Geology of the Miami Terrace and its paleo-oceanographic implications     

Henry T. Mullins  A.Conrad Neumann 《Marine Geology》1979,30(3-4):205-232

The Miami Terrace is a drowned early to middle Tertiary carbonate platform, the outer margin of which has been deeply incised by submarine erosion subsequent to deposition of the limestone terrace. This interpretation is based on the study of high-resolution seismic reflection profiles, rock dredge samples, observations from deep-diving submersibles, and correlation with drill-hole data. The karstic upper terrace (200–375 m) yields limestones and dolostones of early middle Miocene age that have shallow-shelf affinities. Truncated beds of an eastward-dipping deeper-water slope facies are exposed on the upper surface of the erosional lower terrace at 600–700 m. The upper and lower terraces are separated by a discontinuous ridge, probably a drowned Miocene, or post-Miocene bank margin complex. Both terraces and the ridge are capped by dense conglomeratic phosphorites and phosphatic limestones. Phosphorite nodules are more common on the lower terrace whereas the upper terrace yields large phosphorite slabs as well as shark's teeth and bones of marine mammals.

Petrographic study of dredged and submersible-sampled rocks shows that two or more episodes of phosphatization took place intermittent with erosion, grain rounding, reworking and redeposition. Early stages of phosphatization appear to be selective, replacing the more unstable carbonate minerals first, while later stages are nonselective. The origin of most of the phosphorites is the diagenetic replacement of calcium carbonate by francolite.

The karst surface of the upper terrace appears to have been produced by subaerial exposure in the middle to late Miocene as evidenced by shallow-water components in the rocks of the upper terrace plus considerations of local subsidence and eustatic sea-level curves. The erosional lower terrace, 200–300 m deeper than the upper terrace, would have been too deep to have been produced by subaerial or wave erosion. An erosional hiatus of middle Miocene age in JOIDES drill holes on the Blake Plateau indicates that bottom-current velocities in this area increased over this interval. The formation of the lower erosional terrace is related to increased flow of the Gulf Stream system (Florida Current) and bioerosion concurrent with the tectonic uplift and oceanographic closure of the western Caribbean in mid-Miocene time.

The bathymetry, petrology, structure and paleontology of the Miami Terrace, along with correlative data from adjacent areas, argue that a more active Gulf Stream system began as early as the middle Miocene (10.5–16 m.y.B.P.) rather than the early to middle Pliocene (3.5–4.0 m.y.B.P.) as previously suggested.  相似文献   

Possible Mesozoic age of Ellenville Zn-Pb-Cu(Ag) deposit,Shawangunk Mountains,New York     

J. D. Friedman  J. E. Conrad  E. H. McKee  F. E. Mutschler  R. E. Zartman 《Mineralium Deposita》1994,29(6):474-487

Ore textures, epithermal open-space filling of Permian structures of the Alleghanian orogeny, and largely postorogenic mineralization of the Ellenville, New York, composite Zn-Pb-Cu(Ag) vein system, provide permissive evidence for post-Permian mineralization. Isochron ages determined by ⁴⁰Ar/³⁹Ar laser-fusion techniques for K-bearing liquid inclusions in main-stage quartz from the Ellenville deposit additionally suggest a Mesozoic time of mineralization, associated with extensional formation of the Newark basin. The best ⁴⁰Ar/³⁹Ar total-fusion age range is 165 ± 30 to 193 ± 35 Ma. The Mesozoic ⁴⁰Ar/³⁹Ar age agrees with that of many other dated northern Appalachian Zn-Pb-Cu(Ag) deposits with near-matching lead isotope ratios, and adds new evidence of Jurassic tectonism and mineralization as an overprint to Late Paleozoic tectonism at least as far north as Ellenville (lat. 41°43N).  相似文献   

Potentielle Mineralbestände kalitrachybasaltisch-karbonatischer Syntektika und die Zukunft des Vesuvmagmas     

Prof. Dr. Conrad Burri 《International Journal of Earth Sciences》1968,57(3):744-765

