DOCSLIB.ORG

51. Breakup and Seafloor Spreading Between the Kerguelen Plateau-Labuan Basin and the Broken Ridge-Diamantina Zone1

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
51. Breakup and Seafloor Spreading Between the Kerguelen Plateau-Labuan Basin and the Broken Ridge-Diamantina Zone1 Wise, S. W., Jr., Schlich, R., et al., 1992 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 120 51. BREAKUP AND SEAFLOOR SPREADING BETWEEN THE KERGUELEN PLATEAU-LABUAN BASIN AND THE BROKEN RIDGE-DIAMANTINA ZONE1 Marc Munschy,2 Jerome Dyment,2 Marie Odile Boulanger,2 Daniel Boulanger,2 Jean Daniel Tissot,2 Roland Schlich,2 Yair Rotstein,2,3 and Millard F. Coffin4 ABSTRACT Using all available geophysical data and an interactive graphic software, we determined the structural scheme of the Australian-Antarctic and South Australian basins between the Kerguelen Plateau and Broken Ridge. Four JOIDES Resolution transit lines between Australia and the Kerguelen Plateau were used to study the detailed pattern of seafloor spreading at the Southeast Indian Ridge and the breakup history between the Kerguelen Plateau and Broken Ridge. The development of rifting between the Kerguelen Plateau-Labuan Basin and the Broken Ridge-Diamantina Zone, and the evolution of the Southeast Indian Ridge can be summarized as follows: 1. From 96 to 46 Ma, slow spreading occurred between Antarctica and Australia; the Kerguelen Plateau, Labuan Basin, and Diamantina Zone stretched at 88-87 Ma and 69-66 Ma. 2. From 46 to 43 Ma, the breakup between the Southern Kerguelen Plateau and the Diamantina Zone propagated westward at a velocity of about 300 km/m.y. The breakup between the Northern Kerguelen Plateau and Broken Ridge occurred between 43.8 and 42.9 Ma. 3. After 43 Ma, volcanic activity developed on the Northern Kerguelen Plateau and at the southern end of the Ninetyeast Ridge. Lava flows obscured the boundaries of the Northern Kerguelen Plateau north of 48°S and of the Ninetyeast Ridge south of 32°S, covering part of the newly created oceanic crust. Since 43 Ma, the Southeast Indian Ridge has manifested a typical intermediate spreading rate (25-45 km/m.y.). INTRODUCTION guelen Plateau and Broken Ridge would overlap if Broken Ridge were rotated using the poles of opening determined by Located in the southern Indian Ocean, the Kerguelen Weissel and Hayes (1972) between Australia and Antarctica. Plateau and Broken Ridge are a conjugate pair of ocean Such a mismatch problem was resolved by assuming that the plateaus. They are separated by the Australian-Antarctic Northern Kerguelen Plateau is younger than 45 Ma, and Basin and the South Australian Basin formed at the Southeast numerous authors have, more or less, followed this hypothe- Indian Ridge (Fig. 1). Since 1967, many authors have inter- sis (Luyendyk and Rennick, 1977; Norton and Molnar, 1977; preted the magnetic anomaly pattern associated with this Norton and Sclater, 1979; Goslin, 1981; Schlich, 1982). Piston spreading center between Saint Paul and Amsterdam islands core and dredge samples, however, have shown that the part and about 105°E (Schlich and Patriat, 1967, 1971; Le Pichon of the Northern Kerguelen Plateau located south of Kerguelen and Heirtzler, 1968; McKenzie and Sclater, 1971; Schlich, Island is at least 100 Ma (Fröhlich et al., 1983; Wicquart, 1975, 1982; Houtz et al., 1977; Li, 1988; Royer and Schlich, 1983). 