Evaluation of simple geochemical indicators of aeolian sand provenance: Late Quaternary dune fields of North America revisited

Dune fields of Quaternary age occupy large areas of the world\u27s arid and semiarid regions. Despite this, there has been surprisingly little work done on understanding dune sediment provenance, in part because many techniques are time-consuming, prone to operator error, experimental, highly specialized, expensive, or require sophisticated instrumentation. Provenance of dune sand using K/Rb and K/Ba values in K-feldspar in aeolian sands of the arid and semiarid regions of North America is tested here. Results indicate that K/Rb and K/Ba can distinguish different river sands that are sediment sources for dunes and dune fields themselves have distinctive K/Rb and K/Ba compositions. Over the Basin and Range and Great Plains regions of North America, the hypothesized sediment sources of dune fields are reviewed and assessed using K/Rb and K/Ba values in dune sands and in hypothesized source sediments. In some cases, the origins of dunes assessed in this manner are consistent with previous studies and in others, dune fields are found to have a more complex origin than previously thought. Use of K/Rb and K/ Ba for provenance studies is a robust method that is inexpensive, rapid, and highly reproducible. It exploits one of the most common minerals found in dune sand, K-feldspar. The method avoids the problem of using simple concentrations of key elements that may be subject to interpretative bias due to changes in mineralogical maturity of Quaternary dune fields that occur over time

The geologic records of dust in the Quaternary

Study of geologic records of dust composition, sources and deposition rates is important for understanding the role of dust in the overall planetary radiation balance, fertilization of organisms in the world’s oceans, nutrient additions to the terrestrial biosphere and soils, and for paleoclimatic reconstructions. Both glacial and non-glacial processes produce fine-grained particles that can be transported by the wind. Geologic records of dust flux occur in a number of depositional archives for sediments: (1) loess deposits; (2) lake sediments; (3) soils; (4) deep-ocean basins; and (5) ice sheets and smaller glaciers. These archives have several characteristics that make them highly suitable for understanding the dynamics of dust entrainment, transport, and deposition. First, they are often distributed over wide geographic areas, which permits reconstruction of spatial variation of dust flux. Second, a number of dating methods can be applied to sediment archives, which allows identification of specific periods of greater or lesser dust flux. Third, aeolian sediment particle size and composition can be determined so that dust source areas can be ascertained and dust transport pathways can be reconstructed. Over much of the Earth’s surface, dust deposition rates were greater during the last glacial period than during the present interglacial period. A dustier Earth during glacial periods is likely due to increased source areas, greater aridity, less vegetation, lower soil moisture, possibly stronger winds, a decreased intensity of the hydrologic cycle, and greater production of dust-sized particles from expanded ice sheets and glaciers

Dating Marine Terraces with Relative-Age and Correlated-Age Methods

Coastal landforms, and particularly emergent marine terraces, a re amongt he most importantg eomorphicfe aturesi n studieso f Quaternarys eal evel fluctuationsa nd neotectonics. A general model, first articulated by Alexander (1953) and borne out by detailedr ecent studieso n many coastlinesi,s that emergent flights of erosional terraces and coral reefs (Fig. 1) are the resulto f glacioeustaticallyc ontrolledf luctuations of global sea level superimposed on steady uplift. Similiarity of U-series ages of coral from both constructional reefsi n the tropicsa nd erosionalt erracesi n midlatitudesh as provided a rigorous test of this model (Mesolella and others, 1969; Bloom and others, 1974; Dodge and others, 1983; Muhs and others, 1994). Both erosional shore platforms and constructional reefs form when relative sea level is stable, i.e., during an unchanging sea level on a tectonically stable coast, or when the rate of sea level fall or rise matches the rate of tectonics ubsidenceo r uplift, respectivelyT. herefore,o n tectonically rising coasts, emergent marine terraces record interglacial or interstadial sea level high stands; terraces that formed during glacial-period sea-level low stands are usually submerged. On subsiding coasts submerged terraces may record both interglacial high stands and glacial-period low stands (Ludwig and others, 1991). Interglacial and interstadial periods correspond to odd-numbered stages and glacial periodsc orrespondto even-numbereds tagesi n the deep-sea foraminiferal oxygen isotope record. Although U-series dating has demonstrated that erosional marine terraces form during the same interglacial or interstadialh igh sea standsa s constructionarl eef terraces, there are often significantd ifferencesi n the completenesso f terrace flights on erosionala nd constructionacl oasts.L owlatitude coasts characterized by overlapping constructional coral reefs usually have fairly complete terrace sequences. On mid-latitude,h igh-energyc oastsh, owever,s eacliffr etreat rates are often high. For example, in California, most modem sea cliff retreat rates range from about 0.01-0.5 m/yr, but some are higher than 1.0 m/yr (Muhs, 1987). Thus, the potentiale xistsf or removalo f emergentt erraces,r esultingi n flights with variable numbers of terraces along a given coastline. Local correlation from one terrace flight to the next can be a problem, therefore, on the high-energy coastlines of New Zealand, Japan, Oregon, California, Mexico, Peru, and Chile. This paper reviews some of the methods by which firstorder approximationso f marine terrace ages can be determined, when material suitable for numerical dating is rare or absent. The methods described fall into the categories of relative-age a nd correlated-age te chniquesa, s described by Colman and others (1987). I consider first those methods which are useful for local correlation, and then review techniquesw hich havet he goal of correlatingt erracesw ith global sea level stands. The methods reviewed here are those that haveb eent estedo n a variety of coastlinesa, nd can therefore be evaluated for reliability

