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Geologic-Climatic Dating in the West
Abstract
Geologic-Climatic dating of archaeological finds in the arid and semiarid western United States is based on geology, on the relationship between moisture, vegetation, and geological processes, and on climatic history. The procedure of dating includes 4 main steps, namely, (1) study of beds and geological features, (2) climatic interpretation of beds and features, (3) assignment of the bed with the human record to a particular regional climatic age or phase, and (4) correlation of the regional relative chronology with a dated climatic history. The geological study of the site includes texture, structure, and appearance of the beds or terrace deposits, their modes and conditions of formation, their sequence, fossils, and artifacts, the soil zones, caliche incrustations, and erosions. The climatic interpretation of the beds and features is made in conformity with the delicate regional relationship between climatic conditions and changes and geological processes and deposits.
... The Early Agriculture Period (EAP) in the SW of USA and NW of Mexico begins just after the Altithermal period (7500 and 4500 yr BP), which represents the warmest and driest stage of the Holocene (Antevs, 1948(Antevs, , 1955. During the EAP agricultural societies cultivated corn and constructed canals for irrigation (Mabry et al., 2002;Diehl, 2009). ...
... The middle Holocene is characterized by a gradual shift towards drier conditions (less precipitation and higher temperatures), which result in changes in the ecosystem. This period is named as Altithermal (Antevs, 1955). The absence of archaeological artifacts in the Sonora desert suggests the inhospitable environmental conditions. ...
... The earliest evidences of agriculture in the studied site coincide with the end of the Altithermal period (around 4500 yr BP, Antevs, 1955). Our records show that by this time a long period of landsurface stability ended, marked by the formation of a well-developed palaeosol, the SRP or the Big Red mentioned by Sánchez (2010) and Sánchez et al. (2014). ...
... Asimismo, indican que para el Pleistoceno final y gran parte del Holoceno, prevaleció un gran periodo de estabilidad en el paisaje que permitió la formación de suelos bien desarrollados, bajo un clima semiárido, el cual puede ser relacionado con los inicios de la ocupación humana en la región. El cambio en las condiciones ambientales más drástico se nota en el sitio durante el Holoceno medio, hace unos cinco mil años, durante el periodo Altitermal (Antevs, 1955) u Óptimo climático del ...
... SRP did not record in its memory the climatic oscillations of the Bølling-Allerød/Younger Dryas. The only drastic climate change that left a signature in the soils occurred during Middle Holocene times and probably is equivalent to the Altithermal period defined by Antevs (1948Antevs ( , 1955) as a climate oscillation that lasted for several millennia characterized by very warm weather and very little precipitation that occurred between 7000 and 4500 BP. ...
... El cambio más relevante registrado en estos suelos ocurrió en el Holoceno medio, en donde se sucedieron procesos erosivos de gran escala que removieron el horizonte Ah del SRP y lo sepultaron bajo una gruesa capa de sedimentos limosos, sobre los cuales se desarrollaron posteriormente suelos policíclicos de desarrollo incipiente durante el Holoceno tardío. Este cambio coincide con los registros paleoclimáticos globales, que indican un periodo extremadamente cálido y seco conocido como Altitermal (Antevs, 1955) u Óptimo Climático del Holoceno (Darby et al., 2001;Uriarte, 2009). ...
Research of the last 15 years in NW Sonora, in places like El Arenoso, La Playa), Fin del Mundo, El Bajio and El Áigame have made evident that human groups began to inhabit this region since the late Pleistocene. The paleoenvironmental inferences for the surrounding regions indicate that towards the end of the Pleistocene dominated temperate climates, which constitute the habitat of the first settlers and the Pleistocene fauna in the region. However, the information derived from the study of the archaeological site La Playa paleosoils, indicates drier conditions, so a study was conducted at the regional level to establish regional paleoenvironmental conditions.
As part of the study, the physical and chemical properties of paleosols memory constituting the ground and allowed to infer their training environments were characterized. This allowed the paleosol identify and differentiate Pleistocene Holocene soils, which could establish the spatial variability of pedological cover late Pleistocene. That information was supplemented with the analysis of other paleoenvironmental indicators, such as carbon stable isotopes and faunal association.
Derived from research, it is characterized and chronologically located paleosols of late Pleistocene / early and middle Holocene (between 30 ka to 4.2 ka Cal BP) identified and described in previous work at archaeological sites El Arenoso (Terrazas, 2007; Terrazas and Benavente, 2013) and La Playa (Carpenter, et al., 2003 and 2005; Copeland et al, 2012), as well as pedosedimentary sequences of Magdalena de Kino and Rancho Los Alamitos, showing two pedogenic trends for this period.
In general, the south, center and north portions of the Sonora state are dominated by red soils (referred to as Big Red in the archaeological literature) whose characteristics are represented by the San Rafael Paleosol (SRP), described at the archaeological site La Playa, with C/2A/2Bw/2BCk/3Bgk/3BCgk/4C sequence, and dated by radiocarbon between 14.9 ka ka 14.23 Cal BP (in pedogenic carbonates) and 4.44 4.25 ka Cal BP (in charcoal). The properties of SRP (rubification, accumulation of clays, high magnetic susceptibility, illuvial carbonates at the base and redoximorphic features) are indicative of a more humid environment than today. Above of them, is located a polycyclic sequence of Holocene soils with incipient pedological features (humification, structuring, carbonation), developed under a semiarid climate.
In contrast, in El Arenoso site, were found gray paleosols in the alluvial sediments, with C/2Bgk1/2Bgk2/3C/4Bk/5Ck/6Bgk/6BCk/7Ck/8Bk/9Bg sequence, showing weathering, clay formation, redoximorphic and carbonation processes, dated by radiocarbon between 19.43 16.92 ka Cal BP (in pedogenic carbonates). Soil characteristics indicate the alternation between a moist environment (with weathering, rubification, clay formation and reductomorfía) and dry periods (with accumulation of carbonates).
Despite regional differences between late Pleistocene paleosols, the general trends of pedogenesis indicate the prevalence of a semiarid environment, slightly cooler and wetter than today, with winter rains, under which the first human groups and megafauna were established. In the middle Holocene occurred a marked increase in aridity, which decreased slightly in the late Holocene.
This trend of pedogenesis increased during the Pleistocene observed in Sonora is contrary to existing models globally, based primarily on the study of the sequences of loess - paleosols, which consider pedogenesis limited to interglacial and / or interstadials periods. However, similar trends to those observed in Sonora have been documented in other regions with similar geographical characteristics, showing the existence of at least two main palaeosols trends for that period.
... This general trend was interspersed with cooling 31 episodes. The first half of the following Archaic stage occurred during the Altithermal climate event from about 7500 to 4000 BP (Antevs 1955). ...
... Albion points at the stratigraphically broken and disturbed site 5DA3212 (Hedlund et al. in progress) (Figure 9). The 1999 context attributes the lack of Early Archaic sites on the Plains and the Palmer Divide to the warming and drying climate of the Altithermal period (about 7500 to 4000 BP) postulated by Antevs (Antevs 1955:329, Tate 1999. A period of pronounced temperature increase and corresponding eolian activity occurs between 7000-6700 cal BP (Gilmore 2012:6) Transhumance responses to the Altithermal by Early Archaic populations have up until recently been explained in primarily two different ways. ...
... charcoal in F12 is the result of environmental conditions or a cultural preference for burning rabbitbrush. The environmental conditions during the Early Archaic period Altithermal climatic event may have pushed Pinus sp. to higher elevations limiting the availability of fuel wood that was better than rabbitbrush (Antevs 1955). ...
The goal of this thesis is to identify and describe archaeological variation in precontact Native American hunter-gatherer hearths. Hearths are important and powerful sources of archaeological data because hearths are structures built through the culmination of a diverse collection of human decisions. Because so many decisions go into the manufacture, use, and abandonment of a hearth, the structures can be used to address research questions associated with subsistence and settlement. Hearth function and use are assessed through archaeological data, ethnology, and experiments. Hearth function is then used to inform understanding of land use (subsistence and settlement) through the lens of intensification on the northern edge of the Palmer Divide, Colorado.
Data are gathered from 20 excavated sites and 243 features that date between the Early Archaic (7500–5000 before present (BP)) and Early Ceramic (1850–800 BP) periods. The sites were selected because they do not span multiple ecological regions, limiting the potential environmental influences (i.e., resource availability) that may occur, for instance, between montane and alpine ecozones. Hearths are analyzed by date, location, substrate, morphology, size, fuel, rock use, rock attributes, hearth contents, packing material, and capping material. Patterns are then identified within and between hearth types and temporal periods. Those patterns are examined chronologically and against the backdrop of land-use intensification models.
The study reviews a variety of hearth types and uses, but notably, identifies the use of earth oven technology (hearth structures designed to process food in low-temperature high-moisture environments) during all reviewed temporal periods. This conclusion indicates that prehistoric hunter-gatherers were using intensification practices to extract as much from subsistence resources as possible. Importantly, the ways in which intensification happens and the resources that are subject to intensification also change throughout time. This change is best depicted at the transition from the Middle Archaic period (5000–3000 BP) to the Late Archaic period (3000–1800 BP) where abrupt changes in subsistence and hearth technology indicate an earlier appearance of Late Archaic adaptations than regionally expected. Finally, this study demonstrates that thermal features are understudied and that their complexity requires methods beyond those used in this thesis.
... The Early Agriculture Period (EAP) in the SW of USA and NW of Mexico begins just after the Altithermal period (7500 and 4500 yr BP), which represents the warmest and driest stage of the Holocene (Antevs, 1948(Antevs, , 1955. During the EAP agricultural societies cultivated corn and constructed canals for irrigation (Mabry et al., 2002;Diehl, 2009). ...
... The middle Holocene is characterized by a gradual shift towards drier conditions (less precipitation and higher temperatures), which result in changes in the ecosystem. This period is named as Altithermal (Antevs, 1955). The absence of archaeological artifacts in the Sonora desert suggests the inhospitable environmental conditions. ...
... This assemblage represents more land use at the site due to increasing herbs and tropical-desert trees. The earliest evidences of agriculture in the studied site coincide with the end of the Altithermal period (around 4500 yr BP, Antevs, 1955). Our records show that by this time a long period of landsurface stability ended, marked by the formation of a well-developed palaeosol, the SRP or the Big Red mentioned by Sánchez (2010) and Sánchez et al. (2014). ...
Environmental conditions and human-landscape interaction during the onset of the irrigated agriculture in Oasisamerica are not clear yet. In la Playa site (Sonora, NW Mexico), the evidences of sedentary population, land cultivation, and water management developed after the end of Altithermal period (around 4500 yr BP) include more than 550 archaeological features including hundreds of human cremations and a net of buried artificial channels. These findings were closely associated with several palaeosol levels alternating with sediments within a large alluvial fan. We studied micromorphological features, physical characteristics (color, texture, rock magnetic properties), and composition of organic matter, from three profiles (Maravillas, Zanja, and Cuatro Suelos), to reconstruct pedogenesis and sedimentary environment of the palaeosol sequences. Additional pa-leoenvironmental information was extracted from pollen assemblages, extracted from the Cuatro Suelos profile. The results pointed to a long period of geomorphic and climatic stability in the early-middle Holocene marked by a well-developed red Cambisol. This period was followed by an unstable interval around 4.5 kyr BP marked by severe erosion of earlier soil profiles and sedimentation of different kind: channel, floodplain, and fluvio-eolian. Later synsedimentary Fluvisols were formed showing signs of predominantly arid pedogenesis, interrupted by occasional flooding; indicators of human impact were also encountered. We conclude that the shift to irrigated agriculture as the main subsistence activity occurred during the period of major climatic and geomorphic fluctuation and then irrigation developed further under dry environment with limited water resources during the Late Holocene.
