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Home , Broken Ridge, Iceland Plateau, Ontong Java Plateau

Journal of the Geological Society, London, Vol. 152, 1995, pp. 1047-1052, 4 figs. Printed in Northern Ireland

Ontong Java and Kerguelen Plateaux: Icelands?

M. F. COFFIN & L.M. GAHAGAN Institute for Geophysics, The University of Texas at Austin, 8701 North Mopac Expressway, Austin, Texas 78759-8397, USA

Abstract: Together with , the two giant oceanic plateaux, Ontong Java in the western Pacific and Kerguelen/ in the , are accumulations of mafic igneous rock which were not formed by 'normal' seafloor spreading. We compare published geochronological, crustal structure, and subsidence results with tectonic fabric highlighted in new satellite-derived free-air gravity data from the three igneous provinces, and conclude that existing evidence weighs lightly against the Ontong Java and Kerguelen plateaux originating at a seafloor spreading centre.

Keywords: Iceland, , , plumes, hot spots.

The two giant oceanic plateaux, Ontong Java in the western Age constraints Pacific, and Kerguelen in the south-central Indian Ocean (Fig. 1), and Iceland are among the best-studied examples of The vast bulk of crust in the ocean basins is dated using large-scale mafic magmatism not resulting solely from magnetic anomalies created by the interplay between the 'normal' seafloor spreading. Analogues on the continents, seafloor spreading process and the alternating polarity of the continental flood , are demonstrably not created by Earth's magnetic field. Mesozoic and Cenozoic marine seafloor spreading, although controversy persists as to magnetic anomalies, summarized globally by Cande et al. whether or not lithospheric extension must precede their (1989), are most commonly tied to geological time through emplacement. The question exists, were the largest oceanic radiometric dating of samples obtained from crust plateaux created at a seafloor spreading centre (e.g. near displaying a particular anomaly (e.g. Cande & Kent 1992, active transform faults), as is the case with Iceland, or were 1995; Gradstein et al. 1994). In some cases, notably Iceland, they created away from active plate boundaries, as is an active seafloor spreading centre can be traced on land Hawaii? We address this question using available age, using a combination of marine and aeromagnetic data (e.g. crustal structure, subsidence and tectonic fabric data, Nunns et al. 1983). Because one-third of the Iceland igneous following a brief description of the plateaux' physical province (Fig. 2) lies above sea level, radiometric dating has characteristics. been possible on many samples. It has confirmed that Iceland has been created by anomalously voluminous, subaerial seafloor spreading, characterized by an age The plateaux progression from 0 Ma along the locus of crustal generation to as much as 15 Ma (McDougall et al. 1984) away from that The Ontong Java Plateau, in the western equatorial Pacific zone (and still above sea level). Multiple and shifting (Fig. 1), encompasses an area of 1 860000km 2 (Coffin & spreading axes, laterally extensive lava flows, numerous Eldholm 1994). Although neighbouring flood basalts in the central volcanoes, erosion, and alteration, however, East Mariana, Nauru, and Pigafetta basins, as well as those contribute to a rather complex tectonic history. of the , may represent part of the same The advent of the 4°Ar/3~Ar dating technique has igneous event that created the Ontong Java Plateau, we brought needed resolution to dating oceanic basalts, and has consider only the Ontong Java Plateau sensu stricto in this had a particularly large impact on oceanic plateaux in comparison with the Kerguelen and Iceland plateaux. The particular. Igneous basement samples from the Ontong Java Kerguelen Plateau and Broken Ridge, which were separated and Kerguelen plateaux, however, are sparse (Figs 3 & 4). by seafloor spreading in Eocene time (Houtz et ai. 1977), Datable igneous rock has only been recovered offshore from together cover an area of 2300000km 2 in the southern three scientific drill sites on the Ontong Java Plateau (289, Indian Ocean (Coffin & Eldholm 1994). Igneous basement 803, 807). Onshore sampling of igneous basement is possible of Broken Ridge has not been penetrated by drilling, and on the southern part of the plateau that has been uplifted to the relationship of rocks dredged from the rifted southern form and Santa Isabel islands. Mahoney et al. (1993) flank of Broken Ridge to the Ridge's underlying igneous have reported that 4°Ar/39Ar dates of igneous basement at basement is unknown (Duncan 1991). Therefore, in this DSDP Site 289, ODP Site 807, and on Malaita Island are all comparison we consider only the Kerguelen Plateau, which 120-122Ma. Some Santa Isabel basalts have also given covers an area of 1 780000km 2. Iceland, in the North dates of 120-122 Ma. Igneous basement at ODP Site 803 Atlantic approximately equidistant from Greenland and N and other basalts on Santa Isabel Island, however, have Europe (Fig. 1), lies astride the Mid-Atlantic Ridge. That yielded dates of 88-90Ma (Bercovici & Mahoney 1994). part of the above sea level covers The geographic distribution of these two dates of basaltic c. 100 000 km2; if submerged portions are included, on the volcanism is not easily reconciled with simple models of age basis of bathymetry, the area totals c. 300 000 km 2. transgressive volcanism along a spreading axis, and has led

