Geological map of Potter Peninsula (King George Island, South Shetland Islands, Antarctic Peninsula)

We present here a new geological map of Potter Peninsula (King George Island, South Shetland Islands). Like on adjacent Barton Peninsula, the morphology on Potter Peninsula is predominantly characterized by a glacial landscape with abrasion platforms offshore, in parts steep cliffs along the coast, and a rather smooth, hilly countryside in the interior. Potter Peninsula forms part of the downthrown Warszawa Block. The volcanic sequence cropping out here belongs to the King George Island Supergroup, with an observed local minimum thickness of approx. 90 m (Kraus 2005). The most prominent morphological feature is Three Brothers Hill (196 m), a well known andesitic plug showing conspicuous columnar jointing. It marks the final stage of activity of a Paleogene volcano, whose eruption products (lava flows and pyroclastic rocks), together with hypabyssal intrusions related to the volcanism, make up most of the lithology observed on Potter Peninsula (Kraus 2005). The Three Brothers Hill volcanic complex is eroded down to its deepest levels. Thus, the stratigraphically deepest units from the initial phase of volcanic activity are cropping out in some parts (Kraus & del Valle, in Wienke et al. 2008). The lithology on Potter Peninsula comprises lava flows (~50%), pyroclastic rocks (ash-fallout, pyroclastic flow deposits, volcanic breccia and agglomerates, ~30%) and hypabyssal intrusions (dykes, sills and small subvolcanic intrusive bodies, ~20%). 40Ar/39Ar datings carried out on magmatic dykes from Potter Peninsula indicate a short, but intense intrusive event during the Lutetian (Kraus et al. 2007).

Astronomical time scale for Paleocene and early Eocene sediments

The astronomical-tuned time scale is rapidly extended into the Paleogene but, due to the existence of an Eocene gap, different tuning options had to be presented for the Paleocene. These options differ both in number and tuning of ~405-kyr eccentricity related cycles and are only partially consistent with recalculated 40Ar/39Ar constraints for the Cretaceous/Paleogene (K/Pg) and Paleocene/Eocene (P/E) boundaries. In this paper, we evaluate the cyclostratigraphic interpretation of records from ODP Leg 198 and 208 sites, and the Zumaia section to solve the problem of the different tuning options. We found that the interval between the K/Pg boundary and the early Late Paleocene biotic event (ELPE) comprises 17 instead of 16 * ~405-kyr eccentricity related cycles as previously proposed, while the entire Paleocene contains 25 * ~405-kyr cycles. Starting from 40Ar/39Ar age constraints for the K/Pg boundary, a new tuning to 405-kyr eccentricity is presented for the Paleocene and earliest Eocene, which results in ages of ~66.0 and ~ 56.0 Ma for the K/Pg and P/E boundaries, respectively. This tuning introduces considerable differences in age for a number of nannofossil events at ODP Sites 1209 and 1262 in the interval between 61 and 63 Ma, but eliminates large and abrupt changes in the seafloor spreading rate. The tuning seems further consistent with recalculated 40Ar/39Ar ages for ash layer -17 of early Eocene age. However, despite this apparent consistency with existing radio-isotopic constraints, an alternative 405-kyr younger or, less likely, older tuning cannot be excluded at this stage.

Isotopic geochemistry of lavas at DSDP Holes 81-553 and 81-555

It is demonstrated by K-Ar analyses that the age of reversely magnetized basalts, which immediately predate magnetic Anomaly 24B, is 53.5 ± 1.9 m.y. Samples from deep levels appear to be grossly contaminated by an extraneous argon component with a uniform argon-40/argon-36 ratio 440. This component is thought to have been derived from fluids circulating in the lava pile during burial. The age result corroborates the assignment previously made to Anomaly 24B by Hailwood et al. (1979) and Lowrie and Alvarez (1981). It additionally suggests that lava extrusion formed part of a much larger magmatic event, which affected wide areas of the North Atlantic margins around the Paleocene/Eocene boundary, and can therefore probably be considered a good estimate of the age of this boundary. Initial 143Nd/144Nd ratios lie in the very restricted range 0.512920 ± 19 to 0.513026 ± 24 and initial 8 7Sr/86Sr ratios from ca. 0.703 to ca. 0.705. Acid leaching reduces the latter range to 0.70264 ± 4 to 0.70384 ± 4, suggesting that the higher 87Sr/86Sr ratios resulted from interaction with seawater. The array of data for treated samples is closely conformable on a 143Nd/144Nd-87Sr/86Sr diagram with the main oceanic mantle array and with previously published fields for Atlantic Ocean basalts. No evidence for any continental crustal contamination has been found. This suggests, but does not prove, that continental crust played no part in the genesis of these rocks.

