Decadal- to interannual-scale source water variations in the Caribbean Sea recorded by Puerto Rican coral radiocarbon

Water that forms the Florida Current, and eventually the Gulf Stream, coalesces in the Caribbean from both subtropical and equatorial sources. The equatorial sources are made up of, in part, South Atlantic water moving northward and compensating for southward flow at depth related to meridional overturning circulation. Subtropical surface water contains relatively high amounts of radiocarbon (¹⁴C), whereas equatorial waters are influenced by the upwelling of low ¹⁴C water and have relatively low concentrations of ¹⁴C. We use a 250 year record of Δ¹⁴C in a coral from southwestern Puerto Rico along with previously published coral Δ¹⁴C records as tracers of subtropical and equatorial water mixing in the northern Caribbean. Data generated in this study and from other studies indicate that the influence of either of the two water masses can change considerably on interannual to interdecadal time scales. Variability due to ocean dynamics in this region is large relative to variability caused by atmospheric ¹⁴C changes, thus masking the Suess effect at this site. A mixing model produced using coral Δ¹⁴C illustrates the time varying proportion of equatorial versus subtropical waters in the northern Caribbean between 1963 and 1983. The results of the model are consistent with linkages between multidecadal thermal variability in the North Atlantic and meridional overturning circulation. Ekman transport changes related to tradewind variability are proposed as a possible mechanism to explain the observed switches between relatively low and high Δ¹⁴C values in the coral radiocarbon records.     

Outgoing long wave radiation variability from IR satellite data prior to major earthquakes

Our analysis of the continuous outgoing long wave earth radiation (OLR) indicates anomalous variations prior to a number of medium to large earthquakes. The most recent analysis of OLR is from the M9.0 Sumatra Andaman Islands mega trust event. We compared the reference fields for December 2001 to 2004 and found OLR anomalous values, > 80 W/m², (2σ) within the epicentral area on Dec 21, 2004, 5 days before the event. We used the NOAA/IR daily (one degree) and monthly (two and half degree) gridded data to differentiate between the global and seasonal variability and the transient local anomalies. The cause of such anomalies is not fully understood; one possible explanation is the existence of thermal outgoing radiation as a result of near ground air ionization and latent heat change due to change of air humidity and temperature. This phenomenon is hypothesized to be part of a relationship between tectonic stresses, electrochemical and thermodynamic processes in the atmosphere and increasing mid IR flux, all part of a family of electromagnetic (EM) phenomena related to earthquake activity. The time scale of the observed variations is a few weeks before the onset of the seismic event. In comparison with several years of data, the observed time-series preceding the earthquake had unusually high OLR. The OLR anomaly corresponds to a large area of ground coverage and coincides with the main epicentral zone. The significance of these observations is explored using data from most recent East Asian earthquake swarm of December 2004 and three other earthquakes.     

Post-Palaeozoic evolution of weathered landsurfaces in Uganda by tectonically controlled deep weathering and stripping

A model for the evolution of weathered landsurfaces in Uganda is developed using available geotectonic, climatic, sedimentological and chronological data. The model demonstrates the pivotal role of tectonic uplift in inducing cycles of stripping, and tectonic quiescence for cycles of deep weathering. It is able to account for the development of key landforms, such as inselbergs and duricrust-capped plateaux, which previous hypotheses of landscape evolution that are based on climatic or eustatic controls are unable to explain. Development of the Ugandan landscape is traced back to the Permian. Following late Palaeozoic glaciation, a trend towards warmer and more humid climates through the Mesozoic enabled deep weathering of the Jurassic/mid-Cretaceous surface in Uganda during a period of prolonged tectonic quiescence. Uplift associated with the opening South Atlantic Ocean terminated this cycle and instigated a cycle of stripping between the mid-Cretaceous and early Miocene. Deep weathering on the succeeding Miocene to recent (African) surface has occurred from Miocene to present but has been interrupted in the areas adjacent to the western rift where development of a new drainage base level has prompted cycles of stripping in the Miocene and Pleistocene.     

The kinematics of the ionized gas in the Circinus galaxy

The TAURUS-2 Fabry–Perot interferometer, mounted on the 3.9-m Anglo-Australian Telescope, has been used to observe the Circinus galaxy. We have mapped the intensity and velocity distribution of the ionized hydrogen in the galaxy using the Balmer series Hα spectral line.
The semiresolved core (observed with a seeing disc of 30 pc) appears amorphous in shape, which is commonly observed in Seyfert 2 galaxies. Its peak coincides with the core position measured in the radio continuum, suggesting that ionized gas surrounds a non-thermal source.
A circumnuclear ring or spiral of radius 220 pc and a rotational velocity of 350 km s⁻¹ (assuming circular motions) surrounds the core. The inclination angle of this feature, i =40°±10°, is less than that of the previously observed radio continuum disc. The velocity channel maps obtained for the Hα ring show that the kinematics resemble those of a rotating ring and the intensity displays a complex structure indicative of several, unresolved, H II regions. We believe the ring to represent a circumnuclear starburst.
Our Hα data also show the presence of the previously detected [O III ] ionization cone to the north-west of the core, measuring more than 400 pc in length. We suggest that the ionization cone lies in a different plane from that of the starburst ring and is directed away from us. Several kinematic components of the core are derived and we calculate an outflow velocity in excess of 150–200 km s⁻¹ for gas above the core of Circinus. We also present evidence for inflowing ionized gas at the centre of Circinus.
The correlation of the Hα and radio continuum features is discussed, as well as the possible presence of a starburst-driven superwind in the Circinus galaxy.     

