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Displaying 11 - 20 from the 33 total records
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Distribution of Echinarachnius parma (Lamarck) and Associated Fauna on Sable Island Bank, Southeast Canada
Daniel J. Stanley and Noel P. James
24 pages, 8 figures, 6 plates, 1 table
1971 (Date of Issue: 27 April 1971)
Number 6, Smithsonian Contributions to the Earth Sciences
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A combined bottom photographic and sampling survey of Sable Island Bank southeast of Nova Scotia, Canada, reveals locally high densities (to 180 individual/m2) of the northern sand dollar Echinarachnius parma. Populations of this form are closely related to texture of the sea floor and generally concentrated on moderately sorted fine to medium sand surfaces. Topography and current regime are also correlatable factors; depth, time, salinity, and temperature apparently are not. Sand dollars are second in importance, after current activity, in reworking surficial sediments, and these organisms modify at least a third of the total Bank surface in the study area. Bioturbation is particularly intense in the sector north of Sable Island. Associated epifauna and infauna populations occur in two east-west trending areas on the Bank north and south of Sable Island. Absence of conspicuous fauna, save E. parma, in an east-west zone along the crest of the Bank and near Sable Island results from extremely strong current activity concentrated in this region.

Field and Laboratory Investigations of Antarctic Meteorites Collected by United States Expeditions, 1985-1987
Ursula B. Marvin and Glenn J. MacPherson, editors
116 pages, 38 figures, 9 tables
1992 (Date of Issue: 18 December 1992)
Number 30, Smithsonian Contributions to the Earth Sciences
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This monograph describes the meteorite collecting activities of the United States Antarctic Search for Meteorites (ANSMET) expeditions during the 1984-1985, 1985-1986, and 1986-1987 field seasons. Descriptions and classifications are given of most specimens collected during those expeditions with the exceptions of the types 4, 5, and 6 ordinary chondrites, whose properties are tabulated. Two articles are included that summarize data on the terrestrial ages and thermoluminescence properties of Antarctic meteorites. The Appendix lists all ANSMET specimens classified as of June 1987, in numerical order for each locality and by meteorite class.

Field and Laboratory Investigations of Meteorites from Victoria Land and the Thiel Mountains Region, Antarctica, 1982-1983 and 1983-1984
Ursula B. Marvin and Glenn J. MacPherson, editors
146 pages, 86 figures, 14 tables
1989 (Date of Issue: 16 February 1989)
Number 28, Smithsonian Contributions to the Earth Sciences
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This monograph describes the meteorite collecting activities of the United States Antarctic Search for Meteorites (ANSMET) expeditions of the 1982-1983 and 1983-1984 field seasons. Descriptions and classifications are given of most specimens collected during the 1982-1983 season and some of those collected in the 1983-1984 season. Articles are included reviewing topics such as Antarctic achondrites, carbonaceous chondrites, meteorite weathering under polar conditions, trace element contents of Antarctic meteorites in comparison with those found elsewhere, and the meteorite pairing problem. One chapter describes the crystalline fabric of the ice surrounding a meteorite discovered emerging at the surface. The Appendix lists all ANSMET specimens classified as of June 1984, in numerical order for each locality and by meteorite class. The Appendix also includes a tentative list of paired specimens.

Field and Laboratory Investigations of Meteorites from Victoria Land, Antarctica
Ursula B. Marvin and Brian Mason, editors
134 pages, 79 figures, 11 tables
1984 (Date of Issue: 8 June 1984)
Number 26, Smithsonian Contributions to the Earth Sciences
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This monograph describes the meteorite collecting activities in Victoria Land during the 1980-1981 and 1981-1982 field seasons, and the geodetic measurements of ice motion and ablation at the Allan Hills site. Descriptions and classifications are given for all specimens collected during the 1980-1981 season and for most of those collected during the 1981-1982 season. Review articles are included on the petrology and classification of 145 small meteorites collected in the 1977-1978 season, on Antarctic Type 3 chondrites, and on cosmic-ray-produced nuclides in the Victoria Land meteorites. The first lunar meteorite is described. Chemical analyses of 25 Victoria Land meteorites are published, with a discussion of Antarctic weathering effects. The Appendix lists all of the Victoria Land meteorites classified as of June 1983, by numerical order for each locality and by meteorite class.