1988; Royer and Sandwell, 1989). The most detailed tectonic Furthermore, lithostratigraphic (Wicquart and Fröhlich, chart of this area (Royer and Sandwell, 1989), however, is 1986) and seismic stratigraphic (Munschy and Schlich, 1987) based on <IOO magnetic anomaly identifications; only five studies on the Kerguelen Plateau, as well as Ocean Drilling reversal boundaries were selected for plate reconstructions. Program (ODP) results on Broken Ridge (Peirce, Weissel, et Until recently, the breakup history between the Kerguelen al., 1989; Weissel, Peirce, et al., 1991) suggest that the Plateau and Broken Ridge was a matter of controversy. The breakup between the Northern Kerguelen Plateau and Broken original reconstructions of Australia and Antarctica (McKen- Ridge occurred at 45-42 Ma. East of the Southern Kerguelen zie and Sclater, 1971; Weissel and Hayes, 1972) proposed Plateau, Anomalies 17 and 18 (41 and 42 Ma) have been clearly separation of the two continents at Anomaly 22 (52 Ma on the identified (Le Pichon and Heirtzler, 1968; Houtz et al., 1977). 1985 Berggren et al. geomagnetic reversal time scale). Houtz However, these anomalies lie several hundred kilometers east et al. (1977) showed that, before 45 Ma, the Northern Ker- of the Southern Kerguelen' Plateau eastern margin. Coffin et al. (1986) and Rotstein et al. (1991) have studied the area located between the eastern margin of the Southern Kerguelen 1 Wise, S. W., Jr., Schlich, R., et al., 1992. Proc. ODP, Sci. Results, 120: Plateau and the oceanic crust created since Anomaly 18 (42 College Station, TX (Ocean Drilling Program). Ma) at the axis of the Southeast Indian Ridge. This area 2 Institut de Physique du Globe, Université Louis Pasteur, Laboratoire de Géophysique Marine (CNRS URA 323), 5 rue Rene Descartes, 67084 Stras- corresponds to the Labuan Basin, a deep Cretaceous basin, bourg Cedex, France. bounded to the north by the Williams Ridge, a northwest- 3 Also at Institute for Petroleum Research and Geophysics, P. O.Box 2286, southeast elongated bathymetric feature. Holon 58120, Israel. Recently, Royer and Sandwell (1989) proposed a new 4 Bureau of Mineral Resources, Geology and Geophysics, G.P.O. Box 378, Canberra ACT 2601, Australia (present address: Institute for Geophysics, tectonic chart for the area located east of the Kerguelen University of Texas at Austin, 8701 Mopac Boulevard, Austin, TX 78759-8345, Plateau, based on available magnetic identifications and an U.S.A.). interpretation of GEOSAT altimetric data. Their reconstruc- 931 M. MUNSCHY ET AL. Australian - Antarctic Basin Figure 1. Location of the main bathymetric features in the Southeast Indian Ocean, outlined by the 3000-m isobath, and ship tracks of the JOIDES Resolution during Leg 120. tions at Anomalies 13 and 18 resolve the mismatch problem STRUCTURE AND EVOLUTION OF THE between the Kerguelen Plateau and Broken Ridge. They SOUTHEAST INDIAN RIDGE BETWEEN THE propose that the northwesternmost part of the Kerguelen KERGUELEN PLATEAU AND BROKEN RIDGE Plateau, which includes Kerguelen Island, is underlain by late Eocene/early Oligocene oceanic crust. However, this work Using all available marine geophysical data and an inter- was based on only a few anomaly identifications (three Anom- active graphic software, we identified 2500 magnetic picks on aly 18 picks and eight Anomaly 13 picks), and the seismic the southwestern flank of the Southeast Indian Ridge and 2100 profiles across the eastern margin of the Kerguelen Plateau magnetic picks on its northeastern flank and have derived a were not used. Such profiles are crucial, especially the ones detailed tectonic chart. For this study, all recognized reversals cutting the boundary that separates the Labuan Basin and the of the geomagnetic field on all magnetic anomaly profiles were crust created at the axis of the Southeast Indian Ridge. picked (146 reversals of the geomagnetic field since 44.5 Ma). This paper considers all available magnetic profiles located To simplify discussion and presentation of the figures, we east of the Kerguelen