High plains

@article{elias1935tertiary,
    author = "Elias, M. K.",
    title = "Tertiary grasses and other prairie vegetation from High Plains of North America",
    year = "1935",
    journal = "American Journal of Science",
    url = "https://doi.org/10.2475/ajs.s5-29.169.24",
    doi = "10.2475/ajs.s5-29.169.24",
    number = "169",
    openalex = "W2318659963",
    pages = "24-33",
    volume = "s5-29"
}

@book{crossref194241,
    title = "41: Tertiary Prairie Grasses and Other Herbs from the High Plains",
    year = "1942",
    booktitle = "Geological Society of America Special Papers",
    url = "https://doi.org/10.1130/spe41",
    doi = "10.1130/spe41",
    openalex = "W2331843971"
}

@incollection{elias1942tertiary,
    author = "ELIAS, MAXIM K.",
    title = "Tertiary Prairie Grasses and Other Herbs from the High Plains",
    year = "1942",
    booktitle = "Geological Society of America Special Papers",
    url = "https://doi.org/10.1130/spe41-p7",
    doi = "10.1130/spe41-p7",
    openalex = "W4302085224",
    pages = "7-171"
}

@misc{elias1942tertiary1,
    author = "Elias, M. K",
    title = "Tertiary prairie grasses and other herbs from the High Plains, 41 of Geological Society of America, Special Paper",
    year = "1942",
    howpublished = "p. 1-176",
    note = "talkorigins\_source = {true}; raw\_reference = {Elias, M. K., 1942, Tertiary prairie grasses and other herbs from the High Plains, 41 of Geological Society of America, Special Paper: p. 1-176.}"
}

(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.

@article{stebbins1943tertiary,
    author = "{Stebbins, G Ledyard, (George Ledyard), Jr.}",
    title = "Tertiary Prairie Grasses and Other Herbs from the High Plains. Geological Society of America, Special Papers, number 41 by Maxim K. Elias",
    year = "1943",
    publisher = "California Botanical Society",
    abstract = "(Uploaded by Plazi from the Biodiversity Heritage Library) No abstract provided.",
    url = "https://zenodo.org/doi/10.5281/zenodo.16302033",
    doi = "10.5281/zenodo.16302033"
}

@article{weatherwax1944tertiary,
    author = "Weatherwax, Paul and Elias, Maxim K.",
    title = "Tertiary Prairie Grasses and Other Herbs from the High Plains.",
    year = "1944",
    journal = "American Midland Naturalist",
    url = "https://doi.org/10.2307/2421085",
    doi = "10.2307/2421085",
    number = "2",
    openalex = "W2580009101",
    pages = "509",
    volume = "31"
}

@article{ewan1946tertiary,
    author = "Ewan, Joseph",
    title = "Tertiary Prairie Grasses and Other Herbs From the High Plains. Maxim K. Elias",
    year = "1946",
    journal = "The Quarterly Review of Biology",
    url = "https://doi.org/10.1086/395457",
    doi = "10.1086/395457",
    number = "4",
    openalex = "W2517507066",
    pages = "373-374",
    volume = "21"
}

Amphitropical distributions of vascular plants in the Western Hemisphere are divided into three groups: bipola or high-latitude, with about 30 species; temperate, with about 130 species; and desert, with a substancial number. Close relationships of this sort can be explained either by divergence from a common tropical ancestor or by origin on one side of the tropics and subsequent migration to the other. The latter is true for the great majority of groups discussed. These may have crossed the tropics in a single jump or by direct migration. The plant communities involved are relatively recent in origin. The amphitropical disjuncts are drawn from relatively few families and mostly are plants that occur in open habitats such as seacoast or seasonally moist places where establishment would be relatively easy. Woody plants and even herbs of closed communities are scarcely represented. Animals by and large do not have analogous amphitropical distributions as they would be expected to if the plants migrated by a land bridge or mountain chain that took them directly through the tropics. Nearly all of the plants are self-compatible; the arrival of a single seed in a suitable habitat is sufficient for the start of a new disjunct population. Animals, being predominatly bisexual, are not as likely to establish colonies in new areas to which they are rarely dispersed as are autogamous plants. Many of the disjunct patterns correspond with the migration routes of birds, which must occasionally carry seeds between one hemisphere and the other. The floras of extratropical North and South America have been distinct since at least the middle Cretaceous and are still very different at present; the few common or closely similar species are discordant elements superimposed on this pattern. Despite this, in at least 200 species and species-groups of plants, the relationships between North and South American populations are very close. Many of these are annual herbs of rapidly evolving groups in which chromosomal differences often accumulate quickly. Nevertheless, crosses between North and South American plants in several groups have demonstrated a relatively high degree of chromosome pairing and some fertility. The bipolar species mostly come from the Northern Hemisphere; their most likely time of dispersal seems to have ben the Pleistocene. About 85 per cent of the temperate species may likewise have come from the north, possibly in the late Pliocene and Pleistocene. A majority of the desert species may have come from the south, possibly as recently as post-Pleistocene time in some cases. Sporadic long-distance transtropical dispersal seems to be the best hypothesis to account for all these facts.

