This article was published in an Elsevier journal. The attached copyis furnished to the author for non-commercial research and

education use, including for instruction at the author’s institution,sharing with colleagues and providing to institution administration.

Other uses, including reproduction and distribution, or selling orlicensing copies, or posting to personal, institutional or third party

websites are prohibited.

In most cases authors are permitted to post their version of thearticle (e.g. in Word or Tex form) to their personal website orinstitutional repository. Authors requiring further information

regarding Elsevier’s archiving and manuscript policies areencouraged to visit:

http://www.elsevier.com/copyright

Author's personal copy

Discussion

Reply to “Mega-highstand or megatsunami? Discussion of McMurtry et al.“Elevated marine deposits in Bermuda record a late Quaternary

megatsunami”: Sed. Geol. 200 (2007) 155–165”by Paul J. Hearty and Storrs L. Olson

Gary M. McMurtry a,⁎, David R. Tappin b, Peter N. Sedwick c,Ian Wilkinson b, Jan Fietzke d, Bruce Sellwood e,1

a School of Ocean and Earth Science and Technology, University of Hawaii, Manoa, Honolulu, Hawaii 96822, USAb British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham NG 12 5GG, UK

c Bermuda Institute of Ocean Sciences, St George's, GE01, Bermudad Biogeochemie Leibniz-Institut für Meereswissenschaften, IFM-GEOMAR Dienstgebäude Ostufer, 8E-105 Wischhofstraße 1-3, D-24148 Kiel, Germany

e Department of Geography, School of Human and Environmental Sciences, The University of Reading, Whiteknights, Reading RG6 6AB, UK

Received 15 September 2007; received in revised form 31 October 2007; accepted 27 November 2007

Abstract

Our recent paper [McMurtry, G.M., Tappin, D.R., Sedwick, P.N., Wilkinson, I., Fietzke, J. and Sellwood, B., 2007a. Elevated marine deposits inBermuda record a late Quaternary megatsunami. Sedimentary Geol. 200, 155–165.] critically re-examined elevated marine deposits in Bermuda, andconcluded that their geological setting, sedimentary relations,micropetrography andmicrofaunal assemblageswere inconsistent with sustained intertidaldeposition. Instead, we hypothesized that these deposits were the result of a large tsunami that impacted the Bermuda island platform during the mid-Pleistocene. Hearty andOlson [Hearty, P.J., andOlson, S.L., in press.Mega-highstand ormegatsunami?Discussion ofMcMurtry et al. “Elevatedmarinedeposits in Bermuda record a late Quaternary megatsunami”: Sedimentary Geology, 200, 155–165, 2007 (Aug. 07). Sedimentary Geol. 200, 155–165.]in their response, attempt to refute our conclusions and claim the deposits to be the result of a +21 m eustatic sea level highstand during marine isotopestage (MIS) 11. In our reply we answer the issues raised by Hearty and Olson [Hearty, P.J., and Olson, S.L., in press. Mega-highstand or megatsunami?Discussion of McMurtry et al. “Elevated marine deposits in Bermuda record a late Quaternary megatsunami”: Sedimentary Geology, 200, 155–165,2007 (Aug. 07). Sedimentary Geol. 200, 155–165.] and conclude that the Bermuda deposits do not provide unequivocal evidence of a prolonged +21meustatic sea level highstand. Rather, the sediments are more likely the result of a past megatsunami in the North Atlantic basin.© 2008 Elsevier B.V. All rights reserved.

1. Introduction

Hearty and Olson (in press) claim that their hypothesis of asustained eustatic sea level highstand during marine isotopestage (MIS) 11 is based on a diverse set of field and laboratorydata, and offer a number of counter-arguments to our recent re-

interpretation of these elevated marine deposits in Bermuda asthe result of rapid deposition from an Atlantic megatsunami(McMurtry et al., 2007a). We address these issues following theorder of their discussion.

2. The issues

2.1. Supposed variation in elevation of the deposits between+18 and +28 m

With regard to the elevations of the Bermuda marine depositsdiscussed by McMurtry et al. (2007a), we quoted values fromprevious published work: +18 m from Hearty et al. (1999) for

Available online at www.sciencedirect.com

Sedimentary Geology 203 (2008) 313–319www.elsevier.com/locate/sedgeo

⁎ Corresponding author.E-mail addresses: garym@soest.hawaii.edu (G.M. McMurtry),

drta@bgs.ac.uk (D.R. Tappin), peter.sedwick@bios.edu (P.N. Sedwick),ipw@bgs.ac.uk (I. Wilkinson), jfietzke@ifm-geomar.de (J. Fietzke),B.W.Sellwood@reading.ac.uk (B. Sellwood).1 Deceased, November 2, 2007.

