With the aim of better understanding the history of ocean closure and suturing between India and Asia, we conducted a geologic investigation of a siliciclastic matrix tectonic melange within the western Yarlung suture zone of southern Tibet (Lopu Range region, similar to 50 km northwest of Saga). The siliciclastic matrix melange includes abundant blocks of ocean plate stratigraphy and sparse blocks of sandstone. Metapelite and metabasite blocks in the melange exhibit lower greenschist fades mineral assemblages, indicating that they were not deeply subducted. We obtained detrital zircon U-Pb geochronologic and sandstone petrographic data from sandstone blocks in the melange and sandstone beds from Tethyan Himalayan strata exposed to the south of the suture. The sandstones from both units are all similar in U-Pb detrital zircon age spectra and petrography to the nearby Tethyan Cretaceous-Paleocene Sangdanlin section, which records the earliest appearance (at similar to 59 Ma) of arc-affinity strata deposited conformably on Indian-affinity strata. Two Paleocene sandstones, one of which is a schistose block incorporated in the siliciclastic matrix melange, yielded indistinguishable maximum depositional ages of similar to 59 Ma. Mesozoic Asian-affinity sandstone blocks previously documented in the siliciclastic matrix melange 200-500 km along strike to the east are notably absent in the Lopu Range region. We documented a gradational transition in structural style from the block-in-matrix melange in the northeast to the south-vergent Tethyan thrust belt in the southwest. Blocks of Tethyan Himalayan strata increase in size and the volumetric proportion of matrix decreases from northeast to southwest. We conclude that no arc-affinity sandstone blocks were incorporated into the subduction complex until India-Asia collision at similar to 59 Ma when the Xigaze forearc basin became overfilled and Tethyan Himalayan strata entered the trench. As collision progressed, there was a gradual transition in structural style from block-in-matrix melange formation to imbricate-style thrust belt formation. (C) 2017 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

The Eldivan ophiolite, in the Ankara Mélange, represents the remnant of an ocean basin that developed in the İzmir-Ankara-Erzincan Ocean and collapsed the form the İzmir -Ankara-Erzincan suture zone (İAESZ) through continental block collision. Whole-rock and mineral geochemical evidence show supra-subduction zone tectonomagmatic affinity for the ophiolite, revealing this basin formed in the upper plate of an intra-oceanic subduction zone. Detrital zircon from the ophiolitic mélange sandstone and the overlying Karadağ Formation suggest the ophiolites maximum age is 143.2 (±2) Ma, and the overlying Karadağ Formation is 105.2 (±5) Ma. The angular unconformity between the ophiolite and Karadağ formation reveal that the Eldivan ophiolite was imbricated between 105.2 (±5) Ma and 143.2 (±2) Ma. Petrographic analysis of sandstone from the ophiolitic mélange reveals a source terrain of a volcanic arc rather than a continental source. Structural restoration of the sheeted dike complex reveals the back or intra-arc spreading ridge of the Eldivan ophiolite as NE-SW, oblique to the Sakarya-Pontide continental margin. Three phases of evolution for the Eldivan ophiolite are constrained by complied age data: a constructional, destructional, and suturing phase. The evolution is similar the Philippine Sea Plate and Mariana Trough and fits well within the framework of other eastern Mediterranean Tethyan ophiolites.