Plateau and uses, in particular, the four selected 53 isochrons or magnetic lineations on each flank of transit lines acquired during Leg 120 (Fig. 1). A detailed the Southeast Indian Ridge (Table 1). We used the nomencla- interpretation with accurate spreading rates and directions is ture of Berggren et al. (1985) to identify the magnetic linea- proposed for the Southeast Indian Ridge since the middle tions and the corresponding magnetic picks; the letters "y" Eocene. Magnetic picks on both flanks of the Southeast Indian and "o" refer to the younger and older reversals, respec- Ridge are used to define a detailed tectonic chart. Combining tively, in a normal polarity interval. the magnetic anomaly identifications with the interpretation of seismic profiles crossing the eastern boundary of the Ker- Detailed Analysis of Compartment L guelen Plateau provides additional constraints for the breakup Underway geophysical data, including magnetics, were history of the Kerguelen Plateau. recorded across the Southeast Indian Ridge during four 932 SEAFLOOR SPREADING Table 1. Geomagnetic reversal time scale between Anomalies 1 and 19. Normal Normal Normal polarity polarity polarity interval interval interval Anomaly (Ma) Anomaly (Ma) Anomaly (Ma) 1 0-0.73 12.58-12.62 8 26.86-26.93 0.91-0.98 5AA 12.83-13.01 8 27.01-27.74 2 1.66-1.88 5AB 13.20-13.46 9 28.15-28.74 2A 2.47-2.92 SAC 13.69-14.08 9 28.80-29.21 2A 2.99-3.08 5AD 14.20-14.66 10 29.73-30.03 2A 3.18-3.40 5B 14.87-14.96 10 30.09-30.33 3 3.88-3.97 5B 15.13-15.27 11 31.23-31.58 3 4.10-4.24 5C 16.22-16.52 11 31.64-32.06 3 4.40-4.47 5C 16.56-16.73 12 32.46-32.90 3 4.57-4.77 5C 16.80-16.98 13 35.29-35.47 3A 5.35-5.53 5D 17.57-17.90 13 35.57-35.87 3A 5.68-5.89 5D 18.12-18.14 15 37.24-37.46 6.37-6.50 5E 18.56-19.09 15 37.48-37.68 4 6.70-6.78 6 19.35-20.45 16 38.10-38.34 4 6.85-7.28 6A 20.88-21.16 16 38.50-38.79 4 7.35-7.41 6A 21.38-21.71 16 38.83-39.24 4A 7.90-8.21 6AA 21.90-22.06 17 39.53-40.43 4A 8.41-8.50 6AA 22.25-22.35 17 40.50-40.70 8.71-8.80 6B 22.57-22.97 17 40.77-41.11 5 8.92-10.42 6C 23.27-23.44 18 41.29-41.73 10.54-10.59 6C 23.55-23.79 18 41.80-42.23 11.03-11.09 6C 24.04-24.21 18 42.30-42.73 5A 11.55-11.73 7 25.50-25.60 19 43.60-44.06 5A 11.86-12.12 7 25.67-25.97 12.46-12.49 7A 26.38-26.56 Notes: Time scale after Berggren et al.
Load more

Recommended publications
  • Insights on the Indian Ocean Tectonics and Geophysics Supported by GMT Polina Lemenkova
    Insights on the Indian Ocean tectonics and geophysics supported by GMT Polina Lemenkova To cite this version: Polina Lemenkova. Insights on the Indian Ocean tectonics and geophysics supported by GMT. Riscuri si Catastrofe, ”Babes-Bolyai” University from Cluj-Napoca, Faculty of Geography, 2020, 27 (2), pp.67- 83. 10.24193/RCJ2020_12. hal-03033533 HAL Id: hal-03033533 https://hal.archives-ouvertes.fr/hal-03033533 Submitted on 1 Dec 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Distributed under a Creative Commons Attribution| 4.0 International License Riscuri și catastrofe, an XX, vol, 27 nr. 2/2020 INSIGHTS ON THE INDIAN OCEAN TECTONICS AND GEOPHYSICS SUPPORTED BY GMT POLINA LEMENKOVA1 Abstract. Insights on the Indian Ocean Tectonics and Geophysics Supported by GMT. This paper presented analyzed and summarized data on geological and geophysical settings about the tectonics and geological structure of the seafloor of the Indian Ocean by thematic visualization of the topographic, geophysical and geo- logical data. The seafloor topography of the Indian Ocean is very complex which includes underwater hills, isolated mountains, underwater canyons, abyssal and ac- cumulative plains, trenches. Complex geological settings explain seismic activity, repetitive earthquakes, and tsunami.
