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• 11. [Article] The fruits and seeds of the Rancho La Brea Pleistocene deposits

  More than 4,000 specimens of fruits and seeds were extracted from the matrix removed from inside the skulls of sabre-tooth cats excavated from various pits in the Rancho La Brea deposits. Of this number, ...

  Citation × Citation Citation Abstract Copy Title: The fruits and seeds of the Rancho La Brea Pleistocene deposits Author: Templeton, Bonnie Carolyn More than 4,000 specimens of fruits and seeds were extracted from the matrix removed from inside the skulls of sabre-tooth cats excavated from various pits in the Rancho La Brea deposits. Of this number, spproximately 1,445 specimens are involved in this study. Many comparisons with modern fruits and seeds made it possible to make identification of this material. There are 15 families comprising 20 genera and 30 species recorded in this report of the Rancho La Brea Pleistocene flora. Of this number, four species and four varieties are new to the Pleistocene floras. Eleven of the 30 species occur in the flora of the area today, eleven now occur in areas so remote from the Rancho La Brea site that they could not have been carried by flood waters into the areas of deposition, and therefore, must have been living near to the asphalt beds in order that entrapment could occur. Eight of the species are now extinct. Based on the requirements of their modern counterparts, ecologically, many of the species live in riparian situations or more moist locations than prevail today in the area of deposition. The average rainfall for the range of a number of the modern representatives of the fossils was correlated. From these data it appears that the climate may have been cooler and more moist during the period of deposition, and the species occurring in southern California at that time would have required 2- to 25 inches for their continued existence. It may be assumed that when this average dropped below 20 inches for long periods of time, the species either receded to areas with suitable rainfall or became extinct. Title: The fruits and seeds of the Rancho La Brea Pleistocene deposits Author: Templeton, Bonnie Carolyn More than 4,000 specimens of fruits and seeds were extracted from the matrix removed from inside the skulls of sabre-tooth cats excavated from various pits in the Rancho La Brea deposits. Of this number, spproximately 1,445 specimens are involved in this study. Many comparisons with modern fruits and seeds made it possible to make identification of this material. There are 15 families comprising 20 genera and 30 species recorded in this report of the Rancho La Brea Pleistocene flora. Of this number, four species and four varieties are new to the Pleistocene floras. Eleven of the 30 species occur in the flora of the area today, eleven now occur in areas so remote from the Rancho La Brea site that they could not have been carried by flood waters into the areas of deposition, and therefore, must have been living near to the asphalt beds in order that entrapment could occur. Eight of the species are now extinct. Based on the requirements of their modern counterparts, ecologically, many of the species live in riparian situations or more moist locations than prevail today in the area of deposition. The average rainfall for the range of a number of the modern representatives of the fossils was correlated. From these data it appears that the climate may have been cooler and more moist during the period of deposition, and the species occurring in southern California at that time would have required 2- to 25 inches for their continued existence. It may be assumed that when this average dropped below 20 inches for long periods of time, the species either receded to areas with suitable rainfall or became extinct. Close

• 12. [Article] Classification of Icelandic watersheds and rivers to explain life history strategies of Atlantic salmon

  A hierarchical classification system of Iceland's watersheds and rivers is presented. The classification is based on Iceland's substrate, climate, water, biota, and human cultural influences. The geological ...

