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Papers by Richard Jarrard
Journal of Geophysical Research, 1985
A technique that eliminates external field sources and the effects of strike aliasing was used to... more A technique that eliminates external field sources and the effects of strike aliasing was used to extract from marine survey data the intermediate wavelength magnetic anomaly field for (B) in the North Pacific. A strong correlation exists between this field and the Magsat field although a directional sensitivity in the Magsat field can be detected. The intermediate wavelength field is correlated to tectonic features. Island arcs appear as positive anomalies of induced origin likely due to variations in crustal thickness. Seamount chains and oceanic plateaus also are manifested by strong anomalies. The primary contribution to many of these anomalies appears to be due to a remanent magnetization. The source parameters for the remainder of these features are presently unidentified ambiguous. Results indicate that the sea surface field is a valuable source of information for secular variation analysis and the resolution of intermediate wavelength source parameters.
Epic3terra Antartica Bremerhaven Pangaea 5 Pp 299 310, 1998
... Stand from May ABCDEFGHIJKLMNOPQRSTUVWXYZ Saline outflow from the Arctic Ocean its contributi... more ... Stand from May ABCDEFGHIJKLMNOPQRSTUVWXYZ Saline outflow from the Arctic Ocean its contribution the deep waters the Greenland Norwegian and Iceland Seas Journal Geophysical Research Aagaard Fahrbach Meincke Swift Structure and geological processes The ...
The presence of authigenic smectite in the lower Oligocene sandstones of the Cape Roberts Project... more The presence of authigenic smectite in the lower Oligocene sandstones of the Cape Roberts Project core CRP-3 from the Victoria Land Basin of Antarctica is confirmed by scanning electron, scanning-transmission electron, and light microscopy. It was emplaced as a single generation of cement within the lower portion of the Oligocene section. This section has undergone no discernible compaction since cementation.
Drillhole CRP-3 in northern McMurdo Sound (Ross Sea, Antarctica) targeted the western margin of t... more Drillhole CRP-3 in northern McMurdo Sound (Ross Sea, Antarctica) targeted the western margin of the Victoria Land basin to investigate Neogene to Palaeogene climate and tectonic history by obtaining continuous core and downhole logs. Well logging of CRP-3 has provided a complete and comprehensive data set of in situ geophysical measurements down to nearly the bottom of the hole (920
The Arctic Ocean Region, 1990
Abstract The well logging activity of the Ocean Drilling Programme, which deploys the most techni... more Abstract The well logging activity of the Ocean Drilling Programme, which deploys the most technically advanced suite of downhole measurements available for routine use, is providing new opportunities for advancement in marine geoscience. Particular examples ...
ABSTRACT To define the present-day stress field in the upper crust and to understand the recent t... more ABSTRACT To define the present-day stress field in the upper crust and to understand the recent tectonic activity in Antarctica, a study of breakout measurements along AND-2A well was performed. The borehole breakout is an important indicator of horizontal stress orientation and occurs when the stresses around the borehole exceed that required to cause compressive failure of the borehole wall (Bell and Gough, 1979; Zoback et al., 1985, Bell, 1990). The enlargement of the wellbore is caused by the development of intersecting conjugate shear planes that cause pieces of the borehole wall to spall off. Around a vertical borehole, stress concentration is greatest in the direction of the minimum horizontal stress (Shmin), hence, the long axes of borehole breakouts are oriented approximately perpendicular to the maximum horizontal stress orientation (SHmax). The orientation of breakouts along the AND-2A well was measured using acoustic (BHTV) and mechanical (Four-Arm Caliper) tools. Borehole televiewer (BHTV) provides an acoustic "image" of the borehole wall (360 degree coverage) and gives detailed information for investigation of fractures and stress analysis. The four-arm caliper is the oldest technique for borehole breakout identification and it is included in routine dipmeter logs. A quality value has been assigned to the well results in agreement with the World Stress Map quality ranking scheme (Zoback, 1992; Heidback et al., 2010) based mainly on the number, accuracy, and length of breakout measurements. The result is presented as rose diagram of the breakout directions where the length of each peak is proportional to the frequency and the width to the variance of its gaussian curve. We have analyzed the following curves to recognize the breakout: the azimuth of Pad 1 (P1az), the drift azimuth (HAZI), the two calipers with respect to the bit size (BZ) curve and the curve relative to the deviation of the well. The AND-2A Four-Arm Caliper data cover a depth interval between 637 down to 997 mbsl, that corresponds to 360 m of logged interval. We have distinguished breakouts and some washouts only in the interval from 753 to 825 mbsl. From borehole televiewer images, we have data from 398 mbsl down to 1136 mbsl. The BHTV worked well showing a lot of interesting features such as many bedding, lamination and fractures (natural and induced) but poor breakouts. The rare breakouts have also a small size (called proto-breakouts) but they are consistent with induced features. Considering the breakout result from caliper and BHTV, the AND-2A borehole is unfortunately classified as D quality. This means that to obtain a reliable active stress field of the area it is necessary to compare this result with other available data.
