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Displaying 1 - 10 from the 41 total records
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The Red Alga Polysiphonia (Rhodomelaceae) in the Northern Gulf of California
George J. Hollenberg and James N. Norris
21 pages, 10 figures
1977 (Date of Issue: 25 August 1977)
Number 1, Smithsonian Contributions to the Marine Sciences
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Abstract

Taxonomic studies of Polysiphonia show 14 species to be present in the northern Gulf of California, Mexico. One of these, P. sphaerocarpa var. cheloniae is described herein as a new variety, and is found growing exclusively on the green sea turtle, Chelonia mydas L. This and three other species are recorded for the first time in the Gulf of California. The distribution of six other species is extended.


The Echinoderm Fauna of Ascension Island, South Atlantic Ocean
David L. Pawson
115 pages, Vol. 10, 4 figures, 12 plates, 5
1978 (Date of Issue: 1 May 1978)
Number 2, Smithsonian Contributions to the Marine Sciences
DOI: 10.5479/si.01960768.2.1
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Abstract

Two recent intertidal collecting expeditions and existing museum collections have added much to knowledge of the Ascension Island echinoderm fauna. Twenty-five species are now known from Ascension; eight are new records. One new species, Holothuria (Halodeima) manningi, and one new subspecies, Echinometra lucunter polypora, are described. Diadema ascensionis Mortensen is regarded as a subspecies of D. antillarum Philippi, and Pseudoboletia atlantica H. L. Clark is regarded as a subspecies of P. maculata Troschel.

The echinoderm fauna of Ascension Island includes 8 amphi-Atlantic species, 3 western Atlantic species, 4 eastern Atlantic species, 5 circumtropical species, 4 species shared only with St. Helena, and I endemic species. There are in addition three endemic subspecies. Twelve species are shared with St. Helena, and both islands are closely similar in terms of numbers and relationships of their faunal components. Colonization of both islands by planktonic larval stages is suggested. Dendrochirotid holothurians, which lack such larval stages, are not represented at either St. Helena or Ascension. The structure of the Ascension fauna seems to have been determined by vagaries of ocean surface and subsurface currents. In contrast, Bermuda, which sits astride the Gulf Stream, has a fauna that is entirely typical of the West Indian region to the the south.


Salt Tectonics and Basement Fractures: Key Controls of Recent Sediment Distribution on the Balearic Rise, Western Mediterranean
Gilbert Kelling, Andrés Maldonado and Daniel Jean Stanley
52 pages, 19 figures, 9 tables
1979 (Date of Issue: 19 October 1979)
Number 3, Smithsonian Contributions to the Marine Sciences
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Abstract

The Balearic Rise is a morphologically and structurally complex feature on the southern margin of the Balearic Platform, in the western Mediterranean. Originating as a foundered block in Late Miocene time, the rise has acquired a sedimentologically diverse cover of Plio-Quaternary sediments. A study by means of high-resolution reflection profiling (3.5 kHz) and gravity/piston cores emphasizes the effects of a variety of sedimentary processes and of structural controls in the genesis of these Plio-Quaternary sequences. During this geologically recent time interval the Menorca Canyon-Valley-Fan system has exerted an important influence on the sedimentary development of this marginal feature.

On the basis of the 3.5kHz profiles, eight categories of acoustic response of the seafloor and shallow subbottom sediments have been defined and can be linked to distinctive sub-environments of the rise that are characterized by specific sedimentary and structural attributes. Abrupt variations in thickness of the Plio-Quaternary sequence attest to the continuing activity of faulting, which has generated a horst-and-graben morphology across most of the rise. More continuous subsidence is evident below the Menorca Fan but even here subrecent fracturing, accompanied by salt-diapirism, has produced a physiographic and sedimentologic complexity which differs significantly from most of the currently accepted submarine fan models.

The cored sediments fall into five main types: bioclastic (and terrigenous) sand, silt, turbidite mud, hemipelagic mud, and calcareous ooze. Combinations of these sediment types form three principal associations or sequences: channel sands, turbiditic sequences, and hemipelagic sequences. Four distinct core assemblages are also recognized, on the basis of predominant sediment type and sequence: channel sand assemblage, proximal turbiditic/hemipelagic assemblage, hemipelagic/turbiditic mud assemblage, and basin plain assemblage.