@article{doi101086403797,
    author = "Raven, Peter H.",
    title = "Amphitropical Relationships in the Floras of North and South America",
    year = "1963",
    journal = "The Quarterly Review of Biology",
    abstract = "Amphitropical distributions of vascular plants in the Western Hemisphere are divided into three groups: bipola or high-latitude, with about 30 species; temperate, with about 130 species; and desert, with a substancial number. Close relationships of this sort can be explained either by divergence from a common tropical ancestor or by origin on one side of the tropics and subsequent migration to the other. The latter is true for the great majority of groups discussed. These may have crossed the tropics in a single jump or by direct migration. The plant communities involved are relatively recent in origin. The amphitropical disjuncts are drawn from relatively few families and mostly are plants that occur in open habitats such as seacoast or seasonally moist places where establishment would be relatively easy. Woody plants and even herbs of closed communities are scarcely represented. Animals by and large do not have analogous amphitropical distributions as they would be expected to if the plants migrated by a land bridge or mountain chain that took them directly through the tropics. Nearly all of the plants are self-compatible; the arrival of a single seed in a suitable habitat is sufficient for the start of a new disjunct population. Animals, being predominatly bisexual, are not as likely to establish colonies in new areas to which they are rarely dispersed as are autogamous plants. Many of the disjunct patterns correspond with the migration routes of birds, which must occasionally carry seeds between one hemisphere and the other. The floras of extratropical North and South America have been distinct since at least the middle Cretaceous and are still very different at present; the few common or closely similar species are discordant elements superimposed on this pattern. Despite this, in at least 200 species and species-groups of plants, the relationships between North and South American populations are very close. Many of these are annual herbs of rapidly evolving groups in which chromosomal differences often accumulate quickly. Nevertheless, crosses between North and South American plants in several groups have demonstrated a relatively high degree of chromosome pairing and some fertility. The bipolar species mostly come from the Northern Hemisphere; their most likely time of dispersal seems to have ben the Pleistocene. About 85 per cent of the temperate species may likewise have come from the north, possibly in the late Pliocene and Pleistocene. A majority of the desert species may have come from the south, possibly as recently as post-Pleistocene time in some cases. Sporadic long-distance transtropical dispersal seems to be the best hypothesis to account for all these facts.",
    url = "https://doi.org/10.1086/403797",
    doi = "10.1086/403797",
    openalex = "W2075394457"
}

The appearance of fossilized silica bodies derived from the leaf epidermis E grasses visis mammalian fossils having high-crowned teeth was nearly simultaneous in m middle Eoc strata of Patagonia, where these fossils are associated with dry land sedimen vat indicate the America, the earliest clearly identified grass fossils are stipaid dir of lower Miocene ES 'while the oldest mammals having high-crowned teeth are derape es of Miocene age.The abundant stipoid fruits known from the Miocene and Pliocene Epochs in the d United States indicate that the earliest Miocene species were quite different from ES counterparts, but that early Pliocene species have modern counterparts in the pampas of South America.During the Pleistocene, stipoid grasses ceased to be dominant elements of North American grasslands, being replaced by grasses belonging to the tribes Chlorideae and Andropogoneae.This change was associated with the appearance of a drier, more continental climate and with the appearance of bison and sheep on the North American plains.The evolutionary significance of these coordinated changes is discussed

@article{doi1023072398811,
    author = "Stebbins, G. Ledyard",
    title = "Coevolution of Grasses and Herbivores",
    year = "1981",
    journal = "Annals of the Missouri Botanical Garden",
    abstract = "The appearance of fossilized silica bodies derived from the leaf epidermis E grasses visis mammalian fossils having high-crowned teeth was nearly simultaneous in m middle Eoc strata of Patagonia, where these fossils are associated with dry land sedimen vat indicate the America, the earliest clearly identified grass fossils are stipaid dir of lower Miocene ES 'while the oldest mammals having high-crowned teeth are derape es of Miocene age.The abundant stipoid fruits known from the Miocene and Pliocene Epochs in the d United States indicate that the earliest Miocene species were quite different from ES counterparts, but that early Pliocene species have modern counterparts in the pampas of South America.During the Pleistocene, stipoid grasses ceased to be dominant elements of North American grasslands, being replaced by grasses belonging to the tribes Chlorideae and Andropogoneae.This change was associated with the appearance of a drier, more continental climate and with the appearance of bison and sheep on the North American plains.The evolutionary significance of these coordinated changes is discussed",
    url = "https://doi.org/10.2307/2398811",
    doi = "10.2307/2398811",
    openalex = "W2055319580",
    references = "crossref194241, doi101002j153721971941tb07983x, doi101007978146133069126, doi101071bt9730201, doi101086405916, doi101126science19542841325, doi1023072395021, doi1023072395199, openalexw2609991144, openalexw641305787"
}

