Tectonic Reconstruction of the Ellice Basin

Abstract

A geophysical survey of the Ellice Basin, located in the south equatorial Pacific between the Ontong Java and Manihiki plateaus, revealed evidence for an extinct seafloor spreading system between the Pacific Plate and the Manihiki Plate. The spreading occurred during the Cretaceous Normal Superchron, the longest normal period of magnetic polarity from 121 to 83 Ma, and therefore lacks magnetic‐isochron‐derived age and plate motion constraints. Utilizing high‐resolution bathymetric data acquired on survey KM1609 during December 2016–January 2017, morphological and directional analyses were performed on the seafloor spreading fabric. Plate motion between the Pacific Plate and the Manihiki Plate during the Cretaceous Normal Superchron is described by three main stages of spreading. Stage 1 spreading was generally E‐W until a clockwise rotation of the spreading direction rotated transform faults by ~15° and lengthened spreading ridges to form Stage 2 zed pattern rhomboids. An offset between Stage 2 fracture zones evidences the presence of a complex and short‐lived Stage 3. Reconstructions, with respect to the Pacific Plate, are created for each of the three stages. Our reconstructions show that there was an earlier opening history prior to Stage 1 that ultimately reconstructs the Ontong Java and Manihiki plateaus; its quantification will await high‐resolution multibeam bathymetry data closer to the two plateaus.

Breaking Up Is Hard to Do: Magmatism During Oceanic Arc Breakup, Subduction Reversal, and Cessation

“…The Alexa‐type seamounts between the white arrows on the Pacific Plate include Alexa, Niulakita, Nukelaelae, Bustard, Bayonaise, and Tuscarora, from west to east. The Ellice Basin (EB) covers the entire northern part of the figure, both east and west of the Rurutu track (Benyshek et al., 2019). The South Fiji Basin shoshonites extend south of the figure and east of the Three Kings Rise (TKR; Mortimer et al., 2021).…”

Reconciling the Cretaceous breakup and demise of the Phoenix Plate with East Gondwana orogenesis in New Zealand

“…The Phoenix lineations on the Pacific Plate are overlain in the west by the Ontong Java Plateau (Larson, 1997). South of the Phoenix lineations is the oceanic Ellice Basin, which is devoid of marine magnetic anomalies due to its formation during the Cretaceous Normal Superchron, but has east-west trending fracture zones (Benyshek et al, 2019). According to the 'superplateau' hypothesis, the Ontong Java Plateau, together with the Manihiki and Hikurangi plateaus was emplaced as a single Large Igneous Province, known as Ontong Java Nui, around 125-120 Ma (Fig.…”

“…A tectonic reconstruction for the final stages of opening of the Ellice Basin was presented by Benyshek et al (2019), based on detailed bathymetric data from the center of the basin. They tentatively suggested ages for their rotation poles, based on estimated spreading rates, but these await confirmation by radiometric dating of basement samples (Benyshek et al, 2019). The end of spreading in the Ellice Basin most likely occurred before the end of the CNS, i.e., before 83.7 Ma.…”

Reconciling the Cretaceous breakup and demise of the Phoenix Plate with East Gondwana orogenesis in New Zealand

“…We note that the age for the end of Osbourn Trough spreading may change in the future if more reliable radiometric dating of the Osbourn Basin becomes available, and we will discuss below what difference a different age would make for the estimate for subduction arrest at the New Zealand margin. For the Ellice Basin, we use the Chandler et al (2012) rotation pole for the Ontong Java-Manihiki fit at 120 Ma and the rotation poles of Benyshek et al (2019) for subsequent opening, with spreading ending at 90 Ma.…”

“…The rotation poles for the reconstruction of the Ellice Basin include a rotation of the Manihiki Plate relative to the Pacific Plate between 102 and 98 Ma, based on a change in fracture zone orientation in the Ellice Basin from ~E-W to WNW-ESE (Taylor, 2006;Benyshek et al, 2019). As the Chasca Plate is reconstructed relative to the Manihiki Plate in our plate circuit, the rotation modeled by Benyshek et al (2019) also results in a rotation of the Chasca Plate. This in turn leads to convergence at the Chasca-Farallon plate boundary that at that time was still located at the latitude of northern South America.…”