Four box cores and one piston core show that Holocene sedimentation on the southern Canada Abyssal Plain for the last 8010 ± 120 yr has consisted of a continuing rain of pelagic organic and ice-rafted clastic sediment with a net accumulation rate during the late Holocene of ⩽10 mm/1000 yr, and episodically emplaced turbidites 1–5 m thick deposited at intervals of 830 to 3450 yr (average 2000 yr). The average net accumulation rate of the mixed sequence of turbidites and thin pelagite interbeds in the cores is about 1.2 m/1000 yr.
Physiography suggests that the turbidites originated on the Mackenzie Delta or its clinoform, and δ13C values of −27 to −25%. in the turbidites are compatible with a provenance on a delta. Extant displaced neritic and lower slope to basin plain calcareous benthic foraminifers coexist in the turbidite units. Their joint occurence indicates that the turbidites originated on the modern continental shelf and entrained sediment from the slope and rise enroute to their final resting place on the Canada Abyssal Plain. The presence of Middle Pleistocene diatoms in the turbidites suggests, in addition, that the turbidites may have originated in shallow submarine slides beneath the upper slope or outer shelf. Small but consistent differences in organic carbon content and δ13C values between the turbidite units suggest that they did not share an identical provenance, which is at least compatible with an origin in slope failures.
The primary provenance of the ice-rafted component of the pelagic beds was the glaciated terrane of northwestern Canada; and the provenance of the turbidite units was Pleistocene and Holocene sedimentary deposits on the outer continental shelf and upper slope of the Mackenzie Delta. Largely local derivation of the sediment of the Canada Abyssal Plain indicates that sediment accumulation rates in the Arctic Ocean are valid only for regions with similar depositional sources and processes, and that these rates cannot be extrapolated regionally. The location of an elliptical zone of active seismicity over the inferred provenance of the turbidites suggests that they were triggered by large earthquakes.
Distal turbidite sediment accumulation rates were more than two orders of magnitude greater than pelagic sediment accumulation rates on the Canada Abyssal Plain during the last 8000 years. This disparity reconciles the discrepancy between the high accumulation rates assumed by some for the Arctic Ocean because of the numerous major rivers and large ice sheets that discharge into this small mediterranean basin and the low pelagic sedimentation rates that have been reported from the Arctic Ocean.
The slug test is one of the most commonly used field methods for obtaining in situ estimates of hydraulic conductivity. Despite its prevalence, this method has received criticism from many quarters in the ground-water community. This criticism emphasizes the poor quality of the estimated parameters, a condition that is primarily a product of the somewhat casual approach that is often employed in slug tests. Recently, the Kansas Geological Survey (KGS) has pursued research directed at improving methods for the performance and analysis of slug tests. Based on extensive theoretical and field research, a series of guidelines have been proposed that should enable the quality of parameter estimates to be improved. The most significant of these guidelines are: (1) three or more slug tests should be performed at each well during a given test period; (2) two or more different initial displacements (H0) should be used at each well during a test period; (3) the method used to initiate a test should enable the slug to be introduced in a near-instantaneous manner and should allow a good estimate of Ho to be obtained; (4) data-acquisition equipment that enables a large quantity of high quality data to be collected should be employed; (5) if an estimate of the storage parameter is needed, an observation well other than the test well should be employed; (6) the method chosen for analysis of the slug-test data should be appropriate for site conditions; (7) use of pre-and post-analysis plots should be an integral component of the analysis procedure, and (8) appropriate well construction parameters should be employed. Data from slug tests performed at a number of KGS field sites demonstrate the importance of these guidelines.
Many state agencies are currently (1995) developing wellhead protection programs. The thrust of some of these programs is to protect water supplies by determining the areas contributing recharge to water-supply wells and by specifying regulations to minimize the opportunity for contamination of the recharge water by activities at the land surface. The area contributing recharge to a discharging well is the surface area at the water table through which the water flowing to the well entered the ground-water system. In the analyses of ground-water flow systems, steady-state average conditions are commonly used to simplify the problem and make a solution tractable. However, recharge is usually cyclic in nature, with seasonal cycles and longer term climatic cycles. The effect of these cyclic stresses on the area contributing recharge to wells is quantitatively analyzed for a hypothetical alluvial valley aquifer system that is representative of a large class of ground-water systems that are extensively developed for water supply. The analysis shows that, in many cases, these cyclic changes in the recharge rates do not significantly affect the location and size of the areas contributing recharge to wells. The ratio of the mean travel time to the length of the cyclic stress period appears to be an indicator of whether the transient effects of the cyclic stress must be explicitly represented in the analysis of contributing areas to wells. For the cases examined, if the ratio of the mean travel time to the period of the cyclic stress was much greater than one, then the transient area contributing recharge to wells was similar to the area calculated using an average steady-state condition. However, cyclic stresses on systems with ratios less than one do have an effect on the location and size of the areas contributing recharge to wells.
A new technique, using empirical relationships between median grain size and density and velocity to calculate proxy values for density and velocity, avoids many of the problems associated with the use of well logs and shipboard measurements to construct synthetic seismograms. This method was used to groundtruth and correlate across both analog and digital shallow high-resolution seismic data on the New Jersey shelf. Sampling dry vibracores to determine median grain size eliminates the detrimental effects that coring disturbances and preservation variables have on the sediment and water content of the core. The link between seismic response to lithology and bed spacing is more exact. The exact frequency of the field seismic data can be realistically simulated by a 10-20 cm sampling interval of the vibracores. The estimate of the percentage error inherent in this technique, 12% for acoustic impedance and 24% for reflection amplitude, is calculated to one standard deviation and is within a reasonable limit for such a procedure. The synthetic seismograms of two cores, 4-6 m long, were used to correlate specific sedimentary deposits to specific seismic reflection responses. Because this technique is applicable to unconsolidated sediments, it is ideal for upper Pleistocene and Holocene strata.