0037-0738/$ - see front matter © 2008 Elsevier B.V. All rights reserved.doi:10.1016/j.sedgeo.2007.11.008

Author's personal copy

cave UGQ-5; +21 m from Hearty et al. (1999) for cave UGQ-4;and +28 m for the “terrace” site from Land et al. (1967). If oneof the co-authors of the Land et al. (1967) article, Fred T.Mackenzie, has provided a lower elevation of +70 ft or +21 mheight (Fig. 2 of Hearty and Olson, in press), then we acceptthe lower figure for that site. Reducing the height or the rangeof deposit elevations on Bermuda may be more consistentwith their highstand hypothesis, but it is in no way inconsis-tent with our hypothesis, which asserts that these depositsreflect sediments deposited inside karst caves as the result of amegatsunami.

Concerning the geological setting of the Land et al. (1967) site,Hearty andOlson (in press) quote a personal communication fromLand describing the site as “…deposited against an eroded cliff,which doesn't suggest a tsunami deposit…”, and further mention apersonal communication from Fred Mackenzie describing thesite as “…an erosional nip in theWalsingham cliff…”. In response,we note that Fred Mackenzie generously provided us with aphotograph of the Land et al. (1967) site, which has since beendestroyed by quarrying operations (reproduced as Fig. 5 inMcMurtry et al., 2007a). Close inspection of that photographreveals a steep cliff face of recently-exposed eolianite, with theLand et al. (1967)marine deposit at the apex, inwhat appears to bea solution cavity exposed by quarrying. Indeed, this interpretationis supported by aerial photographs of Government Quarry (Fig. 2of McMurtry et al., 2007a), which reveal that the Land et al.(1967) site (located on the figure by Fred Mackenzie) was not acliff nor escarpment prior to the 1940s. We conclude that thissitewas exposed by quarrying operations prior to its description inthe 1960s, and subsequently destroyed by continued quarrying.Therefore, it is disingenuous to maintain that the Land et al.(1967) site was an eroded sea cliff. We suggest that the Land et al.(1967) marine deposits were remnants of karst cave infillings,similar to those described in the Bermuda Government Quarrycaves UGQ-4 and UGQ-5 (Hearty et al., 1999), which wereclearly exposed by quarrying operations (see Fig. 2 in McMurtryet al., 2007a). It is similarly disingenuous to refer to these dead-end karst caves as “coastal caves” (Hearty andOlson, 2007), sinceaerial photographs (Fig. 2 in McMurtry et al., 2007a) show thatthese caves were located tens of meters inland from any sig-nificant escarpment—and hence were subterranean—prior to the1940s.

2.2. The sedimentology of the deposits and conflictinginterpretations

There are numerous published articles that describe thelithology and sedimentology of tsunami deposits, among thempapers published in a recent special issue of Sedimentary Geology“Sedimentary Features of Tsunami Deposits—Their Origin,Recognition and Discrimination” (v. 200, 3–4, 2007). Relevantpapers describing such deposits include Moore andMoore (1984,1988), Moore et al. (1994), Moore (2000), Felton et al. (2000),McMurtry et al. (2004a), and Dawson and Stewart (2007).Tsunami inundation deposits are typically poorly sorted, chaoticboulder conglomerates, with mixtures of rounded (beach) andsubangular (land) boulders and cobbles supported in a sandy,

sometimes shelly or coral-bearing, variably-graded matrix.In Hawaii, such deposits are usually massive, draping and un-graded to reversely graded and the boulders are mainly basaltic(McMurtry et al., 2004a,b). In the deposits we examined inBermuda, the boulders are rounded eolianite, but the settingof boulders—suspended in a finer, marine carbonate matrix—is strikingly similar to the Hawaii deposits (Fig. 1). We areperplexed that Hearty and Olson (in press) take issue with ourdescription of the Bermuda quarry deposits, which contain sand,pebbles, cobbles and boulders, as ‘poorly sorted'. We are alsopuzzled by their assertion that “… any level of sorting requires theelement of time and oscillatory swash effects of waves …”, giventhat tsunamis are known to produce deposits that range frompoorly to moderately sorted (e.g., see Dawson and Stewart, 2007;Jaffe and Gelfenbaum, 2007; Moore et al., 2007).

Hearty and Olson (in press) suggest that the absence ofterrestrial soils and vegetation within the Bermuda quarry

Fig. 1. (A) Photograph of megatsunami deposit sections located in Kohala,Hawaii (McMurtry et al., 2004a). Approximate unit boundaries outlined in red.Upper unit 2 is marine fossiliferous, basalt boulder conglomerate dated to withinstage 5; lower unit 3 is afossiliferous calcareous, basalt boulder conglomeratelikely correlated to within stage 7. Loose gray boulders of the Hawi Seriesandesite overly these conglomerates. David Tappin (1.8 m height) and hammerfor scale. (B) Photograph of a section of the marine conglomerate preserved inkarst cave UGQ-5, Government Quarry, Bermuda (McMurtry et al., 2007a).Upper and lower boundaries of marine conglomerate are outlined in red, eoliniteboulders in yellow. Eugene Domack (1.75 m height) for scale.

