USGS11606.46 Indet. MA91


USNM 406620



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; very wide obovate, with one lateral apical lobe on each side; lobe apices obtuse; base missing; margin entire; venation pinnate camptodromous with brochidodromous secondary veins; primmary midvein more or less straight, moderate; secondary veins weak, angle of divergence from midvein varying from wide acute near base to moderate acute at apex, straight or slightly curved, forking once, exmedial branch looping back to meet admedial branch at an acute angle, the admedial branch continuing to loop meeting superadjacent secondary at an acute angle, composite intersecondary veins present; tertiary veins depart from the secondaries at varying angles, random reticulate, third and fourth order loops present at margin, ultimate loops tending to form intramarginal vein; second, third, and fourth order veins all weak and poorly differentiated.


A striking feature of this leaf is the lack of organization and development in the venation.  This disorganization coupled with the entire margin, pinnate festooned brochidodromous venation, and intersecondary veins suggest an affiliation with the Magnoliidae.