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Sedimentary responses to active growth-faulting in coastal marshes of the northern Gulf of Mexico Phil Wolfe GLY 730 Spring 2012.

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Presentation on theme: "Sedimentary responses to active growth-faulting in coastal marshes of the northern Gulf of Mexico Phil Wolfe GLY 730 Spring 2012."— Presentation transcript:

1 Sedimentary responses to active growth-faulting in coastal marshes of the northern Gulf of Mexico Phil Wolfe GLY 730 Spring 2012

2 introduction Coastal marshes…why do we care? Productive ecosystems Important habitat for both aquatic and terrestrial plants and animals Northern Gulf of Mexico Wetland losses Due to large scale and localized processes Deep-seated growth fault movement and autocompaction Local submergence due to vertical displacement along active normal growth faults Localized processes can have farther-reaching impacts Surface hydrology and vegetation -> accretion processes

3 introduction Objectives 1.What do the sedimentary processes look like in response to active faulting in these settings? 2.Wetlands can maintain system equilibrium in this instance…but are they? 3.What happens when vertical accretion rates < subsidence rates?

4 geologic setting Northern Gulf of Mexico Numerous growth fault systems Growth fault – syndepositional, normal listric-type fault that often exhibits increasing throw at depth and expanded equivalent stratigraphic thickness on the downthrown side Emplaced during Cenozoic Recent reactivation Anthropogenic processes = subsurface fluid withdrawal and reservoir compaction Natural processes = migrating salt structures and movement of deep-seated growth faults

5 geologic setting

6 methods Aerial photography

7 methods Sediment core lithostratigraphic correlation

8 methods

9 methods Rod Sediment Elevation Tables (RSET)

10 sediment geochronology Short-lived fallout radionuclides 137 Cs and 210 Pb Provide maximum temporal resolution of ~100 years

11 results and discussion Cline et al. (2011) Results: Time series aerial photography revealed observable trend between fault scarp proximity and land cover change Suggested that faulting and land cover loss are correlated Land cover changes on downthrown extent more rapid and of greater magnitude From 1948-2008, total water area increase of 451.3% on downthrown, compared to 317% on upthrown

12 results and discussion Feagin et al. (2010), Morton et al. (2001), and Yeager et al. (2012) Results: Marsh facies and foram assemblages on downthrown side of fault suggest accelerated displacement Marsh forams at surface indicate that vertical displacement is ongoing and out-paces sediment supply

13 results and discussion Feagin et al. (2010), Morton et al. (2001), and Yeager et al. (2012) Results: RSET station monitoring over three-year period (2007-2010) More sediment accumulation on down-dropped block due to increased accommodation space These rates unable to keep pace with local RSL rise

14 results and discussion Feagin et al. (2010), Morton et al. (2001), and Yeager et al. (2012) Results: Sediment geochronology ( 210 Pb and 137 Cs) show increased sediment mass accumulation rates on downthrown side Again, vertical displacement outpaces sediment supply -> wetland submergence Matagorda, TX Pearl River, LA

15 results and discussion Feagin et al. (2010), Morton et al. (2001), and Yeager et al. (2012) Results: Fault induced subsidence and subaqueous erosion on downthrown side of fault Vertical accretion << rates of vertical displacement and RSL rise = open water conversion

16 conclusions Accretion rates are typically higher on the downthrown side of the fault relative to the upthrown side Vertical accretion rates in many coastal marshes of the northern Gulf of Mexico are not able to keep pace with rates of fault-driven subsidence Permanent land cover changes in coastal marshes has been occurring and appears to be ongoing

