Ellensburg Formation Research Articles

Expanding the toolbox for dating basaltic lava sequences: 40 Ar– 39 Ar dating of silicic volcanic glass from interbeds

40 Ar– 39 Ar dating of glass shards from silicic tuffs of the Ellensburg Formation (NW, USA) interbedding basaltic lavas yielded accurate, precise, reproducible plateau and isochron ages that are within error at the 2σ level. The age-spectra have flat plateaus and the inverse isochrons have atmospheric 40 Ar/ 36 Ar at the 2σ level. Ages of 12.00 ± 0.24, 11.37 ± 0.15, 10.67 ± 0.21 and 10.70 ± 0.18 Ma are consistent with the stratigraphy of four of the dated layers; the age of 10.77 ± 0.18 Ma for a fifth layer is at odds with the stratigraphy. This discrepancy arises due to the effect of glass alteration that induced K- and Ar-loss. There is no evidence of excess 40 Ar or 39 Ar recoil. The new ages indirectly constrain the timing of eruption of the lavas above and below the ash beds. This demonstrates that volcanic glass from interbeds can be used as an additional tool for indirectly dating basaltic lava sequences, which is independent of the lavas and complementary to other materials. Considering the numerous studies in which volcanic glass failed to provide reliable 40 Ar– 39 Ar ages, additional and supportive constraints are still needed to assess the validity of the ages from glass shards. Supplementary material : A1 – sample location, stratigraphic position and depositional environments; A2 – electron microprobe information with calibration and sample data; A3 – Ar isotopic data of blanks and samples, data reduction software, J values, criteria for age calculation and images of age spectra and inverse isochrons are available at https://doi.org/10.6084/m9.figshare.c.5077705

A new early occurrence of Cervidae in North America from the Miocene-Pliocene Ellensburg Formation in Washington, USA

A new early occurrence of Cervidae in North America from the Miocene-Pliocene Ellensburg Formation in Washington, USA

A geochemical study of the impact of irrigation and aquifer lithology on groundwater in the Upper Yakima River Basin, Washington, USA

The Yakima River, a major tributary of the Columbia River, is currently overallocated in its surface water usage in part because of large agricultural water use. As a result, groundwater availability and surface water/groundwater interactions have become an important issue in this area. In several sub-basins, the Yakima River water is diverted and applied liberally to fields in the summer creating artificial recharge of shallow groundwater. Major ion, trace element, and stable isotope geochemistry of samples from 26 groundwater wells from a transect across the Yakima River and 24 surface waters in the Kittitas sub-basin were used to delineate waters with similar geochemical signatures and to identify surface water influence on groundwater. Major ion chemistry and stable isotope signatures combined with principal component analysis revealed four major hydrochemical groups. One of these groups, collected from shallow wells within the sedimentary basin fill, displays temporal variations in NO3 and SO4 along with high δ18O and δD values, indicating significant contribution from Yakima River and/or irrigation water. Two other major hydrochemical groups reflect interaction with the main aquifer lithologies in the basin: the Columbia River basalts (high-Na groundwaters), and the volcaniclastic rocks of the Ellensburg Formation (Ca–Mg–HCO3 type waters). The fourth major group has interacted with the volcaniclastic rocks and is influenced to a lesser degree by surface waters. The geochemical groupings constrain a conceptual model for groundwater flow that includes movement of water between underlying Columbia River basalt and deeper sedimentary basin fill and seasonal input of irrigation water.

Sedimentology of proximal to distal volcaniclastics dispersed across an active foldbelt: Ellensburg Formation (late Miocene), central Washington

ABSTRACTLate Miocene volcaniclastics of the Ellensburg Formation (Washington, northwestern USA) are exposed in basins within an integrated palaeodrainage over the depositional reach from 15 to 120 km eastward from a Cascade Range source area. Two facies associations are recognized. The first is composed of laterally restricted, well‐sorted, polymictic conglomerates representing a gravel‐bedload regime during inter‐eruption periods. The second comprises laterally extensive sheets, bounded by deeply‐developed paleosols, composed of monomictic pebbly, pumiceous dacitic sandstones with intercalated debris‐flow and hyperconcentrated flood‐flow deposits. These sheets aggraded in response to eruptive events that are sometimes recorded by air‐fall tephras at the bases of sequences. Debris‐flow and hyperconcentrated flood‐flow deposits occur as far as 120 km from source, but are uncommon beyond 50 km. Hyperconcentrated flood‐flow deposits initially increase in abundance away from source as debris‐flow deposits diminish, suggesting formation of hyperconcentrated flood flows by dilution of debris flows. Sandy facies form broad sheets dominated by scour‐fill bedding, in proximal and medial settings, and grade to narrower, trough cross‐bedded sheets in distal settings, suggesting moderation of flood discharges with distance. Base‐level changes associated with episodic sediment influx caused incision‐aggradation cycles in mainstream settings, and episodic impoundment of tributaries to form lakes or rapidly aggrading, poorly drained floodplains. Although volcanism was the primary control on depositional style, concurrent development of the Yakima fold belt produced a structure‐consequent drainage pattern that determined sediment dispersal, and basin subsidence permitted preservation of both syn‐eruption and inter‐eruption facies. Detritus from rising anticlines was generally diluted by the volumetrically superior extrabasinal volcaniclastics, but dominates deposits of small tributary streams flowing toward, rather than from, the Cascades.

