Mapping moho undulations beneath the Grand Banks of Newfoundland using gravity field data

Morrissey, B. Janet (2001) Mapping moho undulations beneath the Grand Banks of Newfoundland using gravity field data. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Avalon terrane of Newfoundland has been the subject of considerable study, especially in relation to the other tectono-stratigraphic terranes of the Appalachian Orogen. The Grand Banks of Newfoundland in particular, located within the Avalon terrane, has been intensely investigated on both a local and crustal scale. -- Gravity data is available for the Avalon terrane. A number of processing techniques, in both the space and frequency domains, was applied to the data in an effort to extract the topography of the Moho for the Grand Banks region. The data were passed through a series of low-pass filters, each having progressively lower cut-off frequencies to Isolate the long-wavelength signal from Moho. To ensure that the observed long-wavelength signal was due primarily to sources at Moho depth and not from intervening sources, the gravity field of the Mesozoic rift basins of the Grand Banks, also long-wavelength in character, was modelled and subtracted from the observed field. -- Using an average depth to Moho derived from spectral analysis of the field and from seismic data for the region as well as a density contrast obtained from direct (seismic refraction results) and indirect (inferred geology) sources, the data was inverted to obtain a map of depth to Moho. Profiles along selected seismic reflection line locations were extracted and the Mohos compared. The broad Moho relief obtained from the inverted gravity data agreed with that of the seismic Moho, however, the amplitude of the topography generated by the inversion is significantly reduced. In light of the sparse deep seismic coverage within the study area, the inversion results give a good first approximation to a comprehensive map of Moho topography for the region.

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