  Citation × Citation Citation Abstract Copy Title: Classification of Icelandic watersheds and rivers to explain life history strategies of Atlantic salmon Author: Gudjonsson, Sigurdur A hierarchical classification system of Iceland's watersheds and rivers is presented. The classification is based on Iceland's substrate, climate, water, biota, and human cultural influences. The geological formations of Iceland are very different in character depending on their age and formation history. Three major types of formations occur: Tertiary, Plio-Pleistocene, and Pleistocene. These formations have different hydrological characters and different landscapes. There are also large differences in the climate within Iceland. Four major river types are found in Iceland: spring-fed rivers in Pleistocene areas, direct runoff rivers in Plio-Pleistocene areas, direct runoff rivers in Tertiary areas and wetland heath rivers in Tertiary areas. Eleven biogeoclimatic regions occur in Iceland, each having a different watershed type. The classification together with life history theory can explain the distributions, abundances, and life history strategies of Icelandic salmonids. Oceanic conditions must also be considered to explain the life history patterns of anadromous populations. When the freshwater and marine habitat is stable, the life history patterns of individuals in a population tend to be uniform, one life history form being most common. In an unstable environment many life history forms occur and the life span of one generation is long. The properties of the habitat can further explain which life history types are present. In the most stable and favorable rivers of Iceland resident life history forms are more common. Such a classification of a river habitat greatly aids the understanding of the habitat and how it enables and constrains the salmonid populations within it. Consequently adaptations in life histories are better understood and conservation, utilization, and management of these valuable natural resources are made more coherent and efficient. Title: Classification of Icelandic watersheds and rivers to explain life history strategies of Atlantic salmon Author: Gudjonsson, Sigurdur A hierarchical classification system of Iceland's watersheds and rivers is presented. The classification is based on Iceland's substrate, climate, water, biota, and human cultural influences. The geological formations of Iceland are very different in character depending on their age and formation history. Three major types of formations occur: Tertiary, Plio-Pleistocene, and Pleistocene. These formations have different hydrological characters and different landscapes. There are also large differences in the climate within Iceland. Four major river types are found in Iceland: spring-fed rivers in Pleistocene areas, direct runoff rivers in Plio-Pleistocene areas, direct runoff rivers in Tertiary areas and wetland heath rivers in Tertiary areas. Eleven biogeoclimatic regions occur in Iceland, each having a different watershed type. The classification together with life history theory can explain the distributions, abundances, and life history strategies of Icelandic salmonids. Oceanic conditions must also be considered to explain the life history patterns of anadromous populations. When the freshwater and marine habitat is stable, the life history patterns of individuals in a population tend to be uniform, one life history form being most common. In an unstable environment many life history forms occur and the life span of one generation is long. The properties of the habitat can further explain which life history types are present. In the most stable and favorable rivers of Iceland resident life history forms are more common. Such a classification of a river habitat greatly aids the understanding of the habitat and how it enables and constrains the salmonid populations within it. Consequently adaptations in life histories are better understood and conservation, utilization, and management of these valuable natural resources are made more coherent and efficient. Close

• 13. [Article] Evaluating the size and extent of paleolakes in central Tibet during the late Pleistocene

  Citation × Citation Citation Abstract Copy Title: Evaluating the size and extent of paleolakes in central Tibet during the late Pleistocene Author: Phillips, Fred, Marrero, Shasta, Kirby, Eric, Shi, Xuhua, Gosse, John, Furlong, Kevin P., Wang, Erchie, Meng, Kai Title: Evaluating the size and extent of paleolakes in central Tibet during the late Pleistocene Author: Phillips, Fred, Marrero, Shasta, Kirby, Eric, Shi, Xuhua, Gosse, John, Furlong, Kevin P., Wang, Erchie, Meng, Kai Close

• 14. [Article] Paleoenvironmental reconstruction of an active margin coast from the Pleistocene to the present : examples from southwestern Oregon

  This study illustrates geoarchaeological and paleoenvironmental approaches to the investigation of an active margin coastal setting and provides examples of how information gleaned through examination ...