1047

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~,Nauru Basin 0o t "~ .) Manihiki ~~ ~ ' Broken ~OntonqPlateauJa/a "~ '~'L~~ i • " Ridge ~'~.~."• 4~Platea0/u / PLATES/UTIG Kerquelen~ " / 30 ° S oO Pla_-teau / ~ 18

Fig. 1. Ontong Java (Ontong Java, Manihiki, Nauru, Pigafetta, and East Mariana), Kerguelen (Kerguelen Plateau, Broken Ridge), and Iceland mafic igneous provinces. Outlines of Ontong Java and Kerguelen in this and Figs 3 and 4 are after Coffin & Eldholm (1994); Iceland in this and Fig. 2 after the General Bathyrnetric Chart of the Oceans (IHO/IOC/CHS 1984).

Bercovici & Mahoney (1994) to propose two volcanic last decade. For example, the gravity field over Iceland episodes caused at 120-122 Ma by an initial plume head and (Fig. 2; Sandwell et al. 1994) clearly shows how NE-SW- at 88-90Ma by the subsequent surfacing of a detached trending, ridge-parallel spreading fabric is continuous plume tail. from the North basin NE across the Iceland Igneous basement of the Kerguelen Plateau has been Plateau to the coast of SW Iceland. This, of course, con- drilled and dredged, and in places cores of sediment and a firms what we know from magnetic anomalies and radio- basalt flow provide minimum age estimates for basement metric dating of onshore basalts. The situation to the NE (Fig. 4). A portion of the Plateau has been interpreted to be of Iceland is not as well displayed on the free-air gravity Cenozoic in age (Coffin & Eldholm 1994), and is not field, but is similar in that symmetric, ridge-parallel discussed further here. On the main, older part of the spreading fabric can be traced from the ocean basin SW to Plateau, Davies et al. (1989) obtained a date of 114 Ma using practically the shoreline. the K-Ar method on a dredged basalt. Whitechurch et al. Given that the Ontong Java and Kerguelen plateaux are (1992) 'determined a wide variety of dates employing Cretaceous in age, one would expect that any possible 4°Ar/39Ar techniques on whole rock ODP basement association with relict seafloor spreading axes would be samples, yet concluded that the bulk of the plateau formed much more subdued than is the case with Iceland and the at c. ll0Ma, on the basis of their most reliable date, active Mid-Atlantic spreading axes to the NE and SW. 109.5 Ma, and the Davies et al. date. Pringle et al. (1994) Relict spreading axes and ridge jumps have been identified have redated the ODP basement samples (Fig. 4), in some places in the ocean basins (Mammerickx & determining ages of c. 110 Ma for sites 750, 749, and 738. Sandwell 1986). In the cases of Ontong Java and Kerguelen, ODP Site 747 basalts have yielded a date of 85 Ma, similar however, marine magnetic anomalies identified to date (Figs to Whitechurch et al.'s date for the flow encountered at Site 3 & 4) provide no clues as to whether the plateaux formed 748. These latter dates are similar to that obtained from at a spreading centre or intra-plate. This is in large part due sediment at the bottom of a piston core on the NE flank of to the fact that a large part of the Ontong Java Plateau the Kerguelen Plateau (Frt~hlich & Wicquart 1989). formed near the start of, and that the Kerguelen Plateau formed during, the Cretaceous superchron, a c. 35Ma period over which the Earth's geomagnetic field remained in Tectonic fabric dominently normal polarity. Great improvement in our knowledge of the tectonic fabric The NE flank of the Ontong Java Plateau is of the seafloor has come from the free-air gravity field over characterized by marked NE-SW trending lineations of the oceans derived from satellite altimetry data over the unknown origin: possibilities include seafloor spreading

