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Karl S. Kellogg

Publications and source records attributed to Karl S. Kellogg.

At least 55 records · Page 3Linked to original sources
USGS1992

Chapter 4: Cretaceous thrusting and Neogene block rotation in the northern Portneuf Range region, southeastern Idaho

The Putnam thrust has long been recognized as an important Mesozoic structure in the northern Portneuf Range, southeastern Idaho. At most localities, the thrust places Ordovician rocks above Permian and Pennsylvanian rocks, although near its southeastern extent, it ramps laterally downsection to the southeast. At its southeasternmost exposures, Cambrian rocks are juxtaposed above Mississippian rocks. New work indicates that the hanging wall of the Putnam thrust contains three imbricate thrust slices or subplates, which are, from structurally lowest to highest (and generally from north to south), the Lone Pine subplate, the Narrows subplate, and the Bear Canyon-Toponce subplate. The steeply south-dipping, east-trending Narrows thrust overlies the Lone Pine subplate, underlies the Narrows subplate, and is a lateral ramp that merges eastward into the Putnam thrust. Where exposed, the Narrows thrust places Late Proterozoic quartzite of the Brigham Group over Ordovician and Cambrian rocks. The Bear Canyon thrust overlies the Narrows subplate and underlies the Bear Canyon-Toponce subplate, dips eastward along the west side of the Portneuf Range, and places lower Brigham Group quartzite above Cambrian limestone and Cambrian and Late Proterozoic upper Brigham Group quartzite and argillite. At its northern extent, the Bear Canyon thrust curves to the east, where it merges with the Putnam thrust. On the east side of the range, the intensely folded Toponce thrust places upper Brigham Group quartzite above Ordovician rocks; the Toponce is believed to be an eastward extension of the Bear Canyon thrust. East-dipping rocks within the Lone Pine subplate were not strongly deformed during Cretaceous thrusting, in contrast to rocks within the Narrows subplate, where east-vergent recumbent folds, cleavage directions that fan about northerly strikes, and tectonic thickening and thinning of beds indicate intense, thrust-parallel shear. The deformation and thrust geometry within the Narrows subplate suggest that the Narrows subplate actually consists of several horses within a foreland-dipping duplex. Late Miocene and younger basin deposits occur in north-trending valleys adjacent t o the northern Portneuf Range and, to the west, the Bannock and Pocatello ranges. At most places, the Neogene deposits dip to the east by as much as 35°, indicating that late Miocene and younger extension and down-to-the-east rotation occurred along mostly west-dipping listric faults that are inferred to merge on at least one regional detachment. Although range-bounding faults account for a large component of extension and rotation, an additional large component was contributed by numerous, relatively small-displacement normal faults within mountain ranges.

Idaho↗
USGS1992

Allochthonous impact-shocked rocks and superimposed deformations at the Beaverhead site in southwest Montana

Upward-pointing shatter cones in sandstones of uncertain age (Middle Proterozoic? to Lower Cambrian?) and older crystalline basement rocks are exposed over an area of approximately 25 × 8 km in southwestern Montana. These shatter cones, together with pseudotachylites and breccias of various types (particularly in basement gneisses), are inferred to be products of a meteorite or cometary impact. However, Late Cretaceous contraction and Tertiary extension have contributed to the structural complexity of the area, and distinguishing unequivocally the shock brecciation from that due to younger tectonism is difficult. Stratigraphic constraints suggest the structure is Late Proterozoic or Cambrian in age. The shocked rocks are present in the Cabin thrust plate—one of many in the Late Cretaceous Cordilleran Thrust belt—and hence are allochthonous, having been transported tens of kilometers from the west. They are considered to represent only a piece from the central uplift of an original complex crater at least 75 km in diameter. It is speculated that some of the considerable uplift and erosion inferred to have taken place in Late Proterozoic to early Paleozoic time in east-central Idaho (The Lemhi arch) may be related to the postulated impact event. Furthermore, quasi-circular magnetic and regional gravity anomalies (50 to 75 km diameter) centered south-southeast of Challis, Idaho, may mark the concealed scar of the original impact structure.

