ARCHAEOMAGNETIC SECULAR VARIATION OF DIRECTION AND PALEOINTENSITY IN THE AMERICAN SOUTHWEST.
Oriented archaeomagnetic samples were collected from 158 in situ features at 33 sites in the southwestern U.S. Seventy-three independently dated features were used for analysis of secular variation. A moving-window smoothing technique with outlier rejection was developed to objectively compute a vir...
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ftunivarizona:oai:repository.arizona.edu:10150/185349 2023-05-15T16:19:42+02:00 ARCHAEOMAGNETIC SECULAR VARIATION OF DIRECTION AND PALEOINTENSITY IN THE AMERICAN SOUTHWEST. STERNBERG, ROBERT SAUL. Butler, Robert 1982 http://hdl.handle.net/10150/185349 en eng The University of Arizona. http://hdl.handle.net/10150/185349 688291829 8306460 Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Magnetometry in archaeology Paleomagnetism -- Southwest New Geomagnetism -- Secular variations -- Southwest text Dissertation-Reproduction (electronic) 1982 ftunivarizona 2020-06-14T08:03:19Z Oriented archaeomagnetic samples were collected from 158 in situ features at 33 sites in the southwestern U.S. Seventy-three independently dated features were used for analysis of secular variation. A moving-window smoothing technique with outlier rejection was developed to objectively compute a virtual geomagnetic pole (VGP) path. Weighted Fisher statistics, accounting for errors in both dating and archaeomagnetic direction, were used to compute a mean VGP and standard error (A95) within each window of time. The VGP moves from 86°N, 83°E at A.D. 750 to 74°N, 192°E at A.D. 1075, and then to 85°N, 236°E at A.D. 1425. Secular variation of the VGP ranges from .00423-.350°/yr with a median of .0359°/yr. The A95s for the VGP curve range from 1.33-5.28°. Archaeomagnetic declinations and inclinations in Tucson range from 346-359°E and 47-60°. The close agreement with a similarly constructed VGP curve for Arkansas implies a small nondipole field in North America between A.D. 1150-1450. The VGP curve is significantly different from that of R. L. DuBois. Three case histories of archaeomagnetic dating suggest the validity of the new curve. The Thellier-Thellier paleointensity experiment was performed on 187 specimens from 77 potsherds. A significant magnetic fabric anisotropy, typically 30%, was found. Using an easy-plane model of magnetization, the anisotropy correction systematically increased the paleointensities by 5%. Paleointensities were interpreted for 127 samples from 54 sherds. All ceramics were independently dated and used along with other results to construct a virtual axial dipole moment (VADM) curve. A moving-window smoother using weighted statistics within each interval of time and incorporating outlier analysis was used. The Southwestern VADM at 300 B.C. is 14 x 10('22)Am('2), decreases to 8.6 x 10²²Am² at A.D. 800, and increases to 12.9 x 10²²Am² at A.D. 1500. Paleointensities from Hohokam ceramics compare favorably with paleointensities from other Southwestern ceramics, regardless of whether the long Hohokam chronology beginning at 300 B.C. or the short chronology beginning at A.D. 500 are used. There is also reasonable agreement between the Southwest and Mesoamerican VADM records. Thesis Geomagnetic Pole The University of Arizona: UA Campus Repository DuBois ENVELOPE(-67.166,-67.166,-66.266,-66.266) |
institution |
Open Polar |
collection |
The University of Arizona: UA Campus Repository |
op_collection_id |
ftunivarizona |
language |
English |
topic |
Magnetometry in archaeology Paleomagnetism -- Southwest New Geomagnetism -- Secular variations -- Southwest |
spellingShingle |