  Citation × Citation Citation Abstract Copy Title: Paleoenvironmental reconstruction of an active margin coast from the Pleistocene to the present : examples from southwestern Oregon Author: Punke, Michele Leigh This study illustrates geoarchaeological and paleoenvironmental approaches to the investigation of an active margin coastal setting and provides examples of how information gleaned through examination of the stratigraphic record can reveal depositional signatures that provide insights into the geomorphic and tectonic forces active within coastal river basins. Three case studies from the southern Oregon coast illustrate the complex relationship between tectonics and geomorphic processes along an active margin coast such as Oregon's Cascadia subduction zone. This work illustrates that the differential preservation of late Pleistocene-age terrestrial deposits in Oregon's coastal landscape, and the early cultural sites they may contain, is not random but can be closely related to larger tectonogeomorphic processes operating at local and regional scales. Detailed subsurface investigation of one case study site, the lower Sixes River valley, reveals a complex history of depositional environment evolution in relation to geomorphic and tectonic forces. Litho- and biostratigraphic data sets are used to develop a depositional environment reconstruction for the lower Sixes River site through time. This reconstruction of the depositional environment from the late Pleistocene to the present indicates a transgressive evolution that differs from models of transgressive coastal facies and from other studied Northwest coast estuarine life histories. Factors such as eustatic sea level rise, regional and local tectonic alteration of the landscape, sediment supply, or valley morphology may have played roles in the creation and preservation of this atypical depositional sequence. Litho- and biostratigraphic evidence of six Cascadia subduction zone earthquakes younger than 6200 cal yr BP is recorded in a long sediment core from the Sixes River valley. All six of these events correlate with events previously reported for the area by Kelsey et al. (2002). At least five additional plate boundary earthquakes lowered tidal marshes and freshwater wetlands prior to 6200 cal yr BP. The presence within the lower Sixes River valley of an intertidal environment capable of recording Cascadia subduction zone earthquakes dating to the late Pleistocene and early Holocene has not been found at any other location on the Northwest coast. Title: Paleoenvironmental reconstruction of an active margin coast from the Pleistocene to the present : examples from southwestern Oregon Author: Punke, Michele Leigh This study illustrates geoarchaeological and paleoenvironmental approaches to the investigation of an active margin coastal setting and provides examples of how information gleaned through examination of the stratigraphic record can reveal depositional signatures that provide insights into the geomorphic and tectonic forces active within coastal river basins. Three case studies from the southern Oregon coast illustrate the complex relationship between tectonics and geomorphic processes along an active margin coast such as Oregon's Cascadia subduction zone. This work illustrates that the differential preservation of late Pleistocene-age terrestrial deposits in Oregon's coastal landscape, and the early cultural sites they may contain, is not random but can be closely related to larger tectonogeomorphic processes operating at local and regional scales. Detailed subsurface investigation of one case study site, the lower Sixes River valley, reveals a complex history of depositional environment evolution in relation to geomorphic and tectonic forces. Litho- and biostratigraphic data sets are used to develop a depositional environment reconstruction for the lower Sixes River site through time. This reconstruction of the depositional environment from the late Pleistocene to the present indicates a transgressive evolution that differs from models of transgressive coastal facies and from other studied Northwest coast estuarine life histories. Factors such as eustatic sea level rise, regional and local tectonic alteration of the landscape, sediment supply, or valley morphology may have played roles in the creation and preservation of this atypical depositional sequence. Litho- and biostratigraphic evidence of six Cascadia subduction zone earthquakes younger than 6200 cal yr BP is recorded in a long sediment core from the Sixes River valley. All six of these events correlate with events previously reported for the area by Kelsey et al. (2002). At least five additional plate boundary earthquakes lowered tidal marshes and freshwater wetlands prior to 6200 cal yr BP. The presence within the lower Sixes River valley of an intertidal environment capable of recording Cascadia subduction zone earthquakes dating to the late Pleistocene and early Holocene has not been found at any other location on the Northwest coast. Close

