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Deanna Laurel - One of the best experts on this subject based on the ideXlab platform.
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coastal tectonics on the eastern margin of the pacific rim late quaternary sea level history and uplift rates channel islands national park california usa
Quaternary Science Reviews, 2014Co-Authors: Daniel R Muhs, Kathleen R Simmons, Randall R Schumann, Lindsey T Groves, Stephen B Devogel, Scott A Minor, Deanna LaurelAbstract:Abstract The Pacific Rim is a region where tectonic processes play a significant role in coastal landscape evolution. Coastal California, on the eastern margin of the Pacific Rim, is very active tectonically and geomorphic expressions of this include uplifted marine terraces. There have been, however, conflicting estimates of the rate of late Quaternary uplift of marine terraces in coastal California, particularly for the northern Channel Islands. In the present study, the terraces on San Miguel Island and Santa Rosa Island were mapped and new age estimates were generated using Uranium-Series Dating of fossil corals and amino acid geochronology of fossil mollusks. Results indicate that the 2nd terrace on both islands is ∼120 ka and the 1st terrace on Santa Rosa Island is ∼80 ka. These ages correspond to two global high-sea stands of the Last Interglacial complex, marine isotope stages (MIS) 5.5 and 5.1, respectively. The age estimates indicate that San Miguel Island and Santa Rosa Island have been tectonically uplifted at rates of 0.12–0.20 m/ka in the late Quaternary, similar to uplift rates inferred from previous studies on neighboring Santa Cruz Island. The newly estimated uplift rates for the northern Channel Islands are, however, an order of magnitude lower than a recent study that generated uplift rates from an offshore terrace Dating to the Last Glacial period. The differences between the estimated uplift rates in the present study and the offshore study are explained by the magnitude of glacial isostatic adjustment (GIA) effects that were not known at the time of the earlier study. Set in the larger context of northeastern Pacific Rim tectonics, Channel Islands uplift rates are higher than those coastal localities on the margin of the East Pacific Rise spreading center, but slightly lower than those of most localities adjacent to the Cascadia subduction zone. The uplift rates reported here for the northern Channel Islands are similar to those reported for most other localities where strike-slip tectonics are dominant, but lower than localities where restraining bends (such as the Big Bend of the San Andreas Fault) result in crustal shortening.
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sea level history during the last interglacial complex on san nicolas island california implications for glacial isostatic adjustment processes paleozoogeography and tectonics
Quaternary Science Reviews, 2012Co-Authors: Daniel R Muhs, Kathleen R Simmons, Randall R Schumann, Lindsey T Groves, Jerry X Mitrovica, Deanna LaurelAbstract:Abstract San Nicolas Island, California has one of the best records of fossiliferous Quaternary marine terraces in North America, with at least fourteen terraces rising to an elevation of ∼270 m above present-day sea level. In our studies of the lowest terraces, we identified platforms at 38–36 m (terrace 2a), 33–28 m (terrace 2b), and 13–8 m (terrace 1). Uranium-Series Dating of solitary corals from these terraces yields three clusters of ages: ∼120 ka on terrace 2a (marine isotope stage [MIS] 5.5), ∼120 and ∼100 ka on terrace 2b (MIS 5.5 and 5.3), and ∼80 ka (MIS 5.1) on terrace 1. We conclude that corals on terrace 2b that date to ∼120 ka were reworked from a formerly broader terrace 2a during the ∼100 ka sea stand. Fossil faunas differ on the three terraces. Isolated fragments of terrace 2a have a fauna similar to that of modern waters surrounding San Nicolas Island. A mix of extralimital southern and extralimital northern species is found on terrace 2b, and extralimital northern species are on terrace 1. On terrace 2b, with its mixed faunas, extralimital southern species, indicating warmer than present waters, are interpreted to be from the ∼120 ka high sea stand, reworked from terrace 2a. The extralimital northern species on terrace 2b, indicating cooler than present waters, are interpreted to be from the ∼100 ka sea stand. The abundant extralimital northern species on terrace 1 indicate cooler than present waters at ∼80 ka. Using the highest elevations of the ∼120 ka platform of terrace 2a, and assuming a paleo-sea level of +6 m based on previous studies, San Nicolas Island has experienced late Quaternary uplift rates of ∼0.25–0.27 m/ka. These uplift rates, along with shoreline angle elevations and ages of terrace 2b (∼100 ka) and terrace 1 (∼80 ka) yield relative (local) paleo-sea level elevations of +2 to +6 m for the ∼100 ka sea stand and −11 to −12 m for the ∼80 ka sea stand. These estimates are significantly higher than those reported for the ∼100 ka and ∼80 ka sea stands on New Guinea and Barbados. Numerical models of the glacial isostatic adjustment (GIA) process presented here demonstrate that these differences in the high stands are expected, given the variable geographic distances between the sites and the former Laurentide and Cordilleran ice sheets. Moreover, the numerical results show that the absolute and differential elevations of the observed high stands provide a potentially important constraint on ice volumes during this time interval and on Earth structure.