Eruptive style and location of volcanic centers in the Miocene Washington Cascade Range: Reconstruction from the sedimentary record

Primary and reworked pyroclastic material in the Ellensburg Formation of central Washington records middle and late Miocene volcanism in the Cascade Range despite the absence of correlative volcanics within the volcanic chain. Volcanics marking sources for Ellensburg detritus were eroded during late Neogene uplift. Facies patterns and paleocurrent data suggest that the bulk of the volcaniclastics were derived from a source near Bumping Lake; a K-Ar date for an intrusion in this area supports this conclusion. Depositional patterns and characteristics of the detritus allow hypothetical reconstruction of the style of volcanism during this period. Eruptive episodes began with modest-sized Plinian eruptions followed by extended periods of dome growth. Aggradation in adjacent sedimentary basins occurred principally in response to introduction of large volumes of lithic pyroclastic material during eruptive episodes.

Water-Escape Structures in Coarse-Grained, Volcaniclastic, Fluvial Deposits of the Ellensburg Formation, South-Central Washington

ABSTRACT The Miocene Ellensburg Formation of south-central Washington consists largely of volcaniclastic, fluvial sediments deposited on a gentle eastward-sloping surface off the Cascade volcanic belt. The Ellensburg fluvial systems were periodically choked with texturally immature volcanic detritus and were probably characterized by rapid deposition and aggradation. Pillar structures and pocket structures of water-escape origin are generally uncommon in coarse-grained sediments, but are common in conglomeratic deposits of the Ellensburg. Development of water-escape structures in the Ellensburg and in other coarse-grained units is probably dependent on a combination of variables that includes depositional slope, rates of sediment deposition and aggradation, textural maturity, sediment density( ), and regional seismicity.

The Saddle Mountains; the evolution of an anticline in the Yakima fold belt

The Saddle Mountains uplift is an asymmetrical, north vergent anticline with a length of about 110 km. It varies from an open to tight fold and is divided into six segments based upon differences in geometry. Flows of the Columbia River Basalt Group, intercalated sedimentary deposits of the Ellensburg Formation, and suprabasalt sediments thin over the uplift and thicken into the synclines. Variations in thickness are used to determine the timing of deformation and age of major and minor structures. The close correlation of growth rate of the folds with rate of magma supply of the Columbia River Basalt Group suggests that the Yakima fold belt resulted from the same tectonic processes that produced eruption of the Columbia River Basalt.--Modified journal abstract.

A new genus of mustelid from the Ellensburg Formation, Washington

A new genus of mustelid from the Ellensburg Formation, Washington

Graded Lahars in the Type Sections of the Ellensburg Formation, South-Central Washington

The volcaniclastic Miocene-Pliocene Ellensburg Formation west of Yakima contains up to about 15 lahars. These are massive, sheet-like deposits with an average thickness of 2-5 m (6-15 feet). The lahars are characteristically graded, having a thin fine-grained (medium sand) basal layer which abruptly grades into a massive, coarse, poorly sorted central portion that may contain blocks up to 3 m (9 feet) in diameter. This part grades into a bedded or cross-bedded top zone (fine to medium-grained sand, partly pebbly) that may be transitional to horizontally bedded tuffs. Clay- and siltsized fractions form less than 10 percent of all three zones. Heavy minerals, chiefly hornblende, hypersthene and magnetite are abundant in the 125-200mu fraction and may constitute as much as 20 percent of the weight of this fraction. Most lahars are predominantly composed of fragments of a pink to light violet hypersthene-hornblende dacite. The lahars probably originated on the flanks of explosive volcanoes in an ancient Cascade chain at least 60 km (40 miles) to the west. They seem to have moved partly as inertia type flows which would explain the inverse grading: pebbles and blocks moved upward during transport, leaving a layer of medium sand at the base.