... The Early Agriculture Period (EAP) in the SW of USA and NW of Mexico begins just after the Altithermal period (7500 and 4500 yr BP), which represents the warmest and driest stage of the Holocene (Antevs, 1948(Antevs, , 1955. During the EAP agricultural societies cultivated corn and constructed canals for irrigation (Mabry et al., 2002;Diehl, 2009). ...
... The middle Holocene is characterized by a gradual shift towards drier conditions (less precipitation and higher temperatures), which result in changes in the ecosystem. This period is named as Altithermal (Antevs, 1955). The absence of archaeological artifacts in the Sonora desert suggests the inhospitable environmental conditions. ...
... This assemblage represents more land use at the site due to increasing herbs and tropical-desert trees. The earliest evidences of agriculture in the studied site coincide with the end of the Altithermal period (around 4500 yr BP, Antevs, 1955). Our records show that by this time a long period of landsurface stability ended, marked by the formation of a well-developed palaeosol, the SRP or the Big Red mentioned by Sánchez (2010) and Sánchez et al. (2014). ...
Environmental conditions and human-landscape interaction during the onset of the irrigated agriculture in Oasisamerica are not clear yet. In la Playa site (Sonora, NW Mexico), the evidences of sedentary population, land cultivation, and water management developed after the end of Altithermal period (around 4500 yr BP) include more than 550 archaeological features including hundreds of human cremations and a net of buried artificial channels. These findings were closely associated with several palaeosol levels alternating with sediments within a large alluvial fan. We studied micromorphological features, physical characteristics (color, texture, rock magnetic properties), and composition of organic matter, from three profiles (Maravillas, Zanja, and Cuatro Suelos), to reconstruct pedogenesis and sedimentary environment of the palaeosol sequences. Additional paleoenvironmental information was extracted from pollen assemblages, extracted from the Cuatro Suelos profile. The results pointed to a long period of geomorphic and climatic stability in the early-middle Holocene marked by a well-developed red Cambisol. This period was followed by an unstable interval around 4.5 kyr BP marked by severe erosion of earlier soil profiles and sedimentation of different kind: channel, floodplain, and fluvio-eolian. Later synsedimentary Fluvisols were formed showing signs of predominantly arid pedogenesis, interrupted by occasional flooding; indicators of human impact were also encountered. We conclude that the shift to irrigated agriculture as the main subsistence activity occurred during the period of major climatic and geomorphic fluctuation and then irrigation developed further under dry environment with limited water resources during the Late Holocene.
... The archaeological evidence of water wells is well documented in the Southern High Plains of the United States in sites such as Mustang Springs (41 MT 2), Blackwater Draw Locality #1, and Rattlesnake Draw sites (Texas and New Mexico, respectively) (Evans, 1951;Green, 1962;Meltzer, 1991;Meltzer and Collins, 1987;Smith et al., 1966). The presence of these water wells indicates a period of lowered water tables and extreme aridity, related to the presence of the Altithermal during the middle Holocene (Antevs, 1955;Meltzer and Collins, 1987: 10). Late-Holocene water wells have also been identified at Gila River Indian Community, in Southern Arizona. ...
... Water well digging and climatic disturbances are strongly connected in the case of North American plains. The presence of these water wells indicates a period of lowered water tables and extreme aridity, related to the presence of the Altithermal during the middle Holocene (Antevs, 1955;Evans, 1951;Green, 1962;Meltzer, 1991;Meltzer and Collins, 1987: 10;Smith et al., 1966). In this sense, in the North American cases, the excavation of wells was performed from erosional unconformities associated with severe droughts related to important climatic events such as the Altithermal and El Niño (Meltzer, 1991;Wright et al., 2013). ...
Water wells are ethnographically and archaeologically described in Australia and the plains of North America. Recently, a prehistoric water well from the Early Holocene was recorded in the Pampas of Argentina. The aim of this paper is to present the main characteristics of the water well, considering its form, dimension, sediment analyses (texture and chemical parameters), and material culture content. This is the first water well recorded in the Pampas of Argentina. Consequently, a discussion about natural or cultural origins of this kind of features is provided. An evaluation of similarities and differences with well-described water wells from United States and Australia is included in order to highlight the cultural origin of the pit. Also, the meaning of the cultural response to water availability in terms of Early Holocene hunter-gatherers adaptations as well as the implications of this strategy for understanding paleoenvironmental scenarios of the Pampas of Argentina are discussed. The well seems to have mitigated an exceptional lack of surface water in the eastern Pampas or offered an alternative for the non-drinkable quality of the available surface water. The strategy of digging water wells was available in the behavioral repertoire of the Pampean hunter-gatherer populations as early as ca. 8700-8000 14C years BP (ca. 9700-8800 cal. years BP), as these groups were fairly flexible and resilient in dealing with short-term shortages of water.
... Las propiedades detectadas en ellos se forman en periodos cortos de 1000 años (Targulian y Krasilnikov, 2007). De esta forma, el máximo cambio en el nivel de energía detectado en el paleosuelo 5 se ubicaría alrededor de 4500 años cal AP, es decir en el Holoceno medio, al término del periodo Altitermal (Antevs, 1955). Si comparamos esta secuencia edafosedimentaria con la encontrada en el río Boquillas, en la porción occidental de Sonora, cerca del poblado de Trincheras, se puede establecer que el patrón de variación no es sólo un fenómeno local. ...
RESUMEN En este trabajo se presenta un análisis integral del registro sedi-mentario y paleopedológico en una secuencia edafo-sedimentaria encontrada en la terraza baja del arroyo Tinajas, estado de Sonora. El objetivo de esta investigación es establecer los mecanismos de forma-ción de dicha secuencia que permitan hacer una reconstrucción de las condiciones paleoambientales. La secuencia consiste de un suelo moderno y once paleosuelos intercalados con sedimentos fluviales. Se determinaron sus propiedades físicas (color, granulometría), quí-micas (pH, conductividad eléctrica, contenido de calcio total), de magnetismo de rocas y micromorfológicas. Así mismo, se hizo la identificación de la mineralogía de arcilla por difracción de rayos X. Prácticamente todos los paleosuelos están decapitados. Debido a la falta de horizontes A, el marco cronológico de la secuencia se obtuvo usando una pequeña cantidad de materia orgánica encontrada en el pa-leosuelo 8. Para concentrar la materia orgánica, se hizo una extracción por desmineralización con ácido fluorhídrico. Esta materia orgánica desmineralizada se dató por 14 C por la técnica de AMS (Accelerator Mass Spectrometry), arrojando una edad de 8415 ± 39 años cal AP (Beta 473502). Los resultados muestran que los paleosuelos tienen un bajo grado de desarrollo. A pesar de ello, es posible establecer las principales tendencias pedogenéticas: la parte baja de la secuencia muestra paleosuelos de granulometría fina, con fuertes rasgos re-ductomórficos y propiedades vérticas. En contraste, los paleosuelos superiores son de textura más gruesa, con mayor porosidad biogénica e, inclusive, con revestimientos arcillosos. A partir del paleosuelo 7, se aprecia un cambio en la energía del relieve, dado por variaciones sedimentológicas (gradación inversa, aumento del tamaño de grano del sedimento), el cual es más evidente en los paleosuelos 2, 3 y 4, dada la alta concentración de gravas, mal seleccionadas y angulosas, que se asocian con procesos fluvio-coluviales. Suponemos que este cambio en el tipo de pedogénesis, sumado a las variaciones sedimentológicas, es debido a oscilaciones climáticas ocurridas en el Holoceno medio a nivel regional, ya que no se tiene documentada actividad tectónica reciente que pudiera influir. ABSTRACT In this work an integral analysis of a pedo-sedimentary sequence is presented, found in the lower fluvial terrace of the arroyo Tinajas, Sonora. The objective of this research is to establish the mechanism of the sequence formation in order to reconstruct the paleoenvironmental conditions. The sequence consists on a modern soil and eleven paleosols interbedded with fluvial sediments. The physical (color, grain size distribution , rock magnetic properties), chemical (pH, electric conductivity, total calcium content), and micromorphological properties are evaluated. The clay mineralogy determined by X-ray diffraction is also presented. Practically all the paleosols are truncated. Due to the lack of A horizons, the chronological frame of the sequence was obtained by using a small amount of organic matter found in the paleosol 8. To concentrate the organic matter, an extraction by demineralization with hydrofluric acid was used. This concentrated organic matter is dated by 14 C accelerator mass spectrometry (AMS), giving an age of 8415 ± 90 years cal BP. The results show that all paleosols are weakly developed. However, it is possible to establish the main pedogenetic tendencies: the lower part of the sequence is finer, with strong reductomorphic features and vertic properties. In contrast, the upper paleosols are coarser in texture, more porous Paleopedogénesis, sedimentación y evolución geomorfológica holocénica en el sistema fluvial del Arroyo Tinajas, Sonora
... Generally, Holocene climatic variation in northeastern California follows a general outline of that in western North America and the Great Basin (e.g., Antevs, 1948Antevs, , 1955. The terminal Pleistocene and early Holocene (10,000-7500 BP) are characterized by a general warming and drying trend and greater temperature and precipitation seasonality characterized by hot, dry summers and cool, wet winters (Broughton et al., 2008 and references therein). ...
... The middle Holocene corresponded to a gradual shift towards drier conditions (less precipitation and higher temperatures), which resulted in changes in the ecosystem. This period is referred to as Altithermal (Antevs, 1955). The absence of archaeological artifacts in the Sonora desert suggests the inhospitable environmental conditions. ...
... The Middle Archaic period (7,500-4,000 BP) coincides with the termination of the Paleoarchaic period and a pronounced climatic shift characterized by a warming and drying trend universally known as the Altithermal (Antevs 1955). This climatic shift caused the desiccation of pluvial lakes that occupied basin lowland settings across the Great Basin. ...
The “Big Dig” was an archaeological investigation carried out in 1962 and 1963 adjacent to the Tule Springs Fossil Beds, North Las Vegas, Nevada. The investigation was undertaken in an attempt to identify evidence of potential archaeological relationships between megafauna remains and human activity. The expedition is important for its association with the peopling of the Americas and for association with early applications of radiocarbon dating. The Tule Springs Expedition Base Camp, “Camp Harrington” has itself been recognized as a cultural resource (26CK6906). Statistical Research, Inc., developed a historic context for the Ice Age Fossils State Park (Swope et al. 2018), which contains the base camp. This article summarizes the story of the “Big Dig.”
... Broad Holocene climatic classification stages have been outlined for western North America (Antevs 1955;Hansen 1947). The Anathermal (12,000-7,000 B.P.) was a period of cooler, wetter climate im¬ mediately following the retreat of the late Pleistocene glaciers. ...
... The link between climate and culture in the southwestern United States (SW USA) has been discussed extensively in the literature [1][2][3][4][5] , although the overall Late Holocene climatic backdrop is not well known prior to 1200 years ago, which is beyond most compelling dendroclimatic records 6,7 . For example, there is a need to place into context Late Holocene megadroughts over several millennia. ...
