Coral Terraces Research Articles

Record of MIS 5 sea-level highstands based on U/Th dated coral terraces of Haiti

New geomorphologic investigations and new U–Th series dates from Haiti (Northwestern Peninsula) confirm the age of coral reef terraces assigned to MIS 5.5 (130 ka), MIS 5.3 (107 ka) and MIS 5.1 (83 ka) sea level peaks. They also provide evidence for a second high sea level occurring some thousand years before 118 ka, and indicate a second MIS 5.1 sea level stand at about 76 ka. These results are in agreement with the raised terraces of Barbados, although the staircase of Haiti consists of four steps compared to eight. The Haitian sequence can be compared with the maximal number of distinct MIS 5 sea-level highstands recorded in the world, from coral reef tracts, and their relative height above or below present sea level. Three MIS 5.5 sea-level changes have been recognized, with sea level oscillating above or near the present level until 122 ka only, dropping, then rising to −11 m below present sea level at 120 ka. Three high-frequency sea-level oscillations occurred during MIS 5.3 and a fourth during MIS 5.3–5.2. Two or three events may have occurred during MIS 5.l, according to whether the 73 ka event is considered to belong to MIS 5.1.

Coupled climate and sea-level changes deduced from Huon Peninsula coral terraces of the last ice age

Huon Peninsula, Papua New Guinea, is a tectonically unstable, uplifting shoreline ringed by emergent coral terraces. The terraces were formed during episodes of rapid sea-level rise when corals constructed large, discrete coral platforms that were subsequently uplifted. Uranium series ages of four prominent Huon Peninsula last glacial (OIS 3) coral terraces coincide with the timing of major North Atlantic climate reversals at intervals of 6000–7000 yr between 30 000 yr and 60 000 yr ago. Terrace elevations, when combined with uplift, indicate 10–15-m high sea-level excursions at these times. We attribute the growth of the terraces directly to sea-level rises arising from ice-calving episodes from major North Atlantic ice-sheets and the Antarctic ice-sheet that precipitated extremes of cold climate called Heinrich events. These periods are associated with major discharges of land-based ice and enhanced concentrations of ice-rafted debris in deep-sea cores. Sea-levels at this time were 60–90 m lower than present.

Raised Coral Terraces at Malakula, Vanuatu, Southwest Pacific, Indicate High Sea Level During Marine Isotope Stage 3

The occurrence of a series of raised coral reefs from the uplifted island of Malakula (Vanuatu, SW Pacific) provide an opportunity to examine sea-level fluctuations over at least the past 120,000 years. Thirteen fossil coral samples from Malakula were analyzed by the thermal ionization mass spectrometry (TIMS) U/Th dating technique, yielding information on sea levels during late marine isotope stage 3 and early stage 4. Our findings are in good agreement with sea-level estimates from raised coral terraces in Papua New Guinea and the recent sea-level reconstruction from the deep-sea sedimentary δ 18O records. In particular, our coral data appear to confirm that sea levels at about 45,000–50,000 yr B.P. were only 30 to 60 m below the present level. Combined with other evidence of sea-level change, our data provide a strong case for much higher sea levels and therefore markedly reduced continental ice volume at 47,000 to 49,000 years ago.

Sea level changes forced ice breakouts in the Last Glacial cycle: new results from coral terraces

Sea level cycles recorded by coral terraces at Huon Peninsula (HP) in Papua New Guinea match rapid climate changes that occurred between 30,000 and 65,000 years ago, seen in Greenland ice cores and marine sediments. Each cycle of 6000–7000 years ended with a sea level rise of 10–15 m lasting 1000–2000 years, following a longer period of falling sea level. Precise dating shows that each rise corresponds to a “Heinrich” episode of ice-rafted detritus in north Atlantic, signalling massive ice outbreak from north America. Sea level may be the trigger that forced near-synchronous breakouts of ice from north America and eastern Greenland. The HP sea level changes also correspond to similar cycles in benthic oxygen isotopes reported from the north Atlantic, which are too large to be explained entirely in terms of ice volumes. Jointly, the sea level and isotope records suggest that the north Atlantic deep ocean cooled as sea level fell and warmed as sea level rose, in each 6000-year cycle.

