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Subaerial rise of Earth's first continents took place 3.3–3.2 Ga years ago. This had significant influence on the ocean, atmosphere, and biosphere. Two important sedimentological consequences of continental emersion were (1) development of terrestrial (alluvial fan–fluvial–aeolian) depositional systems and (2) formation of shallow-marine sedimentary basins near the continental margin. Late Paleoarchean–Neoarchean terrestrial deposits, including development of an extensive paleosol around 3.2 Ga, and Meso–Neoarchean shallow-marine deposits have been reported from the Singhbhum Craton, eastern India from several localities. However, lateral and vertical changes in sedimentary facies associations and stratigraphic correlation between these terrestrial to shallow-marine sedimentary deposits have not yet been investigated. In this paper, we have reviewed the sedimentological characteristics of Late Paleoarchean to Neoarchean (3.2–2.8 Ga) stratigraphic successions of the Singhbhum Craton and have discussed sea level change and mode of stratigraphic sequence building. Our analysis shows that Singhbhum granitoid complex was emplaced around 3.3 Ga in an intracontinental setting, resulting in high continental freeboard conditions that triggered terrestrial (alluvial fan–braided fluvial) sedimentation (Dhosrapahar Formation). Continental sedimentation continued until ca. 3.0 Ga. In the eastern (Simlipal Group), western (Birtola Formation), and southwestern (the Mankarchua, Mahagiri, and Keonjhar formations) parts, shallow-marine sedimentation occurred after 3.0 Ga as a result of transgression. However, in the northern part (Dhanjori Formation), continental sedimentation prevailed throughout the Archean. These Late Paleoarchean to Neoarchean terrestrial and near-coastal successions of Singhbhum Craton should be the prime targets for intense geobiological research. [ABSTRACT FROM AUTHOR]

Detrital zircon from three coarse-grained marine siliciclastic rocks was analyzed for U–Pb, Lu–Hf, and trace element compositions to constrain the timing of deposition and sediment provenance of the Cunningham Lake formation (formerly siliciclastic unit of the Sitlika assemblage) in north-central British Columbia. This strategy tests previously proposed sedimentary linkages between the Cache Creek terrane and the westerly rocks of the Stikine terrane. All three samples indicate maximum depositional ages at ca. 205–202 Ma (Rhaetian). The samples contain a predominant ca. 225–215 Ma detrital population, sourced from proximal contemporaneous volcanic arcs, and minor Permian to Middle Triassic and Carboniferous arc-derived detrital populations. The absence of Precambrian grains is consistent with the strongly suprachondritic zircon compositions (εHf(t) = +7 to +20), and indicates exclusively juvenile sources for the Cunningham Lake formation. Late Triassic sources of zircon are not known in the Cache Creek terrane and, except within western Stikine terrane, are uncommon among the Intermontane terranes that amalgamated with the Cache Creek terrane during Late Triassic–Early Jurassic. The Stikine suite (ca. 230–214 Ma) and coeval volcanic rocks in western Stikinia are the most probable sources of Late Triassic detritus for the Cunningham Lake formation. Stikinia's Paleozoic basement is the probable source of Carboniferous detrital zircon. Volcanic arc–backarc complexes in the Cache Creek terrane are the most likely sources of Permian to Middle Triassic detritus in the Intermontane terranes. Accordingly, the siliciclastic rocks of the Cunningham Lake formation represent an overlap sedimentary succession that links Stikinia to the Cache Creek terrane by the latest Triassic. [ABSTRACT FROM AUTHOR]

Glacial sediment research using thin sections began post-1945. Microsedimentology examines sediments at the microscopic level deriving insights into the processes of glacial erosion, transport, and deposition. Two issues exist (1) the difficulty by some in recognizing microstructures in thin section and (2) the absence of quantitative data making data reproduction difficult. The latter is hard to resolve but more image capture and software methodologies are now becoming available at reasonable costs. Thin sections are two-dimensional sections of three-dimensional objects, and this must be considered when measurements, fabrics and other data are assessed. Research into the microaspects of glacial sediments followed a typical scientific trajectory: thin sections description with little uniformity or common "language" for observed microstructures: standardization allowed comparison between different sediments; with standardization, came an open-ended classification; and with cross-comparison with multiple thin sections—a quantitative means of study needs developed. It has become apparent that the basic principles of structural geology had to be applied. Thus, micromorphology has subsumed into a microsedimentological study of glacial sediments where stress parameters, structural fabrics and the mapping of deformation structures and contextual integration allows an understanding of how these sediments have been formed. Examples of the development stages of glacial micromorphology/sedimentology are presented here as well as discussion of future avenues of study. In addition, multiple thin sections are used to illustrate the many aspects of glacial micromorphology and the parameters necessary to understand glacial sedimentology and the processes of glacial sedimentation. [ABSTRACT FROM AUTHOR]

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