Isotope geology of the bakircay porphyry copper prospect,northern turkey

Isotopic data for the Bakircay granodiorite porphyry, give a Late Eocene age for the development of the porphyry copper system. They suggest a close temporal and genetic relationship between igneous and hydrothermal activity, and indicate that magmatic-hydrothermal fluids produced potassic alteration and that meteoric fluids enriched in radiogenic⁸⁷Sr were responsible for propylitic alteration. The granodiorite porphyry is petrologically similar to porphyry copper-related intrusions from island arc and continental margin settings, which form a group with initial⁸⁷Sr/⁸⁶Sr ratios of less than 0. 7043, representing magmas produced in tectonic environments lacking any important component of old (i. e. Precambrian) continental material.     

Trace element fractionation trends of tholeiitic magma at moderate pressure: Evidence from an Al-spinel ultramafic-mafic inclusion suite

Trace element data on an Al-spinel ultramafic-mafic inclusion suite in an analcimite support earlier proposals that the various inclusions are comagmatic and represent fragments of a layered tholeiitic ‘pluton’ which differentiated at pressures close to 8 kb. Ultramafic inclusions are dominantly pyroxenites, often websteritic, whereas the mafic inclusions are largely two pyroxene-plagioclase assemblages. Appropriate experimental data and abundances of Sc, Cr and V indicate that subcalcic clinopyroxene or relatively Ca-rich clinopyroxene was the major ferromagnesian phase fractionated, often accompanied by spinel in the early and middle stages of differentiation and, in the later stages, by titanomagnetite. Comparatively moderate decreases in Ni and Co suggest that olivine was a relatively unimportant fractionating phase. Clinopyroxene fractionation at moderate pressures should be assigned only a comparatively insignificant role in the production of evolved basaltic compositions.     

Origin of granitic magma by crustal remobilisation: Rb-Sr and Pb/Pb geochronology and isotope geochemistry of the late Archaean Qôrqut Granite Complex of southern West Greenland

Rb-Sr and Pb/Pb whole rock isochrons on the Qôrqut Granite Complex yield ages of $\text{2530 ± 30}\text{Myr}\text{(}\text{initial}{}^{87}\text{Sr}{}^{86}\text{Sr}\text{= 0.7081 ± 0.0008)}$ and 2580 ± 80 Myr respectively. A model relating initial Sr and Pb isotopic compositions of the Qôrqut granites to the Sr and Pb isotopic compositions of the Amîtsoq gneisses (ca. 3700 Myr) and Nûk gneisses (ca. 2900 Myr) at 2550 Myr ago, as well as Sr and Pb contents of the gneiss units, suggests that between 40 and 50% of the Qôrqut granite magma was generated by partial melting of Amîtsoq gneisses, and the remainder by partial melting of Nûk gneisses.     

Geochemistry of upper cretaceous volcanic rocks from the pontic chain,northern turkey

Preliminary data on major elements, Cs, Ba, Rb, Pb, Sr, REE, Y, Th, U, Zr, Ht, Sn, Nb, W, Mo, Cr, V, Sc, Ni, Co and Cu contents for eight samples coming from the Upper Cretaceous volcanic belt of the Pontic Chain (Northern Turkey) are reported. SiO, versus K₂O relationship shows that the analyzed samples belong to the calc-alkaline and shoshonite series. The calc-alkaline rocks appear to represent two distinct magma types one close in composition to typical island are calc-alkaline magmas and one with high incompatible elements concentration and tractionated heavy REE patterns which suggest a genesis by partial melting at high pressure with a garnet bearing residue. Shoshonitic rocks show Na₂O/K₂O close to one, high incompatible elements concentration, and TiO₂%. Al₂O₃%, Ni and Co contents, Ni/Co and V/Ni ratios and REE patterns similar to typical island are andesites which suggest for these rocks similar genetical processes as the island are calc-alkaline magmas.     

Rare earth element geochemistry of Archean metasedimentary rocks from Kambalda,Western Australia

Archean sedimentary rocks of very limited lateral extent from horizons within basaltic and ultramafic volcanic sequences at Kambalda, Western Australia, are extremely variable in major elements, LIL and ferromagnesian trace element compositions. The REE patterns are uniform and do not have negative Eu anomalies. Two samples have very low total REE abundances and positive Eu anomalies attributed to a very much greater proportion of chemically deposited siliceous material. Apart from these two samples, the Kambalda data are similar to REE abundances and patterns from Archean sedimentary rocks from Kalgoorlie, Western Australia and to average Archean sedimentary rock REE patterns. These show a fundamental distinction from post-Archean sedimentary rock REE patterns which have higher $\text{La}\text{Yb}$ ratios and a distinct negative Eu anomaly.     

Risø 1978: Further investigations into the effects of local terrain irregularities on tower-measured wind profiles

Observations of flow over complex terrain taken at Risø during June–July 1978 and numerical studies confirm earlier findings that small variations in surface elevation have significant effects on mean wind profiles. Measured shear stresses in the nonequilibrium region of the flow are consistent with theory but quite different from those obtained assuming simple flux-profile relationships. These findings imply that flux-profile relationships can be quite complicated over other than simple homogeneous terrain.