Last glacial sea-level change deduced from uplifted coral terraces of Huon Peninsula, Papua New Guinea

We have dated corals sampled from the uplifted terraces of Huon Peninsula, Papua New Guinea, that grew during the Marine Isotope Stage 3, to reconstruct sea-levels of the last glacial period from 30 to 55 ka (kiloannum). Mass spectrometric U-series dating methods resulted in high precision dates and could also be used to recognize diagenetically altered samples. The only quantitative test of open-system behaviour of both uranium and thorium isotopes involves the comparison of 234U/ 238U ratios, at the time of coral growth, with present sea-water values. Additional tests included checks for systematic variations in stable isotopes, X-ray diffraction to detect calcification and petrographic examination. Sea-levels were corrected for glacio-hydro-isostatic variations and also for the depth range of coral growth habitat. Sea-levels from 30 to 55 ka were approximately 80 m lower than present. Superimposed on this general trend, four periodic sea-level high-stands were found, at 6–8 ka intervals, approximately at 30, 38, 44 and 52 ka, that appear to be synchronous with rapid climate variations previously observed in ice cores and in deep sea sediments.

Last interglacial sea stands on Barbados and an early anomalous deglaciation timed by differential uplift

Three major sea level maxima between 137 and 120 kyr B.P. are documented by surveys of pairs of wave‐cut notches and other features associated with the broadly defined last interglacial coral terrace on Barbados. Regression analysis of elevation differences between notch pair members as a function of their uplift rates at seven sites yields the age difference between first and third sea stands and their eustatic sea level difference. These results, when combined with stratigraphic data from the Bahamas, Bermuda, and Western Australia and a chronology based on age limits of corals from the Bahamas and Western Australia, yield an endpoint age and eustatic low‐tide elevation of 136.7 kyr B.P. and +7.4 m, respectively, for the first sea stand, 126 kyr B.P. and +5.6 m for the second, and 120.5 kyr B.P. and +3.0 m for the third. The first sea stand is the result of an anomalous deglaciation that was completed during low northern summer Milankovitch insolation. This is contrary to the Milankovitch hypothesis that orbitally controlled insolation largely determines the variations of glacial ice volume. It implies that internal factors within the Earth's climate system can be much stronger than the effects of insolation variations.

Late Middle Pleistocene deposits at Norton Farm on the West Sussex coastal plain, southern England

The coastal plain of West Sussex, southern England, is internationally important because of the sequence of discrete high-sea-level events preserved at Various elevations across it. New evidence is presented from a site at Norton Farm, near Chichester, on the Lower Coastal Plain, where Pleistocene marine sands, fining upwards into silts, occur between 5.3 m and 9.1 m OD. The sequence reflects a regressive tendency at the transition from an interglacial to a cold stage. The marine sands have yielded foraminifera, ostracods and molluscs that indicate a declining marine influence through the sequence, culminating in a tidal mudflat, strongly weathered in places. Cool-climate foraminifera (including Elphidium clavatum, Cassidulina reniformis and Elphidium albiumbilicatum) and ostracods have been recovered from the marine sands. Some species with an apparent preference for warmer water conditions, however, are also present. Freshwater taxa washed into the terminal marine sediments include some cold climate indicators, such as Pisidium stewarti and P. obtusale lapponicum. Additional evidence for cool climatic conditions during the deposition of the upper part of the marine sequence is provided by the lack of tree taxa in the pollen record and by features of the micromorphology. The marine sediments probably began accumulating during OIS 7, a conclusion based on their elevation, on amino acid ratios from shells, but especially on vertebrate evidence, particularly the presence of a small form of horse, together with a large, distinctive, form of northern vole (Microtus oeconomus). The occurrence of cool climate indicators in these marine sediments may demonstrate a lag between the climatic deterioration and the expected glacio-eustatic fall in relative sea-level. This evidence appears to support the conclusions drawn from the study of coral terraces in Barbados. Such a scenario would provide the conditions necessary for the emplacement of the large erratic boulders reported from the Lower Coastal Plain of West Sussex. Copyright (C) 2000 John Wiley & Sons, Ltd.

