Stratigraphic, Vertical Subsidence, and Paleolatitude Histories of Leg 144 Guyots

Abstract

We summarize the ages and thicknesses of the volcanics and shallow-water carbonate platform sequences recovered by drilling atop guyots on Leg 144, along with results of material previously dredged or drilled in the same areas. To model the subsidence histories of the guyots, we estimate the thermal reset ages of the lithosphere and amounts of initial emergence of the volcanos above sea level as follows: Site 871 (Limalok), 8 Ma thermal reset age of the lithosphere and 171 m of initial emergence of the volcano above sea level; Site 872 (Lo-En), unknown; Sites 873-877 (Wodejebato), 21 Ma and 236 m; Site 878 (MIT), 19 Ma and 0 m; Sites 879-880 (Takuyo-Daisan), 22 Ma and 138 m. We then compare observed subsidence of the guyots, as measured by the ages and thicknesses of their carbonate platform sediments, to the Parsons and Sclater (1977) model subsidence curve for oceanic crust formed by seafloor spreading. Limalok, Wodejebato, and Takuyo-Daisan guyots all subsided more slowly than oceanic lithosphere formed by seafloor spreading of the same thermal age. This suggests that the Cretaceous lithosphere cooled more slowly beneath these guyots than in a ridge crest subsidence model, and/or that some dynamic uplift was contributed from the mantle below. By contrast, MIT Guyot subsided in agreement with the Parsons and Sclater (1977) model, suggesting a more normal underlying thermodynamic structure. The lithosphere beneath Limalok, Wodejebato, and MIT guyots lost significant amounts of thermal age (17-83 Ma) during volcanic construction of these guyots, while the lithosphere beneath Takuyo-Daisan Guyot was essentially unaffected (2 Ma age loss). The small thermal age loss to the lithosphere beneath Takuyo-Daisan Guyot during volcanic construction seems incompatible with its subsequent subsidence history, which is slower than model ridge crest subsidence of the same thermal age range. The first observation implies that the underlying thermodynamic structure was unaffected during volcanic construction, but the second observation implies subsequently anomalous thermodynamic conditions. Perhaps the volcano formed over lithosphere and mantle that was unaltered by that volcanic event and then drifted over an anomalous upwelling during the subsequent period of subsidence. Although possible, this explanation appears somewhat contrived. A paleomagnetic polar wander path for the Pacific Plate is used to reconstruct the paleolatitude histories of these guyots and to define the age and paleolatitude ranges of "crisis zones" for each guyot. These crisis zones are defined by the ages and paleolatitudes of the youngest carbonate platform sediments on each guyot and coincide with the times of death of the ecological communities that built the carbonate platforms. These data all can be encompassed either within a crisis paleolatitude range of 0°-10°S, suggesting a paleoequatorial cause for the death of some of the carbonate platforms, or within a crisis age range of 100-110 Ma, suggesting a cause of death of some of the carbonate platfor...

Nutrient control of the global occurrence of isolated carbonate banks

“…Indeed Larson et al (1995) and Wilson et al (1998) suggested that equatorial upwelling probably resulted in the drowning of Pacific atolls during Cretaceous times.…”

Late Cenozoic sea level and the rise of modern rimmed atolls

“…Plate cooling models (Stein and Stein, 1992) predict a subsidence rate of 14-18 m/Myr over the past 8.5 Ma for Enewetak, assuming thermal reset of the crust during island formation (Detrick and Crough, 1978;Li et al, 2004). Likewise, a mean subsidence rate of 19.5 m/Myr since the late Cretaceous can be estimated from cores drilled on Wodejebato guyot (submerged 1485 mbsl), 250 km east of Enewetak (Larson et al, 1995). In general, long-term subsidence rates of western Pacific Ocean guyots (drowned atolls) drilled as part of ODP Leg 144 range from 15.8 to 29.0 m/Myr (Larson et al, 1995).…”

“…Likewise, a mean subsidence rate of 19.5 m/Myr since the late Cretaceous can be estimated from cores drilled on Wodejebato guyot (submerged 1485 mbsl), 250 km east of Enewetak (Larson et al, 1995). In general, long-term subsidence rates of western Pacific Ocean guyots (drowned atolls) drilled as part of ODP Leg 144 range from 15.8 to 29.0 m/Myr (Larson et al, 1995).…”

Reply to: Terry, J. and Goff, J. comment on “Late Cenozoic sea level and the rise of modern rimmed atolls” by Toomey et al. (2016), Palaeogeography, Palaeoclimatology, Palaeoecology 4 51: 73–83.

“…Hawaiian Islands: Moore et al, 1989;Reunion: Oehler et al, 2008). Atolls in the Marshall Islands, where our main study site Enewetak Atoll is located, are likely~50-100 million years old (Larson et al, 1995) and dating of adjacent deep-water turbidite aprons in the Nauru Basin (DSDP Site 462; Schlanger and Silva, 1986) suggests that large atoll flank collapse events have been relatively infrequent there since the mid-Miocene (b11 Ma). In our simple, 1D atoll development model (Toomey et al, 2016a), we included the minimum set of processes (vertical accretion, dissolution, and lagoonal infilling) required to accurately simulate Enewetak's 'recent' depositional history (8.5-0 Ma) and explain basic differences in lagoon depth among western Pacific atolls.…”