Carnegie Ridge is a prominent bathymetric feature of the Gal??pagos Volcanic
Province originated from the interaction of the Gal??pagos Hot Spot and the Cocos -
Nazca Spreading Center. Our present knowledge regarding its crustal structure is limited
to ridge transects along which wide-angle refraction seismic experiments have been
conducted. In this study, the long-wavelength crustal structure of Carnegie Ridge
between ~81?? W and 89?? W was determined by employing 2-D forward gravity
modeling as the primary analytical technique. Model structures were built by assuming
Airy isostasy and crustal layers of constant density. The geometry and density structure
of the thickened oceanic crust beneath the ridge was constrained based on available
seismic velocity models. Except for regions near the Ecuador Trench, the gravity
modeling solution along the different transects examined in this study accounted
adequately for the observed gravity anomaly field over the ridge. Crustal overthickening
mainly accommodated in oceanic layer 3 and the asymmetry of the crustal root geometry
characterize the estimated long-wavelength crustal structure. The asymmetry on eastern
Carnegie Ridge is thought to be related to a ridge-related rifting whereas the origin and
nature of that estimated on western Carnegie Ridge remain uncertain. Crustal volume
fluxes were calculated at Carnegie Ridge and the Gal??pagos Archipelago, and at Cocos
Ridge in order to explain the along-axis variations of the estimated crustal thickness.
Along-axis crustal thickness variations on eastern Carnegie Ridge, and the formation of
its bathymetric saddle were found to be related to the decline in the total volume output
of the Gal??pagos Hot Spot. According to my results, this decay started soon after the
spreading center shifted to the south of the hotspot (i.e., ~15 Ma) and continued for ~4.5
m.y. Since ~10 Ma the volume output of the GHS started to increase again, giving rise to
the formation of western Carnegie Ridge and the Gal??pagos Archipelago. This increase
continued until ~2 Ma, when the hotspot intensity started a new decrease that continues
until the present time.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/2437 |
| Date | 29 August 2005 |
| Creators | De La Torre, Giorgio Michele |
| Contributors | Sager, William W. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 5005143 bytes, electronic, application/pdf, born digital |
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