Improved images of the internal structure of Early Cretaceous North Atlantic crust reveal both probable detachment faults and more steeply dipping normal faults. The detachment faults occur as subhorizontal structures passing ∼ 1.5 km beneath fault blocks without offset; several steeper block-bounding faults appear to detach onto these structures. However, the detachments are bounded to the west (ridgeward) by presumably younger, more steeply west-dipping normal faults. In one possible interpretation, the detachment and the steep faults belong to the same “rolling-hinge” extension system. An intriguing alternative is that a phase of detachment faulting, perhaps related to increased magmatic activity, was succeeded by localized amagmatic extension along steeper and more deeply penetrating faults.
One of the major problems in hydrogeologic investigations of glaciated regions is the determination of complex stratigraphic relationships in the subsurface where insufficient information is available from drilling and geophysical records. In this paper, chemical characteristics of groundwater were used to identify stratigraphic changes in glacial deposits that were previously inferred on Block Island, Rhode Island, USA, an emergent remnant of the late Wisconsinan terminal moraine, located approximately 16 km south of the Rhode Island mainland. Two chemically distinct water types are recognized on the island: 1) high-iron, characterized by dissolved silica levels in excess of 20 mg/L, bicarbonate greater than 30 mg/L and dissolved iron ranging from 1-20 mg/L; and 2) low-iron, characterized by dissolved silica levels below 16 mg/L, bicarbonate less than 30 mg/L, and less than 0.3 mg/L dissolved iron. The spatial distribution of iron-bearing minerals and organic matter and the resulting redox conditions are believed to control the occurrence of highiron groundwater. The high-iron waters occur almost exclusively in the eastern half of the island and appear to coincide with the presence of allochthonous blocks of Cretaceous-age coastal-plain sediments that were incorporated into Pleistocene-age deposits derived from the Narragansett Bay-Buzzard's Bay lobe of the Late Wisconsinan Laurentide ice sheet. The low-iron waters occur in the western half of the island, where the occurrence of these Cretaceous-age blocks is rare and the sediments are attributed to a sublobe of the Hudson-Champlain lobe of the Late Wisconsinan ice sheet.
","language":"English","publisher":"Springer","doi":"10.1007/s100400050093","usgsCitation":"Veeger, A., and Stone, B., 1996, Using hydrogeochemical methods to evaluate complex quaternary subsurface stratigraphy Block Island, Rhode Island, USA: Hydrogeology Journal, v. 4, no. 4, p. 69-82, https://doi.org/10.1007/s100400050093.","productDescription":"14 p.","startPage":"69","endPage":"82","numberOfPages":"14","costCenters":[{"id":40020,"text":"Florence Bascom Geoscience Center","active":true,"usgs":true}],"links":[{"id":488745,"rank":1,"type":{"id":41,"text":"Open Access External Repository Page"},"url":"https://digitalcommons.uri.edu/geo_facpubs/178","text":"External Repository"},{"id":228484,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"country":"United States","state":"Rhode Island","otherGeospatial":"Block Island","geographicExtents":"{\n \"type\": \"FeatureCollection\",\n \"features\": [\n {\n \"type\": \"Feature\",\n \"properties\": {},\n \"geometry\": {\n \"type\": \"Polygon\",\n \"coordinates\": [\n [\n [\n -71.61918640136719,\n 41.14531119462475\n ],\n [\n -71.54090881347656,\n 41.14531119462475\n ],\n [\n -71.54090881347656,\n 41.233800286547435\n ],\n [\n -71.61918640136719,\n 41.233800286547435\n ],\n [\n -71.61918640136719,\n 41.14531119462475\n ]\n ]\n ]\n }\n }\n ]\n}","volume":"4","issue":"4","noUsgsAuthors":false,"publicationDate":"2012-11-20","publicationStatus":"PW","scienceBaseUri":"505bc05ee4b08c986b32a0ad","contributors":{"authors":[{"text":"Veeger, A.I.","contributorId":100031,"corporation":false,"usgs":true,"family":"Veeger","given":"A.I.","email":"","affiliations":[],"preferred":false,"id":377485,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Stone, B. D. 0000-0001-6092-0798","orcid":"https://orcid.org/0000-0001-6092-0798","contributorId":50919,"corporation":false,"usgs":true,"family":"Stone","given":"B. D.","affiliations":[],"preferred":false,"id":377484,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70018163,"text":"70018163 - 1996 - The initial cooling of pahoehoe flow lobes","interactions":[],"lastModifiedDate":"2023-11-08T01:39:31.090094","indexId":"70018163","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1109,"text":"Bulletin of Volcanology","active":true,"publicationSubtype":{"id":10}},"title":"The initial cooling of pahoehoe flow lobes","docAbstract":"In this paper we describe a new thermal model for the initial cooling of pahoehoe lava flows. The accurate modeling of this initial cooling is important for understanding the formation of the distinctive surface textures on pahoehoe lava flows as well as being the first step in modeling such key pahoehoe emplacement processes as lava flow inflation and lava tube formation. This model is constructed from the physical phenomena observed to control the initial cooling of pahoehoe flows and is not an empirical fit to field data. We find that the only significant processes are (a) heat loss by thermal radiation, (b) heat loss by atmospheric convection, (c) heat transport within the flow by conduction with temperature and porosity-dependent thermal properties, and (d) the release of latent heat during crystallization. The numerical model is better able to reproduce field measurements made in Hawai'i between 1989 and 1993 than other published thermal models. By adjusting one parameter at a time, the effect of each of the input parameters on the cooling rate was determined. We show that: (a) the surfaces of porous flows cool more quickly than the surfaces of dense flows, (b) the surface cooling is very sensitive to the efficiency of atmospheric convective cooling, and (c) changes in the glass forming tendency of the lava may have observable petrographic and thermal signatures. These model results provide a quantitative explanation for the recently observed relationship between the surface cooling rate of pahoehoe lobes and the porosity of those lobes (Jones 1992, 1993). The predicted sensitivity of cooling to atmospheric convection suggests a simple field experiment for verification, and the model provides a tool to begin studies of the dynamic crystallization of real lavas. Future versions of the model can also be made applicable to extraterrestrial, submarine, silicic, and pyroclastic flows.","language":"English","publisher":"Springer","doi":"10.1007/s004450050121","issn":"02588900","usgsCitation":"Keszthelyi, L., and Denlinger, R., 1996, The initial cooling of pahoehoe flow lobes: Bulletin of Volcanology, v. 58, no. 1, p. 5-18, https://doi.org/10.1007/s004450050121.","productDescription":"14 p.","startPage":"5","endPage":"18","costCenters":[{"id":615,"text":"Volcano Hazards