Magnetometry in archaeology Paleomagnetism -- Southwest New Geomagnetism -- Secular variations -- Southwest STERNBERG, ROBERT SAUL. ARCHAEOMAGNETIC SECULAR VARIATION OF DIRECTION AND PALEOINTENSITY IN THE AMERICAN SOUTHWEST. |
topic_facet |
Magnetometry in archaeology Paleomagnetism -- Southwest New Geomagnetism -- Secular variations -- Southwest |
description |
Oriented archaeomagnetic samples were collected from 158 in situ features at 33 sites in the southwestern U.S. Seventy-three independently dated features were used for analysis of secular variation. A moving-window smoothing technique with outlier rejection was developed to objectively compute a virtual geomagnetic pole (VGP) path. Weighted Fisher statistics, accounting for errors in both dating and archaeomagnetic direction, were used to compute a mean VGP and standard error (A95) within each window of time. The VGP moves from 86°N, 83°E at A.D. 750 to 74°N, 192°E at A.D. 1075, and then to 85°N, 236°E at A.D. 1425. Secular variation of the VGP ranges from .00423-.350°/yr with a median of .0359°/yr. The A95s for the VGP curve range from 1.33-5.28°. Archaeomagnetic declinations and inclinations in Tucson range from 346-359°E and 47-60°. The close agreement with a similarly constructed VGP curve for Arkansas implies a small nondipole field in North America between A.D. 1150-1450. The VGP curve is significantly different from that of R. L. DuBois. Three case histories of archaeomagnetic dating suggest the validity of the new curve. The Thellier-Thellier paleointensity experiment was performed on 187 specimens from 77 potsherds. A significant magnetic fabric anisotropy, typically 30%, was found. Using an easy-plane model of magnetization, the anisotropy correction systematically increased the paleointensities by 5%. Paleointensities were interpreted for 127 samples from 54 sherds. All ceramics were independently dated and used along with other results to construct a virtual axial dipole moment (VADM) curve. A moving-window smoother using weighted statistics within each interval of time and incorporating outlier analysis was used. The Southwestern VADM at 300 B.C. is 14 x 10('22)Am('2), decreases to 8.6 x 10²²Am² at A.D. 800, and increases to 12.9 x 10²²Am² at A.D. 1500. Paleointensities from Hohokam ceramics compare favorably with paleointensities from other Southwestern ceramics, regardless of whether the long Hohokam chronology beginning at 300 B.C. or the short chronology beginning at A.D. 500 are used. There is also reasonable agreement between the Southwest and Mesoamerican VADM records. |
author2 |
Butler, Robert |
format |
Thesis |
author |
STERNBERG, ROBERT SAUL. |
author_facet |
STERNBERG, ROBERT SAUL. |
author_sort |
STERNBERG, ROBERT SAUL. |
title |
ARCHAEOMAGNETIC SECULAR VARIATION OF DIRECTION AND PALEOINTENSITY IN THE AMERICAN SOUTHWEST. |
title_short |
ARCHAEOMAGNETIC SECULAR VARIATION OF DIRECTION AND PALEOINTENSITY IN THE AMERICAN SOUTHWEST. |
title_full |
ARCHAEOMAGNETIC SECULAR VARIATION OF DIRECTION AND PALEOINTENSITY IN THE AMERICAN SOUTHWEST. |
title_fullStr |
ARCHAEOMAGNETIC SECULAR VARIATION OF DIRECTION AND PALEOINTENSITY IN THE AMERICAN SOUTHWEST. |
title_full_unstemmed |
ARCHAEOMAGNETIC SECULAR VARIATION OF DIRECTION AND PALEOINTENSITY IN THE AMERICAN SOUTHWEST. |
title_sort |
archaeomagnetic secular variation of direction and paleointensity in the american southwest. |
publisher |
The University of Arizona. |
publishDate |
1982 |
url |
http://hdl.handle.net/10150/185349 |
long_lat |
ENVELOPE(-67.166,-67.166,-66.266,-66.266) |
geographic |
DuBois |
geographic_facet |
DuBois |
genre |
Geomagnetic Pole |
genre_facet |
Geomagnetic Pole |
op_relation |
http://hdl.handle.net/10150/185349 688291829 8306460 |
op_rights |
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
_version_ |
1766006106368245760 |