Radiocarbon dating of core samples yields average sedimentation rates of 6 to 7 cm per thousand years, the highest rates being encountered on the Balearic Basin plain and in the main Menorca Fan channel while the lowest rates occur in the hemipelagic muds of the elevated regions of the rise. Most of the thick channel sands were deposited between 23,000 and 16,000 years BP, during the last major lowering of sea level.

The Menorca Fan differs significantly in physiography and sediment distribution from most other modern submarine fans, mainly because of the reduced importance of overbank flow and channel migration, which results from the activity of shallow fractures and the blocking effects of salt-diapirs, together with the exceptionally coarse grade of material supplied to the fan.


Submarine Canyon Wall Sedimentation and Lateral Infill: Some Ancient Examples
Daniel Jean Stanley
32 pages, 17 figures
1980 (Date of Issue: 13 February 1980)
Number 4, Smithsonian Contributions to the Marine Sciences
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Abstract

Submarine canyon wall and tributary sequences at three Annot Sandstone localities in the French Maritime Alps record early-stage resedimentation events in proximal sectors of the Tertiary Annot Basin. Canyon margin lithofacies are distinctive in that they comprise a more variable suite of stratal types than intracanyon slope, canyon axis, distal fan and basin series of the same formation. Characteristic criteria include the highly variable geometry and spatial distribution of the series of strata, irregular bedding thickness, paleocurrent directions that diverge from the predominant regional patterns, and discontinuities within the formation and between the Annot Sandstone and the older marine shale series (Eocene Marnes bleues) forming the canyon margins. Three distinctive sandstone stratification types dominate the “grès d'Annot” canyon wall association: type 1 units, moderately to well-stratified and massive (often amalgamated), emplaced by debris flow and a continuum of sediment-fluid flow mechanism, not specifically identifiable in the field; some thick sand layers may represent deposition as ‘quick’ beds from high-concentration underflows, possibly gradational between liquified and turbidity current flows; type 2 units, displaying slightly to extensive deformed horizons within but not throughout the beds, probably are related to liquefied flow and post-depositional liquefaction processes; and type 3 units, emplaced ‘en masse’ and in some cases showing complete disruption of primary stratification (chaotic bedding), are identified as slides and slumps. In addition to the three above types, lower proportions of graded, generally thin ‘classic’ sandstone turbidites (Ta-b, Tb-c, and Tb-e) and mudstone turbidites are recognized.

Although they appear as distinctly different entities in the field, a genetic relation between some depositional types is suggested. The mapped facies diversity is interpreted in terms of flow transformation, that is, the release of different sediment types along the dispersal path from a single sediment gravity flow as it evolves during its progression downslope. The diversity of mass flow products at the three canyon margin localities records a variable succession of transformation phases on the relatively steep slopes (locally in excess of 10°) within a short distance from the point of initial failure. The distinctive aspect of “grès d'Annot” canyon margin sedimentation is the repetitive erosion→transport→deposition pattern of lateral infill. Definition of these proximal lithofacies serves to better understand the origin of the more distal marine fan and Annot Basin plain sequences seaward of the three canyon localities examined and also can be applicable to the study of modern canyon-fan settings.


Distribution of Recent Benthic Foraminifera off the North American Atlantic Coast
Stephen J. Culver and Martin A. Buzas
28 pages, 14 figures, 10 tables
1980 (Date of Issue: 11 July 1980)
Number 6, Smithsonian Contributions to the Marine Sciences
DOI: 10.5479/si.01960768.6.1
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Abstract

A computer file of all available distributional data on the recent benthic foraminifera off the North American Atlantic Coast was constructed from 142 papers published over the last 130 years. Manipulation of this file produced 5 catalogs and 150 maps.

Catalog 1 lists alphabetically species names with publication and locality information as recorded in the literature (i.e. unsynonomized). Catalog 2 lists alphabetically synonomized species names with publication and locality information. Catalogs 3 and 4 list alphabetically all unsynonomized and synonomized species names, respectively. Catalog 5 lists synonomized species names by increasing latitude and longitude.