Program","active":true,"usgs":true}],"links":[{"id":227454,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"58","issue":"1","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505bad45e4b08c986b323ad6","contributors":{"authors":[{"text":"Keszthelyi, L.","contributorId":42691,"corporation":false,"usgs":true,"family":"Keszthelyi","given":"L.","affiliations":[],"preferred":false,"id":378733,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Denlinger, R.","contributorId":47925,"corporation":false,"usgs":true,"family":"Denlinger","given":"R.","email":"","affiliations":[],"preferred":false,"id":378734,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70018155,"text":"70018155 - 1996 - Shallow ground-water quality beneath a major urban center: Denver, Colorado, USA","interactions":[],"lastModifiedDate":"2017-04-14T09:14:43","indexId":"70018155","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2342,"text":"Journal of Hydrology","active":true,"publicationSubtype":{"id":10}},"title":"Shallow ground-water quality beneath a major urban center: Denver, Colorado, USA","docAbstract":"A survey of the chemical quality of ground water in the unconsolidated alluvial aquifer beneath a major urban center (Denver, Colorado, USA) was performed in 1993 with the objective of characterizing the quality of shallow ground-water in the urban area and relating water quality to land use. Thirty randomly selected alluvial wells were each sampled once for a broad range of dissolved constituents. The urban land use at each well site was sub- classified into one of three land-use settings: residential, commercial, and industrial. Shallow ground-water quality was highly variable in the urban area and the variability could be related to these land-use setting classifications. Sulfate (SO4) was the predominant anion in most samples from the residential and commercial land-use settings, whereas bicarbonate (HCO3) was the predominant anion in samples from the industrial land-use setting, indicating a possible shift in redox conditions associated with land use. Only three of 30 samples had nitrate concentrations that exceeded the US national drinking-water standard of 10 mg l-1 as nitrogen, indicating that nitrate contamination of shallow ground water may not be a serious problem in this urban area. However, the highest median nitrate concentration (4.2 mg l-1) was in samples from the residential setting, where fertilizer application is assumed to be most intense. Twenty-seven of 30 samples had detectable pesticides and nine of 82 analyzed pesticide compounds were detected at low concentrations, indicating that pesticides are widely distributed in shallow ground water in this urban area. Although the highest median total pesticide concentration (0.17 ??g l-1) was in the commercial setting, the herbicides prometon and atrazine were found in each land-use setting. Similarly, 25 of 29 samples analyzed had detectable volatile organic compounds (VOCs) indicating these compounds are also widely distributed in this urban area. The total VOC concentrations in sampled wells ranged from nondetectable to 23 442 ??g l-1. Widespread detections and occasionally high concentrations point to VOCs as the major anthropogenic ground-water impact in this urban environment. Generally, the highest VOC concentrations occurred in samples from the industrial setting. The most frequently detected VOC was the gasoline additive methyl tertbutyl ether (MTBE, in 23 of 29 wells). Results from this study indicate that the quality of shallow ground water in major urban areas can be related to land-use settings. Moreover, some VOCs and pesticides may be widely distributed at low concentrations in shallow ground water throughout major urban areas. As a result, the differentiation between point and non-point sources for these compounds in urban areas may be difficult.","language":"English","publisher":"Elsevier","doi":"10.1016/S0022-1694(96)03031-4","issn":"00221694","usgsCitation":"Bruce, B.W., and McMahon, P., 1996, Shallow ground-water quality beneath a major urban center: Denver, Colorado, USA: Journal of Hydrology, v. 186, no. 1-4, p. 129-151, https://doi.org/10.1016/S0022-1694(96)03031-4.","productDescription":"23 p.","startPage":"129","endPage":"151","numberOfPages":"23","costCenters":[],"links":[{"id":227323,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"186","issue":"1-4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505b8e27e4b08c986b318771","contributors":{"authors":[{"text":"Bruce, B. W.","contributorId":19577,"corporation":false,"usgs":true,"family":"Bruce","given":"B.","email":"","middleInitial":"W.","affiliations":[],"preferred":false,"id":378707,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"McMahon, P.B. 0000-0001-7452-2379","orcid":"https://orcid.org/0000-0001-7452-2379","contributorId":10762,"corporation":false,"usgs":true,"family":"McMahon","given":"P.B.","affiliations":[],"preferred":false,"id":378706,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70018153,"text":"70018153 - 1996 - Aquifer Response to Record Low Barometric Pressures in the Southeastern United States","interactions":[],"lastModifiedDate":"2024-03-08T13:09:45.683593","indexId":"70018153","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":3825,"text":"Groundwater","active":true,"publicationSubtype":{"id":10}},"title":"Aquifer Response to Record Low Barometric Pressures in the Southeastern United States","docAbstract":"A late-winter cyclone classified as one of the most intense of the 20th century moved across the Southeastern states of Georgia and South Carolina and onto the Northeast during March 12–14, 1993. Record low barometric pressures were recorded in Augusta, Georgia (28.93 inches of mercury) and Columbia, South Carolina (28.63 inches of mercury) on March 13, 1993, and pressures returned to normal values (near 30 inches of mercury) within one day following these record lows. This relatively unusual event provided an opportunity to examine the attendant water-level response in continuously monitored ground-water wells in regional Atlantic Coastal Plain, Piedmont, and Blue Ridge aquifers in the Southeast. Water levels in all wells examined responded inversely to the short duration, extreme drop in barometric pressure. Barometric efficiencies (Δground-water level/Δbarometric-pressure level) calculated were dependent on depth to screened- or open-interval midpoint (highest correlation coefficient, r2= 0.89) and, to a lesser extent, total thickness of confining material above the aquifer tapped (highest r2= 0.65). Wells in crystalline-rock aquifers had a correlation with depth to open-interval midpoint (r2= 0.89) similar to the sedimentary aquifers examined. The magnitude of barometric efficiency was also strongly related to a well's increased distance from aquifer outcrop areas in the Cretaceous aquifers in South Carolina (r2= 0.95) and the upper Brunswick aquifer in Georgia (r2= 0.90), because these aquifers are more deeply buried toward the coast. This relation between barometric efficiency, well depth, and extent of confinement suggests that barometric efficiency determinations can provide useful information to hydrologists concerned with examining an aquifer's degree of confinement and corresponding isolation from land surface, particularly when the aquifer is used as a source for public supply.