Geology of the Lincoln Area, Lewis and Clark County, Montana
William G. Melson
29 pages, 13 figures, 8 tables
1971 (Date of Issue: 15 October 1971)
Number 7, Smithsonian Contributions to the Earth Sciences
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The Lincoln area (townships 13 and 14 N, ranges 7 and 8 W, about thirty miles northwest of Helena, Montana) is underlain by Pre-Cambrian Belt sedimentary rocks intruded by late Cretaceous (?) granitic stocks with concomitant widespread contact metamorphism and mineralization. The granitic stocks are probably related to the Boulder batholith. The pre-intrusion structure is characterized by high angle faults and broad open folds of Cretaceous age (Laramide). Oligocene (?) volcanic rocks were extruded on an eroded surface of the Belt rocks and granitic stocks. A second period of mineralization followed extrusion of the volcanic rocks.

Fracture cleavage which dips consistently to the southwest as well as the overall structure show that a southeast plunging syncline which marks the north end of the Boulder batholith continues into the Lincoln area. The syncline extends at least twenty miles north of the batholith and dominates the structure over an area of about 350 square miles.

About forty square miles of middle Tertiary volcanic rocks are composed of a lower series of andesitic to latitic flows and an upper series of rhyolitic welded ash flows. The features of the welded ash flows suggest that they were deposited in part by a vesiculating mass of rhyolitic magma (pumice froth flows). The volcanic rocks are presumably about the same age as the Lowland Creek volcanics of the Butte area.

The area and the region several miles to the north are about the northern limit of Boulder batholith activity, Tertiary volcanism, and associated mineral deposits. The superposition of these two periods of igneous activity and their gross similarities imply that they are genetically related.

Gold and silver have been produced from epithermal fissure veins. The scant available data suggests that the veins are vertically zoned. There were probably at least two periods of epithermal mineralization: one during the late stage cooling of the stocks, and a second after extrusion of the lower volcanic series.

Remnants of Tertiary surfaces preserved under the volcanic rocks imply that there have been topographic inversions since the middle Tertiary.

Glacial deposits suggest at least one early period of valley glaciation and later, perhaps recent, periods of restricted mountain glaciation. Rich gold placer deposits, such as in McClellan Gulch, accumulated after the earliest period of valley glaciation.

Great Basin Aquatic Systems History
Robert Hershler, David Madsen, and Donald R. Currey, eds.
405 pages, 190 figures, 21 tables
2002 (Date of Issue: 11 December 2002)
Number 33, Smithsonian Contributions to the Earth Sciences
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The 14 papers collected herein treat diverse aspects of the aquatic history of the Great Basin of the western United States and collectively attempt to summarize and integrate portions of the vast body of new information on this subject that has been acquired since the last such compilation was published in 1948. In the first section, four papers (Lowenstein, Negrini, Reheis et al., Sack) focus on the physical aspects of the Great Basin paleolake histories, whereas a fifth paper (Oviatt) summarizes the contributions to the study of Bonneville Basin lacustrine history made by two early giants of the field, Grove Karl Gilbert and Ernst Antevs. In the second section, four papers synthesize perspectives on Great Basin aquatic history provide by diatoms and ostracods (Bradbury and Forester), fishes (Smith et al.), aquatic insects (Polhemus and Polhemus), and aquatic snails (Hershler and Sada), whereas a fifth (Sada and Vinyard) summarizes the conservation status of the diverse aquatic biota that is endemic to the region. In the final section, three papers integrate terrestrial biotic evidence pertaining to Great Basin aquatic history derived from pollen from cores (Davis), floristics (Wigand and Rhode), and the mammal record (Grayson), whereas a fourth (Madsen) examines the relationship between Great Basin lakes and human inhabitants of the region. Although diverse in scope and topic, the papers in this volume are nonetheless linked by an appreciation that integration of geological, biological, and anthropological evidence is a necessary and fundamental key to a mature understanding of Great Basin aquatic systems history.

The Guadalupian Symposium
Bruce R. Wardlaw, Richard E. Grant and David M. Rohr, editors
415 pages, 191 figures, 43 plates, 45 tables
2000 (Date of Issue: 21 August 2000)
Number 32, Smithsonian Contributions to the Earth Sciences
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The internal stratigraphy of the Cutoff Formation in the Guadalupe Mountains is clarified, and the unit is divided into three members: the Shumard Canyon, the El Centro, and the Williams Ranch members. The Shumard Canyon Member of the Cutoff Formation in the Guadalupe Mountains correlates to the upper part of the Cathedral Mountain Formation in the Glass Mountains. The El Centro and Williams Ranch members of the Cutoff Formation and the lower part of the Brushy Canyon Formation, including the Pipeline Shale in the Guadalupe Mountains, correlate to the Road Canyon Formation. The changeover in conodonts from transitional forms to Mesogondolella nankingensis) provides a basal definition for the Guadalupian and occurs within correlation unit 3 in the El Centro Member of the Cutoff Formation and cycle 2 of the Road Canyon Formation.

