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Sedimentary record of late-Holocene relative sea-level change and tectonic deformation from the Guerrero Seismic Gap, Mexican Pacific Coast

Sedimentary record of late-Holocene relative sea-level change and tectonic deformation from the Guerrero Seismic Gap, Mexican Pacific Coast
Sedimentary record of late-Holocene relative sea-level change and tectonic deformation from the Guerrero Seismic Gap, Mexican Pacific Coast
Studies of the coastal sedimentary record have allowed both the reconstruction of relative sea-level changes and the determination of local rates and magnitudes of tectonic deformation, particularly in tectonically active areas. Despite their successful use elsewhere, studies of this type are much less common for the Mexican Pacific coast, which parallels the Cocos-North America subduction plate boundary. Stratigraphic, geochemical and microfossil data from sediments in Laguna Mitla, the Pacific coast of Guerrero, Mexico, document late-Holocene sea-level changes induced by tectonic activity in the Mexican subduction zone. Three major events are identified. First, the formation of the lagoon by c. 4630 yr BP, as indicated by a freshwater to brackish peat. Second, a relative sea-level rise, or land subsidence, as indicated by a shift from a freshwater marginal lagoon environment to a marine setting, preceded by a marine inundation represented by a sand unit (possibly a tsunami deposit), by c. 3400 yr BP. And finally, a return to lagoonal conditions indicating a drop in relative sea level or coastal uplift by c. 2300 yr BP. The Laguna Mitla stratigraphy indicates general coastal subsidence or relative sea level rise of c. 1 mm/yr. We argue that these relative sea-level (land-level) changes have been induced by tectonic activity associated with the Mexican megathrust. A plausible explanation for the 3400 yr BP marine inundation is probably a tsunami produced by a large seismic event accompanied by coastal subsidence. Discrete fining upward, fine to coarse, sand units with an erosional basal contact, medium to poor sorting, and clay/mud rip-up clasts; an increase in Na and Sr elemental concentrations, indicative of a marine origin; and the landward extent of the sands support a tsunamigenic source for these deposits. However, these apparent tsunami deposits require further study to determine their lateral extent and to assess whether they can be correlated from one site to another. This study demonstrates the applicability of a multiproxy sedimentary approach in interpreting relative sea-level (land-level) changes and to derive data on related earthquake and tsunami events in tropical coastal lagoons.
Sea-level change, Holocene, earthquake, tectonic deformation, Guerrero Seismic Gap, tsunami, lagoon sediments, Mexico
0959-6836
1211-1220
Ramirez-Herrera, M.T.
e988cf8f-aa9a-4777-9b9e-d201bf5d6eaf
Cundy, A.
994fdc96-2dce-40f4-b74b-dc638286eb08
Kostoglodov, V.
3d6530c7-f5f2-4dc5-9b97-5ddef33177b7
Carranza-Edwards, A.
75249e5f-677f-4f82-9b16-eb858c136f68
Morales, E.
575ff484-8396-4ff6-bd61-4d95c3f8df94
Metcalfe, S.
43febe89-a616-4657-8172-07feb75475fe
Ramirez-Herrera, M.T.
e988cf8f-aa9a-4777-9b9e-d201bf5d6eaf
Cundy, A.
994fdc96-2dce-40f4-b74b-dc638286eb08
Kostoglodov, V.
3d6530c7-f5f2-4dc5-9b97-5ddef33177b7
Carranza-Edwards, A.
75249e5f-677f-4f82-9b16-eb858c136f68
Morales, E.
575ff484-8396-4ff6-bd61-4d95c3f8df94
Metcalfe, S.
43febe89-a616-4657-8172-07feb75475fe

Ramirez-Herrera, M.T., Cundy, A., Kostoglodov, V., Carranza-Edwards, A., Morales, E. and Metcalfe, S. (2007) Sedimentary record of late-Holocene relative sea-level change and tectonic deformation from the Guerrero Seismic Gap, Mexican Pacific Coast. The Holocene, 17 (8), 1211-1220. (doi:10.1177/0959683607085127).

Record type: Article

Abstract

Studies of the coastal sedimentary record have allowed both the reconstruction of relative sea-level changes and the determination of local rates and magnitudes of tectonic deformation, particularly in tectonically active areas. Despite their successful use elsewhere, studies of this type are much less common for the Mexican Pacific coast, which parallels the Cocos-North America subduction plate boundary. Stratigraphic, geochemical and microfossil data from sediments in Laguna Mitla, the Pacific coast of Guerrero, Mexico, document late-Holocene sea-level changes induced by tectonic activity in the Mexican subduction zone. Three major events are identified. First, the formation of the lagoon by c. 4630 yr BP, as indicated by a freshwater to brackish peat. Second, a relative sea-level rise, or land subsidence, as indicated by a shift from a freshwater marginal lagoon environment to a marine setting, preceded by a marine inundation represented by a sand unit (possibly a tsunami deposit), by c. 3400 yr BP. And finally, a return to lagoonal conditions indicating a drop in relative sea level or coastal uplift by c. 2300 yr BP. The Laguna Mitla stratigraphy indicates general coastal subsidence or relative sea level rise of c. 1 mm/yr. We argue that these relative sea-level (land-level) changes have been induced by tectonic activity associated with the Mexican megathrust. A plausible explanation for the 3400 yr BP marine inundation is probably a tsunami produced by a large seismic event accompanied by coastal subsidence. Discrete fining upward, fine to coarse, sand units with an erosional basal contact, medium to poor sorting, and clay/mud rip-up clasts; an increase in Na and Sr elemental concentrations, indicative of a marine origin; and the landward extent of the sands support a tsunamigenic source for these deposits. However, these apparent tsunami deposits require further study to determine their lateral extent and to assess whether they can be correlated from one site to another. This study demonstrates the applicability of a multiproxy sedimentary approach in interpreting relative sea-level (land-level) changes and to derive data on related earthquake and tsunami events in tropical coastal lagoons.

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More information

Published date: December 2007
Keywords: Sea-level change, Holocene, earthquake, tectonic deformation, Guerrero Seismic Gap, tsunami, lagoon sediments, Mexico
Organisations: Geochemistry

Identifiers

Local EPrints ID: 399464
URI: http://eprints.soton.ac.uk/id/eprint/399464
ISSN: 0959-6836
PURE UUID: 1134c478-fdf5-40cc-82b4-5c9b8cbd6d85
ORCID for A. Cundy: ORCID iD orcid.org/0000-0003-4368-2569

Catalogue record

Date deposited: 16 Aug 2016 13:59
Last modified: 05 Nov 2019 01:34

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