A hybrid global search algorithm is used to solve the nonlinear problem of calculating slip amplitude, rake, risetime, and rupture time on a finite fault. Thirty-five strong motion velocity records are inverted by this method over the frequency band from 0.1 to 1.0 Hz for the Northridge earthquake. Four regions of larger-amplitude slip are identified: one near the hypocenter at a depth of 17 km, a second west of the hypocenter at about the same depth, a third updip from the hypocenter at a depth of 10 km, and a fourth updip from the hypocenter and to the northwest. The results further show an initial fast rupture with a velocity of 2.8 to 3.0 km/s followed by a slow termination of the rupture with velocities of 2.0 to 2.5 km/s. The initial energetic rupture phase lasts for 3 s, extending out 10 km from the hypocenter. Slip near the hypocenter has a short risetime of 0.5 s, which increases to 1.5 s for the major slip areas removed from the hypocentral region. The energetic rupture phase is also shown to be the primary source of high-frequency radiation (1–15 Hz) by an inversion of acceleration envelopes. The same global search algorithm is used in the envelope inversion to calculate high-frequency radiation intensity on the fault and rupture time. The rupture timing from the low- and high-frequency inversions is similar, indicating that the high frequencies are produced primarily at the mainshock rupture front. Two major sources of high-frequency radiation are identified within the energetic rupture phase, one at the hypocenter and another deep source to the west of the hypocenter. The source at the hypocenter is associated with the initiation of rupture and the breaking of a high-stress-drop asperity and the second is associated with stopping of the rupture in a westerly direction.
","language":"English","publisher":"American Geophysical Union","doi":"10.1029/96JB01883","issn":"01480227","usgsCitation":"Hartzell, S., Liu, P., and Mendoza, C., 1996, The 1994 Northridge, California, earthquake: Investigation of rupture velocity, risetime, and high-frequency radiation: Journal of Geophysical Research B: Solid Earth, v. 101, no. 9, p. 20091-20108, https://doi.org/10.1029/96JB01883.","productDescription":"18 p.","startPage":"20091","endPage":"20108","numberOfPages":"18","costCenters":[],"links":[{"id":227277,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"101","issue":"9","noUsgsAuthors":false,"publicationDate":"1996-09-10","publicationStatus":"PW","scienceBaseUri":"505ba634e4b08c986b320f76","contributors":{"authors":[{"text":"Hartzell, S.","contributorId":12603,"corporation":false,"usgs":true,"family":"Hartzell","given":"S.","email":"","affiliations":[],"preferred":false,"id":378700,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Liu, P.","contributorId":98443,"corporation":false,"usgs":true,"family":"Liu","given":"P.","email":"","affiliations":[],"preferred":false,"id":378702,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Mendoza, C.","contributorId":82059,"corporation":false,"usgs":true,"family":"Mendoza","given":"C.","email":"","affiliations":[],"preferred":false,"id":378701,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70018140,"text":"70018140 - 1996 - Ferromanganese crusts as indicators for paleoceanographic events in the NE Atlantic","interactions":[],"lastModifiedDate":"2023-11-16T16:43:15.931183","indexId":"70018140","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1795,"text":"Geologische Rundschau","active":true,"publicationSubtype":{"id":10}},"title":"Ferromanganese crusts as indicators for paleoceanographic events in the NE Atlantic","docAbstract":"Hydrogenetic ferromanganese crusts reflect the chemical conditions of the sewater from which they formed. Fine-scale geochemical analysis of crust layers in combination with age determinations can therefore be used to investigate paleoceanographic changes which are recorded in geochemical gradients in the crusts. At Tropic seamount (off northwest Africa), uniform crust growth influenced by terrigenous input from the African continent occurred during approximately the past 12 Ma. Phosphatization of these crusts is minor. In contrast, crusts from Lion seamount, located between Madeira and the Portuguese coast, display a much more variable growth history. A pronounced increase in Ni, Cu, and Zn is observed in some intervals of the crusts, which probably reflects increased surface productivity. A thick older phosphatized generation occurs in many samples. Hydrographic profiles indicate that Mediterranean outflow water (MOW) may play an important role in the composition of these crusts.10Be dating of one sample confirms that the interruption of the MOW during the Messinian salinity crisis (6.2–5 Ma ago) resulted in changes in element composition. Sr-isotope dating of the apatite phase of the old crust generation has been carried out to obtain a minimum age for the older generation of Atlantic crusts and to determine whether crust phosphatization in the Atlantic can be related to phosphatization episodes recorded in Pacific crusts. The preliminary data show that the old phosphatized crust generation might be as old as approximately 30–40 Ma.