The temperate deciduous forest of North America is more diverse than the deciduous forest of western Europe. This difference has traditionally been explained by greater survival in North America of deciduous species during the Quaternary. More recent investigations have shown, however, that late-Tertiary forests of Europe had already become dominated by conifers, with deciduous angiosperms a minor component. During the Quaternary, coniferous species and genera were lost from the European flora, leaving a few species and genera of angiosperms as the dominant trees. Cold, dry, continental climate during the glaciations caused the extinction of conifers; deciduous trees apparently survived these climatic conditions in pockets of favorable habitat in the eastern Mediterranean region. In eastern North America, in contrast, temperate deciduous forests are quite similar to the forests that were present in the late Tertiary. During the Quaternary, relatively few extinctions occurred, although deciduous angiosperms were displaced from the Appalachian mountains, surviving in small populations in the lower Mississippi valley or on the southern coastal plain. Coniferous forests dominated by spruce grew in the Great Plains, and forests dominated by pine grew on the southern part of the Atlantic coastal plain. At the opening of the Holocene, and presumably at the beginning of all the previous interglacials, tree distributions changed dramatically as temperate species rapidly extended their ranges northward. Range boundaries have continued to change throughout the Holocene, as expansions and contractions of range have occurred as the result of climatic change. Quaternary climatic history caused dramatic changes in the forests of both areas, indicating that modern species distributions can no longer be considered relicts of Tertiary distributions. Throughout the Quaternary, species ranges have changed in response to changes in regional climate; many forest communities are of recent origin, having received their present complements of tree species within the last 5,000 years. Forest communities in Eastern North America and in Western Europe as well have been invaded repeatedly during the Holocene by forest species expanding from refuges far to the south. Temperate deciduous forest grows over a wide area of eastern North America. The forest is rich in numbers of species, especially the mixed mesophytic forest communities of the southern Appalachians. These forests were traditionally compared with forests of the Tertiary Period (Reid, 1935; Braun, 1947, 1950; Campbell, 1982), when the so-called Arcto-Tertiary geoflora was supposed to have been widespread throughout the northern hemisphere (Chaney, 1944). Reid (1935) and Chaney (1944) believed that severe climate during the Quaternary Period eliminated the Arcto-Tertiary geoflora entirely from many regions, such as western North America, while in others, such as western Europe, extinctions eliminated all but a few species and genera. The modern deciduous forests were thus seen as remnants of an originally widespread, uniform vegetation. The geoflora concept has been challenged recently by Wolfe (1978, 1979) who argued that a uniform broad-leaved forest never existed. His analysis of the paleobotanical data shows that Tertiary floras were diverse, with evergreen gymnosperms such as Sequoia dominant in some regions, and evergreen angiosperms present elsewhere. He argued that a number of major climatic changes occurred during the Tertiary, especially during the Oligocene; these changes led to local changes in abundances of various components of the Tertiary flora. Thus changes of climate caused local adaptations rather than migrations of intact plant communities from one latitude to another as Chaney hypothesized (Wolfe, 1979). Before the end of the Tertiary Period, the forests of western United States were already dominated by conifers. A similar change had also occurred in Europe, where Pliocene floras contained many genera and species of conifers (Wolfe, 1979). Sequoia was the dominant tree in some regions (Traverse, 1982). Mixed coniferous-deciduous forest in Europe during the Pliocene is a new interpretation of forest history that stands in marked contrast to the traditional view. The traditional view held that deciduous forest persisted in Europe into the early Quaternary Period, when increasing se1 This work was supported by the National Science Foundation. 2 Department of Ecology and Behavioral Biology, University of Minnesota, Minneapolis, Minnesota 55455. ANN. MISSOURI BOT. GARD. 70:550-563. 1983. This content downloaded from 157.55.39.181 on Thu, 29 Sep 2016 05:51:40 UTC All use subject to http://about.jstor.org/terms 1983] DAVIS-QUATERNARY HISTORY 551 verity of climate caused extinctions of many angiosperm trees (Tralau, 1973; Campbell, 1982). In contrast, Wolfe emphasized that coniferous species and genera were the important losses from the European flora during the Quaternary. The Taxodiaceae, for example, once so important in the Black Sea region, were eliminated entirely (Traverse, 1982). The angiospermous genera that remain today represent differential survival of one component of what had been mixed coniferous-deciduous forest (Wolfe, 1979). Wolfe pointed out that Europe today has the type of climatic regime that elsewhere in the world supports mixed coniferous forest; the dominance of deciduous species in the region today is therefore anomalous. Eastern North America, in contrast, has a climatic regime typical of deciduous forest regions. Today it supports forests dominated by deciduous angiosperms, just as it did during the late Tertiary (Wolfe, 1979). The Quaternary pollen record adds a useful perspective to these differing views of the origin of the European deciduous forest and the relationship of deciduous forests in eastern North America and Europe. First, the Quaternary record shows that dramatic changes in the geographical ranges of forest species occurred during the Quaternary. We can no longer speak of Tertiary forest remaining in a region throughout the Quaternary, because many tree species were repeatedly displaced during the Quaternary from the geographical region where they now occur. For this reason, modern geographical ranges cannot be used to identify the locations of relict Tertiary forests. Second, the response of temperate forest trees to Quaternary climatic change was individualistic, supporting Wolfe's contention that Tertiaryfloras would not have migrated as units in response to climatic events. Third, the extinctions that occurred during the Quaternary, especially the differential extinctions of conifers and deciduous angiosperms document that the differential severity of Quaternary climate affectedforests differently in Europe and North America. These three factors contributed to the makeup of the modem temperate forest floras of North America and Europe. In considering how Quaternary climate changed Pliocene floras into modem floras, the two phases of Quaternary climate, glacial climates and interglacial climates, are important. The two phases appear to have had quite different effects. -Glacial phases, i.e., times when ice sheets were more extensive than at present, comprised about 90 percent of the time during the Quaternary period. During these long, cold intervals, temperate species survived in small populations that were susceptible to extinction. The severity of the climate, both in terms of average temperature, continentality, and drought; the extent of geographical displacement of plant species; the sizes of populations; and the community composition of forests in refuge areas; all had an effect on the probability of extinction for individual species. Interglacial intervals comprised a much smaller proportion (about 10 percent) of the Quaternary period. They were characterized by climates similar to those of today, which in Europe and eastern North America seem to bear a general resemblance to late-Tertiary climate. Each interglacial was short, lasting only 10,000 to 1 5,000 years, and began and ended with a sudden, major climatic change (Emiliani, 1972; Broecker & Van Donk, 1970). The interglacials, although favorable for survival and population expansion of temperate forest trees both in Europe and eastern North America, were times of vegetational instability. During interglacials the geographical distributions of temperate species shifted many hundreds of kilometers, and the composition of forest comunities changed rapidly. GEOLOGICAL EVIDENCE OF EVENTS DURING THE QUATERNARY PERIOD The exploration of the deep sea by geologists in the last twenty years has led to a new understanding of Quaternary events, revolutionizing our thinking about the time scale of glaciation. Many marine cores include sediment extending through the entire Quaternary Period. Previously, four major glaciations were recognized within the Quaternary. We now know that there were 18 or 20 glaciations during the last 2 million years, the time interval now assigned to the Quaternary. Each of these glacial cycles lasted about 100,000 years (Hays et al., 1969). Figure 1 shows oxygen-isotope paleoclimatic records for the last 800,000 years. The climatic events are well dated: the last interglacial (the earliest part of stage 5) started 125,000 years ago, lasted about 15,000 years, and ended with a sharp decline in temperature that initiated the last glaciation. Warm conditions returned, followed by a cold period, then a short warm interval. Seventy thousand years ago a long cold interval (stages 2-4) began, which culminated in the glacial maximum 18,000 to 20,000 years ago (Broecker & Van Donk, 1970). This content downloaded from 157.55.39.181 on Thu, 29 Sep 2016 05:51:40 UTC All use subject to http://about.jstor.org/terms 552 ANNALS OF THE MISSOURI BOTANICAL GARDEN [VOL. 70