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fabric (fracture zones and ridge-parallel faults and abyssal hills) and folding of the crust. The lineations intersect 330" 335" 340" 345" 350" interpreted magnetic isochrons Mll-M14 and postulated fracture zones obliquely, suggesting that if the lineations represent fracture zones or seafloor-spreading fabric, existing interpretations require modification. Longer wave- length, NW-SE-trending lineations are observed on the northern plateau; these may represent folds related to collision of the Ontong Java Plateau with the Solomons arc. Unlike the case of Iceland, no remarkable correlations of spreading centres to plateau are possible. The tectonic fabric of the Kerguelen Plateau appears 65 rather complex (Fig. 4). On the Mesozoic part of the 65" plateau, a series of roughly circular gravity highs between the Kerguelen Isles and Heard Island suggest volcanoes, most likely Cenozoic in age since both the Kerguelen Isles (Giret & Lameyre 1982) and Heard Island (Clarke et al. 1982) are of that age. SE of the Kerguelen Isles, these volcanoes appear to lie on Cretaceous basement. Farther south, steep gravity gradients on the fanks of Elan Bank suggest that Elan Bank was emplaced on relatively young, weak crust of assumed Cretaceous age (Coffin et al. 1986). 330' 335" 340" 345' 350" On the southern half of the Mesozoic plateau, several graben and troughs intersect orthogonally, suggesting a -60 40 20 0 20 40 60 rift/transform system (Ki3nnecke & Coffin 1994). No evidence of relict seafloor spreading exists, however; these Free-air Gravi~ Anomaly (reGal) features appear to have been formed after the plateau was Fig. 2. Iceland and its surrounding plateau, delineated by white line emplaced. No seafloor-spreading fabric is prominent in the on the basis of bathymetry, superimposed on the satellite-derived Enderby Basin to the SW of the Kerguelen Plateau, and free-air gravity field (Sandwell et al. 1994). Magnetic anomaly picks hence the emplacement setting of Kerguelen is either unlike (black crosses) and active plate boundaries (black lines) are after or much more complex than that of Iceland. Nunns et al. (1983).

155 ° 160" 165" 170"

. .

. .

Fig. 3. Ontong Java Plateau, delineated by white line on the basis of bathymetry, as it appears on the satellite-derived gravity field (Sandwell et al. 1994). -5" -5" Sampling locations and dates of samples are shown: black circles indicate Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) sites that sampled igneous basement, and the white circle marks a DSDP site that -10" -10" sampled sediment above basement. Igneous basement of the Ontong Java Plateau has also been sampled on Malaita and Santa Isabel islands. Mag- 155" 160" 165" 170" netic anomaly picks (white crosses), magnetic isochrons (white lines connect- ing picks), fracture zones (unlabelled -60 -40-20 0 20 40 60 white lines), and active plate boundaries (black lines) are after Nakanishi et al. Free-air Gravity Anomaly (mGal) (1992).