Zusammenfassung Die Magmenentwicklung des Vesbischen Vulkans (Somma-Vesuv) ist nachRittmann durch eine zeitlich progressive Desilifizierung gekennzeichnet, welche ihre Ursache in der Assimilation von Karbonatgesteinen, vorwiegend Triasdolomiten, besitzt, gefolgt von einer Differentiation der so gebildeten Syntektika. Im Anschluß an diese Vorstellungen werden ganz allgemein die potentiellen Mineralbestände derartiger Schmelzen in verschiedenen heteromorphen Fazien untersucht. Dabei wird vom mittleren kalitrachybasaltischen Stammagma des Tyrrhenisgebietes ausgegangen und sowohl Kalk- wie Dolomitsyntexis in Betracht gezogen. Anschließend werden auf Grund der in benachbarten Gebieten (Mti. Volsini und Vulcano Laziale) herrschenden Verhältnisse sowie des Auftretens von niedrigst silifizierten Auswürflingen am Vesuv selbst (sog. Vesbite vonWashington), Mutmaßungen über die zukünftige Entwicklung des Vesuvmagmas geäußert.

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According toRittmann, the magmatic evolution of the Vesbian Volcano (Somma-Vesuvius) is characterized by progressive desilication due to the assimilation of carbonatic rocks, chiefly triassic dolomites, followed by differentiation of the sintectic melts so produced. In the present paper the potential normative mineral composition in various heteromorphic facies of melts arising from this conception is examined. Starting point for the calculations is a potassic trachybasaltic magma, corresponding to the average composition of the Tyrrhenian primary magma, and the incorporation of limestones as well as of dolomite is considered. Some speculative ideas concerning the future evolution of the Vesuvian magma, based on the nature of ejected blocks of low silification, the so-called Vesbites ofWashington, and on some peculiar features of the neighbouring volcanic regions of the Monti Volsini and of the Alban Hills, are also put forward.

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Résumé D'aprèsRittmann, l'évolution magmatique du Volcan (Somma-Vésuve) est caractérisée par une désilication progressive, ayant pour cause l'assimilation de roches carbonatiques, surtout de dolomies triassiques, et suivies par la différentiation des produits syntectiques ainsi formés. Par suite à ces idées, la compsition minéralogique potentielle de tels mélanges est calculée et examinée d'une manière générale et dans ses divers faciès hétéromorphiques. Comme point de départ des calculs, la composition moyenne du magma trachybasaltique primaire de la région tyrrhénienne est choisie, tout en tenant compte de l'incorporation de chaux comme de celle de dolomie. Enfin quelques idées spéculatives sur le développement futur du magma vésuvien sont énoncées, en se basant sur des renseignements fournis par les régions avoisinantes des Monts Vulsiniens et du Volcan Lazial, ainsi que sur la composition minéralogique et chimique de blocs projetés à silicification très basse, rejetés par le Vésuve-même (les soi-disants vésbites deWashington).

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Herrn Professor Dr. A.Rittmann zum 75. Geburtstag gewidmet  相似文献   

Selective extraction of organically bound gold in soils, lake sediments and stream sediments     

D.Conrad Gregoire 《Journal of Geochemical Exploration》1985,23(3):299-313

The extraction of organically bound gold from surficial materials is accomplished by using a solution of 5% sodium hypochlorite. A 10-g sample is digested at least twice with 50 mL of hypochlorite solution. The recovery of gold from the organic phase is nearly quantitative for lake sediments and stream sediments high in organic content. For stream sediments and soils low in organics, the recovery of gold is complicated by the sorption of released gold onto inorganic sample components. For these materials, recoveries as low as 70% of the organically bound gold are possible. For a stream sediment sample containing 53.4 ppb gold, the precision of the method is approximately 6% for a 10-g sample and 14% when a 5-g sample of stream sediment is used. The results obtained for all materials tested indicate that a substantial fraction of the gold found in sediments and soils exists as organically bound gold.  相似文献   

Les formations volcaniques récentes du Sud de l’Iran (Kouh-e-Shahsavaran): données pétrologiques préliminaires; implications structurales     

M. Girod  G. Conrad 《Bulletin of Volcanology》1975,39(4):495-511

Kouth-e-Shasavaran massif in South Iran (Baloutchistan) consists of Pliocene and Quaternary cale-alkaline lavas. Fourty one new chemical analysis have been carried out to identify the volcanic rock series. Andesites are more abundant than basic thigh alumina basalts) and acid lavas (dacites and rhyodacites). This volcanic area is probably connected with a subduction zone located on the North of Oman Gulf, between the arabic, indian and eurasian plates. In this respect, Makran range may be inerpreted as an emerged trench.  相似文献   

