Overview of bedrock mapping in the northern and western parts of the Tehery Lake-Wager Bay area, western Hudson Bay, Nunavut

Bedrock-geology mapping was conducted in the summer of 2016 in the Tehery Lake–Wager Bay area on the northwestern coast of Hudson Bay, Nunavut, as part of a multiyear, multidisciplinary mapping campaign led by the Geological Survey of Canada, through Phase 2 of the Geo-mapping for Energy a nd Minerals program (GEM-2), and the Canada-Nunavut Geoscience Office. Fieldwork resulted in the identification and spatial constraint of rock units in the northern and western parts of the study area, which were sampled for geochemical, g eochronological and petrographic analysis, as well as to as- sess their economic potential. Mapping has revealed the presence of a large granulite-facies metamorphic domain in the southern part of the study area; the possibility of two different supracrustal rock sequences; the western continuations of the Chesterfield fault zone and Wager shear zone; and generally high, but locally variable, peak metamorphic conditions across the study area. Further analytical work is required to fully characterize rock units, compare and correlate them with other well-studied units, and determine the geological history and economic potential of the Tehery Lake–Wager Bay area

A high-density transcript linkage map with 1,845 expressed genes positioned by microarray-based Single Feature Polymorphisms (SFP) in Eucalyptus

<p>Abstract</p> <p>Background</p> <p>Technological advances are progressively increasing the application of genomics to a wider array of economically and ecologically important species. High-density maps enriched for transcribed genes facilitate the discovery of connections between genes and phenotypes. We report the construction of a high-density linkage map of expressed genes for the heterozygous genome of <it>Eucalyptus </it>using Single Feature Polymorphism (SFP) markers.</p> <p>Results</p> <p>SFP discovery and mapping was achieved using pseudo-testcross screening and selective mapping to simultaneously optimize linkage mapping and microarray costs. SFP genotyping was carried out by hybridizing complementary RNA prepared from 4.5 year-old trees xylem to an SFP array containing 103,000 25-mer oligonucleotide probes representing 20,726 unigenes derived from a modest size expressed sequence tags collection. An SFP-mapping microarray with 43,777 selected candidate SFP probes representing 15,698 genes was subsequently designed and used to genotype SFPs in a larger subset of the segregating population drawn by selective mapping. A total of 1,845 genes were mapped, with 884 of them ordered with high likelihood support on a framework map anchored to 180 microsatellites with average density of 1.2 cM. Using more probes per unigene increased by two-fold the likelihood of detecting segregating SFPs eventually resulting in more genes mapped. <it>In silico </it>validation showed that 87% of the SFPs map to the expected location on the 4.5X draft sequence of the <it>Eucalyptus grandis </it>genome.</p> <p>Conclusions</p> <p>The <it>Eucalyptus </it>1,845 gene map is the most highly enriched map for transcriptional information for any forest tree species to date. It represents a major improvement on the number of genes previously positioned on <it>Eucalyptus </it>maps and provides an initial glimpse at the gene space for this global tree genome. A general protocol is proposed to build high-density transcript linkage maps in less characterized plant species by SFP genotyping with a concurrent objective of reducing microarray costs. HIgh-density gene-rich maps represent a powerful resource to assist gene discovery endeavors when used in combination with QTL and association mapping and should be especially valuable to assist the assembly of reference genome sequences soon to come for several plant and animal species.</p

Candidate chemoreceptor subfamilies differentially expressed in the chemosensory organs of the mollusc Aplysia

