A Rb-Sr whole rock isochron date on an igneous rock-body from the Stavanger area,South Norway

The Ormakam-Moldhesten granite, from the Stavanger area, South Norway, has been dated by the Rb-Sr whole rock method. The isochron ages obtained (1180 m.y., 1243 ±160m.y. and 1534±125 m.y.) show that the granite complex is of Precambrian age. The 1543 m. year age is thought to refer to a period of early granulite facies metamorphism, the 1180 m.y. isochron age is taken as the crystallisation age of a later intrusion of biotite granite. This is within the limits of error of the 1160 m.y. metamorphic event shown earlier to have affected the paragneisses in the area. The results demonstrate clearly the allochthonous position of the gneisses and granitic intrusives overlying the fossiliferous Cambrian beds in the Stavanger area. The tectonostratigraphic succession in this area is thus consistent with the observation of Precambrian nappes to the north (Hardangervidda-Ryfylke area).     

Glacial conglomerates of late precambrian age from the Bunyoro Series,W. Uganda

The Bunyoro Series of W. Uganda is a sequence of sandstones and pelitic sediments of fairly low metamorphic grade resting unconformably on crystalline Precambrian basement rocks. Conglomerates and pebbly mudstones are found predominantly in the lower part of the sequence. The present paper describes the result of fieldwork carried out by the author, mainly in the Hoima and Masindi areas. The author supports the conclusion reached by earlier workers (Davies, 1939) that the conglomerates of the Bunyoro Series are of glacial origin and probably of Late Precambrian age. The conglomerates of the northern part of the Bunyoro District (Masindi) are strongly deformed and elongated, defining a very distinct pebble lineation dipping in a northerly direction. This lineation was most probably formed during isoclinal folding with tectonic movement from the North to the South, producing extensive inversions. This folding is most likely to have taken place in Late Precambrian or Early Palaeozoic times and may tentatively be correlated with the Katanga orogeny.

---

Zusammenfassung Die Bunyoro-Serie in West-Uganda besteht aus wenig metamorphen Sandsteinen und pelitischen Sedimenten, die diskordant auf dem kristallinen präkambrischen Grundgebirge ruhen. Konglomerate und geröllhaltige Ton- und Siltsteine dominieren in den tieferen Teilen der Serie. In dieser Abhandlung beschreibt der Verfasser die Resultate seiner Feldarbeit hauptsächlich aus den Gebieten Hoima und Masindi. Frühere Ergebnisse (Davies, 1939) werden gestützt insofern, als die Konglomerate der Bunyoro-Serie glazialen Ursprungs sind und wahrscheinlich spät-präkambrisches Alter haben. Die Konglomerate der nördlichen Teile des Bunyoro-Gebietes sind stark deformiert, und die Geröllachsen fallen in nördlichen Richtungen ein, Diese Liniation ist wahrscheinlich während einer isoklinalen Faltungsperiode mit tektonischer Bewegung von Norden gegen Süden entstanden. Die Faltung hat extensive Überkippungen hervorgerufen und hat wahrscheinlich in spätpräkambrischen oder frühen paläozoischen Zeiten stattgefunden. Sie kann versuchsweise mit der Katanga-Orogenese korreliert werden.

---

Résumé La Série du Bunyoro de l'Ouest de l'Ouganda consiste en grès et sédiments pélitiques peu métamorphiques reposant en discordance sur le socle cristallin Antécambrien (Précambrien). Des conglomérats et argiles à galets sont surtout localisés dans la partie inférieure de la série. Le présent article décrit les résultats du travail de terrain effectué par l'auteur, principalement dans les districts de Hoima et de Masindi. L'auteur confirme la conclusion à laquelle sont arrivés ses prédécesseurs (Davies, 1939), c.-à-d. que les conglomérats de la Série du Bunyoro ont une origine glaciaire effectué par l'auteur, principalement dans les districts de Hoima et de Masindi. conglomérats de la partie Nord du District du Bunyoro (Masindi) sont fortement déformés et étirés avec une linéation de galets très marquée, plongeant vers le Nord. Cette linéation s'est probablement développée lors d'un plissement isoclinal avec transport tectonique du Nord vers le Sud, ce qui a produit d'importantes inversions. Apparemment cette phase de plissement s'est produite vers la fin de la période infracambrienne ou bien au début de l'ère Paléozoïque, et l'on peut tenter de la mettre en liaison avec l'orogènese du Katanga.