• 15. [Article] Lacustrine micro-fossil assemblage in core NP04-KH3, a Kullenberg piston core from the Moba-Kalya Horst region of Lake Tanganyika, East Africa, as a biogeochemical proxy for Late Pleistocene and Early Holocene climate and lake level changes

  The objective of this research is to determine the correlation of lacustrine micro-fossils in Lake Tanganyika to changes in climate and lake levels during the Late Pleistocene and Early Holocene. Lake ...

  Citation × Citation Citation Abstract Copy Title: Lacustrine micro-fossil assemblage in core NP04-KH3, a Kullenberg piston core from the Moba-Kalya Horst region of Lake Tanganyika, East Africa, as a biogeochemical proxy for Late Pleistocene and Early Holocene climate and lake level changes Author: Steinkamp, Matthew J. The objective of this research is to determine the correlation of lacustrine micro-fossils in Lake Tanganyika to changes in climate and lake levels during the Late Pleistocene and Early Holocene. Lake Tanganyika is the second deepest and one of the oldest lakes in the world. The horst and graben geometry of the lake has created subaqueous structural platforms that accumulate pelagic sediments that contain and archive changes in micro-fossil assemblages controlled by changes in climate and lake levels. One such structural platform is the Moba-Kalya Horst. Micro-fossil analysis of lacustrine sediments from a single Kullenberg piston core from the Moba-Kalya Horst indicate dramatic Late Pleistocene and Early Holocene climate and lake level changes that appear to be synchronized with regional, as well as hemispherical climate shifts. During the Late Pleistocene at the Last Glacial Maximum which ended approximately 15 ky B.P., Lake Tanganyika experienced low-lake stands of 250-350 meters or more below the present lake level. From 17,537 to 15,000 calendar years BP, periphytic diatoms such as Rhopalodia gibberula and Surirella fuellebornii were abundant, as were grass phytoliths and sponge spicules, indicative of a dry climate regime. The dominant planktonic diatom was Stephanodiscus astraea, which thrived in low Si:P supply ratio, stratified lake environments in Na-HCO3 rich waters, indicative of a cool, arid climate regime. Periphytic diatoms were also abundant in Lake Malawi to the south and significantly negative δ180 values were recorded in Greenland ice cores for this period. Following the low-lake stands of the Late Glacial Maximum, lake levels generally rose as East Africa experienced the AHP (African Humid Period) (14.4-5.5 cal ky BP). An increase in planktonic diatoms and decrease in periphytic diatoms were recorded in the lacustrine sediments at this time which indicate a positive water balance and rising lake levels. The accumulation of dark-bundled, laminated sediments indicate that the climate was wet and the coring site was below the annual thermocline. A decrease in S. astraea and increase in Cyclostephanos damasii signal conditions of increased moisture to the lake, and decreased evaporation. Around 13 ky B.P. conditions at Lake Tanganyika reverted to Late Glacial Maximum conditions which lasted until approximately 11.5 ky B.P.. Periphytic diatoms once again became abundant, and sponge spicule and grass phytolith counts rose. S.astraea dominance again rose as lake conditions were calm and stratified and the climate was cool and arid. Periphytic diatoms became abundant in Lake Malawi during this period, and increased negative δ180 values were recorded in the Greenland ice cores correlating with increased periphytic diatoms in both Lake Tanganyika and Lake Malawi. Following the Late Pleistocene cold period, lake levels once again began rising as the climate became wetter and windier. Fluctuations from wet and windy to wet and calm occurred at the terminus of the Late Pleistocene as diatom dominance alternated from Aulacoseira granulata, which indicates wet and windy with increase upwelling, to C.damasii, which indicate wet and stratified. Around 9800 B.P. lake conditions stabilized and remained wet and windy with increase turbulence and upwelling which optimized conditions for the dominance of A.granulata. These conditions prevailed through the Early Holocene to at least 6500 B.P. From the Middle Holocene to the present, the general climate of East Africa was and is more arid than the early Holocene, with dry windy conditions and continued upwelling. Title: Lacustrine micro-fossil assemblage in core NP04-KH3, a Kullenberg piston core from the Moba-Kalya Horst region of Lake Tanganyika, East Africa, as a biogeochemical proxy for Late Pleistocene and Early Holocene climate and lake level changes Author: Steinkamp, Matthew J. The objective of this research is to determine the correlation of lacustrine micro-fossils in Lake Tanganyika to changes in climate and lake levels during the Late Pleistocene and Early Holocene. Lake Tanganyika is the second deepest and one of the oldest lakes in the world. The horst and graben geometry of the lake has created subaqueous structural platforms that accumulate pelagic sediments that contain and archive changes in micro-fossil assemblages controlled by changes in climate and lake levels. One such structural platform is the Moba-Kalya Horst. Micro-fossil analysis of lacustrine sediments from a single Kullenberg piston core from the Moba-Kalya Horst indicate dramatic Late Pleistocene and Early Holocene climate and lake level changes that appear to be synchronized with regional, as well as hemispherical climate shifts. During the Late Pleistocene at the Last Glacial Maximum which ended approximately 15 ky B.P., Lake Tanganyika experienced low-lake stands of 250-350 meters or more below the present lake level. From 17,537 to 15,000 calendar years BP, periphytic diatoms such as Rhopalodia gibberula and Surirella fuellebornii were abundant, as were grass phytoliths and sponge spicules, indicative of a dry climate regime. The dominant planktonic diatom was Stephanodiscus astraea, which thrived in low Si:P supply ratio, stratified lake environments in Na-HCO3 rich waters, indicative of a cool, arid climate regime. Periphytic diatoms were also abundant in Lake Malawi to the south and significantly negative δ180 values were recorded in Greenland ice cores for this period. Following the low-lake stands of the Late Glacial Maximum, lake levels generally rose as East Africa experienced the AHP (African Humid Period) (14.4-5.5 cal ky BP). An increase in planktonic diatoms and decrease in periphytic diatoms were recorded in the lacustrine sediments at this time which indicate a positive water balance and rising lake levels. The accumulation of dark-bundled, laminated sediments indicate that the climate was wet and the coring site was below the annual thermocline. A decrease in S. astraea and increase in Cyclostephanos damasii signal conditions of increased moisture to the lake, and decreased evaporation. Around 13 ky B.P. conditions at Lake Tanganyika reverted to Late Glacial Maximum conditions which lasted until approximately 11.5 ky B.P.. Periphytic diatoms once again became abundant, and sponge spicule and grass phytolith counts rose. S.astraea dominance again rose as lake conditions were calm and stratified and the climate was cool and arid. Periphytic diatoms became abundant in Lake Malawi during this period, and increased negative δ180 values were recorded in the Greenland ice cores correlating with increased periphytic diatoms in both Lake Tanganyika and Lake Malawi. Following the Late Pleistocene cold period, lake levels once again began rising as the climate became wetter and windier. Fluctuations from wet and windy to wet and calm occurred at the terminus of the Late Pleistocene as diatom dominance alternated from Aulacoseira granulata, which indicates wet and windy with increase upwelling, to C.damasii, which indicate wet and stratified. Around 9800 B.P. lake conditions stabilized and remained wet and windy with increase turbulence and upwelling which optimized conditions for the dominance of A.granulata. These conditions prevailed through the Early Holocene to at least 6500 B.P. From the Middle Holocene to the present, the general climate of East Africa was and is more arid than the early Holocene, with dry windy conditions and continued upwelling. Close

• 16. [Article] Geology of the northern part of the Southeast Three Sisters quadrangle, Oregon

  The northern part of the Southeast Three Sisters quadrangle straddles the crest of the central High Cascades of Oregon. The area is covered by Pleistocene and Holocene volcanic and volcaniclastic rocks that ...

