Age estimations based on amino acid racemization: Reply to comments of J.F. Wehmiller

Kvenvolden, Keith A.; Blunt, David J.; Clifton, H. Edward

doi:10.1016/0016-7037(81)90173-3

Cited by 13 publications

(5 citation statements)

References 14 publications

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“…A major conclusion of our report is that amino acid D/L data conform to local litho-or biostratigraphic control, but that there is a significant conflict between the absolute ages (and age differences) inferred from the amino acid data and some of the U-series dates. Furthermore, we conclude that these conflicts cannot be explained by either of the two kinetic models or racemization that have been proposed for these applications (Wehmiller, 1981;Kvenvolden et al, 1981). We suggest that some of the U-series dates might be misleading because of isotopic evidence of diagenetic contamination; alternatively, if the U-series dates are correct measures of the absolute ages of the shells analyzed here, then some basic assumptions inherent to the amino acid dating method must be questioned.…”

Section: Introductionmentioning

confidence: 79%

“…tive to the shape of the temperature history For leucine racemization, we have relied curve, because the duration of time spent at upon a number of field (Wehmiller, 1977, maximum and minimum temperatures is the 1981) and laboratory (Bada and Schroeder, most important factor kinetically. 1972; Mitterer, 1975;Smith et al, 1978; The approach outlined above is a relative Kvenvolden et al, 1981) studies that indi-one that normalizes EQT values (or effeccate an activation energy between 27 and 30 tive temperature reductions) to present day kcaYmole. A convenient expression for the mean-annual air temperatures, because rate constant (k) dependence on tempera-these are the records that are most freture (T, "K) for this approximate activation quently available.…”

Section: Temperature Histories Of Pleistocene Samplesmentioning

confidence: 99%

“…and "extendedlinear": the advantages and disadvantages of each model have been discussed by Wehmiller (1981;in press) and Kvenvolden et al (1981). Both actually are nonlinear models (in a logarithmic format), with separate linear components, but the break in slope between these components occurs at significantly different positions in the two models.…”

Section: Kinetic Model Optionsmentioning

confidence: 99%

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Amino Acid Age Estimates, Quaternary Atlantic Coastal Plain: Comparison with U-series Dates, Biostratigraphy, and Paleomagnetic Control

Wehmiller

Belknap

1982

Quat. res.

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Amino acid enantiomeric (D/L) ratios in the mollusk Mercenaria are compared with recently published biostratigraphic and/or U-series solitary coral data from 22 Quaternary localities on the central and southern Atlantic Coastal Plain. In all cases, local relative aminostratigraphic sequences are consistent with relative ages inferred from U-series or biostratigraphic data, although occasionally more depositional events are recognized by aminostratigraphic than biostratigraphic methods. However, if the U-series data are used as age calibrations for the D/L values, latitudinal trends of “isochronous” D/L values are highly variable and conflict with trends expected from the present temperature gradient, which is smooth and nearly linear between 45° and 25° N. Age estimation can be performed independently of the U-series data using a kinetic model that relies on the assumption that Pleistocene temperature gradients have also been smooth functions of latitude, although significantly steeper than the present temperature gradient. Within the uncertainties of this assumption, kinetic model age estimates for localities in the coastal plain fall into the following groups: 70,000–130,000 yr, 200–250,000 yr, 300,000–400,000 yr, 500,000–600,000 yr, 700,000–800,000 yr, and > 1,000,000 yr. Major conflicts between these model age estimates are observed for localities near Charleston, South Carolina and in central Virginia. These conflicts could indicate that the basic temperature assumptions of aminostratigraphy are incorrect, and that apparent local aminostratigraphic sequences (clusters of different D/L values) could be due to factors other than age difference. Alternatively, some of the U-series dates may be only minimum ages for these localities.

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Section: Introductionmentioning

confidence: 79%

Section: Temperature Histories Of Pleistocene Samplesmentioning

confidence: 99%

Section: Kinetic Model Optionsmentioning

confidence: 99%

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Amino Acid Age Estimates, Quaternary Atlantic Coastal Plain: Comparison with U-series Dates, Biostratigraphy, and Paleomagnetic Control

Wehmiller

Belknap

1982

Quat. res.

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“…These "amino-stratigraphic" correlations require some theoretical or empirical basis. The correlations shown in Figure 6 are based on: (1) the temperature dependence inherent to the kinetic model of leucine racemization as proposed by Wehmiller and Belknap (1982); (2) the observed similarity between the kinetics and the temperature dependence of leucine racemization in Mercenaria on the Atlantic coast, and in three closely related Pacific coast venerid bivalves (Wehmiller and Belknap, 1978;1982); and (3) the assumption that the gradient of Effective Quaternary Temperature (EQT; the gradient is graphically represented by the slope of the dashed line: Wehmiller and Emerson, 1980;Wehmiller et al, 1977;Wehmiller, 1981;Kvenvolden et al, 1981) between the Neuse River and Charleston has been similar to the present temperature gradient, which is about 2°C.…”

Section: Resultsmentioning

confidence: 99%

Comparison of Amino Acid Racemization Geochronometry with Lithostratigraphy, Biostratigraphy, Uranium-Series Coral Dating, and Magnetostratigraphy in the Atlantic Coastal Plain of the Southeastern United States

et al. 1982

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The results of an integrated study comprising litho- and biostratigraphic investigations, uranium-series coral dating, amino acid racemization in molluscs, and paleomagnetic measurements are compared to ascertain relative and absolute ages of Pleistocene deposits of the Atlantic Coastal Plain in North and South Carolina. Four depositional events are inferred for South Carolina and two for North Carolina by all methods. The data suggest that there are four Pleistocene units containing corals that have been dated at about 100,000 yr, 200,000 yr, 450,000 yr, and over 1,000,000 yr. Some conflicts exist between the different methods regarding the correlation of the younger of these depositional events between Charleston and Myrtle Beach. Lack of good uranium-series dates for the younger material at Myrtle Beach makes the correlation with the deposits at Charleston more difficult.

