Search

Search Results

• 1. [Article] New 40Ar/39Ar age progression for the Louisville hot spot trail and implications for inter–hot spot motion

  In this study we present 42 new ⁴⁰Ar/³⁹Ar incremental heating age determinations that contribute to an updated age progression for the Louisville seamount trail. Louisville is the South Pacific counterpart ...

  Citation × Citation Citation Abstract Copy Title: New 40Ar/39Ar age progression for the Louisville hot spot trail and implications for inter–hot spot motion Author: Gee, Jeffrey S., Lonsdale, Peter F., Colwell, Lauren E., Koppers, Anthony A. P., Mahoney, John J., Duncan, Robert A., Gowen, Molly D. In this study we present 42 new ⁴⁰Ar/³⁹Ar incremental heating age determinations that contribute to an updated age progression for the Louisville seamount trail. Louisville is the South Pacific counterpart to the Hawaiian‐Emperor seamount trail, both trails representing intraplate volcanism over the same time interval (~80 Ma to present) and being examples of primary hot spot lineaments. Our data provide evidence for an age‐progressive trend from 71 to 21 Ma. Assuming fixed hot spots, this makes possible a direct comparison to the Hawaiian‐Emperor age progression and the most recent absolute plate motion (APM) model (WK08G) of Wessel and Kroenke (2008). We observe that for the Louisville seamount trail the measured ages are systematically older relative to both the WK08G model predictions and Hawaiian seamount ages, with offsets ranging up to 6 Myr. Taking into account the uncertainty about the duration of eruption and magmatic succession at individual Louisville volcanoes, these age offsets should be considered minimum estimates, as our sampling probably tended to recover the youngest lava flows. These large deviations point to either a contribution of inter–hot spot motion between the Louisville and Hawaiian hot spots or to a more easterly location of the Louisville hot spot than the one inferred in the WK08G model. Both scenarios are investigated in this paper, whereby the more eastern hot spot location (52.0°S, 134.5°W versus 52.4°S, 137.2°W) reduces the average age offset, but still results in a relatively large maximum offset of 3.7 Myr. When comparing the new ages to the APM models (S04P, S04G) by Steinberger et al. (2004) that attempt to compensate for the motion of hot spots in the Pacific (Hawaii) or globally (Hawaii, Louisville, Reunion and Walvis), the measured and predicted ages are more in agreement, showing only a maximum offset of 2.3 Myr with respect to the S04G model. At face value these more advanced APM models, which consider both plate and hot spot motions, therefore provide a better fit to the new Louisville age data. The fit is particularly good for seamounts younger than 50 Ma, a period for which there is little predicted motion for the Louisville hot spot and little inter–hot spot motion with Hawaii. However, discrepancies in the Louisville age‐distance record prior to 50 Ma indicate there is an extra source of inter–hot spot motion between Louisville and the other Pacific hot spots that was not corrected for in the global S04G model. Finally, based on six new ⁴⁰Ar/³⁹Ar age dates, the 169°W bend in the Louisville seamount trail seems to have formed at least 3 Myr before the formation of the Hawaiian‐Emperor bend. The timing of the most acute parts of both bends thus appears to be asynchronous, which would require other processes (e.g., plume motions) than a global plate motion change between 50 and 47 Ma to explain these two observations. Title: New 40Ar/39Ar age progression for the Louisville hot spot trail and implications for inter–hot spot motion Author: Gee, Jeffrey S., Lonsdale, Peter F., Colwell, Lauren E., Koppers, Anthony A. P., Mahoney, John J., Duncan, Robert A., Gowen, Molly D. In this study we present 42 new ⁴⁰Ar/³⁹Ar incremental heating age determinations that contribute to an updated age progression for the Louisville seamount trail. Louisville is the South Pacific counterpart to the Hawaiian‐Emperor seamount trail, both trails representing intraplate volcanism over the same time interval (~80 Ma to present) and being examples of primary hot spot lineaments. Our data provide evidence for an age‐progressive trend from 71 to 21 Ma. Assuming fixed hot spots, this makes possible a direct comparison to the Hawaiian‐Emperor age progression and the most recent absolute plate motion (APM) model (WK08G) of Wessel and Kroenke (2008). We observe that for the Louisville seamount trail the measured ages are systematically older relative to both the WK08G model predictions and Hawaiian seamount ages, with offsets ranging up to 6 Myr. Taking into account the uncertainty about the duration of eruption and magmatic succession at individual Louisville volcanoes, these age offsets should be considered minimum estimates, as our sampling probably tended to recover the youngest lava flows. These large deviations point to either a contribution of inter–hot spot motion between the Louisville and Hawaiian hot spots or to a more easterly location of the Louisville hot spot than the one inferred in the WK08G model. Both scenarios are investigated in this paper, whereby the more eastern hot spot location (52.0°S, 134.5°W versus 52.4°S, 137.2°W) reduces the average age offset, but still results in a relatively large maximum offset of 3.7 Myr. When comparing the new ages to the APM models (S04P, S04G) by Steinberger et al. (2004) that attempt to compensate for the motion of hot spots in the Pacific (Hawaii) or globally (Hawaii, Louisville, Reunion and Walvis), the measured and predicted ages are more in agreement, showing only a maximum offset of 2.3 Myr with respect to the S04G model. At face value these more advanced APM models, which consider both plate and hot spot motions, therefore provide a better fit to the new Louisville age data. The fit is particularly good for seamounts younger than 50 Ma, a period for which there is little predicted motion for the Louisville hot spot and little inter–hot spot motion with Hawaii. However, discrepancies in the Louisville age‐distance record prior to 50 Ma indicate there is an extra source of inter–hot spot motion between Louisville and the other Pacific hot spots that was not corrected for in the global S04G model. Finally, based on six new ⁴⁰Ar/³⁹Ar age dates, the 169°W bend in the Louisville seamount trail seems to have formed at least 3 Myr before the formation of the Hawaiian‐Emperor bend. The timing of the most acute parts of both bends thus appears to be asynchronous, which would require other processes (e.g., plume motions) than a global plate motion change between 50 and 47 Ma to explain these two observations. Close

