Spatial Distribution of Chesapeake Bay Riparian Hemlock Forests Threatened by Hemlock Woolly Adelgid

Landscape-scale maps of tree species densities are important tools for managing ecosystems threatened by forest pests. Eastern hemlock dominates riparian forests throughout its range. As a conifer in a deciduous landscape, hemlock plays an ecohydrological role, especially when other species are dormant. The nonnative, hemlock woolly adelgid has caused widespread hemlock decline and mortality. We used two existing basal area raster layers first to identify Chesapeake Bay subwatersheds with ≥6 percent hemlock basal area and second to quantify hemlock basal area densities within fixed-width riparian buffers of 50 m, 100 m, 250 m, and 500 m. Hemlock densities were higher in riparian zones compared with entire subwatersheds. In five subwatersheds, 50 m and 100 m zones had higher percentages of pixels with ≥25 percent hemlock basal area. We produced maps identifying hemlock riparian densities in the Pine Creek Watershed, which managers can use to prioritize sites for supplemental conifer planting under anticipated hemlock decline. Study Implications: Forest inventory and satellite data were used to map riparian hemlock stands in the Pine Creek Watershed (Pennsylvania). Pine Creek is a subwatershed of the Chesapeake Bay and an important tributary of West Branch Susquehanna River. Pine Creek headwaters are a brook trout refuge, and hemlock shading along streams stabilizes water temperature. These fisheries provide recreational value and economic support to local communities. Hemlock woolly adelgid, an invasive insect, has recently entered the watershed and will cause hemlock decline and mortality. Our maps assist the Pine Creek Watershed Council in identifying riparian areas for supplemental planting of alternative conifer seedlings.

Potentiality of Uranium Mineralisation in the Environs of Chhattisgarh Basin, India: a new occurrence in Chhibra

The Meso-Proterozoic intracratonic basins are known for hosting medium to high grade, large tonnage, low cost unconformity-type uranium deposits in the world like-Athabasca Basin, Saskatchewan, Canada and the Pine Creek Geosyncline, Northern Territory, Australia. Similarly, there are fourteen Proterozoic basins in India, out of which, the unconformity-related uranium deposits are identified at Lambapur-Yellapur-Chitrial in the northern part of the Cuddapah basin. Based on the geological setting, age and fertile basement provenance, the other Proterozoic basins in India also hold promise for uranium mineralisation. In this context, the Chhattisgarh basin which is third largest Proterozoic basin in Central India occupying an area of 33,000 sq. km. with 2500m thick sediments, is identified as one of the major favourable targets for uranium mineralisation. It is located at the northern fringe of Bastar Craton in parts of Odisha and Chhattisgarh and comprises mostly siliciclastic sediments of Singhora, Chandrapur and Raipur Groups. Uranium exploration carried out in the environs of Chhattisgarh basin mostly along the basin margins, have brought to light a number of uranium occurrences having sizeable dimensions hosted by both the basement rocks viz. Malaikhaman (0.026-0.11% U3O8), Makarumunda (0.013-3.3% U3O8), Damdama (0.026-0.43% U3O8) , Kashipali (0.010-0.96% U3O8), Karichhapar (0.011-0.40% U3O8) and the cover sediments viz. Juba-Banjhapali (0.010-0.078% U3O8), Govardhangiri-Bagia Nala (<0.010-0.80% U3O8), Chitakhol-Renkhol-Bokarda (<0.012-0.39% U3O8). The newly located uranium mineralisation in the sandstones of Rehatikhol Formation near Chhibra which is exposed intermittently over a strike length of 800m with grab samples (n=43) physically assayed 0.014 to 0.140% eU3O8, 0.010 to 0.120% U3O8 (β/γ) and <0.005% ThO2. Uraninite and pitchblende have been identified as uranium minerals. The favourable factors like geological, geochemical, geophysical, sedimentological, tectonic framework and presence of fertile granitic rocks (n=33, 5-26ppm U) in the provenance indicate its potentiality for uranium mineralisation. The exploration so far, has been mostly confined around shallow basin margins leaving deeper part unexplored. With the advancement of geophysical techniques like airborne magnetic, radiometric and electromagnetic surveys it would be possible to explore the deeper part of the basin. In addition, geochemical techniques such as hydro and litho-geochemical sampling could also be applied around suitable litho-structural settings, especially along the shear/fault zones trending NNE-SSW to NW-SE and their intersections with the ENE-WSW trending shear/fault zones. The present paper deals with the potentiality of uranium mineralisation in the environs of Chhattisgarh basin with emphasis on recently located significant occurrence of uranium mineralisation near Chhibra in the Rehatikhol Formation of Singhora Group along the southeastern margin of Chhattisgarh basin.