    [Show full text]
  • CHAPTER 2 Aseismic Ridges of the Northeastern Indian Ocean
    CHAPTER 2 Aseismic ridges of the northeastern Indian Ocean 2.1 Evolution of the Indian Ocean 2.2 Major Aseismic Ridges 2.2.1 The Ninetyeast Ridge 2.2.2 The Chagos-Laccadive Ridge 2.2.3 The 85°E Ridge 2.2.4 The Comorin Ridge 2.2.5 The Broken Ridge 2.3 Other Major Structural Features 2.3.1 The Kerguelen Plateau 2.3.2 The Elan Bank 2.3.3 The Afanasy Nikitin seamount Chapter 2 Aseismic ridges of the northeastern Indian Ocean 2.1 Evolution of the Indian Ocean The initiation of the Indian Ocean commenced with the breakup of the Gondwanaland super-continent into two groups of continental masses during the Mesozoic period (Norton and Sclater, 1979). The first split of the Gondwanaland may possibly have associated with the Karoo mega-plume (Lawver and Gahagan, 1998). Followed by this rifting phase, during the late Jurassic, the Mozambique and Somali basins have formed by seafloor spreading activity of series of east-west trending ridge segments. Thus, the Gondwanaland super-continent divided into western and eastern continental blocks. The Western Gondwanaland consisted of Africa, Arabia and South America, whereas the East Gondwanaland consisted of Antarctica, Australia, New Zeeland, Seychelles, Madagascar and India-Sri Lanka (Figure 2.1). After initial break-up, the East Gondwanaland moved southwards from the West Gondwanaland and led to gradual enlargement of the intervening seaways between them (Bhattacharya and Chaubey, 2001). Both West and East Gondwanaland masses have further sub-divided during the Cretaceous period. Approximate reconstructions of continental masses of the Gondwanaland from Jurassic to Present illustrating the aforesaid rifting events are shown in Figure 2.1 (Royer et al., 1992).
    [Show full text]
  • 38. Tectonic Constraints on the Hot-Spot Formation of Ninetyeast Ridge1
    Weissel, J., Peirce, J., Taylor, E., Alt, J., et al. 1991 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 121 38. TECTONIC CONSTRAINTS ON THE HOT-SPOT FORMATION OF NINETYEAST RIDGE1 Jean-Yves Royer,2 John W. Peirce,3 and Jeffrey K. Weissel4 ABSTRACT This paper examines the constraints on the tectonic setting of Ninetyeast Ridge, based on a compilation of bathymetric and magnetic data from the basins surrounding Ninetyeast Ridge in the Indian Ocean that includes the magnetic profiles collected under way during ODP Leg 121. Magnetic data in the Central Indian Basin demonstrate that the spreading center immediately west of Ninetyeast Ridge jumped to the south by a total amount of 11° between 68 and 46 Ma, implying that parts of the mirror image of Ninetyeast Ridge on the Antarctic plate were transferred onto the Indian plate. The obliquity of Ninetyeast Ridge relative to the fracture zone pattern and the occurrence of an Eocene extinct spreading axis in the Wharton Basin suggest that the northern part of Ninetyeast Ridge was emplaced by intraplate volcanism on the Indian plate, whereas the middle and southern parts of the ridge were emplaced along transform plate boundaries. The northward drift of the Indian plate over a single hot spot is the most plausible origin for Ninetyeast Ridge. Based on a recent kinematic model for the relative motions of the Indian, Antarctic, and Australian plates, we present a simple model that reconciles most of the available observations for Ninetyeast Ridge: Paleomagnetism, distribution of basement ages, geochemistry, and geometry. In addition, the model predicts a slow westward migration of the Kerguelen/Ninetyeast hot spot with respect to the Antarctic and Australian plates between the Late Cretaceous and early Oligocene (84 to 36 Ma).
