Magnetostratigraphy of Sites 703 and 704, Meteor Rise, Southeastern South Atlantic

Abstract

ODP Sites 703 and 704 were drilled near the crest of the Meteor Rise in the southeastern part of the South Atlantic in order to explore the role of this aseismic rise as a barrier to the flow of deep water between the Antarctic and South Atlantic during the early evolution of the South Atlantic and to investigate the subsequent subsidence and paleoceanographic evolution of this area.A combination of shipboard whole-core paleomagnetic determinations on all archive core halves and post-cruise paleomagnetic analyses of some 440 discrete samples from the two sites has allowed definition of the sequence of geomagnetic polarity reversals that occurred during deposition of much of this sedimentary sequence. The magnetostratigraphic record for Sift 703 extends from the middle Eocene to the early Miocene and that for Site 704 from the early Miocene to the Pleistocene. The correlation of this record to the standard geomagnetic polarity time scale of Berggren et al. (1985) is generally good for the Oligocene and late Miocene to Pleistocene, but is poorer for the early and middle Miocene.The combined magnetostratigraphic record for these two sites will facilitate the development and chronometric calibration of refined high-latitude biostratigraphic zonations. Furthermore, it provides an important basis for defining the periodicity of the late Neogene stable isotope and carbonate fluctuations observed in these cores and relating these changes to the paleoclimatic and paleoceanographic driving forces.

Evolution of the northern Argentine margin during the Cenozoic controlled by bottom current dynamics and gravitational processes

“…This event, which is also clearly recognized as an unconformity onshore in the northern Austral Basin [ Malumián and Ramos , ] and in the Fuegian Andes [ Malumián and Olivero , ] occurred contemporaneously to the formation of a permanent large East Antarctic ice sheet [ Ehrmann and Mackensen , ; Zachos et al ., ]. The subsequent onset of bottom water formation and stronger bottom current circulation led to the development of prominent unconformities that can be found at several drilling locations in the Southern Hemisphere [ Carter et al ., ; Gersonde et al ., ; Hailwood and Clement , ; Tucholke and Embley , ]. Unconformities of the same age are also documented in seismic studies from the southern Indian Ocean [ Niemi et al ., ; Uenzelmann‐Neben , ] and the South Pacific [ Carter et al ., ; Horn and Uenzelmann‐Neben , ].…”

“…(a, b) Interpreted seismic cross sections of the Ewing terrace (1400-1800 m water depth) at 418S (line BGR 98-39) and 408S (line BGR 98-35) (see Figure 1 for location), and (c, d) uninterpreted sections.Geochemistry, Geophysics, Geosystems 10.1002/2015GC006232 is also clearly recognized as an unconformity onshore in the northern Austral Basin[Malumi an and Ramos, 1984] and in the Fuegian Andes [Malumi an and Olivero, 2006] occurred contemporaneously to the formation of a permanent large East Antarctic ice sheet[Ehrmann and Mackensen, 1992;Zachos et al, 2001]. The subsequent onset of bottom water formation and stronger bottom current circulation led to the development of prominent unconformities that can be found at several drilling locations in the Southern Hemisphere[Carter et al, 1994;Gersonde et al, 1999;Hailwood and Clement, 1991;Tucholke and Embley, 1984].…”

Eocene to Miocene magnetostratigraphy, biostratigraphy, and chemostratigraphy at ODP Site 1090 (sub-Antarctic South Atlantic)

“…In contrast, the detailed nannofossil studies at Holes 744A and 748B (ODP Leg 119/120, Kerguelen Plateau) (Wei and Thierstein, 1991;Wei et al, 1992) are hampered by poorly defined magnetostratigraphic intervals (Keating and Sakai, 1991;Inokuchi and Heider, 1992). Similarly, the nannofossil biostratigraphic results of Wei (1991) from ODP Leg 114 (Sites 699 and 703) are not easily correlated to the GPTS because of poorly defined magnetostratigraphic intervals (Hailwood and Clement, 1991aClement, , 1991b. DSDP Site 516 and other DSDP Leg 72 sites have Cenozoic magnetostratigraphic intervals that are very difficult to interpret, leading to equivocal biomagnetostratigraphic correlations (Berggren et al, 1983;Wei and Wise, 1989).…”

Magnetostratigraphic reinvestigation of the Palaeocene/Eocene boundary interval in Hole 690B, Maud Rise, Antarctica

“…By sampling the cores in this way, it was hoped that ‘push effect’ overprint magnetizations (e.g. Lovlie et al 1986; Hailwood et al 1989; Hailwood & Clement 1991) would be avoided. The boxes were sealed using non‐magnetic tape to minimize H 2 O transfer to/from the sediment.…”