Fjord Area Research Articles

Lichens from two inland localities in west Greenland and their climatic preferences

Abstract Hansen E. S., 2012: Lichens from two inland localities in West Greenland and their climatic preferences [Kerpės iš dviejų vidinių vakarinės Grenlandijos vietovių bei jų klimatinės preferencijos]. - Bot. Lith., 18(1): 19-26. In total, 143 lichen taxa collected from two inland localities in West Greenland are reported and categorized toward their climatic preferences in Greenland. Eighty three lichen taxa were collected in Eqaluit ilorliit in the Ameralik Fjord area in 2000 and 120 lichen taxa were collected in Utaap kuua, east of Sisimiut, in 1998. The two localities share 58 lichen taxa. Almost three fourths of the 143 lichens are more or less equally distributed in continental and oceanic areas in Greenland. About one sixth of the lichens occur most frequently in oceanic areas and more rarely in continental areas, while less than one tenth of the lichens occur frequently in continental areas and more rarely in oceanic areas. The climate of the two localities is low arctic, oceanic. Although they are situated at some distance from the outer coast and close to the continental zone, they are poor in lichens with a mainly continental distribution in Greenland compared to, for example, Kangerlussuaq, which is located in the continental inland region in the southernmost West Greenland.

Modeling suspended solids in a Northern Chilean Patagonia glacier-fed fjord: GLOF scenarios under climate change conditions

Suspended solids play an ecologically important role in glacier-fed fjords, given its dominant effect on their primary production arising from the generation of turbid water plumes by retreating glaciers, which increase light attenuation. Glacial-lake outburst floods, GLOFs, are sudden releases of lake-water impounded by a glacier which may affect either locally or regionally depending on the amount of water and suspended solids released. Chilean Patagonia has been characterized by some of the fastest glacial retreats worldwide and by an increase in GLOFs events. In this article we describe the development of a hydrodynamic model to study the distribution of suspended solids in the Baker channel, a glacier-fed fjord located in Northern Chilean Patagonia. We further describe the simulation of three climate change induced GLOF scenarios and discuss their potential effects on fjord's primary production. The model was implemented as a two-level, one-way, nested hierarchy using the MOHID water modeling system. The large extent, oceanic, level corresponded to a one-layer barotropic model, while the smaller extent, fjord, level corresponded to a 3D baroclinic model with 31 Cartesian layers. Velocities, salinity and suspended solids concentrations were calibrated using field measurements. Results show that the most likely scenario is a decrease in light penetration within the inner fjord's area. Only the most catastrophic scenario, equivalent to a large recorded paleo-discharge, would affect outer areas of the Northern Chilean fjords.

Climate-driven fluctuations in freshwater flux to Sermilik Fjord, East Greenland, during the last 4000 years

The freshwater runoff from the glaciated and snow-covered Sermilik Fjord catchment, SE Greenland, was estimated at annual resolution for the period 1900–2008 and at decadal resolution for the past four millennia. Our simulations were forced with available meteorological station data (1900–2008) and Greenland ice core estimated temperature data (1899 bc–ad 1980) from Dye3 and GISP2. Time series of estimated ice discharge (2000–2009) for the three major outlet glaciers Helheim, Fenris, and Midgård indicate that 53–74% of the ice discharge variations could be explained by variations in areally averaged glacier terminus surface (supraglacial) runoff. Based on these data and together with calculated subglacial geothermal and frictional melting as well as net precipitation for the fjord area, the Sermilik Fjord freshwater flux was deduced for the period 1900–2008. Our simulations indicated that during the last century surface freshwater runoff has equaled 13% of the Sermilik Fjord average freshwater flux of 33.0±5.7×109 m3/yr, covering a periodic runoff variation of 20 years. Ice discharge has accounted for 81%, with 63% of the freshwater flux originated from the Helheim glacier. This indicates that the Helheim outlet glacier plays a dominant role as a freshwater source to both Sermilik Fjord and ultimately the Irminger Sea. For the palaeorecords of the last 4000 years, simulated surface runoff has averaged 4.4±0.2×109 m3/yr. A very weak decreasing trend in runoff over the last 4 k years (1899 bc–ad 1980) is presumably associated with the general insolation-generated Northern Hemisphere cooling since the Holocene Thermal Maximum. Our simulations furthermore indicated centennial- to submillennial-scale variations in surface runoff concurrent with the well-known climate episodes such as the ‘Roman Warm Period’, the ‘Dark Ages Cold Period’, the ‘Medieval Climate Anomaly’, and the ‘Little Ice Age’. During the ‘Little Ice Age’, e.g., the average surface runoff was about 0.7×109 m3/yr lower than today, while the increase in runoff for the Modern Warming, since the late 1800s, was the second strongest and fastest for the last 4 k years.