314 G.M. McMurtry et al. / Sedimentary Geology 203 (2008) 313–319

Author's personal copy

deposits is inconsistent with a tsunami origin. In response, wenote that our description of the Land et al. (1967) site depositdoes mention marsh and mangrove microfaunal species, alongwith diverse marine microfauna including those from thepelagic realm; both end-member environments are not repre-sented in modern beach deposits on Bermuda (McMurtry et al.,2007a). Terrestrial soils (eolianites dominated by Saharan dust;Herwitz et al., 1996) are volumetrically rare in Bermuda'sgeological record (Vacher and Rowe, 1997), so the chances thatthey would be incorporated in sediments deposited by a tsunamiare slim. Similarly, terrestrial vegetation, although not rareon modern Bermuda, is easily oxidized upon burial in vadoseenvironments, and hence likely to be poorly preserved aftersome 400 ka.

Hearty and Olson (in press) also argue that marine sedimentsdeposited by a tsunami should be more widespread in thegeologic record of Bermuda, if such a tsunami had inundatedthe island. Tsunami wave sets can indeed inundate entire is-lands if large enough; however, because they are isolatedepisodic events, as opposed to the sustained presence of asea level highstand, the deposits that result from a tsunamiare immediately subject to erosional processes. Such depositsare readily lost from the geologic record, except in certainsheltered settings, such as the previously subterranean cavesin the Bermuda Government quarry. In Hawaii, where thereis overwhelming evidence of several large, late Quaternarymegatsunami events (Moore and Moore, 1984, 1988; Mooreet al., 1994; Moore, 2000; McMurtry et al., 2004a), the sedi-ments deposited from these events are only preserved on the drysouthern and western coasts, where rainfall is low. Conversely,we would expect the sustained presence of a sea level highstandduring MIS-11 to yield more widely preserved paleo-shorelinedeposits on Bermuda, rather than a few isolated deposits withinkarst caves.

The final paragraph of Section 2.2 in Hearty and Olson (inpress) is basically conjecture as to how these authors believe atsunami should behave upon reaching the platform and island ofBermuda. The key problem for them is the presence of bothrounded conglomerate (including boulder-sized clasts) anddelicate structures such as vertebrate and invertebrate fossils inthe Bermuda deposits, if such deposits were the result of atsunami. Yet these same authors have claimed that fragilebird fossils preserved in mid-Pleistocene outcrops on CoopersIsland, Bermuda, reflect a single rapid event of burial, “… becauseeggs were preserved intact, as well as articulated skeletons ofembryos or recently hatched chicks and older juveniles whosesoft, porous bones would have been abraded and pulverizedunder any other circumstances …” (Olson and Hearty, 2003,p. 12825). In discussing these fossils, Olson and Hearty (2003)invoked a “… major storm …” that “… apparently struck theisland from the south …”, since the nesting site was wellprotected from northerly winter storms. We submit thatthis burial event could also have been a tsunami that impactedBermuda from the east (see Fig. 1 of Olson and Hearty, 2003),which is consistent with a tsunami originating from the CanaryIslands. In any event, these authors seem to want it both ways,first arguing for rapid burial of fossils (Olson and Hearty,

2003), and now arguing for delicate fossils preserved by“… attenuating wave energy as the cave fills with sedimentsalong a predominately quiet shoreline…” (Hearty and Olson, inpress). We maintain that the elevated, poorly sorted marinedeposits in the Bermuda Government Quarry, which includewell preserved fossils from a variety of habitats, are entirelyconsistent with rapid, episodic deposition by a tsunami.

2.3. Post-depositional cementation: petrography of bindingcements in marine sediments

We surmise from the arguments presented in Section 2.3 ofHearty and Olson (in press) that these authors consider sedimentdeposition within the caves at Bermuda Government Quarry asoccurring either on a continuously-wet shoreline or during abrief tsunami event. In fact, these karst caves have been wet anddry over long time periods, hence the various generations offlowstones below and capping the marine conglomerates. Fromour work (McMurtry et al., 2007a) and Hearty et al. (1999), werecognize flowstone generations from interglacial stages 17/15(basal), 11, 9 (?) and 5e (capping) in these caves. Theseflowstone deposits were precipitated by groundwater enteringthe caves, hence there has been ample opportunity for carbonatecements to form under both freshwater phreatic and freshwatervadose conditions. The suggestion that a Ghyben-Herzberg lenswould be required to form such cements in these settingsconveniently ignores the water-retention possibilities of theprevious, basal flowstones in caves UGQ-4 and UGQ-5, forexample. Here our data and reasoning do not controvert ourinterpretation.