  Citation × Citation Citation Abstract Copy Title: Geology of the northern part of the Southeast Three Sisters quadrangle, Oregon Author: Wozniak, Karl C. The northern part of the Southeast Three Sisters quadrangle straddles the crest of the central High Cascades of Oregon. The area is covered by Pleistocene and Holocene volcanic and volcaniclastic rocks that were extruded from a number of composite cones, shield volcanoes, and cinder cones. The principal eruptive centers include Sphinx Butte, The Wife, The Husband, and South Sister volcanoes. Sphinx Butte, The Wife, and The Husband are typical High Cascade shield and composite volcanoes whose compositions are limited to basalt and basaltic andesite. South Sister is a complex composite volcano composed of a diverse assemblage of rocks. In contrast with earlier studies, the present investigation finds that South Sister is not a simple accumulation of andesite and dacite lavas; nor does the eruptive sequence display obvious evolutionary trends or late stage divergence to basalt and rhyolite. Rather, the field relations indicate that magmas of diverse composition have been extruded from South Sister vents throughout the lifespan of this volcano. The compositional variation at South Sister is atypical of the Oregon High Cascade platform. This variation, however, represents part of a continued pattern of late Pliocene and Pleistocene magmatic diversity in a local region that includes Middle Sister, South Sister, and Broken Top volcanoes. Regional and local geologic constraints combined with chemical and petrographic criteria indicate that a local subcrustal process probably produced the magmas extruded from South Sister, whereas a regional subcrustal process probably produced the magmas extruded from Sphinx Butte, The Wife, and The Husband. All of the volcanoes in the field area are probably less than 720,000 years old. Sphinx Butte, The Wife, and The Husband are older than South Sister and have been subjected to at least two glaciations. Late Pleistocene glaciers covered all but the upper ridges and summit of South Sister; however, evidence for multiple glaciation is obscure and it is possible that the bulk of South Sister is younger than the second-to-last Pleistocene glaciation. Glaciated andesite lavas at the summit of South Sister are capped by a veneer of basaltic andesite lavas. The basaltic andesite lavas were extruded prior to 6840 yrs. B.P., but are probably of late Pleistocene rather than Holocene age. At some time between 12,000 and 2300 yrs. B.P., basaltic andesite lavas and cinders were extruded from the Le Conte vent at the southwest base of South Sister. The Le Conte lavas may bear only a spatial relation to South Sister. Between 2300 and 1900 yrs. B.P., a series of rhyodacite domes and block flows were extruded from flank vents on South Sister. Future eruptive activity is likely at this volcano. Title: Geology of the northern part of the Southeast Three Sisters quadrangle, Oregon Author: Wozniak, Karl C. The northern part of the Southeast Three Sisters quadrangle straddles the crest of the central High Cascades of Oregon. The area is covered by Pleistocene and Holocene volcanic and volcaniclastic rocks that were extruded from a number of composite cones, shield volcanoes, and cinder cones. The principal eruptive centers include Sphinx Butte, The Wife, The Husband, and South Sister volcanoes. Sphinx Butte, The Wife, and The Husband are typical High Cascade shield and composite volcanoes whose compositions are limited to basalt and basaltic andesite. South Sister is a complex composite volcano composed of a diverse assemblage of rocks. In contrast with earlier studies, the present investigation finds that South Sister is not a simple accumulation of andesite and dacite lavas; nor does the eruptive sequence display obvious evolutionary trends or late stage divergence to basalt and rhyolite. Rather, the field relations indicate that magmas of diverse composition have been extruded from South Sister vents throughout the lifespan of this volcano. The compositional variation at South Sister is atypical of the Oregon High Cascade platform. This variation, however, represents part of a continued pattern of late Pliocene and Pleistocene magmatic diversity in a local region that includes Middle Sister, South Sister, and Broken Top volcanoes. Regional and local geologic constraints combined with chemical and petrographic criteria indicate that a local subcrustal process probably produced the magmas extruded from South Sister, whereas a regional subcrustal process probably produced the magmas extruded from Sphinx Butte, The Wife, and The Husband. All of the volcanoes in the field area are probably less than 720,000 years old. Sphinx Butte, The Wife, and The Husband are older than South Sister and have been subjected to at least two glaciations. Late Pleistocene glaciers covered all but the upper ridges and summit of South Sister; however, evidence for multiple glaciation is obscure and it is possible that the bulk of South Sister is younger than the second-to-last Pleistocene glaciation. Glaciated andesite lavas at the summit of South Sister are capped by a veneer of basaltic andesite lavas. The basaltic andesite lavas were extruded prior to 6840 yrs. B.P., but are probably of late Pleistocene rather than Holocene age. At some time between 12,000 and 2300 yrs. B.P., basaltic andesite lavas and cinders were extruded from the Le Conte vent at the southwest base of South Sister. The Le Conte lavas may bear only a spatial relation to South Sister. Between 2300 and 1900 yrs. B.P., a series of rhyodacite domes and block flows were extruded from flank vents on South Sister. Future eruptive activity is likely at this volcano. Close

