Dynamic carbonate sedimentation on the Northern Line Islands Ridge, Palmyra Basin

Abstract

The Line Islands Ridge (LIR), located south of the Hawaiian Islands between 7 degrees N and 1 degrees S, is one of the few large central Pacific regions shallower than the regional carbonate compensation depth. Thick sequences of carbonate sediments have accumulated around the LIR despite it being located in the sediment-starved central tropical Pacific. The LIR is an important source of carbonates to the surrounding region and deposition around the LIR has expanded the equatorial Pacific carbonate sediment tongue by about 5% of its total area. Furthermore, sediments on the ridge are potentially important paleoceanographic archives. A recent survey at the crest of the LIR finds evidence for high current activity, significant erosion, but overall net sediment deposition. Currents are strong enough to form sediment waves and lee drifts in the Palmyra Basin, at the northern terminus of the LIR. Sediments along the LIR are pelagic foraminiferal sands that are easily eroded and flow out into the surrounding abyssal plain in active submarine channel systems. As channels migrate, pelagic sediments fill in the abandoned channel arms. Despite significant sediment losses from the top of the ridge, 1.3 km of sediment has accumulated in the upper Palmyra Basin over basement formed 68 to 85 million years ago (Ma). Late Neogene erosion may be more extensive than earlier erosion cycles, in response to reduced sediment production as the Palmyra Basin exited the high productivity equatorial latitudes. Sediments with good stratigraphic order needed for paleoceanographic study are limited in this dynamic sedimentary environment, but can be found with proper survey. (C) 2016 Elsevier B.V. All rights reserved

230Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

“…The JdFR, in the northeast Pacific (~45°N, −135°E, 2,655–2,794 m), contains six sites within 50 km of one another and suffers from a range of sediment focusing caused by the rough bathymetry of the mid‐ocean ridge (Costa et al, ; Costa & McManus, ). The Line Islands, in the central equatorial Pacific (~0–7°N, −160°E, 2,798–3,542 m), contain nine sites along a rough carbonate ridge (Lyle et al, ), and although the core transect spans over 1,000 km, their extremely low dust content leads to only minor spatial trends in dust flux on glacial‐interglacial time scales (Costa et al, ; Jacobel et al, ). Focusing factors were calculated within Marine Isotope Stages (MIS; e.g., Lisiecki & Raymo, ).…”

The Geomorphology of Submarine Channel Systems of the Northern Line Islands Ridge, Central Equatorial Pacific Ocean

“…The southwest rim of the platform is one limb of volcanic edifices that form the outer boundary of the NLIR and encompass a 190km-long NW-SE basin that varies in width from 63 to 81 km. The basin contains about 1.3 km of sediments with highly reflective seismic horizons (Lyle et al, 2016).…”

“…Orwig (1981) traced south-and southeast-directed pathways of calcareous turbidites and siliceous oozes from an area several hundred kilometers west of the NLIR and to the south of the area focused on here. More recently, Lynch-Stieglitz et al (2015) and Lyle et al (2016) described cores from the seafloor adjacent to a few guyots and ridges on the NLIR platform and demonstrated that the guyots are capped by thick pelagic carbonates. Lyle et al (2016) provide a discussion of the lithostratigraphy and sediment thickness of the area, as well as a summary of the few seismic-reflection profiles from the NLIR and adjacent deepocean basins.…”

“…The University of New Hampshire's Center for Coastal and Ocean Mapping/Joint Hydrographic Center (UNH-CCOM/JHC) conducted three month-long MBES mapping cruises on the northern Line Islands Ridge (NLIR) (Figure 1), one cruise each in 2010, 2015 and 2016 that in total covered ∼844,000 km 2 . A comment by Lyle et al (2016) in a study of sedimentation of an interior basin on the NLIR stated that, in their opinion, what is needed in the Line Island Ridge area is multibeam bathymetry mapping to help understand the sediment-dynamics processes. That statement by Lyle et al (2016) was the inspiration for us to compile all publicly available multibeam data with data from the three UHN-CCOM/JHC cruises to provide a detailed dataset of the geomorphology of the NLIR.…”

“…A comment by Lyle et al (2016) in a study of sedimentation of an interior basin on the NLIR stated that, in their opinion, what is needed in the Line Island Ridge area is multibeam bathymetry mapping to help understand the sediment-dynamics processes. That statement by Lyle et al (2016) was the inspiration for us to compile all publicly available multibeam data with data from the three UHN-CCOM/JHC cruises to provide a detailed dataset of the geomorphology of the NLIR. The objective of this study is to analyze the available MBES bathymetry and acoustic backscatter data to provide for the first time a comprehensive view of the geomorphology of this area and to provide a detailed quantitative description of the extensive submarine channel systems found in this terrain.…”