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“…Using nonlinear kinetic modeling, Wehmiller (1981) recalculated the ages of units I/II and IV at Willapa Bay to be 300 ± 50 ka and 70 ± 15 ka, respectively, suggesting correlation with MIS 9 and MIS 5a. Kvenvolden et al (1981) countered that nonlinear kinetics could be applied to amino acid values within the ranges of what their samples yielded, and also noted that Wehmiller's (1981) age estimates would require a much more complex geologic history than their age estimates. Kennedy et al (1982) reported new amino acid values in Saxidomus from unit IV and using a lateral correlation (aminozone) approach, considered that the unit IV deposits at Willapa Bay were of MIS 5a age, in agreement with Wehmiller (1981).…”

Section: Willapa Baymentioning

confidence: 99%

MIS 5e sea-level history along the Pacific Coast of North America

Muhs

2021

Preprint

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Abstract. The primary last interglacial, marine isotope substage (MIS) 5e records on the Pacific Coast of North America, from Washington (USA) to Baja California Sur (Mexico), are found in the deposits of erosional marine terraces. Warmer coasts along the southern Golfo de California host both erosional marine terraces and constructional coral reef terraces. Because the northern part of the region is tectonically active, MIS 5e terrace elevations vary considerably, from a few meters above sea level to as much as 70 m above sea level. The primary paleo-sea level indicator is the shoreline angle, the junction of the wave-cut platform with the former sea cliff, which forms very close to mean sea level. Most areas on the Pacific Coast of North America have experienced uplift since MIS 5e time, but the rate of uplift varies substantially as a function of tectonic setting. Chronology in most places is based on uranium-series ages of the solitary coral Balanophyllia elegans (erosional terraces) or the colonial corals Porites and Pocillopora (constructional reefs). In areas lacking corals, correlation to MIS 5e can sometimes be accomplished using amino acid ratios of fossil mollusks, compared to similar ratios in mollusks that also host dated corals. U-series analyses of corals that have experienced largely closed-system histories range from ~124 to ~118 ka, in good agreement with ages from MIS 5e reef terraces elsewhere in the world. There is no geomorphic, stratigraphic, or geochronology evidence for more than one high-sea stand during MIS 5e on the Pacific Coast of North America. However, in areas of low uplift rate, the outer parts of MIS 5e terraces apparently were re-occupied by the high-sea stand at ~100 ka (MIS 5c), evident from mixes of coral ages and mixes of molluscan faunas with differing thermal aspects. This sequence of events took place because glacial isostatic adjustment processes acting on North America resulted in regional high-sea stands at ~100 ka and ~80 ka that were higher than is the case in far-field regions, distant from large continental ice sheets. During MIS 5e time, sea surface temperatures (SST) off the Pacific Coast of North America were higher than is the case at present, evident from extralimital southern species of mollusks found in dated deposits. Apparently no wholesale shifts in faunal provinces took place, but in MIS 5e time, some species of bivalves and gastropods lived hundreds of kilometers north of their present northern limits, in good agreement with SST estimates derived from foraminiferal records and alkenone-based reconstructions in deep-sea cores. Because many areas of the Pacific Coast of North America have been active tectonically for much or all of the Quaternary, many earlier interglacial periods are recorded as uplifted, higher elevation terraces. In addition, from southern Oregon to northern Baja California, there are U-series-dated corals from marine terraces that formed ~80 ka, during MIS 5a. In contrast to MIS 5e, these terrace deposits host molluscan faunas that contain extralimital northern species, indicating cooler SST at the end of MIS 5. Here I present a standardized database of MIS 5e sea-level indicators along the Pacific Coast of North America and the corresponding dated samples. The database is available in Muhs (2021) [https://doi.org/10.5281/zenodo.5557355].

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Age estimations based on amino acid racemization: Reply to comments of J.F. Wehmiller

Cited by 13 publications

References 14 publications

Amino Acid Age Estimates, Quaternary Atlantic Coastal Plain: Comparison with U-series Dates, Biostratigraphy, and Paleomagnetic Control

Amino Acid Age Estimates, Quaternary Atlantic Coastal Plain: Comparison with U-series Dates, Biostratigraphy, and Paleomagnetic Control

Comparison of Amino Acid Racemization Geochronometry with Lithostratigraphy, Biostratigraphy, Uranium-Series Coral Dating, and Magnetostratigraphy in the Atlantic Coastal Plain of the Southeastern United States

MIS 5e sea-level history along the Pacific Coast of North America

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