The Cape Ann Plutonic Suite: A Field Trip for Petrology Classes

Cape Ann, because of its proximity to Boston and many universities, has long been a focus of geologic study. Nineteenth century papers that consider mineralogy or petrology of Cape Ann rocks include Prescott (1839), Nichols (1856), Kimball (1860), Gregory (1862), Mudge (1862), Balch (1864), Cooke (1866, 1867), Knowlton (1867), Hyatt (1869, 1871a,b), Hunt (1871), Wadsworth (1878, 1882a,b, 1885), McDaniel (1884), Sears (1888, 1889, 1890a, 1891a,b, 1893a,b, 1894a,b, 1895, 1898), Shaler (1889), Pearce (1893), Penfield and Forbes (1896), and Washington (1898a,b,c, 1899a,b,c,d). More recent studies of note include Wright (1900), Clapp (1921), Warren and McKinstry (1924), Bowen and Schairer (1935), Palache (1950), Toulmin (1964a,b), Dennen (1976, 1981, 1991a,b, 1992), Zen et al. (1983), Goldsmith (1991), Wones and Goldsmith (1991), Hon et al. (1993), Hepburn et al. (1993, 1998, 2004), and Hepburn and Bailey (1998). With this long history of study, Cape Ann offers an unusual wealth of data and opinion to match the extensive, interesting, and beautiful outcrops that occur there, making it a destination of choice for petrologists. For many years, we have been jointly taking our petrology classes on a one-day field trip to the Cape Ann region to see and discuss igneous rocks in a spectacular setting. We have found this to be a very rewarding experience both for us and for our students. We offer this NEIGC trip to share with others what we think are the best teaching stops, some comments about teaching strategies, diagrams that may be useful for teaching about Cape Ann, and our current understanding of the geologic history of the Cape Ann Plutonic Suite. This is not a trip about new research, although our students have collected data over the years that are included in some of the figures. Instead, it is a chance to look at some great rocks and to discuss the research that others have done in the region beginning in the mid-19th century.

Petrology of the High-Alumina Hoosac Schist from the Chloritoid+Garnet Through the Kyanite+Biotite Zones in Western Massachusetts

The eastern limb of the Berkshire anticlinorium of western Massachusetts (Figure 1) is a complex, multiplydeformed, polymetamorphic, Taconian/Acadian orogenic terrane. The geologic framework of this area is well established, originally by the mapping of B.K. Emerson (1892, 1898, 1899) and Pumpelly et al. (1894), as summarized on the Massachusetts geologic map of Emerson (1917), and more recently by the mapping of L.M. Hall, N.L. Hatch, S.A. Norton, P.H. Osberg, N.M. Ratcliffe, and R.S. Stanley, as summarized on the Massachusetts geologic map of Zen et al. (1983). The summary reports of USGS Professional Paper 1366 in 1988 as well as the work of Hatch et al. (1984), Stanley and Ratcliffe (1985), and Sutter et al. (1985), among others, provide a provocative regional synthesis that brings into sharp focus a variety of interrelated structural, stratigraphic, petrologic, and geochronologic problems. Despite vigorous efforts, our ability to constrain the timing of many fundamental events is still hampered by both the complexity of the terrane and a lack of data. As reviewed by Karabinos and Laird (1988), differentiating between the effects of different metamorphic events remains quite problematic in much of the terrane. The recent work of Hames et al. (1991) and Armstrong et al. (1992) emphasizes the problem of differentiating between Taconian and Acadian orogenic effects along the zone of maximum overlap, which generally coincides with the axis of the Berkshire massif. This field trip (see figure 10 for route) will review the nature of this polymetamorphism in a nearly continuous belt of high-alumina, Gassetts-like schists of the Hoosac formation that occurs along the eastern margin of the Berkshire massif. As a bonus we will have the opportunity to examine the nearly continuous prograde metamorphic evolution of a relatively unusual, but mineralogically interesting, bulk composition that has historically received much attention