Release of dissolved trace metals and organic contaminants during deep water disposal of contaminated sediments from Oslo harbour, Norway

Purpose The current study was conducted in order to assess the release of dissolved contaminants from sediment relocation works in Oslo harbour, Norway, whilst operations were being carried out, and to assess the potential for spreading into the wider fjord area.

Half a Century of Measurements of Glaciers on Axel Heiberg Island, Nunavut, Canada

We illustrate the value of longevity in high-latitude glaciological measurement series with results from a programme of research in the Expedition Fiord area of western Axel Heiberg Island that began in 1959. Diverse investi­gations in the decades that followed have focused on subjects such as glacier zonation, the thermal regime of the polythermal White Glacier, and the contrast in evolution of White Glacier (retreating) and the adjacent Thompson Glacier (advancing until recently). Mass-balance monitoring, initiated in 1959, continues to 2011. Measurement series such as these provide invaluable context for understanding climatic change at high northern latitudes, where in-situ information is sparse and lacks historical depth, and where warming is projected to be most pronounced.

Raman spectroscopic approach to analytical astrobiology: the detection of key geological and biomolecular markers in the search for life

The compilation of this Theme Issue of Philosophical Transactions of the Royal Society on the theme of Raman spectroscopic analysis of materials from extreme environments is timely for several reasons, perhaps the most significant of these being the realization in the last decade that this technique

Allochthonous subsidies of organic matter across a lake–river–fjord landscape in the Chilean Patagonia: Implications for marine zooplankton in inner fjord areas

Ecosystems can act as both sources and sinks of allochthonous nutrients and organic matter. In this sense, fjord ecosystems are a typical interface and buffer zone between freshwater systems, glaciated continents, and the coastal ocean. In order to evaluate the potential sources and composition of organic matter across fjord ecosystems, we characterized particulate organic matter along a lake–river–fjord corridor in the Chilean Patagonia using stable isotope (δ 13C) and lipid (fatty acid composition) biomarker analyses. Furthermore, estimates of zooplankton carbon ingestion rates and measurements of δ 13C and δ 15N in zooplankton (copepods) were used to evaluate the implications of allochthonous subsidies for copepods inhabiting inner fjord areas. Our results showed that riverine freshwater flows contributed an important amount of dissolved silicon but, scarce nitrate and phosphate to the brackish surface layer of the fjord ecosystem. Isotopic signatures of particulate organic matter from lakes and rivers were distinct from their counterparts in oceanic influenced stations. Terrestrial allochthonous sources could support around 68–86% of the particulate organic carbon in the river plume and glacier melting areas, whereas fatty acid concentrations were maximal in the surface waters of the Pascua and Baker river plumes. Estimates of carbon ingestion rates and δ 13C in copepods from the river plume areas indicated that terrestrial carbon could account for a significant percentage of the copepod body carbon (20–50%) during periods of food limitation. Particulate organic matter from the Pascua River showed a greater allochthonous contribution of terrigenous/vascular plant sources. Rivers may provide fjord ecosystems with allochthonous contributions from different sources because of the distinct vegetation coverage and land use along each river’s watershed. These observations have significant implications for the management of local riverine areas in the context of any human project that may modify terrestrial habitats as well as the productivity, food webs, and community structure of rivers, lakes, fjords, and the coastal ocean in the Chilean Patagonia.