    [Show full text]
  • A Global Review and Digital Database of Large-Scale Extinct Spreading Centers GEOSPHERE
    Research Paper GEOSPHERE A global review and digital database of large-scale extinct GEOSPHERE; v. 13, no. 3 spreading centers doi:10.1130/GES01379.1 Sarah J. MacLeod, Simon E. Williams, Kara J. Matthews, R. Dietmar Müller, and Xiaodong Qin EarthByte Group, School of Geosciences, University of Sydney, Camperdown, New South Wales 2006, Australia 9 figures; 4 tables; 2 supplemental files CORRESPONDENCE: sarah.macleod@ sydney ABSTRACT into which proposed locations are more likely to have been former spreading .edu .au centers, and our analysis further leads to the discovery of several previously Extinct mid-ocean ridges record past plate boundary reorganizations, and unidentified structures in the south of the West Philippine Basin that likely CITATION: MacLeod, S.J., Williams, S.E., Matthews, K.J., Müller, R.D., and Qin, X.D., 2017, A global review identifying their locations is crucial to developing a better understanding of represent extinct ridges and a possible extinct ridge in the western South At- and digital database of large-scale extinct spread- the drivers of plate tectonics and oceanic crustal accretion. Frequently, extinct lantic. We make available our global compilation of data and analyses of indi- ing centers: Geosphere, v. 13, no. 3, p. 911–949, ridges cannot be easily identified within existing geophysical data sets, and vidual ridges in a global extinct ridge data set at the GPlates Portal webpage1. doi:10.1130/GES01379.1. there are many controversial examples that are poorly constrained. We ana- lyze the axial morphology and gravity signal of 29 well-constrained, global, Received 17 June 2016 Revision received 29 November 2016 large-scale extinct ridges that are digitized from global data sets, to describe INTRODUCTION Accepted 15 March 2017 their key characteristics.
    [Show full text]
  • Heat Flow from the Southeast Indian Ridge Flanks Between 80°E and 140°E: Data Review and Analysis L
    Heat flow from the Southeast Indian Ridge flanks between 80E and 140E: Data review and analysis L. G´eli,T. C. Lee, J. R. Cochran, J. Francheteau, D. Abbott, C. Labails, D. Appriou To cite this version: L. G´eli,T. C. Lee, J. R. Cochran, J. Francheteau, D. Abbott, et al.. Heat flow from the Southeast Indian Ridge flanks between 80E and 140E: Data review and analysis. Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2008, 113, pp.B01101. <10.1029/2007JB005001>. <insu-00267287> HAL Id: insu-00267287 https://hal-insu.archives-ouvertes.fr/insu-00267287 Submitted on 15 Feb 2011 HAL is a multi-disciplinary open access L'archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destin´eeau d´ep^otet `ala diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publi´esou non, lished or not. The documents may come from ´emanant des ´etablissements d'enseignement et de teaching and research institutions in France or recherche fran¸caisou ´etrangers,des laboratoires abroad, or from public or private research centers. publics ou priv´es. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, B01101, doi:10.1029/2007JB005001, 2008 Click Here for Full Article Heat flow from the Southeast Indian Ridge flanks between 80°E and 140°E: Data review and analysis L. Ge´li,1 T. C. Lee,2 J. R. Cochran,3 J. Francheteau,4 D. Abbott,3 C. Labails,1 and D. Appriou1 Received 18 February 2007; revised 21 May 2007; accepted 20 September 2007; published 5 January 2008.