Advances in the Geology of the Tobacco Root Mountains, Montana, and Their Implications for the History of the Northern Wyoming Province

Integrated studies by Keck Geology Consortium participants have generated many new insights into the Precambrian geology of the Tobacco Root Mountains. We have clarified the tectonic setting and origin of two suites of metamorphic rocks: (1) a quartzofeldspathic gneiss complex with associated metasupracrustal rocks (the combined Indian Creek and Pony–Middle Mountain Metamorphic Suites) that originated in a continental arc setting between 3.35 and 3.2 Ga with subsequent sedimentation and (2) mafic metavolcanic rocks with intercalated metasedimentary rocks (the Spuhler Peak Metamorphic Suite) from a suprasubduction zone ophiolite or backarc basin possibly of Proterozoic age. A poorly preserved metamorphic event at 2.45 Ga affected the former but not the latter, as did the intrusion of rift-related mafic dikes and sills at 2.06 Ga. Both suites were amalgamated, metamorphosed to at least upper amphibolite facies, subjected to simple shear strain and folded into map- and outcrop-scale sheath folds, and tectonically unroofed during the period 1.78 to 1.71 Ga. We name this event the Big Sky orogeny. The Proterozoic geology of the Tobacco Root Mountains can be integrated with coeval features of the geology of the northern Wyoming province to outline a northeast-trending, southeast-vergent belt as the Big Sky orogen. The Big Sky orogen consists of a metamorphic hinterland flanked to the southeast by a foreland of discrete ductile shear zones cutting older basement, and to the northwest by arc-related metaplutonic bodies and the trace of a fossil subduction zone in the upper mantle. Archean blocks to the north of the Big Sky orogen may have been accreted as allochthonous terranes during collision and convergence. The remarkable synchroneity of collision along the Big Sky orogen with tectonism in the Trans-Hudson orogen along the eastern margin of the Wyoming province and in the Cheyenne belt to the south of the province raise profound but unanswered questions about the process by which the Wyoming province was added to the rest of the ancestral North American craton

Isotope Geochemistry of Proterozoic Talc Occurrences in Archean Marbles of the Ruby Mountains, Southwest Montana, U.S.A

Talc occurs as massive, economic deposits in upper amphibolite facies marbles of Archean age in southwestern Montana. Previous workers have demonstrated that the talc is a replacement of the marble that resulted from interaction with a large volume of fluid. δ18O (SMOW) values for dolomite and calcite range from 20-25‰ for the unaltered Archean marbles to as little as 8-10‰ in the talc deposits, suggesting that the metasomatic fluids had low δ18O values. In contrast, δ13C values for calcite and dolomite are similar for all samples (-2 to +2‰ PDB). Therefore, it is likely that the metasomatic fluids were oxygen-rich and carbon-poor, namely water-rich and CO2-poor. A CO2-poor fluid is also indicated by Δ13C (calcite-graphite) values (3.6-5.3‰), which appear little altered from values expected for upper amphibolite facies marbles, and by the occurrence of the mineral assemblage talc+calcite, 40Ar/39Ar age spectra for hornblende, phlogopite, and biotite record cooling at 1.72 Ga from a regional thermal event. 40Ar/39Ar age spectra of fine-grained muscovite associated with the talc date talc formation at 1.36 Ga. The Ar data limit the temperature of talc crystallization to below ∼350 DEGC, the biotite closure temperature for Ar diffusion. If the metasomatic fluid was seawater (0‰), then the carbonate oxygen data require a minimum temperature of 270 DEGC for talc formation. Oxygen (δ18O = 4.7 to 8.8‰) and hydrogen (D/H = -49.9 to -57.6 SMOW) isotope data for the talc are consistent with a 200-300 DEGC metasomatic fluid derived from seawater, based on theoretical models of the fractionation of oxygen and hydrogen between talc and water. Regional, northwest-trending faults associated with the extension that formed the Belt Basin in the Middle Proterozoic may have provided channels for seawater to circulate in continental crust and to react with marble, forming talc at depths of 5-10 km

