A proposal for the chemical and mineralogical characterization of SOH cores

"We propose to provide chemical analyses and petrographic descriptions of selected samples from State of Hawaii Scientific Observation Holes 1, 2 and 4.

The Morphology ofTrypanosoma GambienseandTrypanosoma Rhodesiensein Cultures: And a Comparison with the Developmental Forms Described inGlossina Palpalis

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Volcanic Mound Fields on the East Pacific Rise, 16˚-19˚S: Low Effusion Rate Eruptions at Overlapping Spreading Centers for the Past 1 Myr

Volcanic mound fields identified on SeaMARC II and HMR1 12 kHz side-scan data from the southern East Pacific Rise (SEPR) occur near overlapping spreading centers (OSCs) and migration traces of OSCs. The volcanic mound fields appear as a distinctive hummocky seafloor fabric due to side-scan backscatter reflections from clusters of moundshaped reflectors. The lack of growth of the mound fields away from the ridge axis, and their occurrence in association with OSC traces, suggests that mound fields form along the ridge crest near OSCs. Volcanic mound fields are found where 120 kHz side-scan and visual observations find fields of pillow mounds. Since pillow mounds are constructed by low effusion rate eruptions, the volcanic mound fields found near the OSCs and in their migration traces indicate that volcanic effusion rates tend to be lower near ridge discontinuities than midsegment regions. This tendency for low effusion rate eruptions at OSCs is documented for the past _1 Myr. Three independent measurements of ridge segmentation, (1) volcanic segment boundaries marked by the low effusion rate eruptions, (2) tectonic segments defined by OSCs, and (3) magmatic segment boundaries based on continuity of parental magma composition, all coincide in the study area. High backscatter off-axis lava fields not associated with seamounts are found on seafloor younger than _0.2 Ma. The _0.2 Ma corridor corroborates previous results from the distribution of small isolated volcanoes that indicates randomly distributed off-axis eruptions mainly occur on crust younger than _0.2 Ma

The Mill River Greenway Initiative: Community-Based, Long-Term Greenway Planning and Design In Williamsburg and Northampton, Massachusetts

Puritans first settled Northampton, Massachusetts in the mid-17th century with a vision in mind – that of a well-ordered community in which the Mill River would play an integral part in their lives. So long as the community hewed to the right path, the river would accommodate the community’s needs. Primary among those needs was waterpower, so the anchor sites for development along the river were the falls. Over the next 200 years, as the Puritan mind metamorphosed into an American industrial mentality, the Mill River’s residents created an industrial necklace with mills and factories decorating a ribbon of water. By the mid-19th century, more than 70 mills and factories were established along 15 miles of river from Northampton’s Lower Mills up to Devil’s Den near the headwaters of the river in Goshen. By the mid-20th century, with the Mill River Valley’s industrial base in rapid decline, the necklace deteriorated into a sad scattering of empty factory buildings with little connection to one another. The vision perished and the river escaped the minds of most residents, especially in Northampton where the Corps of Engineers relocated its flow away from the town center. Industry along the river is all but gone. Relic industrial sites now dot the Mill River’s banks, separated by flat stretches of the river that were never appealing for water-powered manufacturing. Though more prone to flooding, many of those stretches have been developed as recreational destinations. The Daughters of the American Revolution (D.A.R.) State Forest in Goshen and Look Park in Florence are just such places, but substantial inaccessible gaps remain between the old factory sites. The factories turned their backs to the river, severing any remaining connection to residents and visitors. There cannot be a true, continuous greenway if these key spots are not renewed and connected. The industrial sites themselves, called “anchor sites,” can serve as gateways and destination points along one continuous greenway, providing access to the stretches of river between them. A few anchor sites have been resuscitated or renovated, such as Meekins Library in Williamsburg Center and old mill buildings in Florence. People are returning, but the ways in which people and these sites relate to the river need to be addressed so that people can come back and reconnect to the river at historically and geographically significant locations. The Mill River Greenway Initiative is the story of a renewed vision, which, like the original, is being pieced together by individuals and small groups -- the creation of a new kind of necklace composed of those same sites at falls and bridges, which, when linked, will provide fulfillment for walkers, naturalists, and anglers, history buffs, artists, and tourists. The river will, once again, play an integral role in the lives of residents

Cooling rate effects on paleointensity estimates in submarine basaltic glass and implications for dating young flows

