Dinosaur tracks from the Jurassic Shemshak Group in the Central Alborz Mountains (Northern Iran)

Abstract

Abstract:The Shemshak Group includes alternating layers of coal-bearing shale and siliciclastic sediments in the Baladeh area in the central Alborz Mountains of northern Iran. A diverse and abundant Jurassic dinosaur footprint assemblage is now recognized in the group, which is Toarcian to Bajocian in age in the northern Baladeh. This is the first report of a diverse dinosaur ichnoassemblage from Iran that includes the footprints of sauropods. These tracks can be assigned to three groups of trackmakers: theropods, ornithopods and sauropods. Those of theropods are typically tridactyl in shape, their trackways reflecting bipedal movement. Theropod footprints are very abundant in both northern and western Baladeh. The studied theropod tracks themselves are divided into three major dimensional groups. The medium sized footprints (footprint length, 11-15 cm) are abundant and have a stride length, digit and pace angles like the coelurosaurs footprints and trackway. Theropod footprints were identified as similar to Schizograllator otariensis, Talmontopus tersi and Wildeichnus isp. Ornithopod footprints are tridactyl with rounded and thick toes and belong to bipeds. Some didactyl imprints were also observed. Skin imprints were well preserved in these footprints. The ornithopod tracks resemble Jiayinosorupus johnsoni, as well as Velociraptorichnus sichuanensis for didactyl footprints. Sauropod footprints found in the western part of Baladeh are assigned here to Eosauropus isp., which are pentadactyl pes imprints of a quadruped. The assemblage from Iran resembles similar associations from eastern Asia.Key words: Jurassic, Iran, Alborz Mountains, ichnology, Dinosaur. Materials and methodsThe geometry of the studied footprints was examind using the methods of Thulborn 1990. These dimensions are footprint length (FL), footprint width (FW), pace angulations (PA), stride (S), trackway width (TW) and digit length (DL). The shape of footprints and trackway patterns were mapped on the transparent papers. Some footprints were sampled; including six footprints of horizons 2-4 of the Royan section and two footprints of the uppermost layer of horizon 2 of the Bol-Yasel section. Four plaster casts prepared in the field from the well-preserved footprints of the Royan section include footprint numbers of f [11][12] in horizon 4 and 5a 1 from the horizon 5. These samples were deposited in the Geological Museum of the Department of Geology of the University of Zanjan, with code numbers GMZU09-40-49.

Geochemistry of siliciclastic rocks from the Shemshak Group (Upper Triassic–Middle Jurassic), northeastern Alborz, northern Iran: implications for palaeoweathering, provenance, and tectonic setting

“…The siliciclastic Shemshak Group (Up per Tri as sic-Mid dle Ju rassic) is one of the most ex ten sive lithostratigraphic units of the Iran Plate, wide spread across the north ern Alborz and East Cen tral Iran of the Ira nian plate (Tabas and North of Kerman; Fürsich et al, 2009). Nu mer ous stud ies have doc u mented lithostratigraphic, sedimentological and palaeontological aspects of the Shem shak Group (e.g., Seyed-Emami et al, 2006;Fürsich et al, 2009;Shekarifard et al, 2009;Zanchi et al, 2009;Moosavirad et al, 2011Moosavirad et al, , 2012Abbassi and Madanipour, 2014;Salehi et al, 2017). These stud ies have shown that the Shemshak Group is com posed largely of siliciclastic rock, lo cally reach ing up to 4000 m in thick ness.…”

Youngest Cretaceous dinosaur tracksite from the Middle East (Maastrichtian, Farrokhi Formation, Central Iran)

“…There is only a very sparse Mesozoic record of dinosaur tracks from Iran (Lapparent and Davoudzadeh 1972;Lapparent and Nowgol Sadat 1975;Ataabadi et al 2005;Abbassi 2006;Kellner et al 2012;Abbassi and Madanipour 2014;Abbassi et al 2015Abbassi et al , 2018. The bulk of the records is from the Lower and Middle Jurassic Ab-Haji Subgroup of the Shemshak Group of northern and Central Iran, and the uppermost Jurassic Ravar Formation of the Kerman area.…”

“…During a field survey in 2012, a dinosaur trampling site was discovered within the upper Campanian-Maastrichtian Farrokhi Formation and it was revisited and restudied in 2018. The aim of the current short note is the first report and scientific description of the site that supplements the sparse Mesozoic record of dinosaur tracksites from Iran (see Lapparent and Davoudzadeh 1972;Lapparent and Nowgol Sadat 1975;Ataabadi et al 2005;Abbassi 2006;Kellner et al 2012;Abbassi and Madanipour 2014;Abbassi et al 2015Abbassi et al , 2018, representing the youngest hitherto known occurrence. With our report, we also hope to stimulate further research on that topic in the area north of Khur where, in the future, additional and better-preserved tracks may emerge from the Farrokhi Formation.…”