Sources and distribution of organic matter in northern Patagonia fjords, Chile (∼44–47°S): A multi-tracer approach for carbon cycling assessment

We investigated the provenance of organic matter in the inner fjord area of northern Patagonia, Chile (∼44–47°S), by studying the elemental (organic carbon, total nitrogen), isotopic (δ 13C, δ 15N), and biomarker ( n-alkanoic acids from vascular plant waxes) composition of surface sediments as well as local marine and terrestrial organic matter. Average end-member values of N/C, δ 13C, and δ 15N from organic matter were 0.127±0.010, −19.8±0.3‰, and 9.9±0.5‰ for autochthonous (marine) sources and 0.040±0.018, −29.3±2.1‰, and 0.2±3.0‰ for allochthonous (terrestrial) sources. Using a mixing equation based on these two end-members, we calculated the relative contribution of marine and terrestrial organic carbon from the open ocean to the heads of fjords close to river outlets. The input of marine-derived organic carbon varied widely and accounted for 13–96% (average 61%) of the organic carbon pool of surface sediments. Integrated regional calculations for the inner fjord system of northern Patagonia covered in this study, which encompasses an area of ∼4280 km 2, suggest that carbon accumulation may account for between 2.3 and 7.8×10 4 ton C yr −1. This represents a storage capacity of marine-derived carbon between 1.8 and 6.2×10 4 ton yr −1, which corresponds to an assimilation rate of CO 2 by marine photosynthesis between 0.06 and 0.23×10 6 ton yr −1. This rate suggests that the entire fjord system of Patagonia, which covers an area of ∼240,000 km 2, may represent a potentially important region for the global burial of marine organic matter and the sequestration of atmospheric CO 2.

Temporal and spatial distribution of floating objects in coastal waters of central–southern Chile and Patagonian fjords

Floating objects are suggested to be the principal vector for the transport and dispersal of marine invertebrates with direct development as well as catalysts for carbon and nutrient recycling in accumulation areas. The first step in identifying the ecological relevance of floating objects in a specific area is to identify their spatio-temporal distribution. We evaluated the composition, abundance, distribution, and temporal variability of floating objects along the continental coast of central–southern Chile (33–42°S) and the Patagonian fjords (42–50°S) using ship surveys conducted in austral winter (July/August) and spring (November) of the years 2002–2005 and 2008. Potential sources of floating items were identified with the aid of publicly available databases and scientific reports. We found three main types of floating objects, namely floating marine debris (mainly plastic objects and Styrofoam), wood (trunks and branches), and floating kelps ( Macrocystis pyrifera and Durvillaea antarctica). Floating marine debris were abundant along most of the examined transects, with markedly lower abundances toward the southern fjord areas. Floating marine debris abundances generally corresponded to the distribution of human activities, and were highest in the Interior Sea of Chiloé, where aquaculture activities are intense. Floating wood appeared sporadically in the study area, often close to the main rivers. In accordance with seasonal river run-off, wood was more abundant along the continental coast in winter (rainy season) and in the Patagonian fjords during the spring surveys (snow melt). Densities of the two floating kelp species were similar along the continental coast, without a clear seasonal pattern. M. pyrifera densities increased towards the south, peaking in the Patagonian fjords, where it was dominant over D. antarctica. Densities of M. pyrifera in the Patagonian fjords were highest in spring. Correlation analyses between the abundances of floating objects and the distance to the nearest sources were generally non-significant, suggesting that post-supply processes affect the distribution of the floating objects in the study region. The identification of several major retention zones supports this idea. Accumulation areas of floating objects appear to be more common in the fjord zones. In general, the results underscore the abundance of floating objects throughout the study region and the fact that floating marine debris sources are mostly local, whereas floating algae may be dispersed over greater distances. Future studies should focus on the ecological role of floating objects in biota dispersal and nutrient cycling.