Determination of Ruthenium,Palladium and Iridium in 27 In ternational Reference Silicate and I Ron-Formation Rocks,Ores and Related Materials By Isotope Dilution Inductively-Coupled Plasma Mass Spectrometry*     

J.G. SEN GUPTA  D. Conrad GREGOIRE 《Geostandards and Geoanalytical Research》1989,13(2):197-204

Ruthenium, palladium and iridium have been determined in 27 international reference rocks, ores and related materials by inductively-coupled plasma mass spectrometry using isotope dilution and sample introduction by solution nebulization and electrothermal vaporization, after chemical separation by co-precipitation with tellurium. The accuracy of the procedure is discussed by comparison of the results obtained with synthetic solutions and standard samples.  相似文献   

Derived gravity field of the seismogenic upper crust of SE Germany and West Bohemia and its comparison with seismicity   总被引：2，自引：2，他引：0  

J. Švancara  J. Havíř  W. Conrad 《Studia Geophysica et Geodaetica》2008,52(4):567-588

The gravity field of the seismogenic upper crust was derived from the Bouguer gravity map by applying the Butterworth high-pass filter in the wave-number domain. The cutoff wavelength of the filter was 110 km, to pass the gravity signals of structures within the 18 km thick seismogenic layer. The derived residual gravity map reveals potential stress concentrating structures, which may cause seismicity provided they lie within the existing zones of weakness. Furthermore we derived a shaded relief map of the horizontal gravity gradient, which highlighted the tectonic lines accompanied by density contrast. The directional analysis of this map shows three dominant strike directions. The most prominent one is “the Hercynian” NW-SE strike direction represented by the Franconian Line, the Gera-Jáchymov Fault Zone and the Elbe Zone. The second dominant strike is the Rhenisch NNE-SSW trending represented by the Upper Rhine Graben Zone, Rheinsberg-Heldburg Line and several Proterozoic volcanic belts in the Teplá-Barrandien Unit. The third pronounced trending of the ENE-WSW direction is represented by the Erzgebirge and Eger Graben gravity low. The N-S trending Rostock-Leipzig-Regensburg Zone (Pritzwalk-Naab Lineament) is not distinctly reflected in the derived gravity maps, although many fault segments have a meridian direction. The relative reactivation potential of some pre-existing fault systems identified in the gravity map was studied with respect to the wide range of the recent stress configuration determined in the West Bohemia/Vogtland region. The resulting diagrams show that the steep NNW-SSE to N-S faults (represented by some segments of the Mariánské Lázně Fault Zone) are oriented favourably for reactivation. On the contrary, the orientation of the ENE-WSW faults limiting the Eger Graben (Litoměřice Fault, etc.) is unfavourable for reactivation for all dip values.  相似文献   

Spatial survey of trace metal contaminants in the sediments of the Elizabeth River, Virginia   总被引：5，自引：0，他引：5  

Conrad CF  Chisholm-Brause CJ 《Marine pollution bulletin》2004,49(4):319-324

The Elizabeth River is a sub-estuary of the James River, the most southern tributary of the Chesapeake Bay. It is a highly industrialized area, and has been designated a "toxic hot spot" due to the heavy loads of contaminant metals and organic compounds in its bed sediments. Fifty surface sediment samples were taken along the channels and shoals of the Mainstem and the Southern Branch portions of the river. The samples were analyzed for trace metals (Cd, Cr, Cu, Pb and Zn), Fe and particle properties (% sand, % silt, % clay and specific surface area) to discern the spatial distribution of contaminant metals in this system. Enrichment factors were calculated to assess the overall level of contamination relative to other surrounding waterways as well as historic contamination levels within the river itself. The highest levels of metals were found to be in close proximity to industrial sources of contamination. The overall level of contamination was 3-10 times higher than baseline levels within the river, and 2-3 times higher than contaminant levels in other area waters.  相似文献   

