An Interpretation of ISO Guidelines for the Certification of Geological Reference Materials

Recommendations for the certification of reference materials, as published by the International Organisation for Standardisation (ISO), are reviewed and proposals made as to how they can be adapted for the certification of new geological reference materials. Whilst acknowledging the important contribution made by the large number of existing matrix-matched geological reference materials, it is recommended that future characterisation programmes should follow the ISO guidelines for certification, not the least so that laboratories can readily use the resultant samples to establish the traceability of geoanalytical results.     

Potentiometric determination of calcium and magnesium in seawater

Methods are described for the complexometric determination of calcium and magnesium in seawater, using an amalgamated silver electrode for end-point detection. In the presence of a small amount of mercury(II)-chelonate, the amalgamated silver electrode serves as a pM indicator during the complexometric titration, the Hg complex being stronger than Ca, Mg and Sr complexes. Calcium is determined by titration with EGTA, calcium+magnesium+strontium by titration with EDTA and magnesium is obtained by difference. Average values of 0.02120 (standard deviation 0.00004) for Ca:Cl‰ and 0.06671 (standard deviation 0.00014) for Mg:Cl‰ were obtained for samples from tropical North Atlantic Ocean.     

Pebbly mud transport in the head of Wilmington Canyon

Direct visual observation of the Wilmington Canyon axis by research submersible shows that the fill is a very poorly sorted mix of coarse fragments (pebbles, cobbles) dispersed in a muddy matrix. This facies resembles pebbly mudstone units not infrequently associated with ancient deep marine sequences. Earlier dredge, television and camera surveys reveal the widespread nature of slump deposits on the adjacent canyon walls; this type of failure is the major process in the canyon head in terms of sediment volume displaced. Surprisingly, however, only a thin fill occupies the V-shaped axial channel. It is proposed here that down-wall slumps are transformed to debris flow in the axis, and the latter serves as the canyon head flushing mechanism.     

Middle miocene deduction and late miocene beginning of collision registered in the hengchun peninsula: Geodynamic implications for the evolution of Taiwan

Taiwan is located in the axis of the Manila Trench. It results from an oblique collision between the northernmost part of the Luzon arc and the Chinese passive margin. This active collision follows the subduction of the Oligocene-Miocene oceanic crust of the South China Sea along the Manila Trench. The tectonized Chinese margin emerged in the Hengchun peninsula (South Taiwan). Gentle folds which are delineated by the Quaternary reefal limestones demonstrate Recent deformations. These folds deformed a thick detrital sequence of Miocene age (Ssuchung Chi series) which was previously strongly folded and thrust westward (axis NS-N20) upon the Renting mélange of Latest Miocene age. These main deformations, sealed by the Middle Pliocene, are the evidence for the onset of collision in this part of Taiwan at the end of the Miocene. Because of its obliquity, the collision started already in the northern part of Taiwan during the Late Miocene (6-7-8 Ma ?).The Ssuchung Chi series, a sequence of proximal turbidites, has contained, since the Middle Miocene (NN 6~13 Ma), fragments of an Oligocene to Lower Miocene oceanic crust. This ophiolitic material is very similar to the East Taiwan Ophiolite of the Coastal Range. It originated most probably from a slice of South China Sea crust obducted in Middle Miocene times (13–14 Ma) upon the Chinese margin (North of the Hengchun peninsula). This obduction occurred 7 to 8 Ma before the beginning of collision. These results make it possible to propose an evolutionary model for Taiwan from the Oligocene to the Recent, with the different phases of a collision between a volcanic arc and a passive margin.     

The multiple chronological techniques applied to the Lake Suigetsu SG06 sediment core,central Japan

The varved sediment of Lake Suigetsu (central Japan) provides a valuable opportunity to obtain high‐resolution, multi‐proxy palaeoenvironmental data across the last glacial/interglacial cycle. In order to maximize the potential of this archive, a well‐constrained chronology is required. This paper outlines the multiple geochronological techniques being applied – namely varve counting, radiocarbon dating, tephrochronology (including argon–argon dating) and optically stimulated luminescence (OSL) – and the approaches by which these techniques are being integrated to form a single, coherent, robust chronology. Importantly, we also describe here the linkage of the floating Lake Suigetsu (SG06) varve chronology and the absolute (IntCal09 tree‐ring) time scale, as derived using radiocarbon data from the uppermost (non‐varved) portion of the core. This tie‐point, defined as a distinct (flood) marker horizon in SG06 (event layer B‐07–08 at 1397.4 cm composite depth), is thus derived to be 11 255 to 11 222 IntCal09 cal. years BP (68.2% probability range).     

