Deep crustal deformation by sheath folding in the Adirondack Mountains, USA

As described by McLelland and Isachsen, the southern half of the Adirondacks are underlain by major isoclinal (F sub 1) and open-upright (F sub 2) folds whose axes are parallel, trend approximately E-W, and plunge gently about the horizontal. These large structures are themselves folded by open upright folds trending NNE (F sub 3). It is pointed out that elongation lineations in these rocks are parallel to X of the finite strain ellipsoid developed during progressive rotational strain. The parallelism between F sub 1 and F sub 2 fold axes and elongation lineations led to the hypothesis that progressive rotational strain, with a west-directed tectonic transport, rotated earlier F sub 1-folds into parallelism with the evolving elongation lineation. Rotation is accomplished by ductile, passive flow of F sub 1-axes into extremely arcuate, E-W hinges. In order to test these hypotheses a number of large folds were mapped in the eastern Adirondacks. Other evidence supporting the existence of sheath folds in the Adirondacks is the presence, on a map scale, of synforms whose limbs pass through the vertical and into antiforms. This type of outcrop pattern is best explained by intersecting a horizontal plane with the double curvature of sheath folds. It is proposed that sheath folding is a common response of hot, ductile rocks to rotational strain at deep crustal levels. The recognition of sheath folds in the Adirondacks reconciles the E-W orientation of fold axes with an E-W elongation lineation

U-Pb zircon geochronology and evolution of some Adirondack meta-igneous rocks

An update was presented of the recent U-Pb isotope geochronology and models for evolution of some of the meta-igneous rocks of the Adirondacks, New York. Uranium-lead zircon data from charnockites and mangerites and on baddeleyite from anorthosite suggest that the emplacement of these rocks into a stable crust took place in the range 1160 to 1130 Ma. Granulite facies metamorphism was approximately 1050 Ma as indicated by metamorphic zircon and sphene ages of the anorthosite and by development of magmatitic alaskitic gneiss. The concentric isotherms that are observed in this area are due to later doming. However, an older contact metamorphic aureole associated with anorthosite intrusion is observed where wollastonite develops in metacarbonates. Zenoliths found in the anorthosite indicate a metamorphic event prior to anorthosite emplacement. The most probable mechanism for anorthosite genesis is thought to be ponding of gabbroic magmas at the Moho. The emplacement of the anorogenic anorthosite-mangerite-charnockite suite was apparently bracketed by compressional orogenies

Low noise high performance 50nm T-gate metamorphic HEMT with cut-off frequency f_T of 440 GHz for millimeterwave imaging receivers applications

The 50 nm m-HEMT exhibits extremely high f<sub>T</sub>, of 440GHz, low F<sub>min</sub> of 0.7 dB, associated gain of 13 dB at 26 GHz with an exceptionally high Id of 200 mA/mm and gm of 950 ms/mm at low noise biased point

50-nm T-gate metamorphic GaAs HEMTs with f_T of 440 GHz and noise figure of 0.7 dB at 26 GHz

GaAs-based transistors with the highest f/sub T/ and lowest noise figure reported to date are presented in this letter. A 50-nm T-gate In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As metamorphic high-electron mobility transistors (mHEMTs) on a GaAs substrate show f/sub T/ of 440 GHz, f/sub max/ of 400 GHz, a minimum noise figure of 0.7 dB and an associated gain of 13 dB at 26 GHz, the latter at a drain current of 185 mA/mm and g/sub m/ of 950 mS/mm. In addition, a noise figure of below 1.2 dB with 10.5 dB or higher associated gain at 26 GHz was demonstrated for drain currents in the range 40 to 470 mA/mm at a drain bias of 0.8 V. These devices are ideal for low noise and medium power applications at millimeter-wave frequencies

50 nm GaAs mHEMTs and MMICs for ultra-low power distributed sensor network applications

We report well-scaled 50 nm GaAs metamorphic HEMTs (mHEMTs) with DC power consumption in the range 1-150 ΜW/Μ demonstrating f<sub>T</sub> of 30-400 GHz. These metrics enable the realisation of ultra-low power (<500 ΜW) radio transceivers for autonomous distributed sensor network applications

First Recorded Observance of the Dinoflagellate Prorocentrum minimum (Pavillard) Schiller 1933 in Mississippi Sound and Adjacent Waters

The present paper documents the occurrence of the dinoflagellate Prorocentrum minimum in Mississippi Sound and adjacent coastal waters. Outbreaks of discolored water are attributed to blooms of P. minimum in February 1977 and in January and February 1981. Data are presented on the seasonality of the organism in St. Louis Bay. Observations on water appearance and a descriptive analysis of the cells are presented for the 1981 blooms

Stratigraphy and structural geology in the Amenia-Pawling Valley, Dutchess County, New York

Guidebook for field trips in western Massachusetts, northern Connecticut and adjacent areas of New York: 67th annual meeting October 10, 11, and 12, 1975: Trip C-1

First Recorded Observance of the Dinoflagellate Prorocentrum minimum (Pavillard) Schiller 1933 in Mississippi Sound and Adjacent Waters

The present paper documents the occurrence of the dinoflagellate Prorocentrum minimum in Mississippi Sound and adjacent coastal waters. Outbreaks of discolored water are attributed to blooms of P. minimum in February 1977 and in January and February 1981. Data are presented on the seasonality of the organism in St. Louis Bay. Observations on water appearance and a descriptive analysis of the cells are presented for the 1981 blooms

Records of Deep-Water Chaetognaths from the Northern Gulf of Mexico

Fourteen species of deep-water Chaetognatha were present in plankton samples collected between 200 and 677 m at five stations along the continental slope of the northem Gulf of Mexico. Samples were taken in conjunction with the MARFlN Geryon cruises of 1987 and 1988. New Gulf of Mexico records resulting from this study were Eukrohnia calliops, Eukrohnia proboscidea, Mesosagitta sibogae, and Sagitta megalophthalma. Other deepwater species present were Eukrohnia fowleri, E. bathypelagica, E. bathyantarctica, Caecosagitta macrocephala, Mesosagitta decipiens, M. minima, Solidosagitta planctonis, Krohnitta subtilis, Flaccisagitta hexaptera, and F. lyra. In addition, the normally epiplanktonic taxa, Pterosagitta draco, Serratosagitta serratodentata, and Sagitta bipunctata occurred in some of the samples