Locality
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
Description
Leaf: simple; symmetrical; very wide ovate; apex missing; base lobate; margin irregular serrate, teeth with acute apical angles and rounded sinuses; petiole normal; venation imperfect suprabasal marginal actinodromous; pectinal veins somewhat weaker than the midvein, arising at angles of 70-90°, markedly curved towards the apex; pectinal abmedials arising at angles of 50° near the margin becoming more obtuse to 80° near the base, curved often branched abmedially sometimes repeatedly especially near the base; superior secondary veins moderate uniformly curved, angle of divergence from the midvein 35-40°, nearly uniform, often forking a number of times near the margin; tertiary veins percurrent, usually slightly convex, often forked, angle of origin on both the ad- and abmedial sides of secondaries acute or 90°, tertiary angle to the midvein obtuse, remaining approximately constant except for the tertiaries between the pectinal abmedials which vary from acute at the base to obtuse near the apex; fourth order veins orthogonal, percurrent sometimes forked and distinct.
Remarks
This leaf form is apparently very close to specimens USGS 11606.67 (form HAPLTL120) and USGS 11606.35 (form HAPLTL116) and differs only in that it has less coarse dentition.