• 2. [Article] Implications of a nonlinear ⁴⁰Ar/³⁹Ar age progression along the Louisville seamount trail for models of fixed and moving hot spots

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Implications of a nonlinear ⁴⁰Ar/³⁹Ar age progression along the Louisville seamount trail for models of fixed and moving hot spots Author: Koppers, Anthony A. P., Steinberger, Bernhard, Duncan, Robert A. Copyrighted by American Geophysical Union. Title: Implications of a nonlinear ⁴⁰Ar/³⁹Ar age progression along the Louisville seamount trail for models of fixed and moving hot spots Author: Koppers, Anthony A. P., Steinberger, Bernhard, Duncan, Robert A. Copyrighted by American Geophysical Union. Close

• 3. [Article] Nonlinear ⁴⁰Ar/³⁹Ar age systematics along the Gilbert Ridge and Tokelau Seamount Trail and the timing of the Hawaii-Emperor Bend

  Copyright 2007 by the American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Nonlinear ⁴⁰Ar/³⁹Ar age systematics along the Gilbert Ridge and Tokelau Seamount Trail and the timing of the Hawaii-Emperor Bend Copyright 2007 by the American Geophysical Union Title: Nonlinear ⁴⁰Ar/³⁹Ar age systematics along the Gilbert Ridge and Tokelau Seamount Trail and the timing of the Hawaii-Emperor Bend Copyright 2007 by the American Geophysical Union Close

• 4. [Article] Short-lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism?

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Short-lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism? Author: Staudigel, Hubert, Koppers, Anthony A. P., Wijbrans, Jan R., Pringle, Malcom S. Copyrighted by American Geophysical Union. Title: Short-lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism? Author: Staudigel, Hubert, Koppers, Anthony A. P., Wijbrans, Jan R., Pringle, Malcom S. Copyrighted by American Geophysical Union. Close

• 5. [Article] The marine geomorphology of American Samoa : shapes and distributions of deep sea volcanics

  The geologic processes at work in American Samoa have long been a point of scientific debate. Of its numerous volcanic formations, few breach sea level, leaving an enormous proportion of their mass unavailable ...

  Citation × Citation Citation Abstract Copy Title: The marine geomorphology of American Samoa : shapes and distributions of deep sea volcanics Author: Roberts, Jed T. The geologic processes at work in American Samoa have long been a point of scientific debate. Of its numerous volcanic formations, few breach sea level, leaving an enormous proportion of their mass unavailable to traditional observation. This study aims to describe the deep sea geomorphology of American Samoa through compilation, quantitative analysis, and qualitative interpretation of multibeam bathymetry datasets in an effort to contribute a new perspective on volcanic origins. Compilation of multibeam bathymetry datasets collected by various primary sources over the last two and half decades is accomplished using the multibeam processing software package MB-System by Caress and Chayes (1996). The high-resolution product is then employed to measure shape parameters of small seamounts (height < 1,000 m). Methods of quantitative analysis established by Jordan et al. (1983) and Smith (1988) are then used to assess the geomorphologic implications of shape parameter relationships. These relationships suggest that morphologies of small seamounts in American Samoa are typical of Pacific seamounts, though infrequent departures show forms indicative of mid-ocean ridge type magmas. A distribution analysis of small seamounts follows, calculating areal density with the exponential distribution model conceived by Jordan et al. (1983) and modified by Smith and Jordan (1988). Distribution analysis yields a predicted density of 2.8 seamounts per 1,000 km2 and a characteristic height of 139 m, both within expectations for seamounts in the Pacific. Finally, a qualitative interpretation of the entire study area is undertaken that includes mapping of major volcanic features, morphologic descriptions of large seamounts, and considerations of age-progression based on arrangements of volcanic lineaments. Title: The marine geomorphology of American Samoa : shapes and distributions of deep sea volcanics Author: Roberts, Jed T. The geologic processes at work in American Samoa have long been a point of scientific debate. Of its numerous volcanic formations, few breach sea level, leaving an enormous proportion of their mass unavailable to traditional observation. This study aims to describe the deep sea geomorphology of American Samoa through compilation, quantitative analysis, and qualitative interpretation of multibeam bathymetry datasets in an effort to contribute a new perspective on volcanic origins. Compilation of multibeam bathymetry datasets collected by various primary sources over the last two and half decades is accomplished using the multibeam processing software package MB-System by Caress and Chayes (1996). The high-resolution product is then employed to measure shape parameters of small seamounts (height < 1,000 m). Methods of quantitative analysis established by Jordan et al. (1983) and Smith (1988) are then used to assess the geomorphologic implications of shape parameter relationships. These relationships suggest that morphologies of small seamounts in American Samoa are typical of Pacific seamounts, though infrequent departures show forms indicative of mid-ocean ridge type magmas. A distribution analysis of small seamounts follows, calculating areal density with the exponential distribution model conceived by Jordan et al. (1983) and modified by Smith and Jordan (1988). Distribution analysis yields a predicted density of 2.8 seamounts per 1,000 km2 and a characteristic height of 139 m, both within expectations for seamounts in the Pacific. Finally, a qualitative interpretation of the entire study area is undertaken that includes mapping of major volcanic features, morphologic descriptions of large seamounts, and considerations of age-progression based on arrangements of volcanic lineaments. Close