To counter our “dismissive views” regarding isopachous rimcements, Hearty and Olson (in press) present additionalphotomicrographs of deposits in cave UGQ-4 (Bermuda), of20-m elevation marine deposits from Eleuthera, Bahamas, andof 30-m elevation deposits from Kaena Point, Oahu, Hawaii(their Fig. 5). Of these sites, we accept only the Kaena Pointdeposit as a sea level highstand, representing the highly linearuplift of Oahu of 0.060+/−0.001 mm/yr, rather than the loweruplift rate of 0.02 mm/yr that is circuitously reasoned by Hearty(2002) and Hearty and Olson (in press); further, we note thatdated in situ corals from the Kaena Point site and other elevateddeposits on Oahu indicate that this ancient shoreline representsMIS-13 (McMurtry et al., 2007b). Interestingly, only this depositsolely displays early marine isopachous rim cements, with nolater cements (their Fig. 5). In all other deposit photomicro-graphs, we see the early, marine isopachous rim cementssurrounded by later generations of sparry calcite cements. Theseouter cements are more consistent with formation under vadoseconditions, in agreement with our assertion that original marinematerials (like shell and coral) were emplaced in an elevated,terrestrial, freshwater-dominated environment, in which themarine grains were subsequently cemented by calcite spar.

2.4. The significance of fossil microfauna and macrofauna

Regarding our microfaunal analysis, Table 1 of McMurtryet al. (2007a) compares microfauna from the Land et al. (1967)

315G.M. McMurtry et al. / Sedimentary Geology 203 (2008) 313–319

Author's personal copy

site marine conglomerate with similar conglomerates sam-pled from Government Quarry caves UGQ-4 and UGQ-5 andsamples of modern beach sand from locations both inside andoutside of Castle Harbour (Fig. 1 of McMurtry et al., 2007a).Briefly, none of the microfaunal assemblages in the elevatedconglomerates match the modern beach sand samples, andthis dissimilarity also extends to the degree of sorting (poor tomoderately poor versus well sorted for the beach sands) andgrain size (coarse versus finer for the beach sands). As pre-viously mentioned, the Land et al. (1967) site marine con-glomerate most closely matches the modern beach samples,although it is less sorted and includes fauna typical of pelagicand marsh/mangrove environments. The remaining marineconglomerates summarized in Table 1 ofMcMurtry et al. (2007a)contain a depauperate fauna compared with the Land et al. (1967)deposit and the modern beach samples. A straightforward inter-pretation of these results is that an energetic event (the puta-tive tsunami) deposited marine materials similar to the modernbeach in one area (the Land et al., 1967 site), although coarser(winnowed?), less sorted, and incorporating species from ad-ditional environments. Other areas of the karst cave networkreceived equally coarse and poorly sorted material that is quitedissimilar in faunal diversity to the modern beach sands.

Hearty and Olson (in press) also introduce a mix ofpreviously published and new data on sediments from the sitethey have named Calonectris Quarry. We have not been able tolocate this site, and, other than the photograph in Fig. 1 ofHearty and Olson (in press), we are unable to access anyinformation regarding this site beyond that published in Olson

and Hearty (2003), Grady and Olson (2006) and Olson et al.(2005, 2006). Briefly, a mix of terrestrial and marine vertebrateand invertebrate remains has been described from this site. Asbefore, we note that Olson and Hearty (2003) have previouslysuggested that the preservation of such fragile vertebrate fossilsrequires “a single rapid event” of burial, because the fragilespecimens “would have been abraded and pulverized under anyother circumstances”. Since we are unfamiliar with the Calonec-tris Quarry deposits discussed byHearty and Olson (in press), andwith the unpublished manuscript that they cite in this regard, weare unable to assess their claims regarding the origin of thesedeposits in relation to our megatsunami hypothesis.

2.5. Past and recent U/Th dating and the timing of deposition

Three new U-series dates of Government Quarry caveflowstones are provided in Table 1 of Hearty and Olson (2007).One new date for cave UGQ-5 (364±24 ka for sample UGQ-5B) closely matches our date for this cave flowstone of 360±59 ka, whereas another sample of this cave flowstone (UGQ-5e) dates to 409±15 ka, which is closer to their new datefor cave UGQ-4 (405±28 ka) and a previously reported age of420±30 ka for flowstone in this cave (Hearty et al., 1999).Clearly, there is a range of U-series dates for these capping caveflowstones, from an age of 312±39 ka (our dates) to 420±30 ka (Hearty et al., 1999). Basically, the new dates presentedby Hearty and Olson (2007) fall within the previous rangeof ages for samples of these deposits (Fig. 2). We have no reasonto discard our younger date for cave UGQ-4, so we would tend

Fig. 2. Plot of U-series ages for samples of the capping flowstones in karst caves UGQ-4 and UGQ-5, Government Quarry, Bermuda. Age ranges of the marine isotopestages are primarily from the compilations in Kennett et al. (2003).