<p>Abstract</p> <p>Background</p> <p>Marine molluscs, as is the case with most aquatic animals, rely heavily on olfactory cues for survival. In the mollusc <it>Aplysia californica</it>, mate-attraction is mediated by a blend of water-borne protein pheromones that are detected by sensory structures called rhinophores. The expression of G protein and phospholipase C signaling molecules in this organ is consistent with chemosensory detection being via a G-protein-coupled signaling mechanism.</p> <p>Results</p> <p>Here we show that novel multi-transmembrane proteins with similarity to rhodopsin G-protein coupled receptors are expressed in sensory epithelia microdissected from the <it>Aplysia </it>rhinophore. Analysis of the <it>A. californica </it>genome reveals that these are part of larger multigene families that possess features found in metazoan chemosensory receptor families (that is, these families chiefly consist of single exon genes that are clustered in the genome). Phylogenetic analyses show that the novel <it>Aplysia </it>G-protein coupled receptor-like proteins represent three distinct monophyletic subfamilies. Representatives of each subfamily are restricted to or differentially expressed in the rhinophore and oral tentacles, suggesting that they encode functional chemoreceptors and that these olfactory organs sense different chemicals. Those expressed in rhinophores may sense water-borne pheromones. Secondary signaling component proteins Gα_q, Gα_i, and Gα_oare also expressed in the rhinophore sensory epithelium.</p> <p>Conclusion</p> <p>The novel rhodopsin G-protein coupled receptor-like gene subfamilies identified here do not have closely related identifiable orthologs in other metazoans, suggesting that they arose by a lineage-specific expansion as has been observed in chemosensory receptor families in other bilaterians. These candidate chemosensory receptors are expressed and often restricted to rhinophores and oral tentacles, lending support to the notion that water-borne chemical detection in <it>Aplysia </it>involves species- or lineage-specific families of chemosensory receptors.</p

Trans-Hudson Orogen of North America and Himalaya-Karakoram-Tibetan Orogen of Asia: Structural and thermal characteristics of the lower and upper plates

The Trans-Hudson Orogen (THO) of North America and the Himalaya-Karakoram- Tibetan Orogen (HKTO) of Asia preserve a Paleoproterozoic and Cenozoic record, respectively, of continent-continent collision that is notably similar in scale, duration and character. In THO, the tectonothermal evolution of the lower plate involves (1) early thin-skinned thrusting and Harrovian metamorphism, (2) out-of-sequence thrusting and high-T metamorphism, and (3) fluid-localized reequilibration, anatexis, and leucogranite formation. The crustal evolution of the Indian lower plate in HKTO involves (1) early subduction of continental crust to ultrahigh pressure (UHP) eclogite depths, (2) regional Barrovian metamorphism, and (3) widespread high-T metamorphism, anatexis, and leucogranite formation. The shallow depths of the high-T metamorphism in HKTO are consistent with early to mid-Miocene ductile flow of an Indian lower plate midcrustal channel, from beneath the southern Tibetan Plateau to the Greater Himalaya. Melt weakening of the lower plate in THO is not observed at a similar scale probably due to the paucity of pelitic lithologies. Tectonothermal events in the upper plate of both orogens include precollisional accretion of crustal blocks, emplacement of Andean-type plutonic suites, and high-T metamorphism. Syncollisional to postcollisional events include emplacement of garnet-biotite-muscovite leucogranites, anatectic granites, and sporadic metamorphism (up to 90 Myr following the onset of collision in THO). Comparing the type and duration of tectonothermal events for THO and HKTO supports the notion of tectonic uniformitarianism for at least the later half of dated Earth history and highlights the complementary nature of the rock record in an older "exhumed" orogen compared to one undergoing present-day orogenesis. Copyright 2006 by the American Geophysical Union

Archean and Paleoproterozoic cratonic rocks of Baffin Island

Archean and Paleoproterozoic cratonic rocks of Baffin Island define four stacked structural levels that are juxtaposed within the middle Paleoproterozoic Trans-Hudson Orogen. From north to south, and highest to lowest structural level, these comprise:1) the Archean Rae Craton, unconformably overlain along its southern margin by middle Paleoproterozoic supracrustal cover (Piling Group) and stratigraphically similar units of the Hoare Bay Group on Cumberland Peninsula; 2) Archean to middle Paleoproterozoic metaplutonic units and middle Paleoproterozoic metasedimentary cover (Lake Harbour Group), collectively termed the 'Meta Incognita microcontinent'; 3) middle Paleoproterozoic orthogneiss, interpreted as a deformed arc-magmatic terrane (Narsajuaq terrane) or alternatively as Narsajuaq-age intrusions emplaced in the Meta Incognita microcontinent; and 4) Archean orthogneiss, interpreted as the northern continuation of the lower-plate Superior Craton, and associated middle Paleoproterozoic continental-margin supracrustal cover (Povungnituk Group).</jats:p

