Geology

The felsic lavas of the Bamenda Mountains, in the main part of the Cameroon Volcanic Line, are mainly represented by trachytes, with subordinated benmoreites and alkaline to peralkaline rhyolites. New K–Ar geochronological data define two main volcanic episodes, the first one between 18 and 22Ma, and the second one from 12.5 to 13.5Ma. Geochemical data indicate that these felsic rocks

The Austral-Magallanes is an oil-producing basin located in southern Argentina and Chile, containing a siliciclastic stratigraphic record ranging from the Late Jurassic to Late Cenozoic. This short paper finalize the two special volumes of the Latin American Journal of Sedimentology and Basin Analysis dedicated to the basin, and aim to provide a comprehensive synthesis based on the current knowledge about the chronology of deposition, stratigraphy, and tectonic events that shaped this basin. During the breakup of Gondwana in the Jurassic, an extensional phase was responsible for the beginning of accumulation of volcaniclastic material within grabens, which subsequently were covered by widespread Lower Cretaceous shallow and deep marine deposits that conforms the main hydrocarbon system. From Late Cretaceous onward, the subduction-related compressive regime associated to Andean uplift and fold and thrust belt migration was responsible for the onset of the foreland stage. During the L...

Amfilochia Bay (Eastern Amvrakikos Gulf, Western Greece), a complex marine area affected by tectonism, was investigated for seabed seepage manifestations and for possible inter-relationships between shallow gas accumulations and hypoxia. For this purpose, an integrated research methodology that combined geophysical, geochemical, and hydrographic surveys was applied. Marine geophysical and bathymetric surveys led to the discovery of a gas-induced pockmark group in the study area. Oceanographic surveying confirmed that the bay is hypoxic/anoxic below a depth of 15 m (dissolved oxygen from ~4 to 60 μM). Very weak CH4 seepage was detected in correspondence to the pockmark group that seemed to slightly enhance the hypoxic environment locally and close to the seabed, with no effect in shallower waters and the oxycline. Methane isotopic analysis showed variable carbon isotopic composition (from −41‰ to −86‰) which could be either related to differential CH4 oxidation or mixing between micr...

Wang, Y., Shih, C., Szwedo, J. & Ren, D. iFirst article. New fossil palaeontinids (Hemiptera, Cicadomorpha, Palaeontinidae) from the Middle Jurassic of Daohugou, China. Alcheringa, 1–12. ISSN 0311-5518.A new genus and species assigned to the extinct family Palaeontinidae, Synapocossus sciacchitanoae Wang, Shih & Ren, is described from the Middle Jurassic of Daohugou in Inner Mongolia, China. This new genus is established based on well-preserved fossil specimens with body and complete forewings and hind wings. It differs from other described genera by the following characters: small body size, RP and M1 coalescing for an interval on the forewings and M3 + 4 without bifurcation on the hind wings. The RP coalescence with M1 in Synapocossus Wang, Shih & Ren previously reported only in Turgaiella Becker-Migdisova & Wootton, seems to be associated with strengthening of the anterior wing margin. The intra-specific and individual variations of Synapocossus and numerous other insect fossils of northeastern China probably indicate long-lasting ecological stresses and a competitive environment in the Middle Jurassic to Early Cretaceous ecosystems.Synapocossus sciacchitanoae Wang, Shih&Ren;Palaeontinidae:, RPM1, M3+4, Synapocossus Wang, Shih&RenRPM1Turgaiella Becher-Migdisova&Wootton, Synapocossus

Considerably long periods of time are required to measure soil-water characteristic curves using conventional equipment such as pressure plate apparatus or a Tempe cell. A commercially available, small-scale medical centrifuge with a swinging type rotor assembly was used to measure the soil-water characteristic curves on statically compacted, fine-grained soil specimens. A specimen holder was specially designed to obtain multiple sets of water content versus suction data for measuring the soil-water characteristic curve at a single speed of rotation of the centrifuge. The soil-water characteristic curves were measured for three different types of fine-grained soils. The three soils used in the study were processed silt (liquid limit, wL = 24%; plasticity index, Ip = 0; and clay = 7%), Indian Head till (wL = 35.5%, Ip = 17%, and clay = 30%), and Regina clay (wL = 75.5%, Ip = 21%, and clay = 70%). The soil-water characteristic curves for the above soils were measured in 0.5, 1, and 2 ...

