In Geological Society of America, Abstracts with Programs, vol. 35,
no. 3, p. 84.
POSSIBLE TRIASSIC-JURASSIC BOUNDARY SECTIONS, HARTFORD BASIN, EASTERN
WHITESIDE, Jessica H., Earth and Environmental Sciences, Columbia
Univ, Lamont-Doherty Earth Observatory, 61 Rt. 9W, Palisades, NY 10964-1000,
firstname.lastname@example.org and OLSEN, Paul E., Lamont-Doherty Earth Observatory,
Columbia Univ, 61 RT 9W, Palisades, NY 10964-1000
Examination of long-known outcrops plus two new cores in the Hartford
basin allow a comparison between probable Triassic-Jurassic boundary sections
of the latter basin with those better known from the Newark basin.
Gray, well-bedded strata of the uppermost New Haven Fm. beneath the Talcott
basalt at two exposures (Cinque Quarry, and Silver Ridge) and in two cores
(Silver Ridge) contain abundant conifer wood, shoots, and cones. That pollen
consisting only of Corollina has been identified at the Cinque Quarry (1,2)
strongly suggests that these strata are of Early Jurassic age. The sequence
of facies in the uppermost New Haven is extremely similar to those seen in
the northern Newark basin where the Triassic-Jurassic boundary may be cut
out by a tectonostratigraphic sequence (TS III-IV) hiatus (2).
Two candidate sections in the northern Hartford basin (where the Talcott
is lacking) are the Clathropteris locality in Holyoke (3) and the Rt. 91S
cut in Northampton (4). The former section looks remarkably like the complete
boundary section at Exeter in the southwestern Newark basin (2), where the
TS III-IV boundary is a correlative conformity. In both cases there is a
claystone with a "fern spike" dominated by Granulatisporites infirmus and
Converrucosisporites cameronii (3,4), both produced by the dipteraceous fern
Clathropteris meniscoides (3); and in both cases Triassic taxa are absent.
Either both represent the Triassic-Jurassic boundary or they represent only
a distinctive habitat of Clathropteris that in Exeter is by "chance" at the
Triassic-Jurassic boundary, although Clathropteris habitats themselves may
be a signal of events broadly around the Triassic-Jurassic boundary, such
as a "super greenhouse" effect. The Rt. 91 section contains the lowest limestone
of the Shuttle Meadow Fm. and an underlying thin red and purple mudstone sequence.
The latter superficially resembles the red Grist Mills section (2). At Exeter
and Grist Mills a modest Ir anomaly has been found (5) and clearly examining
these Hartford basin sections for a comparable geochemical tracer is the
1) Heilman, JJ. 1987. Jour. Sci. Ed. 25:8. 2) Olsen, et. al. 2002. G.S.A.
Spec. Pap. 356:505. 3) Cornet, B, Traverse, A. 1975. Geosci. Man 11:1. 4)
Fowell, SJ. 1994, Ph.D thesis, Columbia Univ., NY, 154 p. 50 Olsen, et. al.
2002. Science 296:1305.