@article{doi1023072992086,
    author = "Davis, Margaret B.",
    title = "Quaternary History of Deciduous Forests of Eastern North America and Europe",
    year = "1983",
    journal = "Annals of the Missouri Botanical Garden",
    abstract = "The temperate deciduous forest of North America is more diverse than the deciduous forest of western Europe. This difference has traditionally been explained by greater survival in North America of deciduous species during the Quaternary. More recent investigations have shown, however, that late-Tertiary forests of Europe had already become dominated by conifers, with deciduous angiosperms a minor component. During the Quaternary, coniferous species and genera were lost from the European flora, leaving a few species and genera of angiosperms as the dominant trees. Cold, dry, continental climate during the glaciations caused the extinction of conifers; deciduous trees apparently survived these climatic conditions in pockets of favorable habitat in the eastern Mediterranean region. In eastern North America, in contrast, temperate deciduous forests are quite similar to the forests that were present in the late Tertiary. During the Quaternary, relatively few extinctions occurred, although deciduous angiosperms were displaced from the Appalachian mountains, surviving in small populations in the lower Mississippi valley or on the southern coastal plain. Coniferous forests dominated by spruce grew in the Great Plains, and forests dominated by pine grew on the southern part of the Atlantic coastal plain. At the opening of the Holocene, and presumably at the beginning of all the previous interglacials, tree distributions changed dramatically as temperate species rapidly extended their ranges northward. Range boundaries have continued to change throughout the Holocene, as expansions and contractions of range have occurred as the result of climatic change. Quaternary climatic history caused dramatic changes in the forests of both areas, indicating that modern species distributions can no longer be considered relicts of Tertiary distributions. Throughout the Quaternary, species ranges have changed in response to changes in regional climate; many forest communities are of recent origin, having received their present complements of tree species within the last 5,000 years. Forest communities in Eastern North America and in Western Europe as well have been invaded repeatedly during the Holocene by forest species expanding from refuges far to the south. Temperate deciduous forest grows over a wide area of eastern North America. The forest is rich in numbers of species, especially the mixed mesophytic forest communities of the southern Appalachians. These forests were traditionally compared with forests of the Tertiary Period (Reid, 1935; Braun, 1947, 1950; Campbell, 1982), when the so-called Arcto-Tertiary geoflora was supposed to have been widespread throughout the northern hemisphere (Chaney, 1944). Reid (1935) and Chaney (1944) believed that severe climate during the Quaternary Period eliminated the Arcto-Tertiary geoflora entirely from many regions, such as western North America, while in others, such as western Europe, extinctions eliminated all but a few species and genera. The modern deciduous forests were thus seen as remnants of an originally widespread, uniform vegetation. The geoflora concept has been challenged recently by Wolfe (1978, 1979) who argued that a uniform broad-leaved forest never existed. His analysis of the paleobotanical data shows that Tertiary floras were diverse, with evergreen gymnosperms such as Sequoia dominant in some regions, and evergreen angiosperms present elsewhere. He argued that a number of major climatic changes occurred during the Tertiary, especially during the Oligocene; these changes led to local changes in abundances of various components of the Tertiary flora. Thus changes of climate caused local adaptations rather than migrations of intact plant communities from one latitude to another as Chaney hypothesized (Wolfe, 1979). Before the end of the Tertiary Period, the forests of western United States were already dominated by conifers. A similar change had also occurred in Europe, where Pliocene floras contained many genera and species of conifers (Wolfe, 1979). Sequoia was the dominant tree in some regions (Traverse, 1982). Mixed coniferous-deciduous forest in Europe during the Pliocene is a new interpretation of forest history that stands in marked contrast to the traditional view. The traditional view held that deciduous forest persisted in Europe into the early Quaternary Period, when increasing se1 This work was supported by the National Science Foundation. 2 Department of Ecology and Behavioral Biology, University of Minnesota, Minneapolis, Minnesota 55455. ANN. MISSOURI BOT. GARD. 70:550-563. 