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velocities of 7.6-7.7kms -1 are common beneath most of 60" 65" 70" 75" 80" 85" -45" + " -45" Iceland, whereas such relatively low velocities are found only in the axial regions of the spreading ridges. The free-air gravity field of Iceland suggests that it is not in isostatic equilibrium, but is rather dynamically supported by upwelling mantle (Sandwell & MacKenzie 1989). East of Iceland, the Iceland-Faeroe Ridge, however, is in isostatic .50° -50" equilibrium, and shows increased crustal thicknesses of 28-35 km (Bott & Gunnarsson 1980; Bott 1983). Away from the collisional zone along its southern margin, the Ontong Java Plateau appears in relative isostatic equilibrium with the surrounding ocean basins (Fig. 3). The -55+ -55+ crustal thickness of the Ontong Java Plateau is somewhat controversial. Refraction data collected more than two decades ago suggests that the crust of the central Ontong Java Plateati is as thick as 42.7 km (Furumoto et al. 1976), with a maximum average thickness of 39km. They noted, however, that the free-air gravity value of +15 mgal differs by c. 200 mgal from that expected from the crustal structure. -60" -60" Sandwell & Renkin (1988) examined satellite geoid data and topography, and determined a maximum Airy compensation (Moho) depth of 25km. Corroborating those results, Gladczenko (1994) has reinterpreted the refraction data of Furumoto et al. (1976) and determined an igneous crustal thickness of c. 26 km and a depth to the base of the crust of 30-32 km, similar to that of the Iceland-Faeroe Ridge.

-65", ...... ,, -65" Hussong et al. (1979) have argued that the crustal structure 60" 65 ° 70" 75" 80" 85" of the Ontong Java Plateau represents thickening of normal oceanic crust, but, as Coffin & Eldholm (1994) have -60 -40 -20 0 20 40 60 summarized, many oceanic plateaux, volcanic passive Free-air Gravity Anomaly (mGal) margins, and continental flood basalts have similar crustal velocity structures and thicknesses. Fig. 4. Kerguelen Plateau, subdivided by white lines into Cenozoic, Away from its NE flank from which Broken Ridge Mesozoic, and assumed Mesozoic (Elan Bank) portions on the basis of age control and bathymetry (Cotfin& Eldholm 1994), as it separated, Elan Bank, the Labuan Basin, and the Cenozoic appears on the satellite-derived gravity field (Sandwell et al. 1994). province around the Kerguelen Isles, much of the Kerguelen Sampling locations and dates of samples are shown: filled black Plateau appears in relative isostatic equilibrium with the circles are ODP sites that sampled igneous basement; filled white ocean basin to the SW (Fig. 4). Seismic refraction circles indicate an ODP site (748) that sampled a flow lying above experiments on the Cretaceous Kerguelen Plateau (Charvis igneous basement and a piston core site (MD35-510) that sampled & Operto 1993; Operto & Charvis 1995) indicate 21-25 km sediment above basement; open circles indicate dredge sites that thick crust. Refraction crustal thickness concurs with results recovered basaltic basement (MD48-05) and predominantly granites of gravity modeling, which suggest 20-23 km thick crust (MD67). Magnetic anomaly picks (black crosses), magnetic (Houtz et al. 1977). Four drill sites on the southern isochrons (black lines connecting picks), and fracture zones Kerguelen Plateau recovered basalts, mostly tholeiites, (unlabelled black lines) are after Royer & Sandwell (1989). interpreted as basement (Fig. 4). Granite dredged from the east of the Plateau (MD67; Montigny et al. 1993), rare earth element ratios in basalts from the southernmost ODP basement site (738) (Alibert 1991), and deep crustal seismic Crustal structure velocities (Operto & Charvis 1995) on the southern plateau suggesting continental contamination raise the possibility Crustal structure of oceanic plateaux is obtained both by that part of the Kerguelen Plateau is underlain by seismic methods and inversion of gravity data. Wide-angle continental lithosphere. reflection and refraction techniques have benefited im- mensely from improvement in sources, receivers, and processing hardware and software over the last two decades. In general, seismic determinations of crustal structure are Subsidence more reliable than results from non-unique gravity modelling because seismic methods require no assumptions Subsidence analyses of oceanic large igneous provinces of crustal and mantle density structure. suggest strongly that lithospheric cooling plays a dominant Refraction and reflection work confirms that, except for role in their vertical tectonic histories (Detrick et al. 1977; greater thickness (20-24 km) and more pronounced lateral Coffin 1992). Drilling has shown that much of the variations, the Icelandic crust is very similar to mid-ocean Greenland-Scotland Ridge was emplaced subaerially, and ridge to the SE (Bjarnason et al. 1993). The subcrustal has subsided subsequently below sea level (Thiede & structure beneath Iceland differs markedly from that of the Eldholm 1983). adjacent spreading ridges to the NE and SW; upper mantle On the Ontong Java Plateau, no shallow water sediment

