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Jurassic and Cretaceous Microplankton From the Central Alborz Mountains, Iran

Date

1982-04

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Publisher

ORCID

Type

Degree Level

Masters

Abstract

This study was undertaken to survey Mesozoic marine palynofloras as might occur in Iran. Several suites of rock samples were collected from a wide geographical area and often through thick vertical sections. Standard palynological techniques were applies to these. Only one of the sections proved to contain significant Jurassic and Cretaceous assemblages consisting of dinoflagellate cysts, spores, pollen, acritarchs and scolecodonts. The section is located in the Central Alborz Mountains of northern Iran. Refinements made to the biostratigraphic interpretation of this section indicate that sediments of Callovian, Oxfordian and Kimmeridgian age are separated from Campanian strata by a major unconformity. Taxonomic changes include the addition of four new species, and one new subspecies: Ctenidodinium capituatum, Ctenidodinium varispinosum, Chlamydophorella ovale, Micrhystridium granospinosum, and Charangiella vnigri subsp. echinata. The Callovian assemblage provided an opportunity to observe the effects that authigenic pyrite can have on palynomorph textures. The observations support the thesis that "relict texture" is imposed on organic-walled microfossils after the growth of included pyrite crystals and during the diagenetic process f sediment compaction. The lowest parazone of the Campanian assemblages contains abundant linings of trochoid and biserial foraminifers. Some of these pseudochitinous linings provided the first reported examples of foramen plugs or "obturacula". Data gathered from the study of hand samples, thin sections, cyst morphologies, scolecodont distribution and miospore content indicate that both the Jurassic and the Cretaceous carbonate units were deposited in shallow water. The implication of dinoflagellate and angiosperm pollen (Normapolles) provincialism is that norther Iran, biogeographically, was related to the Laurasian landmass during the Mesozoic era.

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Citation

Degree

Master of Science (M.Sc.)

Department

Geological Sciences

Program

Geology

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