Palaeontology, 2005
A new metazoan, Skeemella clavula gen. et sp. nov., is described from the Middle Cambrian Pierson... more A new metazoan, Skeemella clavula gen. et sp. nov., is described from the Middle Cambrian Pierson Cove Formation of the Drum Mountains, Utah, USA. Skeemella is similar to vetulicolians, but differs from other examples of this group in the relative proportions of the anterior and posterior sections, the large number of divisions, and the elongate bifid termination. The posterior section is arthropodan in character. The similarity of this fossil to vetulicolians throws hypotheses of their deuterostome affinity into question and highlights their problematic sta- tus.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2009
Journal of Paleontology, 2008
Journal of Geophysical Research, 1989
Journal of Geophysical Research, 2003
Geophysical Research Letters, 1988
AF demagnetization of thermoremanent magnetization (TRM) and saturation isothermal remanent magne... more AF demagnetization of thermoremanent magnetization (TRM) and saturation isothermal remanent magnetization (IRM (s)) are used to establish diagnostic criteria for primary TRM and for secondary magnetization in igneous rocks. In applying the approach to the ...
Geophysical Research Letters, 2000
Journal of Geophysical Research, 1985
A technique that eliminates external field sources and the effects of strike aliasing was used to... more A technique that eliminates external field sources and the effects of strike aliasing was used to extract from marine survey data the intermediate wavelength magnetic anomaly field for (B) in the North Pacific. A strong correlation exists between this field and the Magsat field although a directional sensitivity in the Magsat field can be detected. The intermediate wavelength field is correlated to tectonic features. Island arcs appear as positive anomalies of induced origin likely due to variations in crustal thickness. Seamount chains and oceanic plateaus also are manifested by strong anomalies. The primary contribution to many of these anomalies appears to be due to a remanent magnetization. The source parameters for the remainder of these features are presently unidentified ambiguous. Results indicate that the sea surface field is a valuable source of information for secular variation analysis and the resolution of intermediate wavelength source parameters.
Epic3terra Antartica Bremerhaven Pangaea 5 Pp 299 310, 1998
... Stand from May ABCDEFGHIJKLMNOPQRSTUVWXYZ Saline outflow from the Arctic Ocean its contributi... more ... Stand from May ABCDEFGHIJKLMNOPQRSTUVWXYZ Saline outflow from the Arctic Ocean its contribution the deep waters the Greenland Norwegian and Iceland Seas Journal Geophysical Research Aagaard Fahrbach Meincke Swift Structure and geological processes The ...
The presence of authigenic smectite in the lower Oligocene sandstones of the Cape Roberts Project... more The presence of authigenic smectite in the lower Oligocene sandstones of the Cape Roberts Project core CRP-3 from the Victoria Land Basin of Antarctica is confirmed by scanning electron, scanning-transmission electron, and light microscopy. It was emplaced as a single generation of cement within the lower portion of the Oligocene section. This section has undergone no discernible compaction since cementation.