Daniel R Muhs - One of the best experts on this subject based on the ideXlab platform.
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coastal tectonics on the eastern margin of the pacific rim late quaternary sea level history and uplift rates channel islands national park california usa
Quaternary Science Reviews, 2014Co-Authors: Daniel R Muhs, Kathleen R Simmons, Randall R Schumann, Lindsey T Groves, Stephen B Devogel, Scott A Minor, Deanna LaurelAbstract:Abstract The Pacific Rim is a region where tectonic processes play a significant role in coastal landscape evolution. Coastal California, on the eastern margin of the Pacific Rim, is very active tectonically and geomorphic expressions of this include uplifted marine terraces. There have been, however, conflicting estimates of the rate of late Quaternary uplift of marine terraces in coastal California, particularly for the northern Channel Islands. In the present study, the terraces on San Miguel Island and Santa Rosa Island were mapped and new age estimates were generated using Uranium-Series Dating of fossil corals and amino acid geochronology of fossil mollusks. Results indicate that the 2nd terrace on both islands is ∼120 ka and the 1st terrace on Santa Rosa Island is ∼80 ka. These ages correspond to two global high-sea stands of the Last Interglacial complex, marine isotope stages (MIS) 5.5 and 5.1, respectively. The age estimates indicate that San Miguel Island and Santa Rosa Island have been tectonically uplifted at rates of 0.12–0.20 m/ka in the late Quaternary, similar to uplift rates inferred from previous studies on neighboring Santa Cruz Island. The newly estimated uplift rates for the northern Channel Islands are, however, an order of magnitude lower than a recent study that generated uplift rates from an offshore terrace Dating to the Last Glacial period. The differences between the estimated uplift rates in the present study and the offshore study are explained by the magnitude of glacial isostatic adjustment (GIA) effects that were not known at the time of the earlier study. Set in the larger context of northeastern Pacific Rim tectonics, Channel Islands uplift rates are higher than those coastal localities on the margin of the East Pacific Rise spreading center, but slightly lower than those of most localities adjacent to the Cascadia subduction zone. The uplift rates reported here for the northern Channel Islands are similar to those reported for most other localities where strike-slip tectonics are dominant, but lower than localities where restraining bends (such as the Big Bend of the San Andreas Fault) result in crustal shortening.