Carbon isotope record of 3 profiles from Campanian-Maastrichtian

Carbon-isotope stratigraphy has proven to be a powerful tool in the global correlation of Cretaceous successions. Here we present new, high-resolution carbon-isotope records for the Global Boundary Stratotype Section and Point (GSSP) of the Maastrichtian stage at Tercis les Bains (France), the Bottaccione and Contessa sections at Gubbio (Italy), and the coastal sections at Norfolk (UK) to provide a global d13C correlation between shelf-sea and oceanic sites. The new d13C records are correlated with d13C-stratigraphies of the boreal chalk sea (Trunch borehole, Norfolk, UK, Lägerdorf-Kronsmoor-Hemmoor section, northern Germany, Stevns-1 core, Denmark), the tropical Pacific (ODP-Hole 1210B, Shatsky Rise) and the South Atlantic and Southern Ocean (DSDP Hole 525A, ODP Hole 690C) by using an assembled Gubbio d13C record as a reference curve. The global correlation allows the identification of significant high-frequency d13C variations that occur superimposed on prominent Campanian-Maastrichtian events, namely the Late Campanian Event (LCE), the Campanian-Maastrichtian Boundary Event (CMBE), the mid-Maastrichtian Event (MME), and the Cretaceous-Paleogene transition (KPgE). The carbon-isotope events are correlated with the geomagnetic polarity scale recalculated using the astronomical 40Ar/39Ar calibration of the Fish Canyon sanidine. This technique allows the evaluation of the relative timing of base occurrences of stratigraphic index fossils such as ammonites, planktonic foraminifera and calcareous nannofossils. Furthermore, the Campanian-Maastrichtian boundary, as defined in the stratotype at Tercis, can be precisely positioned relative to carbon-isotope stratigraphy and the geomagnetic polarity timescale. The average value for the age of the Campanian-Maastrichtian boundary is 72.1 ± 0.1 Ma, estimated by three independent approaches that utilize the Fish Canyon sanidine calibration and Option 2 of the Maastrichtian astronomical timescale. The CMBE covers a time span of 2.5 Myr and reflects changes in the global carbon cycle probably related to tectonic processes than to glacioeustasy. The duration of the high-frequency d13C variations instead coincides with the frequency band of long eccentricity, indicative of orbital forcing of changes in climate and the global carbon cycle.

Age and chemical composition of dredged igneous rocks from the Vityaz Ridge, Pacific slope of the Kuril Island Arc

Original results of igneous rock studies are presented. The rocks were dredged during a marine expedition (cruise 37 of R/V Akademik M.A. Lavrent'ev in August-September, 2005) in the region of the submarine Vityaz Ridge and the Kuril Arc outer slope. Several age complexes (Late Cretaceous, Eocene, Late Oligocene, Miocene, and Pliocene-Pleistocene) are recognizable on the Vityaz Ridge. These complexes are characterized by a number of common geochemical features since all of them represent formations of island arc calc-alkali series. At the same time, they also have individual features reflecting different geodynamic settings. The outer slope of the Kuril Arc demonstrates submarine volcanism. Pliocene-Pleistocene volcanic rocks dredged here are similar to volcanites of the Kuril-Kamchatka Arc frontal zone.