    [Show full text]
  • Slow Spreading Ridges of the Indian Ocean: an Overview of Marine Geophysical Investigations K
    J. Ind. Geophys.Slow Union Spreading ( April Ridges 2015 of the ) Indian Ocean: An Overview of Marine Geophysical Investigations v.19, no.2, pp:137-159 Slow Spreading Ridges of the Indian Ocean: An Overview of Marine Geophysical Investigations K. A. Kamesh Raju*, Abhay V. Mudholkar, Kiranmai Samudrala CSIR-National Institute of Oceanography, Dona Paula, Goa – 403004, India *Corresponding author: [email protected] ABSTRACT Sparse and non-availability of high resolution geophysical data hindered the delineation of accurate morphology, structural configuration, tectonism and spreading history of Carlsberg Ridge (CR) and Central Indian Ridges (CIR) in the Indian Ocean between Owen fracture zone at about 10oN, and the Rodriguez Triple Junction at ~25oS. Analysis of available multibeam bathymetry, magnetic, gravity, seabed sampling on the ridge crest, and selected water column data suggest that even with similar slow spreading history the segmentation significantly differ over the CR and CIR ridge systems. Topography, magnetic and gravity signatures indicate non-transform discontinuity over CR and suggest that it has relatively slower spreading history than CIR. Magmatic and less magmatic events characterize CR and CIR respectively and well defined oceanic core complex (OCC) are confined only to segments of the CIR. The mantle Bouguer anomaly signatures over the ridges suggest crustal accretion and pattern of localized magnetic anomalies indicate zones of high magnetization coinciding with the axial volcanic ridges. Geophysical investigations /
    [Show full text]
  • UTIGTR 0093 OCR.Pdf (2.307Mb)
    PALEOCEANOGRAPHIC MAPPING PROJECT PROGRESS REPORT No. 41 - 0888 Evolution of the Eastern Indian Ocean Since the Late Cretaceous Constraints from Geosat Altimetry by Jean-Yves Royer and Dave Sandwell Evolution of the Eastern Indian Ocean Since the Late Cretaceous: Constraints from G EOSAT Altimetry Jean-Yves Royer and David T. Sandwell Institute for Geophysics University of Texas at Austin 8701 MOPAC Boulevard Austin TX 78759-8345 Draft#4 Submitted to the Journal of Geophysical Research May 1988 Royer and Sandwell: Evolution of the Eastern Indian Ocean Since the Late Cretaceous. 2 Abstract We propose a new model for the tectonic evolution of the Eastern Indian Ocean from the Late Cretaceous to the t»:esent. Two types of data are used to improve previously-published reconstructions. First, reinterpreted seafloor magnetic anomahes, between Australia and Antarctica and in the Wharton basin, provide new constraints on spreading rates and the timing of major reorganizations. Second, vertical deflection profiles (i.e. horizontal gravity anomaly), derived from 22 repeat cycles of GEOSAT altimeter data, reveal the tectonic fabric associated with fracture zones. These new GEOSAT data provide tight constraints on paleo-spreading directions. For example, three prominent fracture zones can be traced from south of Tasmania to the George V Basin, Antarctica providing an important constraint on the relative motions of Australia and Antarctica through the Late Eocene. In addition, the GEOSAT profiles are used to locate the conjugate continental margins and continent-ocean boundaries of Australia and Antarctica, as well as the conjugate rifted margins of Kerguelen Plateau and Broken Ridge. Based on a compilation of magnetic anomaly data from the Crozet Basin, the Central Indian Basin, the WhllrtOn Basin and the Australian-Antarctic Basin, ten plate tectonic reconstructions are proposed.
