana Blasi; Clifford Heil; John King; Willis Hames

2007-01-01

334

Depositional facies of the Miocene-Pliocene Ogallala Formation, northwestern Texas and eastern New Mexico  

Microsoft Academic Search

Deposition of the basal fluvial sediments of the Miocene-Pliocene Ogallala Formation in western Texas and eastern New Mexico was controlled by topography on the underlying erosional surface. Paleovalley-fill facies consist of gravelly and sandy braided-stream deposits interbedded with and overlain by eolian sediments deposited as sand sheets and loess. Uplands on the pre-Ogallala erosional surface are overlain primarily by similar

Thomas C. Gustavson; Dale A. Winkler

1988-01-01

335

Climate and vegetation during the Miocene - evidence from Danish palynological assemblages  

Microsoft Academic Search

Abstract Several Danish exposures and one drill core spanning the upper Oligocene-upper Miocene interval of the Cenozoic (i.e., 24–5 Myr ago) were palynologically investigated. The sedi- ments were deposited in alternating deltaic, marginal marine and fully marine settings, and reveal a rich and diverse miospore flora, associated with abundant dinoflagellate cysts. The results consistently demonstrate that coastal areas in what

Linda Larsson-Lindgren

336

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

337

Oligo-Miocene rift of Sardinia and the early history of the Western Mediterranean Basin  

Microsoft Academic Search

The geodynamic evolution of the Western Mediterranean Basin, in spite of many studies, is still uncertain. There is some consensus for interpreting this basin as a kind of small oceanic marginal basin. Its opening has generally been related to a subduction process which was active during the Oligocene-Miocene somewhere east of Sardinia-Corsica1-7. As the margins of the basin are deeply

A. Cherchi; L. Montadert

1982-01-01

338

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

339

Chronology and integrated stratigraphy of the Miocene Sinj Basin (Dinaride Lake System, Croatia)  

Microsoft Academic Search

In the Miocene, the intra-montane basins of the Dinaric Mountain Chain harbored a series of long-lived lakes constituting the so-called Dinaride Lake System. The thick lacustrine sedimentary records of these lakes provide an excellent opportunity to study evolution and radiation of mollusks in an isolated environment. The 500m thick infill that accumulated in the Sinj Basin is one of the

A. de Leeuw; O. Mandic; A. Vranjkovi?; D. Paveli?; M. Harzhauser; W. Krijgsman; K. F. Kuiper

2010-01-01

340

A Microbial Mat of a Large Sulfur Bacterium Preserved in a Miocene Methane-Seep Limestone  

Microsoft Academic Search

A Miocene methane-seep limestone from the Romagna Apennine (Pietralunga, Italy) was found to contain an extraordinarily well-preserved microbial mat consisting of filamentous fossils. Individual filaments of the lithified Pietralunga mat are 50 to 80 ? m in diameter and resemble the sulfide-oxidizing bacterium Beggiatoa. Mats of sulfur bacteria are common around modern methane-seeps, but have not yet been reported from

Jörn Peckmann; Volker Thiel; Joachim Reitner; Marco Taviani; Paul Aharon; Walter Michaelis

2004-01-01

341

Equatorial Pacific deep-sea benthic foraminifera: Faunal changes before the middle Miocene polar cooling  

Microsoft Academic Search

Data on the composition of benthic foraminiferal faunas at Deep Sea Drilling Project Site 575 in the eastern equatorial Pacific Ocean were combined with benthic and planktonic carbon- and oxygen-isotope records and CaCO3 data. Changes in the composition of the benthic foraminiferal faunas at Site 575 predated the middle Miocene period of growth of the Antarctic ice cap and cooling

E. Thomas; E. Vincent

1987-01-01

342

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

343

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.

344

Geology and palaeontology of the Late Miocene Middle Awash valley, Afar rift, Ethiopia  

Microsoft Academic Search

The Middle Awash study area of Ethiopia's Afar rift has yielded abundant vertebrate fossils (~10,000), including several hominid taxa. The study area contains a long sedimentary record spanning Late Miocene (5.3-11.2Myr ago) to Holocene times. Exposed in a unique tectonic and volcanic transition zone between the main Ethiopian rift (MER) and the Afar rift, sediments along the western Afar rift

Giday WoldeGabriel; Yohannes Haile-Selassie; Paul R. Renne; William K. Hart; Stanley H. Ambrose; Berhane Asfaw; Grant Heiken; Tim White

2001-01-01

345

Carbon13Rich Diagenetic Carbonates in Miocene Formations of California and Oregon  

Microsoft Academic Search

Carbon unusually rich in C13 (delta C13 = +5.4 to +19.0 per mil relative to the Peedee belemnite carbonate standard of the University of Chicago) is characteristic of certain diagenetic limestones and dolomites in the Miocene Monterey Shale of California and the Nye Mudstone of Oregon. This heavy carbon may have originated through low-temperature equilibration between CO3{}- and CO2 in

K. J. Murata; I. I. Friedman; B. M. Madsen

1967-01-01

346

Filling the gap: a fossil frogfish, genus Antennarius (Teleostei, Lophiiformes, Antennariidae), from the Miocene of Algeria  

Microsoft Academic Search

A new species of frogfish, Antennarius monodi sp. nov., is described from the Upper Miocene (Messinian) of Raz-el-Ain, near Oran, north-east Algeria. The type and only specimen of this taxon is the first articulated skeleton belonging to the family Antennariidae ever recorded as a fossil. The morphological and meristic characters observed support the inclusion of this species in the Antennarius

G. Carnevale; T. W. Pietsch

2006-01-01

347

The first female maxilla of the hominoid Ouranopithecus macedoniensis from the late Miocene of Macedonia, Greece  

Microsoft Academic Search

A maxilla with both toothrows C-M3 of a late Miocene hominoid is described. It was found at the locality Nikiti 1 (NKT) of Chalkidiki (Macedonia, Greece). The locality has been dated to late Vallesian-earliest Turolian. The morphological characters and the comparison of the new maxilla suggest that it is a female individual of Ouranopithecus macedoniensis. It is the first known

George D. Koufos

1995-01-01

348

Miocene stratigraphy and mammal fauna from the Sulaiman Range, Southwestern Himalayas, Pakistan  

Microsoft Academic Search

The thick (>4000 m) coarsening-upward terrestrial Neogene sequence of the Sulaiman Range (Middle Indus Basin, central Pakistan) is the western extension of the Siwalik outcrop belt of the Sub-Himalayas. The near-shore to terrestrial sedimentation in the Sulaiman Range, represented by the Chitarwata Formation, began by the late Oligocene to basal Miocene when the main Himalayan foreland was primarily a non-depositional

S. Mahmood Raza; Iqbal U Cheema; William R Downs; A. Rahim Rajpar; Steven C Ward

2002-01-01

349

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

350

Late Eocene-Middle Miocene paleoclimates of the south-west Pacific: oxygen isotopic evidence  

SciTech Connect

High resolution oxygen isotopic stratigraphy is presented for Late Eocene-Middle Miocene sequences in a traverse of 6 DSDP sites from the southwest Pacific at water depths ranging from 1300 to 2000 m and from the warm subtropics to the cool temperature water masses. The data record the progressive increase of latitudinal temperature gradients from the late Eocene. A pattern of increasing isotopic offset between the latitudinally distributed sites is linked to the establishment and strengthening of the circum-Antarctic Current. The intensification of this current system progressively decoupled the warm subtropical gyres from cool polar circulation, in turn leading to Antarctic glaciation. Enriched oxygen isotopic values clustering in the middle Oligocene, are interpreted to represent accumulations of Antarctic ice, although this must have been temporary and of relatively low volume. This Antarctic ice must have disappeared by the Early Miocene when delta/sup 18/O values were relatively depleted, reaching minimum values during the late Early Miocene (19.5 to 16.5), the climax of Neogene warmth. This climatic optimum was immediately followed by a major enrichment in benthic delta/sup 18/O values between approx. 16.5 and 13.5 Ma, which is interpreted to represent major, permanent accumulation of the East Antarctic ice sheet and cooling of bottom waters.

Kennett, J.P.; Murphy, M.G.

1985-01-01

351

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

352

Marine biological productivity and carbon cycling during the Oligocene to Miocene climate transition  

NASA Astrophysics Data System (ADS)

The Oligocene to Miocene boundary marks one of the major Cenozoic cooling steps. A corresponding but slightly out of phase ?13C maximum has been attributed to increased organic matter burial associated with global climate cooling (e.g., Zachos et al., 2001). To test this idea we have constructed records of marine biological productivity (based on benthic foraminiferal accumulation rates, BFAR) and sequestration of total organic carbon (TOC) in pelagic sediments to parallel the stable isotope records from 20-25 Ma. Here we present first results from Ceara Rise Site 926 located in the tropical northwestern Atlantic. Our data show that the ?18O/?13C maximum that characterized the Oligocene/Miocene boundary is accompanied by a pronounced maximum in BFAR derived paleoproductivity. In addition, there are longer term variations in paleoproductivity that follow the well established eccentricity-scale variations in the ?18O and ?13C record. Cross-spectral analysis focusing on the Oligocene/Miocene boundary interval (22-24 Ma), for which we have an average sampling resolution of about 10 kyr, verifies that paleoproductivity is coherent with the stable isotope records above the 80% level. These results support the hypothesis that there is a relationship between global climate cooling and the carbon cycle via marine primary productivity.