Chemical composition and K-Ar age of rocks from the northern Sea of Japan

The Middle Paleozoic complex consists of terrigenous and volcanogenic materials metamorphized in greenschist facies. Clastic rocks have arkosic composition and are formed by alteration of basalts and metamorphic rocks. Metaeffusives were formed from basaltoid products of oceanic tholeiite magma indicating that underwater rise structures of the northern Sea of Japan were emplaced on the oceanic crust.

Petrology, geochemistry and K-Ar Age determination of De Gerlache Seamount basalts

The De Gerlache Seamounts are two topographic highs in the Bellingshausen Sea, southeastern Pacific. Petrological and geochemical studies together with K-Ar age determinations were carried out on four dredged basalt samples collected during a RV Polarstern expedition (ANT-XII/4) in 1995. Minor and trace element composition suggest alkaline basalt compositions. Compared to alkaline basalts of adjacent West Antarctica (the Jones Mountains) and of Peter I Island, the samples have lower mg-numbers, lower Ni and Cr contents and lower high field-strength elements (HFSE)/Nb and large-ion lithophile elements (LILE)/HFSE ratios. Three of the four samples have low K, Rb, and Cs concentrations relative to alkaline basalts. The K-depletion and other elemental concentrations may be explained by 1.1% melting of amphibole bearing mantle material. Additionally, low Rb and Ba values suggest low concentrations of these elements in the mantle source. K-Ar age determinations yield Miocene ages (20-23 Ma) that are similar in age to other alkaline basalts of West Antarctica (Thurston Island, the Jones Mountains, Antarctic Peninsula) and the suggested timing of onset of Peter I Island volcanism (~10-20 Ma). The occurrence of the DGS and Peter I Island volcanism along an older but reactivated tectonic lineation suggests that the extrusions exploited a zone of pre-existing lithospheric weakness. The alkaline nature and age of the DGS basalts support the assumption of plume activity in the Bellingshausen Sea.

(Table 1) K-Ar age and inert-gas-isotopes at DSDP Holes 68-501, 69-504B and 69-505B

Conventional K-Ar ages have been determined and inert-gas abundances have been measured on representative samples of altered rocks from Deep Sea Drilling Project Holes 501, 504B, and 505B in an attempt to correlate their degree of alteration with inert-gas and K-Ar data. Samples taken from the first 60 meters below the sediment/basalt interface give significantly higher ages than would be expected from the magnetic stratigraphy, though at greater depths the calculated ages are in broad agreement with the expected age. The inert gas ratios 20Ne/36Ar, 36Ar/84Kr, and 84Kr/130Xe also show a marked discontinuity at the 60-meter depth, and all these effects are interpreted as being a consequence of low-temperature alteration produced by burial metamorphism and by interaction with sea water (halmyrolysis).

Age and chemical composition of volcaniclastic rocks from the Sea of Japan

Petrographic and geochemical studies showed that Oligocene - Early Miocene volcaniclastic rocks from the southern part of the Sea of Japan are ascribed to high-potassium aluminous rocks of sub-alkaline volcanic series from active continental margins. A comparative analysis revealed spatiotemporal relation of Oligocene - Early Miocene subaerial volcanism of the Sea of Japan with Late Cretaceous and Eocene - Early Miocene ignimbrite volcanism of the East Eurasian margin. This allows to refer the volcaniclastic rocks of the Sea of Japan to the stage of ignimbrite volcanism that occurred during relative quiescence against general extension in the continental margin setting.

Geochronological evidence for pervasive miocene weathering, Minas Gerais, Brazil

Ar-40/Ar-39 laser incremental-heating analyses of 22 individual grains of supergene cryptomelane from three weathering profiles, up to 400 km apart, in the Rio Doce valley and Barbacena regions at Minas Gerais, Brazil, show that the formation of weathering profiles in these regions is contemporaneous, suggesting a strong weathering event in the Middle to Late Miocene (10-8 Ma). The preservation of these Miocene samples at or near the present surface suggests that either erosion rates have been very low in the region since the Miocene or that a much thicker weathering mantle was present in the region originally. Assuming a constant thickness of weathering profiles in the region throughout the Tertiary, we may calculate weathering front propagation rates of 4-8 m Myr(-1) during the past 10 Ma. Copyright (C) 2004 John Wiley Sons, Ltd.