The last interglacial-glacial transition in North America: Evidence from uranium-series dating of coastal deposits

Considerable uncertainty exists as to whether the last interglacial was relatively short (~10 ka) or long (-20-60 ka), although most investigators generally agree that the last interglacial correlates with all or part of deep-sea oxygen-isotope stage 5. A compilation of reliable U-series ages of marine terrace corals from deposits that have been correlated with isotope stage 5 indicates that there were three relatively high sea-level stands at ca 125-120 ka, ca. 105 ka, and ca. 85-80 ka, and these ages agree with the times of high sea level predicted by the Milankovitch orbital-forcing theory. At a number of localities, however, there are apparently reliable coral ages of ca. 145-135 ka and ca. 70 ka, and the Milankovitch theory would not predict high sea levels at these times. These ages are at present unexplained and require further study. The issue of whether the last interglacial was short or long can be addressed by examining the evidence for how high sea level was during the stands at ca. 125 ka, ca. 105 ka, and ca. 80 ka, because sea level is inversely proportional to global ice volume. In technically stable areas such as Bermuda, the Bahamas, the Yucatan peninsula, and Florida, there is clear evidence that sea level at ca. 125 ka was +3 to +10 m higher than present. During the ca. 105 ka and ca. 80 ka high sea-level stands, there is conflicting evidence for how high sea levels were. Studies of uplifted terraces on Barbados and Haiti and most studies of terraces on New Guinea indicate sea levels considerably lower than present. Studies of the terraces and deposits on the east and west coasts of North America, Bermuda, and the Bahamas, however, indicate sea levels close to, or only slightly below, the present at these times. Thus, data from Barbados, Haiti, and New Guinea indicate a short last interglacial centering ca. 125 ka, but data from the other localities indicate that sea level was high during much of the period from 125 to 80 ka, and that there were two minor ice advances in that period. If it is accepted that the last interglacial period was relatively long and ended sometime after ca. 80 ka, then coastal deposits on the California Channel Islands record a shift in the nature of sedimentation at the interglacial/glacial transition. Marine terraces that are ca. 80 ka are overlain by two eolianite units separated by paleosols. U-series ages of the terrace corals and carbonate rhizoliths indicate that eolian sedimentation occurred between ca. 80 and 49 ka, and again between ca. 27 and 14 ka. Eolian sands were apparently derived from carbonate-rich shelf sediments during glaciallylowered sea levels, because there are not sufficient beach sources for calcareous sediment at present. The times of eolian sedimentation agree well with times of glaciation predicted by the Milankovitch model of climatic change

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

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 70m 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 often can be accomplished using amino acid ratios of fossil mollusks, compared to similar ratios in mollusks that also host dated corals. Uranium-series (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 geochronological 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 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 (SSTs) 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 at _ 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 review and 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 et al. (2021b; https://doi.org/10.5281/zenodo.5903285)

Loess Deposits, Origins and Properties

Loess is an eolian (windblown) sediment that is an important archive of Quaternary climate changes. It may provide one of the most complete terrestrial records of interglacial–glacial cycles. Loess is unusual as a record of Quaternary climate change because it is one of the few sediments that is deposited directly from the atmosphere. Thus, it is a geologic deposit that contains a record of atmospheric circulation and can be used to reconstruct synoptic-scale paleoclimatology. Loess is also unusual in that it can be dated directly using ‘trapped electron’ or luminescence methods that require only the sediment itself. Commonly, loess deposits are not homogenous sediments, but most contain buried soils, or paleosols. It is the combination of both unaltered loess deposits and intercalated paleosols that gives this sedimentary record much of its richness as a Quaternary paleoclimate record

