Development of Productivity Models for the Northern Gulf of Mexico Based on Oxygen Concentrations and Stable Isotopes

Oxygen concentrations have been used for decades to estimate primary production (P) and respiration (R) in aquatic ecosystems. Yet, this approach cannot separate the effects of biological and physical processes affecting oxygen dynamics; therefore, it is now often complemented with the analysis of stable oxygen isotopes. Existing algorithms for calculating primary production and P/R have been developed for closed systems and steady-state open systems. None of these formulations are applicable to productive aquatic ecosystems where diurnal changes in oxygen concentrations and isotope values are usually large. Here, we describe a novel P/R model that includes algorithms for air–sea gas exchange and is not constrained by steady-state conditions. Our objective was to test model sensitivity to variations in input parameters for values commonly observed in coastal waters of the northern Gulf of Mexico. The model was highly sensitive to variations in fractionation factor for respiration (ε) but less sensitive to variations in wind speed, oxygen isotope values of source-water, or oxygen flux through the picnocline. This model is easily transferable to other coastal ecosystems, with a caveat that system-specific values for ε are needed to obtain realistic estimates of P/R.     

A hidden suture within the northern Paleotethyan margin: Paleogeographic/paleo-tectonic constraints on the late Paleozoic 'Veles Series' (Vardar Zone,North Macedonia)

There is little consensus in characterizing the effects of the migrated late Pan-African/Lower Paleozoic configuration (western Paleotethys and precursory Paleozoic oceans) and its Variscan, late Variscan, and Eo-Cimmerian involvement. Constrained by a limited choice of the geological, biostratigraphical, and paleogeographical constraints, the focus of this regional geological synthesis is the little-known Devonian – Lower Carboniferous polymetamorphic 'Veles Series' (southern Vardar-Axios Zone, Northeast Mediterranean). Kinematic reconstructions indicate that the drifted carbonate platform assemblage of the 'Veles Series' including its Lower Carboniferous collision occurred along an active margin of southwestern Moesia, Laurussian foreland. Despite the fact that the dominant, low-grade metamorphic imprint across the 'Veles Series' is compatible with the ‘soft’ Eo-Cimmerian docking (i.e. Triassic), the documented Lower Carboniferous age suggests a Variscan involvement.A distinctive Late Paleozoic age is consistent with the north Gondwana and Variscan developments, reflected by the peculiar protoliths pallet portraying the presence of the oceanic crust to deep-marine equivalents. Accommodated to the west (paleo-south) of the late Cadomian Serbo-Macedonian Unit (a segment of the former peri-Gondwanan terrane assembly) and to the north of the Cimmerian Minoan system (East Mediterranean), the 'Veles Series' reflects a migrated rift to carbonate platform system. Despite the significant Alpine overprinting, based on this regional geological synthesis we propose that the 'Veles Series' is a 60 km-long suture segment documenting a so far rather poorly explored Variscan segment of the Paleotethyan lithosphere exposed within Balkans/Northeast Mediterranean.     

Urban-suburban/rural vapour pressure and relative humidity differences at fixed hours over the area of Belgrade city

Summary  In the study, urban-suburban/rural vapour pressure and relative humidity differences at fixed hours in the Belgrade area were analysed and compared. The data from one urban, two suburban and one rural stations (0700, 1400 and 2100 hours LTC), for the period 1976–1980 were used. It has been found, on the basis of the vapour pressure differences that the atmosphere in urban areas is more humid than that in the suburban and rural areas at 0700 and 2100 hours, in the period from September to February, while from February to September the urban atmosphere is drier. At 1400 hours, urban atmosphere is drier throughout the year. However, relative humidity differences indicate that urban air is less humid than the air in suburban and rural areas throughout the year. Relationships between urban-suburban/rural vapour pressure differences and heat island intensity revealed that the local effects could be significant. Received December 23, 1999 Revised September 27, 2000     

Metallogenic provinces and epochs in southern Central America

The southern part of Central America is characterized by common geological features. The ophiolitic belt running alongside the Pacific is related to the late Mesozoic eugeosynclinal trough. No significant mineralization is known in this rock complex. Copper ore occurrences in the Azuero peninsula are associated with the late Cretaceous diorite pluton. During Tertiary time, radial tectonic deformation and basaltandesite-dacite volcanism took place. Gold-silver quartz veins and Cu-, Pb-, Zn- (Ag)-sulfidic ore formation associated with this magmatic and tectonic activity form the largest metallogenic provinces. Porphyry copper mineralization in northern Panama is confined to the late Tertiary intermediate hypabyssal intrusives. Laterite, and gold placers are the only exogenic deposits. The relative abundance of copper ores in southern Central America indicates a geochemical specialization of magma in copper and the possible continuation of the circum-Pacific copper belt across Central America.