316 G.M. McMurtry et al. / Sedimentary Geology 203 (2008) 313–319

Author's personal copy

to use a lower, unweighted mean of 378±87 ka (n=6), notthe weighted mean of 389±26 ka (n=5) reported by Heartyand Olson (in press). Our unweighted mean is close to late MIS-11, with an uncertainty that spans both MIS-9 and MIS-11(Fig. 2). As we have previously discussed, it is possible that weinadvertently sampled different, younger flowstone material,although there is also the possibility that the younger, MIS-9age is correct.

Hearty and Olson (in press) use their weighted mean age toargue that the Government Quarry deposits cannot be related toturbidites on the Madeira abyssal plain, which have been datedand correlated with flank collapses in the Canary Islands byMasson (1996). Our response to this argument is as follows.First, one cannot focus on the mean of such ages, but mustrecognize that there is a range of estimated ages for the Bermudadeposits spanning MIS-9 through MIS-11, all of which aresubject to various uncertainties and assumptions. Secondly, theMadeira abyssal plain is a very large area, and not all turbiditesthere are likely to have been included in the results reported inMasson (1996). Thirdly, there are other age constraints on flankcollapses in the Canary Islands, with the El Julan event onHierro, the Cumbre Nueva event on La Palma, and the Orotavaevent on North Tenerife being likely candidates for theproduction of a tsunami during the period of MIS-9 throughMIS-11 (Watts and Masson, 1995; Masson, 1996; Masson et al.,2002). Fourthly, as discussed in McMurtry et al. (2007a), ourmegatsunami inundation hypothesis for Bermuda (and the

Bahamas) shows remarkable agreement with the modeled flankcollapse of La Palma and subsequent megatsunami propagationthat is described by Ward and Day (2001) (Fig. 3). And lastly,we cannot be certain that a slope failure elsewhere, for examplealong the Atlantic continental margin, did not produce the pu-tative tsunami.

Hearty and Olson (in press) also argue that an island flankcollapse and resultant tsunami are unlikely to have occurredduring the relatively brief interglacial periods of the Quaternary.On the contrary, we would argue that these are exactly theperiods during which such events are likely to occur, via aclimate-based mechanism that has been discussed in the contextof previous work in the Hawaiian Islands (McMurtry et al.,1999; McMurtry et al., 2004b), and further corroborated byrecent work in the Society Islands and elsewhere (Quidelleur etal., 2006; Hildenbrand et al., 2007). Most tsunami investigatorsnow recognize that when they occur, such slope failures andassociated submarine landslides and distal turbidity flowsrepresent sudden, catastrophic events, and do not take “days,weeks or years” to form.

3. Summary and conclusions

A primary motivation for our study was provided by themarine sediment oxygen-isotope record, which provides a proxyfor global ice volume. These records show no clear evidence fora +20 m sea level highstand during MIS-11 (Shackleton, 1987,

Fig. 3. Bathymetric map of the North Atlantic showing modeled at-sea wave train positions and wave heights at various calculated times from a proposed 500 km3

flank collapse of La Palma, Canary Islands (Ward and Day, 2001). Also shown are locations and heights of various marine deposits attributed to elevated sea levelhighstands during MIS-11 time (from Land et al., 1967; Vacher, 1971; Hearty et al., 1999; Bowen, 1999). LS=Land Slide source area on La Palma.

317G.M. McMurtry et al. / Sedimentary Geology 203 (2008) 313–319

Author's personal copy

2000; Shackleton et al., 1990; Hodell et al., 2000; Lambecket al., 2002), and thus are not consistent with the sea levelhighstand proposed by Hearty et al. (1999). Subsequent work,including high-resolution studies of deep-sea cores combinedwith interoceanic salinity modeling (McManus et al., 2007), andanalyses of Antarctic glacial ice cores (Raynaud et al., 2007) alsoprovide no evidence for such a highstand during MIS-11, nor forsignificant reduction in the volume of the East Antarctic ice sheetat that time. In this regard, the highstand hypothesis of Heartyet al. (1999) is far from parsimonious; indeed, the hypothesisappears to be untenable.

