An All-Day Symposium on "Trials Data and Their Handling" was held by the Astronautics and Guided Flight Section of the Society on 16th November 1965. Three papers were presented and discussed: "Developments in Range Instrumentation", by J. E. A. Harrison, RAE Aberporth, with W. N. Neat, MA, FRAeS (Bristol Siddeley Engines) in the chair; "The Acquisition and Processing of Data From the Ariel 1 and 2 Satellites", by Dr. E. B. Dorling, Space Research Management Unit, Science Research Council (now at the Mullard Space Science Laboratory, University College, London), with Dr. H. Fuchs (Hawker Siddeley Dynamics Ltd) in the Chair; and "Analysis and Interpretation of Telemetered Results of Blue Streak Flight Trials", by P. L. V. Hickman, Chief Dynamicist, Hawker Siddeley Dynamics Ltd, with H. G. R. Robinson (Head of Instrument and Electrical Engineering Department, RAE Farnborough) in the chair. The Discussion was summarised by Mr. J. L. Nayler.

This dataset was digitized by the U.S. Geological Survey EROS Data Center and U.S. Geological Survey Spokane Field Office for input into an Arc/Info geographic information systsem (GIS). The digital geologic map database can be queried in many ways to produce a variety of derivative geologic maps.

Interpretations of gravity and aeromagnetic anomaly data, supplemented by results from two seismic reflection profiles and five magnetotelluric soundings, were used to study buried structure and lithology of the Libby thrust belt of northwestern Montana. The gravity anomaly data show a marked correlation with major structures. The Purcell anticlinorium and the Sylvanite anticline are very likely cored by stacks of thrust slices of dense crystalline basement rocks that account for the large gravity highs across these two structures. Gravity anomaly data for the Cabinet Mountains Wilderness show a string of four broad highs. The principal magnetic anomaly sources are igneous intrusive rocks, major fault zones, and magnetite-bearing sedimentary rocks of the Ravalli Group. The most important magnetic anomalies in the principal study area are five distinct positive anomalies associated with Cretaceous or younger cupolas and stocks.

Precambrian crystalline rocks of the Rocky Mountain region of the United States represent two age provinces.An Archean province (older than 2,600 million years) occupies Wyoming and adjacent parts of Utah, Montana, and South Dakota.A Proterozoic province (about 1,600 to 1,800 million years old), is represented by only sparse exposures west and northwest of the older terrane, and by extensive exposures to the south.The Archean province is mostly felsic gneisses and associated metasedimentary rocks that were metamorphosed about 2,800 million years ago.Tonalitic to granodioritic plutons were emplaced in this terrane 2,500 to 2,760 million years ago.In Colorado, a thick sequence of volcanic and sedimentary rocks was deposited between 2,000 and 1, 750 million years ago.These rocks were metamorphosed and intruded by numerous granodioritic plutons about 1, 700 million years ago.This province was invaded by granitic plutons 1,400 million years ago and again, in central Colorado, 1,015 million years ago.Shelf-type sedimentary sequences were deposited on the older crust during the interval from 2,500 to 1, 700 million years ago and are preserved in a belt from southern Wyoming to the Black Hills.A younger sequence, 1,460 to 1,600 million years in age, is preserved only as the Uncompahgre Formation in southwestern Colorado.A still younger sequence, the miogeoclinal Belt Supergroup, 850 to 1,500 million years in age, is preserved in western Montana and northern Idaho.Rocks roughly equivalent to but isolated from the Belt Supergroup include the Y ellowjacket Formation and Lemhi Group of Idaho and the Uinta Mountain Group of northeastern Utah and northwestern Colorado.Eugeoclinal rocks, including diamictites, were deposited west of the miogeoclinal rocks beginning approximately 860 million years ago.

The Wallace 1? x 2 quadrangle in Montana and Idaho was studied by an interdisciplinary research team that included geologists, geochemists, and geophysicists, as well as specialists in isotopic dating and remote sensing. The basic data resulting from these studies, as well as the final metallic mineral resource assessments, are published as a folio of maps, figures, tables, and accompanying discussions. This circular provides background information on the studies and lists the published components of the resource appraisal. An extensive bibliography lists both specific and general references that apply to this geoscience study of the quadrangle.

About 40 mi (65 km) west of the Rocky Mountain trench and at least 9 mi (15 km) above the sole detachment of the Rocky Mountain thrust belt is a zone of Cretaceous-Tertiary thrust faults up to 25 mi (40 km) wide in middle Proterozoic and Cambrian rocks. This zone (the Libby thrust belt) extends northward from the Lewis and Clark line to the northwest corner of Montana. Within the Libby thrust belt is a series of complex ramps, horsts, splays, and folds that accommodate a tectonic shortening End_Page 850------------------------------ of about 6.2 mi (10 km). Backsliding has occurred on some listric thrust faults, and middle Tertiary(?) extensional horst-and-graben faults offset or join most thrust faults. On the east, the lead thrust ramps up onto the broad open Purcell anticlinorium. On the west, the Libby thrust belt is overridden in the north by the lead thrust of the Yaak plate (whose central part is the broad, open Sylvanite anticline), and in the south, it is overridden by the Moyie thrust (which trends northwest and also overrides the west edge of the Yaak plate). An essentially continuous section, 46,000 ft (14,021 m) thick, of Belt rocks is displayed on the south-plunging Sylvanite anticline. The base is not exposed, and the top is eroded. A section of similar thickness exists on the west flank of the Purcell anticlinorium, where the Belt Supergroup is overlain by about 3,000 ft (914 m) of Cambrian rock. The Cambrian occurs in the broad synclinal Libby trough that is paired with the Purcell anticlinorium, and these Cambrian strata are also caught up in the Libby thrust belt. Geologic cross sections suggest that the Belt rocks have overridden the Cambrian at shallow depths only and that Cambrian and younger Phanerozoic strata probably do not occur at greater depths beneath and west of the Purcell anticlinorium. This interpretation differs significantly from interpretations that suggest intercalation of major wedges of Paleozoic and Belt rocks at depth in this same area. End_of_Article - Last_Page 851------------