Comment on: “New” lunar meteorites: Impact melt and regolith breccias and large‐scale heterogeneities of the upper lunar crust,by P. H. Warren,F. Ulff‐Møller,and G. W. Kallemeyn

Abstract We described lunar meteorite Dhofar 026 (Cohen et al. 2004) and interpreted this rock as a strongly shocked granulitic breccia (or fragmental breccia consisting almost entirely of granulitic‐breccia clasts) that was partially melted by post‐shock heating. Warren et al. (2005) objected to many aspects of our interpretation: they were uncertain whether or not the bulk rock had been shocked; they disputed our identification of the precursor as granulitic breccia; and they suggested that mafic, igneous‐textured globules within the breccia, which we proposed were melted by post‐shock heating, are clasts with relict textures. The major evidence for shock of the bulk rock is the fact that the plagioclase in the lithologic domains that make up 80–90% of the rock is devitrified maskelynite. The major evidence for a granulitic‐breccia precursor is the texture of the olivine‐plagioclase domain that constitutes 40—45% of the rock; Warren et al. apparently overlooked or ignored this lithology. Textures of the mafic, igneous‐textured globules, and especially of the vesicles they contain, demonstrate that these bodies were melted and crystallized in situ. Warren et al. suggested that the rock might have originally been a regolith breccia, but the textural homogeneity of the rock and the absence of solar wind—derived noble gases preclude a regolith‐breccia precursor. Warren et al. classified the rock as an impact‐melt breccia, but they did not identify any fraction that was impact melt.     

Lipid composition of phytoplankton from the Barents Sea and environmental influences on the distribution pattern of carbon among photosynthetic end products

The colonial algae Phaeocystis pouchetii and Dinobryon pellucidum dominated the phytoplankton crop at three stations in the Polar Front area of the Barents Sea.
Lipid extracted from the seawater containing the phytoplankton was dominated by neutral lipid classes, particularly triacylglycerols, and phospholipids were more abundant than galactolipids at all stations. Polyunsaturated fatty acids comprised between 15 and 26% of fatty acids of total lipid.
Of the carbon assimilated into lipid over 24 hours, 40% was located in the neutral lipid fraction. Phospholipids contained a smaller proportion of fixed carbon than galactolipids.
No defiinte relationships were observed between the distribution of fixed carbon in photosynthetic end products and the temperature or irradiance at which the phytoplankton was incubated. At a constant irradiance of 8.5 μmol m⁻²s⁻¹, the highest proportion of fixed carbon was recovered in protein at 4.5°C, but at −1.5°C most radioactivity was present in low molecular weight compounds. Regardless of incubation conditions, lipid always contained less than 30% of total assimilated carbon.     

Continental/Cordilleran ice interactions: a dominant cause of westward super-elevation of the last glacial maximum continental ice limit in southwestern Alberta, Canada

In southwestern Alberta, Canada, a westward-rising last-glacial-maximum continental ice limit has been identified. This limit is defined by the upper elevation of Canadian Shield erratics deposited by last-glacial-maximum continental ice along the flanks of prominent ridges and buttes within the region. The interpolation between ice-limit data points has produced two distinct slope profiles: 2.9 m/km to the east, and 4.2 m/km to the west of Mokowan Butte. Three hypotheses are proposed to explain this westward rise of the last-glacial-maximum continental ice limit: (1) regional tectonic uplift, (2) glacio-isostatic uplift, and (3) continental ice-flow convergence due to topographic obstacles and interaction with montane ice. Inferred long-term rates of tectonic uplift and glacio-isostatic modelling show that these two mechanisms account for less than 25% of the observed absolute elevation increase of the limit between the Del Bonita uplands and Cloudy Ridge in southwestern Alberta. The remaining rise in elevation of the continental ice-sheet margin in this region is thought to result from continental ice-flow convergence due to the combined effects of the regional topography and interaction with montane glaciers to the west. The steeper rise in the former continental ice surface west of Mokowan Butte can be explained by the topographic obstruction and interaction with montane glaciers in the area of the Rocky Mountain front.     

