Marine Geophysical Data Research Articles

Non-axial breaching of a rift valley: Evidence from the Lord Howe Rise and the southeastern Australian margin

Present models of continental breakup envisage the formation of a rift valley which undergoes a protracted period of tectonism and eventual seafloor spreading in the axial part of the rift valley. This results in evidence of pre-breakup tectonism on most Atlantic-type margins in the form of normal blockfaults beneath the continental slope. The southeastern margin of the Australian continent has an unusually steep continental slope and shows little evidence of tectonism associated with the rift valley stage of development. The margin was formed by separation of the Lord Howe Rise and Australia during a phase of seafloor spreading in the Tasman Sea which lasted from about 80 to 60 m.y. B.P. Marine geophysical data over the central Lord Howe Rise indicate a contrast between the western and eastern part of of this structure. The western part shows faulted, rough basement topography, disturbed overlying sediments, and a relatively quiet magnetic field. The eastern part shows a smooth basement surface, undisturbed overlying sediments, and a high-amplitude, high-frequency magnetic field. It is suggested that the whole of the pre-breakup rift valley remained attached to the Lord Howe Rise. This explains the absence of rift valley structures within the eastern continental margin of Australia and implies non-axial breaching along the western boundary fault of a pre-Tasman Sea rift valley.

New format for marine geophysical data described

A new exchange format for marine geophysical data has been developed by a special task force convened by a workshop of the Solar‐Terrestrial Data Center.

Structure and tectonic history of the eastern Panama Basin

New marine geophysical data allow the preparation of revised bathymetric and magnetic anomaly charts of the Panama Basin and demonstrate that the eastern part of the basin, between the fracture zone at long 83°W and the Colombian continental margin, was formed by highly asymmetric sea-floor spreading along the boundary of the Nazca and Cocos plates 27 to 8 m.y. B.P. Lineated magnetic anomalies recording this history are oriented approximately east-west. The oldest set of north-flank anomalies overlaps in age with those adjacent to the Grijalva scarp, south of the western Panama Basin, where they are oriented 065°. Younger anomalies (5C to 5) in the eastern basin are approximately parallel to anomalies of this age identified on the Carnegie platform and the flanks of the Costa Rica rift. The eastern basin now contains a pattern of fossil spreading centers (including the Malpelo rift) and transform faults (including the Yaquina graben) that were abandoned 8 m.y. B.P. by a shift in plate boundaries that transferred a large section of the Cocos plate to the Nazca plate. Cessation of Nazca-Cocos spreading east of long 83°W was heralded by a 3-m.y. deceleration of spreading on the eastern segments, which created rough topography and axial rift valleys typical of slow-spreading ridges. Westward jumping of the Nazca-Cocos-Caribbean triple junction rejuvenated the northern segment of the fracture zone at long 83°W, causing uplift of the adjacent Coiba Ridge. Recently, active transform faulting has jumped farther west, from the foot of the Coiba Ridge to the Panama fracture zone. Apart from changes in plate boundaries, the main event in the tectonic evolution of the region was initiation about 22 to 20 m.y. B.P. of the hot spot that created the Malpelo, Cocos, and Carnegie Ridges. Precursors of effusive ridge-building volcanism included major fracturing of the oceanic crust to the north of the present Malpelo Ridge. Both processes hamper identification of magnetic anomalies in the vicinity of the ridges. Our interpretation of the tectonic history is also incomplete in the easternmost parts of the basin, where data are insufficient; this impairs our interpretation of the adjacent continental geology in terms of changing interaction between oceanic and continental plates. The geologic history of the Isthmus of Panama is compatible with our application of the plate-tectonic model.

Plate tectonics synthesis: The displacements between Australia, New Zealand, and Antarctica since the Late Cretaceous