    [Show full text]
  • Mapping Absolute Migration of Global Mid-Ocean Ridges Since 80 Ma to Present
    LETTER Earth Planets Space, 59, 1061–1066, 2007 Mapping absolute migration of global mid-ocean ridges since 80 Ma to Present Desiderius C. P. Masalu University of Dar Es Salaam, Institute of Marine Sciences, PO Box 668, Zanzibar, Tanzania (Received October 27, 2006; Revised June 8, 2007; Accepted August 2, 2007; Online published September 28, 2007) We have computed and mapped the absolute migration of global mid-ocean ridges in the past 80 m.y. and found that ridges have migrated substantially during that period. Presently, the faster-migrating ridges are Pacific-Antarctic, Central Indian, Southeast Indian, Juan de Fuca, Pacific-Nazca, Antarctic-Nazca and Australia- Antarctic ridges which migrate between 3.3 and 5.5 cm/yr. The slower-migrating ridges are Mid-Atlantic and Southwest Indian ridges which migrate between 0.3 and 2.0 cm/yr. Comparing these results with mantle tomog- raphy and geochemistry suggests that slower-migrating ridges have deeper depth of origin than faster-migrating ridges, implying a correlation between migration velocity and depth of origin of ridges. The reconstructed South- western Indian ridge (near 44◦E) between 60 Ma and Present, lies atop reconstructed Central Indian ridge between 80 and 50 Ma, and the present-day Antarctic-Nazca or (Chile) ridge lies atop the reconstructed East Pacific Rise at 70 Ma. Furthermore, the South Mid Atlantic Ridge and the East Pacific Rise near 10◦S appear to have been stationary relative to the mantle for the last 80 m.y. These observations suggest that different portions of the mantle have undergone different recycling history, and may explain the origin of mantle heterogeneities.
    [Show full text]
  • An Ultraslow-Spreading Class of Ocean Ridge
    articles An ultraslow-spreading class of ocean ridge Henry J. B. Dick, Jian Lin & Hans Schouten Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA ........................................................................................................................................................................................................................... New investigations of the Southwest Indian and Arctic ridges reveal an ultraslow-spreading class of ocean ridge that is characterized by intermittent volcanism and a lack of transform faults. We find that the mantle beneath such ridges is emplaced continuously to the seafloor over large regions. The differences between ultraslow- and slow-spreading ridges are as great as those between slow- and fast-spreading ridges. The ultraslow-spreading ridges usually form at full spreading rates less than about 12 mm yr21, though their characteristics are commonly found at rates up to approximately 20 mm yr21. The ultraslow-spreading ridges consist of linked magmatic and amagmatic accretionary ridge segments. The amagmatic segments are a previously unrecognized class of accretionary plate boundary structure and can assume any orientation, with angles relative to the spreading direction ranging from orthogonal to acute. These amagmatic segments sometimes coexist with magmatic ridge segments for millions of years to form stable plate boundaries, or may displace or be displaced by transforms and magmatic ridge segments as spreading rate, mantle thermal structure and ridge
    [Show full text]
  • Glacial Heterogeneity in Southern Ocean Carbon Storage Abated by Fast South Indian Deglacial Carbon Release ✉ Julia Gottschalk 1,2 , Elisabeth Michel 3, Lena M
    ARTICLE https://doi.org/10.1038/s41467-020-20034-1 OPEN Glacial heterogeneity in Southern Ocean carbon storage abated by fast South Indian deglacial carbon release ✉ Julia Gottschalk 1,2 , Elisabeth Michel 3, Lena M. Thöle1,4, Anja S. Studer 5,6, Adam P. Hasenfratz1,7, Nicole Schmid1, Martin Butzin 8, Alain Mazaud3, Alfredo Martínez-García 5, Sönke Szidat9 & Samuel L. Jaccard 1,10 1234567890():,; Past changes in ocean 14C disequilibria have been suggested to reflect the Southern Ocean control on global exogenic carbon cycling. Yet, the volumetric extent of the glacial carbon pool and the deglacial mechanisms contributing to release remineralized carbon, particularly from regions with enhanced mixing today, remain insufficiently constrained. Here, we reconstruct the deglacial ventilation history of the South Indian upwelling hotspot near Kerguelen Island, using high-resolution 14C-dating of smaller-than-conventional foraminiferal samples and multi-proxy deep-ocean oxygen estimates. We find marked regional differences in Southern Ocean overturning with distinct South Indian fingerprints on (early de-)glacial atmospheric CO2 change. The dissipation of this heterogeneity commenced 14.6 kyr ago, signaling the onset of modern-like, strong South Indian Ocean upwelling, likely promoted by rejuvenated Atlantic overturning. Our findings highlight the South Indian Ocean’s capacity to influence atmospheric CO2 levels and amplify the impacts of inter-hemispheric climate variability on global carbon cycling within centuries and millennia. 1 Institute of Geological Sciences and Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland. 2 Lamont-Doherty Earth Observatory, Columbia University of the City of New York, Palisades, NY, USA. 3 Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CNRS-CEA-UVSQ, Université de Paris-Saclay, Gif-sur-Yvette, France.