Last Ice Age Millennial Scale Climate Changes Recorded in Huon Peninsula Corals

Uranium series and radiocarbon ages were measured in corals from the uplifted coral terraces of Huon Peninsula (HP), Papua New Guinea, to provide a calibration for the 14C time scale beyond 30 ka (kilo annum). Improved analytical procedures, and quantitative criteria for sample selection, helped discriminate diagenetically altered samples. The base-line of the calibration curve follows the trend of increasing divergence from calendar ages, as established by previous studies. Superimposed on this trend, four well-defined peaks of excess atmospheric radiocarbon were found ranging in magnitude from 100% to 700%, relative to current levels. They are related to episodes of sea-level rise and reef growth at HP. These peaks appear to be synchronous with Heinrich Events and concentrations of ice-rafted debris found in North Atlantic deep-sea cores. Relative timing of sea-level rise and atmospheric 14C excess imply the following sequence of events: An initial sea-level high is followed by a large increase in atmospheric 14C as the sea-level subsides. Over about 1800 years, the atmospheric radiocarbon drops to below present ambient levels. This cycle bears a close resemblance to ice-calving episodes of Dansgaard-Oeschger and Bond cycles and the slow-down or complete interruption of the North Atlantic thermohaline circulation. The increases in the atmospheric 14C levels are attributed to the cessation of the North Atlantic circulation.

Late Quaternary stratigraphy, Paleoclimate and neotectonism of the Persian (Arabian) Gulf region

The last glacial deposits in the Persian (Arabian) Gulf consist of a >22,000 year old paralic terrigenous sequence in the Mesopotamia Shelf, the foredeep in front of the Iranian Zagros Mountains and the northern side of the Biaban Shelf. Elsewhere, the Gulf, and probably the Biaban Shelf, were mantled by >30,000 year old carbonates. Comparison of 14 C data from foraminifera from the last glacial terrigenous unit in the foredeep off Iran with curves published by Hopley [Hopley, D., 1982. The Geomorphology of the Great Barrier Reef: Quaternary Development of Coral Reefs. Wiley, New York, 453 pp.] and Chapell et al. [Chapell, J., Omura, A., Tezer, E., McCulloch, M., Pandolfi, J., Ota, Y., Pillans, B., 1996. Reconciliation of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep sea oxygen isotope records. Earth Planet. Sci. Lett. 141, 227–236.] indicates that the region may have experienced uplift during the last glacial, whereas other geologic data indicate that the foredeep has had a history of continuous subsidence during the Cenozoic. A possible explanation for this discrepancy is that the foraminifera analyzed are not in place, but were reworked into shallower water during the Holocene transgression. However, the foraminifera analyzed do not display any evidence of wear, indicating that such transport was limited. A third alternative is that sea level during the last glacial was much higher than indicated by the curves of Hopley and Chapell et al. At the peak of the last glaciation 21,000 to 20,000 years ago, when sea level was 120 m lower than now, the Gulf was a waterless basin and deposition was negligible. On the Biaban Shelf, the Holocene transgressive sequence resting unconformably on last glacial sediments consists of 14,000 year old carbonates, a >11,000 year old terrigenous delta on the northern end of the Biaban Shelf and 11,000–10,000 year old intertidal–tidal aragonite deposited in a dry climate. On the northeast side of the Gulf, the last glacial sediments are covered by 10,000 to 7000 year old aragonite muds (younging toward the northwest). Resting on the aragonites on the Biaban Shelf and on the northeast and northwest sides of the Gulf are marls deposited under the present humid climate. The southwest side of the Gulf continued to be a site of carbonate deposition throughout the Holocene. Comparison of AMS 14 C measurements of the late Holocene marls with the sea level curve of Fairbanks [Fairbanks, R.G., 1989. A 17,000 year glacio-eustatic sea level record; influence of glacial melting rates and the Younger Dryas event and deep-ocean circulation. Nature 342, 637-642.] indicates that the axial zone of the Gulf off Iran experienced subsidence during the Holocene. This subsidence coupled with a rapid rise in sea level during a major glacial melt 9500 to 8500 years ago, when global sea level rose from −50 to −28 m, led to the replacement of marl with a shallow (8–25 m) water fauna by a `deep' (>50 m) water one. Similar measurements and other geologic data indicate that the Mesopotamia Shelf and the mouth of the Mesopotamian Depression on the northwest side of the Gulf underwent both subsidence and uplift during the Cenozoic. These vertical oscillations, however, were more subdued than those in the foredeep off Iran. The Arabian Shelf along the Gulf's southwest side appears to have experienced minor uplift during the Cenozoic.

