The Helgeland Nappe Complex consists of a sequence of imbricated east-dipping nappes that record a history of Neoproterozoic-Ordovician, sedimentary, metamorphic, and magmatic events. A combination of U-Pb dating of zircon and titanite by laser-ablation-inductively coupled plasma-mass spectrometry plus chemostratigraphic data on marbles places tight constraints on the sedimentary, tectonic, and thermal events of the complex. Strontium and carbon isotope data have identifi ed Neoproterozoic marbles in the Lower Nappe, the Horta nappe, and Scandian-aged infolds in the Vikna region. The environment of deposition of these rocks was a continental shelf, presumably of Laurentia. Detrital zircon ages from the Lower Nappe are nearly identical to those of Dalradian sedimentary rocks in Scotland. Cambrian rifting caused development of one or more ophiolitefl oored basins, into which thick sequences of Early Ordovician clastic and carbonate sedi-ments were deposited. On the basis of ages of the youngest zircons, deposition ended after ca. 481 Ma. These basin units are now seen as the Skei Group, Sauren-Torghatten Nappe, and Middle Nappe, as well as the stratigraphically highest part of the Horta nappe and possibly of the Upper Nappe. The provenance of these sediments was partly from the Lower Nappe, on the basis of detrital zircon age populations in metasandstones and cobbles from proximal conglomerates. However, the source of Cambrian-Ordovician zircons in all of the Early Ordovician basins is enigmatic. Crustal anatexis of the Lower and Upper Nappes occurred ca. 480 Ma, followed by imbrication of the entire nappe sequence. By ca. 478 Ma, the Horta nappe was overturned and was at the structural base of the nappe sequence, where it underwent migmatization and was the source of S-type magmas. Diverse magmatic activity followed ca. 465 Ma, 450-445 Ma, and 439-424 Ma. Several plutons in the youngest age range contain inherited 460-450 Ma zircons. These zircons are interpreted to refl ect a deep crustal zone in which mafi c magmas caused melting, mixing, and hybridization from 460 to 450 Ma. Magmatic reheating of this zone, possibly associated with crustal thickening, resulted in voluminous, predominantly tonalitic magmatism from 439 to 424 Ma.

The WooleyCreek batholith is a tilted, zoned, calc-alkaline plutonic complex in the Klamath Mountains, northern California, USA. It consists of three main compositionaltemporal zones. The lower zone consists of gabbro through tonalite. Textural heterogeneities on the scale of tens to hundreds of meters combined with bulk-rock data suggest that it was assembled from numerous magma batches that did not interact extensively with one another despite the lack of sharp contacts and identical ages of two lower zone samples (U-Pb [zircon] chemical abrasion-isotope dilution-thermal ionization mass spectrometry ages of 158.99 ± 0.17 and 159.22 ± 0.10 Ma). The upper zone is slightly younger, with 3 samples yielding ages from 158.25 ± 0.46 to 158.21 ± 0.17 Ma, and is upwardly zoned from tonalite to granite. This zoning can be explained by crystalliquid separation and is related to upward increases in the proportions of interstitial K-feldspar and quartz. Porphyritic dacitic to rhyodacitic roof dikes have compositions coincident with evolved samples of the upper zone. These data indicate that the upper zone was an eruptible mush that crystallized from a nearly homogeneous parental magma that evolved primarily by upward percolation of interstitial melt. The central zone is a recharge area with variably disrupted synplutonic dikes and swarms of mafic enclaves. Central zone ages (159.01 ± 0.20 to 158.30 ± 0.16 Ma) are similar to both lower and upper zones crystallization ages. In the main part of the Wooley Creek batholith, age data constrain magmatism to a short period of time (<1.3 m.y.). However, age data cannot be used to identify distinct magma chambers within the batholith; such information must be extracted from a combination of fi eld observations and the chemical compositions of the rocks and their constituent minerals. GEOLOGIC SETTING Klamath MountainsThe Klamath Mountains geologic province, northwestern California and southwestern For permission to copy, contact editing@geosociety.org on July 1, 2015 geosphere.gsapubs.org Downloaded from Note: MSWD-mean square of weighted deviates. Sample: s-single grain; all multipoint dates are weighted mean 206 Pb/ 238 U dates; asterisk indicates sample excluded from weighted mean calculations. Weight represents estimated weight after fi rst step of CA-TIMS (chemical abrasion-thermal ionization mass spectrometry) zircon dissolution and is only approximate. U and Pb concentrations are based on this weight and are useful for internal comparisons only. Picograms of sample and common Pb from the second dissolution step are measured directly and are accurate. Sample Pb: sample Pb [radiogenic (rad.) + initial] corrected for laboratory blank. cPb: total common Pb. All assigned to laboratory blank unless >3 pg. Pb*/Pbc: radiogenic Pb to total common Pb (blank + initial). Corrected atomic ratios: 206 Pb/ 204 Pb corrected for mass discrimination and tracer, all others corrected for blank, mass discrimination, tracer and initial Pb; values in parentheses are 2σ errors in percent. Rho: 206 Pb...

Titanium dioxide nanomaterials (nano-TiO(2) ) exhibit stronger photochemical oxidation/reduction capacity compared with their bulk counterparts, but the effectiveness of nano-TiO(2) interaction with ultraviolet (UV) light strongly depends on particle size. In this study, the dependence of nano-TiO(2) toxicity on particle size and interaction with UV light were investigated. Toxicity tests with Xenopus laevis included eight concentrations of nano-TiO(2) in the presence of either white light or UVA (315-400 nm). We quantified viability and growth of Xenopus laevis. Results showed that, regardless of UV light exposure, increasing TiO(2) concentration decreased X. laevis survival (p < 0.05). Coexposure to 5-nm TiO(2) and UVA caused near-significant decreases in X. laevis survival (p = 0.08). Coexposure to 10-nm TiO(2) and UVA significantly decreased X. laevis survival (p = 0.005). However, coexposure to 32-nm TiO(2) and UVA had no statistical effect on X. laevis survival (p = 0.8). For all three particle sizes, whether alone or with UV light, the nano-TiO(2) concentrations significantly affected growth of tadpoles as determined by total body length, snout-vent length, and developmental stage. High-concentration TiO(2) solutions suppressed tadpole body length and delayed developmental stages. Further research to explore reasons for the growth and mortality in tadpoles is still underway in our laboratory. Given the widespread application of nano-TiO(2) , our results may be useful in the management of nano-TiO(2) released from industrial, municipal, and nonpoint sources.

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