A comprehensive study of the last 75 m.y. of plate tectonics history has been undertaken for the region south of 30°S in the South Pacific, Southeast Indian Ocean and the Tasman Sea. Some aspects of plate boundary evolution have been clarified by our compilation and examination of available marine geophysical data. Reidentification of magnetic lineations in the southern Tasman basin shows that the controversial interval of subduction of Tasman basin crust along the east Australian margin that was previously proposed is no longer necessary. A comparison of Cenozoic magnetic lineations from both sides of the easternmost spreading segment of southeast Indian ridge indicates that a portion of the Indian plate younger than anomaly 10 (32 m.y.B.P.) is missing. We suggest that the missing crust was either subducted beneath or captured by the Pacific plate. Older lineations on the Indian plate out to about anomaly 21 have greater along-strike lengths than their counterparts on the Antarctic plate. The difference is due to an interval of crustal accretion at the Indian—Pacific plate boundary in the Early to Middle Tertiary. In the South Pacific, the Antarctic plate may not have extended northeast of the Eltanin fracture zone system prior to anomaly 29 (69 m.y.B.P.). Subduction of oceanic lithosphere was probably occurring beneath the Antarctic peninsula and eastern Ellsworth Land parts of the Antarctic plate at that time. Between anomaly-29 time and a major reorganization of plate boundaries in the Late Oligocene, plate interactions occurred in the central South Pacific between the Pacific, Farallon, Antarctic, Aluk and possibly a fifth plate. Spreading rate calculations for the Early Oligocene indicate that a simple three-plate system involving the Pacific, Farallon and Antarctic plates is difficult to maintain unless highly asymmetric spreading occurred at the Farallon—Antarctic boundary in the Early Oligocene. Further to the southeast in the Bellingshausen basin, spreading occurred along segments of the Antarctic—Aluk plate boundary beginning at about anomaly-29 time. Collisions of segments of this boundary with the trench along the Antarctic peninsula occurred in the Early and Middle Tertiary and resulted in the total disappearance of portions of Aluk plate. The collisions brought Antarctic—Aluk ridge segments into contact with Antarctic—Aluk trench segments with resulting stabilization of the Antarctic continental margin. From the magnetic lineations mapped in the southern oceans, we calculated new finite rotations which determine the relative positions of the Australian, New Zealand, and Antarctic continental fragments at 5–10 m.y. intervals during the last 75 m.y. For the New Zealand region, finite rotations calculated from magnetic lineations in the Tasman Sea and southwestern Pacific indicate that three plates were active during the Late Cretaceous to Paleocene. Previous workers have proposed that one of the three plate boundaries occurred southward between East and West Antarctica approximately along the trend of the Transantarctic mountains. As no direct geologic or geophysical evidence in Antarctica supports this proposal and since sea-floor spreading magnetic evidence shows that an active plate boundary passed through the New Zealand region after the Paleocene, we prefer to carry the required plate boundary northward. The Indian—Pacific poles of relative motion were always close to this boundary during the Cenozoic and thus corresponding evidence for plate interactions in New Zealand continental geology is generally variable and sometimes subtle.

MARINE GEOPHYSICAL DATA CATALOG–1975

School Science and MathematicsVolume 75, Issue 8 p. 728-728 MARINE GEOPHYSICAL DATA CATALOG–1975 First published: December 1975 https://doi.org/10.1111/j.1949-8594.1975.tb09898.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume75, Issue8December 1975Pages 728-728 RelatedInformation

Part 3. Present plate boundary and its evolution in the New Zealand region: Motion along the New Zealand Alpine Fault and a model for the formation of the Southern Alps

Analysis of marine geophysical data by Falconer, Geddes and Christoffel shows that the present position of the pole of rotation for motion between the Pacific and Indian Plates differs from the average pole for the past 10 million years.

The evolution of the China Basin and the mesozoic paleogeography of Borneo

Marine geophysical data from the China Basin and geological and geophysical data from the surrounding land areas indicate at least three stages in the tectonic evolution of the China Basin. The first stage was a north-south extension associated with the formation of oceanic crust beneath the China Basin during middle Mesozoic time. The second and third stages of east-west compression are associated with the closing of the China Basin. Closing of the basin during the Tertiary involved the northwestward movement of Borneo toward Asia with underthrusting along the Palawan Trough. Presently Luzon Island is approaching Asia with underthrusting along the Manila Trench. A simple paleogeographic reconstruction for the early Mesozoic Era requires Borneo to have been adjacent to mainland China and Hainan. The opening of the basin can then be explained by a simple rotation of a small plate, which included Borneo and Natuna Islands, away from mainland China about a pole of rotation located at Latitude 13.0°N, Longitude 44.0°E.