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sea level history during the last interglacial complex on san nicolas island california implications for glacial isostatic adjustment processes paleozoogeography and tectonics
Quaternary Science Reviews, 2012Co-Authors: Daniel R Muhs, Kathleen R Simmons, Randall R Schumann, Lindsey T Groves, Jerry X Mitrovica, Deanna LaurelAbstract:Abstract San Nicolas Island, California has one of the best records of fossiliferous Quaternary marine terraces in North America, with at least fourteen terraces rising to an elevation of ∼270 m above present-day sea level. In our studies of the lowest terraces, we identified platforms at 38–36 m (terrace 2a), 33–28 m (terrace 2b), and 13–8 m (terrace 1). Uranium-Series Dating of solitary corals from these terraces yields three clusters of ages: ∼120 ka on terrace 2a (marine isotope stage [MIS] 5.5), ∼120 and ∼100 ka on terrace 2b (MIS 5.5 and 5.3), and ∼80 ka (MIS 5.1) on terrace 1. We conclude that corals on terrace 2b that date to ∼120 ka were reworked from a formerly broader terrace 2a during the ∼100 ka sea stand. Fossil faunas differ on the three terraces. Isolated fragments of terrace 2a have a fauna similar to that of modern waters surrounding San Nicolas Island. A mix of extralimital southern and extralimital northern species is found on terrace 2b, and extralimital northern species are on terrace 1. On terrace 2b, with its mixed faunas, extralimital southern species, indicating warmer than present waters, are interpreted to be from the ∼120 ka high sea stand, reworked from terrace 2a. The extralimital northern species on terrace 2b, indicating cooler than present waters, are interpreted to be from the ∼100 ka sea stand. The abundant extralimital northern species on terrace 1 indicate cooler than present waters at ∼80 ka. Using the highest elevations of the ∼120 ka platform of terrace 2a, and assuming a paleo-sea level of +6 m based on previous studies, San Nicolas Island has experienced late Quaternary uplift rates of ∼0.25–0.27 m/ka. These uplift rates, along with shoreline angle elevations and ages of terrace 2b (∼100 ka) and terrace 1 (∼80 ka) yield relative (local) paleo-sea level elevations of +2 to +6 m for the ∼100 ka sea stand and −11 to −12 m for the ∼80 ka sea stand. These estimates are significantly higher than those reported for the ∼100 ka and ∼80 ka sea stands on New Guinea and Barbados. Numerical models of the glacial isostatic adjustment (GIA) process presented here demonstrate that these differences in the high stands are expected, given the variable geographic distances between the sites and the former Laurentide and Cordilleran ice sheets. Moreover, the numerical results show that the absolute and differential elevations of the observed high stands provide a potentially important constraint on ice volumes during this time interval and on Earth structure.
Morten B. Andersen - One of the best experts on this subject based on the ideXlab platform.
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the timing of sea level high stands during marine isotope stages 7 5 and 9 constraints from the Uranium Series Dating of fossil corals from henderson island
Geochimica et Cosmochimica Acta, 2010Co-Authors: Emma-kate Potter, Claudine H. Stirling, Morten B. Andersen, Alex N. Halliday, Steve G Blake, Malcolm T Mcculloch, Bridget Ayling, Michael OlearyAbstract:Direct Dating of fossil coral reefs using the U-Series chronometer provides an important independent test of the Milankovitch orbital forcing theory of climate change. However, well-dated fossil corals pre-Dating the last interglacial period (>130 thousand years ago; ka) are scarce due to, (1) a lack of sampling localities, (2) insufficient analytical precision in U-Series Dating methods, and (3) diagenesis which acts to violate the assumption of closed-system U-Series isotopic decay in fossil corals. Here we present 50 new high-precision U-Series age determinations for fossil corals from Henderson Island, an emergent coral atoll in the central South Pacific. U-Series age determinations associated with the Marine Isotope Stage (MIS) 9 interglacial and MIS 7.5 interstadial periods are reported. The fossil corals show relatively little open-system U-Series behaviour in comparison to other localities with fossil coral reefs formed prior to the last glacial cycle, however, open-system U-Series behaviour is still evident in most of the dated corals. In particular, percent-level shifts in the [230Th/238U]act composition are observed, leading to conventional U-Series ages that are significantly younger or older than the true sample age. This open-system U-Series behaviour is not accounted for by any of the open-system U-Series models, indicating that new models should be derived. The new U-Series ages reported here support and extend earlier findings reported in Stirling et al. (2001), providing evidence of prolific coral reef development on Henderson Island at not, vert, similar320 ka, most likely correlated with MIS 9.3, and subsequent reef development at not, vert, similar307 ka during MIS 9.1, while relative sea-level was potentially not, vert, similar20 m lower than during MIS 9.3. The U-Series ages for additional well-preserved fossil corals are suggestive of minor reef development on Henderson Island during MIS 7.5 (245–230 ka) at 240.3 ± 0.8 and 234.7 ± 1.3 ka. All U-Series observations are consistent with the Milankovitch theory of climate change, in terms of the timing of onset and termination of the dated interglacial and interstadial periods. The best preserved samples also suggest that the oceanic 234U/238U during MIS 9 and MIS 7.5 was within five permil of the modern open ocean composition.