---

Bunyoro , . . , . , . (Dayles, 1939) , Bunyoro , , . Bunyoro , . , , . , , , . .

     

The short term response to eutrophication abatement

We compare results of a new model for predicting the short term inter annual changes in chlorophyll-a (chl-a) in lakes after reductions in total phosphorus (TP) to predictions made by least squares regression models. In the new method, slopes of chl-a/TP graphs (both axes in mg · m^–3) are depicted in frequency diagrams and used to extract information on the expected, short term chl-a/TP response. The short term response for nine shallow (< 10 m deep) and nutrient rich lakes to changes in TP was found to be: Chl-a = 0.49 · TP + 17.3, and for nine deep, P-limited lakes: Chl-a = 0.08 · TP + 3.5. If the TP-reduction is known to be greater than 10 mg · m^–3, the expected slope increases to 0.58 for shallow lakes and to 0.26 for deep lakes. The slope, 0.58, is 8% lower than the slope for the long term response calculated by regression for the shallow lakes. For deep lakes the slope, 0.26, is 2 to 3 times higher than that calculated by regression, indicating that reductions in TP for deep lakes give greater effects than least squares regression equations suggest. We have also calculated the reduction in TP which will give about 80% probability that a reduction in chl-a will be observed next year. For shallow, P-limited lakes this reduction is about 30 mg · m^–3 (5% of average initial in-lake TP concentration), and for deep lakes about 14 mg · m^–3 (35% of average initial in-lake TP concentration).     

Sediment sequences and paleosols in the Kyichu Valley, southern Tibet (China), indicating Late Quaternary environmental changes

Abstract The Tibetan Plateau is highly sensitive to environmental changes and affects the settings of a far larger territory in Central Asia and beyond. Thus, knowledge on past environmental changes in that area is essential. Even though the Kyichu (Lhasa River) Valley and its tributaries is an easily accessible area, the Late Quaternary landscape evolution of southern Tibet is in general scarcely known. Therefore, 12 sedimentary sections in the middle and lower catchment were subjected to multidisciplinary analyses (sedimentology, paleopedology, AMS ¹⁴C and luminescence dating, and charcoal determination) aiming at results on regional paleoenvironmental changes. At the altitude studied (3600–4000 m above sealevel), no glacial relics could be detected, indicating that the valley positions have been unglaciated since the Last Interglacial. The lack of fluvial–lacustrine structures above the floodplain is due to the aggradational character of this tectonically (sub‐)active valley, which caused an alluvial burying of older valley bottoms. During the Late Pleistocene the mouth area of the Kyichu was occupied by a lake which was part of a larger dam‐lake in the superordinate Yarlung Zhangbo Valley. On the valley flanks, loesses were predominantly deposited before the Last Glacial Maximum (LGM), whereas eolian sands were predominantly deposited around and after the LGM. Paleosols of Last Interglacial, Last Glacial and Holocene ages regularly occur at terrestrial sites representing temperate to cool and humid to semiarid conditions during soil formation. Ages of colluvial sediments indicate that the widespread barren valley slopes were primarily formed by Late Pleistocene erosion followed by a secondary Holocene erosion phase. Charcoal spectra indicate a Late Holocene change from a forest environment to a pastoral environment with sparse grasses, herbs and dwarf shrubs. It is assumed that the Late Holocene environmental changes, such as loss of forests/woodlands and erosion, have at least been reinforced by humans, enhancing a regional climatic aridification and cooling trend.     