Cooling rate effects on the intensity of thermoremanent magnetization (TRM) have been well documented in ceramics. In that case, laboratory cooling is generally more rapid than the initial cooling, leading to an overestimate of the paleofield by 5-10% in Thellier-type paleointensity experiments. The reverse scenario, however, has never been tested. We examine the effects of cooling rate on paleointensity estimates from rapidly quenched submarine basaltic glass (SBG) samples from 13 sites at 17°30'-18°30'S on the East Pacific Rise. Absolute cooling rates determined by relaxation geospeedometry at five of these sites range from ~10 to ~330°C min⁻¹ at the glass transition (~650°C). Over the dominant range of remanence blocking temperatures (~200-400°C), the natural cooling rates are approximately equal to or slightly slower than the laboratory cooling rates during the Thellier experiment. These results suggest that while the cooling rate effect might introduce some within-site scatter, it should not result in a systematic bias in paleointensity from SBG. Paleointensity estimates from the 15 sites range from ~29 to 59μT, with an average standard error of ~1μT. Comparison with models of geomagnetic field intensity variations at the site indicate the youngest group of samples is very recent (indistinguishable from present-day) and the oldest is at least 500, and probably several thousand, years old. These age estimates are consistent with available radiometric ages and geologic observations

Morphology and segmentation of the western Galápagos Spreading Center, 90.5°–98°W : plume-ridge interaction at an intermediate spreading ridge

Author Posting. © American Geophysical Union 2003. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 4 (2003): 8515, doi:10.1029/2003GC000609.Complete multibeam bathymetric coverage of the western Galápagos Spreading Center (GSC) between 90.5°W and 98°W reveals the fine-scale morphology, segmentation and influence of the Galápagos hot spot on this intermediate spreading ridge. The western GSC comprises three morphologically defined provinces: A Western Province, located farthest from the Galápagos hot spot west of 95°30′W, is characterized by an axial deep, rift valley morphology with individual, overlapping, E-W striking segments separated by non-transform offsets; A Middle Province, between the propagating rift tips at 93°15′W and 95°30′W, with transitional axial morphology strikes ∼276°; An Eastern Province, closest to the Galápagos hot spot between the ∼90°50′W Galápagos Transform and 93°15′W, with an axial high morphology generally less than 1800 m deep, strikes ∼280°. At a finer scale, the axial region consists of 32 individual segments defined on the basis of smaller, mainly <2 km, offsets. These offsets mainly step left in the Western and Middle Provinces, and right in the Eastern Province. Glass compositions indicate that the GSC is segmented magmatically into 8 broad regions, with Mg # generally decreasing to the west within each region. Striking differences in bathymetric and lava fractionation patterns between the propagating rifts with tips at 93°15′W and 95°30′W reflect lower overall magma supply and larger offset distance at the latter. The structure of the Eastern Province is complicated by the intersection of a series of volcanic lineaments that appear to radiate away from a point located on the northern edge of the Galápagos platform, close to the southern limit of the Galápagos Fracture Zone. Where these lineaments intersect the GSC, the ridge axis is displaced to the south through a series of overlapping spreading centers (OSCs); abandoned OSC limbs lie even farther south. We propose that southward displacement of the axis is promoted during intermittent times of increased plume activity, when lithospheric zones of weakness become volcanically active. Following cessation of the increased plume activity, the axis straightens by decapitating southernmost OSC limbs during short-lived propagation events. This process contributes to the number of right stepping offsets in the Eastern Province.This work was supported by NSF grants OCE98- 18632 to the University of Hawai’i and OCE98-19117 to the Woods Hole Oceanographic Institution; support was provided to M. B. by a CIW/DTM Postdoctoral Fellowshi

Cooling rate effects on paleointensity estimates in submarine basaltic glass and implications for dating young flows

Cooling rate effects on the intensity of thermoremanent magnetization (TRM) have been well documented in ceramics. In that case, laboratory cooling is generally more rapid than the initial cooling, leading to an overestimate of the paleofield by 5–10% in Thellier-type paleointensity experiments. The reverse scenario, however, has never been tested. We examine the effects of cooling rate on paleointensity estimates from rapidly quenched submarine basaltic glass (SBG) samples from 13 sites at 17°30′–18°30′S on the East Pacific Rise. Absolute cooling rates determined by relaxation geospeedometry at five of these sites range from ~10 to ~330°C min^-1 at the glass transition (~650°C). Over the dominant range of remanence blocking temperatures (~200–400°C), the natural cooling rates are approximately equal to or slightly slower than the laboratory cooling rates during the Thellier experiment. These results suggest that while the cooling rate effect might introduce some within-site scatter, it should not result in a systematic bias in paleointensity from SBG. Paleointensity estimates from the 15 sites range from ~29 to 59 μT, with an average standard error of ~1 μT. Comparison with models of geomagnetic field intensity variations at the site indicate the youngest group of samples is very recent (indistinguishable from present-day) and the oldest is at least 500, and probably several thousand, years old. These age estimates are consistent with available radiometric ages and geologic observations

Intrusive dike complexes, cumulate cores, and the extrusive growth of Hawaiian volcanoes