We refute the claims of Hearty and Olson (in press) that ourre-interpretation of the “shoreline deposits” in the BermudaGovernment Quarry as deposits from an Atlantic megatsunamiis based upon “a tenuous chain of assumptions, speculation andconjecture”. The sedimentology of these deposits is entirelyconsistent with what is known of tsunami deposits, includingdeposits from modern tsunamis, as is the post-depositional al-teration of these deposits in the vadose karst caves where theywere preserved. The statement by Hearty and Olson (in press)that “there is no independent evidence that a flank margin col-lapse caused a tsunami anywhere, or at anytime in the Atlantic”is uninformed. For example, there are numerous publicationsconcerning the giant Storegga landslide off the continentalmargin of Norway (Haflidason et al., 2004, 2005), includingstudies of associated tsunami deposits in Scotland, Norway andEast Greenland (Dawson et al., 1988; Bondevik et al., 2005;Wagner et al., 2007).

We do not disregard the elevated marine deposits of similarage and identical elevations in Eleuthera, Bahamas (Heartyet al., 1999; Kindler and Hearty, 2000). In fact, we suggest thatthese may constitute the “missing” Atlantic tsunami deposits,together with elevated MIS-11 “highstand deposits” describedin southern Britain (Bowen, 1999) and along the US East Coast(Vacher, 1971; Fig. 3), and we intend to re-examine these otherdeposits in this light. However, since we can show that, basedupon linear uplift, the correlated morphostratigraphic sequencein western Oahu does not belong to MIS-11 (McMurtry et al.,2007b), we must disregard the stratigraphic correlations thatHearty and Olson (in press) propose between elevated marinedeposits in Hawaii, and those in Bermuda and the Bahamas.We also note that the deposits “of similar age, elevation andcomplexity” described in the western Arctic (Kaufman andBrigham-Grette, 1993) reside in a tectonically active, mountai-nous terrain where tectonic motion is not well constrained.

We summarize our findings as follows: there are no “seacaves, terraces and erosional nips” in the karst caves that havebeen exposed by quarrying activities in the Bermuda Govern-ment Quarry, yet these caves contain conglomerates of poorlysorted marine sediments mixed with clasts and boulders ofeolianite country rock. The fact that these conglomerates weredeposited deep within a karst cave network implicates depo-sition by highly energetic, long-period waves and currents—the hallmark of tsunami, rather than short-period storm wavesand surges or “attenuating wave energy as the cave fills withsediments along a predominately quiet shoreline”. Biogenicstructures and beach fenestrae are likely transported, and not in

situ features, as are the isopachous, marine “rim” cementson carbonate grains, later surrounded by freshwater cementsformed within the vadose cave setting. The preservation ofdelicate marine and terrestrial fossils in these deposits probablyrequired a rapid burial by inundating waves, as has been pre-viously suggested by Olson and Hearty (2003). Hence, theseabirds and terrestrial vertebrates preserved in similar de-posits are likely victims of the tsunami that we hypothesizeimpacted the Bermuda island platform in the period betweenMIS-9 and MIS-11. Bermuda may indeed be “one of the best-studied carbonate islands in the world geologically”, but thatdoes not mean that the geological record of Bermuda is wellunderstood.

Acknowledgements

We thank the NSF, the National Geographic Society Com-mittee for Research and Exploration, and the G. Unger VetlesenFoundation for support of this work. We also thank ChrisFielding for his editorial assistance. David Tappin and IanWilkinson publish by permission of the Executive Director,BGS (NERC). This is SOEST Contribution number 7205. Oneof the co-authors, Bruce Sellwood, passed away shortly afterthis manuscript was revised and accepted. Bruce was engaged inand supportive of our Bermuda work right up to the end. Wewill miss his expertise and kind humanity.

References

Bondevik, S., Løvholt, F., Harbitz, C., Mangerud, J., Dawson, A., Svendsen, J.I.,2005. The Storegga Slide tsunami—comparing field observations withnumerical simulations. Mar. Petrol. Geol. 22, 195–208.

Bowen, D.Q., 1999. +23m stage 11 sea-level in southern Britain. In: Poore, R.Z.,et al. (Ed.), Marine Oxygen Isotope Stage 11 and Associated TerrestrialRecords. U. S. Dept. of the Interior, U. S. Geol. SurveyOpen File Report, vol.99–312, pp. 15–17.

Dawson, A.G., Stewart, I., 2007. Tsunami deposits in the geological record.Sedimentary Geol. 200, 166–183.

Dawson, A.G., Long, D., Smith, D.E., 1988. The Storegga Slides: evidencefrom Eastern Scotland for a possible tsunami. Mar. Geol. 82, 271–276.

Felton, E.A., Crook, K.A.W., Keating, B.H., 2000. The Hulopoe gravel, Lanai,Hawaii: new sedimentological data and their bearing on the “giant wave”(megatsunami) emplacement hypothesis. Pure Appl. Geophys. 157,1257–1284.