Elemental analysis of biological matrices by laser ablation high resolution inductively coupled plasma mass spectrometry (LA-HR-ICP-MS) and high resolution inductively coupled plasma mass spectrometry (HR -ICP -MS)

The need for elemental analysis of biological matrices such as bone, teeth, and plant matter for sourcing purposes has emerged within the forensic and geochemical laboratories. Trace elemental analyses for the comparison of materials such as glass by inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS has been shown to offer a high degree of discrimination between different manufacturing sources. Unit resolution ICP-MS instruments may suffer from some polyatomic interferences including 40Ar16O+, 40Ar 16O1H+, and 40Ca 16O+ that affect iron measurement at trace levels. Iron is an important element in the analysis of glass and also of interest for the analysis of several biological matrices. A comparison of the analytical performance of two different ICP-MS systems for iron analysis in glass for determining the method detection limits (MDLs), accuracy, and precision of the measurement is presented. Acid digestion and laser ablation methods are also compared. Iron polyatomic interferences were reduced or resolved by using dynamic reaction cell and high resolution ICP-MS. MDLs as low as 0.03 μg g-1 and 0.14 μg g-1 for laser ablation and solution based analyses respectively were achieved. The use of helium as a carrier gas demonstrated improvement in the detection limits of both iron isotopes (56Fe and 57Fe) in medium resolution for the HR-ICP-MS and with a dynamic reaction cell (DRC) coupled to a quadrupole ICP-MS system. ^ The development and application of robust analytical methods for the quantification of trace elements in biological matrices has lead to a better understanding of the potential utility of these measurements in forensic chemical analyses. Standard reference materials (SRMs) were used in the development of an analytical method using HR-ICP-MS and LA-HR-ICP-MS that was subsequently applied on the analysis of real samples. Bone, teeth and ashed marijuana samples were analyzed with the developed method. ^ Elemental analysis of bone samples from 12 different individuals provided discrimination between individuals, when femur and humerus bones were considered separately. Discrimination of 14 teeth samples based on elemental composition was achieved with the exception of one case where samples from the same individual were not associated with each other. The discrimination of 49 different ashed plant (cannabis) samples was achieved using the developed method. ^

Chemical composition of Late Cenozoic volcanic and volcaniclastic deposits from the western Woodlark Basin area, SW Pacific

Tephra fallout layers and volcaniclastic deposits, derived from volcanic sources around and on the Papuan Peninsula, form a substantial part of the Woodlark Basin marine sedimentary succession. Sampling by the Ocean Drilling Program Leg 180 in the western Woodlark Basin provides the opportunity to document the distribution of the volcanically-derived components as well as to evaluate their chronology, chemistry, and isotope compositions in order to gain information on the volcanic sources and original magmatic systems. Glass shards selected from 57 volcanogenic layers within the sampled Pliocene-Pleistocene sedimentary sequence show predominantly rhyolitic compositions, with subordinate basaltic andesites, basaltic trachy-andesites, andesites, trachy-andesites, dacites, and phonolites. It was possible to correlate only a few of the volcanogenic layers between sites using geochemical and age information apparently because of the formation of strongly compartmentalised sedimentary realms on this actively rifting margin. In many cases it was possible to correlate Leg 180 volcanic components with their eruption source areas based on chemical and isotope compositions. Likely sources for a considerable number of the volcanogenic deposits are Moresby and Dawson Strait volcanoes (D'Entrecasteaux Islands region) for high-K calc-alkaline glasses. The Dawson Strait volcanoes appear to represent the source for five peralkaline tephra layers. One basaltic andesitic volcaniclastic layer shows affinities to basaltic andesites from the Woodlark spreading tip and Cheshire Seamount. For other layers, a clear identification of the sources proved impossible, although their isotope and chemical signatures suggest similarities to south-west Pacific subduction volcanism, e.g. New Britain and Tonga- Kermadec island arcs. Volcanic islands in the Trobriand Arc (for example, Woodlark Island Amphlett Islands and/or Egum Atoll) are probable sources for several volcaniclastic layers with ages between 1.5 to 3 Ma. The Lusancay Islands can be excluded as a source for the volcanogenic layers found during Leg 180. Generally, the volcanogenic layers indicate much calc-alkaline rhyolitic volcanism in eastern Papua since 3.8 Ma. Starting at 135 ka, however, peralkaline tephra layers appear. This geochemical change in source characteristics might reflect the onset of a change in geotectonic regime, from crustal subduction to spreading, affecting the D'Entrecasteaux Islands region. Initial 143Nd/144Nd ratios as low as 0.5121 and 0.5127 for two of the tephra layers are interpreted as indicating that D'Entrecasteaux Islands volcanism younger than 2.9 Ma occasionally interacted with the Late Archean basement, possibly reflecting the mobilisation of the deep continental crust during active rift propagation.