Dune Fields: Mid-Latitudes

Large dune fields, or sand seas, are landscapes often thought to be found only in deserts beneath the great, subtropical high-pressure zones, where subsiding air suppresses rainfall. Dune fields are also quite common in mid-latitude regions, to the north and south of subtropical deserts (Fig. 1). Two major characteristics distinguish many mid-latitude dune fields from the sand seas of lower latitudes. One difference is that many of those in mid-latitudes are in semiarid, rather than arid climates, and therefore are not presently active. In this article, ‘active’ refers to eolian sand bodies that are not covered with vegetation, and where particles are currently being transported by the wind. Evidence of active sand transport often takes the form of well-expressed sand ripples on a dune’s surface. Where sand is vegetated and particles are not being transported by the wind, a sand body is ‘stable.’ A second characteristic of mid-latitude dune fields is that many are situated near mountain ranges or at least areas of relatively high relief. Glaciation in high mountains reduces local bedrock to sand-sized particles, and additional reduction of rock to sand sizes takes place through colluvial and fluvial processes quickly in terrains of steep relief. Through these processes, new sediment becomes available to feed growing dune fields much more rapidly than in areas of low relief, which characterize lower-latitude regions. Because of their occurrence in semiarid climates, mid-latitude dune fields are particularly sensitive indicators of shifts in the regional moisture balance. Sand dunes move only where there is wind, sandsized sediment, and a lack of vegetation cover. A shift to drier conditions may result in loss of vegetation cover and activation of sand by wind. A shift back to wetter conditions may stabilize dunes because of enhanced vegetation cover. The geologic record of this alternation of dry and moist climates tends to be preserved in many mid-latitude dune fields as eolian sand–paleosol sequences. In areas downslope of high sediment production, such as mountains, fresh sediment may accumulate in a dune field during periods of eolian activity, bury the pre-existing landscape, and preserve former surface soils as buried soils (or paleosols). In arid, lowlatitude environments of low relief, previously stabilized eolian sand may be continually reworked without addition of much new sand, and formerly stable surfaces, which would be marked by paleosols in semiarid climates, may not be preserved. Throughout this article, we correlate eolian dunebuilding events, where they can be dated or where the age can be inferred, to the marine oxygen-isotope stratigraphic framework of Martinson et al. (1987). Where the abbreviation ‘MIS’ occurs, this refers to ‘marine isotope stage,’ using the numbering system and approximate ages in Martinson et al. (1987)

Cliff-height and slope-angle relationships in a chronosequence of Quaternary marine terraces, San Clemente Island, California