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Uranium Series Dating of fossil coral reefs extending the sea level record beyond the last glacial cycle
Earth and Planetary Science Letters, 2009Co-Authors: Claudine H. Stirling, Morten B. AndersenAbstract:Abstract Absolutely dated records of past sea-level change are extremely important for understanding the advance and retreat of the large ice sheets. When combined with other complementary climate archives and climate models, such records offer the potential to gain an improved understanding of Earth's natural climate cycles, providing a firmer basis for assessing the role of anthropogenic effects, such as greenhouse gas emissions, in modifying climate. The U-Series Dating of fossil coral reefs has been widely utilized to provide absolutely dated records of past sea-level change and numerous observations now exist for the past 130,000 years spanning the last glacial cycle. Despite this, controversies still exist regarding the exact timing and character of sea-level events within this time interval, and extending the sea-level history further back in time on the basis of robust and independent age constraints for older fossil reefs remains very elusive. This is primarily due to a progressive loss in the resolution of the U-Series chronometer as one goes further back in time, coupled to a lack of well-preserved, dateable coral in older fossil reefs. To overcome these limitations, the primary challenges are three-fold. First, new analytical protocols are required to improve the resolution of the U-Series chronometer. Enhanced analytical precision must be coupled to accuracy through continued refinement of the U-Series decay constant determinations and via the implementation of rigorous inter-laboratory calibration exercises. Second, efforts should continue to be focussed on gaining an improved understanding of the mechanisms controlling open-system exchange of the U-Series isotopes in fossil reef systems. This will allow the number of ‘reliable’ U-Series observations to be extended. Third, alternative dateable archives of past sea-level change must continue to be emphasized to further complement the coral reef database. These limitations are discussed in the context of current developments that further advance the application of U-Series chronology to older fossil reef systems formed prior to the last glacial cycle.
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High precision Faraday collector MC-ICPMS thorium isotope ratio determination
International Journal of Mass Spectrometry, 2005Co-Authors: Emma-kate Potter, Claudine H. Stirling, Morten B. Andersen, Alex N. HallidayAbstract:Abstract Uranium-Series Dating of carbonate materials requires precise determination of the spike sample thorium isotope ratio, 230 Th/ 229 Th. This ratio is commonly measured using ion counting techniques, however the precision of analyses using ion counting devices suffers from beam intensity limitations, drift in multiplier gain and non-linearities in electron multiplier response. Here, we describe the application of multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) to determine thorium isotope ratios at hitherto unattained precision. For the first time, thorium isotope analyses were performed using only Faraday collectors coupled to 10 11 Ω feedback resistors in the amplifier system. Spiked thorium solutions were concentrated to produce 230 Th and 229 Th signal intensities of around 50 mV and 100 mV, respectively (across a 10 11 Ω resistor) and are run at high intensity for a short period of time (∼1 min). These analyses yield a 230 Th/ 229 Th external reproducibility of better than 0.3‰ for ∼25–30 pg of consumed 230 Th. This is a factor of two better than the best published thermal ionisation mass spectrometry (TIMS) and MC-ICPMS techniques for similar sample sizes, and represents up to an order of magnitude improvement over many other established protocols. Combined with new techniques for high precision Faraday measurement of Uranium isotopic composition [1] , this permits improvements in the uncertainty of U-Series ages to better than 0.1 thousand years (ka) at 100 ka and 1 ka at 300 ka. It should also be possible to resolve events to ∼14 ka at 600 ka. Using these techniques, the U-Series Dating limit can be extended from 500–600 ka to 800 ka enabling a more detailed study of the frequency of late Pleistocene climate events.
Shangde Luo - One of the best experts on this subject based on the ideXlab platform.