1983. This content downloaded from 157.55.39.181 on Thu, 29 Sep 2016 05:51:40 UTC All use subject to http://about.jstor.org/terms 1983] DAVIS-QUATERNARY HISTORY 551 verity of climate caused extinctions of many angiosperm trees (Tralau, 1973; Campbell, 1982). In contrast, Wolfe emphasized that coniferous species and genera were the important losses from the European flora during the Quaternary. The Taxodiaceae, for example, once so important in the Black Sea region, were eliminated entirely (Traverse, 1982). The angiospermous genera that remain today represent differential survival of one component of what had been mixed coniferous-deciduous forest (Wolfe, 1979). Wolfe pointed out that Europe today has the type of climatic regime that elsewhere in the world supports mixed coniferous forest; the dominance of deciduous species in the region today is therefore anomalous. Eastern North America, in contrast, has a climatic regime typical of deciduous forest regions. Today it supports forests dominated by deciduous angiosperms, just as it did during the late Tertiary (Wolfe, 1979). The Quaternary pollen record adds a useful perspective to these differing views of the origin of the European deciduous forest and the relationship of deciduous forests in eastern North America and Europe. First, the Quaternary record shows that dramatic changes in the geographical ranges of forest species occurred during the Quaternary. We can no longer speak of Tertiary forest remaining in a region throughout the Quaternary, because many tree species were repeatedly displaced during the Quaternary from the geographical region where they now occur. For this reason, modern geographical ranges cannot be used to identify the locations of relict Tertiary forests. Second, the response of temperate forest trees to Quaternary climatic change was individualistic, supporting Wolfe's contention that Tertiaryfloras would not have migrated as units in response to climatic events. Third, the extinctions that occurred during the Quaternary, especially the differential extinctions of conifers and deciduous angiosperms document that the differential severity of Quaternary climate affectedforests differently in Europe and North America. These three factors contributed to the makeup of the modem temperate forest floras of North America and Europe. In considering how Quaternary climate changed Pliocene floras into modem floras, the two phases of Quaternary climate, glacial climates and interglacial climates, are important. The two phases appear to have had quite different effects. -Glacial phases, i.e., times when ice sheets were more extensive than at present, comprised about 90 percent of the time during the Quaternary period. During these long, cold intervals, temperate species survived in small populations that were susceptible to extinction. The severity of the climate, both in terms of average temperature, continentality, and drought; the extent of geographical displacement of plant species; the sizes of populations; and the community composition of forests in refuge areas; all had an effect on the probability of extinction for individual species. Interglacial intervals comprised a much smaller proportion (about 10 percent) of the Quaternary period. They were characterized by climates similar to those of today, which in Europe and eastern North America seem to bear a general resemblance to late-Tertiary climate. Each interglacial was short, lasting only 10,000 to 1 5,000 years, and began and ended with a sudden, major climatic change (Emiliani, 1972; Broecker \& Van Donk, 1970). The interglacials, although favorable for survival and population expansion of temperate forest trees both in Europe and eastern North America, were times of vegetational instability. During interglacials the geographical distributions of temperate species shifted many hundreds of kilometers, and the composition of forest comunities changed rapidly. GEOLOGICAL EVIDENCE OF EVENTS DURING THE QUATERNARY PERIOD The exploration of the deep sea by geologists in the last twenty years has led to a new understanding of Quaternary events, revolutionizing our thinking about the time scale of glaciation. Many marine cores include sediment extending through the entire Quaternary Period. Previously, four major glaciations were recognized within the Quaternary. We now know that there were 18 or 20 glaciations during the last 2 million years, the time interval now assigned to the Quaternary. Each of these glacial cycles lasted about 100,000 years (Hays et al., 1969). Figure 1 shows oxygen-isotope paleoclimatic records for the last 800,000 years. The climatic events are well dated: the last interglacial (the earliest part of stage 5) started 125,000 years ago, lasted about 15,000 years, and ended with a sharp decline in temperature that initiated the last glaciation. Warm conditions returned, followed by a cold period, then a short warm interval. Seventy thousand years ago a long cold interval (stages 2-4) began, which culminated in the glacial maximum 18,000 to 20,000 years ago (Broecker \& Van Donk, 1970). This content downloaded from 157.55.39.181 on Thu, 29 Sep 2016 05:51:40 UTC All use subject to http://about.jstor.org/terms 552 ANNALS OF THE MISSOURI BOTANICAL GARDEN [VOL. 70",
    url = "https://doi.org/10.2307/2992086",
    doi = "10.2307/2992086",
    openalex = "W2007173242",
    references = "doi1010160033589482900552, doi1023071943265"
}