Baffin Bay Narwhal Population Distribution and Numbers: Aerial Surveys in the Canadian High Arctic, 2002–04

Aerial surveys of narwhals (Monodon monoceros) were conducted in the Canadian High Arctic during the month of August from 2002 to 2004. The surveys covered the waters of Barrow Strait, Prince Regent Inlet, the Gulf of Boothia, Admiralty Inlet, Eclipse Sound, and the eastern coast of Baffin Island, using systematic sampling methods. Fiords were flown along a single transect down the middle. Near-surface population estimates increased by 1.9 %– 8.7% when corrected for perception bias. The estimates were further increased by a factor of approximately 3, to account for individuals not seen because they were diving when the survey plane flew over (availability bias). These corrections resulted in estimates of 27 656 (SE = 14 939) for the Prince Regent and Gulf of Boothia area, 20 225 (SE = 7285) for the Eclipse Sound area, and 10 073 (SE = 3123) for the East Baffin Island fiord area. The estimate for the Admiralty Inlet area was 5362 (SE = 2681) but is thought to be biased. Surveys could not be done in other known areas of occupation, such as the waters of the Cumberland Peninsula of East Baffin, and channels farther west of the areas surveyed (Peel Sound, Viscount Melville Sound, Smith Sound and Jones Sound, and other channels of the Canadian Arctic archipelago). Despite these probable biases and the incomplete coverage, results of these surveys show that the summering range of narwhals in the Canadian High Arctic is vast. If narwhals are philopatri to their summering areas, as they appear to be, the total population of that range could number more than 60 000 animals. The largest numbers are in the western portion of their summer range, around Somerset Island, and also in the Eclipse Sound area. However, these survey estimates have large variances due to narwhal aggregation in some parts of the surveyed areas.

Observing the behavioral response of herring exposed to mid-frequency sonar signals.

There is general concern on how mid-frequency military sonars might affect aquatic animals. Approaches used to investigate possible effects on Norwegian spring spawning herring (Clupea harengus) are presented. Experiments were performed in a sheltered fjord area, in the open ocean, and in a net pen. In the fjord area, the behavior of the exposed herring was monitored using an upward-looking bottom-moored echo sounder. For the open ocean experiment, schools of exposed herring were tracked using omnidirectional sonar. In the controlled net-pen experiments, the herring were towed into a fjord basin. The net-pen was equipped with a horizontal pointing and an upward-looking split-beam echo sounder to monitor the behavior, a hydrophone to measure the exposure levels, and a video camera to verify the observed behavior. In all experiments the herring was exposed to relevant naval sonar signals using operational sources mounted on a research vessel or operated from a frigate. For the net-pen experiments, the herring were also exposed to other audible sound sources to investigate the robustness of the methodology to detect reaction patterns. The pros and cons of the different observational approaches are discussed. [Work supported by the Research Council of Norway Grant No. 184705.]

Distribution and diversity of polychaetes collected by trawling in Admiralty Bay: an Antarctic glacial fiord

The aim of the study is to determine patterns of distribution, species richness and diversity of polychaetes collected by trawling in Admiralty Bay. Forty-seven species of polychaetes were found in 75 samples collected in 1988 along a depth range from 15 to 500 m. Four polychaete assemblages were distinguished. The most diverse and peculiar assemblage was found in the deepest sublittoral of the central basin from ca. 300–500 m with main constant species Laetmonice producta, Sternaspis sp. and Thelepus cincinnatus. Shallow water assemblages had low diversity and species richness. The most common and eurytopic epifaunal polychaetes were Aglaophamus trissophyllus, Barrukia cristata, Harmothoe spp., Flabelligera mundata and Perkinsiana littoralis. The low species richness in shallow waters of Admiralty Bay is probably associated with depth, influence of glacial streams and suspended matter inflow which is particularly distinct in the shallow water fiord areas.