Stratigraphy and Petrography of Four Upper Yakima Basalt Flows in South-Central Washington

Field and laboratory investigations of the Yakima Basalt in south-central Washington show that the upper flows consist of four widespread sheets and interbedded sediments. From oldest to youngest, they are: Umatilla Basalt, Selah Member of the Ellensburg Formation, Pomona Basalt, Rattlesnake Ridge Member of the Ellensburg Formation, Elephant Mountain Basalt, and Ward Gap Basalt. Compared with two other local occurrences, the Pomona Basalt is identical with the Selah Butte flow and correlated with it, but is only similar to and probably older than the Huntzinger flow. The basalts are tholeiites and, except for Pomona Basalt, aphyric. During flowage, they were more than 95 percent liquid and crystallization began with olivine, followed by magnetite, plagioclase, and clinopyroxene. Intraflow variations in textures, modes, and mineral composition are determined by the crystallinity, which depends on the cooling history and varies widely within a flow. In general, the flows are glassiest in their interiors, whereas the lower and upper colonnades are hypocrystalline. Glass contents, for example, vary more than 60–70 modal percent within the Elephant Mountain and Umatilla flows. Vertical or lateral variations unrelated to crystallinity were not found. Characteristic structural and petrographic interflow differences, which are present despite internal variations, depend mainly on primary differences in chemical composition. Pomona Basalt is distinguished from the other flows by its magnesium- and calcium-rich composition. Umatilla Basalt differs from the Elephant Mountain flow in having lower total iron, magnesium, and calcium but higher alkalies. Ward Gap Basalt resembles the crystalline Elephant Mountain Basalt. The approximate average thicknesses (in meters), minimum extents (in square kilometers), and volumes (in cubic kilometers) of the four flows are: Umatilla Basalt—45 m, 5180 km 2 , 233 km 3 ; Pamona Basalt—30 m, 18,000 km 2 , 540 km 3 ; Elephant Mountain Basalt—10 m, 10,350 km 2 , 103 km 3 ; and Ward Gap Basalt—10 m, 5120 km 2 , 51 km 3 .

GEOMORPHOLOGY OF SOUTH-CENTRAL WASHINGTON, ILLUSTRATED BY THE YAKIMA EAST QUADRANGLE

Research Article| June 01, 1955 GEOMORPHOLOGY OF SOUTH-CENTRAL WASHINGTON, ILLUSTRATED BY THE YAKIMA EAST QUADRANGLE AARON C WATERS AARON C WATERS THE JOHNS HOPKINS UNIVERSITY, BALTIMORE 18, MARYLAND Search for other works by this author on: GSW Google Scholar Author and Article Information AARON C WATERS THE JOHNS HOPKINS UNIVERSITY, BALTIMORE 18, MARYLAND Publisher: Geological Society of America Received: 05 Apr 1954 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1955, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1955) 66 (6): 663–684. https://doi.org/10.1130/0016-7606(1955)66[663:GOSWIB]2.0.CO;2 Article history Received: 05 Apr 1954 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation AARON C WATERS; GEOMORPHOLOGY OF SOUTH-CENTRAL WASHINGTON, ILLUSTRATED BY THE YAKIMA EAST QUADRANGLE. GSA Bulletin 1955;; 66 (6): 663–684. doi: https://doi.org/10.1130/0016-7606(1955)66[663:GOSWIB]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Geologic mapping of the Yakima district has been neglected since publication of the Ellensburg and Mount Stuart folios (G. O. Smith, 1903a; 1904; see also Calkins, 1905). Reports on other parts of the Columbia River plateau, however, pose new problems and call for revision of some interpretations. This paper presents the results of extending Smith's mapping eastward into the adjacent Yakima East quadrangle, and of considerable reconnaissance work in adjoining areas. The new mapping shows that to the east and south the lower part of the Ellensburg formation interfingers with the Yakima basalt. It also indicates that local diastrophism and volcanism continuously modified and interrupted deposition of the Ellensburg formation.Smith's conclusions that the great topographic ridges are growing anticlines, not fault blocks, and that the major rivers are antecedent to these folds, are confirmed. The anticlines appear to have grown in a single epoch of deformation instead of in two orogenic episodes separated by a period of peneplanation. The “Cascade lowland” is a local pediment formed on the flanks of a growing anticline, not a remnant of a widespread peneplain.The new data do not support Warren's hypothesis of defeat and diversion of Columbia River by rise of the Horse Heaven uplift, nor Flint's hypothesis of the cutting of Wallula Gap by a river thus diverted. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Hornblende and Magnetite Heavies in the Ellensburg of Central Washington

ABSTRACT The mineral assemblage in the Ellensburg formation is unusual in many respects. The heavies are restricted exclusively to hornblende and magnetite. The lights are essentially glass and plagioclase. All of the minerals are remarkably euhedral although evidence points to sources up to 50 miles or more from their present position. The uniform mineral content persists over an area of many hundreds, if not thousands, of square miles and may prove to be an aid in working out the stratigraphy of central Washington.