During the last 130 years, 1303 names have been used to record benthic foraminifera off the North American Atlantic Coast. Through synonomization this number was reduced to 876 of which 149 occur at 20 or more of the 542 sample sites. Computer-generated maps were drawn for these 149 most commonly recorded species.

Species were grouped by depth and geographic distribution through examination of the maps. Seven species are coastal in their distribution, 71 occur mainly at depths of less than 200 m, 41 at depths of greater than 200 m, and 30 are ubiquitous. Thirteen species alter their depth distribution with latitude.

Geographically, the species group into 6 categories. Thirty-one species occur from Florida to Cape Hatteras, 26 from Cape Hatteras to Cape Cod, 4 from Cape Cod to Newfoundland, 22 from Florida to Cape Cod, 40 from Cape Hatteras to Newfoundland, and 26 are ubiquitous. Because of the overlapping distribution of the species, no simple boundaries can be drawn for faunal provinces. We recognize two major overlapping faunal provinces: a northern province from Newfoundland to Cape Hatteras and a southern province from Florida to Cape Cod.


The Saint-Antonin Conglomerate in the Maritime Alps: A Model for Coarse Sedimentation on a Submarine Slope
Daniel Jean Stanley
25 pages, 12 figures, 1 table
1980 (Date of Issue: 23 July 1980)
Number 5, Smithsonian Contributions to the Marine Sciences
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Abstract

The Upper Eocene to Lower Oligocene Saint-Antonin Conglomerate, a formation more than 1000 m thick well exposed in the French Maritime Alps, about 30 km north of the Mediterranean coast, comprises coarsening-upward successions, or megasequences, of silty shale-siltstone, sandstone and conglomerate sections. The megasequences include coarse channelized deposits associated with coarse lenticular and fine-grained sheet facies that are identified as migrating channels and lobe and channel overflow deposits. Microfossils in the finer-grained units indicate dispersal in an open marine, outer shelf to upper bathyal environment where minimal depths ranged from 100 to 200 m. The spatial and temporal distribution patterns of facies successions, assemblage of stratification types and sedimentary structures, and petrology of the various textural grades indicate submarine progradation on a slope, or in a slope basin, seaward of a fan delta system. The Saint-Antonin Conglomerate is more similar to alluvial fans than to some of the gravel-rich submarine fan deposits that accumulate on a gentle gradient at the base of a slope. The coarsening-upward megasequences record a strong tectonic overprint, including a northward shift of the basin margin on which these strata were deposited, concurrent andesitic flows and structurally-induced fan delta switching on the adjacent land. This latter phenomenon was largely responsible for the irregular back-and-forth migration of the sandstone and gravel-rich tongues on the upper slope. Emplacement of poorly sorted (disorganized) conglomerates and pebbly sandstones, and of strata displaying crudely stratified inverse grading or preferred clast fabric, was largely by debris flow and associated high-concentration dispersions. Slumping, turbulent flows with some bed-load traction and turbidity currents also were effective mechanisms for the transport of sediment to proximal depositional sites on the slope. Modern counterparts of the Saint-Antonin Conglomerate are probably to be found on the leading edge of plates, rift margins and other tectonically-active coastal chain-bounded margins where coarse terrigenous sediments bypass narrow shelves and are transported directly on steep mobile slopes.


The Distributional Ecology and Zoogeographical Relationships of Stomatopod Crustacea from Pacific Costa Rica
Marjorie L. Reaka and Raymond B. Manning
iii, 29 pages
1980 (Date of Issue: 7 October 1980)
Number 7, Smithsonian Contributions to the Marine Sciences
DOI: 10.5479/si.01960768.7.1
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Twenty species of stomatopod crustaceans, primarily shallow-water forms, are recorded from Costa Rican localities. Earlier records for size, depth distribution, habitat, and latitudinal distribution are summarized for each species. Habitat use and co-occurrence of species are analyzed, and the zoogeographical relationships of East Pacific species are discussed.


