Influence of late Pleistocene sea-level variations on midocean ridge spacing in faulting simulations and a global analysis of bathymetry

Abstract

It is established that changes in sea level influence melt production at midocean ridges, but whether changes in melt production influence the pattern of bathymetry flanking midocean ridges has been debated on both theoretical and empirical grounds. To explore the dynamics that may give rise to a sea-level influence on bathymetry, we simulate abyssal hills using a faulting model with periodic variations in melt supply. For 100-ky melt-supply cycles, model results show that faults initiate during periods of amagmatic spreading at half-rates >2.3 cm/y and for 41-ky melt-supply cycles at half-rates >3.8 cm/y. Analysis of bathymetry across 17 midocean ridge regions shows characteristic wavelengths that closely align with the predictions from the faulting model. At intermediate-spreading ridges (half-rates >2.3 cm/y and ≤ 3.8 cm/y) abyssal hill spacing increases with spreading rate at 0.99 km/(cm/y) or 99 ky ( n = 12; 95% CI, 87 to 110 ky), and at fast-spreading ridges (half-rates >3.8 cm/y) spacing increases at 38 ky ( n = 5; 95% CI, 29 to 47 ky). Including previously published analyses of abyssal-hill spacing gives a more precise alignment with the primary periods of Pleistocene sea-level variability. Furthermore, analysis of bathymetry from fast-spreading ridges shows a highly statistically significant spectral peak ( P < 0.01) at the 1/(41-ky) period of Earth’s variations in axial tilt. Faulting models and observations both support a linkage between glacially induced sea-level change and the fabric of the sea floor over the late Pleistocene.

Honing in on the climate signal in seafloor topography

“…The models by Huybers et al. ( 6 ) confirm findings of previous studies that this negative correlation reflects “lithospheric controls” (large white arrow) on fault wavelength when the periods of magmatic and amagmatic cycles are relatively short ( 19 ). However, when observations at intermediate spreading rates and fast spreading rates are viewed as two separate groups, the wavelengths within each group correlate positively with spreading rate ( 19 , 21 ).…”

“…In PNAS, Huybers et al. ( 6 ) argue that one such process originates with the fall and rise of sea level during glacial–interglacial climate cycles.…”

“… Modified from Huybers et al. ( 6 ), showing observed (colored circles) and modeled (open squares) characteristic wavelengths of abyssal hill topography versus the rate of seafloor spreading. When considering all of the observations together, wavelength correlates negatively with spreading rate ( 17 , 18 , 20 ).…”

“…Huybers et al. ( 6 ) provide an important advancement by examining >200 shipboard profiles in 17 different areas representing an appreciable range of seafloor spreading environments around the globe. Their results fortify prior findings ( 18 ) for the dominant global tendency of the characteristic wavelengths of abyssal hills to decrease with increasing seafloor spreading rate, a relation that opposes the positive correlation expected for climate control and, instead, reflects the first-order controls of lithosphere structure and magma flux as they differ with spreading rate ( 19 ) ( Fig.…”

Deep submerged speleothems in the Sansha Yongle Blue Hole (South China Sea) as determination of low sea levels during the Last Glacial Maximum

“…Though previous studies over four decades have thoroughly illustrated variable maximum sea levels using U-Th and U-Pb dating of speleothems in coastal caves (Harmon et al, 1978;Gascoyne et al, 1979;Bard et al, 2002;Dorale et al, 2010;Moseley et al, 2015;Dumitru et al, 2019), the deepest speleothems collected so far were from -54.9 m of a blue hole in South Andros Island (Richards et al, 1994). These speleothems are therefore unable to determine Pleistocene low sea levels, which were often over 100 m lower than they are at present (Richards et al, 1994;Lambeck and Chappell, 2001;Spratt and Lisiecki, 2016;Huybers et al, 2022). Therefore, deep submerged speleothems (-116 m) collected from the Sansha Yongle Blue Hole (SYBH) with reliable ages are useful for determining Last Glacial Maximum (LGM) low sea levels.…”