On thermal springs a contribution to the knowledge of their nature     

V. Conrad 《Meteorology and Atmospheric Physics》1956,9(3):371-405

Summary Temperature and discharge of fourteen thermal spring at Badgastein (Hohe Tauern, Austrian Alps) were observed throughout a year.Daily observations were made at four springs. With these an obviously rapid increase in temperature of 1 Cdeg occurred from May 11 to May, 12 1931. Generally, short variations are exceedingly small. Six other springs, observed once a week, showed an increase in temperature of an equal amount. Synchronism of the increase among all the ten springs could be made plausible. The dropping back of temperature on May 23 occurred unequivocally simultaneously with all the ten springs.The curve ofdischarge remained, however, fully undisturbed within the time of the temperature discountinuity.From the synchronism of the disturbance of temperature the conclusion was drawn thatall the ten springs may originate from one and the same source in the interior of the mountains.The main problem that should be cleared up in this study on temperature and discharge is the question how far the spring water is either juvenile or vadose (atmospheric) or mixed of both.An investigation into the variability of temperature and discharge was the first step. The daily observations of four springs offered a convenient material. The absolute variability (A. V.) (Table 5, last line) is extremely small, 0.045 Cdeg, on the average, for the four springs. As a supplement theinterdiurnal variability (I. V.) was calculated. On the average, this is still smaller than the regular average variability. It is 0.026 Cdeg. A comparison of the magnitude of R. V.^* and R. I. V.^* of discharge for December, January and July, August arrived partly at contradictory indications. The differences, however, between the two seasons are of an order of magnitude of only hundredth per cent so that the idea is at hand to think of an effect caused by chance.The further investigation leads to the conclusion that some of the springs are likely of juvenile nature and perhaps sometimes mixed withnon-essential amounts of atmospheric water.Rain water penetrating the clefts has either no influence on the temperature or it must have a cooling effect. The discharge must increase in any case if rain water is penetrating. The number of coolings from day to day must beincreased then in thewarm half-year and just so the number of cases withdischarge increasing from day to day. These effects are examined by means of two methods. In some cases the statistical indications were qualitatively again in favor of the assumption that rain water penetrates in small amounts. The magnitude of the differences is, however, not large enough, and the agreement of the behavior of the single springs not sufficient to exclude the role ofchance. Also this investigation arrived, at the result that one or the other indication speaks for the assumption that occasionally after copious rainfalls insignificant amounts of atmospheric water are mixed with the thermal water.Especially in consideration of the reslts of the first section that some of the springs carryessentially juvenile water one could think of anything but of variations of temperature and discharge in the length of a year.Figures 4a and 4b, however, show examples of such, at least fictive, annual variations. With the one spring, variations of temperature and discharge are parallel to one another; in the other spring the variations are opposite to one another; with a spring, the water of which is mixed of juvenile water with greater amounts of atmospheric water, the opposite type must be expected with minimum of temperature and maximum of discharge in summer. Only one of the fourteen springs (W) fulfils these conditions.The reality of the annual variations is dubious since with most important spring groups the ranges of both elements are very small. A method given by the present author permits estimating the reality of an annual variation so far as only practicallywhole-year sine-waves are considered.The main results is that four springs of the fourteen show areal annual variation of temperature and at the same time of discharge.Only a clue can be given to a possibly correct explanation. Themovement of the poles showstwo andonly two periodical components that cause certain stresses in the crust of the earth. With a probability not too small these stresses contribute to the release of earthquakes and could also influence the mechanism of the springs. The one component has a wave length of 12 months, the other one of 14 months. If it would be possible to discover the second 14-months-variation of temperature and discharge from a new material of a few years the enigma of the annual variation, otherwiseununderstandable, could be solved to a certain degree.In the last section some numerical characteristics of the springs appear. Statistics show that a real annual variation of temperature is found only in springs of a medium temperature and not in the warmest and coolest springs.All of the methods applied here, lead to the conclusion thatsome of the springs at Badgastein carry generally pure juvenile water possibly mixed some-times with negligible amounts of vadose water.