Articulated Coralline Algae of the Gulf of California, Mexico, I: Amphiroa Lamouroux
James N. Norris and H. William Johansen
155 pages, 143 figures, 2 maps
1981 (Date of Issue: 7 October 1981)
Number 9, Smithsonian Contributions to the Marine Sciences
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Abstract

Amphiroa (Corallinaceae, Rhodophyta) is a tropical and subtropical genus of articulated coralline algae and is prominent in shallow waters of the Gulf of California, Mexico. Taxonomic and distributional investigations of Amphiroa from the Gulf have revealed the presence of seven species: A. beauvoisii Lamouroux, A. brevianceps Dawson, A. magdalensis Dawson, A. misakiensis Yendo, A. rigida Lamouroux, A. valonioides Yendo, and A. van-bosseae Lemoine. Only two of these species names are among the 16 taxa of Amphiroa previously reported from this body of water; all other names are now considered synonyms. Of the seven species in the Gulf of California, A. beauvoisii, A. misakiensis, A. valonioides and A. van-bosseae are common, while A. brevianceps, A. magdalensis, and A. rigida are rare and poorly known. None of these species is endemic to the Gulf, and four of them, A. beauvoisii, A. misakiensis, A. valonioides, and A. rigida, also occur in Japan.


The Marine Algae of Tunisia
Ernani G. Meñez and Arthur C. Mathieson
59 pages, 1 figure
1981 (Date of Issue: 19 October 1981)
Number 10, Smithsonian Contributions to the Marine Sciences
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A taxonomic study of the marine flora of Tunisia, North Africa, was conducted during 1973-1975. A total of 169 species, 37 Chlorophyta, 36 Phaeophyta, 96 Rhodophyta, of benthic marine algae were collected from 29 sites along the Mediterranean coast of Tunisia. Of the 169 species, 57 taxa are newly reported for the country. Of these, 16 represent genera previously unreported.


Sohm Abyssal Plain: Evaluating Proximal Sediment Provenance
Daniel Jean Stanley, Patrick T. Taylor, Harrison Sheng and Robert Stuckenrath
48 pages, 23 figures, 5 tables
1981 (Date of Issue: 23 October 1981)
Number 11, Smithsonian Contributions to the Marine Sciences
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Abstract

The southernmost part of the Sohm Abyssal Plain in the Northwest Atlantic Basin is geographically distal with respect to the major source of Quaternary terrigenous material transported from the Canadian Maritime Provinces. An assessment of the proportion of more locally introduced sediment relative to that derived from distal sources is based largely on size and compositional analyses of Quaternary piston core samples. These data are supplemented by radiocarbon dating of selected core samples, bottom photographs, conductivity-temperature-depth profiles, and seismic records.

The premises of the study are that (a) locally derived sediment should be most abundant near high-relief bathymetric features such as seamounts and abyssal hills, and (b) such material should contain enhanced proportions of reworked volcanic debris and alteration products. Core analyses reveal that the amounts of these are directly related to proximity of volcanic ocean-bottom features, and that a significant, although not total, amount of such volcanic materials recovered from cores are derived from submarine weathering of basalt. Associated with this assemblage are nannofossils, dating from the Quaternary to the Upper Cretaceous, reworked from older strata. This increased proportion of volcanic and related products and reworked faunas near seamounts and basement rises strongly implies that such topographic features continue to serve as major source terrains. Locally derived volcanic materials, however, are usually disseminated and masked on the Sohm Abyssal Plain, particularly in sectors receiving large amounts of terrigenous turbidites and biogenic suspensates, and/or undergoing reworking by bottom currents.

We propose that the volcanic fraction can serve as a useful index, or “yardstick,” to interpret the role of locally derived material in abyssal plain sedimentation. A sedimentation model is developed to illustrate the premise that as access to land-derived sources diminishes, the proportion of terrigenous components is reduced while pelagic and volcanic fractions are enhanced. Thus, sediment accumulating in abyssal plains almost totally isolated from terrigenous sources would comprise significant amounts of pelagic (including wind-blown) and volcanic components. Our model illustrates that even in an abyssal plain, such as the Sohm, which has had an important and direct access to abundant distally derived terrigenous sources, particularly during the Pliocene and Quaternary, the locally supplied reworked volcanic products account for a significant fraction of the total abyssal plain sediment fill.


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