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| Titel |
Three-dimensional sedimentary architecture of Quaternary deposits; a case study of environmental sedimentology (Bam, Iran) |
| VerfasserIn |
K. Rezaei, B. Guest, A. Friedrich, F. Fayazi, M. Nakhaei, H. Bakhtiari, L. Nouri |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020010
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| Zusammenfassung |
| Detailed 3-D analysis of the sedimentary structure and stratigraphy of these deposits
allows for an accurate understand of sedimentary model of basin. This paper presents a
case study in Bam (SE Iran) reconstructing the 3-D distribution of fluvial sediments
based on a high resolution, process-orientated sedimentary facies classification
and lithostratigraphy. We investigated the mean grain size with vertical and
horizontal change of it, clay mineralogy, sediment texture, sedimentary structures,
petrology and petrography and determination of paleo-environments and finally,
we prepared two cross sections in S-N and W-E directions and a 3D block
diagram for the situation of changes in subsurface sediments and compare
them with the destruction rate map of earthquake in Bam city. Quaternary
alluvial sediments are characterized by lithofacies deposited by braided river
channels, debris flows and hyperconcentrated flows. The channel flow deposits
constitute relatively well sorted, well imbricated and clast-supported gravels
with coarse to medium sand matrix. Mostly poorly sorted, weakly imbricated
to disorganized matrix supported pebble to boulder gravels with silty sand
represent debris flow deposits. Hyperconcentrated flow deposits consist of
clast-supported, poorly developed sorted polymodal gravel facies with poorly developed
imbricated fabric, and generally occupy the lower parts of the terrace and fan
sequences. The alternation from hyperconcentrated flow to channel flow deposits is
predominant in the sequence, and is possibly the response to different climate
modes. The high discharge and supply of sediments as well as the dispersal
and deposition of these materials in the trunk stream is attributed to climatic
perturbations during the Quaternary. These models allow quantifying the thickness
and volume distribution of sandy gravel and clay deposits. We correlate these
sedimentary units on the basis of lithofacies similarities, stratigraphic position. These
relationships suggest that deformation had occured upward into the basin during
time. According to our observations, a great number of recently constructed
buildings were also damaged in city areas far from the faulted zones. These
are areas where silty and clayey soils dominate, exhibiting very low electric
resistivity and low wave velocity, together with high thickness, plasticity and
compressibility. Rock samples are from volcanism stages in Eocene magmatism. The
clay minerals have resulted from weathering of continental environments in
upstream.
Key Words: Bam, Sediment, facies, 3D sedimentary model, Earthquake. |
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