17 references Chan, A.W. and Zoback, M.D., 2007. The role of hydrocarbon production on land subsidence and fault reactivation in the Louisiana coastal zone. Journal of Coastal Research, 23, 771-786. Cline, M. D., R. A. Feagin, Yeager, K.M., Van Alstyne, J.M., 2011. Fault-induced wetland loss at Matagorda, Texas, USA: land cover changes from 1943 to 2008. Geocarto International 26(8), 633-645. Dokka, R.K., Sella, G.F., and Dixon, T.H., 2006a. Tectonic control of subsidence and southward displacement of southeast Louisiana with respect to stable North America. Geophysical Research Letters, 33, L23308. Dokka, R.K., 2006b. Modern-day tectonic subsidence in coastal Louisiana. Geology, 34(4), 281-284. Feagin, R.A. and Yeager, K.M., unpublished. Salt marsh accretion rates on the upper Texas coast: Will sea level rise drown our marshes? A report to NOAA. College Station, Texas Feagin, R.A., Yeager, K.M., Brunner, C.A., Paine, J., 2010. Vegetation transition and sedimentary responses to fault-induced sea level rise. A report to NICCR-DOE. College Station, Texas: NICCR Coastal Center, Tulane University. Gagliano, S.M., Kemp, E.B., Wicker, K.M., Wiltenmuth, K.S., 2003. Active geological faults and land change in southeastern Louisiana. Prepared for US Army Corps of Engineers, New Orleans District, Contract No. DACW 29-00-C-0034 Huntley, S.L., Wenning, R.J., Su, S.H., Bonnevie, N.L., Paustenbach, D.J., 1995. Geochronology and sedimentology of the lower Passaic River, New Jersey. Estuaries, 18(2): 351-361. Kennish, M.J., 2001. Coastal salt marsh systems: a review of anthropogenic impacts. Journal of Coastal Research 17: 731–748. Koide, M., Soutar, A., Goldberg, E.D., 1973. Marine geochronology with 210 Pb. Earth and Planetary Science Letters, 14, 442-446. Krishnaswami, S., Martin, J.M., Meybeck, M., 1971. Geochronology of lake sediments. Earth and Planetary Science Letters, 11, 407-414. Lankesky, D.E., Logan, B.W., Brown, R.G., Hine, A.C., 1979. A new approach to portable vibracoring underwater and on land. Journal of Sedimentary Petrology, 49, 654-657. Morton, R.A., Purcell, N.A., Peterson, R.L., 2001. Field evidence of subsidence and faulting induced by hydrocarbon production in coastal southeast Texas. Gulf Coast Association of Geological Societies Transactions, 51, 239-248. Morton, R.A., Bernier, J.C., Barras, J.A., 2006. Evidence of regional subsidence and associated interior wetland loss induced by hydrocarbon production, Gulf Coast region, USA. Environmental Geology, 50, 261-274. Nelson, T.H., 1991. Salt tectonics and listric-normal faulting. In: A. Salvador, ed. The Gulf of Mexico Basin. Boulder, CO: The Geological Society of America. White, W.A., Tremblay, T.A., 1995. Submergence of wetlands as a result of human-induced subsidence and faulting along the upper Texas Gulf Coast. Journal of Coastal Research, 11, 788-807. White, W.A., Morton, R.A., 1997. Wetland losses related to fault movement and hydrocarbon production, Southeastern Texas coast. Journal of Coastal Research, 13, 1305-1320. White, W.A., Morton, R.A., Holmes, C.W., 2002. A comparison of factors controlling sedimentation rates and wetland loss in fluvial-deltaic systems, Texas Gulf coast. Geomorphology, 44, 47-66. Williams, H., 1995. Assessing the impact of weir construction on recent sedimentation using cesium-137. Environmental Geology, 26, 166- 171. Worrall, D.M., Snelson, S., 1989. Evolution of the northern Gulf of Mexico, with emphasis on Cenozoic growth faulting and the role of salt. In: A.W. Bally and A.R. Palmer, eds. The Geology of North America. Boulder, CO: Geological Society of America. Yeager, K.M., Brunner, C.A., Kulp, M.A., Fischer, D., Feagin, R.A., Schindler, K.J., Prouhet, J., Bera, G., 2012. Significance of active growth faulting on marsh accretion processes in the lower Pearl River, Louisiana. Geomorphology 153- 154, 127-143.

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