Zusammenfassung. Eine Abfolge quartarer Strandterrassen auf ~an Clemente Island, Kalifornien, liefert einen Rahmen fur die quantitative Analyse der Anderungen an vom Meer verlassenen Kustenkliffen als Funktion der Zeit. Es wurde eine Abschatzung der Anwendbarkeit von BUCKNAM & ANDERSON (1979) log-lin~arer Beziehung zwischen Wandhohe und Hangwinkel durchgefuhrt, indem Brandungskliffhohe und maximale Hangwinkel verwendet wurden. Die Ergebnisse zeigen eine regelhafte Zunahme des Hangwinkels mit dem Logarithmus der Kliffhohe, und Kliffe einer bestimmten Hohe zeigen m,it der Zeit eine Abnahmedes maximalen Hangwinkels. 1m ganzen waren die Relationen schwacher als fur FluBterrassen und Bruchstufen in unverfestigten Materialen, aber die Methode kann wahrscheinlich verwendet werden, urn fruhe, mittlere und junge quartare Bruchstufen und Kustenkliffe in verfestigtem Material erfolgreich zu unterscheiden. Summary. A flight of Quaternary marine terraces on San Clemente Island, California, provides a framework for quantitative analysis of abandoned sea cliff modification as a function of time. An assessment was made of the applicability of BUCKNAM & ANDERSON\u27S (1979) log-linear relationship between scarp height and slope angle using sea cliff height and maximum slope angle. Results indicate a regular increase in slope angle with the logarithm of the cliff height and cliffs of a given height show a decline in maximum slope angle with time. Overall, the relationships are weaker than for stream terraces and fault scarps in unconsolidated materials, but the method can probably be used successfully to distinguish early, middle and late Quaternary fault scarps or sea cliffs in consolidated materials. Resume. Une serie de terrasses marines quaternaires sur l\u27ile de San Clemente (Californie) fournit un cadre pour l\u27analyse quantitative de l\u27evolution de falaises marines mortes. Une hypothese a ete avancee concernant l\u27application de la relation log-normale de BUCKNAM & ANDERSON (1979) entre la hauteur de l\u27escarpement et l\u27angle de la pente appliquee ici a la hauteur de la falaise marine et l\u27angle maximum de la pente. Les resultats indiquent un accroissement regulier de la pente avec Ie logarithme de la hauteur de la falaise et les falaises d\u27une hauteur determinee montrent un abaissement de l\u27angle de pente maximum en fonction du temps. Partout, les relations sont moins bonnes que pour les terrasses de rivieres et des escarpements de failles dans des materiaux meubles. Toutefois, la methode peut probablerment etre utilisee avec succes pour donner un age quaternaire recent moyen ou ancien aux escarpements de failles ou aux falaises marines dans des materiaux c;onsolides. Text in English: The rate of alteration of slopes, particularly those derived from fault scarps, has received increasing attention in recent years because of the need for accurate assessment\u27 of potential fault hazards (WALLACE 1977; BUCKNAM & ANDERSON, 1979; NASH 1980a, 1980b, 1984; MACHETTE 1982; COLMAN 1983; COLMAN & WATSON 1983; HANKS et al. 1984; MAYER 1984; STERR 1985). Often there is a need for age determination of a fault scarp, but little or no material available for radiometric dates. Hence, many investigators have utilized morphometric parameters in order to establish relative and in some cases absolute ages. BUCKNAM & ANDERSON (1979) were perhaps the first to quantify changes in fault scarp slope angles through time. They examined the relationship between scarp height and slope angle in Quaternary deposits in the Great Basin of western Utah and quantified earlier observations of WALLACE (1977). Their results indicated that for small scarps less than 10 m high, slope angle increases with the logarithm of scarp height and decreases through time for a scarp of a given height. This relationship has been confirmed for fault scarps in other locations in the southwestern U. S. A. (MACHETTE 1982; MAYER 1984; HANKS et al. 1984) and has been, extended to other landforms such as stream terrace scarps (COLMAN 1983) and lake cliffs (NASH 1980b). Several studies have gone beyond the relative dating method proposed by BUCKNAM & ANDERSON (1979) and models for determination of absolute age have been generated (NASH 1980b, 1984; COLMAN & WATSON 1983; HANKS et al. 1984; HANKS & WALLACE 1985; STERR 1985). MAYER (1984) recently discussed the complicating effects of measurement error, lithology, particle size, and composite scarps

Newgeochemical evidence for the origin of North America\u27s largest dune field, the Nebraska Sand Hills, central Great Plains, USA

The Nebraska SandHills region is the largest dune field inNorthAmerica and has diverse aeolian landforms. It has been active during both the late Pleistocene and late Holocene. Despite decades of study, the source of sediment for this large sand sea is still controversial. Here we report new trace element compositions of aeolian sand that are compared to four hypothesized sediment sources, Tertiary rocks of the Arikaree Group and Ogallala Group, unconsolidated sands of Pliocene age, and Platte River systemsands. All four potential sources have amineralogy that is similar to the Nebraska Sand Hills. K/Rb, K/Ba, Sc-Th-La, Eu/Eu*, LaN/YbN, As/Sb, and Fe/Sc values show, however, that Pliocene sediments and sands from the Platte River system are not likely sources. The Arikaree Group could be a minor contributor, but sands from the Ogallala Group appear to have the best compositional fit to the Nebraska Sand Hills. Although past studies have proposed the Ogallala Group as an important sand source, the hypothesis has been questioned, because the unit iswell cemented by calcrete in its upper part. However, examination of the landscape upwind of the Nebraska Sand Hills shows that the Ogallala Group, where it occurs at the land surface, is highly dissected in much of this region, which makes sand-sized particles available for aeolian entrainment whenever drought conditions diminish a protective vegetation cover

Bermuda solution pipe soils: A geochemical evaluation of eolian parent materials

Solution pipes found in the Quaternary eolian and marine carbonates of Bermuda are filled with reddish to reddish-brown soil material. The bulk of the soil is composed of clay and silt-sized quartz and aluminosilicate clay minerals. The carbonates are of high purity and, therefore, are not likely to have been the parent material. Previous workers have hypothesized that Saharan dust may have been the soil parent material. The fine-grained component of loess from the Mississippi River Valley of North America also could have contributed. Paleoclimate models indicate that both North Africa and North America could have been important source areas during both glacial and interglacial periods. Immobile element concentrations in Bermuda soil samples collected from the interiors of solution pipes were determined for the purpose of geochemical fingerprinting and comparisons with the hypothesized parent materials. Immobile element ratios using Al, Ti, Zr,Y, and Th suggest that neither Saharan dust nor lower Mississippi River Valley loess were the sole contributors to Bermuda soils. Eolian dust from at least one other source area such as the Great Plains may have contributed parent material to the soils of Bermuda