Geophysical Studies in the Angola Diapir Field

Research Article| July 01, 1972 Geophysical Studies in the Angola Diapir Field RICHARD P VON HERZEN; RICHARD P VON HERZEN Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543 Search for other works by this author on: GSW Google Scholar HARTLEY HOSKINS; HARTLEY HOSKINS Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543 Search for other works by this author on: GSW Google Scholar TJEERD H VAN ANDEL TJEERD H VAN ANDEL Department of Oceanography, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar Author and Article Information RICHARD P VON HERZEN Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543 HARTLEY HOSKINS Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543 TJEERD H VAN ANDEL Department of Oceanography, Oregon State University, Corvallis, Oregon 97331 Publisher: Geological Society of America Received: 01 Nov 1971 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1972, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1972) 83 (7): 1901–1910. https://doi.org/10.1130/0016-7606(1972)83[1901:GSITAD]2.0.CO;2 Article history Received: 01 Nov 1971 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation RICHARD P VON HERZEN, HARTLEY HOSKINS, TJEERD H VAN ANDEL; Geophysical Studies in the Angola Diapir Field. GSA Bulletin 1972;; 83 (7): 1901–1910. doi: https://doi.org/10.1130/0016-7606(1972)83[1901:GSITAD]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Marine geophysical data on the continental slope west of Angola, Africa, indicate a large (50,000 km2) diapir field. Heat-flow values on the crests of the diapiric structures are systematically 2 to 3 times larger than those measured between these structures. A steady-state model of thermal conductivity contrasts, based on a detailed survey over the diapirs, strongly suggests that the cores of the diapirs are salt. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Earth-Science Studies of a Nuclear Test Area in the Western Aleutian Islands, Alaska: An Interim Summary of Results

Recent multi-disciplinary studies by the U. S. Geological Survey conducted on and near Amchitka Island in the Aleutians have contributed much to a better understanding of the geologic, hydrologic, and tectonic environment of the island as an underground nuclear test site. The work included geologic mapping, isotopic dating, deep drilling, geophysical surveys, hydrologic investigations, and post-test effects examinations. Three distinct volcanic episodes have been distinguished and dated. A general volcanotectonic history of the arc is proposed. The islands in the vicinity of Amchitka have apparently been stable tectonically in the late Pleistocene and Holocene. Most of the gravity and magnetic data can be interpreted in terms of known structure and rock distribution. Marine geophysical data tend to confirm structural stability of the insular area and indicate a scarcity of sedimentary material in the insular slopes and shelf. Geologic effects of underground tests have been minor. (auth)

The transition from continental to oceanic crust

Abstract A considerable body of data has been collected on the continental margins of the world but the greater part of these data are concentrated in a few areas and the remaining areas have received only limited attention. This is especially true of data dealing with the deep-seated structure. There has been a tendency to group the margins into Atlantic and Pacific types, characterized respectively by truncation of pre-Mesozoic structures or by a coincidence between the margins and Meso-Cenozoic orogenic belts but this classification now appears to be too simple. It would seem more appropriate to relate the margins to the manner of their development than to area or time. Characteristics of the deep structure of the transition zones have been determined from seismic refraction (D.D.S.) studies and it is obvious that their development is related to deep-seated physico-chemical changes. There is, however, sharp disagreement about the relative importance of horizontal and vertical movements in producing the features that can be observed today. Evidence of large scale subsidence is recorded in the sediments of present and fossil continental margins but compelling arguments for major horizontal movements can be raised on the basis of recent data from the ocean basins. Resolution of this problem will depend upon better correlation of marine and terrestrial geological and geophysical data and determination of the age and method of formation of the ocean basins.

Deep-Sea Drilling into the Challenger Knoll, Central Gulf of Mexico

During the recent pioneering cruise of a deep-sea coring project, a series of holes was drilled into the deep floor of the Gulf of Mexico and the western North Atlantic. One of the holes, in the Sigsbee Knolls area of the central Gulf of Mexico, encountered salt-dome caprock saturated with oil, gas, and sulfur. The objectives of this coring project are scientific and the discovery of petroleum was not an intended part of the program, even though the possibility had been recognized. The results of drilling into the Challenger Knoll indicate that the Sigsbee Knolls and adjacent buried domes are diapirs derived from a mid-Mesozoic salt deposit, comparable in age and lithology with other major evaporite sequences within the Gulf of Mexico area. Marine geophysical data show that these diapirs are part of a belt which extends southwest into the saline basin of the Isthmus of Tehuantepec. Cores of caprock, recovered from more than 12,000 ft below sea level, contained a typical salt-dome caprock mineral assemblage of calcite, gypsum, and free sulfur (up to 19 percent). The petroleum is sulfur-rich and of low gravity, and geochemical data indicate that these hydrocarbons are immature, of fairly young age, and derived from marine organic material. Residual mineral assemblages--including quartz crystals--are comparable with those found in caprock elsewhere in the Gulf of Mexico region; similar quartz crystals are common in the mid-Mesozoic Louann Salt. All sediments above the caprock are pelagic clays and calcareous organic oozes of late Tertiary age (late Miocene and younger). The presence of these sediment types indicates that the Challenger Knoll has been topographically above the surrounding sea floor at least since late Miocene time. In contrast, the turbidite-rich sequence cored beneath the adjacent abyssal plain shows that pelagic sediments constitute only a fourth to less than half the total late Miocene and younger section. The late Cenozoic pelagic deposits of Challenger Knoll and the turbidites appear to reflect major geologic events and significant changes in sediment provenance within the land area surrounding the Gulf of Mexico. The regional problem which probably will be debated most earnestly as a result of the Challenger Knoll coring is whether the salt underlying the knoll was deposited originally in a deep-sea environment, or on a crust which once was much shallower. This problem is of considerable geologic importance, and it can now be approached with a background of firm data.