Chemical and mineral composition of rocks from the Philippine Sea

The book is devoted to geology of the Philippine Sea floor. This region is studied most extensively among other marginal seas of the Pacific Ocean. Rocks of the sedimentary and basalt layers within this sea have been studied during five legs of D/S Glomar Challenger. International geological expedition on board R/V Dmitry Mendeleev carried out according to the Project ''Ophiolites of Continents and Comparable Rocks of the Ocean Floor''obtained unique collection of rocks from the second and third layers of the ocean crust in the Philippine Sea. The book provides detailed petrographic and geochemical description of igneous and sedimentary formations from the Philippine Sea and compares them with rocks of the continental ophiolite association. An analysis of structure and history of the ocean crust formation in the region is based on all known geological information. The main periods of tectonic movement activation and nature of their manifestations within the sea are shown.

(Table 3) Isotopic composition of pyrite sulfur and carbonate carbon in carbonate nodules and host sediments from Core DM9-666, Gulf of California

Isotopic-geochemical study revealed presence of mantle He (3He/4He up to 223x10**-8) in gases from mud volcanoes of Eastern Georgia. This fact confirms that the Middle Kura basin fill encloses an intrusive body previously distinguished from geophysical data. Wide variations of carbon isotopic composition d13C in CH4 and CO2 and chemical composition of gas and water at temporally constant 3He/4He ratio indicate their relation with crustal processes. Unusual direct correlations of 3He/4He ratio with concentrations of He and CH4 and 40Ar/36Ar ratio can be explained by generation of gas in the Cenozoic sequence of the Middle Kura basin.

Biomarker in Heinrich event layers

There are controversies regarding the origin of Heinrich layer 3 (H3), the massive ice-rafting and meltwater event in the North Atlantic during the last glacial cycle spanning a time window between 29 and 30 kyr B.P. Some argue in favor of a Laurentide Ice Sheet source similar to other Heinrich layers, while a contending view argues for the European ice sheet source. Existing geochemical proxies such as 40Ar/39Ar, 206Pb/204Pb, or epsilon-Nd, etc., could not be used to distinguish among various sources of ice-rafted debris in H3 because of their low abundances, suggesting a background glacial sediment signal. In order to circumvent this problem a biomarker-based approach is used to characterize the provenance of H layers 2, 3, and 4 and other non-Heinrich layers. The presence of hopanes and steranes and their aromatic counterparts in the H layers is incompatible with Recent sediments and is attributed to the transportation of organic matter because of the glacial erosion of source rocks. The most diagnostic and useful signatures of this ancient organic matter in the H layers are the dominance of C34 hopanoids over C33 and the occurrence of isorenieratane along with palaerenieratane. Biomarkers signatures in H layers 2 and 3 of the Labrador Sea suggest no difference in their source. Hydrocarbon distributions suggest that these sediments were derived from the Middle to Late Ordovician and Silurian source rocks of the Hudson Bay of eastern Canada. Biomarker data of the H layer 4 from the northwest Atlantic reveal that the sediments of this layer have a similar source to the H layers in the Labrador Sea.