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overlies basement at either the drill sites or on the uplifted Ridge, the Ontong Java Plateau, and the Kerguelen Plateau Malaita and Santa Isabel islands (Tarduno 1992). ODP Site appear quite similar in terms of crustal thicknesses and 807 (Fig. 3) sediment documents deposition above the velocities, although this resemblance does not argue for or calcite compensation depth (CCD) from c. 125-118 Ma, and against an origin at a spreading center. Discrepancies below the CCD from c. 118-83Ma. At ODP Site 288, between crustal thicknesses derived from seismic refraction sediment was deposited above the CCD during these times experiments and gravity modeling for the Ontong Java (Tarduno 1992). All of the Ontong Java basalts were Plateau, as well as its unusual vertical tectonic history, apparently erupted in a submarine environment (J. require further study. Mahoney, pers. comm. 1994). This, in combination with a (6) Subsidence histories of the three provinces differ crustal thickness of >-25 km, argues strongly that the Ontong markedly. The entirely submarine emplacement of the Java Plateau was not created at a spreading axis. Many Ontong Java Plateau and the c. 50 Ma subaerial phase of oceanic plateaux, including Iceland, experience subaerial portions of the Kerguelen Plateau argue against an construction and erosion (Detrick et al. 1977; Coffin 1992). emplacement setting resembling Iceland. One possible explanation is that neutrally-buoyant, (7) We conclude that existing evidence weighs lightly 3.2gcm -3 cumulates forming the lower c. 40% of the against the Ontong Java and Kerguelen plateaux sharing a Ontong Java Plateau do not allow the plateau to subside similar origin with Iceland at a spreading axis. Relevant (Schaefer & Neal 1994), which would argue against the data, however, are extremely few. More basement samples plateau forming at a spreading centre. from and geophysical characterization of the two giant On the Kerguelen Plateau, terrestrial, terrigenous, oceanic plateaux are clearly required. and/or shallow water sediment overlies basement at two of the drill sites (738, 750), and at the other two sites (747, 749) We thank M. Storey, J. Mahoney, R. Duncan, M. Pringle, T. a significant hiatus separates basement and sediment (Coffin Gladczenko, F. Frey, J. Tarduno, and A. Saunders for preprints and 1992). Weathering characteristics of the basalt at all four for discussions on ages of the Ontong Java and Kerguelen plateaux, sites and subsidence analysis suggests subaerial or shallow P. Charvis and L. Kroenke for preprints and discussions on the water emplacement. Angular unconformities observed on crustal structure of the two plateaux, S. Gudlaugsson for references seismic reflection data support subaerial exposure and on Iceland, and O, Eldholm for valued time and resources at the erosion of basement (Coffin et al. 1990), which may have University of Oslo. We are grateful to R. White, L. Ktinnecke and lasted as long as 50Ma following emplacement. This an anonym for reviews. This work is part of a larger study of large subaerial history, perhaps lengthened by post-emplacement igneous provinces supported by the University of Texas at Austin, tectonism (Coffin 1992), is in marked contrast to both the the Norwegian Research Council for Science and the Humanities, c. 15 Ma subaerial emplacement duration of Iceland and the the Joint Oceanographic Institutions/United States Science entirely submarine history of the Ontong Java Plateau. Advisory Committee, the Industrial Liaisons of the University of Oslo, and sponsors