Interglacial sea levels

Abstract Isotopic curves have been used as approximative estimators of global sea level. Calculations of the amplitude of sea-level variations during Interglacials, especially for the last Interglacial, are based on the study of emerged coral terraces. The application of different dating methods shows great uncertainty about the length of each Interglacial and also about the number, chronology and altitude of the different highstands that occur during each Interglacial. Data of raised marine terraces from areas with different geodynamic behaviour (Bermudas, Bahamas, Peru, Chile, Italy and Spain) are summarized in order to analyze the relationships between sea level and Interglacial stages. Two Interglacials have been identified for the early Pleistocene represented by two marine terraces with different highstands. During the early-middle Pleistocene, an Interglacial with several highstands is recorded in uplifted areas. During Isotopic Stage 11 at least one highstand with sea level equal or higher than present has been recorded. Similar sea-level behaviour can be suggested for Isotopic Stage 9. All the analyzed areas record two highstands during Isotopic Stage 7, when warm equatorial fauna migrate into the Mediterranean. During Isotopic Substage 5e at least two highstands took place with evidence of lowstands between them and at least one highstand during substage 5c with similar sea-level height above present MSL, except in Barbados and Bermuda. During Substage 5a at least one highstand has been recorded.

Rapid fluctuations in sea level recorded at huon peninsula during the penultimate deglaciation

About 140,000 years ago, the breakup of large continental ice sheets initiated the Last Interglacial period. Sea level rose and peaked around 135,000 years ago about 14 meters below present levels. A record of Last Interglacial sea levels between 116,000 years to 136, 000 years ago is preserved at reef VII of the uplifted coral terraces of Huon Peninsula in Papua New Guinea. However, corals from a cave situated about 90 meters below the crest of reef VII are 130, 000 +/- 2000 years old and appear to have grown in conditions that were 6 degreesC cooler than those at present. These observations imply a drop in sea level of 60 to 80 meters. After 130,000 years, sea level began rising again in response to the major insolation maximum at 126,000 to 128,000 years ago. The early (about 140,000 years ago) start of the penultimate deglaciation, well before the peak in insolation, is consistent with the Devils Hole chronology.

Coral record of equatorial sea-surface temperatures during the penultimate deglaciation at huon peninsula

Uplifted coral terraces at Huon Peninsula, Papua New Guinea, preserve a record of sea level, sea-surface temperature, and salinity from the penultimate deglaciation. Remnants have been found of a shallow-water reef that formed during a pause, similar to the Younger Dryas, in the penultimate deglaciation at 130,000 +/- 2000 years ago, when sea level was 60 to 80 meters lower than it is today. Porites coral, which grew during this period, has oxygen isotopic values and strontium/calcium ratios that indicate that sea-surface temperatures were much cooler (22 degrees +/- 2 degreesC) than either Last Interglacial or present-day tropical temperatures (29 degrees +/- 1 degreesC). These observations provide further evidence for a major cooling of the equatorial western Pacific followed by an extremely rapid rise in sea level during the latter stages of Termination II.

