Abstract
DECIPHERING the geological evolution of the Earth's continental crust requires knowledge of its bulk composition and global variability. The main uncertainties are associated with the composition of the lower crust. Seismic measurements probe the elastic properties of the crust at depth, from which composition can be inferred. Of particular note is Poisson's ratio, σ; this elastic parameter can be determined uniquely from the ratio of P- to S-wave seismic velocity, and provides a better diagnostic of crustal composition than either P- or S-wave velocity alone'. Previous attempts to measure σ have been limited by difficulties in obtaining coincident P- and S-wave data sampling the entire crust2. Here we report 76 new estimates of crustal σ spanning all of the continents except Antarctica. We find that, on average, σ increases with the age of the crust. Our results strongly support the presence of a mafic lower crust beneath cratons, and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions, followed by magmatic underplating, or a model in which crust formation processes have changed since the Precambrian era.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 152-154 |
| Number of pages | 3 |
| Journal | Nature |
| Volume | 374 |
| Issue number | 6518 |
| State | Published - Mar 9 1995 |
| Externally published | Yes |
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Cite this
Continental crust composition constrained by measurements of crustal Poisson's ratio. / Zandt, George; Ammon, Charles J.
In: Nature, Vol. 374, No. 6518, 09.03.1995, p. 152-154.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Continental crust composition constrained by measurements of crustal Poisson's ratio
AU - Zandt, George
AU - Ammon, Charles J.
PY - 1995/3/9
Y1 - 1995/3/9
N2 - DECIPHERING the geological evolution of the Earth's continental crust requires knowledge of its bulk composition and global variability. The main uncertainties are associated with the composition of the lower crust. Seismic measurements probe the elastic properties of the crust at depth, from which composition can be inferred. Of particular note is Poisson's ratio, σ; this elastic parameter can be determined uniquely from the ratio of P- to S-wave seismic velocity, and provides a better diagnostic of crustal composition than either P- or S-wave velocity alone'. Previous attempts to measure σ have been limited by difficulties in obtaining coincident P- and S-wave data sampling the entire crust2. Here we report 76 new estimates of crustal σ spanning all of the continents except Antarctica. We find that, on average, σ increases with the age of the crust. Our results strongly support the presence of a mafic lower crust beneath cratons, and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions, followed by magmatic underplating, or a model in which crust formation processes have changed since the Precambrian era.
AB - DECIPHERING the geological evolution of the Earth's continental crust requires knowledge of its bulk composition and global variability. The main uncertainties are associated with the composition of the lower crust. Seismic measurements probe the elastic properties of the crust at depth, from which composition can be inferred. Of particular note is Poisson's ratio, σ; this elastic parameter can be determined uniquely from the ratio of P- to S-wave seismic velocity, and provides a better diagnostic of crustal composition than either P- or S-wave velocity alone'. Previous attempts to measure σ have been limited by difficulties in obtaining coincident P- and S-wave data sampling the entire crust2. Here we report 76 new estimates of crustal σ spanning all of the continents except Antarctica. We find that, on average, σ increases with the age of the crust. Our results strongly support the presence of a mafic lower crust beneath cratons, and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions, followed by magmatic underplating, or a model in which crust formation processes have changed since the Precambrian era.
UR - http://www.scopus.com/inward/record.url?scp=0028792984&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028792984&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0028792984
VL - 374
SP - 152
EP - 154
JO - Nature
JF - Nature
SN - 0028-0836
IS - 6518
ER -