Monitoring the freely dissolved concentrations of polycyclic aromatic hydrocarbons (PAH) and alkylphenols (AP) around a Norwegian oil platform by holistic passive sampling

In order to assess the environmental impact of aquatic discharges from the offshore oil industry, polar organic chemical integrative samplers (POCIS) and semipermeable membrane devices (SPMDs) were deployed around an oil platform and at reference locations in the North Sea. Exposure to polycyclic aromatic hydrocarbons (PAH) and alkylated phenols (AP) was determined from passive sampler accumulations using an empirical uptake model, the dissipation of performance reference compounds and adjusted laboratory derived sampling rates. Exposure was relatively similar within 1–2 km of the discharge point, with levels dominated by short chained C1–C3 AP isomers (19–51 ng L⁻¹) and alkylated naphthalenes, phenanthrenes and dibenzothiophenes (NPD, 29–45 ng L⁻¹). Exposure stations showed significant differences to reference sites for NPD, but not always for more hydrophobic PAH. These concentrations are several orders of magnitude lower than those reported to give both acute and sub-lethal effects, although their long term consequences are unknown.     

Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system

We reevaluate the systematics and geologic setting of terrestrial, lunar, Martian, and asteroidal “impactites” resulting from single or multiple impacts. For impactites derived from silicate rocks and sediments, we propose a unified and updated system of progressive shock metamorphism. “Shock-metamorphosed rocks” occur as lithic clasts or melt particles in proximal impactites at impact craters, and rarely in distal impactites. They represent a wide range of metamorphism, typically ranging from unshocked to shock melted. As the degree of shock metamorphism, at a given shock pressure, depends primarily on the mineralogical composition and the porosity of a rock or sediment sample, different shock classification systems are required for different types of planetary rocks and sediments. We define shock classification systems for eight rock and sediment classes which are assigned to three major groups of rocks and sediments (1) crystalline rocks with classes F, M, A, and U; (2) chondritic rocks (class C); and (3) sedimentary rocks and sediments with classes SR, SE, and RE. The abbreviations stand for felsic (F), mafic (M), anorthositic (A), ultramafic (U), sedimentary rocks (SR), unconsolidated sediments (SE), and regoliths (RE). In each class, the progressive stages of shock metamorphism are denominated S1 to Sx. These progressive shock stages are introduced as: S1–S7 for F , S1–S7 for M, S1–S6 for A , S1–S7 for U , S1–S7 for C , S1–S7 for SR , S1–S5 for SE , and S1–S6 for RE . S1 stands for “unshocked” and Sx (variable between S5 and S7) stands for “whole rock melting.” We propose a sequence of symbols characterizing the degree of shock metamorphism of a sample, i.e., F-S1 to F-S7 with the option to add the tabulated pressure ranges (in GPa) in parentheses.     

Addendum to “Stöffler,D., Hamann,C., and Metzler,K., Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system. Meteoritics & Planetary Science 53, 5–49, 2018”

With this addendum we provide some correction and additional information regarding the above cited publication. It addresses the following two topics. (1) Clarification for a correct application of the criteria for certain shock stages of chondrites, in particular stage C‐S6. (2) Correction of a printing error in the table that contains the shock classification system of chondrites.     

The Meteoritical Bulletin,No. 105

Meteoritical Bulletin 105 contains 2666 meteorites including 12 falls (Aouinet Legraa, Banma, Buritizal, Ejby, Kamargaon, Moshampa, Mount Blanco, Murrili, Osceola, Sariçiçek, Sidi Ali Ou Azza, Stubenberg), with 2244 ordinary chondrites, 142 HED achondrites, 116 carbonaceous chondrites, 37 Lunar meteorites, 20 enstatite chondrites, 20 iron meteorites, 20 ureilites, 19 Martian meteorites, 12 Rumuruti chondrites, 10 primitive achondrites, 9 mesosiderites, 5 angrites, 4 pallasites, 4 ungrouped achondrites, 2 ungrouped chondrites, 1 enstatite achondrite, and 1 relict meteorite, and with 1545 from Antarctica, 686 from Africa, 245 from Asia, 147 from South America, 22 from North America, 14 from Europe, 5 from Oceania, 1 from unknown origin. Note: 5 meteorites from Russia were counted as European. It also includes a list of approved new Dense Collection Areas and a nomenclature of the Aletai (IIIE‐an) iron meteorites from Xinjiang, China.