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Zusammenfassung Temperatur und Ergiebigkeit von 14 Thermalquellen in Badgastein (Hohe Tauern, Österreich. Alpen) wurden ein Jahr hindurch beobachtet. Bei vier Quellen erfolgten die Messungen täglich. Bei diesen wurde ein offenbar rascher Anstieg um zirka 1° C vom 11. bis 12. Mai beobachtet, während sonst die kurzen Schwankungen ausnehmend klein sind. Bei sechs weiteren Quellen, bei denen nur einmal in der Woche gemessenAls Hauptresultat wird festgestellt, daß vier Quellenreale Jahresschwankung von Temperatur sowohl als von Ergiebigkeit aufweisen. Zur Erklärung ist daran zu erinnern, daß dieBewegung der Erdpole zwei und nur zwei periodische Komponenten aufweist, die gewisse Spannungen in der Erdkruste erzeugen müssen. Diese tragen z. B. mit nicht unbedeutender Wahrscheinlichkeit zur Auslösung von Erdbeben bei und könnten so auch den Quellmechanismus beeinflussen. Die eine Komponente hat eine Wellenlänge von 12 Monaten, die andere eine von 14 Monaten. Wenn es gelänge, auch diese 14monatige Schwankung von Temperatur und Ergiebigkeit der Quellen in einem mehrjährigen Material festzustellen, wäre wohl das Rätsel der sonst unverständlichen Jahresschwankung gelöst.Im letzten Abschnitt erscheinen einige numerische Charakteristiken der Quellen. Unter anderem ist zu ersehen, daß weder die wärmsten noch die kühlsten Quellen dem besprochenen Jahresgang unterworfen sind, sondern nur solche, die einer mittleren Temperaturgruppe angehören.Alle hier angeführten Untersuchungsmethoden führen zu dem Schlusse, daß dasjuvenile Wasser einiger der Gasteiner Quellen nur mit unwesentlichen Teilen atmosphärischen Wassers vermischt sein kann.

