introduction to ammonite assemblages of delichay formation in polour section, central alborz, iran

In this research lithostratioghrphy and biostratigraphy have been studied in south polour; in central alborz zone. according to the field observations and obtains, about 80 meter of the thickness of delichay formation in this zone is systematically sampled. in the whole mass of rocks, lithological characters have been noticed while sampling. ammonite criteria samples have gathered among the layers and debris, sent to the laboratory in order to study and identify the type and specie. the importance is that the lithography characteristics consisting texture and structure, while studying doesn’t differ a lot with the type section of delichai .in this section, delichay formation has been observed alternately made of marly lime with rich ammonite fauna. the lower layer of delichay formation is shemshak and its upper layer also reaches the lar limy formation gradually. the whole view of the formation is gray. according to the paleontological studies, in the whole formation thickness, 8 types of ammonite have been identified. it should be mention that in regard to destruction degree of visible signs in ammonite samples, recognizing the specie is possible which prevents recognizing the type. the oldest ammonite which is identified in the study section is procerites (early athonian) and the youngest is reineckeia sp. (late cllovian). according to investigations the age of delichay formation is determined early bathtonin to late callovian.