While climatic triggers for collapse and population migrations of ancestral Pueblo communities have been proposed, little is known about the overall climatic backdrop for the entire pre-Hispanic Pueblo period (ca. 1300 to 460 B2K). Here, we report data from stalagmite HC-1, from Hidden Cave, Guadalupe Mountains, New Mexico, covering the past 3400 years, showing an interval of increased frequency of droughts from 1260 to 370 yr B2K that is coeval with the entire pre-Hispanic Pueblo period. Our record suggests that this puebloan Late Holocene climatic interval was the most arid and highly variable climatic period of the last 3400 years. Climatic conditions favoring the introduction of cultivation existed prior to the Pueblo period during more pluvial-like conditions from at least 3400 to 1260 yr B2K. Hence, the change from the Desert Archaic/Basketmaker to Pueblo cultures was associated with a quick transition to increasing aridity into and through the Pueblo period associated with greater urbanization and the establishment of pueblo population centers.
... Further work in southern California was done by the WPA in the 1930s (e.g., Winterbourne 1967) and by Walker (e.g., 1937Walker (e.g., , 1951) at a number of sites, including Malaga Cove; in the 1940s and 1950s by the University of California at sites such as Topanga (e.g., Heizer and Lemert 1947); and in the 1950s by Wallace (e.g., 1954). In 1955, Wallace (1955 produced the first general synthesis of southern California prehistory. Four cultural "horizons" were proposed: Horizon I (Early Man), Horizon II (Millingstone period), Horizon III (Intermediate period), and Horizon IV (Late period). ...
Project Location: The project area is located in the former
Ballona Lagoon, a prehistoric wetland complex in west Los
Angeles that is known collectively as the Ballona. This area
is today bound roughly by Playa del Rey to the west, Marina
del Rey to the north, the Ballona Escarpment (a high bluff )
and Del Rey Hills/Westchester Bluffs to the south, and Interstate
405 to the east. It is located approximately 0.5 km
east of the Pacific Ocean, 1.3 km west of the Baldwin Hills,
and 1.6–2.6 km north of Los Angeles International Airport.
Ballona Creek, a drainage that is now channelized, crosses
the project area; Centinela Creek, a spring-fed drainage, once
ran along the southern portion of the project area along the
base of the Ballona Escarpment.
Project Description: Statistical Research, Inc. (SRI), conducted
research, including data recovery, at five sites in the
Ballona: CA-LAN-54/H, CA-LAN-62/H, CA-LAN-193/H,
CA-LAN-211/H, and CA-LAN-2768/H. This involved the
creation of research designs for the investigations, a paleoenvironmental
study of the Ballona, and hand and mechanical
excavation of the sites themselves. These five sites were
recommended eligible for listing in the National Register of
Historic Places (NRHP) (Altschul et al. 1991, 1998, 1999,
2003; Keller and Altschul 2002; Van Galder et al. 2006; Vargas
and Altschul 2001; Vargas et al. 2005). A sixth site, CALAN-
2676, was recommended eligible and underwent data
recovery but was found to have been redeposited. This volume
provides an introduction to and background for the project;
it includes an introduction to the Playa Vista Archaeological
and Historical Project (PVAHP), an environmental setting for
the Ballona and the Southern California Bight, an updated
culture history for the southern California coast, a description
and discussion of previous research in the Ballona, an
updated research design for the PVAHP, and the results of
our paleoenvironmental study of the Ballona Lagoon area’s
evolution over the past 8,000 calendar years.
Project Summary: This volume presents several important
research findings on the paleoenvironment and prehistory
of the Ballona. An updated culture history for the Southern
California Bight allows a deeper understanding of regional
trends over the past 10,000 years and how those trends compare
to those in the Ballona. The updated research design
offers new insight regarding the research topics and theories
first proposed for the PVAHP and how they have evolved
through time. Over the course of 20 years, research goals
and objectives have changed to adapt to data recovery at
NRHP-eligible sites, as well as to research trends and topics
in California archaeology and in the discipline as a whole.
The paleoenvironmental study was conducted as part of the
PVAHP to provide insight regarding prehistoric use of the
Ballona Lagoon over the past 10,000 years. It was designed
to complement the archaeological excavations at sites in the
PVAHP and aimed at providing a geoarchaeological context
for interpreting the distribution of habitats and the evolution
of landscapes used by ancient peoples who lived in the
Ballona. Stratigraphic reconstruction of the Ballona Lagoon
indicates a system that was probably in static equilibrium
with sea-level rise after about 7000 b.p. and a lagoonal evolution
driven primarily by sediment in-filling rather than
by sea-level transgression or regression. Paleoenvironmental
and archaeological data indicate that both biological productivity
and human occupation in the Ballona reached a
peak between about 3000 and 2000 b.p.
... The growing body of palynological, isotopic, and tree-ring data suggests that, between 8,000 and 10,000 years ago, the climate was much cooler and moister (Heusser 1978;Pisias 1978). That period was followed by a period of warmer and drier conditions known as the Altithermal, which lasted until approximately 5,000 years ago (Antevs 1955). A study of oxygen isotopes indicated that environmental fluctuations were particularly dramatic during the past 3,000 years. ...
Project Location: The project area is located in the former
Ballona Lagoon, a prehistoric wetland complex in west Los
Angeles that is known collectively as the Ballona. That area is
today bounded, roughly, by Playa del Rey to the west, Marina
del Rey to the north, the Ballona Escarpment (a high bluff )
and Del Rey Hills/Westchester Bluffs to the south, and Interstate
405 to the east. It is located approximately 0.5 km
east of the Pacific Ocean, near Santa Monica Bay, along that
section of the coast; 1.3 km west of the Baldwin Hills; and
1.6–2.6 km north of Los Angeles International Airport. Ballona
Creek, a drainage that is now channelized, crosses the
project area; Centinela Creek, a spring-fed drainage, once
ran along the southern portion of the project area, along the
base of the Ballona Escarpment.
Project Description: Statistical Research, Inc., (SRI) conducted
research—including testing, evaluation to determine
eligibility for listing in the National Register of Historic Places
(NRHP), and data recovery—at eight sites in the Ballona
(CA-LAN-54/H, CA-LAN-62/H, CA-LAN-193/H, CALAN-
211/H, CA-LAN-1932/H, CA-LAN-2676/H, CALAN-
2768/H, and CA-LAN-2769/H) (hereinafter in this
volume, the prefix “CA-” and the suffix “/H” will be omitted).
Of those eight sites, five were recommended eligible for
listing in the NRHP: LAN-54, LAN-62, LAN-193, LAN-
211, and LAN-2768. Data recovery was conducted at those
five sites (Altschul 1991; Altschul et al. 1991; Altschul et al.
1998a; Altschul et al. 1999; Altschul et al. 2003; Keller and
Altschul 2002; Van Galder et al. 2006; Vargas and Altschul
2001a; Vargas et al. 2005). Research designs and plans of work
were developed and implemented (after review by regulatory
agencies). In addition, related research in the Ballona included
a paleoenvironmental study of the area (Volume 1 of the Playa
Vista Archaeological and Historical Project [PVAHP] series),
analyses and results of material classes and subsistence data
(Volume 3 of the series), and bioarchaeology (Volume 4 of the
series). The final volume in the series (Volume 5) synthesizes
the work presented in other volumes and offers detailed discussions
and modeling of the Native Californians, including
the Gabrielino/Tongva, who lived in the Ballona for thousands
of years. Volume 5 also includes detailed mortuary-analysis
ethnohistoric studies for the Ballona. This volume (Volume
2 of the series) presents the methods and results of the data
recovery at the five sites. In addition, it details the inventory
of the entire project area and documents additional sites that
either were found not eligible for listing in the NRHP or
were not evaluated.
Project Summary: This volume of the PVAHP series presents
the methodology and approach to large data recovery at
complex sites in an alluvial context, the results of the chronostratigraphic
reconstruction, and the descriptive results
of the data recovery, with emphasis on midden-constituent
analysis and feature typology. The long-term occupation in
the Ballona, from 8,000 years ago through the Mission and
early Historical periods, has been well documented through
these excavations. The large-scale excavations yielded large
data sets with complex temporal and spatial contexts that
are discussed in detail in this volume. This project is among
the very large-scale and rigorous studies of Native American
adaptations in the southern California coastal region, especially
for the Mission period Gabrielino/Tongva territory.
The data presented here illustrate both stability and change
in cultural systems extending back 8,000 years, including
denser occupations during the Protohistoric and Mission
periods. The most-pronounced changes occurred at the
beginning and end of the Intermediate period and at the
start of the Protohistoric and Mission periods.
... It is likely that the changes Van Devender (1990) identified are also linked to changes in ENSO and the NAM. Van Devender (1995) also suggests that the middle Holocene desert grassland was likely mesic, not dry as suggested by Antevs (1955). Van Devender's assertion is well supported by a wet period in both ciénega reconstructions that capture the middle Holocene (SBNWR and Cloverdale). ...
Millennial-scale environmental histories from North American desert southwest (SW) ciénegas were examined with existing time series for the North American Monsoon (NAM) and El Niño, in concert with published long-term records of desert vegetation and climate. The goal was to better understand the relationships among fire, the seasonality of precipitation, effective moisture levels, and vegetation type. It was determined that without sufficient winter precipitation fires are rare in desert SW ecosystems. However, it was also determined that in addition to winter moisture, summer ignitions are critical for fire in southwestern deserts. A relationship between the abundance of woody fuels and charcoal abundance was identified, although further calibration on charcoal production in woody vs. grassy desert settings in necessary to fully understand this interplay. Finally, the impacts of climate change and invasive species were considered, with both likely increasing the frequency of fire in desert ecosystems.
... Regionwide data-model comparisons support the idea of a drier LGM climate in the northwestern U.S. and a relatively wet southwestern U.S. (Oster et al., 2015a, b;Hudson et al., 2019). The comparatively wetter glacial climate in the southwestern U.S. has been attributed to a southward displacement of the polar jet stream and associated storm tracks (Antevs, 1955), which is a recurring feature in numerical simulations of LGM climate (Kutzbach and Wright, 1985;Thompson et al., 1993;Bartlein et al., 1998). After the LGM, when glaciers in some mountains were at or near their maximum lengths until as late as 15 ka (Licciardi et al., 2001;Thackray et al., 2004;Munroe et al., 2006;Young et al., 2011), Pacific-derived moisture likely increased throughout the region (Lyle et al., 2012;Munroe and Laabs, 2013;Ibarra et al., 2014) and the position of storm tracks varied across a broad range of latitudes (Lora and Ibarra, 2019;Hudson et al., 2019). ...
The geologic record of mountain glaciations is a robust indicator of terrestrial paleoclimate change. During the last glaciation, mountain ranges across the western US hosted glaciers while the Cordilleran and Laurentide
ice sheets flowed to the west and east of the continental divide,
respectively. Records detailing the chronologies and paleoclimate
significance of these ice advances have been developed for many sites across
North America. However, relatively few glacial records have been developed
for mountain glaciers in the northern Rocky Mountains near former ice sheet
margins. Here, we report cosmogenic beryllium-10 surface exposure ages and
numerical glacier modeling results, which show that mountain glaciers in the
northern Rockies abandoned terminal moraines after the end of the global
Last Glacial Maximum around 17–18 ka and could have been sustained by −10 to −8.5 ∘C temperature depressions relative to modern assuming
similar or less than modern precipitation. Additionally, we present a
deglacial chronology from the northern Rocky Mountains that indicates while
there is considerable variability in initial moraine abandonment ages across the Rocky Mountains, the pace of subsequent ice retreat through the
late glacial exhibits some regional coherence. Our results provide insight on potential regional mechanisms driving the initiation of and sustained
deglaciation in the western US, including rising atmospheric CO2 and
ice sheet collapse.