","language":"English","publisher":"Springer","doi":"10.1007/BF02369011","usgsCitation":"Koschinsky, A., Halbach, P., Hein, J., and Mangini, A., 1996, Ferromanganese crusts as indicators for paleoceanographic events in the NE Atlantic: Geologische Rundschau, v. 85, no. 3, p. 567-576, https://doi.org/10.1007/BF02369011.","productDescription":"10 p.","startPage":"567","endPage":"576","numberOfPages":"10","costCenters":[],"links":[{"id":227054,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg"}],"otherGeospatial":"Northeast Atlantic","geographicExtents":"{\n \"type\": \"FeatureCollection\",\n \"features\": [\n {\n \"type\": \"Feature\",\n \"properties\": {},\n \"geometry\": {\n \"coordinates\": [\n [\n [\n -30.25,\n 40\n ],\n [\n -30.25,\n 18\n ],\n [\n -1,\n 18\n ],\n [\n -1,\n 40\n ],\n [\n -30.25,\n 40\n ]\n ]\n ],\n \"type\": \"Polygon\"\n }\n }\n ]\n}","volume":"85","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a0f86e4b0c8380cd5392e","contributors":{"authors":[{"text":"Koschinsky, A.","contributorId":42724,"corporation":false,"usgs":true,"family":"Koschinsky","given":"A.","affiliations":[],"preferred":false,"id":378665,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Halbach, P.","contributorId":101396,"corporation":false,"usgs":true,"family":"Halbach","given":"P.","affiliations":[],"preferred":false,"id":378667,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Hein, J.R. 0000-0002-5321-899X","orcid":"https://orcid.org/0000-0002-5321-899X","contributorId":61429,"corporation":false,"usgs":true,"family":"Hein","given":"J.R.","affiliations":[],"preferred":false,"id":378666,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Mangini, A.","contributorId":22101,"corporation":false,"usgs":true,"family":"Mangini","given":"A.","email":"","affiliations":[],"preferred":false,"id":378664,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70018125,"text":"70018125 - 1996 - Clay alteration and gold deposition in the genesis and blue star deposits, Eureka County, Nevada","interactions":[],"lastModifiedDate":"2024-01-03T16:15:48.886432","indexId":"70018125","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1472,"text":"Economic Geology","active":true,"publicationSubtype":{"id":10}},"title":"Clay alteration and gold deposition in the genesis and blue star deposits, Eureka County, Nevada","docAbstract":"The Genesis and Blue Star sedimentary rock-hosted gold deposits occur within the 40-mile-long Carlin trend and are located in Eureka County, Nevada. The deposits are hosted within the Devonian calcareous Popovieh Formation, the siliciclastic Rodeo Creek unit and the siliciclastic Vinini Formation. The host rocks have undergone contact metamorphism, decalcification, silicification, argillization, and supergene oxidation.Detailed characterization of the alteration patterns, mineralogy, modes of occurrence, and associated geochemistry of clay minerals resulted in the following classifications: least altered rocks, found distal to the orebody, consisting of both metamorphosed and unmetamorphosed host rock that has not been completely decalcified; and altered rocks, found proximal to the orebody that have been decalcified. Altered rocks are classified further into the following groups based on clay mineral content: silicic, 1 to 10 percent clay; silicic-argillic, 10 to 35 percent clay; and argillic, 35 to 80 percent clay. Clay species identified are 1M illite, 2M 1 illite, kaolinite, halloysite, and dioctahedral smectite. An early hydrothermal event resulted in the precipitation of euhedral kaolinite and at least one generation of silica. This event occurred contemporaneously with decalcification which increased rock permeability and porosity. A second clay alteration event resulted in the precipitation of hydrothermal 1M illite which replaced hydrothermal kaolinite and is associated with gold deposition. Silver and silica deposition is also associated with this phase of hydrothermal alteration. Hydrothermal alteration was followed by supergene alteration which resulted in the formation of supergene kaolinite, halloysite, and smectite as well as the oxidation of iron-bearing minerals. Supergene clays are concentrated along faults, dike margins, and within rocks containing carbonate. Gold mineralization is not associated with supergene clay minerals within the Genesis and Blue Star deposits. Rocks classified as silicic-argillic in the Popovich Formation represent the most significant gold host. Silicic-argillic rocks commonly exhibit bedding-parallel alteration zones. This pattern of alteration indicates that stratigraphy as well as northwest-trending structures played a significant role in the migration of gold-bearing fluids. Based on K-Ar age determinations of hydrothermal 1M illite associated with gold, the main event of mineralization in the Genesis and Blue Star deposits occurred between 93 and 100 Ma, during mid-Cretaceous time.