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u Series chronology of lacustrine deposits in death valley california
Quaternary Research, 1998Co-Authors: Shangde Luo, Tim K Lowenstein, Ronald J SpencerAbstract:Uranium-Series Dating on a 186-m core (DV93-1) drilled from Badwater Basin in Death Valley, California, and on calcareous tufas from nearby strandlines shows that Lake Manly, the lake that periodically flooded Death Valley during the late Pleistocene, experienced large fluctuations in depth and chemistry over the last 200,000 yr. Death Valley has been occupied by a long-standing deep lake, perennial shallow saline lakes, and a desiccated salt pan similar to the modern valley floor. The average sedimentation rate of about 1 mm/yr for core DV93-1 was punctuated by episodes of more-rapid accumulation of halite. Arid conditions similar to the modern conditions prevailed during the entire Holocene and between 120,000 and 60,000 yr B.P. From 35,000 yr B.P. to the beginning of the Holocene, a perennial saline lake existed, over 70 m at its deepest. A much deeper and longer lasting perennial Lake Manly existed from about 185,000 to 128,000 yr B.P., with water depths reaching about 175 m, if not 330 m. This lake had two significant “dry” excursions of 102–103yr duration about 166,000 and 146,000 yr B.P., and it began to shrink to the point of halite precipitation between 128,000 and 120,000 yr B.P. The two perennial lake periods correspond to marine oxygen isotopic stages (OIS) 2 and 6. Based on the shoreline tufa ages, we do not rule out the possible existence ∼200,000 yr ago of yet a third perennial lake comparable in size to the OIS 6 lake. The234U/238U data suggest that U in tufa owes its origin mainly to Ca-rich springs fed by groundwater that emanated along lake shorelines in southern Death Valley, and that an increase of this spring-water input relative to the river-water input apparently occurred during OIS 6.
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a 100 ka record of water tables and paleoclimates from salt cores death valley california
Palaeogeography Palaeoclimatology Palaeoecology, 1996Co-Authors: Tim K Lowenstein, Christopher B Brown, Shangde LuoAbstract:Abstract Sedimentary and petrographic features of evaporites and associated sediments from a 185 m deep core taken in Death Valley, CA, together with Uranium-Series Dating have been used to reconstruct the history of water table fluctuations and climate changes in Death Valley for the past 100 ka. Death Valley has been arid during the Holocene (0–10 ka), with predominantly mudflat and saline pan subenvironments. A perennial lake, up to 90 m deep, existed in Death Valley from 10 to 35 ka. Saline pan and mudflat subenvironments dominated Death Valley from 35 to 100 ka. The chronology of changing subenvironments and water table fluctuations in Death Valley generally correlates with other climate records in the western US (Owens Lake and Searles Lake, CA, Browns Room cave calcite, NV), the marine oxygen isotope record, and the Vostok ice core record. Core intervals through saline pan sediments are composed of interbedded halite, chaotic muddy halite, and mud. The halite contains abundant vertical dissolution pipes, cemented with clear halite. These sediments record repeated flooding by dilute waters, dissolution of subaerially exposed surface salt crusts, deposition of mud from suspension, precipitation of halite during the saline lake phase, and cementation by diagenetic halite. Mudflat sediments consist of clayey silt, with sand patches and mud cracks, which document long periods of desiccation and the formation of efflorescent salt crusts from the evaporation of groundwater brines. Saline pan and mudflat deposits formed during periods when Death Valley was relatively arid, similar to the modern climate. Lacustrine deposits consist of mudhalite cycles, accumulated during the early lake stage, bedded thenardite (Na 2 SO 4 ) and mud above, and a cap of massive halite formed during the latest lake stage, all of which record fluctuating salinities and lake levels in a perennial system. Such deposits document a relatively wet climate with a high ratio of water inflow to evaporation. Ostracodes in mud layers represent the least saline, deepest lake phases. Halite layers are made of fine grained cumulates and clear, vertically-oriented crystals precipitated during shallower, perennial lake stages. Of significance is the nearly complete absence of syndepositional dissolution of saline minerals in the lacustrine interval, indicating that accumulated salts were permanently protected from dissolution by saline lake waters. Such evidence strongly suggests that lakes existed continually, without desiccating, for 25 ka between 10 and 35 ka B.P.
Randall R Schumann - One of the best experts on this subject based on the ideXlab platform.