of the Plates Project. The University of Texas at Austin Institute for Geophysics contribution no. 1150. Conclusions (1) Basement ages on the Ontong Java and Kerguelen References plateaux show no simple Icelandic-type pattern of age ALIBERT, C. 1991. Mineralogy and geochemistry of a basalt from Site 738: progression away from a central axis. Instead, on both implications for the tectonic history of the southernmost part of the plateaux two peaks of volcanic activity have been observed Kerguelen Plateau. Proceedings oft he Ocean Drilling Program, Scientific to date, each separated by approximately 30 Ma of relative Results, 119, 293-298. BERCOVIO, D. & MAHONEY, J. 1994. Double flood-basalt events and the quiescence. Basement samples, however, are extremely separation of heads at the 660 km discontinuity. Science, limited, and more complex tectonic histories than that of 266, 1367-1369. Iceland could conceivably account for the giant plateaux BJARNASON, I.T., MENKE, W., FLOVENZ, O.G. & CARESS, D. 1993. originating along a spreading axis. These could include the Tomographic image of the mid-Atlantic plate boundary in southwestern Iceland. Journal of Geophysical Research, 98, 6607-6622. intersection of a plume with a triple junction (e.g. Shatsky Bo-r'r, M.P. 1983. The crust beneath the Iceland-Faeroe Ridge. In: BOTr, Rise: Sager & Han 1993) or with fracture zones (e.g. M.H.P., Sgxov, S., TALWANI, M. & THIEDE, J. (eds) Structure and Marquesas: McNutt et al. 1989), among others. Development of the Greenland-Scotland Ridge: New Methods and (2) Magnetic anomaly patterns in the basins adjacent to Concepts. Plenum, New York, 63-75. the Ontong Java and Kerguelen plateaux, limited or absent -- & GUNNARSSON, K. 1980. Crustal structure of the lceland-Faeroe Ridge. Journal of Geophysics, 47, 221-227. due to the Cretaceous superchron, do not reveal an CANOE, S.C. • KENT, D.V. 1992. A new geomagnetic polarity time scale for Icelandic-type development at ridge axes. the Late Cretaceous and Cenozoic. Journal of Geophysical Research, 97, (3) Away from zones of convergence, extension, and 13917-13951. Cenozoic volcanism, the Ontong Java and Kerguelen -- & KENT, D.V. 1995. Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic. Journal of Geophysical plateaux are in isostatic equilibrium with their adjacent Research, 100, 6093-6095. ocean basins, similar to the Iceland-Faeroe Ridge. --, LABRECQUE,J.L., LARSON, R.L., P1TMAN III, W.C., GOLOVCHENKO,X. & (4) The tectonic fabric of relict spreading axes, readily HAXBY, W.F. 1989. Magnetic lineations of the World's ocean basins apparent in Iceland, is not observed in the satellite-derived (chart). Tulsa, OK (American Association of Petroleum Geologists). CHARVIS, P. 8£ OPERTO, S. 1993. Structure profonde du domaine nord du free-air gravity fields of the Ontong Java and Kerguelen plateau de Kerguelen (oc6an Indien austral): r6sultats pr61iminaires de la plateaux, arguing against their originating at spreading axes. campagne MD66/KeOBS. Comptes Rendus de l'Acadamie des Sciences The Cretaceous Kerguelen Plateau, however, displays Paris, 316, 341-347. intriguing post-emplacement tectonic lineaments which have CLARKE, [., McDOUGALL, I. & WHITFORD, D.J. 1982. Volcanic evolution of Heard and McDonald islands, southern Indian Ocean. In: OLIVER, R.L., not yet been explained by any plate tectonic model for the JAMES, P.R. & JAGO, J.B. (eds) Antarctic Earth Science. Cambridge region. University Press, Cambridge, 632-635. (5) The crustal structures of the inactive Iceland-Faeroe COVFIN, M.F. 1992. Emplacement and subsidence of Indian Ocean plateaus

