Sumsar-Paleog Fm
Type Locality and Naming
The Fergana Depression and Tajik Depression. Stratotype in the area of the city of Isfara. Hypostratotype in the area of the Rishistan folds along the Sarykamyshsai (281). Named after the river Sumsar, Fergana Valley. O.S. Vyalov, 1935 (155, p.280).
Synonym: Sumsarskaya Suite, Сумсарская св.
Lithology and Thickness
Maroon clays with subordinate red-colored sandstones, siltstones, shell limestones. K.P. Kalitsky divided it into three lithological horizons "p", "q", "r". Thickness is up to 90m.
Relationships and Distribution
Lower contact
The suite conformably, with slight erosion, overlies the Upper Eocene Khanabad Fm
Upper contact
It is overlain with erosion by the Maylisay Fm. To the west of the Isfara River, marine deposits of the Sumsar-Paleog Fm are facially replaced by continental red beds, forming a single Lower Tien Shan Gr with overlying alluvial-proluvial red beds of the Miocene Maylisay Fm.
Regional extent
At the exit from the Fergana Depression, this series dips into the Tashkent-Hungry Steppe trough, where it corresponds to the Chulin Fm. R.K. Makarova, B.I. Pinhasov (162; 281) correlated it with the Sarbatyr suite of the Kyzylkum. In some places in the Tajik Depression, South-West Gissar, and in the Chatkal-Kurama, the Lower Oligocene part of the Sumbar suite is absent and marine deposits of the Lower Miocene lie directly on the Upper Eocene or older formations.
GeoJSON
Fossils
R.K. Makarova (281), B.I. Pinhasov, R.K. Makarova (162) in the section of the Sumsar-Paleog Fm, from bottom to top, distinguished five lons (faunal layers): 1 - Pycnodonta sewerzowi, 2 - Ostrea pygmaea, 3 - Liostrea Korobkovi and Amphidonta ferganensis Mica, 4 - Amphidonta ferganensis, Amphidonta galleata, 5 - Pitar bajsunica. The first and second lons (horizon "p" and lower parts of horizon "q") correspond to the Rupelian stage of the Oligocene. The third lon (middle part of horizon "q") - Chattian stage of the Oligocene. The fourth lon, including the upper parts of horizon "q" and horizon "p", and the fifth lon, which belongs to the latter, correspond to the Lower Miocene.
The suite contains marine bivalve mollusks Nucula comta Goldf., Ioldiella chadumica (Korob.), Pinna endeterminata Sand., Ostrea pygmaea Vial., O. syathula Lam., Miocardiopsis ustjurtensis Iljina, Abra sordenfrei Ander., Thracia speyeri Koen., Th. faba Sand., Amphidonta ferganensis Mica Mak., Amfidonda ferganensis Rom., A. galleata Rom., Pycnodonta sewerzovi Rom., Pitar baisunica Varens. and others; gastropods - Drilia longa Luk., Surcula sokolovi Bajar.; foraminifera - Anomalina munda munda N. Byk., Cibicides macrurus N. Byk., C. tschagalaensis Korob., Globigerina hadumica N. Byk., Porosononion dendriticus Chalil.; ostracods - Cytherelloidea probata Mand., C. vollaris Mand., C. entermedia (Reuss.).
Age
Depositional setting
Additional Information
R.M. Davidzon et al. (162) divided the Sumsar-Paleog Fm of the Tajik Depression into the Sangalak and Shurysay horizons and attribute them to the Oligocene. In this case, they are distinguished as independent suites – Shurysay Fm in Surkhandarya, Kyzylchin Fm in South-West Gissar, Tashsay Fm on the Angren Plateau. The same picture is observed in the Kyzylkum. This indicates a constant increase in transgression, which began in the second half of the Early Oligocene and reached its maximum in the Early Miocene.