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

2009-12-01

353

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

354

Late Miocene remagnetization within the internal sector of the Northern Apennines, Italy  

USGS Publications Warehouse

Paleomagnetic and geologic evidence indicates that Upper Jurassic radiolarian cherts of both the Tuscan Cherts Formation (continental margin, Tuscan Units) and the Monte Alpe Cherts Formation (oceanic crust, Ligurian Units) were remagnetized during Miocene orogenesis of the Northern Apennines of Italy. Characteristic overprint magnetizations with reversed polarities have been found over a large area within the internal sector of the Northern Apennines, including eastern Liguria, Elba Island and the Thyrrenian margin, and west of the Middle Tuscan Ridge. The reversed-polarity overprint (average direction: D=177??, I=-52??, ??95=15??) was most likely acquired during Late Miocene uplift and denudation of the orogenic chain, and thermochemical remagnetization was a probable consequence of increased circulation of orogenic fluids. Similarly, mostly reversed-polarity directions of magnetization have been found by other workers in overlying post-orogenic Messinian sediments (D=177??, I=-57??, ??95=3??), which show little counterclockwise (CCW) vertical-axis rotation with respect to stable Europe (-8??5??). The Monte Alpe Cherts sampled at sites in the external sector of the Northern Apennines, close to major tectonic features, have normal- polarity overprint directions with in situ W-SW declinations. Since the overlying post-orogenic Messinian sediments have not been substantially rotated about vertical axes, the evidence points to an earlier,pre-Late Miocene remagnetization in the external parts of the orogenic chain. ?? 2004 Elsevier B.V. All rights reserved.

Aiello, I. W.; Hagstrum, J. T.; Principi, G.

2004-01-01

355

Seastacks buried beneath newly reported Lower Miocene sandstone, northern Santa Barbara County, California  

SciTech Connect

Three large, isolated exposures of a light-gray, coarse-grained, thick-bedded sandstone unit occur in the northern San Rafael Mountains of Santa Barbara County, California. These rocks are moderately fossiliferous and contain Vertipecten bowersi, Amussiopecten vanvlecki, Aequipecten andersoni, Otrea howelli, shark teeth, whale bones, and regular echinoid spines. The fossils indicate that the sandstone unit, although previously reported as upper(.) Miocene, correlates best with the lower Miocene Vaqueros Formation. This unit was deposited in angular unconformity on a Cretaceous, greenish-gray turbidite sequence of interbedded sandstone and shale, and onlaps the unconformity erosion surface from west to east, the unit being thicker in the west and older at its base. The underlying Cretaceous sandstone beds are well indurated, and during the eastward transgression of the early Miocene sea, they resisted wave erosion and stood as seastacks offshore of the advancing coastline, thus creating a very irregular topographic surface upon which the Vaqueros Formation was deposited. Some seastacks were as much as 4 m tall, as indicated by inliers of Cretaceous rock surrounded by 4-m thick sections of the Vaqueros Formation.

Fritsche, A.E.; Hanna, F.M.

1985-04-01

356

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

357

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

PubMed

The Miocene Randeck Maar (southwestern Germany) is one of the only sites with abundant material of fossil honey bees. The fauna has been the focus of much scrutiny by early authors who recognized multiple species or subspecies within the fauna. The history of work on the Randeck Maar is briefly reviewed and these fossils placed into context with other Tertiary and living species of the genus Apis Linnaeus (Apinae: Apini). Previously unrecorded specimens from Randeck Maar were compared with earlier series in an attempt to evaluate the observed variation. A morphometric analysis of forewing venation angles across representative Recent and Tertiary species of Apis as well as various non-Apini controls was undertaken to evaluate the distribution of variation in fossil honey bees. The resulting dendrogram shows considerable variation concerning the wing venation of Miocene Apini, but intergradation of other morphological characters reveals no clear pattern of separate species. This suggests that a single, highly variable species was present in Europe during the Miocene. The pattern also supports the notion that the multiple species and subspecies proposed by earlier authors for the Randeck Maar honey bee fauna are not valid, and all are accordingly recognized as Apis armbrusteri Zeuner. PMID:21594072

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

2011-05-10

358

Juvenile hominoid cranium from the late Miocene of southern China and hominoid diversity in Asia  

PubMed Central

The fossil ape Lufengpithecus is known from a number of late Miocene sites in Yunnan Province in southern China. Along with other fossil apes from South and Southeast Asia, it is widely considered to be a relative of the extant orangutan, Pongo pygmaeus. It is best represented at the type site of Shihuiba (Lufeng) by several partial to nearly complete but badly crushed adult crania. There is, however, an additional, minimally distorted cranium of a young juvenile from a nearly contemporaneous site in the Yuanmou Basin, which affords the opportunity to better assess the relationships between Lufengpithecus and Pongo. Comparison with similarly aged juvenile skulls of extant great apes reveals no features suggesting clear affinities to orangutans, and instead reveals a morphological pattern largely consistent with a stem member of the hominid (great ape and human) clade. The existence at this time of other hominids in South Asia (Sivapithecus) and Southeast Asia (Khoratpithecus) with clear craniofacial affinities to Pongo suggests both more diversity among Asian Late Miocene apes and more complex patterns of dispersal than previously supposed. Major differences in the associated mammal faunas from the southern China sites and those from South and Southeast Asia are consistent with these findings and suggest more than one dispersal route of apes into East Asia earlier in the Miocene.

Kelley, Jay; Gao, Feng

2012-01-01

359

Genesis of siderite in the Upper Miocene, offshore Sarawak: Constraints on pore fluid chemistry and diagenetic history  

SciTech Connect

The cored sequence of the Upper Miocene reservoir of Baram field, offshore Sarawak, consists of cyclic deltaic-related quartz-rich sandstones and mudstones interpreted to have been deposited during storm events in shallow to midshelf water depths. The sequence is intercalated with minor tidal intervals. Authigenic siderite is common in sandstones throughout the sequence. Siderite cemented zones are up to 2 m thick. The cement is found in four different sandstone types: laminated sandstone, massive sandstone, bioturbated sandstone, and in association with shell fragments. Whole-rock XRD gives estimates of 20 to 40% siderite in bioturbated sandstones and 10 to 25% for the others. Petrographic analysis reveals that diagenetic siderite occurs in four different crystal morphologies: rhombic, [open quotes]bundles,[close quotes] acicular, and cylindrical. The rhombic siderite, which commonly occurs in bioturbated sandstone, has the most adverse effect on the poroperm characteristics of the sandstones, reducing porosity to 10% and permeability to 2 md. [sigma][sup 13]C and [sigma][sup 18]O plots show groupings based on morphology. Bundled and acicular siderite show ranges of [sigma][sup 13]C[sub PDB] of [minus]15 to [minus]25 and [sigma][sup 18]O[sub PDB] of 0 to [minus]1. The late Miocene seawater [sigma][sup 18]O estimate for the region is [minus]0.8 PDB. This would give the bundles/acicular siderite a temperature of formation range of 26[degrees] to 30[degrees]C. The [sigma][sup 18]O values are compatible with precipitation at shallow burial depth from unaltered seawater; [sigma][sup 13]C values are inherited from sulfate reduction horizons. Rhombic siderite has ranges of [sigma][sup 13]C[sub PDB] of [minus]5 to [minus]15 and [sigma][sup 18]O[sub PDB] of [minus]3 to [minus]4. The range of [sigma][sup 13]C indicates that siderite diagenesis occurred within both the shallow sulfate reduction zone and at deeper levels within the zone of decarboxylation.

Abdul Hadi, A.R.; Astin, T.R. (Univ. of Reading (United Kingdom))

1994-07-01

360

Deformation History of the Paleocene Quottoon Pluton (British Columbia) at 54N: Constraints From Paleomagnetism and Miocene Dike Orientations  

NASA Astrophysics Data System (ADS)

New paleomagnetic results from the Paleocene Quottoon pluton (Douglas Channel, Coast Mountains, British Columbia) and the orientations of Miocene dikes that intrude it reveal two episodes of deformation that correlate with regional events. The very-well determined site-mean remanence directions from 15 sites in the tonalite intrusion form two spatially-distinct groups with declinations that are substantially (63 deg and 40 deg) CCW of the appropriate NAM reference direction. The trends of over 100 dikes intruding the Quottoon do not appear to have been dispersed by this differential vertical-axis rotation, strongly suggesting that the deformation (an oroclinal bending known as the Hawkesbury Warp) predated dike intrusion at approximately 20 Ma. The orocline may be the result of southward decreasing amounts of E-W extension related to development of the Queen Charlotte Basin Remanence directions from the Quottoon also show evidence of block tilting manifested as inclinations significantly steeper or shallower than expected. These tilt domains (a few km wide) are smaller in scale than the vertical-axis rotation domains (10s of km wide). Large jumps in site-mean inclinations between tilt-domains occur over distances as short as 0.5 km, suggesting that boundaries between the domains are sharp. Of the 7 domains, 6 are tilted W-side or NW-side up, a pattern that is at odds with alternatives to the "Baja BC" hypothesis that invoke ubiquitous NE-side-up tilting to explain anomalous paleomagnetic results from Cretaceous plutons in the Coast Mountains. Restoring the blocks to their pre-tilt orientations (and applying the same rotations to dikes that intrude them) steepens the average dip of the dikes by 4 deg to 85 deg, suggesting that block-tilting was post-mid-Miocene. Furthermore, tilt magnitudes along a transect perpendicular to the length of the orogen mimic a smooth, V- shaped trend in (U-Th)/He-in-apatite ages, with the location of maximum tilting corresponding to the youngest age (2.8 Ma). This correlation suggests that post-4 Ma erosionally-driven exhumation may have caused the tilting.

Bogue, S. W.; Rusmore, M. E.; Farley, K. A.