The geology, stratigraphy, and depositional setting of the Permian in the Del Norte Mountains and of the Word Formation in the Glass Mountains are discussed in detail, and this data suggest deposition in a foreland basin or backbay between the Marathon Fold Belt and the Delaware basin. The internal stratigraphy of the Road Canyon, Word, Vidrio, Altuda, Capitan, and Tessey formations reveal the following: (1) the Road Canyon was deposited in four cycles and the Word in six cycles; (2) the Altuda can be divided into five informal members and the Tessey into three members; (3) the Vidrio is an unconformity-bounded unit; and (4) the Capitan displays characteristic platform margin to slope foresets.

Biozonation of the Guadalupian is discussed, and details are provided on the fusulinid and conodont zonations. Changes in conodont fauna, based on the succession of Mesogondolella species from M. nankingensis to M. altudaensis, divide the Guadalupian into five zones.

Five new species of conodonts (Sweetina crofti Wardlaw, Mesogondolella shannoni Wardlaw, Hindeodus wordensis Wardlaw, Iranognathus punctatus Wardlaw, and Sweetognathus bicarinum Wardlaw) and two new species of fusulinids (Codonofusiella (Lantschichites) altudaensis Wilde and Rudine and Rauserella bengeensis Wilde and Rudine) are described.

Inclusions in the Allende Meteorite
Brian Mason and S. R. Taylor
30 pages, 25 figures, 5 tables
1982 (Date of Issue: 5 October 1982)
Number 25, Smithsonian Contributions to the Earth Sciences
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Six discrete groups of inclusions have been distinguished in the Allende meteorite. Groups I, V, and VI are mostly melilite-rich chondrules, although some have been extensively altered to fine-grained aggregates; Groups II and III are mostly fine-grained aggregates made up largely of spinel and fassaite; Group IV are olivine-rich aggregates and chondrules. Each group has a distinctive trace-element pattern, most clearly shown by the rare-earth (RE) distribution pattern. Group I has an unfractionated pattern (except for a small positive Eu anomaly) at about 10-15 times chondrites; Group II has a highly fractionated pattern with depletion of the heavier lanthanides (Gd-Er) and negative Eu and positive Tm and Yb anomalies; Group III has an unfractionated pattern at about 20 times chondrites, except for negative Eu and Yb anomalies; Group IV has a relatively unfractionated pattern at 2-4 times chondrites; Group V has an unfractionated pattern at 10-20 times chondrites; Group VI has an unfractionated pattern at 10-20 times chondrites, except for positive Eu and Yb anomalies (i.e., complementary to Group III). The complex patterns of trace element distribution in these Allende inclusions indicate a complex history of formation of this meteorite from the solar nebula.

Late Quaternary Progradation and Sand Spillover on the Outer Continental Margin Off Nova Scotia, Southeast Canada
Daniel J. Stanley, Donald J. P. Swift, Norman Silverberg, Noel P. James and Robert G. Sutton
88 pages, 83 figures, 6 tables
1972 (Date of Issue: 11 April 1972)
Number 8, Smithsonian Contributions to the Earth Sciences
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Three distinct sediment types have prograded seaward from the outer shelf to the slope and rise in the vicinity of Sable Island Bank southeast of Nova Scotia during late Quaternary time. On the slope, the oldest facies recovered in cores is a brown to brick red, irregularly stratified, pebbly-sandy-clayey silt. Locally it is covered by an olive gray, clayey silt with a low sand and pebble content. This more homogenous gray facies displays abundant biogenic structures. A third facies, a thin layer of very fine, gray sand and muddy sand, locally covers brown and olive gray sediments on the slope and upper rise. All three facies contain similar light, heavy, and clay mineral suites.

The regional distribution of these facies has been determined by core traverses normal to the shelf edge, including one passing down the axis of The Gully (largest submarine canyon in the area), and another extending down the dissected slope off Sable Island Bank. The brown, late Pleistocene unit is exposed on the floor of The Gully and on its dissected deep-sea fan; postglacial bottom processes have kept younger sediments from accumulating in these areas. The brown beds also are exposed on the lower slope and rise off Sable Island in areas of slumping or nondeposition. The olive gray facies, late Pleistocene-Holocene in age, occurs primarily on the slope; it is thicker on flanks of slope valleys and thinner or absent on the divides. It is absent on part of the lower slope and upper rise. On the lower rise, tan mud with a coarse fraction rich in Foraminifera and shell debris may be the equivalent of the olive gray slope facies.

