Sedimentology
Majid Khazaee; Mahbobeh Hosseini-Barzi; Abbas Sadeghi; Hossein Mosaddegh
Abstract
The provenance of Jeirud Formation deposits (upper Devonian) in central Alborz has been investigated from study of siliciclastic sandstones (petrography, modal analysis and Heavy minerals assemblage) and mudstones (major and minor elements geochemistry). An integration of results suggest a mixture of ...
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The provenance of Jeirud Formation deposits (upper Devonian) in central Alborz has been investigated from study of siliciclastic sandstones (petrography, modal analysis and Heavy minerals assemblage) and mudstones (major and minor elements geochemistry). An integration of results suggest a mixture of basic to acidic igneous rocks and recycling of older sedimentary rocks as the provenance that weathered under cold and arid to semi-arid climatic conditions. An integration of modal analysis and heavy minerals results into the geochemical studies including Roser and korsch diagram (Log K2O/Na2O versus SiO2) and Verma and Armstrong-Altrin Functional diagrams, indicate that, siliciclastic rocks of Jeirud, resulted from weathering of acidic-intermediate to basic rocks of collisional tectonic provenances (recycled orogens) and transporting on craton interior and have been deposited on a passive margin basin. Investigations and comparison with McLennan et al., studies, represent that geochemical results and proportions of study area are consistent with those of old upper continental crust (OUC) typical of collisional tectonic settings.
M Khazaee; M Hosseini-Barzi; A Sadeghi; H Mosaddegh
Abstract
The Jeirud Formation (Upper Devonian) in Deh-Sufian section of northeast of Shahmirzad consists of siliciclastic and carbonate deposits. In the study area lower boundary of the Jeirud Formation with fine grain clastic deposits of the Mila Formation is erosional (Disconform) and has been conformably overlain ...
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The Jeirud Formation (Upper Devonian) in Deh-Sufian section of northeast of Shahmirzad consists of siliciclastic and carbonate deposits. In the study area lower boundary of the Jeirud Formation with fine grain clastic deposits of the Mila Formation is erosional (Disconform) and has been conformably overlain by dark carbonate deposits of the Mobarak Formation. The clastic deposits of the Jeirud Formation include conglomeratic, sandy and muddy facies. The conglomeratic deposits comprises three facies A1, A2 and A3 that are equivalent to Gcm, Gt and Gmm/Gmg of Miall facies respectively. Also, five sandy facies of B1, B2, B3 and B4 equivalent to St, Sh, Sm and Sr of Miall respectively and B5 (Shc) with hummocky cross stratification (HCS) sedimentary structure have been identified. Muddy facies including C1 and C2 are equivalents to Miall’s Fsm and Fl facies. Carbonate facies (D) comprising small amounts of the stratigraphic column is almost entirely dolomitized. Field and petrographic studies provide five facies association: fluvial, foreshore-backshore, shoreface, offshore transitional zone and offshore and carbonate facies interpreted as Proximal carbonate tempestites and distal carbonate tempestites based on evidences such as basal erosional surface, normal grading, HCS and coexisting clastic facies . In the study area, the Jeirud Formation deposits initiate with fluvial sequences that have been followed by storm dominated marine deposits as foreshore-backshore deposits and alternations of shoreface to offshore deposits. Study of sequence stratigraphic surfaces especially important subaerial unconformities and also stratal stacking patterns of the formation resulted in determination of three subaerial unconformity bounded depositional sequences plus transgressive part of the 4th sequence.