2007-12-01

361

Molecular evidence for ten species and Oligo-Miocene vicariance within a nominal Australian gecko species (Crenadactylus ocellatus, Diplodactylidae)  

PubMed Central

Background Molecular studies have revealed that many putative 'species' are actually complexes of multiple morphologically conservative, but genetically divergent 'cryptic species'. In extreme cases processes such as non-adaptive diversification (speciation without divergent selection) could mask the existence of ancient lineages as divergent as ecologically and morphologically diverse radiations recognised as genera or even families in related groups. The identification of such ancient, but cryptic, lineages has important ramifications for conservation, biogeography and evolutionary biology. Herein, we use an integrated multilocus genetic dataset (allozymes, mtDNA and nuclear DNA) to test whether disjunct populations of the widespread nominal Australian gecko species Crenadactylus ocellatus include distinct evolutionary lineages (species), and to examine the timing of diversification among these populations. Results We identify at least 10 deeply divergent lineages within the single recognised species Crenadactylus ocellatus, including a radiation of five endemic to the Kimberley region of north-west Australia, and at least four known from areas of less than 100 km2. Lineages restricted to geographically isolated ranges and semi-arid areas across central and western Australia are estimated to have began to diversify in the late Oligocene/early Miocence (~20-30 mya), concurrent with, or even pre-dating, radiations of many iconic, broadly sympatric and much more species-rich Australian vertebrate families (e.g. venomous snakes, dragon lizards and kangaroos). Conclusions Instead of a single species, Crenadactylus is a surprisingly speciose and ancient vertebrate radiation. Based on their deep divergence and no evidence of recent gene flow, we recognise each of the 10 main lineages as candidate species. Molecular dating indicates that the genus includes some of the oldest vertebrate lineages confounded within a single species yet identified by molecular assessments of diversity. Highly divergent allopatric lineages are restricted to putative refugia across arid and semi-arid Australia, and provide important evidence towards understanding the history and spread of the Australian arid zone, suggesting at a minimum that semi-arid conditions were present by the early Miocene, and that severe aridity was widespread by the mid to late Miocene. In addition to documenting a remarkable instance of underestimation of vertebrate species diversity in a developed country, these results suggest that increasing integration of molecular dating techniques into cryptic species delimitation will reveal further instances where taxonomic conservatism has led to profound underestimation of not only species numbers, but also highly significant phylogenetic diversity and evolutionary history.

2010-01-01

362

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

NASA Astrophysics Data System (ADS)

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 9-6.5 Ma. Additionally, we present results that demonstrate that deposits in Peruvian Amazonia attributed to Miocene tidal environments are actually fluvial sediments that have been misinterpreted (both environmentally and chronologically) by several authors. The entire Late Miocene sequence was deposited in a continental environment within a subsiding basin. The facies analysis, fossil fauna content, and palynological record indicate that the environment of deposition was dominated by avulsive rivers associated with megafan systems, and avulsive rivers in flood basins (swamps, lakes, internal deltas, and splays). Soils developed on the flatter, drier areas, which were dominated by grasslands and gallery forest in a tropical to subtropical climate. These Late Miocene sediments were deposited from westward of the Purus arch up to the border of Brazil with Peru (Divisor Ranges) and Bolivia (Pando block). Eastward of the Iquitos structural high, however, more detailed studies, including vertebrate paleontology, need to be performed to calibrate with more precision the ages of the uppermost levels of the Solimões Formation. The evolution of the basin during the late Miocene is mainly related to the tectonic behavior of the Central Andes (˜ 3°-15°S). At approximately 5 Ma, a segment of low angle of subduction was well developed in the Nazca Plate, and the deformation in the Subandean foreland produced the inland reactivation of the Divisor/Contamana Ranges and tectonic arrangements in the Eastern Andes. During the Pliocene southwestern Brazilian Amazonia ceased to be an effective sedimentary basin, and became instead an erosional area that contributed sediments to the Amazon fluvial system. At that time, the lowland fluvial systems of southwestern Amazonia (the Purus, Jurua and Javarí basins) become isolated from the Andes by the newly formed north-flowing Ucayali system and south-east flowing Madre de Dios System. It was during the early Pliocene that the Amazon fluvial system integrated regionally and acquired its present appearance, and also when it started to drain water and sediments on a large scale to the Atlantic Ocean.

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

2010-05-01

363

Southeast Atlantic upwelling intensity changes influencing late Miocene C4 plant expansion?  

NASA Astrophysics Data System (ADS)

The Late Miocene epoch (about 15 to 5 Myrs BP) is characterised by fundamental changes in Earth's climate system: turnovers in marine and terrestrial biota, sea-level variability, changes in surface- und deep-water circulations, and increase in upwelling intensities along the coasts [1,2]. During the transition period the Antarctic ice sheets expanded and were permanently established, while additionally ice volumes began to fluctuate [1]. Plants acting with the C4 concentrating mechanism of CO2 fixation for photosynthesis expanded nearly simultaneous at different places in the world, whereas the global CO2 levels exhibit no corresponding change [1,3]. However, C4 plants are also known to have a competitive advantage in habitats of higher temperature, light and fire intensities as well as of limited water supply, compared to the almost ubiquitous C3 plants. This study tries to give insights to Miocene climatic conditions in Southwest Africa and how these conditions may be linked to the C4 plant expansion. We focused on data from a sediment core of the Ocean Drilling Program (Leg 175, ODP 1085A), which span about 10 Myrs of the late Miocene. The core is situated in the Cape basin at the south-western African continental margin in the upwelling zone of the Benguela coastal current. The current brings cold, nutrient-rich waters from South Atlantic and the Antarctic circumpolar current to the surface water along the coast of Southwest Africa. Miocene sea surface temperatures (SST) were reconstructed by two indices, tetraether index (TEX86) and an alkenone based index (U37K'). Both trends exhibit a shift to cooler temperatures from around 27 to 18? C, but are different in rate and timing. Especially by TEX86 reconstructed SSTs exhibit a similar trend as found for ice volume changes shown by the ?18O curve [4]. These findings may reflect an intensification of the Benguela upwelling current during the late Miocene, probably in association with the formation of West Antarctic ice sheet. The increased upwelling enhances the marine primary production shown by a small overall shift in the total organic carbon (TOC) content (

Rommerskirchen, F.; Condon, T.; Mollenhauer, G.; Schefuß, E.

2009-04-01

364

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

365

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

366

Multivariate statistical analyses of palynodebris from the Middle Miocene of the Niger Delta and their environmental significance  

SciTech Connect

Fourteen types of palynodebris have been identified in Middle Miocene reservoir sediments from the Niger Delta. They include palynomorphs, cuticle, parenchyma, resins, black debris, woody fragments and degraded components. The palynodebris types were interpreted by Principal Components Analysis and Average Linkage Cluster Analysis. Four assemblages of samples emerged and they have been grouped into two palynofacies associations, A/C and B/D, because of their correlation with mudstone and muddy heterolithic lithofacies and sandstone lithofacies, respectively. The significant palynodebris components are black debris, parenchyma, resins and amorphous organic matter. The size, shape and texture of all the components were integrated with sedimentological features, palynomorph and foraminiferal assemblages to recognize seven, possibly eight, deltaic sub-environments of deposition in the reservoir. Mudstones and muddy heteroliths from low energy depositional environments are characterized by small-sized, lath-shaped woody debris, and high concentration of buoyant components such as palynomorphs, cuticles and degraded bundles. The sandstones contain larger and more equidimensional woody fragments. These sediments are also richer in black debris which are believed to be a function of exposure to oxidizing conditions for a longer period of time. Parenchyma and resins, though rare, are characteristic of distributary channel-fill sandstones. 59 refs., 7 figs., 3 tabs.

Oboh, F.E. (Univ. of Missouri, Rolla (United States))

1992-12-01

367

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

368

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

USGS Publications Warehouse

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

Peek, Harry M.; Anders, Robert B.

1955-01-01

369

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

370

Depositional patterns and hydrocarbon occurrence in middle to upper Miocene strata in part of the western Niger Delta Basin, Nigeria  

NASA Astrophysics Data System (ADS)

The relation of depositional patterns to hydrocarbon occurrence in middle to upper Miocene strata of part of the western Niger Delta Basin is postulated from the study of electrical logs, radiometric logs, lithologic logs, bottom hole temperatures, intervals of hydrocarbon occurrence and paleontological data. Alternating sands and shales of the Agbada Formation were deposited in the area (up to 720 m, middle Miocene and 510 m, upper Miocene) mainly as regressive off lap sequences in a paralic environment with depo-centers located in the south of the study area. Three deltaic facies can be recognized based on the relative amounts of shale and sand including, proximal delta front facies (>70% sand), distal delta front facies (30-70% sand) and prodelta facies (<30% sand). The upper Miocene is generally sandier than the middle Miocene as a result of south-westerly progradation of delta front facies from middle to upper Miocene. Geothermal gradients in the area range from 2.5 °C/100 m to 4.4 °C/100 m. Isothermal maps show that some middle to upper Miocene shales could have undergone catagenesis to become mature source rocks. Three depositional zones (A, B, C) corresponding to dominant depositional facies i.e., proximal delta, distal delta and prodelta respectively, have been delineated from sand percentage maps. There is a progression of these zones from A through B to C in a generally south-westerly direction (the direction of delta progradation). Data for hydrocarbon intervals reveal the predominance of hydrocarbons in Zone C due to high entrapment potentials and to a lesser extent in Zone B. Zone A is barren as a result of poor entrapment potentials. The juxtaposition of distal delta front sands and prodelta mud could have initiated growth faults which constitute the major types of traps in the basin.

