Early Pleistocene origin of reefs around Lanai, Hawaii

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• 作者：Jody M. Webster ; David A. Clague ; Iain D.E. Faichney ; Paul D. Fullagar ; James R. Hein ; James G. Moore ; Charles K. Paull
• 关键词：Hawaii ; Lanai ; early Pleistocene ; Sr isotope stratigraphy ; coral reef evolution
• 刊名：Earth and Planetary Science Letters
• 出版年：2010
• 出版时间：20 February 2010
• 年：2010
• 卷：290
• 期：3-4
• 页码：331-339
• 全文大小：2058 K

文摘

A sequence of submerged terraces (L1–L12) offshore Lanai was previously interpreted as reefal, and correlated with a similar series of reef terraces offshore Hawaii island, whose ages are known to be < 500 ka. We present bathymetric, observational, lithologic and 51 ⁸⁷Sr/⁸⁶Sr isotopic measurements for the submerged Lanai terraces ranging from − 300 to − 1000 m (L3–L12) that indicate that these terraces are drowned reef systems that grew in shallow coral reef to intermediate and deeper fore-reef slope settings since the early Pleistocene. Age estimates based on ⁸⁷Sr/⁸⁶Sr isotopic measurements on corals, coralline algae, echinoids, and bulk sediments, although lacking the precision ( ± 0.23 Ma) to distinguish the age–depth relationship and drowning times of individual reefs, indicate that the L12–L3 reefs range in age from  1.3–0.5 Ma and are therefore about 0.5–0.8 Ma older than the corresponding reefs around the flanks of Hawaii. These new age data, despite their lack of precision and the influence of later-stage submarine diagenesis on some analyzed corals, clearly revise the previous correlations between the reefs off Lanai and Hawaii. Soon after the end of major shield building ( 1.3–1.2 Ma), the Lanai reefs initiated growth and went through a period of rapid subsidence and reef drowning associated with glacial/interglacial cycles similar to that experienced by the Hawaii reefs. However, their early Pleistocene initiation means they experienced a longer, more complex growth history than their Hawaii counterparts.