","language":"English","publisher":"Society of Economic Geologists","doi":"10.2113/gsecongeo.91.8.1383","issn":"03610128","usgsCitation":"Drews-Armitage, S.P., Romberger, S., and Whitney, C., 1996, Clay alteration and gold deposition in the genesis and blue star deposits, Eureka County, Nevada: Economic Geology, v. 91, no. 8, p. 1383-1393, https://doi.org/10.2113/gsecongeo.91.8.1383.","productDescription":"11 p.","startPage":"1383","endPage":"1393","numberOfPages":"11","costCenters":[],"links":[{"id":227450,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"91","issue":"8","noUsgsAuthors":false,"publicationDate":"1996-12-01","publicationStatus":"PW","scienceBaseUri":"5059f637e4b0c8380cd4c60e","contributors":{"authors":[{"text":"Drews-Armitage, S. P.","contributorId":7022,"corporation":false,"usgs":true,"family":"Drews-Armitage","given":"S.","email":"","middleInitial":"P.","affiliations":[],"preferred":false,"id":378590,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Romberger, S.B.","contributorId":24114,"corporation":false,"usgs":true,"family":"Romberger","given":"S.B.","affiliations":[],"preferred":false,"id":378591,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Whitney, C.G.","contributorId":86361,"corporation":false,"usgs":true,"family":"Whitney","given":"C.G.","email":"","affiliations":[],"preferred":false,"id":378592,"contributorType":{"id":1,"text":"Authors"},"rank":3}]}} ,{"id":70018124,"text":"70018124 - 1996 - Jellyfish Lake, Palau: Regeneration of C, N, Si, and P in anoxic marine lake sediments","interactions":[],"lastModifiedDate":"2012-03-12T17:19:27","indexId":"70018124","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2620,"text":"Limnology and Oceanography","active":true,"publicationSubtype":{"id":10}},"title":"Jellyfish Lake, Palau: Regeneration of C, N, Si, and P in anoxic marine lake sediments","docAbstract":"Sediment cores from Jellyfish Lake were processed under an inert atmosphere and the pore waters extracted and analyzed for the following parameters: pH, titration alkalinity (TA), Cl-, H4SiO4, PO43-, NH4+, Ca2-, Mg2+, SO42-, and H2S. Additionally, in one set of pore-water samples (core 10), the ??13C of the ??CO2 was also determined. The TA, H4SiO4, PO43-, NH4+, and H2S increased with depth in the pore waters above anoxic bottom-water values. H2S values increased to 3.8 ??M. In one case, both H4SiO4 and PO43- concentrations increased to a maximum value and then decreased with depth, suggesting removal into solid phases. The H4SiO4 concentrations are equal to or greater than pore-water values observed in sediments underlying upwelling areas. PO43- concentrations are, in general, lower than pore-water values from terrigenous nearshore areas but higher than nearshore carbonate pore-water values from Florida Bay or Bermuda. The Ca2+, Cl-, and Mg2+: Cl- ratios show slight decreases in the top 15-20 cm, suggesting that authigenic carbonate may be forming. This suggestion is supported by the fact that the pore waters are saturated with respect to CaCO3 due to the very high TAs. The ??13C measurements of the pore-water ??CO2 are from a shorter core. These measurements reach their most negative concentration at 72 cm and then become slightly heavier. This change is accompanied by a decrease in TA, suggesting the onset of methanogenesis at this location in this core.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Limnology and Oceanography","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","issn":"00243590","usgsCitation":"Lyons, W., Lent, R., Burnett, W.C., Chin, P., Landing, W., Orem, W., and McArthur, J., 1996, Jellyfish Lake, Palau: Regeneration of C, N, Si, and P in anoxic marine lake sediments: Limnology and Oceanography, v. 41, no. 7, p. 1394-1403.","startPage":"1394","endPage":"1403","numberOfPages":"10","costCenters":[],"links":[{"id":227405,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"41","issue":"7","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505a3feee4b0c8380cd6492e","contributors":{"authors":[{"text":"Lyons, W.B.","contributorId":71319,"corporation":false,"usgs":true,"family":"Lyons","given":"W.B.","email":"","affiliations":[],"preferred":false,"id":378585,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Lent, R.M.","contributorId":80317,"corporation":false,"usgs":true,"family":"Lent","given":"R.M.","email":"","affiliations":[],"preferred":false,"id":378586,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Burnett, W. C.","contributorId":39779,"corporation":false,"usgs":false,"family":"Burnett","given":"W.","email":"","middleInitial":"C.","affiliations":[],"preferred":false,"id":378584,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Chin, P.","contributorId":9787,"corporation":false,"usgs":true,"family":"Chin","given":"P.","email":"","affiliations":[],"preferred":false,"id":378583,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Landing, W.M.","contributorId":99303,"corporation":false,"usgs":true,"family":"Landing","given":"W.M.","email":"","affiliations":[],"preferred":false,"id":378588,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Orem, W. H. 0000-0003-4990-0539","orcid":"https://orcid.org/0000-0003-4990-0539","contributorId":93084,"corporation":false,"usgs":true,"family":"Orem","given":"W. H.","affiliations":[],"preferred":false,"id":378587,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"McArthur, J.M.","contributorId":101826,"corporation":false,"usgs":true,"family":"McArthur","given":"J.M.","email":"","affiliations":[],"preferred":false,"id":378589,"contributorType":{"id":1,"text":"Authors"},"rank":7}]}} ,{"id":70018123,"text":"70018123 - 1996 - Contrasts between Sm-Nd whole-rock and U-Pb zircon systematics in the Tobacco Root batholith, Montana: Implications for the determination of crustal age provinces","interactions":[],"lastModifiedDate":"2025-08-15T15:19:05.224822","indexId":"70018123","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":3525,"text":"Tectonophysics","active":true,"publicationSubtype":{"id":10}},"title":"Contrasts between Sm-Nd whole-rock and U-Pb zircon systematics in the Tobacco Root batholith, Montana: Implications for the determination of crustal age provinces","docAbstract":"Proper documentation of the extent and age of crust in the western US is critical for constraining a variety of geologic problems ranging from the growth rate of continents to Precambrian continental reconstructions. The secondary isotopic systematics of granitoids have been one of the principal means used to characterize continental crust in areas where the basement is covered. In southwestern Montana and eastern Idaho a group of Late Mesozoic to Cenozoic, dioritic to quartz monzonitic batholiths (e.g., Tobacco Root, Idaho, Pioneer, Boulder, etc.) share a limited range of Paleoproterozoic Sm-Nd depleted mantle model ages. The Tobacco Root batholith (TRB) has a Nd isotopic composition (ϵNd = −17.9 to −19.1) and SmNd model age (TDM = 1.63 to 1.90 Ga) typical of this group. The TRB, however, intruded Archean crust (∼3.3 Ga, ϵNd = ∼ −35), rather than the presumed Proterozoic crust intruded by the other plutons. The Archean heritage of the TRB is confirmed by the presence of premagmatic zircons which range from 2.2 to 3.0 Ga. The combination of U-Pb zircon and Nd model ages suggest that the batholith was derived from both Archean and Proterozoic crustal sources, as well as an ∼80 Ma mantle component. This contrasts with a sample from the northern Idaho batholith which exhibits concordancy between its Sm-Nd and premagmatic zircon systems at ∼1.74 Ga. These data point to the difficulties that can occur if crustal age provinces are defined solely on the basis of Nd model ages of younger plutons, particularly in areas such as the northwestern US where Archean and Proterozoic crust is poorly exposed and dispersed over a large area.
