Sedimentology on two core from the Bransfield Strait area

The raw material for these investigations are samples from marine (sub)surface sediments around the northern part of the Antarctic Peninsula. They had been sampled in the years 1981 to 1986 during several expeditions of the research vessels Meteor, Polarstern and Walther Herwig. 83 box core, gravity core and dredge samples from the area of the Bransfield Strait, the Powell Basin and the northern Weddell Sea have been examined for their grain-size distribution, their mineralogical and petrographical composition. Silt prevails and its clay proportions exceed 25% wt. in water depths greater than 2000 m. The granulometrical results reveal some typical sedimentation processes within the area of investigation. While turbiditic processes together with sediment input from melting icebergs control the sedimentation in the Weddell Sea, the South Orkney Island Plateau and the Powell Basin, the fine grained material from Bransfield Strait mainly relies on marine currents in the shelf area. In addition, the direct sediment input of coarse shelf sediments from the Bransfield Strait into the Powell Basin through submarine canyons could be proven. Variations in the grain-size composition with sediment depth are smalI. The mineral composition of the clay and fine silt fractions is quite uniform in all samples. There are (in decreasing order): illite, montmorillonite, chlorite, smectite, mixed-Iayers, as well as detrital quartz and feldspars. A petrographically based sediment stratigraphy can be established in using the considerable changes in the chlorite- and Ca-plagioclase portions in samples from Core 224. For this sedimentation area a mean sedimentation rate of 7 cm/1000 a is assumed. Remarkable changes in the portions of amorphous silica components - diatom skeletons and volcanic glass shards - appear all over the area of investigation. They contribute between 4-83 % to the clay and fine silt fraction. Several provinces according to the heavy mineral assemblages in the fine sand fraction can be distinguished: (i) a province remarkably influenced by minerals of volcanic origin south and north of the South Shetland Islands; (ii) a small strip with sediment dominated by plutonic material along the western coast of the Antarctic Peninsula and (iii) a sediment controlled by metamorphic minerals and rock fragments in the area of the Weddell Sea and Elephant Island. While taking the whole grain-size spectrum into account a more comprehensive interpretation can be given: the accessoric but distinct appearance of tourmaline, rutile and zircon in the heavy mineral assembly along the northwestern coast of the Antarctic Peninsula is in agreement with the occurrence of acid volcanic rock pieces in the coarse fraction of the ice load detritus in this region. In the vicinity of the South Shetland Islands chlorite appears in remarkable portions in the clay fraction in combination with leucoxene, sphene and olivine, and pumice as well as pyroclastic rocks in the medium and coarse grain fractions, respectively. Amphiboles and amphibole-schists are dominant on the South Orkney Island Plateau. In the sediments of the northwestern Weddell Sea the heavy mineral phases of red spinel, garnet, kyanite and sillimanite in connection with medium to highgrade metamorphic rocks especially granulitic gneisses, are more abundant. A good conformity between the ice rafted rock sampIes and the rocks in the island outcrops could be proven, especially in the vicinity of offshore islands nearby. On the continent enrichments of rock societies and groups appear in spacious outlines: acid effusive rocks in the west of the ice divide on the Antarctic Peninsula, clastic sedimentites at the tip of the Antarctic Peninsula and granoblastic gneisses in central and eastern Antarctica. Coarse grain detritus with more than 1 cm of diameter must have been rafted by icebergs. These rock fragments are classified as rock types, groups and societies. The spacial distribution of their statistically determined weight relations evidently shows the paths of the iceberg drift and in nexus with already known iceberg routes also point to the possible areas of provenance, provided that the density of sample locations and the number of rock pieces are sufficient.

Sandstone and siltstone beds overlying conglomerate at DSDP Hole 59-439

Massive sandstone and siltstone beds with many shallow-water megafossils overlie acidic volcanic conglomerates at DSDP Site 439. Smear-slides, thin sections from coarse fractions, and heavy minerals of the sandstone and siltstone beds were analyzed. The sandstones and siltstones are very rich in lithic fragments and are classified as lithic arenite and (or) lithic wacke. Hornblende and clinopyroxene are abundant, and zircon is present in most of the examined samples. The proportions of sandstone, chert, and volcanic rock in the coarse fraction are variable, but fragments of clastic rocks and cherts are predominant. Plagioclase crystals of volcanic-rock origin, such as highly zoned plagioclase and very fine, euhedral, lath-shaped plagioclase, are frequently observed. Metamorphic-rock fragments and metamorphic minerals are also observed. Thus, the provenance of the sandstone and siltstone beds appears to have been a slightly mature island arc, the Oyashio ancient landmass, consisting of clastic sediments and metamorphic and volcanic rocks.