... BP), a period of significantly warmer summer temperatures punctuated by extended periods of drought. This period was first formalized as the Altithermal period in the work of Antevs (1955), which he characterized as representing a "Long Drought" lasting from 7500 to 4000 BP. Subsequent work interpreting the paleoclimate has indicated that the climate story in North America during this period was complicated, with the timing, duration and spatial distribution of drought varying widely during the middle Holocene. ...
The Bayou Gulch site is a prehistoric site located on a northwest-facing ridge overlooking the confluence of Bayou Gulch and Cherry Creek. Bayou Gulch is a multi-component site with evidence of occupation from the Early Archaic (7800 to 5000 BP, 6650 to 3800 BC) through Protohistoric (AD 1540–1860) periods. Based on previous investigations (Gilmore 1991; Larmore 2002) and the recent reassessment and reconciliation of the site and artifact assemblage (Gilmore, Espinosa et al. 2019), the most intensive occupations occurred during the Middle Archaic and the Early Ceramic periods. This Second Edition is an updated version of the original 2019 report submitted to the State Historical Fund in July of 2019 (Gilmore, Espinosa et al. 2019), and contains significantly more information and corrects many technical errors and omissions in the original 2019 document.
Approximately 450 m2 at the Bayou Gulch site were excavated by Colorado Department of Highways in 1979, representing the largest excavation in eastern Colorado to date (Colorado Department of Highways 1979). The 1979 excavation recovered nearly 100,000 artifacts, including hundreds of projectile points and more than 600 pottery sherds, an impressive number for the western Central Plains. Bayou Gulch is a defining site in Colorado and regional prehistory, used to establish and corroborate the chronological prehistory of eastern Colorado and the western Central Plains. Investigations in 2014 (Gilmore et al. 2014) and the current collections reanalysis determined that Bayou Gulch retains significant subsurface cultural deposits and has the potential to contribute information significant to the interpretation of regional prehistory.
... On the contrary, the Holocene climate was characterized by an aridity trend that ended with current environmental conditions. The driest and warmest conditions prevailed during the Altithermal period (7500-4500 cal yr BP), which was defined by Antevs (1948Antevs ( , 1955, as a period of severe aridity and drought accompanied by intense erosion. Several studies conducted in north-west Mexico and south-southwest United States have documented dry and warm conditions during that period (Gile and Grossman, 1968;Nettleton et al., 1975;Byrne et al., 1979;Weide, 1985;Holliday, 1989;Smith and McFaul, 1997). ...
Northern Mexico is predominantly composed of moderately developed red soils that provide evidence of weathering, rubification, neoformation of clay, and pedogenic carbonate accumulation. These soils constitute a pedological unit named San Rafael Paleosol (SRP) which were developed during the late Pleistocene (MIS 2) to the middle Holocene (15,000–4500 cal years BP). These paleosols can use as a chronologic marker at a regional scale. In this paper, we present a pedogenic interpretation of the paleosol-sedimentary processes during the late Quaternary, which contributes to the reconstruction of regional paleoenvironment. The development of SRP takes place over more than 15,000 years, and this pedogenesis is interrupted by stages of strong climatic instability, causing erosion of the SRP and sedimentation, presumably during the Altithermal. The records of La Playa show that SRP is buried by fluvial sediments, which include different facies. These sedimentation events are associated with the end of the Altithermal period and evidence more active geomorphic processes. These conditions are also observed at El Gramal, where dune sediments overly the SRP. This discontinuity evidence an intense erosional/sedimentation phase. In the particular case of El Fin del Mundo site, it is observed more mesic conditions as the water table rose, creating a wetland. Much of the synchronous variation in the morphology of the paleosols (pedofacies) can be explained by differences in local geomorphological conditions. These palaoesols developed under a semi-arid climate, slightly more humid than the present one with winter dominant rains and marked seasonal changes. These assumptions are supported by soil micromorphology, physical characteristics (color, grain size distribution) and composition of total organic and inorganic carbon. Additional paleoenvironmental information is also extracted from microbiomorphic analyses and diatoms assemblages from the one profile at El Fin del Mundo site.
... The middle Holocene, variously known as the Altithermal, the Climatic Optimum, the Thermal Maximum, the Xerothermic, or the Hypsithermal, is generally believed to have been a period of warming and drying that resulted in the expansion of prairie at the expense of forest (Antevs 1955;Delcourt and Delcourt 1985:19;Wright 1976). Ferring ascribes the development of the Arlington soil in the upper Trinity River valley to the middle Holocene period, feeling that it denotes a -period of flood plain stability or very slow flood plain aggradation that lasted ca. ...
This report presents the findings of the survey of 75 acres and the excavation of 28 cubic meters of site 41TR198 (Crooked Oxbow Site) within the Riverside Oxbow Project sponsored by the U.S. Army Corps of Engineers, Fort Worth District, in partnership with the City of Fort Worth and the Tarrant County Water District. Planned impacts from this proposed project include habitat restoration, channel reestablishment, vegetation plantings, new roads, and sports field construction. The deepest impacts planned for the Area of Potential Effects are one meter and involve the excavation of a shallow lake utilizing the relict oxbow bordering site 41TR198. Impacts planned for the remainder of the project area will be less than one-half meter deep. Overall, the project will attempt to use the existing landscape as much as possible in order to reduce impacts. As a federal agency the USACE is required to undertake cultural resource investigations for their projects in accordance with the National Historic Preservation Act of 1966, as amended through 2001. Since the Tarrant Regional Water District is the landowner and co-sponsor of the project, and a political subentity of the state of Texas, this project was also conducted under Texas Antiquities Permit No. 5040.
... Regionwide data-model comparisons support the idea of a drier LGM climate in the northwestern U.S. and a relatively wet southwestern U.S. (Oster et al., 2015a, b;Hudson et al., 2019). The comparatively wetter glacial climate in the southwestern U.S. has been attributed to a southward displacement of the polar jet stream and associated storm tracks (Antevs, 1955), which is a recurring feature in numerical simulations of LGM climate (Kutzbach and Wright, 1985;Thompson et al., 1993;Bartlein et al., 1998). After the LGM, when glaciers in some mountains were at or near their maximum lengths until as late as 15 ka (Licciardi et al., 2001;Thackray et al., 2004;Munroe et al., 2006;Young et al., 2011), Pacific-derived moisture likely increased throughout the region (Lyle et al., 2012;Munroe and Laabs, 2013;Ibarra et al., 2014) and the position of storm tracks varied across a broad range of latitudes (Lora and Ibarra, 2019;Hudson et al., 2019). ...
Surface exposure dating with terrestrial cosmogenic nuclides (TCNs) has become the primary method for determining numerical ages of Pleistocene mountain glacial deposits and landforms in the conterminous western United States (U.S.) and in numerous other glaciated settings worldwide. Recent updates to models of TCN production and scaling warrant a reconsideration of published exposure ages of moraines of the last two Pleistocene glaciations and associated paleoclimate inferences. Previously reported TCN exposure ages of moraines are recalculated here using newer production rates and scaling models for nuclides helium-3 (³He), beryllium-10 (¹⁰Be), aluminum-26 (²⁶Al), and chlorine-36 (³⁶Cl), in most cases yielding significant differences from originally reported ages. Recalculated TCN exposure ages of moraines of the penultimate glaciation display a high degree of variability for individual landforms, particularly toward the younger end of age distributions, suggesting that exposure history is affected by moraine denudation and that older age modes provide the best estimate of the depositional age of these moraines. Oldest exposure ages of penultimate glaciation moraines are well-aligned among mountain ranges across the western U.S. and yield a mean of 138 ± 13 ka, indicating that mountain glaciation occurred in step with global ice volume maxima during marine oxygen isotope stage 6. On average, terminal moraines of the last glaciation date to 19.5 ± 2.3 ka and correspond to the latter part of the global Last Glacial Maximum (LGM). Down-valley recessional moraines representing prolonged glacial stabilizations or readvances to ≥75% of maximum lengths have a mean exposure age of 17.0 ± 1.8 ka, suggesting that these moraine positions were last occupied during Heinrich Stadial 1. Evidence for multiple glacial culminations during the last glaciation is found in several mountain ranges and likely reflects at least two phases of Late Pleistocene climate: an earlier phase when glaciers attained their maximum length in response to cooling during the LGM, and a later phase when glaciers persisted at or readvanced to near-maximum lengths in response to sustained cold temperatures and/or increased precipitation.
... Stronger zonal airflow restricted the northward penetration of moist tropical air into the Central Plains, resulting in a warm, dry climate from ca. 8000-4000 yr B.P., i.e., during the Holocene Climate Optimum (HCO) or Altithermal (cf. Antevs, 1955). More recent simulations highlight the enhanced seasonal temperature cycle during the mid-Holocene (Braconnot et al., 2007), while other simulations suggest that mid-Holocene aridity in the Great Plains may be linked to orbitally induced enhancement of the summer monsoon in the American Southwest (Harrison et al., 2003). ...
A systematic study of floodplains, terraces, and alluvial fans in the Republican River valley of south-central Nebraska provided a well-dated, detailed reconstruction of late Quaternary landscape evolution and resolved outstanding issues related to previously proposed Holocene terrace sequences. Stable carbon isotope (δ13C) values determined on soil organic matter from buried soils in alluvial landforms were used to reconstruct the structure of vegetation communities and provided a means to investigate the relationships between bioclimatic change and fluvial activity for the period of record. Our study serves as a model for geomorphological and geoarcheological investigations in stream valleys throughout the central Great Plains and wherever loess-derived late Quaternary alluvial fans occur, in particular.
Holocene alluvial landforms in the river valley include a broad floodplain complex (T-0a, T-0b, and T-0c), a single alluvial terrace (T-1), and alluvial fans that mostly grade to the T-1 (AF-1) and T-0c (AF-0c) surfaces. Remnants of a late Pleistocene terrace (T-2), mantled by Holocene (Bignell) loess, are also preserved, and some Holocene alluvial fans (AF-2) grade to T-2 surfaces.
Radiocarbon ages suggest that the T-1 fill and AF-1 fans aggraded between ca. 9000−1000 yr B.P. Hence, nearly all of the Holocene alluvium in the river valley is stored in these landforms. Sedimentation, however, was interrupted by several periods of landscape stability and soil formation. Radiocarbon ages from the upper A horizons of buried soils in the T-1 and AF-1 fills, indicating approximate burial ages, cluster at ca. 6500, 4500, 3500, and 1000 yr B.P. Also, based on the radiocarbon ages, the T-0c fill and AF-0c fans were aggrading between ca. 2000−900 yr B.P. Given that the T-0c fill and upper parts of the T-1 fill were both aggrading after ca. 2000 yr B.P, we suggest that the T-1 surface was abandoned between ca. 4500−3500 yr B.P., but subsequent aggradation of both the T-1 and T-0c fills occurred due to large-magnitude flood events during the late Holocene.
The δ13C data indicate a shift from ∼40% C4 biomass at ca. 6000 to ∼85% at ca. 4500 yr B.P. We propose a scenario where (1) a reduction in C3 vegetation after 6000 yr B.P. destabilized the uplands, resulting in an increase in sediment supply and aggradation of the T-1 fill and AF-1 fans, and (2) the establishment of C4 vegetation by ca. 4500 yr B.P. stabilized the uplands, resulting in a reduction in sediment supply and subsequent incision and abandonment of the T-1 and most AF-1 surfaces. The proposed timing and nature of landscape and bioclimatic change are consistent with regional records from the central Great Plains.