---

Zusammenfassung Der südliche Teil von Zentralamerika zeichnet sich durch regionale Merkmale der geologischen Beschaffenheit aus: Die ophiolitische Zone längs der Pazifikküste ist mit der spät-mesozoischen Eugeosynklinale verbunden. Keine bedeutende Mineralisation ist in diesem Komplex bekannt. Die Kupfererzvorkommen auf der Azuero-Halbinsel sind mit spät-kretazischen Dioritintrusionen verbunden. Während des Tertiärs entstanden radialtektonische Störungen und Basalt-Andesit-Dazit Vulkanismus. Die Gold-Silber Quarzgänge und die sulfidische Cu-Pb-Zn-(Ag-) Erzformation, die mit dieser magmatischen und tektonischen Aktivität verbunden ist, bildet die grössten metallogenetischen Provinzen. Die porphyrische Kupfermineralisation in Nord-Panama ist mit den spät-tertiären intermediären hypoabyssischen Intrusionen assoziiert. Laterit und Seifen sind die einzigen exogenen Lagerstätten. Die relative Häufigkeit der Kupferlagerstätten im südlichen Teil Zentralamerikas weisen auf eine mögliche geochemische Spezialisation der Magmen in Kupfer und Fortsetzung der zirkumpazifischen Kupferzone quer durch Zentralamerika hin.

     

Xonotlit und Pektolith aus basischen Gesteinen des Peridotitgabbrokomplexes im Zlatibor-Gebirge,Jugoslawien

Zusammenfassung Im westlichen Randgebiet des Zlatibor-Gebirges, im Tal des Flusses Lim, wurden in der Nähe des Ortes Bistrica in der Randzone einer kleineren Pyroxenitmasse gegen angrenzenden serpentinisierten Peridotit dünnere, milchweiße Adern gefunden. Sie bestehen aus Xonotlit und Pektolith. Der Xonotlit ist nach seinem äußeren Aussehen Chalcedon-ähnlich; von ihm werden die zentralen Teile der Äderchen eingenommen. Der Pektolith ist weiß und faserig; aus ihm bestehen die Ränder der Adern. Die Resultate der ausführlichen optischen, quantitativ chemischen, thermischen und röntgenographischen Untersuchungen sowie der Untersuchungen im infraroten Spektralgebiet stimmen mit bisher bestehenden Angaben für beide Minerale überein.Die Genesis dieser Minerale läßt sich auf die Umwandlung der basischen, primäre Calciumminerale enthaltenden Gesteine zurückzuführen. Es entstehen dabei in diesen Gesteinen aus Calciummineralen verschiedene sekundäre Minerale. Der Überschuß des Calciums und Siliciums wird unter den meso- bis katathermalen Umständen in der Form einfacher Adernparagenesen ausgeschieden.

---

Xonotlite and pectolite from basic rocks of the peridotite-gabbro-complex in the Zlatibor-mountains, Yugoslavia

Summary In the Lim valley, at the western slope of Mount Zlatibor, near the village of Bistrica there is a minor pyroxenite mass surrounded by serpentinized peridotite. The border zone of pyroxenite contains milk-white viens composed of the rare minerals xonotlite and pectolite. Xonotlite is in its outer appearance similar to chalcedony and occupies the central parts of the veins. Pectolite is white and fibrous, and is confined to the outer parts of the veins.The results of detailed optical, quantitative chemical, thermal and x-ray examinations, and of infrared spectral analyses agree with the hitherto known data on both minerals.The origin of these minerals may be explained by alteration of basic rocks containing primary calcium minerals. Different secondary minerals can be formed from calcium minerals by such processes. The excess calcium and silica precipitate in the form of simple vein associations under the mesoto katathermal conditions.

---

---

Mit 2 Abbildungen     

Die Erforschung der Altwasser und Überschwemmungsgebiete der Donau

Ohne Zusammenfassung