Bowen

Campbell

Dutton

Gary M. McMurtry

Gerard J. Fryer

Hearty

J. Frisbee Campbell

Jan Fietzke

Lisiecki

Ludwig

McMurtry

Sherman

Stearns

Watts

McMurtry, Gary M.

Campbell, J. Frisbee

Fryer, Gerard J.

Fietzke, Jan

OceanRep

Geologydoi: 10.1130/G32067Y.1 2011;39;e236-e237Geology Gary M. McMurtry, J. Frisbee Campbell, Gerard J. Fryer and Jan Fietzke deposits: REPLYUplift of Oahu, Hawaii, during the past 500 k.y. as recorded by elevated reef  Email alerting servicescite this article to receive free e-mail alerts when new articleswww.gsapubs.org/cgi/alertsclick Subscribe  to subscribe to Geologywww.gsapubs.org/subscriptions/click Permission request  to contact GSAhttp://www.geosociety.org/pubs/copyrt.htm#gsaclick viewpoint. Opinions presented in this publication do not reflect official positions of the Society.positions by scientists worldwide, regardless of their race, citizenship, gender, religion, or politicalarticle's full citation. GSA provides this and other forums for the presentation of diverse opinions and articles on their own or their organization's Web site providing the posting includes a reference to thescience. This file may not be posted to any Web site, but authors may post the abstracts only of their unlimited copies of items in GSA's journals for noncommercial use in classrooms to further education andto use a single figure, a single table, and/or a brief paragraph of text in subsequent works and to make GSA,employment. Individual scientists are hereby granted permission, without fees or further requests to Copyright not claimed on content prepared wholly by U.S. government employees within scope of theirNotes© 2011 Geological Society of America on February 10, 2012geology.gsapubs.orgDownloaded from GEOLOGY FORUM, March 2011 e236REPLY: doi:10.1130/G32067Y.1Gary M. McMurtry1, J. Frisbee Campbell2, Gerard J. Fryer3, and Jan Fietzke41University of Hawaii, Manoa, Honolulu, Hawaii 96822, USA2University of Hawaii, Manoa, Honolulu, Hawaii 96822, USA (Retired)3 Pacifi c Tsunami Warning Center, 91-270 Fort Weaver Road, Ewa Beach, Hawaii 96706-2928, USA4 Biogeochemie Leibniz-Institut für Meereswissenschaften, IFM-GEOMAR Dienstgebäude Ostufer, 8E-105 Wischhofstraße 1-3, D-24148 Kiel, GermanyHerein, we rebut Hearty’s (2011) claims about our data and interpre-tations, which hopefully will help bring some clarity to the issue of Oahu’s uplift over the past 500 k.y.QUALITY OF CORAL SAMPLESA plot of 230Th/238U versus 234U/238U showing the trend of ideal closed-system behavior over time is often used to evaluate the quality of U-series dates of coral samples. Reasonable dates fall within the 5% band of uncertainty in the initial seawater 234U/238U ratio at their respective times. Of the Kahe Point and older Ko Olina coral samples, only two of the fi ve dates for each group fall above this band, suggesting some open-system behavior. Of these four samples, only one shows excessively high calcite of 12% and Th of 30 ppb. The rest contain <2.5% calcite and <5 ppb Th. Open-system corrections previously made for these dates reduce their apparent ages by a few thousand years for most samples reported in our Table DR1 in GSA Data Repository item 2010005.We agree with the comment “such allochthonous cobbles may have been emplaced by younger transgressions or tsunami,” and that possibil-ity, plus the anomalously high elevations of these deposits, were used to reject them from our original linear regression analysis of reef uplift. Therefore, concerns about the poor quality of these dates, with which we disagree, are rendered moot.LINEAR UPLIFT AND CORRELATIONS OF SHORELINESThe regression coeffi cient of r = 0.999 simply expresses that the