TY  - JOUR
A1  - Weber, Michael H.
A1  - Wicks, Charles
A1  - Le Stunff, Yves
A1  - Romanowicz, Barbara
A1  - Krüger, Frank
T1  - Seismic evidence for a steeply dipping reflector-stagnant slab in the mantle transition zone
JF  - Geophysical journal international
N2  - Studies of seismic tomography have been highly successful at imaging the deep structure of subduction zones. In a study complementary to these tomographic studies, we use array seismology and reflected waves to image a stagnant slab in the mantle transition zone. Using P and S (SH) waves we find a steeply dipping reflector centred at ca. 400 km depth and ca. 550 km west of the present Mariana subduction zone (at 20N, 140E). The discovery of this anomaly in tomography and independently in array seismology (this paper) helps in understanding the evolution of the Mariana margin. The reflector/stagnant slab may be the remains of the hypothetical North New Guinea Plate, which was theorized to have subducted ca. 50 Ma.
KW  - Mantle processes
KW  - Composition of the mantle
KW  - Seismic tomography
KW  - Wave scattering and diffraction
KW  - Subduction zone processes
KW  - Volcanic arc processes
KW  - Continental margins: convergent
KW  - Pacific Ocean
Y1  - 2015
U6  - https://doi.org/10.1093/gji/ggu438
SN  - 0956-540X
SN  - 1365-246X
VL  - 200
IS  - 2
SP  - 1235
EP  - 1251
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Panitz, Sina
A1  - Cortese, Giuseppe
A1  - Neil, Helen L.
A1  - Diekmann, Bernhard
T1  - A radiolarian-based palaeoclimate history of Core Y9 (Northeast of Campbell Plateau, New Zealand) for the last 160 kyr
JF  - Marine micropaleontology
N2  - Sea-surface temperatures (SSTs) based on radiolarian assemblage changes are estimated for the last 160 kyr, from a sediment core (Y9) recovered from Pukaki Saddle, northeast of Campbell Plateau. Site Y9 lies beneath Subantarctic Surface Water (SAW) immediately to the north of the Subantarctic Front (SAF), which in this region is bathymetrically constrained by the edges of Campbell Plateau and defines the northern boundary of the Antarctic Circumpolar Current (ACC). Radiolarian assemblages are characterised by an exceptionally high abundance of the Antarctic to subantarctic species Antarctissa spp. (up to 68%), especially during glacial intervals. SST estimates are derived using Factor Analysis and the Modern Analog Technique. Both methods capture the glacial-interglacial (G-I) pattern. The SST reconstructions show the changing relative influence of distinct water masses during the past G-I cycle, with major temperature variations of the order of 7-9 degrees C at glacial Terminations. Glacials (marine isotope stages (MIS) 6 and 2) are associated with particularly cool SSTs that are indicative of a more vigorous SAF/ACC and an enhancement of the inflow through Pukaki Saddle and/or frequent development of cold-core eddies at the SAF. By contrast, the influence of warmer waters and relaxation of the ACC during interglacials can be inferred from temperatures slightly warmer (e.g., mid-Holocene) and/or comparable to present day (e.g., MIS 5e). During these intervals, relatively warmer temperatures most likely indicate a higher warmcore eddy activity due to a strengthened Subtropical Front and/or a weakened inflow of cool water through Pukaki Saddle and/or an increased stratification in the Campbell Plateau region. Furthermore, the SST record is characterised by an abrupt warming at ca. 10 kyr (i.e., Termination l), the occurrence of a reversal at Termination I, and a warming event at the end of MIS 4, coinciding with the A4 event in the Byrd ice core. These characteristics, together with the pronounced G-I cycle shown by the SST estimates, suggest that Site Y9 is influenced by major oceanographic changes in the SW Pacific and responds to thermal changes at high southern latitudes. (C) 2014 Elsevier B.V. All rights reserved.
KW  - Radiolaria
KW  - Palaeotemperature
KW  - Subantarctic Front
KW  - Antarctic Circumpolar Current
KW  - Pacific Ocean
Y1  - 2015
U6  - https://doi.org/10.1016/j.marmicro.2014.12.003
SN  - 0377-8398
SN  - 1872-6186
VL  - 116
SP  - 1
EP  - 14
PB  - Elsevier
CY  - Amsterdam
ER  -