• 17. [Article] Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae)

  Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Published version can be found at American Journal of Botany: http://www.amjbot.o...

  Citation × Citation Citation Abstract Copy Title: Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Author: Liston, Aaron, Kadereit, Joachim W., Coleman, Max, Abbott, Richard J. Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Published version can be found at American Journal of Botany: http://www.amjbot.org/content/vol90/issue10/ Title: Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Author: Liston, Aaron, Kadereit, Joachim W., Coleman, Max, Abbott, Richard J. Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Published version can be found at American Journal of Botany: http://www.amjbot.org/content/vol90/issue10/ Close

• 18. [Article] Preliminary report on the geology of the Molalla quadrangle, Oregon

  The Molalla quadrangle is located in northwestern Oregon along the eastern edge of Willamette Valley about 30 miles south of Portland. The area includes part of the Western Cascade foothills as well as ...

  Citation × Citation Citation Abstract Copy Title: Preliminary report on the geology of the Molalla quadrangle, Oregon Author: Harper, Herbert Ewing The Molalla quadrangle is located in northwestern Oregon along the eastern edge of Willamette Valley about 30 miles south of Portland. The area includes part of the Western Cascade foothills as well as a portion of the Willamette Valley lowland. The rocks in the Cascade foothills are marine and terrestrial sediments interlayered with volcanic flows and pyroclastics which range from Eocene (?) to Pliocene or early Pleistocene in age. The oldest rocks consist of approximately 1500 feet of basaltic and andesitic lavas, present in the southeastern portion of the area, and described here as the Pre-Butte Creek lavas. The base or lower part of the series contains interbedded marine pebble conglomerates presumably of Eocene age. To the southwest the laves are unconformably ever-lain with about 1200 feet of marine and terrestrial sediments which have been termed the Butte Creek beds. Field relations indicate a correlation of these sediments with the Oligocene Illahe sandstone, while the faunal study made by Durham suggests a lower Miocene age. In the southwestern part of the quadrangle the Butte Creek beds are unconformably overlain by the middle Miocene Stayton lavas. Several hundred feet of pyroclastics and terrestrial sediments considered early Pliocene in age and described as the Molalla formation are exposed along Molalla River in the eastern and northeastern part of the quadrangle. They rest unconformably on the Pre-Butte Creek lavas and are overlain by Pliocene or early Pleistocene Boring lavas. Where exposed along the western edge of the Cascade foothills these older formations are covered by middle Pleistocene alluvial deposits which blanket the Willamette valley lowland. All of the Tertiary rocks have been tilted or gently folded. Dips observed in the Butte Creek beds in the southern half of the area average about 6 degrees and indicate an elongate domal fold trending northeasterly. A regional dip of 5 to 8 degrees to the northwest is present in the Molallla formation in the northern part of the area. Minor normal faulting in present locally in the Butte Creek beds. Residual and transported high-alumina clays are present in the Molalla formation. Exploration by the United States Bureau of Mines and Unites States Geological Survey revealed an estimated 53,460,000 wet tons of ore in the Molalla area. Title: Preliminary report on the geology of the Molalla quadrangle, Oregon Author: Harper, Herbert Ewing The Molalla quadrangle is located in northwestern Oregon along the eastern edge of Willamette Valley about 30 miles south of Portland. The area includes part of the Western Cascade foothills as well as a portion of the Willamette Valley lowland. The rocks in the Cascade foothills are marine and terrestrial sediments interlayered with volcanic flows and pyroclastics which range from Eocene (?) to Pliocene or early Pleistocene in age. The oldest rocks consist of approximately 1500 feet of basaltic and andesitic lavas, present in the southeastern portion of the area, and described here as the Pre-Butte Creek lavas. The base or lower part of the series contains interbedded marine pebble conglomerates presumably of Eocene age. To the southwest the laves are unconformably ever-lain with about 1200 feet of marine and terrestrial sediments which have been termed the Butte Creek beds. Field relations indicate a correlation of these sediments with the Oligocene Illahe sandstone, while the faunal study made by Durham suggests a lower Miocene age. In the southwestern part of the quadrangle the Butte Creek beds are unconformably overlain by the middle Miocene Stayton lavas. Several hundred feet of pyroclastics and terrestrial sediments considered early Pliocene in age and described as the Molalla formation are exposed along Molalla River in the eastern and northeastern part of the quadrangle. They rest unconformably on the Pre-Butte Creek lavas and are overlain by Pliocene or early Pleistocene Boring lavas. Where exposed along the western edge of the Cascade foothills these older formations are covered by middle Pleistocene alluvial deposits which blanket the Willamette valley lowland. All of the Tertiary rocks have been tilted or gently folded. Dips observed in the Butte Creek beds in the southern half of the area average about 6 degrees and indicate an elongate domal fold trending northeasterly. A regional dip of 5 to 8 degrees to the northwest is present in the Molallla formation in the northern part of the area. Minor normal faulting in present locally in the Butte Creek beds. Residual and transported high-alumina clays are present in the Molalla formation. Exploration by the United States Bureau of Mines and Unites States Geological Survey revealed an estimated 53,460,000 wet tons of ore in the Molalla area. Close