These sediments reflect changes in the sedimentary regimen during the post-Wisconsinan transgression. The observed sequence starts with the Wisconsin low stand of the sea when glacial drift, including reddish-brown, fluvioglacial sediments, were deposited over the Nova Scotian Shelf as far as Sable Island Bank. Periglacial outwash spread across the bank and flowed seaward around it. Deposition of the slope and rise brown facies is associated with this period; textural inhomogeneity suggests downslope transport by mass movement. Pebbly lenses resulted, in part, from ice-rafting prevalent during this phase. The contact between brown and the overlying olive gray, clayey silt facies is often abrupt, commonly occurring within several centimeters; this change is correlated with the rise of the late Quaternary sea above the margin of Sable Island Bank.

As the sea transgressed across Sable Island Bank in late glacial time, fines winnowed from fluvioglacial sediment were moved north of the Bank (into the Gully Trough) and seaward onto the slope. Coarse materials no longer reached the slope with former frequency, and the fines were supplied at a markedly lower rate. This decrease in sedimentation rate on the slope coincides with an increase in the organic fraction and bioturbation. Suspended fines were reduced to a gray hue as they passed through the sediment-water interface whose rate of upward growth was now an order of magnitude smaller. The Pleistocene-Holocene boundary of approximately 10,000 years B.P. occurs within the olive gray facies. As sea level attained its near-present position, and the present configuration of bottom currents was established, the lag (modified relict or palimpsest) sands on the Nova Scotian Shelf began a pattern of radial dispersal that may now be observed on Sable Island and associated banks. This bottom current activity has resulted in the development of spillover sands on the upper slope and deposition of thin discontinuous layers (including some turbidites) on the slope and rise and in The Gully Canyon.

Late Quaternary Sedimentation and Stratigraphy in the Strait of Sicily
Andres Maldonado and Daniel Jean Stanley
73 pages, 39 figures, 5 tables
1976 (Date of Issue: 3 August 1976)
Number 16, Smithsonian Contributions to the Earth Sciences
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The Strait of Sicily, a broad, elongate, topographically complex platform in the central Mediterranean, separates the deep Ionian Basin from the Alg?ro-Balearic and Tyrrhenian basins to the west. A detailed core analysis shows that the late Quaternary sections in the different sectors of the Strait are distinct from those in the deep Mediterranean basins. Strait lithofacies are characteristically uniform, highly bioturbated, and contain significant amounts of coarse calcareous sediment. Five major sediment types (coarse calcareous sand, sand- to silt-size sediment, ash, mud, and sapropel) are grouped into natural vertical successions termed sequences. The three major sequences defined in the Strait are upward-coarsening and upward-fining, uniform, and turbiditic (including both mud and sand-silt turbidites); sapropel sequences are recovered in cores on the Ionian slope east of the Strait.

The direct relation between sediment type, lateral lithofacies distribution, water depth, and structural displacement is demonstrated. For example, the proportion of turbiditic mud increases while that of hemipelagic mud and bioturbated strata decreases with depth. The effects of regional Quaternary events, particularly climatic changes and eustatic sea level oscillations, are well recorded in cores collected in shallow platform and neritic-bathyal environments; here the upper sediment sequences are truncated and fining- and coarsening-upward sequences, which include coarse calcareous sand layers interbedded with mud and sandy lutite, prevail. In contrast, well stratified units comprising sand (including gravity flow units and volcanic ash) alternating with hemipelagic and turbiditic mud form the surficial deposits in the deep (>1000 m) elongate Linosa, Pantelleria, and Malta basins. Homogeneous bioturbated light olive gray to dusty yellow muddy sequences predominate in the intermediate depth neritic-bathyal environments.

Stratigraphic correlation of cores based on carbon-14 analyses shows that individual units or sequences are not correlatable across the Strait or even within small basins, although it is possible to recognize a general vertical succession of depositional patterns. Sedimentation rates generally decrease with increasing depth. Rates in the deep basins have been relatively uniform from the late Quaternary to the present, while upper (Holocene) sequences in the shallow platform and neritic-bathyal environments have been truncated. Correlation of reflectors on high-resolution subbottom profiles indicates that faulting in many sectors of the Strait is of recent or subrecent origin and that the vertical displacement rate is locally in excess of the average sedimentation rate (i.e., greater than 20 cm per 1000 years).

The absence of sapropel layers in the Strait basins indicates that these depressions remained ventilated during periods when anaerobic conditions prevailed in the deep basins in the eastern and central Mediterranean. An early Holocene paleooceanographic model depicting a possible reversal of currents in the Strait of Sicily region is postulated.

Displaying 11 - 20 from the 33 total records