... Climate became progressively warmer and more arid into the mid-Holocene causing grasslands to expand (Kornfeld et al. 2010;Valero-Garcés et al. 1997). Temperatures peaked at a point warmer than today during the Altithermal period (7000-4500 calendar years BP), which corresponds roughly to the Early Archaic (Antevs 1955;Neusius and Gross 2014). ...
The Licking Bison Site (39HN570) is located in Harding County, South Dakota and dates to 5570±30 14C yr BP (6406-6301 cal yr BP), during the Early Archaic period. The site was discovered in 1994 and excavated between 1995 and 2000 by the South Dakota State Archaeological Research Center (SARC). The Early Archaic corresponds with a period of warm and dry climatic conditions on the Northern Great Plains often referred to as the Altithermal. Archaeological sites from this time are relatively rare compared to both earlier and later periods. The Licking Bison Site is one of only two known bison kill sites from the Early Archaic of the region, and as such it has the potential to provide valuable information on prehistoric ways of life during the arid climatic conditions, as well as providing data about bison evolution. The faunal collection, housed at SARC, was analyzed to identify the species of bison, herd demographics (age, sex, MNI), and season of death. The excavated portion of the bonebed contained at least twenty-two individual bison killed and butchered by Early Archaic peoples in a single late fall kill event. The herd most likely consisted of predominately adult females, juveniles, and calves. Analysis of metacarpals shows at least four adult females and one adult male in the assemblage. The species of bison could not be identified due to a lack of well-preserved crania, but postcranial metrics suggest a possible slight trend towards Bison bison-sized individuals.
... Las propiedades detectadas en ellos se forman en periodos cortos de 1000 años (Targulian y Krasilnikov, 2007). De esta forma, el máximo cambio en el nivel de energía detectado en el paleosuelo 5 se ubicaría alrededor de 4500 años cal AP, es decir en el Holoceno medio, al término del periodo Altitermal (Antevs, 1955). Si comparamos esta secuencia edafosedimentaria con la encontrada en el río Boquillas, en la porción occidental de Sonora, cerca del poblado de Trincheras, se puede establecer que el patrón de variación no es sólo un fenómeno local. ...
In this work an integral analysis of a pedo-sedimentary sequence is presented, found in the lower fluvial terrace of the arroyo Tinajas, Sonora. The objective of this research is to establish the mechanism of the sequence formation in order to reconstruct the paleoenvironmental conditions. The sequence consists on a modern soil and eleven paleosols interbedded with fluvial sediments. The physical (color, grain size distribution , rock magnetic properties), chemical (pH, electric conductivity, total calcium content), and micromorphological properties are evaluated. The clay mineralogy determined by X-ray diffraction is also presented. Practically all the paleosols are truncated. Due to the lack of A horizons, the chronological frame of the sequence was obtained by using a small amount of organic matter found in the paleosol 8. To concentrate the organic matter, an extraction by demineralization with hydrofluric acid was used. This concentrated organic matter is dated by 14 C accelerator mass spectrometry (AMS), giving an age of 8415 ± 90 years cal BP. The results show that all paleosols are weakly developed. However, it is possible to establish the main pedogenetic tendencies: the lower part of the sequence is finer, with strong reductomorphic features and vertic properties. In contrast, the upper paleosols are coarser in texture, more porous Paleopedogénesis, sedimentación y evolución geomorfológica holocénica en el sistema fluvial del Arroyo Tinajas, Sonora
... rra regresó muy rápidamente a condiciones casi glaciales (es decir, fría, seca y ventosa), y permaneció así por cerca de 1 200 años. El aspecto más espectacular del Younger Dryas es que terminó muy abruptamente (hace alrededor de 11 600 años), y aunque la fecha no se puede saber exactamente, se calcula a partir del núcleo de hielo de Groenlandia con bandas anuales que la temperatura media anual aumentó en alrededor de 10° C en 10 años, es decir, se generaron las condiciones para el desarrollo de la agricultura y de una etapa de la vida humana de la que literalmente somos resultado (independientemente de que el Homo sapiens sapiens y otras especies en el árbol genealógico humano fueron testigos de estos procesos geológicos).En cambio, el Altitermal (también conocido como el Holoceno Medio) está fechado aproximadamente entre los años de 7 500 a 4 500 ap (5 500-2 500 aC), que es conocido como un periodo de estrés climático macrorregional representado por temperaturas muy altas y un descenso considerable de las lluvias(Antevs 1948;Antevs 1955). La severidad de las condiciones ambientales ocurrió de diversas formas de región en región; algunos autores consideran que en ciertas partes los grupos humanos tuvieron que adaptarse a las sequías, otros lugares fueron abandonados casi por completo y la gente tuvo que refugiarse en lugares con mayor elevación o con microclimas mucho más amigables(Betancourt et al. 1990; Holliday y Meltzer 1996; Meltzer y Holliday 2010; Carpenter y Sánchez 2013). ...
La relación de la investigación arqueológica con el análisis del cambio climático ha sido indisociable durante los últimos cien años. Analizando a detalle nos percatamos que las clasificaciones culturales guardan una estrecha relación con el clima. Las interpretaciones culturales parcialmente han sido el resultado de las combinaciones entre clima y cultura. Sin embargo, una cosa es el cambio climático global, sobre el que se ha discutido mucho, y otro, las fluctuaciones ambientales locales, que si bien no tienen efectos mundiales, son determinantes para el establecimiento, movilidad o desplazamiento de ciertos grupos en regiones particulares. Para discutir lo anterior me centro en el análisis de la arqueología del norte de México, específicamente en Sonora, donde se puede evaluar el impacto del cambio climático en procesos de larga duración. En el preludio, clarifico el uso de conceptos y describo de forma general las particularidades del desierto y los cambios climáticos asociados en su evolución geológica. En la segunda parte, me enfoco en las características culturales de la historia cultural sonorense. Afirmo que existe una relación intrínseca entre cambio climático y complejidad sociocultural. En la tercera parte puntualizo que el cambio climático global, no es el único causante directo de las transformaciones culturales, por el contrario, las fluctuaciones locales son aún mas determinantes en la dinámicas culturales. Concluyo argumentado que el análisis local de las fluctuaciones ambientales representa el tema de mayor interés y expansión en la investigación contemporánea sobre la relación entre pasado, clima y cultura.
... Rainfall amounts continued to decline in the continent's western interior where summer precipitation became increasingly erratic, opening up much of the remaining woodland to invasion by open savannas and shrub-steppe (Van Devender 1990, Metcalfe et al. 2000). Even greater climatic oscillations occurred during the Altithermal, a hot, dry period between 4,500 and 7,000 ybp, characterized by nearly total winter precipitation failure (Antevs 1955). ...
We consider the plant and animal assemblages within the various grasslands depicted
to not only be varied and large, but to contribute to a better understanding of each grassland’s history and evolution. This presentation therefore incorporates the biotic community concepts originally proposed by H. S. Swarth, Forrest Shreve, and V. E. Shelford; applied by D. I. Rasmussen, and formulated by C. H. Lowe, Jr.
... The characteristics of the Holocene cultures and environments of the Rocky Mountains are still poorly known. However, as data accumulate it becomes increasingly evident that simplistic models of the past climatic change, e.g., Antevs (1955) and culture change, e.g., Husted (1969), have outlived their usefulness, and the interpretation of past events require the development of more sophisticated models. The data and interpretations presented herein will, we hope, assist in the formulation of such models. ...
Salvage excavations at an archaeological site (D1Po-20) located in the Front Range of the Rocky Mountains in southwestern Alberta revealed the presence of a series of living floors, radiocarbon dated at ca. 4000, 4700 and 6000 B.C., in association with the Ah horizons of a series of buried soil profiles. While archaeological information is minimal, analysis of the buried soils indicates that they formed under a different vegetation cover from that on the site today. The earliest soil, a Degraded Alpine Eutric Brunisol, inferred to have developed under subalpine to alpine vegetation and a cold wet climate, suggests depression of the timberline on the order of 600 m. These climatic characteristics are considered to reflect those of the last valley glaciation (Pinedale IV). The two later buried soils, Orthic Regosols, developed under grassland vegetation reflective of a drier warmer climate, indicating the lower tree line shifted upwards a minimum of 30 m. A return to “normal” climatic conditions is correlated with the onset of the Neoglacial dated ca. 2800 B.C. in the Southern Alberta Rockies.
... Pollen records within the present groves show that giant sequoias began to increase dramatically with the onset of a slight global cooling at the end of the Altithermal era thousands of years ago (Antevs 1948(Antevs , 1955Anderson 1994, Anderson andSmith 1994). Though pollen records reflect small changes in the proportions of species to the present, the most dramatic changes were completed by about A.D. 900 (Graumlich 1993). ...
THE GIANT SEQUOIA NATIONAL MONUMENT SCIENTIFIC ADVISORY BOARD
Final Report
In the Beginning
On April 15, 2000 the President ofthe United States issued a Proclamation in which he declared , "The rich and varied landscape ofthe Giant Sequoia National Monument holds a diverse array of scientific and historic resources. Magnificent groves oftowering giant sequoias, the world's largest trees, are interspersed within a great belt of coniferous forest, jeweled with mountain meadows. Bold granitic domes, spires, and plunging gorges texture the landscape." He concluded that it would be in the public interest to reserve such lands as a national monument to be known as the Giant Sequoia National Monument.
The Secretary ofAgriculture was to prepare a management plan within 3 years. The Secretary in consultation with the National Academy ofSciences was to appoint a Scientific Advisory Board to provide scientific guidance during the development ofthe initial management plan. Board membership shall represent a range of scientific disciplines pertaining to the objects to be protected, including, but not necessarily limited to, the physical, biological, and social sciences. The Board was appointed, has served, and herewith respectfully submits its Final Report.
Introduction
Landscapes held in public trust are difficult to manage; a living National Monument subject to increased public use presents additional challenges. These landscapes are subject to regional and global effects outside the manager's control, such as global climate change and air pollution. They are also subject to innumerable local variables, most ofwhose effects are difficult to predict. The giant sequoia groves and their surrounding ecosystem are fiercely loved by many; although the goals may be broadly similar, the objectives and policies ofthese giant sequoia lovers are often sharply at odds.
The Proclamation challenges the Board to work with the Forest Service in establishing a Management Plan that balances the need to restore and counteract the effects ofa century of fire suppression and logging, increased human use ofthe Monument, and preservation ofthe essential features that led the President to proclaim the Monument for similar use and appreciation in the future.
Most of the topography and drainage of the Mississippi River system has developed within relatively recent geologic time. In contrast to the relative geographic stability for location of the lower Mississippi River, the headwaters of the upper Mississippi River system appear to have experienced considerable modifications during the last 2.5–3.0 million years in response to regional advances and retreats by continental glaciers. Holocene backswamp environments have accumulated from 10 to 35 m of sediment deposited during overbank flooding. Thickness of the deposits increases downstream in the Lower Mississippi Valley. The longitudinal profile of the Mississippi River does not possess a smooth concave‐upward morphology that is typical of most large alluvial rivers. During the Wisconsin Stage of glaciation the Mississippi River system drained nearly the entire southern margin of the continental (Laurentide) ice sheet.
