Aybugir Formation

Aybugir Fm

Period:

Cretaceous

Age Interval:

Berriasian - lower Hauterivian, U3

Province:
Ustyurt-Sultanuzdag

Type Locality and Naming

Along the Aibugir Uplift. N. Turkmenistan. L.N. Amaniyazov, 1968 (62, p.119).

Synonym: Aibutir Suite, Айбуиргская св.

Lithology and Thickness

Two packages are distinguished.

Upper - dark gray, greenish-gray sandstones with layers of siltstone (aleurolites) and clays (Thickness 26-80m).

Lower - gray, dark gray clays with subordinate layers of red-brown and greenish-gray sandstones and siltstone (aleurolites) (Thickness 34-110m);

Lithology Pattern:

Sandstone

Relationships and Distribution

Lower contact

The Aybugir Fm transgressively overlies the Jurassic

Upper contact

It is conformably overlain, or with signs of erosion, by the Lower Cretaceous (363; 383; 506)

Regional extent

E. Ustyurt, S. Pre-Aral. Boreholes. Stratotype not specified. Type section Along borehole 23 (north of the Aibugir Uplift). It is an analog of the Nurumgur Fm of southern Turkmenistan (471).

GeoJSON

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Fossils

The upper package - predominantly foraminifera with calcareous and sandy shells: Hormosina turkmenica Suleim., Lenticulina poljkovi Kurb., L. rodovilski Kurb., L. (Astacolus) coriphorus (Chalil.), and others, ammonites - Kaschpurites cf. fulgens Trd., K. sp.; marine ostracods - Postheroprocythere propria Shar., Lubimovina denticulata (Shar.), L. neocomiensis Lub., Malzevia pellucida (And.), a complex of spores and pollen.

The lower package contains, predominantly, agglutinated foraminifera - Paammosphaera sugaityenensis Suleim., Lagenammina bartensteini Mjatl., Lituotula incerta Franke, Reophax crespinae Mjatl., Adelungia aibugirensis Suleim., Hormosina turkmenica Suleim., Haplophragmoides princeps Kurb. et Mam., Cribrostomoides vulgaris Mam., Ammobaculites quadriloculinus Mjatl., Trochammina khoskudukensis Kurb. et Mam.; marine bivalve mollusks - Buchia volgensis Lah., B. cf. crassicollis (Keys)., marine ostracods - Praelongytheria aff. acuta (Quents) and a complex of spores and pollen.

Age

Along other data, it is assigned to the Kimmeridgian–Tithonian (62), to the Kimmeridgian–Valanginian (137), or to the Jurassic (463).Along A.M. Akramkhodjaev and others (47), in the modern interpretation the Aybugir Fm represents the eroded part of the Chimbay Fm. It is assigned to the Berriasian—corresponding to the Shakhiakhtin Fm—and the Baiterek Fm corresponds to the Aybugir Fm.

Age Span:

Beginning stage:

Berriasian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

140.40

Ending stage:

Hauterivian

Fraction up in the ending stage:

0.5

Ending date (Ma):

129.55

Depositional setting

Depositional pattern:

Additional Information

Compiler:

I.M. Abdazimova, V.V. Kurbatov – In: GeoGPT translation of: “Abduazimova, Z.M. (Ed.), 2001. Stratigraphic Dictionary of Uzbekistan. IMR (Institute of Mineral Resources), Tashkent, 580 pp. (In Russian)”