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/152/6/1047/4893212/jgs_152_006_1047.pdf by guest on 30 September 2021 1052 M. F. COFFIN & L. M. GAHAGAN

and submarine ridges. In: DUNCAN, R.A., REA, D.K., KIDD, R.B, VON Union, Geophysical Monographs, 77, 233-261. RAD, U. & WEISSEL, J.K. (eds) Synthesis of Results from Scientific MAMMERICKX, J. • SANDWELL, D. 1986. Rifting of old oceanic lithosphere. Drilling in the Indian Ocean. American Geophysical Union, Geophysical Journal of Geophysical Research, 91, 1975-1988. Monographs, 70, 115-125. McDOUGALL, I., KRISTJANSSON, L. & SAEMUNDSSON, K. 1984. Magnetostrati- -- t~ ELDHOLM, O. 1994. Large igneous provinces: crustal structure, graphy and geochronology of northwest Iceland. Journal of Geophysical dimensions, and external consequences. Reviews of Geophysics, 32, 1-36. Research, 89, 7029-7060. , DAVIES, H.L. & HAXBY, W.F. 1986. Structure of the Kerguelen Plateau McNuTT, M., FISCHER, K., KRUSE, S. & NATLAND, J. 1989. The origin of the province from Seasat altimetry and seismic reflection data. Nature, 324, Marquesas fracture zone ridge and its implications for the nature of hot 134-136. spots. Earth and Planetary Science Letters, 91, 381-393. , MUNSCHY, M., COLWELL, J.B., SCHLICH, R., DAVIES, H.L, & LI, Z.G. MONTIGNY, R., KARPOFF, A.-M. & HOFMANN, C. 1993. R6sultats d'un dragage 1990. Seismic stratigraphy of the Raggatt Basin, southern Kerguelen par 55°18'S-83°04'E dans le Bassin de Labuan (campagne MD67, oc6an Plateau: tectonic and paleoceanographic implications. Geological Society Indien m6ridional): implications gdodynamiques. Journ~es spOcialisOes de of America Bulletin, 102, 563-579. la Soci~t~ GOologique de France, Paris, 93. DAVIES, H.L., SUN, S.-S., FREY, F.A., GAUTIER, I., McCuLLOCH, M.T., PRICE, NAKANISHI, M., TAMAKI, K. & KOBAYASHI, K. 1992. Magnetic anomaly R.C., BASSIAS, Y., KLOOTWIJK, C.T. & LECLAIRE, L. 1989. Basalt lineations from Late Jurassic to in the west-central basement from the Kerguelen Plateau and the trail of a DUPAL plume. Pacific Ocean. Geophysical Journal International, 109, 701-719. Contributions to Mineralogy and Petrology, 103, 457-469. NUNNS, A.G., TALWANI, M., LORENTZEN, G.R., VOGT, P.R., SUGURGEIRSSON, DETRICK, R.S., SCLATER, J.G. & THIEDE, J. 1977. The subsidence of aseismic T., KRISTJANSSON, L., LARSEN, H.C. & VOPPEL, D. 1983. Magnetic ridges. Earth and Planetary Science Letters, 34, 185-196. anomalies over Iceland and surrounding seas. In: Borr, M.H.P., SAXOV, DUNCAN, R.A. 1991. Age distribution of volcanism along aseismic ridges in S., TALWANI, M. & THIEDE, J. (eds) Structure and Development of the the eastern Indian Ocean. Proceedings of the Ocean Drilling Program, Greenland-Scotland Ridge. New Methods and Concepts. Plenum, New Scientific Results, 121, 507-517. York, 661-678. FRt~HL1CH, F. & WICQUART, E. 1989. Upper Cretaceous and Paleogene OPERTO, S. & CHARVlS, P. 1995. Kerguelen Plateau: a volcanic passive margin sediments from the northern Kerguelen Plateau. Geo-Marine Letters~ 9, fragment? Geology, 23, 137-140. 127-133. PRINGLE, M.S., STOREY, M. & WIJBRANS 1994. 4°Ar/39Ar geochronology of FURUMOTO, A.S., WEBB, J.P., ODEGARD, M.E. & HUSSONG, D.M. 1976. mid-Cretaceous Indian Ocean basalts: constraints on the origin of large Seismic studies on the Ontong Java Plateau, 1970. Tectonophysics, 34, provinces. EOS, 75 (44) (Supplement), 728. 