Variable rates of Late Quaternary surface uplift along the Banda Arc-Australian plate collision zone, eastern Indonesia

Abstract Radiometrically dated emergent coral terraces from southeastern Indonesia provide estimates of differential vertical strain in the Banda Arc-continent collision complex. At Semau island, two samples from the lowest emergent reef (5–7 m) yield 230 Th dates that correspond to the 5a ( c. 83 ka) sea-level highstand and a low surface uplift rate of 0.2–0.3 m per 1000 years. At Rote island, samples from the lowest emergent reef ( c. 1–2 m) on both north and south sides of the island yield late Holocene ages and an average short-term uplift rate of c. 1–1.5 m per 1000 years. Similarity of ages from different samples on the north coast of Rote suggests possible coseismic emergence. Survey data from nine emergent reefs and marine notches up to 170 m in altitude on the south side of Rote indicate that uplift rates may have been c. 1–1.5 m per 1000 years for c. 120 000–130 000 years. Combined with previous studies, these results indicate that late Quaternary surface uplift rates vary an order of magnitude along the strike of the Banda orogen. Vertical displacement rates are greatest in young parts of the orogen where the shelf-slope break recently has been underthrust beneath the orogenic wedge, as at Rote, and in older parts of the orogen where retroarc thrust faulting occurs, as at Alor island.

Decoupling post-glacial tectonism and eustasy at Huon Peninsula, Papua New Guinea

Abstract Late Quaternary uplift of coral terraces varies along the coast at northeast Huon Peninsula, Papua New Guinea, but the uplift rate has been assumed to be constant at any given locality in previous studies. Measurements indicate that rates for the last 7000 and 120 000 years were similar but this may be coincidence, because uplift at Huon Peninsula is dominated by isolated, metre-scale events with recurrence intervals around 1000 years. Using age-height data from 54 corals from the post-glacial reef, we examine the uplift rate over the last 13 000 years near Kwambu, where facies changes in a drill core indicate several uplift events before 7 ka bp . To separate uplift from sea level, a eustatic curve for Kwambu was generated by the global sea-level model described by Lambeck, recalibrated to new, Late Pleistocene sea-level data. With Barbados as a test case, predictions compare well with observations reported earlier, but predicted sea levels for Kwambu cannot be reconciled with the coral data unless the water depth of coral growth at the site was greater than estimated previously.

A review of the Milankovitch climatic beat: template for Plio–Pleistocene sea-level changes and sequence stratigraphy

The Milankovitch theory of climate change predicts that global ice volume, and hence sea-level changes, were controlled by long-term quasi-periodic variations in the earth's orbital parameters (obliquity, precession and eccentricity). δ 18O records from deep-sea cores are a proxy for sea-level changes and have an orbitally tuned chronology covering the last 5 Ma. The sea-level signal in δ 18O data from east equatorial Pacific core V19-30 is well calibrated with sea-level data from coral terraces on Huon Peninsula, New Guinea, over the last 140 ka, and with less certainty back to 340 ka. Over the last 140 ka, the sea-level contribution to benthic glacial–interglacial isotopic variation is about 1.2–1.3‰ or 0.011‰ m −1, and for core V19-30 the glacial-age temperature contribution from deep ocean cooling of 1.7°C is 0.4‰. Independent constraints on Late Pliocene sea-level changes interpreted from shallow marine continental margin records indicate that the sea-level δ 18O calibration may not have been the same over the last 2.6 Ma, and the temperature correction is unlikely to have been the same in all glacial periods and all ocean settings. Nevertheless, the astronomically tuned isotopic records from deep-sea cores provide an accurate chronology and approximate the magnitudes of sea-level changes over the last 2.6 Ma, against which the facies architecture of stratigraphic sequences can be analysed and the concepts of sequence stratigraphy properly evaluated.

Unspiked K–Ar dating of Pleistocene tholeiitic basalts from the deep core SOH-4, Kilauea, Hawaii

Tholeiitic subaerial lava flows from Kilauea (SOH-4 deep core) were successfully dated by unspiked K–Ar with 40Ar * contents as low as ≈0.1%. Ages between 436 and 42 ka were found on lavas between the depths of 1650 and 468 m. All subaerial ages are consistent with their stratigraphic position and allow us to derive a lava accumulation rate of 3.07±0.44 mm/a, which is within the range of rates determined in high 40Ar * OIBs. Age determinations on dike samples yield ages that are younger than those of the enclosing lavas. The validity of the ages was cross-checked with U-series ages of coral terraces on the northwest flank of Hawaii as determined by Ludwig et al. (1991). Dating problems seem to be restricted to a submarine pillow lava sample from level 1808 m, which gives an apparent age of ≈1 Ma, which is an overestimate with respect both to rate of construction of Kilauea and the Hawaiian plume history.