Idaho, Montana↗
USGS1990

Follow-up evaluation of fifteen geochemically anomalous areas and evaluation of four prospects in the Farah Garan-Kutam mineral belt, Kingdom of Saudi Arabia

A follow-up exploration program was conducted in fifteen areas anomalous in precious and base metals within the Farah Garan-Kutam mineral belt, which forms part of a strongly deformed greenstone terrane in the southern part of the Proterozoic Arabian Shield. Using detailed chip-sample traverses, the program also evaluated four mineralized prospects, two of which (Raiah and Al Misadij prospects) had been recognized before the exploration program began; the additional two prospects (Kuhaym and Khathl prospects) were discovered during the course of the exploration program. Mineralized rock discovered during the exploration program consists of three types: (1) precious- and base-metal occurrences associated with large, lenticular, quartz-veined dolomitic bodies interpreted to be submarine exhalative deposits; the highest metal-concentration values are associated with silicified shear zones within the dolomite, which commonly were the sites of ancient mines; (2) precious- and base-metal mineralization associated with several small, isolated quartz veins scattered throughout the mineral belt; and (3) zones (several kilometers long and several hundred meters wide, with long axes oriented parallel to foliation) of variably silicified and pyritized greenstone and quartz-sericite phyllite; extensively dolomitized rock generally occurs in a zone surrounding the silicified and pyritized rock. Grades and (or) tonnages of all occurrences discovered during the exploration program are low the silicified and pyritized zones are entirely barren of base or precious metals-and no further work on them is recommended. The only significant mineralization discovered within the study area is located at the Raiah prospect, where a silicified shear zone (about 1 m wide) in lenticular exhalative dolomite body, contains as much as 5 ppm Au, 85 ppm Ag, 1.1 percent Cu, 2.6 percent Pb, and 10.7 percent Zn. Concentrations of the same elements within the surrounding dolomite are anomalously high, although they are significantly lower than values obtained in the shear zone. The inferred small tonnage of the deposit does not warrant further study.

Open-File Report↗
USGS1988

A paleomagnetic investigation of rocks from the Ohio Range and the Dry Valleys, Transantarctic Mountains, Antarctica

Two well-defined virtual geomagnetic poles (VGPs) for East Antarctica were obtained from the Middle Jurassic Ferrar Dolerite, sampled from a thick sill on Mt Schopf in the Ohio Range, and from a horizontal sheet intruding Paleozoic granitic rocks at Mt Cerberus in the Dry Valleys. The VGP from the sill at Mt Schopf lies at lat. 58°.0S, long. 129°.0W (dm=13°, dp=12°), and the VGP from Mt Cerberus lies at lat. 57°.8S, long. 135°.7W (dm=6°, dp=6°). Rocks from both localities have normal polarity magnetisations. These data, together with 15 other acceptable pole positions reported in the literature, define a Middle Jurassic paleomagnetic pole at 52°.7S, 139°.6W (α 95 =4°.4), which is not significantly different from previously reported mean Middle Jurassic paleomagnetic poles from East Antarctica. Paleomagnetic investigations in the Ohio Range of mafic inclusions in Ordovician granitic and sedimentary rocks of Devonian and Permian ages found that the rocks are magnetically unstable and are unreliable for determining a paleomagnetic pole.

New Zealand Journal of Geology and Geophysics↗
USGS1983

Opening of the Red Sea: Constraints from a palaeomagnetic study of the As Sarat volcanic field, south‐western Saudi Arabia

Four stratigraphic sections through alkali basalt flows of Oligocene to Miocene age (29‐24 Ma) in the As Sarat volcanic field, south‐western Saudi Arabia, were sampled for palaeomagnetic study. After systematic alternating‐field demagnetization, 42 magnetically acceptable flows (139 samples) yield a mean direction of magnetization of =355.3°, =15.2° (α=4.3°), which defines a palaeomagnetic pole at 78.8°N, 247.8°E. Of these acceptable flows, 24 are normally, and 18 reversely, magnetized. Part of one section was apparently erupted during the early phases of a polarity reversal of the Earth's field. The mean direction derived from the 24 normally magnetized flows is significantly different (after inverting 180°) from that derived from the 18 reversed flows, supporting the hypothesis of a displaced dipole source for the Earth's field in late Oligocene to early Miocene time. A comparison of the results from As Sarat with palaeomagnetic results from upper Tertiary rocks in Africa indicates that the Red Sea has opened 12° (estimated ±8° at the 95 per cent confidence level). These results indicate that most of the counter‐clockwise rotation of Arabia relative to Africa occurred since the eruption of the As Sarat volcanics, in disagreement with proposed models for main‐stage Red Sea spreading from late Eocene to early Oligocene time. The palaeomagnetic results also indicate that the Arabian Peninsula was more equatorial in late Oligocene to early Miocene time than it is now, by an amount compatible with the opening of the Gulf of Aden