Recognition of climate change impacts on river systems arose in the 1800s, soon after glacial theory. By the early 20th century, multiple theories competed to explain how a specific climate shift would affect river system behavior, with some emphasizing the role of sediment production and others emphasizing runoff production. Non-climatic factors, such as tectonics, sea-level change, and human impacts also needed to be considered. In the late 20th century, developments such as radiocarbon and other dating methods, paleohydrological records, sediment budget studies, the orbital theory of climatic change, recognition of shorter-term climatic events, and more data on modern river processes led to more sophisticated theories of fluvial response to climate change. At the same time, theories of non-linear and autogenic behavior called into question whether fluvial response to climate change was detectable. Today most geomorphologists believe that fluvial records reflect climate changes, but complex and non-linear response, as well as non-climatic controls, must be considered in any interpretation. Computer models are powerful tools for testing theories of fluvial response, but are only beginning to be applied to modelling response to climatic change. The challenge of near-future anthropogenic climate change is likely to spur further development of fluvial system models and theory.
Modulating days to flowering is a key mechanism in plants for adapting to new environments, and variation in days to flowering drives population structure by limiting mating. To elucidate the genetic architecture of flowering across maize, a quantitative trait, we mapped flowering in five global populations, a diversity panel (Ames) and four half-sib mapping designs, Chinese (CNNAM), US (USNAM), and European Dent (EUNAM-Dent) and Flint (EUNAM-Flint). Using whole-genome projected SNPs, we tested for joint association using GWAS, resampling GWAS and two regional approaches; Regional Heritability Mapping (RHM) ( 1 , 2 ) and a novel method, Boosted Regional Heritability Mapping (BRHM). Direct overlap in significant regions detected between populations and flowering candidate genes was limited, but whole-genome cross-population predictive abilities were ≤0.78. Poor predictive ability correlated with increased population differentiation (r = 0.41), unless the parents were broadly sampled from across the North American temperate-tropical germplasm gradient; uncorrected GWAS results from populations with broadly sampled parents were well predicted by temperate-tropical F ST s in machine learning. Machine learning between GWAS results also suggested shared architecture between the American panels and, more distantly, the European panels, but not the Chinese panel. Machine learning approaches can reconcile non-linear relationships, but the combined predictive ability of all of the populations did not significantly enhance prediction of physiological candidates. While the North American-European temperate adaption is well studied, this study suggest independent temperate adaptation evolved in the Chinese panel, most likely in China after 1500, a finding supported by differential gene ontology term enrichment between populations.
The petrology and stratification of the late Pleistocene and Recent mesa deposits in the Mesa Verde area are described. These deposits are believed to have been formed by eolian deposition. Measurements of present-day dust accumulation are reported. The age relationships of the strata are discussed on the basis of measurements of the radioactivity of organic carbon and carbonate precipitates and with reference to the early Mesa Verde culture.
Our of the dust of time
comes a nation's heritage.
Eugene W. Ingle
Growing on shifting sand dunes in central Utah is a small endemic population of a gigas form of A triplex canescens. Whereas normal A. canescens usually grows to a height of three to four feet and occasionally to five or six feet, the gigas form often reaches ten and sometimes twelve feet. All normal A. canescens so far examined (67 populations) have 2n = 36 chromosomes; the gigas form has 2n = 18 chromosomes. Several lines of evidence suggest that the gigas form is a relic diploid and the normal form is an autotetraploid derived from it. The growth rate of seedlings and new twigs is nearly twice as great in the diploid as in the tetraploid. Seed germination is faster and much better in the diploid. The tetraploid is reproductively isolated from the diploid because of a much earlier flowering period. The diploid plants possess many attributes which make them uniquely adapted to the drifting sand dune habitat.
Tucker, J. M. (U. California, Davis.) Studies in the Quercus undulata complex. III. The contribution of Q. arizonica. Amer. Jour. Bot. 50(7): 699–708. Illus. 1903.—Of the 7 oak species involved in the Quercus undulata complex, Q. arizonica contributes the least of all. The latter has hybridized with Q. gambelii at a few widely separated localities (listed in Table 1) in central Arizona, and northern Sonora and Chihuahua, Mexico. The putative hybrids (identifiable as Quercus undulata) occur as isolated individuals with the parental species. The parents, although regionally sympatric, are usually ecologically isolated. They differ in a number of morphological characters, 6 of which were analyzed in detail. The resulting data, presented as pietorialized scatter diagrams, demonstrate that the putative hybrids are intermediate, in general. This is taken as evidence of their hybrid nature. Factors limiting hybridization in oaks are discussed. It is speculated that hybridization between Q. arizonica and Q. gambelii has occurred since the postglacial hypsithermal interval.
In May 1978, a general freeze of the male flowers of Gambel oak (Quercus gambelii Nutt.) was observed in northern Utah. In August, transect reconnaissance was conducted throughout Utah to assess acorn production and the incidence of freeze damage in Gambel oak. It was found that below ca. 1950 m elevation acorn production was relatively low while the incidence of freeze damage was high. Above ca. 1950 m elevation, where the oaks were still dormant at the time of the freeze, acorn production was relatively high while freeze damage was relatively low. Occasional acorn production observed at low elevations appeared to be associated with subterranean pooling of water and/or cold air drainage. Some biogeographic implications of freeze stress are discussed.
Much of the variation in hexaploid Atriplex tridentata appears to have come from tetraploid A. canescens by introgression. Among the recombinations, three types appear to have become established as new, adaptive, hexaploid derivatives. One of these is a robust, woody form near Knolls, Utah, another is a widespread, low-growing, shrubby form in Lander County, Nevada, the other is an upright bushy, canescens-like form near Grantsville, Utah.
Tucker, J. M. (U. California, Davis), W. P. Cottam, and R. Drobnick. Studies in the Quercus undulata complex. II. The contribution of Quercus turbinella. Amer. Jour. Bot. 48(4): 329–339. Illus. 1961.—Quercus undulata has been interpreted as a hybrid complex involving Q. gambelii and several other species, including Q. turbinella (Tucker, 1961). In the present paper, the total distribution of the hybrids between Q. gambelii and Q. turbinella is given. Lacking direct genetic evidence, proof of hybridity is sought in a demonstration of the morphological intermediacy of these putative hybrids. Population samples of both parental species, other samples containing hybrids, and numerous individual hybrids, are analyzed on the basis of 6 differences between the parental species. The data obtained, presented in the form of pictorialized scatter diagrams, clearly show the general intermediacy of the hybrids. Of the various binomials that have been applied to forms in the Q. undulata complex, Quercus pauciloba Rydb. applies to this hybrid. The appropriate change in status (Quercus × pauciloba Rydb.) is made.
Creosote bush clones in the Mojave Desert develop by irregular radial growth, stem segmentation and the production of new stems at the outer edge of stem segments. The resulting circular clone encloses a central bare area as the central dead wood rots away. Old clones become elliptical and may exceed 20 m in length. Modern growth rates estimated from annual increments in stem wood of seedlings (0.73 mm/yr) and young clones (0.82 mm/yr) approximate those estimated for radiocarbon-dated wood samples (0.66 mm/yr). Assuming comparable growth rates through time, the extrapolated age of the largest known clone (average radius = 7.8 m) may approach 11,700 years. If growth rates have changed, that clone's age may be somewhat less.
A comparison of evidence from linguistics, archaeology, ethnography and history suggests that the separation of Northern and Southern Athabascans in the first millennium A.D. may have been provoked by warming conditions and resultant shifts in the distribution of major game species. The “mixed bag” subsistence pattern of most Athabascan groups, as well as their association with mountainous areas which provide access to a variety of ecological zones, lends weight to the hypothesis that mountain ranges were the medium for Apachean migration into the Southwest. A hypothetical reconstruction of this transition from the Subarctic to the Southwest is presented and discussed.
Studies of the stratified sediments of Bonfire Shelter, southwest Texas, were conducted as an outgrowth of earlier research by Dibble and others. Stratigraphic analysis, granulometry, and mineral studies address the observable variations in the natural and cultural strata. Results favor climatic fluctuations and the introduction ofexogenous particles instead of lithologic vagaries of the limestone as explanations for the variations. Sedimentand pollen data from matched samples taken from the bison bone beds were correlated. The implications for paleoclimate and plant communities are similar for these temporally disjunct strata. They were both deposited in periods of ameliorating climate preceded and followed by periods of sharply colder winters. Plant communities showed the loss of some tree elements, replaced by brushier species and a continuation of grasses. The human groups exploiting the bison probably migrated into the region from the High Plains during more equitable climatic periods.
If Reeves (1973) is correct that sampling errors explain low Early Archaic site frequency in many parts of the Great Plains, then recent research in previously unsurveyed regions should reveal Paleoindian, Early Archaic, and Middle Archaic site frequencies significantly different from those reported by Reeves. A chi-square test indicates significant differences do occur between the frequencyofsites reported by Reeves and those reported by recent surveys. However, analysis of adjusted residuals indicates significant differences are not associated with the frequency of Early Archaic sites. While Paleoindian and Middle Archaic site frequencies provide support for Reeves’ prediction, it remains to be determined why Early Archaic site frequency does not. It may be argued that Altithermal climatic conditions did significantly alter grassland ecology and did require significant adaptive responses from indigenous Plains populations.
The Beaver Creek Shelter contains the most complete Holocene section in the Black Hills and evidence for the regional cultural transition between the Early and Middle Archaic periods, from approximately 6720 to 3800 years ago. Test excavations were limited to 22 stratigraphic units through 4. 77 m of section, ranging in age from 9380 years to 1750 years ago. Mollusk, plant, and vertebrate remains occur throughout the section, and provide documentation for Holocene environmental change in the southern Black Hills. Shelter occupation was during warm seasons by peoples engaged in hunting and food processing activities utilizing locally available raw materials. The McKean cultural complex in this locality represents a continuation of the life-styles represented in the later portion of the Early Archaic period Changes in artifact styles, lithic composition, and reduction of the numbers of modified flakes and debitage, however, suggest that changes in site utilization may have occurred by the Middle Archaic period
The remarkable finds from the trans-Holocene archaeological record excavated at Hogup Cave, Utah, helped define our understanding of Great Basin prehistory. However, many scholars doubt the integrity of the site's depositional sequence and resulting chronological interpretations. To resolve these concerns, we produce several Bayesian chronological models combining 14 new radiocarbon dates with the results of past dating efforts. We first present an examination of the excavation and previously derived dates, finding that several of the most anomalous dates can be accounted for by details in the excavation's field notes. We then report our new dates and construct an initial Bayesian chronological model to serve as a framework for three increasingly complex models synthesizing old and new dates from the site. The best-supported model divides the site's stratigraphy into four occupational phases: Strata 1 through 7 (9790 to 6490 cal B.P.), Stratum 8 (5840 to 3330 cal B.P.), Strata 9 and 10 (2870 to 2760 cal B.P.), and Strata 11 through 16 (2610 to 360 cal B.P.). This result raises several questions to direct future research and dating efforts at Hogup Cave and serves as a model for reevaluating complex stratigraphic sequences in western North America and beyond.
A robust collection of mammal, bird, fish, and shellfish remains from an 8,000-year residential sequence at Morro Bay, a small, isolated estuary on the central California coast, shows a strong focus on marine species during the Middle-Late Transition cultural phase (950–700 cal B.P.), which largely coincides with the Medieval Climatic Anomaly (MCA). Previous studies have provided modest evidence for increased fishing and rabbit hunting during the MCA in adjacent regions, but the Morro Bay findings suggest a distinctive marine-focused subsistence refugium during the period of drought. Specifically, the sequence shows striking all-time peaks in marine and estuarine birds, fish NISP/m ³ , and fish/deer + rabbits during the MCA. Heavy exploitation of fish, aquatic birds, rabbits, and shellfish suggests that the bow and arrow, which seems to have arrived in the area at this time, had little impact on local subsistence strategies.