Bedrock geology, Ravn River, Baffin Island, Nunavut, NTS 37-G east 1:100,000 Map

This map presents the field observations and initial geological interpretations for the Ravn River area (NTS 37-G east) Baffin Island, Nunavut. The regional bedrock geology depicted on CGM maps 402 to 406 comprises Archean tonalitic to monzogranitic gneiss that includes mafic to intermediate components, and relatively homogeneous monzogranite-granodiorite intrusions. The Archean Mary River Group forms discontinuous volcano-sedimentary belts, consisting of mafic volcanic rocks interlayered with siliciclastic strata, banded iron-formation, and felsic to intermediate and ultramafic volcanic units. The supracrustal rocks are intruded by monzogranite-granodiorite plutons. Pelitic to psammitic units, marble, and calc-silicate of the middle Paleoproterozoic Piling Group unconformably overlie the Archean units. Archean units are also unconformably overlain by Mesoproterozoic clastic and carbonate platform sequences of the Bylot Supergroup. These strata were deposited within a graben that forms part of the larger Borden Basin. Paleozoic (Cambrian to Ordovician) strata lie unconformably upon Archean and Paleoproterozoic felsic plutonic rocks in the western portion of northern Baffin Island

Archean and Paleoproterozoic cratonic rocks of Baffin Island

Archean and Paleoproterozoic cratonic rocks of Baffin Island define four stacked structural levels that are juxtaposed within the middle Paleoproterozoic Trans-Hudson Orogen. From north to south, and highest to lowest structural level, these comprise:1) the Archean Rae Craton, unconformably overlain along its southern margin by middle Paleoproterozoic supracrustal cover (Piling Group) and stratigraphically similar units of the Hoare Bay Group on Cumberland Peninsula; 2) Archean to middle Paleoproterozoic metaplutonic units and middle Paleoproterozoic metasedimentary cover (Lake Harbour Group), collectively termed the 'Meta Incognita microcontinent'; 3) middle Paleoproterozoic orthogneiss, interpreted as a deformed arc-magmatic terrane (Narsajuaq terrane) or alternatively as Narsajuaq-age intrusions emplaced in the Meta Incognita microcontinent; and 4) Archean orthogneiss, interpreted as the northern continuation of the lower-plate Superior Craton, and associated middle Paleoproterozoic continental-margin supracrustal cover (Povungnituk Group)

Bedrock geology, Angijurjuk-Mary River, Baffin Island, Nunavut, NTS 37-G west 1:100,000 Map

This map presents the field observations and initial geological interpretations for the Angijurjuk-Mary River area (NTS 37-G west), Baffin Island, Nunavut. The regional bedrock geology depicted on CGM maps 402 to 406 comprises Archean tonalitic to monzogranitic gneiss that includes mafic to intermediate components, and relatively homogeneous monzogranite-granodiorite intrusions. The Archean Mary River Group forms discontinuous volcano-sedimentary belts, consisting of mafic volcanic rocks interlayered with siliciclastic strata, banded iron-formation, and felsic to intermediate and ultramafic volcanic units. The supracrustal rocks are intruded by monzogranite-granodiorite plutons. Pelitic to psammitic units, marble, and calc-silicate of the middle Paleoproterozoic Piling Group unconformably overlie the Archean units. Archean units are also unconformably overlain by Mesoproterozoic clastic and carbonate platform sequences of the Bylot Supergroup. These strata were deposited within a graben that forms part of the larger Borden Basin. Paleozoic (Cambrian to Ordovician) strata lie unconformably upon Archean and Paleoproterozoic felsic plutonic rocks in the western portion of northern Baffin Island