The High Plains aquifer, which underlies about 174,000 square miles in parts of eight States, is the principal source of water in one of the Nation's major agricultural areas. About 170,000 wells pump water from the aquifer to irrigate about 13 million acres in the High Plains. In 1978, the U.S. Geological Survey began a regional study of the High Plains aquifer to provide geohydrologic data and computer models of the aquifer needed to evaluate the effects of ground-water development. This report describes the geohydrology of the High Plains aquifer.

@article{doi103133pp1400b,
    author = "Gutentag, Edwin D. and Heimes, F.J. and Krothe, Noel C. and Luckey, Richard R. and Weeks, John B.",
    title = "Geohydrology of the High Plains Aquifer in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming",
    year = "1984",
    journal = "USGS professional paper",
    abstract = "The High Plains aquifer, which underlies about 174,000 square miles in parts of eight States, is the principal source of water in one of the Nation's major agricultural areas. About 170,000 wells pump water from the aquifer to irrigate about 13 million acres in the High Plains. In 1978, the U.S. Geological Survey began a regional study of the High Plains aquifer to provide geohydrologic data and computer models of the aquifer needed to evaluate the effects of ground-water development. This report describes the geohydrology of the High Plains aquifer.",
    url = "https://doi.org/10.3133/pp1400b",
    doi = "10.3133/pp1400b",
    openalex = "W1554641608",
    references = "doi102475ajss536213220"
}

@article{mclaughlin2002highvalue,
    author = "McLaughlin, S. B. and de la Torre Ugarte, D. G. and Garten, C. T. and Lynd, L. R. and Sanderson, M. A. and Tolbert, V. R. and Wolf, D. D.",
    title = "High-Value Renewable Energy from Prairie Grasses",
    year = "2002",
    journal = "Environmental Science \& Technology",
    url = "https://doi.org/10.1021/es010963d",
    doi = "10.1021/es010963d",
    number = "10",
    openalex = "W2077193390",
    pages = "2122-2129",
    volume = "36",
    references = "doi101007978146120223370, doi101007bf02941755, doi101021bp990109e, doi101046j13652486200000308x, doi10108000224561199412456893, doi101126science25149991318, doi101146annurevenergy211403, doi1023073894695, openalexw1605679211, openalexw2981311172"
}

Abstract Ogallala gravels are an important lithic material source for stone tool manufacture across the Great Plains. The lithology of eight gravel sample locations along the eastern escarpment of the Southern High Plains has been examined to quantify the composition and variability in Ogallala deposits. In addition, three Ogallala gravel quarry sites have been analyzed to determine how the lithology of Ogallala gravels influenced procurement and tool production strategies. Results indicate deposits of Ogallala gravels differ in their composition related to their position on the landscape, and the types of rocks vary by size and shape. Investigation of the quarry sites has revealed that the lithology of Ogallala gravels had an impact on testing and the initial stages of lithic reduction. Different rock types, however, may have more of an influence on later stages of tool manufacture at nearby campsites and other locations where Ogallala gravels are not as dense. © 2009 Wiley Periodicals, Inc.