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coastal tectonics on the eastern margin of the pacific rim late quaternary sea level history and uplift rates channel islands national park california usa
Quaternary Science Reviews, 2014Co-Authors: Daniel R Muhs, Kathleen R Simmons, Randall R Schumann, Lindsey T Groves, Stephen B Devogel, Scott A Minor, Deanna LaurelAbstract:Abstract The Pacific Rim is a region where tectonic processes play a significant role in coastal landscape evolution. Coastal California, on the eastern margin of the Pacific Rim, is very active tectonically and geomorphic expressions of this include uplifted marine terraces. There have been, however, conflicting estimates of the rate of late Quaternary uplift of marine terraces in coastal California, particularly for the northern Channel Islands. In the present study, the terraces on San Miguel Island and Santa Rosa Island were mapped and new age estimates were generated using Uranium-Series Dating of fossil corals and amino acid geochronology of fossil mollusks. Results indicate that the 2nd terrace on both islands is ∼120 ka and the 1st terrace on Santa Rosa Island is ∼80 ka. These ages correspond to two global high-sea stands of the Last Interglacial complex, marine isotope stages (MIS) 5.5 and 5.1, respectively. The age estimates indicate that San Miguel Island and Santa Rosa Island have been tectonically uplifted at rates of 0.12–0.20 m/ka in the late Quaternary, similar to uplift rates inferred from previous studies on neighboring Santa Cruz Island. The newly estimated uplift rates for the northern Channel Islands are, however, an order of magnitude lower than a recent study that generated uplift rates from an offshore terrace Dating to the Last Glacial period. The differences between the estimated uplift rates in the present study and the offshore study are explained by the magnitude of glacial isostatic adjustment (GIA) effects that were not known at the time of the earlier study. Set in the larger context of northeastern Pacific Rim tectonics, Channel Islands uplift rates are higher than those coastal localities on the margin of the East Pacific Rise spreading center, but slightly lower than those of most localities adjacent to the Cascadia subduction zone. The uplift rates reported here for the northern Channel Islands are similar to those reported for most other localities where strike-slip tectonics are dominant, but lower than localities where restraining bends (such as the Big Bend of the San Andreas Fault) result in crustal shortening.
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sea level history during the last interglacial complex on san nicolas island california implications for glacial isostatic adjustment processes paleozoogeography and tectonics
Quaternary Science Reviews, 2012Co-Authors: Daniel R Muhs, Kathleen R Simmons, Randall R Schumann, Lindsey T Groves, Jerry X Mitrovica, Deanna LaurelAbstract:Abstract San Nicolas Island, California has one of the best records of fossiliferous Quaternary marine terraces in North America, with at least fourteen terraces rising to an elevation of ∼270 m above present-day sea level. In our studies of the lowest terraces, we identified platforms at 38–36 m (terrace 2a), 33–28 m (terrace 2b), and 13–8 m (terrace 1). Uranium-Series Dating of solitary corals from these terraces yields three clusters of ages: ∼120 ka on terrace 2a (marine isotope stage [MIS] 5.5), ∼120 and ∼100 ka on terrace 2b (MIS 5.5 and 5.3), and ∼80 ka (MIS 5.1) on terrace 1. We conclude that corals on terrace 2b that date to ∼120 ka were reworked from a formerly broader terrace 2a during the ∼100 ka sea stand. Fossil faunas differ on the three terraces. Isolated fragments of terrace 2a have a fauna similar to that of modern waters surrounding San Nicolas Island. A mix of extralimital southern and extralimital northern species is found on terrace 2b, and extralimital northern species are on terrace 1. On terrace 2b, with its mixed faunas, extralimital southern species, indicating warmer than present waters, are interpreted to be from the ∼120 ka high sea stand, reworked from terrace 2a. The extralimital northern species on terrace 2b, indicating cooler than present waters, are interpreted to be from the ∼100 ka sea stand. The abundant extralimital northern species on terrace 1 indicate cooler than present waters at ∼80 ka. Using the highest elevations of the ∼120 ka platform of terrace 2a, and assuming a paleo-sea level of +6 m based on previous studies, San Nicolas Island has experienced late Quaternary uplift rates of ∼0.25–0.27 m/ka. These uplift rates, along with shoreline angle elevations and ages of terrace 2b (∼100 ka) and terrace 1 (∼80 ka) yield relative (local) paleo-sea level elevations of +2 to +6 m for the ∼100 ka sea stand and −11 to −12 m for the ∼80 ka sea stand. These estimates are significantly higher than those reported for the ∼100 ka and ∼80 ka sea stands on New Guinea and Barbados. Numerical models of the glacial isostatic adjustment (GIA) process presented here demonstrate that these differences in the high stands are expected, given the variable geographic distances between the sites and the former Laurentide and Cordilleran ice sheets. Moreover, the numerical results show that the absolute and differential elevations of the observed high stands provide a potentially important constraint on ice volumes during this time interval and on Earth structure.