Deposits from the Minoan Santorini (Thera) eruption in the eastern Mediterranean region constitute the most important regional stratigraphic marker in the chronological perplexity of the 2nd millennium BCE. Extensive tsunami depos- its were discovered in Crete at the Minoan archaeological site of Palaikastro, containing reworked volcanic Santorini ash. Hence, airborne deposition of volcanic ash, probably during the 1st (Plinian) eruption phase, preceded the tsunami, which was apparently generated during the 3rd or 4th phase of the eruption, based on evidence from Thera. Average radiocarbon dates (uncalibrated) of animal bones in the Palaikastro tsunami deposits along the coast (3350 ± 25 BP) and at the inland archaeo- logical site (3352 ± 23 BP) are astoundingly similar to the average 14C date for the Minoan Santorini eruption at Akrotiri on Thera (3350 ± 10 BP). The wiggle-matched 14C date of the eruption in calendar years is 1627-1600 cal BCE. Late Minoan IA pottery is the younges...

An integrated study involving sedimentology, mineral chemistry and spectroscopy highlights a distinctive compositional evolution of Cretaceous glauconite within the Ukra Hill Member. Glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf. The concentration of glau-conite steadily increases towards the maximum flooding surface, maximizing around 50%, and sharply falls at the onset of progradation. Unlike most Phanerozoic examples, Ukra glauconite forms by the variable degree of replacement of quartz, feldspar and mica grains. XRD, FEG-SEM and spectroscopy of glauconite pellets indicate an 'evolved' stage of maturation. Mossbauer spectroscopy reflects a minor substitution of Al 3þ-Fe 3þ (total) in tetrahedral sites and significant substitution of the same in octahedral sites. A consistently high value of K 2 O as well as Fe 2 O 3 contradicts the two popular theories, 'layer lattice' and 'verdissement', and support replacement origin of glauconite in a high a Siþ and high a Kþ pore water environment. Incipiently formed glauconite records a marginal increase in K 2 O content accompanied by release of Al 2 O 3 and SiO 2 to form evolved glauconite pellets; those forming within quartz grains involve an addition of Fe 2 O 3 (total) content during maturation. The minimal increase in K 2 O content of incipiently formed glauconite, best exhibited by those formed within quartz grains is possibly related to stratigraphic condensation. Compositional evolution like this is exhibited by Precambrian glauconites involving abiotic substrates, but is unusual for the Phanerozoic. Original K 2 O and Fe 2 O 3 (total) content of glauconites is reduced around peripheries and fractures during diagenesis, adding to compositional variability.

The trip starts at the Beale Library parking lot at Truxtun and Q
Streets in Bakersfield, California. From the parking lot the tour
will proceed east onto Truxtun Avenue, south on Union Avenue, west
on State Highway 58 Freeway, south on State Highway 99, to Taft
Highway, Old River Road, State Highway 166, State Highway 33, Ojai,
State Highway 150, and ends at Carpinteria State Beach.
In order to present the maximum amount of information, most stops
are limited to 20 minutes, except for the lunchtime stop and the
optional side trip which will be longer. Participants are
encouraged to bring a sack lunch and beverages. All vehicles are
encouraged to bring a CB radio set.

Twenty years of continuous Earth observation by satellite SAR have resulted in numerous new insights into active volcanism, including a better understanding of subsurface magma storage and transport, deposition of volcanic materials on the surface, and the structure and development of volcanic edifices. This massive archive of data has resulted in fundamental leaps in our understanding of how volcanoes work - for example, identifying magma accumulation at supposedly quiescent volcanoes, even in remote areas or in the absence of ground-based data. In addition, global compilations of volcanic activity facilitate comparison of deformation behavior between different volcanic arcs and statistical evaluation of the strong link between deformation and eruption. SAR data are also increasingly used in timely hazard evaluation thanks to decreases in data latency and growth in processing and analysis techniques. The existing archive of SAR imagery is on the cusp of being enhanced by a new gene...