Agyingi, C. M.; Agagu, O. K.; Fozao, K. F.; Njoh, O. A.; Ngalla, N.

2013-04-01

371

Evidence for Late Oligocene-Early Miocene episode of transtension along San Andreas Fault system in central California  

SciTech Connect

The San Andreas is one of the most intensely studied fault systems in the world, but many aspects of its kinematic history remain controversial. For example, the period from the late Eocene to early Miocene is widely believed to have been a time of negligible strike-slip movement along the San Andreas fault proper, based on the rough similarity of offset of the Eocene Butano-Point of rocks Submarine Fan, the early Miocene Pinnacles-Neenach volcanic center, and an early Miocene shoreline in the northern Gabilan Range and San Emigdio Mountains. Nonetheless, evidence indicates that a late Oligocene-early Miocene episode of transtension, or strike-slip motion with a component of extension, occurred within the San Andreas fault system. The evidence includes: (1) about 22-24 Ma, widespread, synchronous volcanic activity occurred at about 12 volcanic centers along a 400-km long segment of the central California coast; (2) most of these volcanic centers are located along faults of the San Andreas system, including the San Andreas fault proper, the San Gregorio-Hosgri fault, and the Zayante-Vergeles fault, suggesting that these and other faults were active and served as conduits for magmas rising from below; (3) during the late Oligocene and early Miocene, a pull-apart basin developed adjacent to the San Andreas fault proper in the La Honda basin near Santa Cruz; and (4) during the late Oligocene and early Miocene, active faulting, rapid subsidence, and marine transgression occurred in the La Honda and other sedimentary basins in central California. The amount of right-lateral displacement along the San Andreas fault proper during this transtentional episode is unknown but was probably about 7.5-35 km, based on model studies of pull-apart basin formation. This small amount of movement is well within the range of error in published estimates of the offset of the Eocene to early Miocene geologic features noted.

Stanley, R.G.

1986-04-01

372

Paleomagnetic study of late Miocene through Pleistocene igneous rocks from the southwestern USA: Results from the historic collections of the U.S. Geological Survey Menlo Park laboratory  

NASA Astrophysics Data System (ADS)

Seventy sites from the southwestern United States provide paleomagnetic results that meet certain minimum criteria and can be considered for the Time-Averaged Field Initiative (TAFI). The virtual geomagnetic poles for these 70 units are circularly distributed, and their mean is nearly coincident with the rotational axis. When other published data for the southwestern United States are included (N = 146), the virtual geomagnetic poles are again circularly distributed, but their mean is significantly displaced from the rotational axis. Whichever of these data sets is used, the mean poles for normal- and reversed-polarity data differ by ˜170° and are not antipodal at greater than 95% confidence. When the data are separated into specific age groups, the 95% confidence limits about the mean poles for the Brunhes, Matuyama, combined Gauss/Gilbert, and late Miocene intervals all include the rotational axis. Angular dispersion about these four mean poles increases systematically with increasing age and is consistent with paleosecular variation Model "G."

Mankinen, Edward A.

2008-05-01

373

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

374

Paleogeographic and geodynamic Miocene evolution of the Tunisian Tell (Numidian and Post-Numidian Successions): bearing with the Maghrebian Chain  

NASA Astrophysics Data System (ADS)

The Numidian and Post-Numidian stratigraphy of the Tunisian Tell has been updated based on 16 stratigraphic sections belonging to the Massylian sub-domain of the Maghrebian Flysch Basin and to the External Domain. The new data concern detailed litho- and biostratigraphy, gaps, synchronous marker levels, lateral correlations, tectonic contacts, etc. The successions studied show many diachronous and unconformity boundaries delimiting sedimentary depositional sequences related to some tectonic/sedimentary processes. Two main Miocene sedimentary successions (Numidian and Post-Numidian) are recognized overlying the Sub-Numidian Succession (pre-Early Aquitanian) by new integrated (planktonic foraminifera and calcareous nannoplankton) chronostratigraphic analyses, allowing an update of the formations studied. The Miocene tectonic/sedimentary relationships and the timing of the deformation are summarized as follows: (1) the activation of a foredeep stage and a tectogenesis phase gives rise to an accretionary orogenic wedge during mainly the Early Miocene; (2) a late-orogenic phase is checked in the Late Burdigalian-Early Langhian characterized by a marine glauconitic terrigenous sedimentation; (3) a post-orogenic generalized phase is confirmed from the Middle Miocene on in shallow marine or continental sedimentation. These results show good correlation along the Maghrebian Chain and Betic Cordillera. Finally, a paleogeographic and geodynamic evolutionary model concerning the Miocene African Tunisian Margin is postulated.

Belayouni, Habib; Guerrera, Francesco; Martín-Martín, Manuel; Serrano, Francisco

2012-10-01

375

Paleogeographic and geodynamic Miocene evolution of the Tunisian Tell (Numidian and Post-Numidian Successions): bearing with the Maghrebian Chain  

NASA Astrophysics Data System (ADS)

The Numidian and Post-Numidian stratigraphy of the Tunisian Tell has been updated based on 16 stratigraphic sections belonging to the Massylian sub-domain of the Maghrebian Flysch Basin and to the External Domain. The new data concern detailed litho- and biostratigraphy, gaps, synchronous marker levels, lateral correlations, tectonic contacts, etc. The successions studied show many diachronous and unconformity boundaries delimiting sedimentary depositional sequences related to some tectonic/sedimentary processes. Two main Miocene sedimentary successions (Numidian and Post-Numidian) are recognized overlying the Sub-Numidian Succession (pre-Early Aquitanian) by new integrated (planktonic foraminifera and calcareous nannoplankton) chronostratigraphic analyses, allowing an update of the formations studied. The Miocene tectonic/sedimentary relationships and the timing of the deformation are summarized as follows: (1) the activation of a foredeep stage and a tectogenesis phase gives rise to an accretionary orogenic wedge during mainly the Early Miocene; (2) a late-orogenic phase is checked in the Late Burdigalian-Early Langhian characterized by a marine glauconitic terrigenous sedimentation; (3) a post-orogenic generalized phase is confirmed from the Middle Miocene on in shallow marine or continental sedimentation. These results show good correlation along the Maghrebian Chain and Betic Cordillera. Finally, a paleogeographic and geodynamic evolutionary model concerning the Miocene African Tunisian Margin is postulated.

Belayouni, Habib; Guerrera, Francesco; Martín-Martín, Manuel; Serrano, Francisco

2013-04-01

376

Origin of a Late Eocene to pre-Miocene buried crater and breccia lens at Fohn-1, North Bonaparte Basin, Timor Sea: A probable extraterrestrial connection  

NASA Astrophysics Data System (ADS)

Seismic reflection data and an at least 350 m thick PGE-rich carbonate breccia lens intersected by the Fohn-1 exploration well in the Timor Sea, off northern Australia, are interpreted in terms of a buried 4.8 km-diameter impact crater of late Eocene to pre-Miocene age. The crater displays the classic elements of impact structures, including a central uplift, ring syncline and upraised rims. The presence in the breccia of redeposited Campanian and Maastrichtian microfossils suggests rebound of strata from levels deeper than 1250 m below the pre-Miocene unconformity. Morphometric modelling suggests an original crater depth of ~450 m which, in view of the >350 m thickness of the breccia section, places a limit of <100 m on the amount of post impact erosion. Stratigraphic and palaeontological evidence suggests that the impact occurred between 36 and 24.6 Ma. The breccia contains a pseudotachylite component enriched in the inert platinum group elements (PGE) (Ir, Ru) by factors of 5-12 above the values of common sediments. The more mobile PGE (Os, Pt, Pd) show a wide scatter and terrestrial-type values. Opposite geochemical/stratigraphic trends pertain to different PGE species - the relatively inert Ir-Ru group shows an overall concentration at the base of the section, whereas the more mobile Os shows peaks at median levels of the section - suggesting upward diagenetic leaching. The near-chondritic PGE patterns at the base of the breccia pile are accompanied by near chondritic Ni/Cr, Co/Cr, Ni/Ir, Ni/Pt, and Cu/Pd ratios. Departure from these values related to alteration at higher levels in the breccia pile is accompanied with high Sulphur levels (~1%).

Gorter, John D.; Glikson, Andrew Y.

2000-03-01

377

Miocene carbonate reservoirs related to tectonic and thermal evolution of southeast Asian marginal basins  

SciTech Connect

The early Miocene global sea level rise and oceanic warming period allowed the tropical reef growth belt to expand and fostered the development of major carbonate buildups throughout southeast Asia. A regional paleogeographic reconstruction for 18 m.y. places reefal, shelf, and basinal facies in a tectonic setting of island arcs, subduction zones, and marginal basins. For typical basins, such as the Sulu, Celebes, and South China Sea basins, basin formation and sedimentation models have been developed based on ages inferred from identified marine magnetic anomalies and heat flow data. These basins have many of the attributes needed for hydrocarbon development and maturation. They accumulated sediment from pelagic sources and surrounding island arcs and landmasses fringed by reefs. During the early Miocene, limited water circulation in restricted basins, such as the Sulu and Celebes basins, may have induced dysaerobic conditions that enhanced organic carbon preservation. Models of marginal basin formation provide the basis for studying the time-dependent thermal histories of their sediment sequences. The authors models show that, for example, lower Miocene sediments deposited at a rate of 100 m/m.y. on 20-m.y.-old crust in a typical basin have just entered the oil-generation window. Lower sedimentation rates require deposition on younger crust in order for the sediments to reach an equivalent maturation stage. Estimates of the hydrocarbon potential of such marginal basins should be based on a sequential time-slice analysis of each basin in terms of sediment type, sedimentation rate, sea floor age and thermal regime, and the presence of reservoirs.