Grady, F.V., Olson, S.L., 2006. Fossil bats from Quaternary deposits onBermuda (Chiroptera: Vespertilionidae). Jour. Mamm. 87, 148–152.

Haflidason, H., Sejrup, H.P., Nygard, A.,Mienert, J., Byrn, P., Lien, R., Forsberg,C.F., Berg, K., Masson, D., 2004. The Storegga Slide: architecture, geometryand slide development. Mar. Geol, 213, 201–234.

Haflidason, H., Lien, R., Sejrup, H.P., Forsberg, C.F., Bryn, P., 2005. The datingand morphometry of the Storegga Slide. Mar. Petrol. Geol. 22, 123–136.

Hearty, P.J., 2002. The Ka'ena highstand of O'ahu, Hawai'i: further evidence ofAntarctic ice collapse during the middle Pleistocene. Pacific Sci. 56, 65–81.

Hearty, P.J., Olson, S.L., in press. Mega-highstand or megatsunami? Discussionof McMurtry et al. “Elevated marine deposits in Bermuda record a lateQuaternary megatsunami. Sedimentary Geology 200, 155–165 (Aug. 07).Sedimentary Geol. doi:10.1016/j.sedjeo.2007.08.001.

Hearty, P.J., Kindler, P., Cheng, H., Edwards, R.L., 1999. A +20 m middlePleistocene sea-level highstand (Bermuda and the Bahamas) due to partialcollapse of Antarctic ice. Geology 27, 375–378.

Herwitz, S.R., Muhs, D.R., Prospero, J.M., Mahan, S., Vaughn, B., 1996. Originof Bermuda's clay-rich Quaternary paleosols and their paleoclimaticsignificance. J. Geophys. Res. 101, 23389–23400.

318 G.M. McMurtry et al. / Sedimentary Geology 203 (2008) 313–319

Author's personal copy

Hildenbrand, A., Quidelleur, X., Samper, A., 2007. Causal link betweenQuaternary paleoclimatic changes and flank collapses on volcanic islands.Eos Trans. AGU 88 (23) Jt. Assem. Suppl., Abstract V31A-06.

Hodell, D.A., Charles, C.D., Ninnemann, U.S., 2000. Comparison ofinterglacial stages in the South Atlantic sector of the southern ocean forthe past 450 kyr: implications for Marine Isotope Stage (MIS) 11. GlobalPlanet. Change 24, 7–26.

Jaffe, B.E., Gelfenbaum, G., 2007. A simple model for calculating tsunami flowspeed from tsunami deposits. Sedimentary Geol. 200, 347–361.

Kaufman, D.S., Brigham-Grette, J., 1993. Aminostratigraphic correlations andpaleo-temperature implications, Pliocene–Pleistocene high sea level depos-its, northwestern Alaska. Quat. Sci. Rev. 12, 21–33.

Kennett, J.P., Cannariato, K.G., Hendy, I.L., Behl, R.J., 2003. Methane hydrates inQuaternary climate change. Am. Geophys. Un., Washington, D.C., 216 pp.

Kindler, P., Hearty, P.J., 2000. Elevated marine terraces from Eleuthera(Bahamas) and Bermuda: sedimentological, petrographic and geochronolo-gical evidence for important deglaciation events during the middlePleistocene. Global Planet. Change 24, 41–58.

Lambeck, K., Esat, T., Potter, E., 2002. Links between climate and sealevels forthe past three million years. Nature 419, 199–206.

Land, L.S., Mackenzie, F.T., Gould, S.J., 1967. The Pleistocene history ofBermuda. Geol. Soc. Am. Bull. 78, 993–1006.

Masson, D.G., 1996. Catastrophic collapse of the volcanic island of Hierro 15 kaago and the history of landslides in the Canary Islands. Geology 24,231–234.

Masson, D.G.,Watts, A.B., Gee,M.J.R., Urgeles, R., Mitchell, N.C., Lebas, T.P.,Canals, M., 2002. Slope failures on the flanks of the western Canary Islands.Earth Sci. Rev. 57, 1–35.

McManus, J., Oppo, D., Cullen, J., Benway, H., 2007. Relative climate stabilityduring marine isotope stage 11 (MIS 11). Quat. Intl. 278, 167–168 (INQUACongress, 2007, Cairns, Australia).

McMurtry, G.M., Herrero-Bervera, E., Cremer, M., Resig, J., Sherman, C.,Smith, J.R., Torresan, M.E., 1999. Stratigraphic constraints on the timingand emplacement of the Alika 2 giant Hawaiian submarine landslide.J. Volcan. Geotherm. Res. 94, 35–58.

McMurtry, G.M., Tappin, D.R., Fryer, G.J., Wilkinson, I.P., Williams, M.,Fietzke, J., Garbe-Schoenberg, D., Watts, P., 2004a. Megatsunami depositson Kohala Volcano, Hawaii, from flank collapse of Mauna Loa. Geology 32,741–744.