Trophic ecology of Pomatoschistus microps within an intertidal bay (Roscoff,France), investigated through gut content and stable isotope analyses

The diet of Pomatoschistus microps has been studied using both gut content and stable isotope analyses. In the Roscoff Aber Bay (Brittany, France), this fish is commonly found on sandy muddy intertidal flats. Gut content analyses were also interpreted using trophic indices. Owing to the large diversity of prey consumed, these indices emphasised the opportunistic feeding behaviour of P. microps. Here, this species fed mainly on endofauna with meiofauna being of high relative importance. The main biotic components of its trophic habitat, characterized by δ¹³C and δ¹⁵N, provided evidence of a major trophic pathway based on drift Enteromorpha sp. Trophic positions estimated by both diet analyses and isotopic analyses led to similar results. In this bay, P. microps is a first‐order predator with a low degree of omnivory. Despite a preferential consumption of the amphipod Corophium arenarium, we assumed that this goby behaves as a generalist feeding on a uniform variety of endofauna taxa.     

High-resolution record of tectonic and sedimentary processes in growth strata

Growth strata are used to determine the kinematics of synsedimentary structures such as faults. Classical methods of analysis such as thickness versus throw plot consider that the available space created by fault slip in the hanging wall of faults is instantaneously filled up by sediments. This has lead many previous works to identify a cyclic activity for growth faults. Here we perform a careful analysis of the variation of strata thicknesses on each side of a very well documented normal growth fault in the Niger delta. We show that these thickness variations are induced by the alternation of sedimentary processes during continuous fault slip. Suspended-load processes induce either uniform or slightly variable thickness of a large majority of mudstone layers. Bedload processes result in a preferential thickening of sand layers in the hanging wall. These high quality data thus provide strong grounds for doubting the polycyclic growth diagnosed for some faults at the scale of sedimentary cycles and supports the notion that fault displacement rates can be very well behaved. Our study emphasizes the important conclusion that stable fault growth, and related displacement rates, can appear to be punctuated when viewed at the scale of sedimentary cycles. It follows that care should be taken when attempting to derive displacement rates on temporal scales equivalent to those of alternating sedimentological cycles.     

Integrative taxonomic description of Plakina kanaky,a new polychromatic sponge species from New Caledonia (Porifera: Homoscleromorpha)

Four similar sponges of different colors, all unknown to science, were collected in submarine caves of New Caledonia. We aimed at determining whether the four chromotypes represented different species or phenotypic variations of a unique new species. We used an integrative taxonomic approach combining morphologic, molecular and metabolomic analyses. The main traits that define these specimens are a skeleton made of monolophose, trilophose and tetralophose calthrops only, high chemical diversity and a high abundance and diversity of prokaryotic symbionts. The symbiotic community includes two unique prokaryote morphotypes, which are described for the first time in Homoscleromorpha, and appeared to be vertically transmitted. Although several features slightly differ among chromotypes, the most parsimonious conclusion was to propose a single new species Plakina kanaky sp. nov. Our phylogenetic analysis indicated the paraphyly of the Plakina genus, with P. kanaky sp. nov. belonging to a clade that includes Plakina jani and Plakina trilopha. The present work demonstrates that integrative taxonomy should be used in order to revise the entire Plakinidae family and especially the non‐monophyletic genus Plakina.     

Gravity Anomaly and Tectonics in the Northern Part of the North Fiji Basin - Preliminary Result of the 1994 NOFI Cruise under the NEW STARMER Programme

A surface ship gravity survey was carried out in the northern part of the North Fiji Basin during the NOFI cruise by the R/V l'Atalante in August-September, 1994. The two ridges inside the study area, the South Pandora Ridge and the Tripartite Ridge, present different structures and states of isostatic equilibrium in terms of gravity anomaly and its tectonic implications. The former is supported by a restoring force of an imaginary elastic plate in the crust and the latter by the Airy type isostasy. These characteristics can be derived from the difference in magmatic activity, as influenced by the difference in lithospheric structure. The latter is characterised by greater active magmatism and hydrothermalism underneath the ridge than the former. Such a difference in the magmatic activity and the horizontal scale of the shallow subsurface structure is derived from the difference in the stiffness or viscosity of the lithosphere beneath the two ridges.