Thesis advisor: Seth C. Kruckenberg / The Potters Pond migmatite domain (PPMD) is a heterogeneous zone of migmatites located ~10 km southwest of Cascade, Idaho within the western Idaho shear zone (WISZ). The PPMD is the only known exposure of migmatites within the WISZ over its ~300 km length, occurring where the shear zone orientation changes from 020° south to 000° north of the migmatite domain. Structural mapping within the PPMD has identified multiple generations of migmatite with varied structural fabrics. Leucosome layers were sampled from distinct migmatite localities and morphologies (e.g., metatexite, diatexite) to determine the timing and duration of partial melting in the PPMD. U-Pb age determinations of zircon by means of LA-ICP-MS document two periods of protracted migmatite crystallization during the Early and Late Cretaceous. Early Cretaceous (ca. 145 to 128 Ma) migmatite crystallization ages are coeval with the collision and suturing of oceanic terranes of the Blue Mountains province with North America, and the formation of the Salmon River suture zone (SRSZ). Migmatite crystallization ages from ca. 104 to 90 Ma are associated with Late Cretaceous dextral transpression in the WISZ. Field observations and geochronology of cross cutting leucosome relationships are interpreted to record deep crustal deformation and anatexis associated with formation of the SRSZ, subsequently overprinted by solid-state deformation and renewed anatexis during the evolution of the WISZ. These data are the first direct evidence of the synmetamorphic fabric related to the SRSZ east of the initial Sr 0.706 isopleth, and that the WISZ is a temporally distinct overprinting structure. / Thesis (MS) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Black grouse (Tetrao tetrix) is a bird species with a lek mating system found in the Palearctic boreal taiga. It is assumed that it has a continuous distribution along Scandinavia and Siberia, whereas in Central Europe it has declined during the last decades. The primary objective of this thesis was to obtain a deeper understanding of the history, systematic classification and the genetic structure of black grouse on different geographical scales using microsatellites and control region mtDNA sequences (CR). I determined how much the mating system, habitat fragmentation and historical population processes have influenced the partitioning of genetic diversity in this species. Phylogeographical results are consistent with a demographic population expansion, and the patterns of postglacial dispersal suggest that a glacial refugium was located somewhere in central Asia, and from there black grouse spread out to Europe following the retreat of glacial ice sheets. I suggest that the two European black grouse subspecies, T. t. Tetrix and T. t. britannicus correspond to only one subspecies: T. t. tetrix, and that this lineage has diverged from T.t. viridanus, a subspecies found in Kazakhstan. The British population is significantly divergent from the remaining Eurasian samples for microsatellites but it is not for mtDNA. Therefore, they should regard as a separate Management Unit and not as a subspecies. Furthermore, British black grouse occur in three independent genetic units, corresponding to Wales, northern England/southern Scotland and northern Scotland. There was also genetic structure within Sweden. Habitat fragmentation is the main cause of population genetic structure in southern Swedish black grouse. In contrast, low levels of genetic differentiation and high connectivity were found in northern Sweden due to female-biased dispersal. On a finer geographical scale, I found genetic differences between leks due to a mixture of related and unrelated individuals within leks. However, mean relatedness values hardly differed from zero. Some leks were similar to one another and I interpret this as a result of variation in local reproductive success and philopatry. These factors would cause genetic structuring but this by itself would not reveal that kin selection is operating within black grouse leks.

The structural lineament mapping of southern India along withgeological, geochronological datasets help in redefining the Precambrian crustal blocks.The newly proposed Kumta and Mercara suture zones welding Archean crustal blocks in western peninsular India offer critical insights into the crustal evolution of Gondwana. The Kumta suturemainly consists of schistose rocks including quartz-phengite, garnet-biotite, chlorite, fuchsite and marble, whereas the Mercara suture contains mylonitic quartzo-feldspathic gneiss, garnet-kyanite-sillimanite gneiss, calc-silicate granulite and metagabbro. Metamorphic pressure-temperature estimations (Kumta suture: 11-18 kbar at 790-550oC; Mercara suture: 13 kbar at 825oC) suggest that, the sediments have undergone subduction to greater depths. The K-Ar age of biotite, phengite and U-Pb dating of zircon yields consistent metamorphic age of 1100-1400 Ma. In situ zircon 176Lu/177Hf isotope analysis shows wide range of εHf (t) values indicating the protolith sediments were derived from Paleo-Neoarchean juvenile crust that mixed with recycled older crust. The Bondla ultramafic-gabbro complex, northwest of the Kumta suture contains basalt, dolerite, gabbro, serpentinite, chromitite, peridotite and chromian spinel chemistry suggests evolution in a supra-subduction zone arc tectonic setting.The Sirsi shelf towards east of the Kumta suture, contains weakly deformed sedimentary rocks (limestone, shale, banded iron formations, greywacke, sandstone and quartzite) unconformable on relatively high-grade ca. 2571 Ma gneisses of the Dharwar craton. The Karwar block to the west is composed of weakly metamorphosedca. 3200 Ma tonalite-trondhjemite-granodiorite (TTG) with enclaves of amphibolite. In situ zircon 176Lu/177Hf isotope analysis and whole-rock 143Nd/144Nd isotopic analysis of TTGs show positive εHf and εNd values indicating ca. 3200 Ma juvenile crust. The Coorg block consists of ca. 3200 Ma charnockite, mafic granulites, hornblende-biotite gneiss, garnet-hornblende gabbro and anorthosite.In situ zircon 176Lu/177Hf isotope analysis indicates source as mixture of juvenile crust and older recycled crustal materials. Synthesis of the above results with published data suggests that Kumta and Mercara suture zones incorporate Paleoarchean to Mesoproterozoic sedimentssubjected to high-pressure metamorphism in the late Mesoproterozoic. Metamorphic P-T estimations of mafic granulite and U-Pb zircon geochronology of pelitic gneisses from Betsimisaraka suture zone, Madagascar suggests the rocks were underwent metamorphism at c. 24 kbar and c. 780°C during Mesoproterozoic suturing of Antongil-Masora blocks with the Antananarivo block.From the integration of above results with the new geophysical results and published data Mesoproterozoic Kumta-Mercara suture is interpreted as eastern extension of the Mesoproterozoic Betsimisaraka suture of Madagascar into western India.