Does your (sub)horizontal, unbranched burrow with a cylindrical or a ridge-like appearance have a passive or an active filling?

1. passive fill (in case of subrecent traces: NO fill)
2. active fill
3. both or cannot be determined. (Click on the ichnogenera below to get more information about their ichnospecies. Please allow for pop-up windows):
• Ovatiichnum (May also occur as surface trace (track, trail, impression, etc.))
• Ptychoplasma (May also occur as surface trace (track, trail, impression, etc.); ichnogenus includes ornamented ichnospecies)