• 19. [Article] Origin and configuration of the present-day land surface, Goodhue County, Minnesota

  This study describes the surface configuration of Goodhue County and attempts to determine the origin of that configuration. The research has a descriptive portion--an objective examination of land surface ...

  Citation × Citation Citation Abstract Copy Title: Origin and configuration of the present-day land surface, Goodhue County, Minnesota Author: Sansome, Constance J. (Constance Jefferson) This study describes the surface configuration of Goodhue County and attempts to determine the origin of that configuration. The research has a descriptive portion--an objective examination of land surface configuration and the composition and distribution of rock material underlying that surface, and a theoretical portion--a speculative examination of the factors controlling the land surface configuration and discussion of the probable origin of that configuration. I found that the configuration of any land surface is described in terms of drainage and topography and that the origin and age of any land surface is determined by an examination of the materials making up that surface, the present and past processes acting on that surface, and the amount of time available for the processes to act. I also found that the age of land surface configuration is distinct from the age of the underlying materials and that the degree to which configuration of any land surface is dependent on structure, process, and time is dependent on the scale of the investigation and the surface itself. The surface of Goodhue County ranges in elevation from approximately 670 feet to 1275 feet. The southern two-thirds of the county is a broad upland; the northern third of the county is slightly lower and more dissected. The county has a dendritic and well-integrated drainage system and is underlain by virtually flat-lying sedimentary rocks and thick deposits of glacial drift. The surface configuration of Goodhue County is the result of: (1) geographic location near the center of North America and alongside its major river; (2) marine deposition during the early Paleozoic; (3) minor folding and faulting during the later Paleozoic; (4) extensive solution and erosion during the late Paleozoic and/or parts of the Mesozoic; (5) fluvial deposition during the Cretaceous; (6) glacial and glaciofluvial deposition during the early and middle Pleistocene; (7) aeolian deposition and mass movement late in the Pleistocene; and (8) fluvial erosion and deposition during the late Pleistocene and Recent. Title: Origin and configuration of the present-day land surface, Goodhue County, Minnesota Author: Sansome, Constance J. (Constance Jefferson) This study describes the surface configuration of Goodhue County and attempts to determine the origin of that configuration. The research has a descriptive portion--an objective examination of land surface configuration and the composition and distribution of rock material underlying that surface, and a theoretical portion--a speculative examination of the factors controlling the land surface configuration and discussion of the probable origin of that configuration. I found that the configuration of any land surface is described in terms of drainage and topography and that the origin and age of any land surface is determined by an examination of the materials making up that surface, the present and past processes acting on that surface, and the amount of time available for the processes to act. I also found that the age of land surface configuration is distinct from the age of the underlying materials and that the degree to which configuration of any land surface is dependent on structure, process, and time is dependent on the scale of the investigation and the surface itself. The surface of Goodhue County ranges in elevation from approximately 670 feet to 1275 feet. The southern two-thirds of the county is a broad upland; the northern third of the county is slightly lower and more dissected. The county has a dendritic and well-integrated drainage system and is underlain by virtually flat-lying sedimentary rocks and thick deposits of glacial drift. The surface configuration of Goodhue County is the result of: (1) geographic location near the center of North America and alongside its major river; (2) marine deposition during the early Paleozoic; (3) minor folding and faulting during the later Paleozoic; (4) extensive solution and erosion during the late Paleozoic and/or parts of the Mesozoic; (5) fluvial deposition during the Cretaceous; (6) glacial and glaciofluvial deposition during the early and middle Pleistocene; (7) aeolian deposition and mass movement late in the Pleistocene; and (8) fluvial erosion and deposition during the late Pleistocene and Recent. Close

• 20. [Article] Quaternary tectonics of the Rincon and San Miguelito oil fields area, western Ventura basin, California

  The Ventura basin is an elongate sedimentary trough extending from the San Gabriel fault west into the Santa Barbara Channel. West of Ventura it contains over 4 km of severely deformed Pliocene and Pleistocene ...