Fulthorpe, C.S.; Brodholt, J.P.; Jurdy, D.M.; Schlanger, S.O.

1986-05-01

378

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

379

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

380

Tectono-sedimentary characteristics of Late Miocene-Quaternary extensional basins of the Northern Apennines, Italy  

NASA Astrophysics Data System (ADS)

Extensional and compressional regimes exist at the same time in adjacent parts of the Northern Apennines (Italy), and the former regime succeeded the latter at the same place as the thrust mountain front moved eastward since Miocene times. Numerous extensional basins have developed west of the present mountain divide. The westernmost ones formed over attenuated continental crust since Late Miocene and have been subjected to several subsidence and uplift events, with rates of subsidence generally faster than rates of sedimentation. They contain continental deposits overlain by gypsum-bearing Upper Miocene marine sequences and siliciclastic, marine Pliocene deposits. These basins were affected by shallow magmatism and are still experiencing high geothermal gradient and late to post-magmatic activities, such as in the renowned thermal region of Larderello. To the east, closer to the present mountain divide, the extensional basins formed later, from Pliocene to Quaternary, contain continental (fluvial and lacustrine) deposits and have not experienced near-surface magmatic activities. The sedimentary fill architecture of the Apennine extensional basins is similar to that of other European, American and African extensional or transtensional systems. For instance, a common characteristic is the prevalence of large alluvial fan deposits at the hanging-wall shoulder of half-grabens, coarser, smaller, alluvial fans at the footwall shoulder, and some fluvial deposits introduced longitudinally. Unlike the African rifts though, the sedimentary facies distribution of extensional basins which developed in active orogenic zones such as in the Apennines, may be strongly affected by uplifting, steep mountain slopes and can have large, thick, coarse alluvial fans also on the footwall side of the half-grabens.

Martini, I. P.; Sagri, M.

1993-06-01

381

Modeling Freshwater Impacts on Ocean Circulation During the Miocene at 20 and 14 Ma  

NASA Astrophysics Data System (ADS)

A large modeling effort has been committed to better understand the role of freshwater impacts on the past climates, the thermohaline ocean circulation (THC) patterns, and variations of sea level. The restructuring of the THC may be caused by many factors, including ice sheets melting of the major ice sheets, sea ice melting and forming, and for long-term variability - also by changes in major gateways. The sensitivity of the past THC to freshwater fluxes could depend critically on the land-sea distribution and thus be different from the present-day. However, our understanding of the role of paleogeography in THC dynamics and climate change is not yet complete. There is a consensus that the Cenozoic cooling trend and southern glaciation during the last 25 million years was largely caused by continental drift and bathymetrical changes. In the Southern Hemisphere, the Miocene marks further widening of the ocean passage between Antarctica and Australia, the opening of the Drake Passage, and therefore the emergence of the fully developed Antarctic Circumpolar Current. We focus on two different Miocene time slices (20 and 14 Ma), which are characterized by major transitions from warm to cold polar climate. In a series of numerical experiments, we show that the Miocene THC is noticeably sensitive to both the geographical conditions and to the southern high-latitudinal freshwater pulses that might have been caused by young cryosphere evolution. Our coupled ocean-atmosphere simulation reveals changes in all major ocean circulation parameters - the ocean heat transport, meridional overturning, sea level, etc. The sensitivity to freshwater impacts appears to be a function of land-sea distribution and is different at all three points on the timeline - the two paleo time slices and the present one.

Haupt, B. J.; Seidov, D.

2004-12-01

382

Molar crown formation in the Late Miocene Asian hominoids, Sivapithecus parvada and Sivapithecus indicus.  

PubMed

During the past decade, studies of enamel development have provided a broad temporal and geographic perspective on evolutionary developmental biology in Miocene hominoids. Here we report some of the first data for molar crown development in one hominoid genus, Sivapithecus. The data are compared to a range of extant and extinct hominoids. Crown formation times (CFTs), daily rates of enamel secretion (DSR), Retzius line number and periodicity, and relative enamel thickness (RET) were calculated in a mandibular first molar of Sivapithecus parvada and a maxillary first molar of Sivapithecus indicus from the Siwalik sequence of Pakistan. A CFT of 2.40 years for the protoconid of S. parvada and 2.25 years for the protocone of S. indicus lie within the range of first molar (M1) formation times for the majority of Miocene hominoids (1.96-2.40 years, excluding Proconsul heseloni), and are similar to an M(1) from Gorilla (2.31 years) and M(1)s from Pan (2.22-2.39 years). This is unlike the longer CFTs in modern humans, which appear to be linked with their extended growth period. In contrast to extant great apes and humans, daily rates of enamel secretion are rapid in the Sivapithecus M1s during the early stages of growth, which seems to be a common pattern for most Miocene apes. The rapid accumulation of cuspal enamel in the Sivapithecus molars produced thicker enamel than either Pan or Gorilla in a comparable period of time. Future studies on larger samples of living and fossil hominoids are needed to clarify trends in crown development, which may be better understood in the context of life history strategies coupled with good data on body mass and brain size. PMID:17512035

Mahoney, Patrick; Smith, Tanya M; Schwartz, Gary T; Dean, Christopher; Kelley, Jay

2007-05-23

383

Atmosphere, ecology and evolution: what drove the Miocene expansion of C4 grasslands?  

PubMed Central

Grasses using the C4 photosynthetic pathway dominate today's savanna ecosystems and account for ?20% of terrestrial carbon fixation. However, this dominant status was reached only recently, during a period of C4 grassland expansion in the Late Miocene and Early Pliocene (4–8 Myr ago). Declining atmospheric CO2 has long been considered the key driver of this event, but new geological evidence casts doubt on the idea, forcing a reconsideration of the environmental cues for C4 plant success. Here, I evaluate the current hypotheses and debate in this field, beginning with a discussion of the role of CO2 in the evolutionary origins, rather than expansion, of C4 grasses. Atmospheric CO2 starvation is a plausible selection agent for the C4 pathway, but a time gap of around 10 Myr remains between major decreases in CO2 during the Oligocene, and the earliest current evidence of C4 plants. An emerging ecological perspective explains the Miocene expansion of C4 grasslands via changes in climatic seasonality and the occurrence of fire. However, the climatic drivers of this event are debated and may vary among geographical regions. Uncertainty in these areas could be reduced significantly by new directions in ecological research, especially the discovery that grass species richness along rainfall gradients shows contrasting patterns in different C4 clades. By re-evaluating a published data set, I show that increasing seasonality of rainfall is linked to changes in the relative abundance of the major C4 grass clades Paniceae and Andropogoneae. I propose that the explicit inclusion of these ecological patterns would significantly strengthen climate change hypotheses of Miocene C4 grassland expansion. Critically, they allow a new series of testable predictions to be made about the fossil record. Synthesis. This paper offers a novel framework for integrating modern ecological patterns into theories about the geological history of C4 plants.

Osborne, Colin P

2008-01-01

384

Coarse-grained deltaic sedimentation in the Miocene Cuyama strike-slip basin, California coast ranges  

SciTech Connect

The Cuyama basin, located in the southern Coast Ranges southwest of the San Andreas fault developed early in the history of the San Andreas transform system. The Miocene marine basin formed in a transtensional setting along a dextral strike-slip fault of the transform system, the San Juan-Chimineas fault following Oligocene nonmarine basin formation in an extensional setting. The lower and middle Miocene Vaqueros Formation in the northwestern part of the basin, which represents the first of two transgressive-regressive cycles, consists of eight facies making up two depositional systems. The 400-m-thick Soda Lake Shale Member constitutes a basinal system consisting of deep-basin and starved-basin facies. The overlying 2,200-m-thick Painted Rock Sandstone Member consists mostly of coarse-grained, pebbly sandstone and constitutes a deltaic depositional system of prodelta, slope channel, delta front, tidal channel, interdistributary bay, and fluvial channel facies. The basinal depositional system consists of turbidite sand and mud, and hemipelagic and pelagic sediments that were deposited in a rapidly subsiding basin. The deltaic depositional system prograded into the deep basin and had a steep prodelta slope that extended to bathyal depths. The delta is inferred to be a river-dominated fan delta in which coarse sediment was transported down the prodelta slope into deep water by sediment gravity flows. The overall basin history and geometry of the northwestern Cuyama basin are typical of strike-slip basins. The initial rapid subsidence to bathyal depths at rates of more than 500 m/m.y. in the early Miocene is interpreted to be a result of extension at the releasing bend of a dextral strike-slip fault.

Bartow, J.A. (Geological Survey, Menlo Park, CA (USA))

1990-05-01

385

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

386

Rapid syn-convergent Exhumation of Miocene-aged Lower Orogenic Crust in the Eastern Himalaya  

NASA Astrophysics Data System (ADS)

Rare granulitized eclogites exposed in the eastern Himalaya provide an insight into conditions and processes deep within the orogen. SHRIMP U-Pb, Ti and REE data from zircons in mafic granulitized eclogites located in the upper structural levels of the GHS in Bhutan show that zircon crystallized under eclogite facies metamorphic conditions, between 15.3 ± 0.3 and 14.4 ± 0.3 Ma, within a couple of million years of the later granulite-facies overprint. In conjunction with pressure estimates of the eclogite and granulite facies stages of metamorphism, the age data suggest that initial exhumation occurred at plate tectonic rates (cm yr-1). These extremely rapid syn-convergence exhumation rates during the later stages of the India-Asia collision require a revision of theories about how crustal materials are transported and exhumed during continental collisions. In contrast to western Himalayan examples, the eastern Himalayan eclogites cannot be tectonically related to steep subduction of India beneath Asia. Instead, they more likely represent fragments from the base of the over-thickened Tibetan crust. Based on the zircon age and trace element data we hypothesize that the protolith of the mafic granulites are Middle Miocene mafic intrusions into the lower crust of southern Tibet, linked to the Miocene volcanism in the Lhasa block. We suggest that a transient tectonic event, possibly the indenting of a strong Indian crustal ramp into crust under southern Tibet weakened by partial melting, may have promoted exhumation of the eclogitized lower crust under Tibet. Mafic magmatism and volcanism themselves may be related to the convective thinning of the lithospheric mantle triggered by the reduction in India-Eurasia convergence rate during the Middle Miocene, which in turn could have helped the rapid extrusion of the lower crust over the earlier exhumed middle crust.

