Oceanic axial depth and age-depth distribution of oceanic lithosphere; comparison of magnetic anomaly picks versus age-grid models

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Author(s): Rowley, David B.
Author Affiliation(s): Primary:
University of Chicago, Chicago, IL, United States
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The oceanic lithosphere age-depth relationship is a fundamental consequence of Earth's convective system that is reassessed by integrating four major datasets. (1) Axial depths (Zr) along the modern mid-oceanic ridge (MOR) vary from -6453m to +1998m, with median (-3000m), modal (-2670m), and area-weighted mean (-3044m) depths. Zr has some correlation with spreading rate up to about 50 mm/a if hotspot impacted North Atlantic and Sheba MORs are excluded. (2) The relationship of zero-age crustal thickness (Zc) with Zr is tested based on a compilation of ∼1000 estimates. There is some correlation but it is not a compact relationship implying that other processes contribute to both Zr and Zc variations. (3) A revised sediment-load correction (SLC) is presented based on assessing 9,260,185 records from 1263 IODP sites on oceanic lithosphere with wet bulk density measurements. Dispersion of integrated wet bulk density measurement-derived SLCs for the 1263 sites implies ∼±100 m uncertainty in the SLC at 1300m sediment thickness. (4) The age-depth relationship is derived based on SLCed depths of ∼90,000 explicitly dated, globally distributed magnetic reversal picks from the GSFML database. A best-fit global age-median SLCed depth relationship using a plate model with zero-age ridge depth of -2220m, temperature difference of 1349°C, and asymptotic plate thickness of 120 km. The dispersion of SLCed depths as a function of age is comparable to that observed along the MOR suggesting that zero-age depths contribute to dispersion at all ages. A comparison is made with various vintages of age grid-derived age-depth distributions. The implied age-depth relationship using older versions of the age grid deviate significantly from the age-depth relationship derived using magnetic reversal picks alone. There is considerable disparity between pick ages and corresponding grid cell ages for these data sets. In contrast, the most recent age grid (2016) more closely matches the age-depth relationship derived here and has significantly less disparity with magnetic reversal pick ages. A suggestion is made that the deviation of the age-depth from a half-space cooling to exponential model reflects the advective contribution of asthenospheric flow associated with asthenospheric tractions contributing to plate driving forces.
Year of Publication: 2018
Research Program: IODP2 International Ocean Discovery Program
Key Words: 18 Geophysics, Solid-Earth; Cores; Crust; International Ocean Discovery Program; Lithosphere; Magnetic anomalies; Magnetic field; Marine sediments; Oceanic crust; Oceanic lithosphere; Sediments
Record ID: 2019061767
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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