Geopic of the week: Dinosaur tracks in Arkansas

IMAG0084

Pictured above are tracks of an Acrocanthosauras Atokensis: a bi-pedal predatory dinosaur.  The tracks were discovered in 2011 in a gypsum mine north of Nashville Arkansas by workers at the mine.  It is one of two such “dinosaur trackways” – as they are called – that have been discovered in this mine;  The first one was unearthed in 1983.  Dinosaur tracks are not common in Arkansas as most of the rocks here, which are very old, were deposited long before the dinosaurs existed. 

The rocks where the tracks are preserved were deposited in the early Cretaceous Period sometime between 145 and 100 million years ago.  At that time, the area south of the Ouachita Mountains was a broad coastal plain and the Gulf of Mexico waters reached all the way to southern Arkansas.  A variety of dinosaur species tracks, both herbivore and carnivore, have been discovered in these trackways, indicating that the coastal area at that time was quite the dinosaur stomping ground. 

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One thought on “Geopic of the week: Dinosaur tracks in Arkansas

  1. Jim Liles

    Hutto’s geoblog is great. And the geo. mapping you (&USGS) have done along Buffalo River is outstanding. This comment is offered, in reference to the USGS Geological Map of the Maumee Quadrangle (2010, Turner & Hudson) — prompted by my reading of Hutto’s blog posted Oct 2, 2013:
    “Most of the quads mapped by our agency did not include the higher river terrace levels above the (Buffalo) River — some as high as 200 feet!”
    I majored in geology (Cornell ’59) and have continued my interest over 36 years with the national park service and subsequent 16 years of retirement. I have continued to volunteer in the construction of the Buffalo River Trail, a project I began in 1983. (I brought Kenneth L. Smith “out of NPS retirement” to assist with the trail’s layout, beginning 1985.) Early this year I began construction of the BRT across the pronounced meander bend, T16N, R16W, river mile 47-48 (measuring up from White River.) For at least 1/4 mile of trail route, spanning elevations between 800 and 760 feet above sea-level, I have encountered numerous water-worn, much-weathered clasts within a sandy matrix, or loose within the clayey soil — occasionally red clay without rock. These are pebble to fist-sized clasts of sandstone, generally exhibiting a red ‘weathering rind’ of precipitated iron. The river level at the point of the bend is about 530 feet above sea level, so the water-worn pebbles & cobbles indicate a former river level as much as 270 feet above present.
    Incidentally, last January, I developed a nomination for this unnamed river bend and its associated bluff to be called Branner Bend & Branner Bluff, in honor of Dr. John C. Branner. (His work in this area is classic, for example, his identification and description of the “Tomahawk Faults” and associated formations displayed in the subject bluff, pp. 45,46, Annual Report of the Geological Survey of Arkansas for 1892.) The USGS Geographic Names Office place the nomination under review, but the office of Superintendent, Buffalo National River, declined to support the nomination, as it was not a name “of local origin” or “in local use.” Perhaps the Arkansas Geological Survey would like to revive that nomination.

    Reply

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