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Résumé On a observé pendant une année la température et le débit de 14 sources thermales à Bad Gastein (Hohe Tauern, Alpes autrichiennes). Pour 4 sources on fit des mesures quotidiennes, pour 6 autres une fois par semaine et pour les 4 dernières une fois en 5 semaines. Une hausse remarquable de température de 1° s'est produite pour toutes les sources au milieu de mai, tandis que le débit restait inchangé. On en conclut que les sources ont une origine commune à l'intérieur de la montagne.Le problème principal est celui de savoir si les eaux de ces sources sont d'origine atmosphérique ou non. A cet effet on a examiné la variabilité de la température qui est en moyenne extrêmement faible, de l'ordre de 0,045°; la variation interdiurne est encore plus petite: 0,026°. En ce qui concerne le débit, la variabilité relative de quatre sources n'atteint pas 0,5%. On est amené à conclure que quelques-unes des sources ne reçoivent pas d'apport d'eau météorique. Si de l'eau de pluie pénètre dans le sous-sol, elle doit ou bien ne pas modifier la température des sources ou alors l'abaisser; elle doit parallèlement accroître le débit. L'étude statistique montre que tout au plus certaines fortes chutes de pluie peuvent se mêler partiellement à l'eau des cources.Ces résultats font douter d'une variation de température et de débit à période annuelle. Quatre sources présentent cependant une variation annuelle des deux grandeurs, faible il est vrai. Il est possible que l'explication puisse en être trouvée un jour dans le déplacement du pôle, capable de provoquer des tensions de la croûte terrestre et qui ne présente que deux périodes de 12 et de 14 mois. Il faut cependant remarquer que les sources les plus chaudes et les plus froides ne présentent pas cette variation annuelle. Les constatations faites pour les sources de Gastein pourraient aussi être valables pour d'autres sources soumises à des conditions géologiques semblables. wurde, trat gleich großer Anstieg ein. Gleichzeitigkeit desselben mit dem der vier täglich beobachteten Quellen konnte plausibel gemacht werden. Bei dem Zurückfallen der Temperatur am 23. Mai unterliegt die Gleichzeitigkeit bei allen 10 Quellen keinem Zweifel. Die Kurve der Ergiebigkeit der 10 Quellen verläuft merkwürdigerweise völlig ungestört. Aus dem Synchronismus der Störung wird geschlossen, daß alle zehn Quellen wahrscheinlich einen gemeinsamen Ursprung im Innern des Gebirges haben.Das Hauptproblem, zu dessen Klärung eine Untersuchung der Temperatur und Ergiebigkeit beitragen soll, liegt in der Frage, wieweit das Quellwasser atmosphärischen (vadosen) oder juvenilen Ursprungs ist. Zu diesem Zwecke wurde eine Untersuchung der Veränderlichkeit der beiden Elemente an Hand der täglichen Beobachtungen an vier Quellen durchgeführt. Die mittlere absolute Veränderlichkeit (Tabelle 5, letzte Zeile) ist ausnehmend klein und beträgt im Mittel der vier Quellen 0,045° C; die interdiurne Veränderlichkeit (I. V.) ist im Mittel noch kleiner als die mittlere Veränderlichkeit und beträgt 0,026°C.Für die Untersuchung derErgiebigkeit wurde dierelative Veränderlichkeit (R. V.) angewendet; sie erreicht im Mittel der vier Quellen nicht 1/2%, die R. I. V. nicht einmal 0,4%.Ein Vergleich der Größen von R. V. und R. I. V. für Dezember (Januar und Juli) August führt zu teilweisem Widerspruch. Die Unterschiede zwischen den beiden Jahreszeiten bewegen sich jedoch nur in hunderstel Prozent. so daß es naheliegt, an eine Zufallswirkung zu denken. Die weitere Untersuchung führt dann zu dem Schluß, daßeinige von den untersuchten Quellen keinen wesentlichen Zusatz von atmosphärischem Wasser erhalten.Wenn Regenwasser die Klüfte durchdringt, hat es entweder keinen Einfluß auf die Temperatur oder es müßte abkühlend wirken. Die Ergiebigkeit muß bei zugesetztem Regenwasser jedenfalls ansteigen. Wenn also Außenwasser eindringt muß die Zahl der Abkühlungen von Tag zu Tag im warmen Halbjahr steigen und ebenso die der zunehmenden Ergiebigkeit. Diese Effekte werden mittels zweier Methoden geprüft. Als Resultat ergab sich wieder, daß die Statistiken in manchen Fällenqualitativ für die Annahme von eindringendem Regenwasser sprechen, daß aber diequantitativen Unterschiede nicht groß genug sind, das Verhalten der einzelnen Quellen nicht einheitlich genug, um das Wirken des Zufalls auszuschließen. Auch diese Untersuchung kommt zum Schluß, daß wohl das eine oder andere Anzeichen dafür spricht, daß gelegentlich größerer Regenfälle kleine Mengen atmosphärischen Wassers dem Quellwasser beigemengt werden.Speziell mit Rücksicht auf die Feststellung, daß die Quellen wesentlich juveniles Wasser aus den Tiefen der Gebirgskette zutage führen, sollte man alles eher als Schwankungen mit Jahresperiode von Temperatur und Ergiebigkeit vermuten. Fig. 4 und 5 zeigen Beispiele solcher, mindestens fiktiver Jahresgänge und auch die extremen Möglichkeiten. Bei der einen Quelle variieren Temperatur und Ergiebigkeit gleichsinnig, bei einer zweiten spiegelbildlich. Bei einer reichlich mit atmosphärischem Wasser gemischten Quelle müßte spiegelbildliches Verhalten auftreten, mit Temperaturminimum und Ergiebigkeitsmaximum im Sommer. Nur eine einzige Quelle (W) erfüllt diese Bedingung. Was die Realität der sich ergebenden Jahresschwankung so fraglich macht, sind die bei den wichtigsten Quellgruppen auftretenden, sehr kleinen Schwankungsweiten. Eine vom Verfasser gegebene Methode erlaubt es, die Realität einer Jahresschwankung abzuschätzen, soweit man es mit einer praktisch ganzjährigen Sinuswelle zu tun hat.

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With 5 Figures  相似文献   

Tertiary and quaternary geodynamics of southern Lut (Iran) as deduced from palaeomagnetic, isotopic and structural data     

G. Conrad  R. Montigny  R. Thuizat  M. Westphal 《Tectonophysics》1981,75(3-4)

Palaeomagnetic measurements and K---Ar age determinations carried out on lavas from Dash-e-Lut in southeast Iran reveal an anticlockwise rotation of about 90° of the depression south of Lut between Paleocene and Miocene time. It is probably associated with the collision between India and Asia.  相似文献