USGS11606.17 Indet. MA87


USNM 406616



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 sandstones, 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; elliptic (?); apex missing; base decurrent; margin entire; venation pinnate camptodromous, poorly developed brochidodromous, primary midvein more or less straight, moderate; secondary veins departing from the midvein at an angle of 50-70° with no appreciable change in angle along the length of the midvein, moderate, uniformly curved, often dichotomizing at or on the marginal side of a point midway between the midvein and the margin, subsequent dichotomies may also be present, the more basal branches becoming curved and joining the superadjacent branch at an acute, loop shape and size variable; tertiary veins tending to be convex, unbranched to reticulate, oriented oblique to primary vein, at the abmedial end of intercostal region to approximately 90° at the midvein.


The venation of this leaf displays a general lack of organization. There is a tendency towards brochidodromy but this is poorly developed except near the base.  Not all the secondaries are of the same thickness and the weaker ones could be interpreted as intersecondaries.  The basal secondaries loop to join the superadjacent secondaries in a manner quite distinct from the other secondaries.  The penultimate basal secondaries therefore appear to be very poorly developed pectinal veins.