Trace Fossil?

[pleft]

Looks like the trace of some kind of worm to my uneducated eye - any ideas?

Found near Mahurangi, New Zealand. I believe the stratified cliffs there are limestone.

Thanks!

Edited July 11, 2012 by pleft

[painshill]

Casts of serpulid worm tubes maybe?

[erose]

Casts of serpulid worm tubes maybe?

Serpulids (Tube worms like the feather dusters) leave shell material behind. These are most likely feeding traces. They wander about gathering up all the good bits in the sediment. They could have been any of a number of critters.

[Auspex]

I think they are, as you suspect, in-filled burrows, since the material is the same within and without their forms.

It's an attractive ichnofossil; the pattern is fascinating!

[pleft]

Yes, I agree they look like infilled burrows or tracks. They don't appear to have any 'casing' such as a tube-worm might leave.

In an online field guide I found the following:

Mahurangi Limestone

Portland Quarry is located on a large block of Oligocene, fine-grained Mahurangi Limestone, which is one of the most dominant units in the Northland Allochthon. Fossil foraminifera and nannofossils indicate a late Oligocene age (late Whaingaroan-Duntroonian) and a deep bathyal paleodepth in an oceanic setting. It accumulated as pelagic foram nanno ooze on the floor of the Pacific Ocean.

Mahurangi Limestone is typically moderately to well-cemented, sheared and tectonically-deformed, argillaceous micritic limestone, blue-grey when fresh, but rapidly weathering to a distinctive, light creamy-white colour. Exposure are often massive and thoroughly homogenised by bioturbation, although bedding or lamination can occasionally be discerned. Lenses and intercalations of thin, graded calcareous sandstone, glauconitic sandstone and rippled fine sandstone are locally conspicuous (Isaac et al., 1994).

Mahurangi Limestone is typically composed of planktic foraminifera (up to 50%) set in a nannofossil-rich micritic matrix, with minor radiolaria and sponge spicules, and fine silt-sized quartz, clays and other terrigenous matter. Macrofossils are extremely rare (e.g. deep-water bivalve Parvamussium), but trace fossils are reasonably abundant. The most common ichnotaxa are Zoophycos and Phycodes/Planolites. At Portland Quarry a wide variety of large and small Zoophycos can be found. Several large ‘Paramoudra’ concretions, developed around simple, non-branching burrows have been seen here.

Source: http://cdn.onlinehosting.co.nz/~gsnz/file_downloads/fieldtrip/MP112B_FT1.pdf

The find was not at Portland Quarry, however.

Edited July 11, 2012 by pleft

[abyssunder]

It looks close to Planolites/Phycodes ichnofossils.