@article{doi101002gea20297,
    author = "Hurst, Stance and Johnson, Eileen and McCoy, Zaneta Martinez and Cunningham, Doug",
    title = "The lithology of Ogallala gravels and hunter‐gatherer procurement strategies along the Southern High Plains eastern escarpment of Texas, USA",
    year = "2009",
    journal = "Geoarchaeology",
    abstract = "Abstract Ogallala gravels are an important lithic material source for stone tool manufacture across the Great Plains. The lithology of eight gravel sample locations along the eastern escarpment of the Southern High Plains has been examined to quantify the composition and variability in Ogallala deposits. In addition, three Ogallala gravel quarry sites have been analyzed to determine how the lithology of Ogallala gravels influenced procurement and tool production strategies. Results indicate deposits of Ogallala gravels differ in their composition related to their position on the landscape, and the types of rocks vary by size and shape. Investigation of the quarry sites has revealed that the lithology of Ogallala gravels had an impact on testing and the initial stages of lithic reduction. Different rock types, however, may have more of an influence on later stages of tool manufacture at nearby campsites and other locations where Ogallala gravels are not as dense. © 2009 Wiley Periodicals, Inc.",
    url = "https://doi.org/10.1002/gea.20297",
    doi = "10.1002/gea.20297",
    openalex = "W1976022447",
    references = "doi101002gea3340080105, doi1058799c175"
}

The subfamily Equinae in the Great Plains region of North America underwent a dramatic radiation and subsequent decline as climate changed from warm and humid in the middle Miocene to cooler and more arid conditions during the late Miocene. Here we use ecological niche modeling (ENM), specifically the GARP (Genetic Algorithm using Rule-set Prediction) modeling system, to reconstruct the geographic distribution of individual species during two time slices from the middle Miocene through early Pliocene. This method combines known species occurrence points with environmental parameters inferred from sedimentological variables to model each species' fundamental niche. The geographic range of each species is then predicted to occupy the geographic area within the study region wherever the set of environmental parameters that constrain the fundamental niche occurs. We analyze changes in the predicted distributions of individual species between time slices in relation to Miocene/Pliocene climate change. Specifically, we examine and compare distribution patterns for two time slices that span the period from the mid-Miocene (Barstovian) Climatic Optimum into the early Pliocene (Blancan) to determine whether habitat fragmentation led to speciation within the clade and whether species survival was related to geographic range size. Patchy geographic distributions were more common in the middle Miocene when speciation rates were high. During the late Miocene, when speciation rates were lower, continuous geographic ranges were more common. Equid species tracked their preferred habitat within the Great Plains region as well as regionally throughout North America. Species with larger predicted ranges preferentially survived the initial cooling event better than species with small geographic ranges. As climate continued to deteriorate in the late Miocene, however, range size became irrelevant to survival, and extinction rates increased for species of all range sizes. This is the first use of ENM and GARP in the continental fossil record. This powerful quantitative biogeographic method offers great promise for studies of other taxa and geologic intervals.

@article{doi10166600948373354587,
    author = "Maguire, Kaitlin C. and Stigall, Alycia L.",
    title = "Using ecological niche modeling for quantitative biogeographic analysis: a case study of Miocene and Pliocene Equinae in the Great Plains",
    year = "2009",
    journal = "Paleobiology",
    abstract = "The subfamily Equinae in the Great Plains region of North America underwent a dramatic radiation and subsequent decline as climate changed from warm and humid in the middle Miocene to cooler and more arid conditions during the late Miocene. Here we use ecological niche modeling (ENM), specifically the GARP (Genetic Algorithm using Rule-set Prediction) modeling system, to reconstruct the geographic distribution of individual species during two time slices from the middle Miocene through early Pliocene. This method combines known species occurrence points with environmental parameters inferred from sedimentological variables to model each species' fundamental niche. The geographic range of each species is then predicted to occupy the geographic area within the study region wherever the set of environmental parameters that constrain the fundamental niche occurs. We analyze changes in the predicted distributions of individual species between time slices in relation to Miocene/Pliocene climate change. Specifically, we examine and compare distribution patterns for two time slices that span the period from the mid-Miocene (Barstovian) Climatic Optimum into the early Pliocene (Blancan) to determine whether habitat fragmentation led to speciation within the clade and whether species survival was related to geographic range size. Patchy geographic distributions were more common in the middle Miocene when speciation rates were high. During the late Miocene, when speciation rates were lower, continuous geographic ranges were more common. Equid species tracked their preferred habitat within the Great Plains region as well as regionally throughout North America. Species with larger predicted ranges preferentially survived the initial cooling event better than species with small geographic ranges. As climate continued to deteriorate in the late Miocene, however, range size became irrelevant to survival, and extinction rates increased for species of all range sizes. This is the first use of ENM and GARP in the continental fossil record. This powerful quantitative biogeographic method offers great promise for studies of other taxa and geologic intervals.",
    url = "https://doi.org/10.1666/0094-8373-35.4.587",
    doi = "10.1666/0094-8373-35.4.587",
    openalex = "W2095774692",
    references = "doi101017s0022336000036362, doi1016660022336020050790185bgabhg20co2"
}