Güímar and La Orotava mega-landslides (Tenerife) and tsunamis deposits in Canary Islands

More than 20 mega-landslides have been described in the Canary Islands affecting the flanks of the volcanic edifices. Gliimar and La Orotava landslides, in Tenerife, are two exceptional cases due to their huge dimensions and outstanding geomorphological features. The estimated volume of these landslides exceed tens of cubic km. Tsunami deposits have been also identified in some of the islands of the archipelago probably associated to the large landslides of the islands flanks. An investigation has been carried out to explain the causes of these large instability processes and their failure mechanisms. One of the main aspects investigated was the geomechanical characteristics of the volcanic rock masses, specially the hyaloclastite rocks forming the substratum underlying the emerged volcanic building. The low strength and high deformability properties of these rocks have played a fundamental role on the stability of the island flanks. The results have shown the gravitational origin of these instability processes as the main failure mechanism. Volcanic eruptions or large earthquakes could be contributing factors to the instability, but according with the data obtained in Gliimar and La Orotava cases they are not necessary as triggering factors. As a result of the field work carried out in the frame of the project, three large tsunami deposits have been identified in the islands of Lanzarote, Tenerifc and Gran Canaria attributed to rnega-Iandslides, possibly related to Guimar and La Orotava. A Sumrnary of their main features is described.

Observation of manganese deposits made during the 1936 transect of C/S Lord Kelvin through the Northern Atlantic Ocean

In May and June 1936 Dr. C. S. Piggot of the Geophysical Laboratory, Carnegie Institution of Washington, took a series of 11 deep-sea cores in the North Atlantic Ocean between the Newfoundland banks and the banks off the Irish coast. These cores were taken from the Western Union Telegraph Co.'s cable ship Lord Kelvin with the explosive type of sounding device which Dr. Piggot designed. All but two of these cores (Nos. 8 and 11) are more than 2.43 meters (8 feet) long, and all contain ample material for study. Of the two short cores, No. 8 was taken from the top of the Faraday Hills, as that part of the mid-Atlantic ridge is known, where the material is closely packed and more sandy and consequently more resistant; No. 11 came from a locality where the apparatus apparently landed on volcanic rock that may be part of a submarine lava flow.

Mineralogy and chemistry of bentonitic clays from the Wombat and Exmouth Plateaus

Bentonites (i.e., smectite-dominated, altered volcanic ash layers) were recovered in Berriasian to Valanginian hemipelagic sediments of the Wombat Plateau (Site 761) and southern Exmouth Plateau (Site 763). They are compared to coeval bentonites in eupelagic sediments of the adjacent Argo Abyssal Plain (Sites 261 and 765) and Gascoyne Abyssal Plain (Site 766). A volcaniclastic origin with dacitic to rhyolitic ash as parent material is suggested by the abundance of well-ordered montmorillonite, fresh to altered silicic glass shards, volcanogenic minerals (euhedral sanidine, apatite, and long-prismatic zircon), and volcanic rock fragments, and by a vitroclastic ultrafabric (smectitized glass shards). We distinguish (1) pure smectite bentonites with a white, pink, or light gray color, a waxy appearance, and a very homogeneous, cryptocrystalline smectite matrix (water-free composition at Site 761: 68.5% SiO2, 0.27% TiO2, 19.1% Al2O3, 3.3% Fe2O3, 0.4%-1.1% Na2O, and 0.6% K2O) and (2) impure bentonitic claystones containing mixtures of volcanogenic smectite and pyroclastic grains with terrigenous and pelagic components. The ash layers were progressively altered during diagenesis. Silicic glass was first hydrated, then slightly altered (etched with incipient smectite authigenesis), then moderately smectitized (with shard shape still intact), and finally completely homogenized to a pure smectite matrix without obvious relict structures. Euhedral clinoptilolite is the latest pore-filling or glass-replacing mineral, postdating smectite authigenesis. Volcanic activity was associated with continental breakup and rapid subsidence during the "juvenile ocean phase." Potential source areas for a Neocomian post-breakup volcanism include the Wombat Plateau, Joey and Roo rises, Scott Plateau, and Wallaby Plateau/Cape Range Fracture Zone. Westward-directed trade winds transported silicic ash from these volcanic source areas to the Exmouth Plateau into the adjacent abyssal plains. The Wombat Plateau bentonites are interpreted as proximal ash turbidites.