","language":"English","publisher":"Elsevier","doi":"10.1016/S0040-1951(96)00151-5","issn":"00401951","usgsCitation":"Mueller, P., Heatherington, A., D’Arcy, K.A., Wooden, J.L., and Nutman, A., 1996, Contrasts between Sm-Nd whole-rock and U-Pb zircon systematics in the Tobacco Root batholith, Montana: Implications for the determination of crustal age provinces: Tectonophysics, v. 265, no. 1-2, p. 169-179, https://doi.org/10.1016/S0040-1951(96)00151-5.","productDescription":"11 p.","startPage":"169","endPage":"179","costCenters":[],"links":[{"id":227404,"rank":1,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"country":"United States","state":"Idaho, Montana, Wyoming","geographicExtents":"{\n \"type\": \"FeatureCollection\",\n \"features\": [\n {\n \"type\": \"Feature\",\n \"properties\": {},\n \"geometry\": {\n \"coordinates\": [\n [\n [\n -115.06377085731225,\n 46.66227149504411\n ],\n [\n -115.06377085731225,\n 44.077720147519585\n ],\n [\n -110.28647031561087,\n 44.077720147519585\n ],\n [\n -110.28647031561087,\n 46.66227149504411\n ],\n [\n -115.06377085731225,\n 46.66227149504411\n ]\n ]\n ],\n \"type\": \"Polygon\"\n }\n }\n ]\n}","volume":"265","issue":"1-2","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059fa7de4b0c8380cd4db1a","contributors":{"authors":[{"text":"Mueller, P.A.","contributorId":86117,"corporation":false,"usgs":true,"family":"Mueller","given":"P.A.","email":"","affiliations":[],"preferred":false,"id":378582,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Heatherington, A.L.","contributorId":75708,"corporation":false,"usgs":true,"family":"Heatherington","given":"A.L.","affiliations":[],"preferred":false,"id":378581,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"D’Arcy, K. A.","contributorId":71707,"corporation":false,"usgs":true,"family":"D’Arcy","given":"K.","email":"","middleInitial":"A.","affiliations":[],"preferred":false,"id":378580,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Wooden, J. L.","contributorId":58678,"corporation":false,"usgs":true,"family":"Wooden","given":"J.","email":"","middleInitial":"L.","affiliations":[],"preferred":false,"id":378579,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Nutman, A.P.","contributorId":16177,"corporation":false,"usgs":true,"family":"Nutman","given":"A.P.","affiliations":[],"preferred":false,"id":378578,"contributorType":{"id":1,"text":"Authors"},"rank":5}]}} ,{"id":70018115,"text":"70018115 - 1996 - Middle Proterozoic age for the Montpelier Anorthosite, Goochland terrane, eastern Piedmont, Virginia","interactions":[],"lastModifiedDate":"2023-12-23T15:02:55.895239","indexId":"70018115","displayToPublicDate":"1996-01-01T00:00:00","publicationYear":"1996","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1786,"text":"Geological Society of America Bulletin","active":true,"publicationSubtype":{"id":10}},"title":"Middle Proterozoic age for the Montpelier Anorthosite, Goochland terrane, eastern Piedmont, Virginia","docAbstract":"Uranium-lead dating of zircons from the Montpelier Anorthosite confirms previous interpretations, based on equivocal evidence, that the Goochland terrane in the eastern Piedmont of Virginia contains Grenvillian basement rocks of Middle Proterozoic age. A very few prismatic, elongate, euhedral zircons, which contain 12–29 ppm uranium, are interpreted to be igneous in origin. The vast majority of zircons are more equant, subangular to anhedral, contain 38–52 ppm uranium, and are interpreted to be metamorphic in origin. One fraction of elongate zircon, and four fragments of a very large zircon (occurring in a nelsonite segregation) yield an upper intercept age of 1045 ± 10 Ma, interpreted as the time of anorthosite crystallization. Irregularly shaped metamorphic zircons are dated at 1011 ± 2 Ma (weighted average of the 207Pb/206Pb ages). The U-Pb isotopic systematics of metamorphic titanite were reset during the Alleghanian orogeny at 297 ± 5 Ma. These data provide a minimum age for gneisses of the Goochland terrane that are intruded by the anorthosite. Middle Proterozoic basement rocks of the Goochland terrane may be correlative with those in the Shenandoah massif of the Blue Ridge tectonic province, as suggested by similarities between the Montpelier Anorthosite and the Roseland anorthosite. Although the areal extent of Middle Proterozoic basement and basement-cover relations in the eastern Piedmont remain unresolved, results of this investigation indicate that the Goochland terrane is an internal massif of Laurentian crust rather than an exotic accreted terrane.
The results of a field experiment comparing water-quality constituents, specific conductance, geophysical measurements, and well-bore hydraulics in two long-screen wells and adjacent vertical clusters of short-screen wells show bias in ground-water data caused by well-bore flow in long-screen wells. The well screen acts as a conduit for vertical flow because it connects zones of different head and transmissivity, even in a relatively homogeneous, unconfined, sand and gravel aquifer where such zones are almost indistinguishable. Flow in the well bore redistributes water and solutes in the aquifer adjacent to the well, increasing the risk of bias in water-quality samples, failure of plume detection, and cross-contamination of the aquifer. At one site, downward flow from a contaminated zone redistributes solutes over the entire length of the long-screen well. At another site, upward flow from an uncontaminated zone masks the presence of a road salt plume.