Grujic, D.; Warren, C. J.; Wooden, J. L.

2011-12-01

387

Atmosphere, ecology and evolution: what drove the Miocene expansion of C(4) grasslands?  

PubMed

Grasses using the C(4) photosynthetic pathway dominate today's savanna ecosystems and account for approximately 20% of terrestrial carbon fixation. However, this dominant status was reached only recently, during a period of C(4) grassland expansion in the Late Miocene and Early Pliocene (4-8 Myr ago). Declining atmospheric CO(2) has long been considered the key driver of this event, but new geological evidence casts doubt on the idea, forcing a reconsideration of the environmental cues for C(4) plant success.Here, I evaluate the current hypotheses and debate in this field, beginning with a discussion of the role of CO(2) in the evolutionary origins, rather than expansion, of C(4) grasses. Atmospheric CO(2) starvation is a plausible selection agent for the C(4) pathway, but a time gap of around 10 Myr remains between major decreases in CO(2) during the Oligocene, and the earliest current evidence of C(4) plants.An emerging ecological perspective explains the Miocene expansion of C(4) grasslands via changes in climatic seasonality and the occurrence of fire. However, the climatic drivers of this event are debated and may vary among geographical regions.Uncertainty in these areas could be reduced significantly by new directions in ecological research, especially the discovery that grass species richness along rainfall gradients shows contrasting patterns in different C(4) clades. By re-evaluating a published data set, I show that increasing seasonality of rainfall is linked to changes in the relative abundance of the major C(4) grass clades Paniceae and Andropogoneae. I propose that the explicit inclusion of these ecological patterns would significantly strengthen climate change hypotheses of Miocene C(4) grassland expansion. Critically, they allow a new series of testable predictions to be made about the fossil record.Synthesis. This paper offers a novel framework for integrating modern ecological patterns into theories about the geological history of C(4) plants. PMID:18784799

Osborne, Colin P

2008-01-01

388

Miocene Indian Ocean Circulation: A High-Resolution Multivariate Analysis of Interbasinal Records  

NASA Astrophysics Data System (ADS)

Ocean circulation in the Indian Ocean during the Miocene progresses through three configurations in response to changes in plate movement and global climate. Principal Component Analysis (PCA) was carried out on benthic foraminifera, stable isotope and sedimentological data sampled at 100 kyr intervals from cores recovered from ODP sites 237, 707, 709 and 710 in the Somali Basin (SOB) and sites 214, 216 and 238 in the Mid-Indian Basin (MIB). These analyses provide insight into the structure and dynamics of the Indian Ocean through most of the Miocene (25--6 Ma) and suggest forcing mechanisms of the circulation system in this and adjacent ocean basins. Bulk responses of infaunal and epifaunal species mask local and regional oceanic signals that this study extracts by analysis at the species level. Isotopic ratios are used to describe the depth structure of the two basins. Coupled with sedimentological data, the dynamics of the basins is described in terms of the major events of the Miocene, namely Tethyan closure, the growth of the West Antarctic Ice Sheet (WAIS) and the initiation of the monsoon. PCA of the time series data show three separate components which correlate with these three phases in the history of the Indian Ocean. These are: i) 25-18 Ma, a stratified SOB with warm dense Tethyan outflow waters (TOW) underlying cooler, less dense water that is weakly coupled across the Chagos- Laccadive Ridge (CLR) with an unstratified MIB; ii) 18-12 Ma, mixing in the SOB as TOW diminishes due to seaway closure, and increasing cool bottom waters which penetrate further north with time, accompanied by stratification of the MIB and stronger coupling of surface waters promoting nutrient transfer eastwards; iii) 12-6 Ma, overturn and upwelling in the SOB with occasional strong fluxes of cooler WAIS bottom water and strong stratification in the MIB, with a westerly flux of warm water overtopping a more greatly subsided CLR.

Irving, D. H.; Smart, C.; Ramsay, A. T.; Thomas, E.

2006-12-01

389

Latest Miocene and Pliocene paleoceanographic condition in the Southern Ocean based on silicoflagellate assemblage  

NASA Astrophysics Data System (ADS)

Integrated Ocean Drilling Program (IODP) Expedition 318 succeeded to recover the sediment cores near Wilkes Land in the East Antarctica during January-March 2010. Sediments of Site U1359A and U1359D on the Wilkes Land continental margin were deposited during the Pleistocene to mid-late Miocene. Detailed silicoflagellates records in these sediments reveal the evolution of the water condition changes during the latest Miocene and Pliocene. Dominant taxa were shifted step by step from "pseudofibula plexus" (Distephanus speculum speculum f. pseudofibula, Ds. s.s. varians and Ds. s.s. notabilis) in the latest Miocene to Ds. speculum with Ds. crux and following Ds. speculum in the early Pliocene. Distinct peaks in Dictyocha were observed in the early Pliocene. At present, genus Dictyocha is observed north of the Antarctic polar front (APF), whereas genus Distephanus is dominated south of the APF. Thus, these Dictyocha peaks reflect the surface water warming events as early Pliocene warm events. Based on Dictyocha / Distephanus ratio, Ciesielski and Weaver (1974)'s method, sea-surface temperatures were approximately 5 ?C at the end of early Pliocene and approximately 3 ?C in early Pliocene. Such silicoflagellate evolution pattern at these sites is almost consistent with the patterns of the silicoflagellate variation in the other areas (e.g., in the Kerguelen Plateau and Prydz Bay) of the Southern Ocean. Weakening of the thermal gradient across the Southern Ocean occurred at the early Pliocene warm events due to the high sea surface temperature along at least the entire East Antarctic. Widespread occurrence of the early Pliocene warm events was likely a response to weakening of the deep water circulation.

Katsuki, K.; Khim, B. K.; Song, B.

2012-04-01

390

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

2012-06-06

391

Model study of the Miocene Mediterranean Sea and Paratethys: closure of the Indian gateway  

NASA Astrophysics Data System (ADS)

The proto-Mediterranean Sea and Paratethys were both connected to the Indian Ocean until the Middle Miocene, when the convergence of the Eurasian plate and African-Arabian plate caused the constriction and closure of the Indian gateway. This interrupted the water exchange with the Indian Ocean and gave birth to the present-day Mediterranean basin. Although there are lots of uncertainties concerning the timing of the closure and the consequences that this entailed, it is broadly accepted that it had had a large effect on water properties and ocean dynamics on the regional and global scales, and in that way may have also played a role in the evolution of climate. While, from a modeling perspective, considerable research has been devoted to the Late Miocene period on the Mediterranean region, rather less attention has been paid to the Early and Middle Miocene. The purpose of this work is to investigate the palaeocirculation of the Mediterranean Sea and Paratethys during the different stages of closure. For this purpose we use of a regional ocean model and a Burdigalian (about 20 Ma) palaeogeographic map from the Peri-Tethys Atlas. In the interest of gaining insight into the first-order effects of the gateway evolution on marine circulation, different experiments, ranging from a deep gateway to a completely closed one, have been carried out. In addition, different sets of values for the atmospheric forcing have been applied in order to understand the role of the temperature and net evaporation on the marine circulation and the strait dynamics. The series of experiments allows us to analyze different scenarios, helping us to understand the evolution of such a complex system, and sheds a new light on the interpretation of the sedimentary record. Consequently, the information derived from this work can be useful for other studies focused on strait dynamics and could be a valid starting point for subsequent research on this gateway.

de la Vara Fernandez, Alba; Meijer, Paul Th.; Wortel, Rinus M. J.

2013-04-01

392

Miocene stable isotope record: a detailed deep pacific ocean study and its paleoclimatic implications.  

PubMed

Deep Sea Drilling Project site 289 in the western equatorial Pacific has yielded an extremely detailed record of the carbon and oxygen isotopic changes in the Miocene deep ocean. The isotopic record reflects major changes in paleoclimate and paleoceanography, probably dominated by a major phase of Antarctic ice-cap growth. The transition from a relatively unglaciated world to one similar to today occurred between 16.5 x 10(6) and 13 x 10(6) years before the present, with the greatest change occurring between approximately 14.8 x 10(6) and 14.0 x 10(6) years before the present. PMID:17739401

Woodruff, F; Savin, S M; Douglas, R G

1981-05-01

393

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

394

A fossil grass (gramineae: chloridoideae) from the miocene with kranz anatomy.  