Pockmarks in the inner Oslofjord, Norway

Multibeam bathymetric surveys of the Inner Oslofjord, Norway have revealed a high density of pockmarks in the 179-km2 inner fjord area, which contains over 500 pockmarks of varying size, typically 20–50 m in diameter and 2–10 m deep. These pockmarks have been investigated with a variety of techniques, including acoustic subbottom profiling, sedimentological and geochemical analyses of cores, remotely operated vehicle observation, and morphometry. Both the distribution and shapes of the pockmarks suggest that they are related to structures in the bedrock underlying relatively thin (<50 m) unconsolidated glacial and postglacial sediments. The data provide no direct indication of a particular mode of pockmark formation, but release of large amounts of biogenic, shallow methane seems unlikely. Several lines of evidence point to a continuous process of pockmark formation followed by inactivity, with some pockmarks recently active whereas others have been inactive for a considerable time. Some pockmarks are characterised by coarse sediment in their centres. The density, variety and easy access make this pockmark field an ideal model area for pockmark research.

Late Holocene marine productivity changes in Northern Patagonia-Chile inferred from a multi-proxy analysis of Jacaf channel sediments

A multi-proxy approach based on organic (organic carbon, alkenones, and C/N) and inorganic geochemical proxies (biogenic opal, inorganic carbon, Fe, Ti, and Ca) preserved in the sediments of the Jacaf channel (CF7-PC33; 44°21′S, 72°58′W, 510 m water depth), Chilean fjords, yields evidence of major past productivity fluctuations in accordance with climatic changes over the last ∼1800 years. The downcore record clearly shows two productivity/climate modes. The first period, prior to 900 cal yr BP, is characterized by decreased marine productivity and a reduced continental signal, pointing to diminished precipitation and runoff. In contrast, the second period between ∼750 cal yr BP and the late 1800s (top of core) is illustrated by elevated productivity and an increased continental signal, suggesting higher precipitation and runoff. Both time intervals are separated by a relatively abrupt transition of ∼150 years which roughly coincides with the beginning of the Little Ice Age. The increased content of freshwater diatoms and Chrysophyte cysts that characterize the last 200 years of the latter mode coincides with a significant decrease in the carbonate content of the sediment; together they further indicate increased terrigenous contributions and decreased marine carbonate productivity at the end of the Little Ice Age. The correspondence between our record and other paleoclimate studies carried out in South America and Antarctica demonstrates that the Chilean fjord area of Northern Patagonia is not just sensitive to local climatic variability but also to regional and possibly global variability.

The invasive red alga Gracilaria vermiculophylla in the Baltic Sea: adaptation to brackish water may compensate for light limitation

The recent introduction of Gracilaria vermiculophylla (Rhodophyta) to the Kiel Fjord area was a reason for concern, since this red macroalga performs best under mesohaline conditions and thus appears well adapted to thrive and spread in the Baltic Sea environment, A systematic survey on a coastal range of 500 km in 2006 and 2007 indicated considerable Multiplication and spreading of G. vermiculophylla within Kiel Fjord, but provided little evidence of long-distance transport. Nonetheless, flow-through growth experiments conducted at a range of salinities under ambient light showed that G. vermiculophylla should be able to grow in most of the Baltic Sea. Growth declined only below a salinity of 5.5. High water temperatures in summer seem to reduce resistance against low salinity. Growth of G, vermiculophylla in the SW Baltic is limited by light and is only possible during summer and above a depth of 3 m. Drifting fragments are dispersed by currents. Either they sink to deeper waters, where they degrade, or they accumulate in shallow and sheltered waters, where they form perennial mats. These overgrow not only soft bottom sediments, but also stones, which are an important habitat to Fucus vesiculosus, the main native perennial alga in the Baltic Sea. As compared to F. vesiculosus, G. vermiculophylla seems to represent a preferred refuge for mesograzers and other invertebrates, particularly in winter. Nonetheless, feeding trials showed that potential grazers avoided G. vermiculophylla relative to F vesiculosus. Daily biomass uptake by grazers associated with G. vermiculophylla in nature did not exceed 2 g kg(-1) and is <11% of average daily net growth (18.5 g kg(-1)) in the first 2 m below sea level. Consequently, feeding may not be sufficient to control the spread of G. vermiculophylla in the SW Baltic. Our study suggests that absence of feeding enemies and adaptation to brackish water may allow G. vermiculophylla to invade most shallow coastal waters of the inner Baltic Sea despite light limitation.