Some observed results of oceanic turbulence : Nan'niti Tosio, 1964. In: Studies on Oceanography dedicated to Professor Hidaka in Commemoration of his Sixtieth Birthday, 211–215

Marine geophysical data, including SEA BEAM bathymetry, HAWAII MR1 sidescan, and seismic reflection profiles, along with recent robot submersible observations and samples, were acquired over the offshore continuation of the mobile Kilauea volcano south flank. This slope comprises the three active hot spot volcanoes Mauna Loa, Kilauea, and Loihi seamount and is the locus of the Hawaiian hot spot. The south flank is the site of frequent low-intensity seismicity as well as episodic large-magnitude earthquakes. Its sub-aerial portion creeps seaward at a rate of approximately 10 cm/year. The Hilina slump is the only large submarine landslide in the Hawaiian Archipelago thought to be active, and this study is one of the first to more highly resolve submarine slide features there. The slump is classified into four distinct zones from nearshore to the island’s base. Estimates of size based on these data indicate a slumped area of 2100 km2 and a volume of 10,000–12,000 km3, equivalent to about 10% of the entire island edifice. The overall picture gained from these data sets is one of mass wasting of the neovolcanic terrain as it builds upward and seaward, though reinforcement by young and pre-Hawaii seamounts adjacent to the pedestal is apparent. Extensive lava delta deposits are formed by hyaloclastites and detritus from recent lava flows into the sea. These deposits dominate the upper submarine slope offshore of Kilauea, with pillow breccia revealed at mid-depths. Along the lower flanks, massive outcrops of volcanically derived sedimentary rocks were found underlying Kilauea, thus necessitating a rethinking of previous models of volcanic island development. The morphologic and structural evolutionary model for Kilauea volcano and the Hilina slump proposed here attempts to incorporate this revelation. A hazard assessment for the Hilina slump is presented where it is suggested that displacement of the south flank to date has been restrained by a still developing northeast lateral submarine boundary. When it does fully mature, the south flank may be more subject to land slips triggered by large, long duration earthquakes and thus Kilauea may undergo more frequent episodes of failure with increased displacements.

Carbonate deposits and paleoclimatic implications in the northeast Pacific Ocean : Nayudu Y. R., 1964. Science, 146 (3643): 515–517

Marine geophysical data, including SEA BEAM bathymetry, HAWAII MR1 sidescan, and seismic reflection profiles, along with recent robot submersible observations and samples, were acquired over the offshore continuation of the mobile Kilauea volcano south flank. This slope comprises the three active hot spot volcanoes Mauna Loa, Kilauea, and Loihi seamount and is the locus of the Hawaiian hot spot. The south flank is the site of frequent low-intensity seismicity as well as episodic large-magnitude earthquakes. Its sub-aerial portion creeps seaward at a rate of approximately 10 cm/year. The Hilina slump is the only large submarine landslide in the Hawaiian Archipelago thought to be active, and this study is one of the first to more highly resolve submarine slide features there. The slump is classified into four distinct zones from nearshore to the island’s base. Estimates of size based on these data indicate a slumped area of 2100 km2 and a volume of 10,000–12,000 km3, equivalent to about 10% of the entire island edifice. The overall picture gained from these data sets is one of mass wasting of the neovolcanic terrain as it builds upward and seaward, though reinforcement by young and pre-Hawaii seamounts adjacent to the pedestal is apparent. Extensive lava delta deposits are formed by hyaloclastites and detritus from recent lava flows into the sea. These deposits dominate the upper submarine slope offshore of Kilauea, with pillow breccia revealed at mid-depths. Along the lower flanks, massive outcrops of volcanically derived sedimentary rocks were found underlying Kilauea, thus necessitating a rethinking of previous models of volcanic island development. The morphologic and structural evolutionary model for Kilauea volcano and the Hilina slump proposed here attempts to incorporate this revelation. A hazard assessment for the Hilina slump is presented where it is suggested that displacement of the south flank to date has been restrained by a still developing northeast lateral submarine boundary. When it does fully mature, the south flank may be more subject to land slips triggered by large, long duration earthquakes and thus Kilauea may undergo more frequent episodes of failure with increased displacements.