Preprints
https://doi.org/10.5194/essd-2021-345
https://doi.org/10.5194/essd-2021-345

  22 Oct 2021

22 Oct 2021

Review status: this preprint is currently under review for the journal ESSD.

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

Daniel R. Muhs Daniel R. Muhs
  • U.S. Geological Survey, MS 980, Box 25046, Federal Center, Denver, Colorado 80225 USA

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].

Daniel R. Muhs

Status: open (until 17 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2021-345', Jessica Creveling, 01 Nov 2021 reply
  • RC2: 'Comment on essd-2021-345', John Wehmiller, 11 Nov 2021 reply
    • CC2: 'Reply on RC2', Alessio Rovere, 25 Nov 2021 reply
      • RC3: 'Reply on CC2', John Wehmiller, 29 Nov 2021 reply
  • CC1: 'Comment on essd-2021-345', Barbara Mauz, 22 Nov 2021 reply
  • RC4: 'Comment on essd-2021-345', Hayley C. Cawthra, 30 Nov 2021 reply

Daniel R. Muhs

Data sets

MIS 5e relative sea-level index points along the Pacific coast of North America Muhs, Daniel https://doi.org/10.5281/zenodo.5557355

Daniel R. Muhs

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Short summary
The last interglacial period, also known as marine isotope substage (MIS) 5e, was the last time in recent geologic history when sea level was substantially higher than present. It is an important time period to understand, because climate models forecast a higher global sea level in the not-too-distant future. Geologic records of this high-sea stand (marine terraces) along the Pacific Coast of North America are reviewed here, with identification of knowledge gaps where more work is needed.