The Hawaiian Islands are the most geologically studied hot-spot islands in the world yet surprisingly, the only large-scale compilation of marine and land gravity data is more than 45 years old. Early surveys served as reconnaissance studies only, and detailed analyses of the crustal-density structure have been limited. Here we present a new chain-wide gravity compilation that incorporates historical island surveys, recently published work on the islands of Hawai‘i, Kaua‘i, and Ni‘ihau, and >122,000 km of newly compiled marine gravity data. Positive residual gravity anomalies reflect dense intrusive bodies, allowing us to locate current and former volcanic centers, major rift zones, and a previously suggested volcano on Ka‘ena Ridge. By inverting the residual gravity data, we generate a 3-D view of the dense, intrusive complexes and olivine-rich cumulate cores within individual volcanoes and rift zones. We find that the Hāna and Ka‘ena ridges are underlain by particularly high-density intrusive material (>2.85 g/cm3) not observed beneath other Hawaiian rift zones. Contrary to previous estimates, volcanoes along the chain are shown to be composed of a small proportion of intrusive material (<30% by volume), implying that the islands are predominately built extrusively

Magmatic Subsidence of the East Pacific Rise (EPR) at 18˚14\u27S Revealed Through Fault Restoration of Ridge Crest Bathymetry

The fault restoration technique of De Chabalier and Avouac [1994] is applied to an ultra-highresolution bathymetry data set from the East Pacific Rise (EPR) at 18140S. Fault offsets are calculated and subtracted from the original seafloor bathymetry to examine the morphology of the unfaulted seafloor surface within an area encompassing the ridge axis 400 [1] 1600 m in dimension. The restored topography reveals a gently sloping seafloor 200 m wide, which slopes 5 inward toward the spreading axis. We attribute this inward sloping seafloor to subsidence within the axial trough due to subsurface magmatic deflation. The vertical deformation field extracted from the bathymetry is used to characterize the ridge axis fault population present in the area. Median fault throws (9 m for inward-facing and 8 m for outwardfacing faults) are comparable to values measured for nearby mature abyssal hill fault populations, suggesting a genetic link. However, median fault spacings (70 and 46 m) are an order of magnitude smaller, and estimated total extensional strain is 3[1]–4[1] greater than values measured for ridge flank faults. These differences indicate the axial fault population at 18140S cannot be rafted onto the ridge flanks to form abyssal hill faults without significant modification, presumably via volcanic burial. We attribute the dense faulting observed in this area to slip on axial fissures during subsidence of the crestal region. The surface subsidence of a volcanic edifice can be modeled in terms of volume change in the magma source reservoir and volume of magma withdrawn from the reservoir. Using the relationship derived for a sill-like magma body, we estimate that the axial depression at 18140S could represent magma withdrawal associated with a small number (4–22) of the frequent dike injection and eruption events required to build the upper crust during the evolution of the trough. The subsidence volumes represented by the axial topography at 18140S are a small percentage of the underlying upper crustal sections (3–4%), suggesting that only a minor mismatch between magma recharge and withdrawal from the axial melt lens during ongoing plate separation could account for this pronounced axial depression

Evidence for a broadly distributed Samoan-plume signature in the northern Lau and North Fiji Basins

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 15 (2014): 986–1008, doi:10.1002/2013GC005061.Geochemical enrichment of lavas in the northern Lau Basin may reflect the influx of Samoan-plume mantle into the region. We report major and trace element abundances and He-Sr-Nd-Hf-Pb-isotopic measurements for 23 submarine volcanic glasses covering 10 locations in the northern Lau and North Fiji Basins, and for three samples from Wallis Island, which lies between Samoa and the Lau Basin. These data extend the western limit of geochemical observations in the Basins and improve the resolution of North-South variations in isotopic ratios. The Samoan hot spot track runs along the length of the northern trace of the Lau and North Fiji Basins. We find evidence for a Samoan-plume component in lavas as far West as South Pandora Ridge (SPR), North Fiji Basin. Isotopic signatures in SPR samples are similar to those found in Samoan Upolu shield lavas, but show a slight shift toward MORB-like compositions. We explain the origin of the enriched signatures by a model in which Samoan-plume material and ambient depleted mantle undergo decompression melting during upwelling after transiting from beneath the thick Pacific lithosphere to beneath the thin lithosphere in the northern Lau and North Fiji Basins. Other lavas found in the region with highly depleted isotopic signatures may represent isolated pockets of depleted mantle in the basins that evaded this enrichment process. We further find that mixing between the two components in our model, a variably degassed high-3He/4He Samoan component and depleted MORB, can explain the diversity among geochemical data from the northern Lau Basin.M.G.J. acknowledges support from NSF grants OCE-1061134, OCE-1153894, and EAR-1145202 and J.B.T. acknowledges support from the French Agence Nationale de la Recherche (grant ANR-10-BLANC-0603 M&Ms—Mantle Melting—Measurements, Models, Mechanisms).2014-10-1