During the spring of 2006 (May 11 through May 18, 2006), the Center for Archaeological Research (CAR) at The University of Texas at San Antonio conducted testing at 41BP679, a site formally listed as a State Archaeological Landmark. Site 41BP679 is located in Bastrop County at the confluence of the Colorado River and Spring Branch Creek, one of its tributaries. The site is on land that is the proposed location for the City of Bastrop Wastewater Treatment Plant. The installation of outflow pipes will impact the northern portion of 41BP679. The testing was conducted under Texas Antiquities Permit No. 4117, with Kristi Ulrich serving as Principal Investigator and Cynthia Moore Munoz serving as the Project Archaeologist. The testing involved mechanical auger borings, backhoe trenching and the hand-excavation of a limited number of test units.
Testing confirmed that 41BP679 is likely to be a single component site (30-70 cm below surface) dating from the Paleoindian to Archaic period. One temporally diagnostic artifact, a Clear Fork tool, was recovered. Testing efforts failed to encounter features, and the low density cultural materials consist primarily of lithic debitage, burned rock and a handful of lithic tools. A detailed debitage analysis of the samples from the site suggests that the debitage collection represents a focus on tool production.
The low density cultural remains have been impacted by bioturbation and vegetation clearing or plowing and their research potential is limited. The portion of the site tested during the investigations reported herein, along with the materials recovered, do not contribute to the State Archeological Landmark eligibility of 41BP679. We therefore recommend that the planned construction be allowed to proceed. We also recommend that the portion of the site located to the south of the area tested by CAR remain protected.
The Texas Historical Commission (THC) concurred with the conclusions and recommendations reached by the CAR. In addition, the THC requested that the portion of 41BP679 not assessed by CAR be protected from potential construction-related impacts by a fence. The desired location of the fence would be furnished by CAR to insure that intact portions of the site are not adversely affected by the fence’s construction. Furthermore, if significant archaeological deposits are uncovered during plant construction, the THC requested that all work should stop in those immediate areas and the City of Bastrop should immediately contact the THC.
CAR staff informed the City of the THC request. City representatives have indicated to CAR that fencing will be installed around the perimeter of the construction area both to keep people out of the construction area and keep construction impacts limited to the designated area. The fence will be a five-strand barbwire fence.
All artifacts collected during this project are curated at the Center for Archaeological Research according to Texas Historical Commission guidelines.
During the spring of 2006 (April 27 through May 4, 2006), the Center for Archaeological Research (CAR) at The University of Texas at San Antonio conducted testing at 41BP678, a site formally listed as a State Archaeological Landmark. Site 41BP678 is located in Bastrop County at the confluence of the Colorado River and Spring Branch Creek, one of its tributaries. The site is on land that is the proposed location for the City of Bastrop Wastewater Treatment Plant. The installation of outflow pipes and the excavation of a 500-foot deep water well and associated utilities installations will impact the central and eastern portions of 41BP678. The testing was conducted under Texas Antiquities Permit No. 4117, with Kristi M. Ulrich serving as Principal Investigator and Antonia L. Figueroa serving as the Project Archaeologist. The testing involved mechanical auger borings, backhoe trenching and the hand-excavation of a limited number of test units.
Testing confirmed that 41BP678 is a multi-component site, with a Late Prehistoric presence in the upper 40 cm of the site, and a second component (40-80 cm below surface) of unknown temporal affiliation. Testing efforts failed to encounter features, and the low-density cultural materials consist primarily of lithic debitage and fire-cracked rock. A detailed debitage analysis of the samples from the two components suggests that the Late Prehistoric debitage collection represents a focus on tool production while the underlying component resembles an assemblage focused more on core reduction. This pattern suggests that site activities may have changed over time.
The low-density cultural remains have been impacted by bioturbation and vegetation clearing or plowing and their research potential is severely limited. CAR recommends that the portion of the site tested during the investigations reported herein, along with the materials recovered, do not contribute to the State Archeological Landmark eligibility of 41BP678. We therefore recommend that the planned construction be allowed to proceed. We also recommend that the portion of the site located to the south of the area tested by CAR remain protected.
All artifacts collected during this project are curated at the Center for Archaeological Research according to Texas Historical Commission guidelines.
In a paper published in the Monthly Weather Review in September, 1933, the author discussed long‐time temperature trends, and presented data showing that an unusual and extended warm phase of climate had at that time developed through a more or less regular rise in temperature for a comparatively long period of years. The paper also showed that the prevailing condition was widespread, in fact apparently world‐wide, and in addition that temperature data up through 1932, the terminal of the records presented in that paper, afforded no indication of an impending trend reversal to more normal thermal conditions in the then near future.
Up to the end of 1945, records for 13 subsequent years have become available, and these are here presented, supplementary to the original data, to determine tendencies since 1932. They show that the general upward temperature trend continued for several years but that the more recent records Indicate a leveling off, and even contain currently a suggestion of an impending reversal.
The Committee on Glaciers at present is constituted as follows:
Harry Fielding Reid—Professor‐Emeritus of Geology, Johns Hopkins University (former member of the International Glacier Commission), 608 Cathedral Street, Baltimore, Maryland
William H. Hobbs—Professor‐Emeritus of Geology, University of Michigan (until recently Vice‐ President of the International Glacier Commission, at present associate member), Ann Arbor, Michigan
J. E. Church—Professor of Classics, University of Nevada (President of the International Commission of Snow, and Chairman of the Committee on Snow of the Section of Hydrology, American Geophysical Union), Reno, Nevada
Colonel Lawrence Martin—Chief of the Division of Maps, Library of Congress, Washington, D. C. Wm. Osgood Field, Jr.—Explorer, 18 West Twelfth Street, New York, N.Y.
Earl A. Trager—Chief of the Naturalist Division, National Park Service, Washington, D. C.
Glenn L. Parker—District Engineer, Water Resources Branch, United States Geological Survey, 406 Federal Building, Tacoma, Washington
Oliver Kehrlein—Chairman, Committee on Glacier Studies, Sierra Club, 1050 Mills Tower, San Francisco, California
Kenneth N. Phillips—Associate Hydraulic Engineer, Water Resources Branch, United States Geological Survey, Chairman, Research Committee of the Mazamas, 606 Post‐Office Building, Portland, Oregon
William S. Cooper—Professor of Botany, University of Minnesota, Minneapolis, Minnesota Gerald FitzGerald, Senior Topographic Engineer, Alaska Branch, United States Geological Survey, Washington, D.C.
Laurence M. Gould, Professor of Geology, Carleton College, Northfield, Minnesota
François E. Matthes, Chairman , Senior Geologist, Section of Glacial Geology, United States Geological Survey (titular member of the International Glacier Commission), Washington, D.C.
In 1938, as in previous years, the Committee devoted its energies primarily to the collecting of data on the variations in length and volume of American glaciers, it being felt that the maintenance of a continuous record of these variations is of prime importance, not only to hydrology and glaciology, but, as has become increasingly evident recently, also to climatology, geomorphology, geography, ecology, history, and archaeology. As the time available for the work of the Committee is limited and does not permit covering the entire field of glaciology, it seems best to devote it before all else to this line of research which yields results of value to so many different sciences. Besides, the gathering of data on glacier‐oscillations is not a one‐man job that can be taken up or dropped at convenience from time to time, but is an organized and far‐flung enterprise whose success depends upon the faithful cooperation of many volunteer workers located in different parts of the country. Such an enterprise, once launched, must be kept running or it will disintegrate and the precious enthusiasm of the field‐workers will be lost.
In september, 1949, while in west central Nevada for the purpose of collecting vegetal materials from the lowermost cultural levels of Lovelock cave (Loud and Harrington, 1929) to be used for radiocarbon dating, the author revisited an open rockshelter site some six miles up the valley from Lovelock cave. The site, since named Leonard rockshelter (site 26- Pe-14) after Zenas Leonard who in 1833 traversed the Humbolt Sink area as a member of the Walker expedition (Leonard, 1904), is not referred to by Loud and Harrington. It is the same site from which, in 1936, Thomas Derby mined bat guano and recovered artifacts described in a brief article (Heizer, 1938). The bat guano formed a layer two to three feet thick lying on ancient gravels of Lake Lahontan and beneath a thick accumulation of aeolian dust and rockfall.
Prehistoric shaft-like excavations which may have been aboriginal water wells were discovered in the fall of 1949 and the summer of 1950 at the well-known early man site 12 miles southwest of Clovis and 7 miles north of Portales, New Mexico. Work at this site is part of an extended program of geologic studies of Quaternary deposits on the High Plains of western Texas and eastern New Mexico being carried on by the Texas Memorial Museum. A report dealing with the geology and ancient archaeological horizons at the Clovis site will be ready for publication in the near future, but a separate description of the shafts or wells seems desirable at this time.
Kroeber's classic study of the “Cultural and Natural Areas of Native North America” has been invaluable to eth' nologists and archaeologists working with cultural phenomena more recent than the beginning of the Christian era. However, it has become increasingly evident that the cultural and natural areas of the neo-Indian (the term used by Griffin, 1946, p. 38) were not necessarily those of the paleo-Indian (the term used by Roberts, 1940, pp. 51-116). It is therefore my intent here to outline briefly, and without much detail, the cultural and natural areas of the paleo-Indian.
I have focused my attention upon glaciation, because the presence of a continental glacier seems to have been a major factor of North American paleogeography in the periods here considered. Climate, which possibly is more the result of, than the cause of, glaciation, I have interpreted in terms of pollen levels, and any other phenomena that I could understand.
A core sample of the bottom in the southeastern Pacific Ocean contains several layers of red clay and globigerina ooze. The highly calcareous ooze is correlated with warm-water conditions, whereas the red clay, which is low in carbonate, is correlated with cold-water conditions because the carbonate is more soluble in cold water. The core is interpreted as a record of climate. Age determinations made by W. D. Urry, using the "percentage of equilibrium method" for uranium, ionium, and radium give dates for the various layers covering a period of several hundred thousand years. The detailed interpretation of this core gives dates for the end of the Kansan glacial stage (about 700,000 years ago), for three substages of the Illinoian glacial stage (330,000; 310,000; and 274,000 years ago), for six substages of the Wisconsin glacial stage (64,000; 51,000; 37,000; 26,000; 15,000; and 11,000 years ago), and for a postglacial thermal maximum centering at 6,000 years ago. There is good correlation between the Pacific red-clay (cold-water) zones of Wisconsin age and the North Atlantic and Antarctic glacial marine zones of the same age.
A variety of evidence suggests that the borders of the Cary and Mankato drift sheets cross eastern New York and New England, that there were two and perhaps three late Wisconsin marine invasions of the St. Lawrence lowland, and that there exist logical eastern correlatives of the low-water phases in the glacial upper Great Lakes, in the form of till-covered marine deposits, the abandoned, drift-filled Niagara gorge, and the North Bay-Ottawa River lake-outlet channel.
The suggested events from the Gary maximum to the present are assembled in a correlation chart for comparison and criticism. Although the scheme proposed is suggestive only, it is consistent with ecology implied by fossils, with the dates and amplitudes of known crustal movements, and with the radium- and radiocarbon dates of the dated materials collected from the region.