PubMed

A fossil leaf fragment collected from the Ogallala Formation of northwestern Kansas exhibits features found in taxa of the modern grass subfamily Chloridoideae. These include bullet-shaped, bicellular microhairs, dumbbell-shaped silica bodies, cross-shaped suberin cells, papillae, stomata with low dome- to triangular-shaped subsidiary cells, and Kranz leaf anatomy. The leaf fragment extends the fossil record of plants that show both anatomical and external micromorphological features indicating C(4) photo-synthesis back to the Miocene. On the basis of associated mammals, the leaf fragment is assigned a Hemphillian age (7 to 5 million years ago). PMID:17752216

Thomasson, J R; Nelson, M E; Zakrzewski, R J

1986-08-22

395

Miocene ostracod (Crustacea) biostratigraphy of the upper Amazon Basin and evolution of the genus Cyprideis  

NASA Astrophysics Data System (ADS)

The Ostracoda in this study come from an area in the Western Amazon river region shared by Peru, Colombia, and Brazil. Fauna was recovered from 125 samples collected at 26 outcrop localities of the Pebas Formation. Five ostracod zones are proposed and referred mainly to the Middle Miocene. The zonation is based on the stratigraphical distribution of 21 endemic species of the euryhaline genus Cyprideis, probably the largest brackish-water ostracod evolutionary radiation of the American Neogene. This study illustrates that Ostracoda can constitute a useful biostratigraphical tool in such environments as those obtained in the Neogene of the upper Amazon Basin.

Muñoz-Torres, F. A.; Whatley, R. C.; Harten, D. Van

2006-03-01

396

Tectonics of Miocene Pliocene fresh-water molasses in the Carpathian Foredeep (Witów Series, South Poland)  

NASA Astrophysics Data System (ADS)

Normal faults of different orientations appear to be the youngest manifestations of faulting in the Polish Outer Carpathians, composed of the Lower Cretaceous trough Lower Miocene strata, and the related Carpathian Foredeep, which is filled with the Lower to Middle Miocene sediments. In the Outer Carpathians, the folds and thrusts produced by accretion-related shortening were formed between the Paleocene and early Late Miocene. The origin of normal faults is still debatable, since it is not known whether these faults were a result of multidirectional extension produced in a single collapse event, or differently oriented extension proceeding in a series of successive events. Structural studies of the Late Miocene Pliocene(?) fresh-water molasses of the Witów Series provide a possibility to reconstruct the Late Neogene stress field in the central part of the Polish Carpathian Foredeep and, indirectly, in the central part of the Polish Outer Carpathians. The strata of such an age are unique features in the Polish Carpathian Foredeep, proving thereby a key record of structural deformation during the latest stages of orogenic evolution of the Carpathian orogen. The molasses are cut by joints, and normal and strike-slip faults which were formed in two successive events: (1) a syn-depositional one, proceeding under NNW-SSE to N-S oriented horizontal compression, possibly coeval with reactivation of a NE-striking sinistral fault of the Kurdwanów-Zawichost Fault Zone in the basement; and (2) a post-depositional one, during N-S to NE-SW-oriented extension. In the first event, reactivation of the NE-striking sinistral fault led to formation of N-S-oriented joints, as well as NW-striking dextral, and NNW-trending normal faults. This event was probably contemporaneous with sinistral reactivation of some thrusts in the Western Outer Carpathians, induced by eastward-directed extrusion of crustal blocks in the Carpathian internides. In the second event, both W-E and NW-SE-oriented joints and WNW-striking normal faults were formed. The latter most probably originated due to reactivation of the Early Paleocene WNW- and NW-striking normal faults in the basement. Therefore, normal faults detected in the Outer Carpathians and Carpathian Foredeep appear to be a result of not a single collapse event but of different successive events. This extensional episode lasted at least to the late Pleistocene. No evidence for the recent NNE-directed tectonic compressive stress, typical for that segment of the Carpathian arc, has been found yet.

Galicia T. Group; Rauch-W?odarska, Marta; Zuchiewicz, Witold; Brud, Stanis?aw; Galicia T. Group

2006-05-01

397

Determination of mid/late Miocene ice sheet stability: Reconciling oxygen isotopes and sequence stratigraphy  

NASA Astrophysics Data System (ADS)

Values in benthic foraminiferal ?18O records, uncorrected for temperature variations, usually remain relatively constant through the late Serravallian and early Tortonian (˜13-8 Ma) after the major early Serravallian phase of ice-sheet growth (˜15-13 Ma). This has been interpreted to indicate that ice-sheets on Antarctica had remained relatively stable at a time when the Haq et al. (1987) onlap curve displays high amplitude sea level fluctuations. However, when these temperature variations are taken into account to correct the oxygen isotope records using Mg/Ca ratios as proxy for paleothermometry, significant ice volume fluctuations are observed during the time interval spanning the middle to late Miocene transition. Interpretation of sedimentary geometries in the Inner Sea of the Maldive Archipelago provided further evidence for Serravallian/Tortonian ice sheet instability. Other lines of evidence for middle/late Miocene ice sheet instability come from a planktic oxygen isotope record for the Miocene developed at ODP Site 714A near the Maldives. A planktic oxygen isotope record from this site is thought to represent better ice volume variations because the site in the Maldives was nearly equatorial in location when these sediment were deposited. Sea surface temperature changes, therefore, are assumed to have been minimal for this site, and most of the shifts in oxygen isotope ratios are interpreted to be related to ice sheet growth and decay, or sea level changes. This study focuses on the time interval from ˜13.2 Ma to ˜10.1 Ma in Hole 714A in which a benthic ?18O record corrected for temperature changes based upon Mg/Ca variations is compared with the planktic ?18O record and the middle to late Miocene overall global sequence stratigraphy pattern. The uncorrected benthic oxygen isotope curve is offset from the planktic oxygen isotope curve from Hole 714A by ˜3 per mil, reflecting the lower temperatures at ˜2000 meters as compared to sea surface temperatures. The benthic ?18O and planktic d18O curve appear to be in phase with relative high amplitude variations, although the variation in the benthic curve is also of smaller amplitude than the planktic curve. Those fluctuations are interpreted as ice volume fluctuations, because during the same time interval, the Mg/Ca values remain rather constant.

Petter, A.; Droxler, A. W.; Billups, K.; Vincent, E.

2003-04-01

398

Late Miocene (Proto-Gulf) Extension and Magmatism on the Sonoran Margin  

NASA Astrophysics Data System (ADS)

Constraints on the magnitude and character of late Miocene (Proto-Gulf) deformation on the Sonoran margin of the Gulf of California extensional province are key to understanding how and when Baja California was captured by the Pacific plate and how strain was partitioned during the early stages of this transtensional rift system. Our new geologic mapping in southwestern Sonora and 40Ar/39Ar dating of pre-, syn-, and post-tectonic volcanic units indicate that late Miocene deformation and volcanic activity were largely restricted to a NW-trending, 100-120 km wide belt adjacent to the coast. Inboard of this belt, NW-SE extension is mainly older (>15 Ma) and occurred in an intra-arc or back-arc setting. Proto-Gulf deformation within the coastal belt was profoundly transtensional, with NW-striking, dextral strike slip faults operating in concert with N-S and NNE-striking normal and oblique slip faults to produce an inferred NW or NNW tectonic transport direction. The total amount of late Miocene NW directed dextral shear within the coastal belt is still poorly constrained, but may exceed 100 km. The locus of deformation and volcanic activity migrated westward or northwestward within the Sonoran coastal belt. in the eastern portion (Sierra Libre and Sierra El Bacatete) major volcanic activity commenced at ˜13.0 Ma and peaked at 12.0 Ma, and major faulting and tilting is bracketed between 12.0 and 10.6 Ma. Further west in the Sierra El Aguaje/San Carlos region, major volcanic activity commenced at 11.5 Ma and peaked at 10.5 Ma, and most faulting and tilting is bracketed between 10.7 and 9.3 Ma. On the coastal mountains northwest of San Carlos, rift related faulting and tilting continued after 8.5 Ma. Voluminous late Miocene (13-8 Ma) volcanic rocks within the Sonoran coastal belt were erupted from numerous centers (e.g. Sierra Libre, Guaymas, Sierra El Aguaje). These thick volcanic sections are compositionally diverse (basalt to rhyolite, with abundant dacite and andesite), and are intimately associated in space and time with tectonic activity. Overall, the Sonoran coastal belt provides a spectacular example of distributed transtension and associated magmatism that ultimately led to rupturing of the continental lithosphere.

Gans, P.; MacMillan, I.; Roldan-Quintana, J.

2003-12-01

399

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

400

New constrains on the thermal history of the Miocene Jarando basin (Southern Serbia)  

NASA Astrophysics Data System (ADS)

The Jarando basin, located in the internal Dinarides, formed in the course of the Miocene extension affecting the whole Alpine-Carpathian-Dinaride system (Schmid et al., 2008). In the study area Miocene extension led to the formation of a core-complex in the Kopaonik area (Schefer et al., 2011) with the Jarando basin located in the hanging wall of the detachment fault. The Jarando basin is characterized by the presence of bituminous coals, whereas in the other intramontane basins in Serbia coalification did not exceed the subbituminous stage within the same stratigraphic level. Furthermore, the basin hosts boron mineralizations (borates and howlite) and a magnesite deposit, which again implies elevated temperatures. This thermal overprint is possibly due to post-magmatic activity related to the emplacement of Oligocene I-type Kopaonik and Miocene S-type Polumir granitoid (Schefer et al., 2011.). This research project is aimed at providing new information about the thermal history of the Jarando basin. Fifteen core samples from three boreholes and 10 samples from the surrounding outcrops were processed for apatite fission-track analysis. Additionally, vitrinite reflectance was measured for 11 core samples of shales from one borehole and 5 samples of coal from an underground mine. VR data of Early to Middle Miocene sediments reveal a strong post-depositional overprint. Values increase with the depth from 0.66-0.79% to 0.83-0.90%. Thus organic matter reached the bituminous stage and experienced temperatures of around 110-120?C (Barker and Pawlewicz, 1994). FT single grain ages for apatite scatter between 45 Ma to 10 Ma with a general trend towards younger ages with depth. Both, the spread in single grain ages together with the bimodal track lengths distribution clearly point to partial annealing of the detrital apatites. With the temperature given from the VR values the partial annealing points to a rather short-lived thermal event. This is assisted by thermal modelling of our fission track data indicating that maximum temperatures of <120°C around 15-12 Ma. We correlate the thermal event with the extension and core-complex formation followed by the syn-extensional intrusion of the Polumir granite. Later cooling from 10 Ma onwards is related to basin inversion and erosion.