Footprints of the Alice Springs Orogeny preserved in far northern Australia: An application of multi-kinetic thermochronology in the Pine Creek Orogen and Arnhem Province

The Precambrian Pine Creek Orogen and Arnhem Province represent two of the oldest basement terrains in northern Australia and are often considered to be devoid of significant regional deformation since the cessation of regional metamorphism in the Paleoproterozoic. A major caveat in the current hypothesis of long lived structural inactivity is the absence of published low-temperature thermochronological data and thermal history models for this area. Here we report the first apatite fission track and (U–Th–Sm)/He data for crystalline samples from both the Pine Creek Orogen and Arnhem Province, complemented with apatite geochemistry data acquired by electron microprobe and laser ablation mass spectrometry methods, and present multi-kinetic low-temperature thermal history models. The thermal history models for the Pine Creek Orogen and Arnhem Province reveal a distinct phase of denudation coeval with the Paleozoic Alice Springs Orogeny. By integrating with previous studies, we suggest that this event deformed a larger area of the Australian crust than previously perceived. Localised Mesozoic thermal perturbations proximal to the Pine Creek Shear-Zone additionally record evidence for Mesozoic reheating contemporaneous with mantle induced subsidence and the onset of sedimentation in the Money Shoal Basin, while the Arnhem Province samples demonstrate no evidence of Mesozoic thermal perturbations.Supplementary material: EPMA protocol comparison, AFT plots and modelling, additional geochemistry, datasets and instrumentation parameters are available at https://doi.org/10.6084/m9.figshare.c.5206664

Unification of the Australian cratons before the formation of Nuna

&lt;p&gt;The paleogeography and chronology of the Paleoproterozoic supercontinent Nuna are highly debated. To further test the paleogeography of Australian cratons in the leadup to Nuna formation, we present new paleomagnetic results from two Paleoproterozoic rock formations in North Australia. First, we obtained paleomagnetic directions from the 1825&amp;#177;4 Ma, bimodal Plum Tree Creek Volcanics sequence located within the Pine Creek Inlier of the North Australian Craton. Second, we studied the 1855&amp;#177;2 Ma layered mafic-ultramafic &amp;#8216;Toby&amp;#8217; intrusion from the Kimberley Craton (KC). Samples from both study areas reveal high quality, stable, magnetite related characteristic remanent magnetization directions. Combining within-site clustered mean directions, we obtained two paleopoles, which plot proximal to each other in the present day central Pacific Ocean, off the east coast of Australia. These results agree with previous interpretation that the Kimberly Craton was amalgamated with the rest of the North Australian Craton (NAC) prior to ca. 1.85 Ga. Comparing these new results with slightly younger poles from the NAC and slightly older, rotated poles form the West Australian Craton (WAC) reveal a high degree of clustering suggesting very minimal absolute plate motion between ca. 1.9-1.85 and 1.6 Ga before the final amalgamation of Nuna. All available paleomagnetic poles agree with an assembly, or close juxtaposition, of the two major Australian cratons (NAC and WAC) before 1.8 Ga. Furthermore, the individual virtual geomagnetic poles from the potentially slow cooled Toby intrusion show a non-fisherian distribution along a great circle. This spread might be related to previously interpreted major true polar wander events based on Laurentian data, which would be global if such an interpretation is correct. The assembly of proto-Australia prior to ca. 1.85 Ga roughly 250 to 300 Myr before the final stage of supercontinent Nuna&amp;#8217;s amalgamation ca. 1.6 Ga suggests that assembling of major building blocks, such as Australia and Laurentia for the supercontinent Nuna and Gondwana for the supercontinent Pangea, is an important step in the formation of supercontinents.&lt;/p&gt;

Using detrital geochronology to unravel the Proterozoic greater McArthur Basin of Northern Australia

