Paleomagnetism of igneous rocks from the Shatsky Rise: Implications for paleolatitude and oceanic plateau volcanism

Abstract

The Cretaceous Period stands out in Earth's geologic history by ubiquitous and sustained massive eruption of lava, forming several enormous igneous plateaus in the ocean basins worldwide. It has been proposed that the subaerial phases of Cretaceous oceanic plateau formation spurred the global environmental deterioration, yet this view is supported by patchy fossil and/or rock evidence for uplifting of the plateau summits above the sea level. Reported here is by far the most comprehensive case of Cretaceous plateau emergence at northern Shatsky Rise, Northwest Pacific, based on the integration of unique micropalaeontological and seismic evidence. From just above the flat-topped igneous edifice, recent Integrated Ocean Drilling Program (at Site U1346) recovered early Cretaceous (Hauterivian) ostracod and foraminiferal assemblages showing marked shallow-marine preferences. Most intriguing discovery is an ostracod taxon with well-developed eye tubercles, which serves as compelling palaeobiological evidence for a very shallow, euphotic setting. By linking the nearshore biofacies (<20 m water depth) to the basement topography undoubtedly shaped by subaerial weathering and/or erosion, it is obvious that northern Shatsky Rise was remarkably emergent during its final emplacement phase. We suggest that early Cretaceous surface environments might have been affected, at least in part, by Shatsky Rise subaerial volcanism.

Geochemistry and age of Shatsky, Hess, and Ojin Rise seamounts: Implications for a connection between the Shatsky and Hess Rises

“…Shatsky Rise is a massive oceanic plateau, covering an area of 4.8x10 5 km 2 similar to the size of California (Sager et al, 1999;Sager, 2005) and consists of three discrete volcanic edifices ( Fig. 1a): the TAMU Massif, the ORI Massif, and the Shirshov Massif (Sager et al, 1999), that become younger (Geldmacher et al, 2014;Heaton & Koppers, 2014) and smaller in volume toward the northeast (Sager et al, 1999), consistent with the southwestward trajectory of the Pacific plate's motion from 145-125 Ma (Larson et al, 1992;Kroenke, 1996;Sager, 2007;Sager et al, 2015). The northeast flank of the Shirshov Massif is truncated by a WNWtrending graben.…”

Pacific‐Panthalassic Reconstructions: Overview, Errata and the Way Forward

“…Paleolatitudes from the Pacific plate can be derived from sediment and basalt cores, but we only examine paleomagnetic data collected from volcanic rocks (Shatsky Rise, Ontong Java Plateau, and Hess Rise) and not from sediments, because the latter may be prone to inclination shallowing effects (e.g., Bilardello & Kodama, 2010a, 2010bDomeier et al, 2012;Kent & Tauxe, 2005;Kodama, 2009;Tauxe, 2005;Torsvik et al, 2012). The Shatsky Rise erupted at around 144 Ma (Mahoney et al, 2005;Tejada et al, 2016), and there are younger volcanics (141-134 Ma; Figure 9a) with paleomagnetic data that collectively yield local paleolatitudes between 3°N and 10°N (±20°; Figure 11) in the paleomagnetic reference frame (Sager et al, 2015;Tominaga et al, 2005). Owing to these low paleolatitudes and ambiguities in the polarity of the paleomagnetic data, Tominaga et al (2012) argued that the Shatsky Rise initially erupted at low southerly latitudes at 144 Ma and then drifted across the equator, but we model all the volcanic rocks of the Shatsky Rise to have erupted in northerly latitudes (see also Sager et al, 2015).…”

“…Modeled paleomagnetic latitudes fit well with the observations (Figure 11), and both NR (mean = 0.18 ± 0.04°/Ma between 150 and 90 Ma) and Pacific plate velocities (mean = 0.46 ± 0.09°/Ma, corresponding tõ 5 cm/year) are low and reasonable (Figure 13). Sager et al, 2015Tominga et al, 2005), Ontong Java Plateau (LEG 192: Site 807, Hole 1183, Hole 1185, Hole 1186, Hole 1186Riisager et al, 2003) and Hess Rise (Hole 465, Leg 62; Sayre, 1981;recalculated in Cox & Gordon, 1984).…”

“…The Shatsky Rise erupted at around 144 Ma (Mahoney et al, ; Tejada et al, ), and there are younger volcanics (141–134 Ma; Figure a) with paleomagnetic data that collectively yield local paleolatitudes between 3°N and 10°N (±20°; Figure ) in the paleomagnetic reference frame (Sager et al, ; Tominaga et al, ). Owing to these low paleolatitudes and ambiguities in the polarity of the paleomagnetic data, Tominaga et al () argued that the Shatsky Rise initially erupted at low southerly latitudes at 144 Ma and then drifted across the equator, but we model all the volcanic rocks of the Shatsky Rise to have erupted in northerly latitudes (see also Sager et al, ). Paleomagnetic sites from the Ontong Java Plateau are dated to ~123 Ma and the local paleolatitudes of 18 +4.5 / ‐4.1 o S to 28 +14.1 / ‐10.3 o S (Riisager et al, ) are used to constrain the latitude of the Pacific plate at that time.…”

“…Models E and R are similar for Shatsky and Hess Rises but Model E latitudes for Ontong Java Plateau are statistically different from the observed latitudes. Inset maps : Paleomagnetic sampling locations of volcanic rocks from Shatsky Rise (EXP 324: Site U1350, U1346, U1349, U1347; Sager et al, & Hole 1213B; Tominga et al , 2005), Ontong Java Plateau (LEG 192: Site 807, Hole 1183, Hole 1185, Hole 1186, Hole 1186; Riisager et al, ) and Hess Rise (Hole 465, Leg 62; Sayre, ; recalculated in Cox & Gordon, ).…”