DISTINGUISHING TRUE TRACKS FROM UNDERTRACKS AND OVERTRACKS THROUGH INTEGRATION OF MORPHOLOGICAL, SEDIMENTOLOGICAL, AND PHOTOGRAMMETRIC MODELLING, DINOSAUR STATE PARK, ROCKY HILL, CONNECTICUT

Early Jurassic Eubrontes tracks and at Dinosaur State Park (DSP) in Rocky Hill, Connecticut are investigated using morphological observations, sediment fill patterns, and 3-D photogrammetry to distinguish and visualize true tracks from undertracks and overtracks. DSP contains over 750 primarily Eubrontes tracks that include 54 distinct trackways of which 14 contain footprints on multiple stratigraphic surfaces. Attributes of the outcrop permit the examination of: (1) trackways that cross from one stratigraphic bed onto another, (2) individual tracks that are truncated along the edge of one bed and can be viewed in cross-section and on the underlying bed surface, and (3) partial removal of one bed that permits a portion of the track to be viewed on the underlying bed. Our 300+ million point-cloud model and visualizations identify subtle topographic variations and support measurement of track dimensions (e.g. depth, volume, area) and spatial analyses that are difficult to determine by hand, yet further quantify direct comparisons of true tracks, overtracks, and undertracks.

Based on observations from tracks and trackways that occur on more than one stratigraphic surface, true tracks at DSP have: (1) better preservation of anatomical features such as claw marks and toe pads, (2) generally deeper and narrower track dimensions, and (3) sediment layers that are not vertically disturbed but rather thicken into the track and show evidence of lateral and/or vertical fill. We note that tracks at DSP do not contain skin impressions that are often used to identify true tracks.

By recognizing true tracks based on observed morphology and sedimentology we assign associated true tracked surfaces to trackways identified in our digital model. This supports ongoing analyses to determine which and how many trackways were registered penecontemporaneously. Such groupings would be helpful in reevaluating whether contemporaneous trackways display preferred orientations (to date not recognized at DSP) and to assess the value of new digital track measures (especially depth and volume). However, these measures must be interpreted cautiously as they are strongly influenced by any remaining infilling of the track after its registration and excavation.