&lt;p&gt;There is still little known about the occurrence, formation and spatial distribution of long-lived cratonic basins that form during hundreds of millions of years of subsidence. Their histories often span multiple phases of super-continent break-up, dispersal and amalgamation. Each of these phases resulted in the modification of sedimentation rates and drainage within the basins but the broader basin persisted. These changing conditions are recorded in the detrital zircon record, providing a tool for understanding the basin evolution and consequently its palaeogeography.&lt;/p&gt;&lt;p&gt;The informally termed greater McArthur Basin is a regionally extensive Proterozoic basin that overlies the North Australian Craton. It is a vast sedimentary system that stretches across the northern part of the Northern Territory from north-eastern Western Australia to north-western Queensland. It includes Palaeo- to Mesoproterozoic successions of the McArthur and Birrindudu basins, the Tomkinson Province and likely the Lawn Hill Platform and South Nicholson Basin (to the south-east); all interpreted to be contemporaneous systems. However, the full extent of the greater McArthur Basin sedimentary system is still being unravelled. The basin records nearly one billion years of Earth history, from ca. 1.82 Ga to ca. 0.85 Ma. This sedimentary system temporally overlaps with episodes of Palaeo- to Mesoproterozoic tectonism and igneous activity that affected underlying and adjacent terranes, including the Aileron, Warumpi and Musgrave provinces to the present-day south, Pine Creek Orogen and Arnhem Province to the north, Halls Creek Orogen and Tanami Region to the west, and Mount Isa and Murphy provinces to the east. &amp;#160;&lt;/p&gt;&lt;p&gt;LA-ICP-MS detrital zircon U&amp;#8211;Pb geochronology and Lu&amp;#8211;Hf isotope data provide new constraints on the lower sedimentary successions of the McArthur Basin (Tawallah and Katherine River Groups) and demonstrate they are coetaneous with the Tomkinson Province (Tomkinson Creek Group). U&amp;#8211;Pb detrital zircon data show major &lt;sup&gt;207&lt;/sup&gt;Pb /&lt;sup&gt;206&lt;/sup&gt;Pb peaks at ca. 1860 Ma and ca. 2500&amp;#8211;2400 Ma in both the McArthur Basin and Tomkinson Province sediments. Combined with Lu&amp;#8211;Hf isotope data, the detrital zircon age data from the McArthur Basin show similarities to the Aileron Province (to the south) and magmatic rocks of the Gawler Craton, suggesting that these terranes might be possible source areas. Comparatively, the oldest succession within the Tomkinson Province (Hayward Creek Formation), shows similar spectra to units within the Lawn Hill Platform succession (McNamara Group, Surprise Creek Sandstone and Carrara Range Group) possibly suggesting a correlation between the two areas.&lt;/p&gt;&lt;p&gt;Here we explore the links between the North Australia Craton and surrounding continents to further elucidate the evolution of this enigmatic basin throughout the Proterozoic. New palaeogeographic reconstructions link the &amp;#8216;greater&amp;#8217; McArthur basin to the Yanliao Basin and coeval rocks in the North China Craton. The &amp;#8216;greater&amp;#8217; McArthur basin may also have extended into southern Australia, Laurentia and Siberia as a vast intra-continental gulf (the McArthur-Yanliao Gulf) within the core of the supercontinent Nuna/Colombia.&lt;/p&gt;

Woodcutters 55 Years Later: A New Look at an Old Discovery

The Woodcutters Zn-Pb-Ag deposit in the Rum Jungle district of the Pine Creek orogen in northern Australia was discovered in 1964 and produced 4.6 Mt of ore grading 12.3% Zn, 5.6% Pb, and 83 g/t Ag between 1985 and 1999. Woodcutters, together with several other polymetallic, uranium, and phosphate deposits, is within a Paleoproterozoic sequence of fluviatile and shallow marine sediments deposited in a deepening basin between ~2100 and 2025 Ma around the margins of an Archean granitic and gneissic dome. These sediments were overlain by turbidites and volcaniclastic rocks until the basin was inverted and the sediments and mineral deposits were deformed and metamorphosed at 1860 Ma. Whereas the polymetallic and uranium bodies at Rum Jungle are considered to be syngenetic or syndiagenetic, sulfides in the Woodcutters orebody replace dolomitic horizons in an otherwise carbonaceous unit. This suggests that Woodcutters is similar to Mississippi Valley-type mineralization and rules out affinities with younger sedimentary exhalative-style deposits elsewhere in the Pine Creek orogen. A model is proposed whereby metals were eroded from Archean basement rocks into Paleoproterozoic sandstone aquifers following the Great Oxidation Event, which also liberated sulfur by oxidation of pyrite. Evaporative conditions, as suggested by the widespread occurrence of dolomite and magnesite, may have increased the chloride content of seawater and enhanced its capacity to transport metals. Subsequently, deeply circulating seawater leached metals from the aquifers and ascended up a deep, basin-penetrating fault until it intersected carbonaceous sediments. In this environment, Zn and Pb sulfides were deposited under reducing conditions, while sulfur may have been provided by H2S from organic material. The Woodcutters and other deposits at Rum Jungle show how metals formerly locked up in Archean cratons were delivered by erosion under an oxygenated atmosphere to Paleoproterozoic shorelines, where they were further mobilized and concentrated by a variety of processes.

Utilization of pit telemetry to assess microhabitat affinities of stream-dwelling female crayfish during reproductive seclusion

Stream habitat-use of female crayfish during brooding of eggs and hatchlings is a poorly studied aspect of crayfish life history and ecology. Our goal was to use passive integrated transponder (PIT) technology to describe diurnal habitat-use patterns of females of two crayfish species during reproductive seclusion. PIT tags were externally attached to female Cambarus friaufi in Pine Creek, Tennessee, USA and Orconectes meeki meeki in Rock Creek, Missouri, USA. Crayfish were tracked with a portable detector and habitatuse was assessed in 2008 for C. friaufi and 2009 for O. m. meeki. PIT tags proved to be a highly effective tool for relocating crayfish, with = 85% of tagged individuals located at least once. Substrate roughness was identified as the most important variable for both species during brooding, followed by additional substrate-related variables, water velocity, and water depth. Cambarus friaufi, however, was more of a generalist and used microhabitat variables in close proportion to availability, whereas O. m. meeki showed more specialized use of brooding habitat variables. Our results suggest that female crayfish reproductive seclusion is closely linked to sufficiently heterogeneous substrate. Reductions in substrate quality could potentially alter crayfish reproductive capacity, thus impacting biodiversity and productivity of streams.