Drillhole CRP-3 in northern McMurdo Sound (Ross Sea, Antarctica) targeted the western margin of t... more Drillhole CRP-3 in northern McMurdo Sound (Ross Sea, Antarctica) targeted the western margin of the Victoria Land basin to investigate Neogene to Palaeogene climate and tectonic history by obtaining continuous core and downhole logs. Well logging of CRP-3 has provided a complete and comprehensive data set of in situ geophysical measurements down to nearly the bottom of the hole (920
The Arctic Ocean Region, 1990
Abstract The well logging activity of the Ocean Drilling Programme, which deploys the most techni... more Abstract The well logging activity of the Ocean Drilling Programme, which deploys the most technically advanced suite of downhole measurements available for routine use, is providing new opportunities for advancement in marine geoscience. Particular examples ...
ABSTRACT To define the present-day stress field in the upper crust and to understand the recent t... more ABSTRACT To define the present-day stress field in the upper crust and to understand the recent tectonic activity in Antarctica, a study of breakout measurements along AND-2A well was performed. The borehole breakout is an important indicator of horizontal stress orientation and occurs when the stresses around the borehole exceed that required to cause compressive failure of the borehole wall (Bell and Gough, 1979; Zoback et al., 1985, Bell, 1990). The enlargement of the wellbore is caused by the development of intersecting conjugate shear planes that cause pieces of the borehole wall to spall off. Around a vertical borehole, stress concentration is greatest in the direction of the minimum horizontal stress (Shmin), hence, the long axes of borehole breakouts are oriented approximately perpendicular to the maximum horizontal stress orientation (SHmax). The orientation of breakouts along the AND-2A well was measured using acoustic (BHTV) and mechanical (Four-Arm Caliper) tools. Borehole televiewer (BHTV) provides an acoustic "image" of the borehole wall (360 degree coverage) and gives detailed information for investigation of fractures and stress analysis. The four-arm caliper is the oldest technique for borehole breakout identification and it is included in routine dipmeter logs. A quality value has been assigned to the well results in agreement with the World Stress Map quality ranking scheme (Zoback, 1992; Heidback et al., 2010) based mainly on the number, accuracy, and length of breakout measurements. The result is presented as rose diagram of the breakout directions where the length of each peak is proportional to the frequency and the width to the variance of its gaussian curve. We have analyzed the following curves to recognize the breakout: the azimuth of Pad 1 (P1az), the drift azimuth (HAZI), the two calipers with respect to the bit size (BZ) curve and the curve relative to the deviation of the well. The AND-2A Four-Arm Caliper data cover a depth interval between 637 down to 997 mbsl, that corresponds to 360 m of logged interval. We have distinguished breakouts and some washouts only in the interval from 753 to 825 mbsl. From borehole televiewer images, we have data from 398 mbsl down to 1136 mbsl. The BHTV worked well showing a lot of interesting features such as many bedding, lamination and fractures (natural and induced) but poor breakouts. The rare breakouts have also a small size (called proto-breakouts) but they are consistent with induced features. Considering the breakout result from caliper and BHTV, the AND-2A borehole is unfortunately classified as D quality. This means that to obtain a reliable active stress field of the area it is necessary to compare this result with other available data.
Palaeontology, 2005
A new metazoan, Skeemella clavula gen. et sp. nov., is described from the Middle Cambrian Pierson... more A new metazoan, Skeemella clavula gen. et sp. nov., is described from the Middle Cambrian Pierson Cove Formation of the Drum Mountains, Utah, USA. Skeemella is similar to vetulicolians, but differs from other examples of this group in the relative proportions of the anterior and posterior sections, the large number of divisions, and the elongate bifid termination. The posterior section is arthropodan in character. The similarity of this fossil to vetulicolians throws hypotheses of their deuterostome affinity into question and highlights their problematic sta- tus.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2009
Journal of Paleontology, 2008
Journal of Geophysical Research, 1989
Journal of Geophysical Research, 2003
Geophysical Research Letters, 1988
AF demagnetization of thermoremanent magnetization (TRM) and saturation isothermal remanent magne... more AF demagnetization of thermoremanent magnetization (TRM) and saturation isothermal remanent magnetization (IRM (s)) are used to establish diagnostic criteria for primary TRM and for secondary magnetization in igneous rocks. In applying the approach to the ...
Geophysical Research Letters, 2000