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Middle Jurassic palynology of the southwest Tabas Block, Central-East Iran

Authors:
Fatemeh Vaezjavadi at University of Tehran, Tehran, I.S. Iran
Fatemeh Vaezjavadi
  • University of Tehran, Tehran, I.S. Iran
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Abstract

Diverse and moderately to poorly preserved palynofloras occur in the lower Middle Jurassic sediment of the Hojedk Formation in the Chahrekhneh, southwestern of Tabas, east central Iran. The palynofloras comprise fifty-six species including spores (fifteen species allocated to seven genera), various types of pollen (thirty species designated to sixteen genera), dinoflagellate cysts (ten species belonged to three genera), and one acritarch species. Vertical distribution of miospores allows erection within the Hojedk Formation of one biozone–Klukisporites variegatus- Callialasporites trilobatus Assemblage zone– based on the first observed occurrence (FOO) and the last observed occurrence (LOO) of selected taxa. Moreover, vertical distribution of dinoflagellate cysts allows erection within this formation of one biozone- Nannoceratopsis sp. cf. N. gracilis Interval zone. These biozones are compared with palynozones from ± coeval strata in Iran and elsewhere. Abundance of ferns and cycadophytes in parent floras implies that the host strata accumulated under a moist warm climate during the early Middle Jurassic in this locality. Based on various data of ecogroups in Chahrekhneh, it should be considered that there were several environments of upland, warmer lowland, wetter lowland, rivers and delta. Furthermore, based on the occurrence of dinoflagellate cysts it can conclude that Chahrekhneh located at the south coastal boundary of the Iran Plate, along the Tethys Ocean.
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Articles
Middle Jurassic palynology of the
southwest Tabas Block, Central-East Iran
Fatemeh Vaez Javadi
Accepted author version posted online: 03 Jul 2019
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https://doi.org/10.1080/01916122.2019.1637954
Abstract
Diverse and moderately to poorly preserved palynofloras occur in the lower Middle Jurassic
sediment of the Hojedk Formation in the Chahrekhneh, southwestern of Tabas, east central
Iran. The palynofloras comprise fifty-six species including spores (fifteen species allocated to
seven genera), various types of pollen (thirty species designated to sixteen genera),
dinoflagellate cysts (ten species belonged to three genera), and one acritarch species. Vertical
distribution of miospores allows erection within the Hojedk Formation of one biozone–
Klukisporites variegatus- Callialasporites trilobatus Assemblage zone– based on the first
observed occurrence (FOO) and the last observed occurrence (LOO) of selected taxa.
Moreover, vertical distribution of dinoflagellate cysts allows erection within this formation of
one biozone- Nannoceratopsis sp. cf. N. gracilis Interval zone. These biozones are compared
with palynozones from ± coeval strata in Iran and elsewhere. Abundance of ferns and
cycadophytes in parent floras implies that the host strata accumulated under a moist warm
climate during the early Middle Jurassic in this locality. Based on various data of ecogroups
in Chahrekhneh, it should be considered that there were several environments of upland,
warmer lowland, wetter lowland, rivers and delta. Furthermore, based on the occurrence of
dinoflagellate cysts it can conclude that Chahrekhneh located at the south coastal boundary of
the Iran Plate, along the Tethys Ocean.
KEYWORDS: - Middle Jurassic, Palynostratigraphy, Palaeoclimate, Tabas Block, Iran
... Vaez-Javadi & Mirzaei-Ataabadi (2006) conducted a study on Jurassic plant macrofossils from the Hojedk Formation in east-central Iran, which suggested that the formation was of Bajocian-Bathonian age. Those researchers also found evidence of a uniform palaeoclimate and environment in Iran during this time, which is consistent with the findings of Vaez-Javadi's later studies on Middle Jurassic flora and palynology in Iran (Vaez-Javadi, 2018, 2019. In her 2018 study, Vaez-Javadi focused on the Hojedk Formation in south Kouchekali, the south-western area of Tabas City, and found that the relative abundance of certain plant groups suggested a humid subtropical climate for that locality. ...
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