USGS11606.65 Indet. MA94


USNM 406623



Locality Map

Arctic Slope of Alaska locality USGS 11606, north of Maybe Creek. This locality is a bluff approximately 10 m high on the east side of an unnamed tributary of the Price River.  The predominant lithologies are bentonitic clays overlying a silty sandstone capped by coal beds up to 2 m thick, which are in turn overlain by a white-gray medium-grained sandstone.  Irregularly dispersed throughout the clay are nodules and sheets of ferruginous limestone (sideritic) which, although light gray when fresh, weather to a rusty brown.  With the exception of some poorly preserved plant matter in the upper sandstones, and impressions of platanoid leaves in the power sandtsones, the plant material is confined to these fine-grained iron-rich nodules and is preserved as impressions totally lacking cuticle. There is little evidence of post-mortem decay but many leaves are penetrated by vertical fossil rootlets. Platanoid leaves are most common in siltier/sandier facies. The uppermost coal surface supports several in situ tree bases each of which is approximately 20 cm in diameter.

Latitude: 69.528329 °N

Longitude: -153.887128 °W


Leaf:  simple; symmetrical (?); wide elliptic, bilobed; apex emarginate, apices of lobes rounded; base missing; margin entire; venation pinnate camptodromous with the brochidodromous secondary veins; midvein moderate, straight; secondary veins moderate with somewhat irregular courses including recurved, straight, sinuous, and curving uniformly in an apical direction, arising from primary vein at an angle of 45-50°, branching once near margin but sometimes branching as near to the midvein as one-third of the distance between the midvein and the margin, forming loops that join superadjacent secondary at an acute angle; third and higher order loops also present; intersecondary veins present, complex; tertiary veins reticulate to irregularly percurrent, often simple, straight, sinuous or convex but sometimes branched one or more times to form a reticulate pattern in places; fourth order veins forming random reticulate patterns.


Although an unreliable character in such 'Liriodendropsis'-type leaves, the lamina shape is different from all other similar forms described here in that the lobes are poorly developed with respect to the rest of the lamina.  The magnoliidean venation is clearly similar to that of specimen USGS 11606.22 (Form MA88) for which lamina shape characters are sparse but the venation differs from that specimen by being less well organized.