Abstract: Recent drilling in southwestern Kansas has produced intact cores to investigate the subsurface lithostratigraphy, sedimentary provenance, and chronostratigraphy of strata constituting the central High Plains Aquifer (HPA). In large portions of the HPA, groundwater withdrawals greatly exceed rates of recharge, leading to dramatic water-level declines and growing concerns for long-term sustainability. Two cores, HP1A (98 m) and CMC1 (50 m), are the first and deepest intact cores of the HPA ever collected. The cores show decameter-scale intercalations between suspended-load fluvial deposits composed of fine-grained sands with pedogenically modified overbank deposits, and very coarse-grained sands and gravels consistent with high-energy, bedload-dominated fluvial systems. Six intervals in HP1A and one from CMC1 were analyzed for detrital-zircon U-Pb ages by LA-ICP-MS. The HP1A samples show maximum depositional ages (MDAs) ranging from ∼ 27.5 to 36.4 Ma with depth. A MDA of ∼ 30 Ma was measured in the CMC1 core. These Paleogene zircons likely originated from explosive volcanism associated with the mid-Cenozoic ignimbrite flare-up (44–18 Ma), which blanketed much of western North America with high-volume air-fall tuffs. We propose that a large evaporite-dissolution basin in southwestern Kansas provided the accommodation space to preserve a record of Paleogene strata. The lack of younger middle–late Miocene zircons from cores in southwestern Kansas is striking given that such grains, likely derived from the Snake River Plain–Yellowstone hotspot volcanic provinces (16.1–0.6 Ma), are readily identified in the Ogallala Formation in north-central Kansas and Nebraska. The MDAs suggest Eocene to Oligocene age deposits that are time-equivalent to the Arikaree and White River groups in Nebraska are also present in Kansas.

@article{doi102110jsr201748,
    author = "Smith, J. J. and Ludvigson, Greg A. and Layzell, Anthony L. and Möller, Andreas and Harlow, R. Hunter and Turner, Elijah and Platt, Brian F. and Petronis, Michael",
    title = "Discovery of Paleogene Deposits of the Central High Plains Aquifer In the Western Great Plains, U.S.A.",
    year = "2017",
    journal = "Journal of Sedimentary Research",
    abstract = "Abstract: Recent drilling in southwestern Kansas has produced intact cores to investigate the subsurface lithostratigraphy, sedimentary provenance, and chronostratigraphy of strata constituting the central High Plains Aquifer (HPA). In large portions of the HPA, groundwater withdrawals greatly exceed rates of recharge, leading to dramatic water-level declines and growing concerns for long-term sustainability. Two cores, HP1A (98 m) and CMC1 (50 m), are the first and deepest intact cores of the HPA ever collected. The cores show decameter-scale intercalations between suspended-load fluvial deposits composed of fine-grained sands with pedogenically modified overbank deposits, and very coarse-grained sands and gravels consistent with high-energy, bedload-dominated fluvial systems. Six intervals in HP1A and one from CMC1 were analyzed for detrital-zircon U-Pb ages by LA-ICP-MS. The HP1A samples show maximum depositional ages (MDAs) ranging from ∼ 27.5 to 36.4 Ma with depth. A MDA of ∼ 30 Ma was measured in the CMC1 core. These Paleogene zircons likely originated from explosive volcanism associated with the mid-Cenozoic ignimbrite flare-up (44–18 Ma), which blanketed much of western North America with high-volume air-fall tuffs. We propose that a large evaporite-dissolution basin in southwestern Kansas provided the accommodation space to preserve a record of Paleogene strata. The lack of younger middle–late Miocene zircons from cores in southwestern Kansas is striking given that such grains, likely derived from the Snake River Plain–Yellowstone hotspot volcanic provinces (16.1–0.6 Ma), are readily identified in the Ogallala Formation in north-central Kansas and Nebraska. The MDAs suggest Eocene to Oligocene age deposits that are time-equivalent to the Arikaree and White River groups in Nebraska are also present in Kansas.",
    url = "https://doi.org/10.2110/jsr.2017.48",
    doi = "10.2110/jsr.2017.48",
    openalex = "W2749164495",
    references = "doi1016660022336020050790185bgabhg20co2"
}

exploration project in the Southern High Plains. We thank Mark Hannon, formerly U.S. Geological Survey (USGS), for scanning and georectifying maps and plates from the Kerr-McGee collection for our use. James Paces, research geologist with the USGS, contributed uranium-series isotope analyses of uranium minerals in outcrop samples

@article{doi103133sir20175134,
    author = "Gosen, Bradley S. Van and Hall, Susan M.",
    title = "The discovery and character of Pleistocene calcrete uranium deposits in the Southern High Plains of west Texas, United States",
    year = "2017",
    journal = "Scientific investigations report",
    abstract = "exploration project in the Southern High Plains. We thank Mark Hannon, formerly U.S. Geological Survey (USGS), for scanning and georectifying maps and plates from the Kerr-McGee collection for our use. James Paces, research geologist with the USGS, contributed uranium-series isotope analyses of uranium minerals in outcrop samples",
    url = "https://doi.org/10.3133/sir20175134",
    doi = "10.3133/sir20175134",
    openalex = "W2781419108",
    references = "doi1058799c175"
}