71-90, ROYER, J.-Y. & SANDWELL,D.T. 1989. Evolution of the eastern Indian Ocean GIRET, A. & LAMEYRE, J. 1982. A study of Kerguelen plutonism: petrology, since the Late Cretaceous: constraints from satellite altimetry. Journal of geochronology, and geological implications. In: OLIVER, R.L., JAMES, Geophysical Research, 94, 13 755-13 782. P.R. & JAGO, J.B. (eds) Antarctic Earth Science, Cambridge University SAGER, W.W. & HAN, H.-C. 1993. Rapid formation of the Press, Cambridge, 646-651. inferred from its magnetic anomaly. Nature, 364, GLADCZENKO, T.P. 1994. Crustal structure and composition of selected 610-613. transient large igneous provinces. Cand. Scient. Thesis, Applied SANDWELL, D.T. & MACKENZIE, K.R. 1989. Geoid height versus topography Geophysics, University of Oslo, 220 pp. for oceanic plateaus and swells. Journal of Geophysical Research, 94, GRADSTE1N, F.M., AGTERBERG, F.P., OGG, J.G., HARDENBOL, J., VAN VEEN, 7403-7418. P., THIERRY, J, & HUANG, Z. 1994. A Mesozoic time scale. Journal of -- & RENKIN, M.L. 1988. Compensation of swells and plateaus in the North Geophysical Research, 99, 24 051-24 074. Pacific: no direct evidence for mantle convection. Journal of Geophysical HOUTZ, R.E., HAYES, D.E. & MARKL, R.G. 1977. Kerguelen Plateau Research, 93, 2775-2783. bathymetry, sediment distribution, and crustal structure. Marine --. YALE, M.M. & SMITH, W.H.F. 1994. ERS-1 geodetic mission reveals Geology, 25, 95-130. detailed tectonic structures. EOS, 75 (44) (Supplement), 155. HUSSONG, D.M., WIPPERMAN, L.K. & KROENKE, L.W. 1979. The crustal SCHAEFER, S. & NEAL, C.R. 1994. An estimate of the uplift associated with structure of the Ontong Java and Manihiki plateaus. Journal of the Ontong Java Plateau and the importance of cumulates. EOS, 75 (44) Geophysical Research, 84, 6003-6010. (Supplement), 711. IHO/IOC/CHS 1984. GEBCO--General bathymetric chart of the oceans TARDUNO, J. 1992. Vertical and horizontal tectonics of the Cretaceous Ontong (Sth edition). International Hydrographic Organization/Inter- Java Plateau. EOS, 73 (43) (Supplement), 532. governmental Oceanographic Commission/Canadian Hydrographic THIEDE, J. & ELDHOLM, O. 1983. Speculations about the paleodepth of the Service, Ottawa, Canada. Greenland-Scotland Ridge during Late Mesozoic and Cenozoic times. KENT, D. V. & GRADSTE1N, F., 1985. A Cretaceous and Jurassic In: Borr, M.H.P., SAxov, S., TALWANI, M. & THIEDE, J. (eds) Structure geochronology. Geological Society of America Bulletin, 96, 1419-1427. and Development of the Greenland-Scotland Ridge. New Methods and KONNECKE, L. & COFFIN, M.F. 1994. Tectonics of the Kerguelen Plateau, Concepts. Plenum, New York, 445-456. southern Indian Ocean. EOS, 75 (44) (Supplement), 154. WHITECHURCH, H., MONTIGNY, R., SEVIGNY, J., STOREY, M. & SALTERS, V. 40 39 MAHONEY, J.J., STOREY, M.A, DUNCAN, R.A., SPENCER, K.J., AND PRINGLE, 1992. K-Ar and Ar- Ar ages of central Kerguelen Plateau basalts. M. 1993. Geochemistry and age of the Ontong Java Plateau. In: PRINGLE, Proceedings of the Ocean Drilling Program, Scientific Results, 120, M.S. & SAGER, W.W. (eds) The Mesozoic Pacific. American Geophysical 71-77.

Received 9 November 1994; revised typescript accepted 3 May 1995.

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