Managing and resisting ‘degeneration’ in employee-owned businesses: a comparative study of two large retailers in Spain and the UK

Employee-owned businesses have recently enjoyed a resurgence of interest as possible ‘alternatives’ to the somewhat tarnished image of conventional investor-owned capitalist firms. Within the context of global economic crisis, such alternatives seem newly attractive. This is somewhat ironic because, for more than a century, academic literature on employee-owned businesses has been dominated by the ‘degeneration thesis’. This suggested that these businesses tend towards failure – they either fail commercially, or they relinquish their democratic characters. Bucking this trend and offering a beacon - especially in the UK - has been the commercially successful, co-owned enterprise of the John Lewis Partnership (JLP) whose virtues have seemingly been rewarded with favourable and sustainable outcomes. This paper makes comparisons between JLP and its Spanish equivalent Eroski – the supermarket group which is part of the Mondragon cooperatives. The contribution of this paper is to examine in a comparative way how the managers in JLP and Eroski have constructed and accomplished their alternative scenarios. Using longitudinal data and detailed interviews with senior managers in both enterprises it explores the ways in which two large, employee-owned, enterprises reconcile apparently conflicting principles and objectives. The paper thus puts some new flesh on the ‘regeneration thesis’

The medical student

The Medical Student was published from 1888-1921 by the students of Boston University School of Medicine

Oceanic Sharks Clean at Coastal Seamount

Interactions between pelagic thresher sharks (Alopias pelagicus) and cleaner wrasse were investigated at a seamount in the Philippines. Cleaning associations between sharks and teleosts are poorly understood, but the observable interactions seen at this site may explain why these mainly oceanic sharks regularly venture into shallow coastal waters where they are vulnerable to disturbance from human activity. From 1,230 hours of observations recorded by remote video camera between July 2005 and December 2009, 97 cleaner-thresher shark events were analyzed, 19 of which were interrupted. Observations of pelagic thresher sharks interacting with cleaners at the seamount were recorded at all times of day but their frequency declined gradually from morning until evening. Cleaners showed preferences for foraging on specific areas of a thresher shark's body. For all events combined, cleaners were observed to conduct 2,757 inspections, of which 33.9% took place on the shark's pelvis, 23.3% on the pectoral fins, 22.3% on the caudal fin, 8.6% on the body, 8.3% on the head, 2.1% on the dorsal fin, and 1.5% on the gills respectively. Cleaners did not preferentially inspect thresher sharks by time of day or by shark sex, but there was a direct correlation between the amount of time a thresher shark spent at a cleaning station and the number of inspections it received. Thresher shark clients modified their behavior by “circular-stance-swimming,” presumably to facilitate cleaner inspections. The cleaner-thresher shark association reflected some of the known behavioral trends in the cleaner-reef teleost system since cleaners appeared to forage selectively on shark clients. Evidence is mounting that in addition to acting as social refuges and foraging grounds for large visiting marine predators, seamounts may also support pelagic ecology by functioning as cleaning stations for oceanic sharks and rays

Progress of irrigation research on Willamette Valley soils

Published April 1968. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

A deep learning approach to photo–identification demonstrates high performance on two dozen cetacean species

We thank the countless individuals who collected and/or processed the nearly 85,000 images used in this study and those who assisted, particularly those who sorted these images from the millions that did not end up in the catalogues. Additionally, we thank the other Kaggle competitors who helped develop the ideas, models and data used here, particularly those who released their datasets to the public. The graduate assistantship for Philip T. Patton was funded by the NOAA Fisheries QUEST Fellowship. This paper represents HIMB and SOEST contribution numbers 1932 and 11679, respectively. The technical support and advanced computing resources from University of Hawaii Information Technology Services—Cyberinfrastructure, funded in part by the National Science Foundation CC* awards # 2201428 and # 2232862 are gratefully acknowledged. Every photo–identification image was collected under permits according to relevant national guidelines, regulation and legislation.Peer reviewedPublisher PD