The article Gav Rymill (See his posting reproduced below.) wonders about is as follows:
Feather-Like Impressions in a Theropod Resting Trace from the lower Jurassic of Massachusetts, by Gerard Gierlinski, published in The Continental Jurassic, Michael Morales, Editor, 1996, Museum of Northern Arizona Bulletin 60.
And, yes, there has been much discussion of this on this list, some of it recent.
In short, Paul Olsen, possibly the most experienced expert on tracks and other ichnites of the Newark Super Group, has studied these traces from the Lily Pond Quarry in Massachusetts (Portland Formation, Lower Jurassic) first-hand and in depth. (Amherst College, Massachusetts item catalogued as AC 1/7) He is convinced (personal conversation, 1998) that the traces Gierlinski interprets as possible feather impressions have a much less spectacular explanation.
I have a sizeable piece of Newark Super Group substrate with a dinosaur track and with impressions that seem identical to those in the specimen Gierlinski and Olsen have discussed, and those on my sample seem to have been made by some type of vegetation adrift in shallow water and brushing against the very fine-grained bottom sediment.
Personally, I would be delighted if AC 1/7 should contain theropod feather impressions -- and, in fact, believed them to be such on initial exposure to Gierlinski's paper -- but I am now 100% certain his interpretation is not tenable.
I hope this helps,