    [Show full text]
  • Download (7Mb)
    ARTICLE https://doi.org/10.1038/s41467-021-22586-2 OPEN 13 million years of seafloor spreading throughout the Red Sea Basin ✉ Nico Augustin 1 , Froukje M. van der Zwan 2, Colin W. Devey 1 & Bryndís Brandsdóttir3 The crustal and tectonic structure of the Red Sea and especially the maximum northward extent of the (ultra)slow Red Sea spreading centre has been debated—mainly due to a lack of detailed data. Here, we use a compilation of earthquake and vertical gravity gradient data 1234567890():,; together with high-resolution bathymetry to show that ocean spreading is occurring throughout the entire basin and is similar in style to that at other (ultra)slow spreading mid- ocean ridges globally, with only one first-order offset along the axis. Off-axis traces of axial volcanic highs, typical features of (ultra)slow-spreading ridges, are clearly visible in gravity data although buried under thick salt and sediments. This allows us to define a minimum off- axis extent of oceanic crust of <55 km off the coast along the complete basin. Hence, the Red Sea is a mature ocean basin in which spreading began along its entire length 13 Ma ago. 1 GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany. 2 King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia. ✉ 3 Institute of Earth Sciences, Science Institute, University of Iceland, Reykjavík, Iceland. email: [email protected] NATURE COMMUNICATIONS | (2021) 12:2427 | https://doi.org/10.1038/s41467-021-22586-2 | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-22586-2 he Red Sea (Fig.
    [Show full text]
  • Contribution of Multibeam Bathymetry to Understanding the Processes That Shape Mid-Ocean Ridges
    Charting the Secret World of the Ocean Floor. The GEBCO Project 1903-2003 1 CONTRIBUTION OF MULTIBEAM BATHYMETRY TO UNDERSTANDING THE PROCESSES THAT SHAPE MID-OCEAN RIDGES BY Marie-Helene Cormier Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA Abstract With the emergence in the 1980’s of multibeam bathymetric systems, comprehensive two-dimensional maps of the seafloor became available that changed our view of the mid- ocean ridges. Multibeam bathymetry reveals a fine-scale segmentation of the ridge axis, with ridge offsets as small as a few hundred meters. Ridge segments are 10-100km long and generally correspond with individual volcanic systems. While the morphology of the ridge axis depends primarily on spreading rates, it also varies predictably from the center to the ends of a ridge segment and with local supply of magma. Discordant features on the ridge flanks provide a continuous record of the tectonic evolution of the mid-ocean ridges and reveal that the plate boundary is commonly reorganizing in response to minor changes in plate motion and variations in the thermal structure of the lithosphere. Emerging deep- submergence technologies now provide microbathymetric maps with a vertical resolution of a few cm, sufficient to accurately map individual lava flows, eruptive vents, fissures, and faults. A strategy of repeating microbathymetric surveys may offer the potential to precisely characterize seafloor spreading events. Introduction Much of the volcanic and seismic activity on earth occurs along the 75,000 km of mid- ocean ridges that circle the continents, hidden from view beneath 2000 to 4000 m of water (Fig.
    [Show full text]