  Citation × Citation Citation Abstract Copy Title: Quaternary tectonics of the Rincon and San Miguelito oil fields area, western Ventura basin, California Author: Grigsby, F. Bryan The Ventura basin is an elongate sedimentary trough extending from the San Gabriel fault west into the Santa Barbara Channel. West of Ventura it contains over 4 km of severely deformed Pliocene and Pleistocene clastic strata. The north-dipping Red Mountain reverse fault system, which forms the northern boundary of the basin, has been active since the early Pliocene and has maximum reverse separation of 7300 m (23,900 ft). In the basin, the Grubb and Oak Grove faults were active in the early Pleistocene and were reactivated during late Pleistocene folding. Both are tear faults that dip steeply northeast and strike northwest, in contrast to the west-trending structural grain of the region. The Rincon anticline is the western extension of the Ventura Avenue anticline. Both anticlines formed approximately 200,000 years ago as rootless folds which die out in subjacent fine-grained Miocene strata. Above the Rincon anticline synchronous shortening occurred on the Javon Canyon/Padre Juan fault and San Miguelito anticline. The Padre Juan fault is a south-dipping reverse fault that flattens over the axis of the Rincon anticline and dies out to the north. Where it flattens, the Javon Canyon fault rises upwards and offsets 3500 year old marine terrace deposits at the surface. Maximum reverse separation across the Javon Canyon/Padre Juan fault is 2800 m (9200 ft). The steeply north-dipping to overfolded region between the Javon Canyon and Padre Juan faults constitutes a large portion of the north limb of the San Miguelito anticline. This anticline, constrained above the Padre Juan fault, is a complex example of a fault-propagation fold. Total shortening in the Ventura basin along a cross-section through the study area is approximately 7825 m (25,700 ft). For the last 200,000 years this north-south directed shortening has occurred at a rate of 12.5 to 22.3 mm/yr (0.49 to 0.87 in/yr). These values compare favorably with shortening values obtained at other locations in the basin, and support the concept of decreasing horizontal contraction from east to west across the basin for the last 200,000 years. Title: Quaternary tectonics of the Rincon and San Miguelito oil fields area, western Ventura basin, California Author: Grigsby, F. Bryan The Ventura basin is an elongate sedimentary trough extending from the San Gabriel fault west into the Santa Barbara Channel. West of Ventura it contains over 4 km of severely deformed Pliocene and Pleistocene clastic strata. The north-dipping Red Mountain reverse fault system, which forms the northern boundary of the basin, has been active since the early Pliocene and has maximum reverse separation of 7300 m (23,900 ft). In the basin, the Grubb and Oak Grove faults were active in the early Pleistocene and were reactivated during late Pleistocene folding. Both are tear faults that dip steeply northeast and strike northwest, in contrast to the west-trending structural grain of the region. The Rincon anticline is the western extension of the Ventura Avenue anticline. Both anticlines formed approximately 200,000 years ago as rootless folds which die out in subjacent fine-grained Miocene strata. Above the Rincon anticline synchronous shortening occurred on the Javon Canyon/Padre Juan fault and San Miguelito anticline. The Padre Juan fault is a south-dipping reverse fault that flattens over the axis of the Rincon anticline and dies out to the north. Where it flattens, the Javon Canyon fault rises upwards and offsets 3500 year old marine terrace deposits at the surface. Maximum reverse separation across the Javon Canyon/Padre Juan fault is 2800 m (9200 ft). The steeply north-dipping to overfolded region between the Javon Canyon and Padre Juan faults constitutes a large portion of the north limb of the San Miguelito anticline. This anticline, constrained above the Padre Juan fault, is a complex example of a fault-propagation fold. Total shortening in the Ventura basin along a cross-section through the study area is approximately 7825 m (25,700 ft). For the last 200,000 years this north-south directed shortening has occurred at a rate of 12.5 to 22.3 mm/yr (0.49 to 0.87 in/yr). These values compare favorably with shortening values obtained at other locations in the basin, and support the concept of decreasing horizontal contraction from east to west across the basin for the last 200,000 years. Close