mean or single ages of the coral samples from each elevated reef, and their maxi-mum estimated elevations, are highly linearly correlated, which extends for over 500 k.y. This linear uplift for Oahu is no more improbable than the pre-viously determined linear subsidence rates over the same period for islands southeast of Oahu (Campbell, 1986; Ludwig et al., 1991). Comments about “nonlinear processes of migrating forebulge ‘waves’ generated by crustal loading at multiple volcanic centers over time” have no reference to evalu-ate. Over the past 500 k.y., loading of the lithosphere beneath Hawaii has been mainly from the massive Hawaii Island volcanoes that abut each other, and have been modeled as a single point source (Watts and ten Brink, 1989).EXTRAPOLATED VERSUS ACTUAL INTERGLACIAL SEA LEVELSWe are interested in the maximum elevation of each elevated reef, not other, lower stands of the sea. Therefore, we do not see the relevance of “an early, sustained position at +5 m at ca. 127 ka” for MIS 5 reefs measured by Hearty et al. (2007). Stearns (1978) measured the maximum height of the MIS 5 reef on Oahu from two wave-cut notches at +8.2 and +6.7 m asl, and used +7.6 m asl as the most representative maximum height found elsewhere amongst this extensive reef exposure, where the two notches were often not observed. Dismissing maximum reef elevations and using lower ones obviously leads to slower uplift rates, even without resort to dubious corrections based upon claims of eustatic sea level from “stable platforms” elsewhere, e.g., see commentary by Bowen (2010).MIS 7Sherman et al. (1999) found reef corals dated to MIS 7 at water depths of −10 m. Deeper reef corals at −13 m date to 280 ± 2 ka (MIS 8?), and those at −27 to −30 m date to 97 ± 6 and 83 ± 5 ka (MIS 5.3 and 5.1, respectively). The deeper coral reefs are not relevant to this Reply.MIS 7 has been resolved into three main peaks of sea level lower than present: MIS 7.1, 7.3, and 7.5, separated by rapid drops in sea level (Dut-ton et al., 2009). The Sherman et al. (1999) coral dates for MIS 7 fi t within these periods of lower sea level (MIS 7.4 and prior to MIS 7.5 peak), and in fact better fi t the eustatic sea-level curve (Lisiecki and Raymo, 2005) when corrected for linear uplift. We were concerned with maximum inter-glacial reef positions, so inclusion of the Sherman et al. (1999) lower reef elevations was not considered relevant.MIS 9If the Ko Olina deposits result from storms or tsunami, as we previ-ously suggested, then they would represent a maximum elevation for Stage 9 on Oahu. Stearns (1978) originally described these deposits as “bedded beach conglomerates.” We suspect that the single coral date of 334 ± 17 ka (closed) from the nearby, extensive Lualualei reef at +21 m asl is correct, but the coral is altered, and yields an older, open-system date of 372 ± 17 ka.MIS 11We consider the uplift rates derived from the mostly undated strati-graphic sequence at Waianae Health Center (Hearty, 2002) to be circular. A more reliable approach would produce accurate dates of highstand reefs in situ at their apex elevations.MIS 13 AND 15Hearty ironically uses proxy data (δ18O records) to argue for lower MIS 13–15 reef elevations. At present, corals dated from the Kaena Stand at +29–30 m asl on Oahu have mean ages from 468 to 547 ka (McMurtry et al., 2010). These ages have large analytical uncertainties, but appear to best coincide with MIS 13, and their measured elevations are consistent with linear uplift for Oahu, based upon the other elevated reefs there used in our analysis.CONCLUSIONSHearty dismisses all U-series ages of corals >130 ka reported for Oahu as being defi nitive of any