Karst Morphology and Diagenesis of the Top of Albian Limestone Platforms, Mid-Pacific Mountains

Abstract

The upper surface of the Albian platform limestone on many Mid-Pacific Mountains (MPM) guyots, as shown by multibeamsonar, bathymetric data, and seismic-reflection data from where pelagic sediments have buried the Albian platform limestone, shows that the top of the limestone sequence has been sculptured by streams, by waves, and by dissolution during an episode of emergence to heights of as much as 180 m above sea level. Seismic-reflection profiles show that the surface is arched over the buried volcanic basement, reflecting progressive differential compaction of the limestone section over erosional relief on the basement. This compaction began during early stages of burial of limestone layers and continued after final drowning of the platform. On some guyots, differential erosion left a prominent perimeter rim several tens of meters high. This atoll-like erosional form was drowned in post-Albian, pre-mid-Turonian time, with no further accumulation of platform limestone. Petrographic and stable-isotopic studies of samples recovered in drill holes in the upper parts of the platform limestone on Allison and Resolution guyots show dissolution cavities tens of meters below the top of the limestone, some filled with pelagic sediments and others still open and lined with stalagmite-like calcite structures and cements showing evidence of accumulation in vadose environments.

Stratigraphic evolution and karstification of a Cretaceous Mid‐Pacific atoll (Resolution Guyot) resolved from core‐log‐seismic integration and comparison with modern and ancient analogues

“…100.45 ± 1 Ma (marked by SS5). Our findings of two major karstification events before the demise may support the hypothesis of ‘death‐by‐emergence‐and‐submergence’ by Winterer et al (1995) and Winterer (1998).…”

“…The study has revealed clear evidence of two subaerial exposure events in the mid (105.15 ± 1 Ma) and late Albian (100.45 ± 1 Ma), which may support the hypothesis of ‘death‐by‐emergence‐and‐submergence’ by Winterer et al (1995) and Winterer (1998). Syndepositional fractures at the rims interacted with the subaerial exposure events by focusing the dissolution which formed vertically stacked flank‐margin fracture‐cave system.…”

“…Our work sheds new light on the debated subaerial exposure and karstification of the Albian succession of the Mid‐Pacific Mountains atolls (Jenkyns & Wilson, 1999; Wilson et al, 1998; Winterer, 1998; Winterer et al, 1995). Here, we present detailed subsurface geomorphological evidence for two karstification episodes during the Albian (Figures 6 and 10).…”

“…The diagenetic history of the Resolution Guyot carbonates based on core data is relatively simple including marine and meteoric diagenesis and late diagenetic dolomitization (Flood & Chivas, 1995; Röhl & Strasser, 1995). The presence of meteoric diagenesis is still debated: the irregular surface of the upper Albian carbonates below the pelagic cap observed in 3.5‐kHz echo‐soundings and seismic profiles is interpreted as evidence for subaerial exposure (Winterer, 1998; Winterer et al, 1995), but oxygen and carbon isotope signature of bulk carbonates and calcitic cements do not offer any supporting evidence of meteoric diagenesis (Jenkyns & Wilson, 1999; Wilson et al, 1998). This observation has raised the debate of whether the Pacific Cretaceous atolls have ever experienced subaerial exposure and karstification before their demise.…”

“…This observation has raised the debate of whether the Pacific Cretaceous atolls have ever experienced subaerial exposure and karstification before their demise. This debate was reflected on the hypotheses for the demise of the Mid‐Pacific atolls, which are: (1) ‘death‐by‐emergence‐and‐submergence’ (Winterer, 1998; Winterer et al, 1995) and (2) ‘death‐in‐tropics’ (Jenkyns & Wilson, 1999; Larson, 1991; Wilson et al, 1998).…”