Seismic reconnaissance survey for the ICDP proposal 'Paleoclimate, Paleoenvironment, and Paleoecology of Neogene Central America: Bridging Continents and Oceans (NICA-BRIDGE)'
Geophysics
Final Report Abstract
The two largest lakes in Central America, Lake Nicaragua and Lake Managua, are situated in the south-central part of Nicaragua. The location and the proposed long existence (at least Pliocene possibly Late Miocene) make these lakes promising targets for scientific drilling within the International Continental Drilling Program. Drilling objectives therefore (a) development of a Neotropical environmental and paleoclimate record, e.g. including moisture availability/origin in the region for selected time periods back to Paleogene times, (b) determination of the times and rates of marine transgressions and regressions, their tectonic and climatic controls and ecological consequences, (c) investigation of recurrence rates and magnitudes of natural hazards such as explosive volcanic eruptions, landslides, earthquakes and hurricanes, (d) constraints on the timing and magmatic compositional changes during shifts of the volcanic arc, (e) linkages between long-term terrestrial and marine environmental records, (f) long-term basin development, and the deeper structure of western Nicaragua, and (g) correlation of climatic, geologic and (Holocene) anthropogenic influences on biodiversity and limnological variables, e.g. evaluating past freshwater/saltwater phases initiated by tectonics, and respective influence on micro- and macrobiota. The first seismic site survey data have been collected in the frame of this proposal. Major parts of the lake are characterized by a very strong lake floor reflector with reversed polarity, indicative of a sediment layer (probably volcaniclastic material) with free gas in the pore spaces. The small source (Micro-GI Gun with 0.1 l primary volume) was too weak to image features beneath this strong surface reflector. We did, however, identify at least one, probably tectonically active, area in the lake without free gas, which made it possible to obtain excellent images of the deeper subsurface. This area is located in the central part of the lake, east of Ometepe Island. The seismic data show stratified sediments with a thickness exceeding 300 m. Energy was attenuated at greater sub-surface depth, but deeper sediment likely exists and can be imaged with a larger source during additional pre-site surveys. The sedimentary succession is slightly tilted and thickens to the west, indicating progressive tilting of the sediments; some faults are imaged on the seismic data, documenting tectonic activity. The seismic image shows an interlayering of strong continuous reflectors and some slightly disturbed units. Such a pattern is typical for the interlayering of lacustrine and volcaniclastic deposits. The strong continuous reflectors may represent tephra layers and/or lacustrine sediments, whereas the slightly disturbed units most likely include volcanic landslide deposits (e.g. debris avalanches), deformed sediments related to the initial emplacement of debris avalanche deposits, or deposits of pyroclastic flows. A relatively thick transparent unit is found close to the lake floor, most likely representing a major mass transport deposits originating from Maderas Volcano. We do not see signs of significant erosion events such as incised channels or erosional unconformities. This suggests that the lake has existed as a water-filled body for a long time and hosts a continuous sedimentary succession, though small hiatuses cannot be ruled out because of the limited seismic resolution (a few meters for the air gun that was used).
Publications
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(2017) Seismic reconnaissance survey for the ICDP proposal ‘Paleoclimate, Paleoenvironment, and Paleoecology of Neogene Central America: Bridging Continents and Oceans (NICA-BRIDGE)’, IODP/ICDP Kolloquium 2017, TU Braunschweig, 14. – 16. März 2017
Krastel, S., Kutterolf, S., Lebas, E., Hagemann, K., Strauch, W.
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(2019) Paleoclimate, Paleoenvironment, and Paleoecology of Neogene Central America: Bridging Continents and Oceans (NICA-BRIDGE), 25th Latin-American Colloquium, 18. – 21 September 2019, Hamburg
Kutterolf, S., Brenner, M., Freundt, A., Kallmeyer, J., Krastel, S. Katsev, S., Meyer, A., Péréz, L., Rausch, J., Saballos, A., Schwalb, A., Strauch, W.
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(2019) Paleoclimate, Paleoenvironment, and Paleoecology of Neogene Central America: Bridging Continents and Oceans (NICA-BRIDGE), AGU Fall Meeting, 09. – 13 December 2019, San Francisco
Kutterolf, S., Brenner, M., Freundt, A., Kallmeyer, J., Krastel, S. Katsev, S., Meyer, A., Péréz, L., Rausch, J., Saballos, A., Schwalb, A., Strauch, W.
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(2019) Paleoclimate, Paleoenvironment, and Paleoecology of Neogene Central America: Bridging Continents and Oceans (NICA-BRIDGE), GeoMünster, 22. – 25. September 2019, Münster
Kutterolf, S., Brenner, M., Freundt, A., Kallmeyer, J., Krastel, S. Katsev, S., Meyer, A., Péréz, L., Rausch, J., Saballos, A., Schwalb, A., Strauch, W.