interglacial period, including his own TIMS data for the Kaena Stand (Hearty, 2002). Older U-series coral dates have larger uncertainties, because of the increased chance of exposure to weathering and open-system behavior over time. However, when plotted with means of coral dates <130 ka, most of these older dates continue to defi ne a linear trend in age elevation. The rest of Hearty’s conclusions are opinions, among them that MIS 11 should not be missing from the geo-logic record on Oahu, and suggesting a paradox if it is missing when other Uplift of Oahu, Hawaii, during the past 500 k.y. as recorded by elevated reef deposits: REPLY© 2011 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or editing@geosociety.org. on February 10, 2012geology.gsapubs.orgDownloaded from GEOLOGY FORUM, March 2011 e237highstands of lesser duration are represented there. Beyond stating the ob-vious Est quod est, perhaps the best approach would indeed be “diligent fi eldwork, the use of pristine, in-situ samples, and accurate age determina-tions.” We agree with this ideal.REFERENCES CITEDBowen, D.Q., 2010, Interactive Comment on “Comment on ‘Sea level 400,000 years ago (MIS 11): Analogue for present and future sea-level?’ by D.Q. Bowen (2010) Can the extrapolation of uplift rates from MIS 5e shorelines to MIS 11 replace direct and tangible evidence of the latter’s sea-level history?” by P.J. Hearty: Climate of the Past Discussions, v. 6, p. C128–C133.Campbell, J.F., 1986, Subsidence rates for the southeastern Hawaiian Islands determined from submerged terraces: Geo-Marine Letters, v. 6, p. 139–146, doi:10.1007/BF02238084.Dutton, A., Bard, E., Antonioli, F., Esat, T.M., Lambeck, K., and McCulloch, M.T., 2009, Phasing and amplitude of sea-level and climate change during the penultimate interglacial: Nature Geoscience, v. 2, p. 355–359, doi:10.1038/ngeo470.Hearty, P.J., 2002, The Ka’ena highstand of O’ahu, Hawai’i: Further evidence of Antarctic ice collapse during the middle Pleistocene: Pacifi c Science, v. 56, p. 65–81, doi:10.1353/psc.2002.0004.Hearty, P.J., 2011, Uplift of Oahu, Hawaii, during the past 500 k.y. as recorded by elevated reef deposits: Comment: Geology, doi:10.1130.G31749C.1.Hearty, P.J., Hollin, J.T., Neumann, A.C., O’Leary, M.J., and McCulloch, M., 2007, Global fl uctuations during the last integlaciation (MIS 5e): Quaternary Science Reviews, v. 26, p. 2090–2112, doi:10.1016/j.quascirev.2007.06.019.Lisiecki, L.E., and Raymo, M.E., 2005, A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records: Paleoceanography, v. 20, PA1003, doi:10.1029/2004PA001071.Ludwig, K.R., Szabo, B.J., Moore, J.G., and Simmons, K.R., 1991, Crustal subsidence rate off Hawaii determined from 234U/238U ages of drowned coral reefs: Geology, v. 19, p. 171–174, doi:10.1130/0091-7613(1991)019<0171:CSROHD>2.3.CO;2.McMurtry, G.M., Campbell, J.F., Fryer, G.J., and Fietzke, J., 2010, Uplift of Oahu, Hawaii, during the past 500 k.y. as recorded by elevated reef deposits: Geology, v. 38, p. 27–30, doi:10.1130/G30378.1.Sherman, C.E., Fletcher, C.H., and Rubin, K.H., 1999, Marine and meteoric diagenesis of Pleistocene carbonates from a nearshore submarine terrace, Oahu, Hawaii: Journal of Sedimentary Research, v. 69, p. 1083–1097.Stearns, H.T., 1978, Quaternary shorelines in the Hawaiian Islands: Bernice P. Bishop Museum Bulletin 237: Honolulu, Bishop Museum Press, 57 p.Watts, A.B., and ten Brink, U.S., 1989, Crustal structure, fl exure, and subsidence history of the Hawaiian islands: Journal of Geophysical Research, v. 94, p. 10473–10500, doi:10.1029/JB094iB08p10473. on February 10, 2012geology.gsapubs.orgDownloaded from 

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