Ecotoxicological sediment evaluations in marine aquaculture areas of Chile

Given its geographic characteristics, the southern Chilean fjord area is subjected to growing environmental pressure from the development of diverse forms of aquaculture (i.e., fish, algae, shellfish). The sediments accumulate substances as a natural sink, and ecotoxicology assays offer a reliable and robust proxy for sediment quality analyses. This study's objective was to establish a mid-range toxicity base line for the sediments in the region by applying a battery of non-specific ecotoxicological assays. Sediment samples (28) were collected in the channels and fjords studied during the CIMAR-Fiordos 11 cruise (July 2005). The sediments were evaluated using different species endemic to the eastern Pacific as targets: Ampelisca araucana, Tisbe longicornis, Arbacia spatuligera, and Dunaliella tertiolecta. The conditions for each assay were reported previously. Of the four species used as ecotoxicological tools, only D. tertiolecta differed significantly from the control group (negative) in terms of its growth. This difference could be attributed to nutrient enrichment. In general, we concluded that, although local changes occurred in the sediments, the mesoscale magnitude of the ecotoxicological alterations was small. Nonetheless, a surveillance program should be implemented that would allow us to follow-up and analyze the changes that are taking place in the systems on broader scales of time and space.

Lateglacial and Holocene terrestrial and marine proxies reflecting climate changes in the Malangen fjord area, Norway, northeast North Atlantic

A high‐resolution Younger Dryas–late Holocene record of climate and environment from the Malangen fjord has been established on the basis of two marine sediment cores. Five pollen‐spore assemblage zones have been defined covering the period c. 11 500 cal. yr BP (10 200 14C yr BP) to c. 1600 cal. yr BP (1600 14C yr BP) with a hiatus of c. 2000 cal. years between c. 10 200 and 8100 cal. yr BP (9000 and 7300 14C yr BP). The Holocene vegetation development from pioneer vegetation to forest development, identified in the marine pollen record, correlates well with pollen records from terrestrial sections of northern Norway. The marine pollen record was also correlated directly with marine proxy records of the bottom water temperature investigated in the same sediment cores. Correlation between the marine and terrestrial proxies suggests that changes in the influx of warm Atlantic Water to the fjord led to an instant change in the vegetation of the surrounding land area. The results thus support a strong link between marine and atmospheric mean climatic states in the North Atlantic region throughout the Holocene.

Trophic model of a lightly exploited cod-dominated ecosystem

A 27 compartment model of the food-web in Sørfjord, northern Norway was balanced using the mass-balance model Ecopath based on data from Sørfjord and adjacent fjord areas. Sørfjord is a lightly exploited high-latitude fjord ecosystem with cod as the main piscivore. During 1993–1996, the biomass of planktivore fish was low, and the pelagic community in the model was dominated by herbivore zooplankton, mainly copepods and krill, chaetognaths and microzooplankton. Carbon flows were dominated by the pelagic lower trophic level groups and the components of the microbial food-web. Flows originating from detritus amounted to 53% of the total carbon flow. The model benthic community was dominated by detrivores, with benthic invertebrate predators as important secondary consumers. Model output values for the benthic groups were sensitive to the input values of the cod and other fish groups. Macroalgae constituted a major part of the living biomass and was an important source for detritus, but did not provide a major input to herbivores. Cod, phytoplankton and krill were the major keystone groups and had large trophic impacts on the other groups. Herbivorous krill constituted much (>50%) of the cod diet, resulting in a low trophic level (TL = 3.6) of cod in Sørfjord compared to TL of cod in other ecosystems ranging from 3.7 to 4.4. Cod biomass, production and yield were relatively high compared to other boreal and high-latitude ecosystems with cod populations. Model transfer efficiencies averaged 21.7% from trophic levels II–IV. The low level of exploitation may enhance long-lived benthic groups that not only directly support higher trophic levels but also contribute to a broad food base that supports a relatively high production of cod.

