Cenozoic Dynamic Topography of Madagascar
Abstract It has been proposed that Oligo‐Miocene regional uplift of Madagascar was generated and is maintained by mantle dynamical processes. Expressions of regional uplift include flat‐lying Upper Cretaceous‐Paleogene marine limestones that crop out at elevations of hundreds of meters along the wes...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2021-06-01
|
| Series: | Geochemistry, Geophysics, Geosystems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2020GC009624 |
| _version_ | 1797637957803311104 |
|---|---|
| author | S. N. Stephenson N. J. White A. Carter D. Seward P. W. Ball M. Klöcking |
| author_facet | S. N. Stephenson N. J. White A. Carter D. Seward P. W. Ball M. Klöcking |
| author_sort | S. N. Stephenson |
| collection | DOAJ |
| description | Abstract It has been proposed that Oligo‐Miocene regional uplift of Madagascar was generated and is maintained by mantle dynamical processes. Expressions of regional uplift include flat‐lying Upper Cretaceous‐Paleogene marine limestones that crop out at elevations of hundreds of meters along the western seaboard and emergent Quaternary coral‐rich terraces that rim the coastline. Here, we explore the history of subcrustal topographic support through a combined analysis of four sets of observational constraints. First, we exploit published receiver function estimates of crustal thickness and spectral admittance between gravity and topography. An admittance value of ∼+40 ± 10 mGal km−1 at wavelengths >500 km implies that ∼1 km of topography is supported by subcrustal processes. Secondly, new apatite fission‐track and helium measurements from 18 basement samples are inverted, constraining temperature and denudation histories. Results suggest that 0.5–1.6 km of regional uplift occurred after ∼30 Ma. Thirdly, we calculate a history of regional uplift by minimizing the misfit between observed and calculated longitudinal river profiles. Results suggest that topography was generated during Neogene times. Finally, inverse modeling of rare earth element concentrations in Neogene mafic rocks indicates that melting of the asthenospheric source occurred at depths of ≤65 km with potential temperatures of 1300–1370 °C. Melting occurred at higher temperatures beneath Réunion Island and northern Madagascar and at lower temperatures beneath the Comores and southern Madagascar. These inferences are consistent with shear wave velocities obtained from tomographic models. We conclude that Madagascar is underlain by thinned lithospheric mantle and that a thermal anomaly lies within an asthenospheric layer beneath northern Madagascar. |
| first_indexed | 2024-03-11T12:56:40Z |
| format | Article |
| id | doaj.art-921a565bc4d945a1b996825b9b74224e |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T12:56:40Z |
| publishDate | 2021-06-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-921a565bc4d945a1b996825b9b74224e2023-11-03T17:00:53ZengWileyGeochemistry, Geophysics, Geosystems1525-20272021-06-01226n/an/a10.1029/2020GC009624Cenozoic Dynamic Topography of MadagascarS. N. Stephenson0N. J. White1A. Carter2D. Seward3P. W. Ball4M. Klöcking5Bullard Laboratories Department of Earth Sciences University of Cambridge Cambridge UKBullard Laboratories Department of Earth Sciences University of Cambridge Cambridge UKDepartment of Earth and Planetary Sciences Birkbeck University of London London UKSchool of Geography, Environment and Earth Sciences Victoria University of Wellington Wellington New ZealandBullard Laboratories Department of Earth Sciences University of Cambridge Cambridge UKBullard Laboratories Department of Earth Sciences University of Cambridge Cambridge UKAbstract It has been proposed that Oligo‐Miocene regional uplift of Madagascar was generated and is maintained by mantle dynamical processes. Expressions of regional uplift include flat‐lying Upper Cretaceous‐Paleogene marine limestones that crop out at elevations of hundreds of meters along the western seaboard and emergent Quaternary coral‐rich terraces that rim the coastline. Here, we explore the history of subcrustal topographic support through a combined analysis of four sets of observational constraints. First, we exploit published receiver function estimates of crustal thickness and spectral admittance between gravity and topography. An admittance value of ∼+40 ± 10 mGal km−1 at wavelengths >500 km implies that ∼1 km of topography is supported by subcrustal processes. Secondly, new apatite fission‐track and helium measurements from 18 basement samples are inverted, constraining temperature and denudation histories. Results suggest that 0.5–1.6 km of regional uplift occurred after ∼30 Ma. Thirdly, we calculate a history of regional uplift by minimizing the misfit between observed and calculated longitudinal river profiles. Results suggest that topography was generated during Neogene times. Finally, inverse modeling of rare earth element concentrations in Neogene mafic rocks indicates that melting of the asthenospheric source occurred at depths of ≤65 km with potential temperatures of 1300–1370 °C. Melting occurred at higher temperatures beneath Réunion Island and northern Madagascar and at lower temperatures beneath the Comores and southern Madagascar. These inferences are consistent with shear wave velocities obtained from tomographic models. We conclude that Madagascar is underlain by thinned lithospheric mantle and that a thermal anomaly lies within an asthenospheric layer beneath northern Madagascar.https://doi.org/10.1029/2020GC009624apatite fission trackdynamic topographyIndian Oceanmantle dynamicsriver profile modelingthermochronology |
| spellingShingle | S. N. Stephenson N. J. White A. Carter D. Seward P. W. Ball M. Klöcking Cenozoic Dynamic Topography of Madagascar Geochemistry, Geophysics, Geosystems apatite fission track dynamic topography Indian Ocean mantle dynamics river profile modeling thermochronology |
| title | Cenozoic Dynamic Topography of Madagascar |
| title_full | Cenozoic Dynamic Topography of Madagascar |
| title_fullStr | Cenozoic Dynamic Topography of Madagascar |
| title_full_unstemmed | Cenozoic Dynamic Topography of Madagascar |
| title_short | Cenozoic Dynamic Topography of Madagascar |
| title_sort | cenozoic dynamic topography of madagascar |
| topic | apatite fission track dynamic topography Indian Ocean mantle dynamics river profile modeling thermochronology |
| url | https://doi.org/10.1029/2020GC009624 |
| work_keys_str_mv | AT snstephenson cenozoicdynamictopographyofmadagascar AT njwhite cenozoicdynamictopographyofmadagascar AT acarter cenozoicdynamictopographyofmadagascar AT dseward cenozoicdynamictopographyofmadagascar AT pwball cenozoicdynamictopographyofmadagascar AT mklocking cenozoicdynamictopographyofmadagascar |