Absolute Paleolatitude of Northern Zealandia From the Middle Eocene to the Early Miocene

Abstract

The absolute position during the Cenozoic of northern Zealandia, a continent that lies more than 90% submerged in the southwest Pacific Ocean, is inferred from global plate motion models, because local paleomagnetic constraints are virtually absent. We present new paleolatitude constraints using paleomagnetic data from International Ocean Discovery Program Site U1507 on northern Zealandia and Site U1511 drilled in the adjacent Tasman Sea Basin. After correcting for inclination shallowing, five paleolatitude estimates provide a trajectory of northern Zealandia past position from the middle Eocene to the early Miocene, spanning geomagnetic polarity chrons C21n to C5Er (∼48–18 Ma). The paleolatitude estimates support previous works on global absolute plate motion where northern Zealandia migrated 6° northward between the early Oligocene and early Miocene, but with lower absolute paleolatitudes, particularly in the Bartonian and Priabonian (C18n–C13r). True polar wander (solid Earth rotation with respect to the spin axis), which only can be resolved using paleomagnetic data, may explain the discrepancy. This new paleomagnetic information anchors past latitudes of Zealandia to Earth's spin axis, with implications not only for global geodynamics, but also for addressing paleoceanographic and paleoclimate problems, which generally require precise paleolatitude placement of proxy data.

Calcareous nannofossil biostratigraphy and biochronology across the Eocene-Oligocene transition: the record at IODP Site U1509 (Tasman Sea) and a global overview

“…The ACC formed during the EOT when the southern end of South Tasman Rise (Figure 2) separated from Antarctica and allowed water from the southeast Indian Ocean to circulate into the Tasman Sea (Kennett et al, 1975). During the EOT, the paleolatitude of Sites U1509 and U1510 was ~44-45°S and 46-47°S, respectively (Dallanave et al, 2022), but Australia and New Zealand were also farther south. Site U1509 is located near to the South Tasman gateway and hence one might expect it to be one of the first locations in the global ocean to have been affected by ACC inception.…”

Calcareous Nannofossils and Paleoclimatic Evolution Across the Eocene‐Oligocene Transition at IODP Site U1509, Tasman Sea, Southwest Pacific Ocean

“…The late Eocene–early Oligocene paleolatitude for the northern Zealandia Site U1509 is estimated to be ∼44–45°S (Dallanave et al., 2022), which is considerably further south than its present‐day latitude, approximately at 34.65°S. This is a result of extensive tectonic activities that led to the northward movement of Australia and its separation from Antarctica since the late Eocene (e.g., Cande & Stock, 2004).…”

“…These hiatuses traditionally have been interpreted to reflect enhanced seafloor erosion caused by intensification of bottom currents during the progressive opening of gateways for the Southern Ocean and the Antarctic glaciation (Close et al, 2009;Houben et al, 2019;Kennett et al, 1972Kennett et al, , 1975Sauermilch et al, 2019). Extensive seismic studies across the Tasman Sea (Dallanave et al, 2020(Dallanave et al, , 2022Etienne et al, 2018;Sutherland et al, 2017) now suggest that these unconformities relate to major vertical motions of the seafloor caused by tectonism.…”

Trust but verify: How to assess the reliability of paleomagnetic directions by using the R package PmagDirs

“…Typically, it varies from 0.4 to 0.9 depending on the degree of compaction, presence of clay minerals, and the magnetization carrier 23 . A common family of methods for detect and correct for inclination shallowing is based on the magnetic fabric measured in rocks, in the form of either anisotropy of magnetic susceptibility (AMS) or anisotropy of anhysteretic and isothermal remanent magnetization (AARM and AIRM, respectively) 24,[51][52][53][54][55][56] .…”