Separation of Norwegian coastal cod and Northeast Arctic cod by outer otolith shape analysis

For stock assessment purposes, Atlantic cod ( Gadus morhua) from the coastal and offshore regions off northern Norway is usually allocated to Norwegian coastal cod (NCC) or Northeast Arctic cod (NEAC) by internal morphological features of their otoliths. As this classification is subject to individual interpretation by otolith age readers, this study investigated an alternative objective approach for the separation of the two cod groups, using otolith shape analysis. Several hundred otolith samples from coastal fjord areas along northern Norway and from the Barents Sea were analysed by univariate shape descriptors and elliptical Fourier analysis (EFA). When combining uni- and multivariate descriptors and applying the otolith reader typing as reference, the classification score was 89% for NCC and 90% for NEAC. These results indicate that the internal morphology of the otoliths, evaluated by the age readers, is translated to a great extent to their outer morphology and that otoliths can be allocated to NCC and NEAC by their shapes with high certainty. When genetic typing data ( Pan I marker) were used as reference, the classification scores were reduced to 83% for NCC and 76% for NEAC when combining uni- and multivariate descriptors and excluding heterozygotes. This implies that differences in otolith morphology cannot directly be linked to genetic structure. Differences in environmental conditions, however, seem to have a considerable influence on how otolith growth increments and consequently otolith shapes are formed. As the various fjord systems in Norway provide local habitats and as differences within the NCC with regard to genetic structure and life-history parameters had been found in earlier studies, variation of NCC otolith shapes between three coastal regions was also examined. The region classification scores for reader-typed NCC varied between 60% and 81%.

Loch Burn Formation, Fiordland, New Zealand: SHRIMP U‐Pb ages, geochemistry and provenance

New SHRIMP U‐Pb ages and geochemical data have been obtained for the volcano‐sedimentary Loch Burn Formation (LBF). A rhyolitic clast from the tops of the Stuart Mountains gave a SHRIMP age of 150.3 ± 1.9 Ma, and a very fine sandstone from the same area was dominated by 147.9 ±2.1 Ma zircons. These ages imply a <148 Ma depositional age for the LBF in this area, in contrast to a previous 195‐1 +3Ma age determination for an intercalated felsic flow in the North Fiord area, c. 1 km distant. Two tonalitic clasts from Cumbrae Island gave ages of 354.6 ± 2.6 and 326.8 ±3.2 Ma, respectively. The c. 47 m.y. difference between depositional ages in the Stuart Mountains and North Fiord indicates that the LBF as currently mapped includes more than one unit. however, volcanic clasts and lavas from the two areas are indistinguishable in terms of major and trace element geochemistry, and there is currently insufficient information to discriminate between the two units. informal units are therefore proposed: the < 148 Ma LBF‐2 unit and the c. 195 Ma LBF‐1 unit. volcanic clasts and lavas from both units are probably derived from the Darran Suite arc. The c. 327 Ma tonalite clast has moderate Zr/TiO2 and chemistry similar to most of the other LBF tonalite samples, whereas the c. 355 Ma tonalitic clast has unusual, very high Zr chemistry. Neither appear to be related to any New Zealand plutonics currently well characterised in the literature, based on differences in major and trace element chemistry. however, recent work indicates that possible correlatives with appropriate age and geochemistry exist for both groups of tonalites. No Western Province material is recorded in any of the LBF samples, but this is not considered to exclude formation adjacent to or within the gondwana margin.