Grain counts and relative abundances of volcaniclastic sands and sandstones of ODP Leg 180 sites

Modal analysis of middle Miocene to Pleistocene volcaniclastic sands and sandstones recovered from Sites 1108, 1109, 1118, 1112, 1115, 1116, and 1114 within the Woodlark Basin during Leg 180 of the Ocean Drilling Program indicates a complex source history for sand-sized detritus deposited within the basin. Volcaniclastic detritus (i.e., feldspar, ferromagnesian minerals, and volcanic rock fragments) varies substantially throughout the Woodlark Basin. Miocene sandstones of the inferred Trobriand forearc succession contain mafic and subordinate silicic volcanic grains, probably derived from the contemporary Trobriand arc. During the late Miocene, the Trobriand outerarc/forearc (including Paleogene ophiolitic rocks) was subaerially exposed and eroded, yielding sandstones of dominantly mafic composition. Rift-related extension during the late Miocene-late Pliocene led to a transition from terrestrial to neritic and finally bathyal deposition. The sandstones deposited during this period are composed dominantly of silicic volcanic detritus, probably derived from the Amphlett Islands and surrounding areas where volcanic rocks of Pliocene-Pleistocene age occur. During this time terrigenous and metamorphic detritus derived from the Papua New Guinea mainland reached the single turbiditic Woodlark rift basin (or several subbasins) as fine-grained sediments. At Sites 1108, 1109, 1118, 1116, and 1114, serpentinite and metamorphic grains (schist and gneiss) appear as detritus in sandstones younger than ~3 Ma. This is thought to reflect a major pulse of rifting that resulted in the deepening of the Woodlark rift basin and the prevention of terrigenous and metamorphic detritus from reaching the northern rift margin (Site 1115). The Paleogene Papuan ophiolite belt and the Owen Stanley metamorphics were unroofed as the southern margin of the rift was exhumed (e.g., Moresby Seamount) and, in places, subaerially exposed (e.g., D'Entrecasteaux Islands and onshore Cape Vogel Basin), resulting in new and more proximal sources of metamorphic, igneous, and ophiolitic detritus. Continued emergence of the Moresby Seamount during the late Pliocene-early Pleistocene bounded by a major inclined fault scarp yielded talus deposits of similar composition to the above sandstones. Upper Pliocene-Pleistocene sandstones were deposited at bathyal depths by turbidity currents and as subordinate air-fall ash. Silicic glassy (high-K calc-alkaline) volcanic fragments, probably derived from volcanic centers located in Dawson and Moresby Straits, dominated these sandstones.

Iwo Jima Photo Album, Image 18

Tunnels carved by the Japanese on Iwo Jima. Caption; "Elaborate caves and tunnels were carved out of the volcanic rock throughout the island."

Summary of 40Ar/39Ar results from sediment core CRP-2A (Table 1)

40Ar/39Ar analyses of tephra and clasts of volcanic rock provide age constraints for upper parts of the CRP-2A core. Single-crystal laser-fusion analyses of anorthoclase phenocrysts from three tephra-bearing layers yielded the most precise age constraints for CRP-2A. The dated tephra layers are: 1) a 2.7-m-thick interval of pumice and ash layers between 111.5 and 114.2 meters below sea floor (mbsf) (weighted mean age = 21.44 ± 0.05 Ma, +2.2); 2) a concentration of pumice near 193.4 mbsf (23.98 ± 0.13 Ma): and 3) a concentration of pumice near 280 mbsf (24,22 ± 0.03 Ma) (all ages are calibrated relative to Fish Canyon Tuff sanidine at 27.84 Ma). The 111 to 114 mbsf tephra is almost entirely non-reworked, and the 193 mbsf and 280 mbsf tephra concentrations are interpreted as being reworked and redeposited soon after eruption. All three of the tephra ages are therefore considered to be equivalent to depositional ages. The variation in precision of these three age determinations is largely a function of phenocryst size and abundance. The accuracy of these ages is equal to the accuracy of the current calibration of the 40Ar/39Ar methode (about ± 1 %). 40Ar/39Ar results from volcanic clasts provide three additional maximum age constraints for the CRP-2A core. Single-crystal laser-fusion of sanidine phenocrysts from a rhyolitic clast from 294 mbsf yielded a precise maximum depositional age of 24.98 ± 0.08 Ma, and plateau ages of groundmass concentrates from basaltic clasts near 36.02 mbsf and 125.92 mbsf yielded maximum depositional ages of 19.18 ± 0.12 Ma, and 22.56 ± 0.14 Ma, respectively. The 40Ar/39Ar data, in association with biostratigraphic, paleomagnetic, and isotopic age constraints for CRP-2A, confirm interpretation for rapid sedimentation rates in the 36 to 280 mbsf interval, particularly in the 193 to 280 mbsf interval where they support interpretations for sedimentation cycles spanning 100 k.y. intervals. In addition to the 19 to 25 Ma ages measured from thephra layers and clasts, provenance-related ages ranging from 150 to 450 Ma were determined from clasts and individual detrital or xenocrystic crystals from CRP-2A.