Resurrected Erosion Surface in Central Washington

Results obtained in mapping the geology of the Wenatchee-Chelan and of the Okanogan district suggest modifications of the earlier interpretations regarding the erosional history: 1) The existence of a “Methow Plain” or “Cascade Peneplain” is questioned. Most of the areas formerly considered to be remnants of this peneplain are surfaces controlled by the structure of the Columbia River basalt flows without regard to a widespread base level of erosion. One remnant, which bevels the Columbia River basalt and the Ellensburg formation on the flanks of an anticline in the Yakima district, is believed to be a pediment of very local extent. 2) The mature surface of the “Entiat stage” is well developed only on resistant granodiorite and gneiss and is exceedingly fragmentary or absent in areas underlain by greenstone, phyllite, schist, and Tertiary sedimentary rocks. It has not been recognized in areas underlain by the Columbia River basalt. The writer interprets nearly all the residuals of the “Entiat surface” described in the literature as resurrected fragments of a widespread late mature erosion surface buried beneath the Miocene Columbia River lavas and associated sediments and then partially exhumed in post-Miocene time. Certain fragmentary remnants of this surface on massive crystalline rocks beyond the limit reached by the basalt flows are believed to have been similarly preserved by burial under andesitic pyroclastics erupted from volcanoes in the Cascade Range.

Land Utilization in the Scablands of Eastern Washington

D TV ECIDED contrasts in land utilization occur on the Columbia Plateau in eastern Washington between the Palouse and the channeled Scablands that interlace in a mystifying manner across the plateau. The area discussed lies within the Big Bend of the Columbia River east to Idaho, south of the Spokane River and north of the Snake River. The bedrock consists of thick basaltic lava flows with a few island hills of crystalline rock, called steptoes by Russell in his Geology and Water Resources of Nez Perce after Steptoe Butte, rising above the lava. Lake beds, called the Ellensburg formation, were deposited on the surface of the lava plateau in the western part of the Columbia Basin. Both the basalt and the lake beds are pervious, and surface streams are, therefore, relatively scarce. A mature topography was developed by the Pleistocene period on the plateau in Washington. Little residual soil was formed from the bedrock. The surface soil was largely of loessial origin and had been heaped into hills, elongated southwest to northeast, by the wind, according to J. Harlen Bretz. During the glacial period a tremendous flood that resulted from the very rapid melting of an ice sheet, poured down across the plateau, which slopes towards the confluence of the Snake and Columbia rivers. This flood devastated the country. It was in places hundreds of feet deep. Divides were overtopped, and vast anastomosing streams washed away the surface soil in their beds and, by plucking out the basalt, excavated numerous deep basins, many of which now form lakes. The bare basalt is locally called scabrock. The intermingled channels formed by flood erosion are called Large bars were deposited by the flood, and the Quincy Basin, in southern Grant County, was largely buried under sand and gravel. The area of the scablands is about 2,800 square miles, with 900 square miles additional buried in debris left by the flood. Figure 1 illustrates the anastomosed character of the scablands. The scablands include numerous smaller channels within the main canyons, pits, buttes, elongated lake basins, mesas, steep cliffs, dry waterfalls, hanging valleys, islands of the original less covered mature relief, isolated columns, and other erosional forms. The erosional and depositional forms are wholly the work of running water. The giant streams are extinct, but the evidence of the flood remains. Before the flood the area was covered with deep, fertile less; after the flood the lower land affected by the catastrophe was barren scabrock, pitted by numerous basins containing ponds and lakes, and covered by debris in many places forming bars and other deposits. Since the epochal formation of the

PROCEEDINGS OF THE SEVENTEENTH ANNUAL MEETING OF THE CORDILLERAN SECTION, HELD AT SAN DIEGO, CALIFORNIA, AUGUST 10, 1916.

Session of August 10 The seventeenth annual meeting of the Cordilleran Section was called to order by the Secretary, in the High School Building, at 2 p. m., in conjunction with that of the Pacific Division of the American Association for the Advancement of Science, August 10, 1916. In the absence of the chairman, Dr. George D. Louderback was elected to the chair. Twenty-five members and visitors were present. All of the papers on the program were presented in order, as follows : AGE OF THE ELLENSBURG FORMATION OF EASTERN OREGON BY DR. J . C. MERRIAM Read in full. Discussion by Mr. Taff, Dr. Louderback, and General Vogdes. SOME INDICATIONS OF CLIMATIC ZONES IN CALIFORNIA DURING LOWER EOCENE TIME BY ROY E. DICKERSON Read in full. RELATIONSHIP OF TERATORNIS TO OTHER REPORTED BIRDS Read in full. RECENT EXTENSION OF THE DISTRIBUTION OF MARINE WOOD BORERS IN SAN PABLO BAY. . .