McMurtry, G.M., Watts, P., Fryer, G., Smith, J.R., Imamura, F., 2004b. Giantlandslides, mega-tsunamis, and paleo-sea level in the Hawaiian islands. Mar.Geol. 203, 219–233.

McMurtry, G.M., Tappin, D.R., Sedwick, P.N., Wilkinson, I., Fietzke, J.,Sellwood, B., 2007a. Elevated marine deposits in Bermuda record a lateQuaternary megatsunami. Sedimentary Geol. 200, 155–165.

McMurtry, G.M., Campbell, J.F., Fryer, G.J., Fietzke, J., 2007b. Uplift of Oahu,Hawaii over the past 500,000 years recorded by its elevated reef deposits,(Unpubl. Ms. in Prep.).

Moore, A.L., 2000. Landward fining in onshore gravel as evidence for a latePleistocene tsunami on Molokai, Hawaii. Geology 28, 247–250.

Moore, A.L., McAdoo, B.G., Ruffman, A., 2007. Landward fining frommultiple sources in a sand sheet deposited by the 1929 Grand Bankstsunami, Newfoundland. Sedimentary Geol. 200, 336–346.

Moore, J.G., Moore, G.W., 1984. Deposit from a giant wave on the island ofLanai, Hawaii. Science 226, 1312–1315.

Moore, G.W., Moore, J.G., 1988. Large-scale bedforms in boulder gravelproduced by giant waves in Hawaii, in sedimentologic consequences ofconvulsive geologic events. Spec. Pap. Geol. Soc. Amer. 229, 101–110.

Moore, J.G., Bryan, W.B., Ludwig, K.R., 1994. Chaotic deposition by a giantwave, Molokai, Hawaii. Geol. Soc. Am. Bull. 106, 962–967.

Olson, S.L., Hearty, P.J., 2003. Probable extirpation of a breeding colony ofshort-tailed albatross (Phoebastria albatrus) on Bermuda by Pleistocenesea-level rise. Proceed National Acad. Sci. 100, 12825–12829.

Olson, S.L., Wingate, D.B., Hearty, P.J., Grady, F.V., 2005. Prodromus of thevertebrate paleontology and geochronology of Bermuda. In: Alcover, J.A.,Bover, P. (Eds.), Insular Vertebrate Evolution: The Palaeontological Approach.Monogr. Soc. d'Hist. Nat. Balears, vol. 12, pp. 219–232. xiv + 390 p.

Olson, S.L., Hearty, P.J., Pregill, G.K., 2006. Geological constraints on evolutionand survival in endemic reptiles on Bermuda Jour. Herp. 40, 394–398.

Quidelleur, X., Hildenbrand, A., Samper, A., 2006. Causal link betweenQuaternary paleoclimatic changes and volcanic islands evolution. Eos Trans.AGU 87 (52) Fall Meet. Suppl., Abstract OS43C-0657.

Raynaud, D., and the EPICA community members, 2007. MIS 11 viewed fromthe Antarctic ice sheet. Quat. Intl. 167–168 (INQUA Congress, 2007,Cairns, Australia).

Shackleton, N.J., 1987. Oxygen isotopes, ice volume and sea level. Quat. Sci.Rev. 6, 183–190.

Shackleton, N.J., 2000. The 100,000-year ice-age cycle identified and foundto lag temperature, carbon dioxide, and orbital eccentricity. Science 289,1897–1902.

Shackleton, N.J., Berger, A., Peltier, W.R., 1990. An alternative astronomicalcalibration of the lower Pleistocene timescale based upon ODP Site 677.Trans. R. Soc. Edinb. Earth Sci. 81, 251–261.

Vacher, H.L., 1971. Late Pleistocene sea-level history: Bermuda evidence. Ph. D.dissertation, Northwestern Univ., Evanston, IL, 153 p.

Vacher, H.L., Rowe, M.P., 1997. Geology and hydrogeology of Bermuda. In:Vacher, H., Quinn, T.M. (Eds.), Geology and Hydrogeology of CarbonateIslands. Elsevier.

Wagner, B., Bennike, O., Klug, M., Cremer, H., 2007. First indication ofStoregga tsunami deposits from East Greenland. J. Quat. Sci., 22, 321–325.

Ward, S.N., Day, S., 2001. Cumbre Vieja Volcano—potential collapse andtsunami at La Palma, Canary Islands. Geophys. Res. Lett. 28, 3397–3400.

Watts, A.B., Masson, D.G., 1995. A giant landslide on the north flank ofTenerife (Canary Islands). J. Geophys. Res. 100, 24487–24498.

319G.M. McMurtry et al. / Sedimentary Geology 203 (2008) 313–319