Borehole induction logs, conducted in a fully penetrating short-screen well, can provide a profile of solutes in the aquifer that is not attainable in long-screen wells. In this study, the induction-log profiles show close correlation with data from analyses of water-quality samples from the short-screen wells; however, both of these data sets differ markedly from the biased water-quality samples from the long-screen wells. Therefore, use of induction logs in fully cased wells for plume detection and accurate placement of short-screen wells is a viable alternative to use of long screen wells for water-quality sampling.
Field and laboratory evidence shows that deeply buried (90–888 m) fine-grained sediments of the Atlantic Coastal Plain contain viable acetogenic microorganisms, and that these microorganisms actively produce organic acids. Concentrations of formate, acetate, and propionate in pore waters extracted from fine-grained sediments ranged from 50 μM to 5 mM and were much higher than in adjacent pore waters associated with sandy sediments (<2 μM). Laboratory studies showed that asceptically cored fine-grained sediments incubated under a H2 atmosphere produced formate and acetate, and that H14CO3− was converted to 14C-acetate and 14C-formate over time. An enrichment culture of these acetogenic microorganisms was recovered from one long-term incubation that showed the presence of several morphologically distinct gram-positive, rod-shaped bacteria. These microorganisms were capable of growth under autotrophic (H2 + CO2), heterotrophic (syringate), and mixotrophic (H2 + CO2 + syringate) conditions. These results suggest that microbial acetogenesis, rather than abiotic processes, is the most important organic acid-producing mechanism during low-temperature (∼ 30 °C) diagenesis of Atlantic Coastal Plain sediments.
Strata of Westphalian D age on the western coast of the Sydney Basin expose a fossil forest of approximately 30 lepidodendrid trees within one of several clastic splits of the Harbour Seam. A multidisciplinary approach was employed to interpret the origins of the coat bed, the depositional history of the site and the response of the fossil forest to changing edaphic conditions. The megaspore and miospore records indicate that the mire vegetation was dominated by arboreous lycopsids, especially Paralycopodites, with subdominant tree ferns. Petrographic, palynological and geochemical evidence suggest that the Harbour coal bed at Table Head originated as a rheotrophic (cf. planar) mire (eutric histosol). The mire forest is interpreted to have been engulfed by prograding distributary-channel sediments; sparse protist assemblages are suggestive of a freshwater delta-plain lake environment occasionally in contact with brackish waters. Lepidodendrids persisted as site colonizers of clastic substrates even after burial of the rheotrophic peatland and influenced the morphology of deposited sediment, but apparently were unable to colonize distributary channels. Equivocal taxonomic data (compression fossils) show the fossil forest to have been composed of both monocarpic (Lepidodendron) and polycarpic (Diaphorodendron, Paralycopodites, ?Sigillaria) lycopsids, genera recorded in the palynology of the uppermost ply of the underlying coal bed. Comparatively rare within the clastic beds of the fossil forest, however, is the stem compression of Paralycopodites, whose dispersed megapores and miospores dominate the underlying coal bed. Tree diameter data recorded equivalent to breast height indicate a forest of mixed age. These data would appear to suggest that some lepidodendrids employing a polycarpic reproductive strategy were better able to cross the ecological barrier imposed between peat and clastic substrates. Foliar compressions indicate that an understory or stand of Psaronius type tree ferns co-existed with the lepidodendrids on clastic substrates, which developed as incipient gleysol soils. The entombment of the forest can be ascribed to its distributary coastal setting, local subsidence and a seasonal climate that fostered wildfire and increased sedimentation.
The systematics of the fossil bee nest ichnogenus Uruguay from the Uruguayan Cretaceous or lower Tertiary is reviewed and two new ichnospecies of a new ichnogenus, Rosellichnus, are proposed for fossil bee nests from the Miocene of the United Arab Emirates and Patagonian Argentina. Uruguay contains U. auroranormae(the ich‐notype) and U. rivasi, which differs from the type ichnospecies in having clustered cells arranged in three rows, with one central and two marginal rows of subparallel cells. No bee nest architecture known to us unequivocally fits with any ichnospecies described herein. Uruguay was constructed in the subsoil and may be of halictid origin; however, its large cell size, thick cell walls, and the presence of a vestibular cell do not fit the architecture of nests of extant halictids. Rosellichnus arabicus lacks the complete cavity surrounding the cell cluster that is typical in nests of Old World halictids, but it may, nonetheless, still be of halictid origin. R. pa‐tagonicus has an architecture more similar to nests of anthophorine bees than to those of Neotropical Halictidae. Therefore, the ichnogenus Rosellichnus may include both halictid and anthophorine constructions. Although the smooth inner cell walls, spiral cell caps, and clustering of cells indicate that both Uruguay and Rosellichnus are trace fossils of bee origin, it is likely that both represent nest architectures that are no longer employed by extant bees, or those that are as yet unknown. The paleoenvironments of both the Argentine and Emirates species of Rosellichnus indicate that the trace‐makers of this ichnogenus constructed their nests in open ground sandy soils.
","language":"English","publisher":"Taylor & Francis","doi":"10.1080/10420949609380127","usgsCitation":"Genise, J.F., and Bown, T.M., 1996, Uruguay Roselli 1938 and Rosellichnus, N. Ichnogenus: Two ichnogenera for clusters of fossil bee cells: Ichnos: An International Journal for Plant and Animal Traces, v. 4, no. 3, p. 199-217, https://doi.org/10.1080/10420949609380127.","productDescription":"19 p.","startPage":"199","endPage":"217","costCenters":[],"links":[{"id":228746,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"country":"Argentina, United Arab Emirates","volume":"4","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"505bbe4ae4b08c986b3294e7","contributors":{"authors":[{"text":"Genise, Jorge F.","contributorId":107450,"corporation":false,"usgs":false,"family":"Genise","given":"Jorge","email":"","middleInitial":"F.","affiliations":[],"preferred":false,"id":378426,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Bown, Thomas M.","contributorId":67081,"corporation":false,"usgs":true,"family":"Bown","given":"Thomas","email":"","middleInitial":"M.","affiliations":[],"preferred":false,"id":378425,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ]}