(Table 3, page 280) Chemical composition of micronodules from a series of stations and sediment depths from Areas C, F, G and K in the Pacific Ocean from R/V Sonne Cruise SO06

Compositional data for coexisting manganese nodules, micronodules, sediments and pore waters from five areas in the equatorial and S.W. Pacific have been obtained. This represents the largest study of its type ever undertaken to establish the distribution of elements between the various phases within the sediment column. The composition of manganese nodules, micronodules and sediments (on a carbonate-free basis) shows marked differences between the equatorial high productivity zone and the low productivity region of the S.W. Pacific. In the case of the nodules, th is reflects an increased supply of transition elements (notably Ni, Cu and Zn) to the nodules as a result of the in situ dissolution of siliceous tests within the sediment column in the equatorial Pacific high productivity zone. Micronodules display similar, but somewhat different, compositions to those of the associated nodules in each area. Micronodule composition is therefore influenced by the same basic factors that control nodule composition, but is modified by dissolution of the micronodules in situ within the sediment column. Locally, as in the area immediately south of the Marquesas Fracture Zone, the micronodule population is contaminated by small, angular volcanic rock fragments; this leads to apparently anomalous micronodule compositions. Micronodules appear to be a transient feature in the sediment column, especially in the equatorial Pacific. Dissolution of micronodules in the sediment column therefore represents an important source of elements for the growth of manganese nodules in the equatorial Pacific. Sediment composition is markedly influenced by the carbonate content. On a carbonate-free basis, the sediments from the equatorial high productivity zone are quite distinct in composition from those in the S.W. Pacific. This reflects differences in the lithology of the sediments. In the Aitutaki Passage, the local influence of volcanoclastic material in sediment composition has been established. The major cations and anions in pore waters measured here show no major differences between equatorial and S.W. Pacific sediments. Silica is, however, higher in equatorial Pacific pore waters reflecting the dissolution of siliceous tests in these sediments.

Protected cropping for specialty melons in North Queensland

Protective cropping could be an effective system for growing specialty melons in the dry tropics of North Queensland. The growing system could reduce outdoor risks for production loss, improve fruit quality, increase yield per m2, allow production offseason, and used for supplying niche markets in a segment of the larger melon market in Australia. First evaluations in Giru, Queensland, included seven cultivars of fruit types 'Galia', 'Hami', 'Charentais', small 'Canary', and 'Rockmelon', transplanted July 25, 2013 under a high polyethylene-covered tunnel. Plants were grown at a density of 2.8 plants m-2 in containers filled with volcanic rock and irrigated with a complete nutrient solution. Pruning and trellising was done to a single vertical stem, keeping lateral shoots on the main stem after the 7th leaf node. After bearing small fruit, lateral shoots were cut off after their second or third leaf node. To facilitate insect pollination, a screen window in the tunnel was left partially opened. On November 20 the cultivars had combined marketable yields that ranged from 2.8 to 8.2 fruits m-2 and 3.1 to 7.8 kg m-2. Total soluble solids levels in fruit ranged from 6 to 13 °Brix. Cultivars 'Tempo' ('Galia'), 'Tikal' ('Canary') and 'Sultan' ('Charentais') had fruit yields that were up to 2.6 times greater than yields commonly achieved with field-grown rockmelon crops. Sugar levels in fruits and marketable yields may be increased with changes in fertigation management. Promising results in this first evaluation justify examination of a greater number of genetic materials, in addition to the development of economic feasibility studies and further adaptive research to refine crop recommendations for growing melons in protective cropping systems.

Investigating Microbial Trace-fossils and Abiotic Alteration in Hydrovolcanic Tuffs of the Fort Rock Volcanic Field, Oregon

Microbial ichnofossils in volcanic rocks provide a significant record of subsurface microbes and potentially extraterrestrial biosignatures. Here, the textures, mineralogy, and geochemistry of two continental basaltic hydrovolcanic deposits - Reed Rocks and Black Hills - in the Fort Rock Volcanic Field (FRVF) are investigated. Methods include petrographic microscopy, micro and powder X-ray diffraction, SEM/BSE/EDF imaging, energy dispersive spectroscopy, stable isotopes, and X-ray fluorescence. Petrographic analysis revealed granular and tubular textures with biogenic morphologies that include terminal enlargements, septate divisions, branching forms, spiral filaments, and ovoid bodies resembling endolithic microborings described in ocean basalts. They display evidence of behaviour and a geologic context expressing their relative age and syngenicity. Differences in abiotic alteration and the abundance/morphotype assemblage of putative microborings between the sites indicate that water/rock ratio, fluid composition and flux, temperature and secondary phase formation are influences on microboring formation. This study is the first report of reputed endolithic microborings in basalts erupted in a continental lacustrine setting.