Andri?, Nevena; Životi?, Dragana; Fügenschuh, Bernhard; Cvetkovi?, Vladica

2013-04-01

401

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

402

The record of Miocene climatic events in AND-2A drill core (Antarctica): Insights from provenance analyses of basement clasts  

NASA Astrophysics Data System (ADS)

This paper includes the results of a detailed quantitative provenance investigation on gravel-size clasts occurring within the late Early to Late Miocene sedimentary glacimarine section recovered for the first time by the AND-2A core in the SW sector of the Ross Sea (southern McMurdo Sound, Antarctica). This period of time is of crucial interest, as it includes two of the major Cenozoic events in the global climatic evolution: the mid-Miocene climatic optimum and the middle Miocene climate transition. Petrographical and mineral chemistry data on basement clasts allow to individuate two different diagnostic clast assemblages, which clearly suggest two specific sectors of southern Victoria Land as the most likely sources: the Mulock-Skelton glacier and the Koettlitz-Blue glacier regions. Distribution patterns reveal high fluctuations of the detritus source areas throughout the investigated core interval, variations which can be interpreted as the direct result of an evolving McMurdo Sound paleogeography during the late Early to Late Miocene. Consistently with sedimentological studies, gravel-fraction clast distribution patterns clearly testify that the Antarctic ice sheet experienced a dramatic contraction at ca. 17.35 ± 0.14 Ma (likely correlated to the onset of the climatic optimum), and in a < ca. 100 ka time window passing from a glacial scenario comparable to the last glacial maximum (Phase 1) to a very dynamic glacial environment (Phase 2). Phase 2 conditions persisted through the early Middle Miocene (to ca. 14.2 Ma), when a major expansion of the Antarctic ice sheet is hypothesized, likely contemporaneously to the onset of the middle Miocene climate transition. Therefore, provenance and distribution studies of gravel-fraction clasts show that the variations of paleoenvironmental drivers characterising this period were able to exert deep transformation of the Antarctic ice sheet and reveal the methodology to be a powerful tool for the reconstruction of paleo-glacial-flow direction and paleogeographic scenarios.

Sandroni, Sonia; Talarico, Franco M.

2011-01-01

403

Dietary reconstruction of Miocene Gomphotherium (Mammalia, Proboscidea) from the Great Plains region, USA, based on the carbon isotope composition of tusk and molar enamel  

Microsoft Academic Search

The Miocene of the Great Plains of North America has long been recognized as an interval of major ecological reorganization. To reconstruct the dietary response of the proboscidean Gomphotherium to Miocene ecosystem change in the Great Plains, we analyzed the carbon isotope composition of 185 serial samples of tusk enamel from 17 individuals and bulk samples of posterior molars from

David L. Fox; Daniel C. Fisher

2004-01-01

404

Middle Miocene Paleoceanography in the Southern High-Latitudes Off Tasmania: Stable Isotope Records from ODP Sites 1170 and 1172  

NASA Astrophysics Data System (ADS)

The middle Miocene encompasses one of the major steps in a global cooling trend towards the permanent establishment of east Antarctica ice sheet (EAIS), as inferred from the worldwide ca. 1\\permil increase in benthic foraminiferal ?18O. It has been suggested that an intensified Antarctic Circumpolar Current (ACC) prompted the mid-Miocene cooling, thereby increasing the meridional thermal gradient in the southern high-latitudes, and, ultimately, accumulation of the EAIS. At the same time, the southwest Pacific sector is thought to have ameliorated regionally through the incursion of a warm western boundary current, i.e., the proto-East Australian Current (EAC). In order to test the potentially contrasting effects of the EAC and ACC on evolution of the meridional thermal gradient in the southern high-latitudes across the middle Miocene climate transition, we have reconstructed near-surface paleohydrography by measuring ?18O and ?13C of planktic foraminifer Globigerina bulloides and Orbulina universa and bulk fine-fraction carbonates from ODP Sites 1170 (South Tasman Rise; Indian Ocean sector) and 1172 (East Tasman Plateau; Pacific sector) off Tasmania for the interval 8-20 Ma. Our results show no significant differences in the ?18O values between Sites 1170 and 1172. This suggests that the both sites were influenced by the same water mass in the middle Miocene. Long-term trends in the fine-fraction ?18O from the both sites indicate a signal of the early middle Miocene "climatic optimum" (MMCO) and the subsequent EAIS positive ?18O shift, and are similar to those reported from other lower latitude sites. In contrast, the planktic foraminiferal ?18O records from Sites 1170 and 1172 do not exhibit significant long-term trends, with values ranging from ca. 0.6 to 1.6\\permil. This implies that near-surface seawater temperatures at Sites 1170 and 1172 increased across the middle Miocene EAIS event (after ca. 14.5 Ma), as assuming that the mid-Miocene increase in the benthic foraminiferal ?18O reflects the global 18O budget due to accumulation of continental ice. We suggest that Sites 1170 and 1172 were in the north of ACC, and these sites were warmed by intensified EAC during the mid-Miocene EAIS event.

Ennyu, A.; Arthur, M. A.

2002-12-01

405

Relationships of seismic amplitudes and gas content of the Miocene Amos Sand, Mobile Bay area, offshore Alabama  

SciTech Connect

Mobil Oil Company has collected three-dimensional (3-D) seismic data over Mary Ann field in the Mobile Bay area, Alabama. Although the survey was designed and collected so as to image the deeper Norphlet Sands, amplitude anomalies in the image of the shallow Miocene Amos Sand are evident. Relationships are developed between the seismic amplitudes and net feet of gas in the Amos Sand at the few existing wells. These relationships are used to predict net feet of gas everywhere in the area of the seismic survey. The result is a contoured map of net feet of gas in the Miocene Amos Sand in Mary Ann field.

Reif, L.T. (Mobil Oil Company, New Orleans, LA (United States)); Kinsland, G.L. (Univ. of Southwestern Louisiana, Lafayette, LA (United States))

1993-09-01

406

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

407

CO2 drawdown following the middle Miocene expansion of the Antarctic Ice Sheet  

NASA Astrophysics Data System (ADS)

The development of a permanent, stable ice sheet in East Antarctica happened during the middle Miocene, about 14 million years (Myr) ago. The middle Miocene therefore represents one of the distinct phases of rapid change in the transition from the "greenhouse" of the early Eocene to the "icehouse" of the present day. Carbonate carbon isotope records of the period immediately following the main stage of ice sheet development reveal a major perturbation in the carbon system, represented by the positive ?13C excursion known as carbon maximum 6 ("CM6"), which has traditionally been interpreted as reflecting increased burial of organic matter and atmospheric pCO2 drawdown. More recently, it has been suggested that the ?13C excursion records a negative feedback resulting from the reduction of silicate weathering and an increase in atmospheric pCO2. Here we present high-resolution multi-proxy (alkenone carbon and foraminiferal boron isotope) records of atmospheric carbon dioxide and sea surface temperature across CM6. Similar to previously published records spanning this interval, our records document a world of generally low (~300 ppm) atmospheric pCO2 at a time generally accepted to be much warmer than today. Crucially, they also reveal a pCO2 decrease with associated cooling, which demonstrates that the carbon burial hypothesis for CM6 is feasible and could have acted as a positive feedback on global cooling.

Badger, Marcus P. S.; Lear, Caroline H.; Pancost, Richard D.; Foster, Gavin L.; Bailey, Trevor R.; Leng, Melanie J.; Abels, Hemmo A.

2013-01-01

408

A geochemical study of macerals from a Miocene lignite and an Eocene bituminous coal, Indonesia  

USGS Publications Warehouse

Optical and chemical studies of maceral concentrates from a Miocene lignite and an Eocene high-volatile bituminous C coal from southeastern Kalimantan, Indonesia were undertaken using pyro-Lysis, optical, electron microprobe and FTIR techniques Pyrolysis products of vitrinite from bituminous coal were dominated by straight-chain aliphatics and phenols. The huminite of the Miocene lignite produced mostly phenolic compounds upon pyrolysis. Differences in the pyrolysis products between the huminite and vitrinite samples reflect both maturation related and paleobotanical differences. An undefined aliphatic source and/or bacterial biomass were the likely contributors of n-alkyl moieties to the vitrinite. The resinite fraction in the lignite yielded dammar-derived pyrolysis products, as well as aliphatics and phenols as the products of admixed huminite and other liptinites. The optically defined resinite-rich fraction of the bituminous coal from Kalimantan produced abundant n-aliphatic moieties upon pyrolysis, but only two major resin markers (cadalene and 1,6-dimethylnaphthalene). This phenomenon is likely due to the fact that Eocene resins were not dammar-related. Data from the electron microprobe and Fourier transform infrared spectrometry strongly support the results obtained by Py GC MS and microscopy.

Stankiewicz, B. A.; Kruge, M. A.; Mastalerz, M.

1996-01-01

409

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