EVIDENCE FOR EXPANDED MIDDLE AND LATE PLEISTOCENE GLACIER EXTENT IN NORTHWEST NELSON,NEW ZEALAND

The extent of Late Quaternary glaciation in the northwest Nelson region of New Zealand has traditionally been regarded as minor, with small‐scale valley glaciation in confined upland reaches. New geomorphological evidence, including moraines, kame terraces, till‐mantled bedrock and outwash terraces, indicate that greatly expanded valley glaciers flowed into the lowland valley system at the mouths of the Cobb‐Takaka and Anatoki drainages. The timing for this ice advance into lowland valleys is constrained by lowland landform characteristics and a single cosmogenic exposure age, suggesting Late and Middle Pleistocene ice expansion, respectively. Evidence for expanded upland ice on the Mount Arthur Tableland and adjacent areas includes trimlines, boulder trains and roche moutonées. Two cosmogenic exposure ages on upland bedrock surfaces suggest that major ice expansion occurred during MIS 3 and/or 4, while previously published exposure dating from Cobb Valley suggests large MIS 2 ice expansion as well. The inferred, markedly expanded ice left little or no clear geomorphic imprint on the Cobb–Takaka Gorge, and required temperature depression of 4–6°C with near‐modern precipitation levels.     

Carbonates within a Pleistocene glaciomarine succession, Yakataga Formation, Middleton Island, Alaska

Uplifted during the 1964 Alaskan earthquake, extensive intertidal flats around Middleton Island expose 1300 m of late Cenozoic (Early Pleistocene) Yakataga Formation glaciomarine sediments. These outcrops provide a unique window into outer shelf and upper slope strata that are otherwise buried within the south‐east Alaska continental shelf prism. The rocks consist of five principal facies in descending order of thickness: (i) extensive pebbly mudstone diamictite containing sparse marine fossils; (ii) proglacial submarine channel conglomerates; (iii) burrowed mudstones with discrete dropstone layers; (iv) boulder pavements whose upper surfaces are truncated, faceted and striated by ice; and (v) carbonates rich in molluscs, bryozoans and brachiopods. The carbonates are decimetre scale in thickness, typically channellized conglomeratic event beds interpreted as resedimented deposits on the palaeoshelf edge and upper slope. Biogenic components originated in a moderately shallow (ca 80 m), relatively sediment‐free, mesotrophic, sub‐photic setting. These components are a mixture of parautochthonous large pectenids or smaller brachiopods with locally important serpulid worm tubes and robust gastropods augmented by sand‐size bryozoan and echinoderm fragments. Ice‐rafted debris is present throughout these cold‐water carbonates that are thought to have formed during glacial periods of lowered sea‐level that allowed coastal ice margins to advance near to the shelf edge. Such carbonates were then stranded during subsequent sea‐level rise. Productivity was enabled by attenuation of terrigenous mud deposition during these cold periods via reduced sedimentation together with active wave and tidal‐current winnowing near the ice front. Redeposition was the result of intense storms and possibly tsunamis. These sub‐arctic mixed siliciclastic‐carbonate sediments are an end‐member of the Phanerozoic global carbonate depositional realm whose skeletal attributes first appeared during late Palaeozoic southern hemisphere deglaciation.     

Discrete lithofacies discrimination of Jurassic strata using Advanced Spaceborne Thermal Emission and Reflection Radiometer Data, Bighorn Basin, Wyoming, USA

An investigation of the carbonate sedimentology of the Middle Jurassic strata, Bighorn Basin, North-central Wyoming, proved to be an ideal test of new spaceborne remote sensing platforms with high spatial and spectral resolution. To evaluate these new tools, it was necessary to: (i) map the occurrence of different lithofacies in at least a part of the area to establish ground truth; (ii) establish the reflectance characteristics of the different lithofacies using portable, on the ground, systems; (iii) produce maps based on spaceborne remote sensing data that discriminate between the lithological types found in the field; and, lastly, (iv) evaluate the discrimination by visiting previously unvisited areas in which these rock types are predicted to occur based upon their remote signatures. Field checking of previously unvisited outcrops demonstrated whether these remote sensing techniques allowed distinction of different lithological outcrops. This investigation determined that the new spaceborne tools could distinguish between outcrops of sparse silty oomicrites from sorted biosparites as small as 10 m by 10 m. In a study area as large as the Bighorn Basin, the ability to identify very small outcrops with a predicted lithology a priori proved to be a major advantage in maximizing field effort.