Kukpowruk River

Introduction	Geology	Northern Alaska Map			Kokolik River

 

The map on the right shows the localities along the Kukpowruk River sampled both by Smiley (reported in Smiley 1969a), Spicer and Herman (1996) and by Bob and Andrew Spicer in 1998. Click on the locality numbers to see further details of the sites and the fossil floras.
The flora in general consists of 57 species. Some of them are long-ranging and are found throughout the Kukpowruk and Corwin Formations, others are more common or found exclusively in particular parts of the sequence. Based on plant fossil distribution the flora can be divided into three floral suites. The first suite comprises plants from the Torok and Kukpowruk Formations and the lower part of the Corwin Formation; the second one, from the middle part of the Corwin Formation (localities 96-23 to 97-27). The third suite comes from localities 98- 17–22 and from Smiley's locality 59 and lies within the uppermost bentonite-rich part of the Corwin Formation. The first suite is characterised by an abundance of Arctopteris, diverse cycadophytes (Nilssonia is represented by four species together with Anomozamites, Heilungia and Taeniopteris) and the presence of Parataxodium. Sphenobaiera leaves are rare here and angiosperms have not been found. The second suite differs from the first in the abundance of Sphenobaiera and Desmiophyllum leaves, by the presence of Phoenicopsis and Pagiophyllum triangulare and by the appearance of rare angiosperms. Arctopteris and cycadophytes are rarer in the second suite. The differences between the first two plant suites (except the presence of rare angiosperms in the second one) are subtle. The overall composition and the distribution of predominant plants indicates that these two suites may belong to a single stage of floral evolution within the region but represent different parent communities/ depositional environments. We collectively refer to these two plant suites as the Kukpowruk Flora. The Kukpowruk Flora in general is similar to a very rich (more than 150 species) early–middle Albian flora of the Buor-kemuss type of north-eastern Russia.

The Buor-kemuss type flora is known from several localities, the richest of them are those in Buor-kemuss Formation of the Zyrianka Coal Basin (Kolyma River Basin: Prynada, 1938; Samylina, 1964, 1967), upper subformation of the Ainakhkurgen Formation and Chimchememel Formation of the Ainakhkurgen Depression (Bolshoi Anui River Basin: Filippova, 1975; Samylina, 1976), Umkuveem, Marakveem and Irvunei formations of the Umkuveem Depression (Yeropol River Basin: Filippova, 1975; Samylina, 1976) and middle and upper subformations of the Omsukchan Formation and Toptan Formation of the Omsukchan area (Magadan district: Samylina, 1976). Almost all plant species comprising the Kukpowruk Flora are also typical for the floras of the Buor-kemuss type listed above.

A presumably Albian flora from the Tyl' Formation of the Torom Trough (west of the Okhotsk Sea coast) is similar in composition to the Kukpowruk Flora: about 25 fossil taxa occur in both floras including Mirella sp., Arctopteris rarinervis (= A. tschumikanensis E. Lebedev), Nilssonia magnifolia, N. menneri, Podozamites eichwaldii, Lindera jarmoljukii, and the genera Cissites and Kenella (Lebedev, 1974).

In northern Alaska the flora from the lower part of the Killik Tongue is similar to that of the Kukpowruk and Corwin formations (Smiley, 1969a; Spicer et al., 1992). Pityophyllum and Podozamites are particularly abundant in both and in riparian facies large-leafed ginkgos are common.

Fontaine (in Ward, 1905) reported a small fossil flora from the vicinity of Cape Lisburne which seems to represent the same type of flora preserved along the Kukpowruk River.

The third Kukpowruk River plant suite (localities 98-17–98-22), designated the Corwin Flora, consists of 22 species: Gleichenia sp. cf. G. pseudocrenata E. Lebedev, Equisetites sp., Birisia ochotica Samylina, Birisia sp. cf. B. oerstedtii (Heer) E. Lebedev, Ctenis sp., Taeniopteris (?) sp., Ginkgo ex gr. adiantoides (Unger) Heer, Ginkgo ex gr. concinna Heer, Sphenobaiera ex gr. biloba Prynada, Desmiophyllum sp. (Sphenobaiera?), Podozamites spp. (isolated leaves), Pityophyllum sp., Cephalotaxopsis intermedia Hollick, Cephalotaxopsis sp., Scheffleraephyllum venustum (Philippova) Philippova, Platanus louravetlanica Herman, Platanus sp., platanoid leaf fragments, Dicotylophyllum (Cissites?) sp., Dicotylophyllum (Viburniphyllum?) sp., and Dicotylophyllum spp.

In north-eastern Russia the closest equivalent of the Corwin Flora is the latest Albian–early Cenomanian Grebenka Flora from the right bank of the Anadyr River (Shczepetov et al., 1992; Herman, 1999). Almost all species from the Corwin Flora are present in, and typical for, the Grebenka flora, and some of them (Araucarites sp. cf. A. anadyrensis Kryshtofovich, Scheffleraephyllum venustum (Philippova) Philippova, Platanus louravetlanica Herman, Grebenkia anadyrensis (Kryshtofovich) E. Lebedev) are known exclusively from this flora and its equivalents within north-eastern Russia. In Alaska the Corwin Flora taxa are also found in the early Cenomanian bentonite-rich Niakogon and Upper Killik Tongues of the Chandler Formation.