Sierran glaciers reached Lake Russell in the late Pleistocene, and shore lines cut in lateral moraines of the next-to-last glacial stage (Tahoe) extend into troughs vacated by the ice at the close of that stage. During the waning phase of the last glacial stage (Tioga) conspicuous shore lines were carved on slopes bordering present Mono Lake. Terminal moraines of the Tioga stage, nested inside moraines of the preceding advance, reach the uppermost shore lines of Mono Lake and appear to be contemporaneous with its last expansion. Both the Tioga terminal and recessional moraines show that ice retreat was pulsatory, with several relatively long halts interrupting times of rapid recession. The comparatively stationary ice fronts probably can be correlated with broader lake terraces, the rapid ice withdrawals with narrower terraces.
A section of lake beds exposed in the sides of the trench of Ana River below Ana Spring near the northwest corner of Summer Lake basin in Lake County, Oregon, reveals near the top at least six layers of pumice. Four of these appear to record eruptions of Mount Mazama which led finally to the formation of Crater Lake; the source of the fifth is not known; the sixth is attributed to a later eruption of Newberry Crater. As certain layers in the associated sediments imply shallow-water conditions, these eruptions must have occurred when the last pluvial lake, formerly about 215 feet deep, had been reduced by evaporation to a depth of about 85 feet, probably about 14,000 years ago. The data appear to extend back the ages of Mount Mazama pumice, of Crater Lake, and of Paleo-Indian occupation of the area by several thousand years.
On the west flank of the Sawatch Range, Colorado, evidence is found for six distinct glacial advances One glaciation is pre-Wisconsin, four are Wisconsin, and one post-Wisconsin in age. In addition to end and lateral moraines of each advance, terrace remnants of six valley trains were identified and studied for a distance of 25 miles along Frying Pan River and its major tributaries. Elevations above stream level of these outwash terraces are 400-450, 90-120, 50-40, 20-30, 12-17, and 6-8 feet. Five of the tributary valleys contained large ice streams which did not join the trunk Frying Pan glacier during the Wisconsin stage. Extensive review and testing of the numerous criteria used to distinguish deposits of multiple glaciations show that nine of these criteria can conveniently be expressed in parameters indicative of relative age. Estimates based on these criteria, coupled with a recent radiocarbon dating of late Mankato till in the Midwest, yield the following approximate ages for deposits of the six glaciations in Frying Pan Valley: 230,000, 63,000, 46,000, 17,000, 11,500, and 5,750 years. The accuracy and reliability of the procedure used cannot be evaluated without further absolute Carbon 14 age determinations.
On the basis of Hans Ahlmann's determinations of the temperature at the glaciation limit, the altitude of the mean June-September isotherm of 36° F. is taken as the modern climatic snow line in New Mexico. This plane naturally rises southward. The actual snow line of the last glacial maximum, probably the Cary of more than 24,000 years ago, is determined mainly from data presented by Louis Ray. The Cary snow line is found to have been practically horizontal from Pikes Peak in central Colorado to Cerro Blanco (Sierra Blanca) in southern New Mexico. The altitudinal difference between the snow-line planes, the Cary snowline depression, ranges from 3,000 feet at Pikes Peak to 4,300 feet on Cerro Blanco. Since the temperature lowering probably was slightly greater at Pikes Peak than at Cerro Blanco, the smallest snow-line depression, 3,000 feet at Pikes Peak, is the largest amount referable to lower temperature. Therefore, the mean June-September temperature during the Cary maximum was, at most, 10° F. (5?5 C.) lower in the area. The snowline depressions in excess of 3,000 feet are the minimum lowerings caused by heavier snowfall. Thus the Cary glaciation in New Mexico was a product of both lower temperature and greater snowfall, and the latter increased in importance southward. Lake Estancia and other pluvial lakes in New Mexico and contiguous regions postulated both heavier rainfall and lower temperature. Over Lake Estancia the rainfall can have been 9 inches greater. The exceptional precipitation in November, 1940—October, 1941, demonstrates that an altered and favorable circulation of the atmosphere can produce a greater precipitation in the region during all seasons, even in winter. Therefore, the glaciers and the lakes must have been caused by the same temperature lowering and precipitation increase and may have culminated at the same time, for the lakes did not receive any water from melting glaciers. The pluvial maximum was probably attained slightly earlier than in the Great Basin, where glacial meltwater contributed to most lakes. This dating of the pluvial culmination in New Mexico is new, for I earlier referred it to a late stage of the deglaciation. The revised dating is based mainly on the finding that the Cary glaciation was in part produced by heavier snowfall and on the realization that the abnormal precipitation of November, 1940—October, 1941, might be a sample of the normal one during the glacio-pluvial maximum. At the latitude of Santa Fe, the Cary snow-line depression was 4,000 feet and equaled that of the life- and climatic zones deduced by Charles Stearns from the present and one-time altitudinal distribution of the dusky marmot or western woodchuck. The present semiarid pinon-juniper woodlands and short-grass steppes in New Mexico were then subhumid timberlands and tall-grass prairies.
This is a review of the chronologies based on varved (annually laminated) sediments and a revision of the estimates of the gaps in the varve data. A Finno-Swedish chronology by Gerard De Geer, Ragner Liden, and Matti Sauramo covers the last 11,600 years. It is based on 650 historical years (A.D. 1300-1950), 380 interpolated years (A.D. 920-1300), and the rest on postglacial and glacial varves. The Salpausselka or Younger Dryas age is dated at 10810-10150 B.P. (before the present, 1950). The marked temperature rise which caused the departure of the ice from Salpausselka II in the Finnish year + 1 or 10150 B.P. is taken as the beginning of the Neothermal (European Postglacial) age. The North American chronology ends during the ice oscillations at Cochrane, south of James Bay. These are correlated with the comparably located Nyland and Salpausselka halts in southern Finland. Thus the drainage of Lake Ojibway and varve Timiskaming no. 2025 are dated at about 11300 B.P., and the Cochrane oscillations at 11300-...
This paper gives a brief account of the present material of varve measurements from all over Sweden and vicinity, The first radial lines accomplished, datings were mainly made in marginal directions, although radial lines are at work.
Here is also discussed saltwater softened by outstreaming meltwater, forming different types of symmigt varves, and further on the main moraine extension as in Finland possibly due to a revived ice-center in the N Bothnic region.
Two easterly saltwater influxes arrived just after each enduring morainic stop, Ss I and II, and two westerly, one preliminary in - 1073 B. Z. (B. Z. = Before Zero) and the greater one from -978 on, this latter only through the Närke strait, according to several precise varve determinations.
The drainage of the Baltic ice lake at Mt Billingen is found to be complicated, as the lake for a long time was locked by a broad ice lobe close E of Mt Billingen from -1260, Daltorp, to -1140 B. Z. This is just after the final stage of the Ss II with the entrance of the second marine stage in Finland. The Daltorp lobe mentioned may have left a narrow channel along the steep mountain side, where the seam between ice and rock wall may have permitted a slow leaking out of the lake water for a long time, gradually lowering the lake in concordance with Nilsson's find of a too great divergence between the Baltic and Yoldia shorelines to allow one sudden drainage only. Also Caldenius' measures of varves in the Tidan ice lake show repeated disturbances, which now may be referred to special dated drainings, beginning in -1140 at Billingen, culminating -1077 at Mölltorp, until at last, in -1073, the first saltwater influx could enter through Lake Viken, while the second and far more enduring one entered through the early openings of the Närke strait 95 years later, in -978 B. Z., reviving the symmiet type of clays in Finland, H 2.
Another lake drainage just dated is that of G. Holmsen's ice dammed lakes in the upper Glommen valley (1915). The eatastrophe took place in -522. It deposited at the boundary a vast gravel delta and brought a mega varve of fine silt unto the outlet of River Byälven at the W shore of Lake Vänern at Säffle, VI (p. 307, 323).
Finally is mentioned De Geer's original dating in 1909 within Ragunda of the Zero year at the varve locality Vikbäcken by a mega varve just below the biotic, dark and micro-varved clay, which he then determined to denote the arrival of the Postglacial Period (1910, pp. 3, 4, 1912, p. 251, Pl. 1). That type of clay must have simultaneously begun to be formed at Storedan, after the last mega varve was formed and the ice-lake draining had ceased, all in concordance with a correction of 84 years in the dating of this latter locality.
The Cochrane-Bell moraines in Canada seem, to judge from Antevs' extensive varve counts, to have been of still younger date.
Greenland's ice cover may be a last continuous relict from the big glaciation in a glacial concentration towards the Atlantic, where Greenland has a central situation.
De Geer's system and C 14, by repeated concordance, both prove to be exact and thus supporting each other (GFF 1953, 403, 417).
Historical, botanical, and geological studies in a part of the Coast Mountains of British Columbia show that all the existing glaciers of that area are retreating from climaxes attained in the early part of the eighteenth century and in the middle of the nineteenth century. A rapid rate of shrinkage, amounting to a loss in depth of as much as 12 1/2 feet of ice annually, has prevailed, however, only since the second and third decades of this century and has coincided approximately with a relatively warm period indicated by meteorological records. In three of four glaciers studied, the maximum advance of the last three centuries exceeded any other since the latter part of the Pleistocene epoch, and one of these three glaciers has been as extensive as it was in 1947 for only about four centuries since the deglaciation of its basin by the Cordilleran ice sheet in late Wisconsin time. For a fourth glacier, however, the advances of the past few centuries failed by far to reach the limits of a much earlier, pro...
The Great Basin in the western United States consists of almost level desert basins and alternating parallel mountain ranges. It has sparse, mostly interior, drainage and a few permanent lakes. The climate is arid and semiarid. Fairly large areas are true deserts. The main Cenozoic climatic changes have been: 1. a general cooling during the Tertiary and the early Pleistocene, 2. a progressive drying from the early Miocene into the Pleistocene as a consequence of rise of the Sierra Nevada and the Cascades, and 3. Pleistocene fluctuations between cold-moist and warm-dry ages.
The Ice Age left known records of three or four major glaciations, the last of which had two maxima. The glaciations were relatively extensive on the eastern flank of the Sierra Nevada and just east of the Great Basin, and glaciers existed on several ranges in northeastern Nevada. Each glacial was accompanied by a pluvial, which culminated just after the glacial maximum. The pluvial lakes were largest on Lat. 40°. The histories of the huge lakes Bonneville and Lahontan are incompletely known. During the Mankato-Tioga-Provo'glacio-pluvial maximum the temperature in the Great Basin seems to have been only 2.5–3 C° lower, and the precipitation on the surface of Lake Lahontan (Dendritic Lake) twice as large as now.
The Neothermal (Postglacial, Postpluvial), the equivalent of the interglacials, is with long-distance correlation in view subdivided on the basis of the major temperature changes into the Ana-,.Alti-, and Medithermal ages. However, in the dry country of the Great Basin the changes in moisture are more apparent and important. The Altithermal was distinctly drier than the present, and nearly all the basins went dry. About 2000 B.C. several basins began again to contain lakes which remained permanent through some acute brief droughts. These recentmodern lakes attained very moderate maxima some time before Christ, while the glaciers in the adjacent mountains probably reached their greatest extent since the Anathermal during the last centuries.
New data concerning the uplift in northern North America and in Fennoscandia are combined with earlier findings. The main quantities involved in the hypothesis of postglacial uplift are of the same order of magnitude for Fennoscandia and for the Great Lakes-Hudson Bay regions. Whereas the hypothesis of postglacial uplift is readily accepted for Fennoscandia, it has been rejected in several publications for the present uplift in North America, partly as a consequence of misinterpretation of data. Actually, it offers the best explanation by far for the uplift in both areas.
Abstract in front. Thesis - Harvard, 1948.