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R. J. Munroe

Publications and source records attributed to R. J. Munroe.

17 recordsLinked to original sources
USGS2012

Heat flow and thermotectonic problems of the central Ventura Basin, southern California

The Ventura Basin, southern California, is located near the Big Bend area of the San Andreas fault system, within the Transverse Ranges physiographic province. Continuous equilibrium temperature logs were measured in 12 idle oil wells located within the onshore Ventura Avenue, San Miguelito, Filmore, Oxnard, and West Montalvo fields to an average depth of about 3100 m (10,200 feet). Thermal conductivities were measured on all available samples. Heat flows were calculated with the aid of a thermostratigraphic scheme based on correlative gradient intervals and average thermal conductivity for the appropriate units. Negative curvature of the Ventura Avenue temperature profiles may be explained by an increase in thermal conductivity associated with tectonic compaction of the underlying Pliocene clastic sequence. Temperature profiles at Fillmore are enigmatic but suggest highly unusual geotectonic conditions. Basinwide, heat flow averages about 48 mW/m 2 , a value which is low relative to most of southern California. As heat flow does not vary systematically to the maximum measured depth of about 4 km, this anomaly is not easily explained in terms of hydrologic effects or recent uplift and erosion. However, a diminution of heat flow is an expectable consequence of the accumulation of cold sediments (up to 12 km) since Eocene time. If 70 mW/m 2 is accepted as the background heat flow, then the sedimentation effect is probably sufficient to explain the anomaly.

Journal of Geophysical Research Solid Earth↗
USGS1985

A heat-flow reconnaissance of southeastern Alaska

Heat flow was measured at nine sites in crystalline and sedimentary rocks of southeastern Alaska. Seven of the sites, located between 115 and 155 km landward of the Queen Charlotte – Fairweather transform fault, have an average heat flow of 59 ± 6 mW m −2 . This value is significantly higher than the mean of 42 mW m −2 in the coastal provinces between Cape Mendocino and the Queen Charlotte Islands, to the south, and is lower than the mean of 72 ± 2 mW m −2 for 81 values within 100 km of the San Andreas transform fault, even farther south. This intermediate value suggests the absence of significant heat sinks associated with Cenozoic subduction and of heat sources related to either late Cenozoic tectono-magmatic events or significant shear-strain heating. At Warm Springs Bay, 75 km from the plate boundary, an anomalously high heat flow of 150 mW m −2 can most plausibly be ascribed to the thermal spring activity from which its name is derived. At Quartz Hill, 240 km landward of the plate boundary, a value of 115 mW m −2 might indicate a transition to a province of high heat flow resulting from late Tertiary and Quaternary extension and volcanism.

Alaska↗
USGS1984

Thermal conductivity determinations on solid rock - a comparison between a steady-state divided-bar apparatus and a commercial transient line-source device

Two apparatuses were used to measure thermal conductivities on pairs of contiguous samples from 17 specimens of solid rock: the USGS divided-bar apparatus, a steadystate comparative method, and the Shotherm "Quick Thermal Meter" (QTM), which employs a transient strip heat source. Both devices were calibrated relative to fused silica. Both devices have a reproducibility of ??5% or better depending, to some extent, on the physical nature of the specimen being tested. For solid rocks, specimen preparation for the divided bar is much more tedious and expensive than for the QTM, which seems insensitive to minor surface roughness. The QTM does, however, require quite large specimens (30 mm ?? 60 mm ?? 100 mm as a minimum for rocks) with even larger specimens (50 mm ?? 100 mm ?? 100 mm) required for higher conductivity material (3.5 W m-1 K-1 and greater). Experimental times are comparable; however, the QTM is a self-contained unit that can be transported easily and set up quickly and requires no more space than a standard desk top. From a formal statistical comparison, it appears that, over a large range of conductivities (1.4 to ???5 W m-1 K-1) and rock types, the two instruments will yield the same value of thermal conductivity for isotropic rocks. ?? 1984.

Journal of Volcanology and Geothermal Research↗
USGS1976

Heat-flow data from southeastern Oregon

With the exception of values from two holes drilled within 2 km of Mickey Hot Springs, 17 new heat-flow values in southeastern Oregon are within or somewhat below the range one would normally expect in non-anomalous parts of the North American Cordillera. This is not surprising for a region in which most igneous rocks on the surface are 5 m.y. old or more. There is a suggestion of a thermal anomaly associated with the very young (late Pleistocene or Holocene) Diamond Craters lava field, and the thermal regime on both sides of Steens Mountain seems to be controlled, to some degree, by lateral and vertical movement of water.

Oregon↗
USGS1974

Heat flow from eastern Panama and northwestern Colombia

Heat flows were determined at 12 sites in four distinct areas between longitude 77° and 80°W in eastern Panama and northwestern Colombia. Evidently, most of the region is underlain by mafic oceanic crust so that the crustal radiogenic component of heat flow is very small (∼ 0.1 μcal cm −2 sec −1 ). Low heat-flow values (∼ 0.7 μcal cm −2 sec −1 ) in northwestern Colombia may reflect thermal transients associated with shallow subduction. The normal values (∼ 1) at about 78°W are consistent with the mean heat flow from the western Caribbean and the Gulf of Mexico. At 80°W, a fairly high value of 1.8 may define the easterly limit of thermal transients due to Cenozoic volcanic activity in Central America.

Earth and Planetary Science Letters↗
USGS1968

Measurement of geothermal flux through poorly consolidated sediments

In many regions, crystalline rocks are covered by hundreds of meters of unconsolidated and poorly consolidated sediments. Estimates of heat flux within these sediments using standard continental techniques (temperature and conductivity measurements at intervals of 10 to 30 meters) are unreliable, mainly because of the difficulty in obtaining and preserving representative lengths of core. However, it is sometimes feasible to use what amounts to an oceanographic technique by making closely spaced temperature and conductivity measurements within short cored intervals. This is demonstrated in a borehole at Menlo Park, California (37°27′N, 122°10′W, elevation 16 meters), where heat flows determined over 12 separate 1-meter intervls al lie within 10% of their mean value; 2.2 μcal/cm 2 sec.

California↗