Late Quaternary paleolandslides on the coral terraces of Huon Peninsula, Papua New Guinea

Many landslides disrupt the coral terraces at northeast Huon Peninsula, Papua New Guinea. Each landslide is younger than the youngest terrace which it intersects and is older than the oldest coral reef or shoreline that overlies it. The ages of the raised coral reefs and terraces were established by previous studies using radiocarbon and uranium-series dating. The times of occurrence of 26 late Quaternary landslides are reported here; 7 are based on new radiocarbon dates from in situ corals or molluscs associated with landslide deposits, and the remainder are based on terrace ages that were established previously. The landslides include slumps, block slides and block flows which mostly involve failure of coral limestones of the terraces, and debris flows which originate from large landslides that cut through the coral limestones into underlying fan-delta and tuffaceous sedimentary rocks. The proportion of terrace area affected by Late Quaternary landslides ranges from < 1% to > 50% per km2 and depends on average gradient of the landsurface, tectonic uplift rate, and the thickness and geometry of the raised reefs and terraces. Clusters of landslides, which occurred at about 800–1250 and 6300–7800 yr BP, may have been triggered by large earthquakes which also caused metre-scale coseismic uplift. However, we did not identify landslides that could have been associated with every large coseimic uplift that has been documented in this region.

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Late Quaternary reorientation of stress field and extension direction in the southern Gulf of Suez, Egypt: Evidence from uplifted coral terraces, mesoscopic fault arrays, and borehole breakouts

Uplifted Pleistocene coral terraces and modern earthquakes show that several large normal faults are presently active in the southern Gulf of Suez rift basin. The footwall of one of these faults is exposed at Gebel el Zeit, where terraces at elevations of +10–18 and +42 m have been radiometrically dated as 125 ka and 426 ka, respectively. After correcting for eustatic sea‐level changes, this results in net tectonic uplift rates of about 0.1 m/kyr. Published interpretations and our own observations indicate that the average extension direction during the Miocene to Pliocene synrift history was 055°. Analysis of borehole breakouts and published earthquake fault plane solutions, however, suggests that the present‐day stress field in the southern Gulf has a 010°–020° Shmin orientation. Detailed structural observations show that a change in extension direction occurred in the late Pleistocene, with rotation of the stress field beginning prior to formation of the 125 ka terraces but after formation of older Pleistocene terraces whose ages are less tightly constrained. Using a horizontal slip direction of 015° and our observed net footwall uplift rate, we calculate a separation velocity between Sinai and Africa of 0.8–1.2 m/kyr. The proposed Pleistocene change in extension direction in the Gulf of Suez corresponds closely with the post‐500 ka change in extension direction documented in the Kenyan rift system and a similar change in extension direction recorded in the central Red Sea. These regional similarities in tectonic history suggest that the underlying causes of these events may be a plate‐scale phenomenon affecting the entire Afro‐Arabian rift system, rather than local changes in the Quaternary stress field.

Reconciliaion of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep sea oxygen isotope records

A major discrepancy between the Late Quaternary sea level changes derived from raised coral reef terraces at the Huon Peninsula in Papua New Guinea and from oxygen isotopes in deep sea cores is resolved. The two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka (ka = 1000 yr before present), but between 70 and 30 ka the isotopic sea levels are 20–40 m lower than the Huon Peninsula sea levels derived in earlier studies. New, high precision U-series age measurements and revised stratigraphic data for Huon Peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic δ 18O data. Using the sea level and deep sea isotopic data, oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from Greenland ice cores. The record of ice volume changes through the last glacial cycle now appears to be reasonably complete.