As Sarat volcanic field↗
USGS1981

Paleomagnetic study of the As Sarat volcanic field, southwestern Saudi Arabia

Four stratigraphic sections through alkali basalt flows of Oligocene-Miocene age (24 to 29 m.y.) in the As Sarat volcanic field, southwestern Saudi Arabia, were sampled for paleomagnetic study. Forty-two magnetically acceptable flows (139 samples) yield a mean direction of magnetization of D=-4.7°, 1=15.2° ( α 95=4.3°), which defines a paleomagnetic pole at 78.8°N, 247.8°E. Of these acceptable flows, 24 are normally magnetized and 18 are reversed. Parts of two sections of flows erupted apparently during the early phases of a polarity reversal of the earth's field. Although the mean paleomagnetic directions determined from each flow do not collectively define a strict Fisherian distribution, the fact that the mean directions for each of the four sections are nearly identical indicates that the overall paleomagnetic pole position is reliable. The magnetostratigraphy can be only generally correlated from one section to another apparently because of a lateral thickening and pinching out of many flows between sections. The dispersion of directions due to secular variation of the upper Oligocene and lower Miocene field (standard angular deviation = 16.2°) is about the same as that produced by the recent field. If the rate of secular change during the time of As Sarat eruption was approximately that of the present, the rate of eruption during several sequences of As Sarat flows is estimated to be one flow about every 100 years. The fact that the mean direction derived from 24 normally magnetized flows is significantly different from that derived from the 18 reversed flows supports the hypothesis of a displaced dipole source for the earth's field in late Oligocene to early Miocene time. The results from As Sarat, as well as those from Aden, compared with paleomagnetic results from Late Tertiary rocks in Africa indicate with 95 percent confidence that the Red Sea has opened at least 2° in the past 5 m.y., and at least 4° in the past 25 m.y. The paleomagnetic results also indicate that the Arabian Peninsula was more equatorial in late Oligocene to early Miocene time than it is now, by an amount compatible with the opening of the Gulf of Aden.

As Sarat volcanic field↗
USGS1980

Paleomagnetic evidence for oroclinal bending of the southern Antarctic Peninsula

Two classes of fracture zones are distinguished on the basis of their orientations with respect to a spreading axis and length of associated ridge-ridge transform offset. (1) Minor fracture zones associated with transform faults of short offset (<30 km; minitransforms); the minor fracture zones may exhibit an asymmetric V-shaped configuration with respect to a spreading axis at variance with small circles about poles of plate rotation. (2) Major fracture zones associated with transform faults of long offset (>50 km); the major fracture zones exhibit a symmetric configuration with respect to a spreading axis following small circles about poles of plate rotation. Recognition of the coexistence of the two classes of fracture zones with different orientations on a slow-spreading oceanic ridge raises questions regarding the significance of the different orientations and nature of the intervening structural transition. A systematic narrow-beam bathymetric and magnetic investigation was performed to answer these questions in an area encompassing the change from minor fracture zones asymmetric with respect to the axis of the rift valley of the Mid-Atlantic Ridge at lat 26 degree N between major fracture zones, and a major fracture zone, the Kane, symmetric with respect to the axis of the rift valley at lat 24 degree N. The investigation delineated an intervening transitional region where structural features have continuously undergone geometric adjustments that have accommodated the discrepancy in orientation between the two classes of fracture zones for at least the past 6 m.y. A hypothesis of differential structural stability determined by thickness of lithosphere within transform offsets is advanced to explain the observed differences in behavior of the two classes of fracture zones. The orientation of a major fracture zone is constrained to follow small circles along a trajectory of relative plate motion by a long section of thick lithosphere in the associated transform fault. The orientation of a minor fracture zone is susceptible to reorientation in the short section of thin lithosphere in the associated transform fault; the reorientation reflects response to intra-plate and interplate stresses. The geometric adjustments that occur as a consequence of differential structural stability continuously accommodate any discrepancy in orientation that may develop between coexistent major and minor fracture zones, so that an ocean basin such as the Atlantic can open symmetrically.

GSA Bulletin↗