Arundel Field Notes #2: 4/22/01

[Tompaleo@aol.com]

As promised, the next in a continuing series of field notes from the wilds of 
suburban Maryland. I meant to write this almost a week ago but never managed 
to get the time to do it. Besides, in light of the new feathered theropod 
thread , I doubt I was missed ;-)

Conditions continue to improve both locally and at the site. Today's trip 
took place on a warm (60 degrees F at 9 AM) but cloudy-overcast Sunday 
morning that threatened rain until about noon. Upon arrival in country, the 
quarry had dried considerably in a weeks time, only a couple of the major 
erosion channels which transect the slope were still draining. This is 
typical from a hydrogeological standpoint as the Arundel Clay is referred to 
in the hydrogeological literature as the Lower Potomac Confining Layer. In 
other words the Arundel acts as a confining layer for the sandier Patuxent 
Fm. which is itself a major aquifer for the entire region. Similarly, the 
Arundel also separates the upper sandy Potapsoco Fm that is too, a major 
aquifer all the way up to Long Island New York! Naturally, after a period of 
heavy rains, or just after the spring thaw, water can be seen 'springing' out 
on the hillside where the Arundel-Patuxent contact is. This zone also is a 
zone of ongoing pyritization (diagenesis); pyrite pseudomorhphing after 
lignite, bone and siderite. So we have both primary pyrite or marcasite 
(pyrite's polymorph) and secondary pyrite and/or marcasite the downside to 
all this geochemistry is that this contact is one of the major producers of 
fossils at the site and I have found completely pyritized bones including a 
nice vertebra at times! Most times, due to my frequent visits to the site, I 
catch recently exposed material before it has had time to get that bad. 
Today however, there was nothing in this zone!  However, in the next erosion 
channel to the left of this zone, I noticed a number of shards of bone 
sitting on what I first though was the surface. After picking up these shards 
and probing around the area, I hit major bone that projected at an angle of 
about 30 degrees downward and approximately parallel to strike. In all, two 
large fragments measuring roughly 4 inches long each and ~1.5 inched in 
diameter were recovered. They are both still covered in matrix but they 
appear to be contiguous and that of a long bone. The specimens do not appear 
to be hollow and thus doubt at this time that it is of theropod origin. We'll 
see...
 Some of the outer cortical bone appears to be preserved along the shaft as 
well. I won't know more until I get it cleaned up. Unfortunately too, this 
specimen has some indication of pyrite rot.
By afternoon the clouds had burned away and the temps rose to the mid 80's. 
Time to strip! The bright sun really helps with the prospecting but after 
another 5 hours of prospecting, not much more was recovered and I received a 
slight burn for the effort!

I also noticed soon after arriving that someone else had been there during 
the week. The person's boot prints were all over the place as were pot holes 
all over the outcrop-from the person(s) illicit digging! I checked with a 
colleague to see if he had been out there that week, hoping it was he 
although the signs left were not characteristic of this individual, who 
indicated that he had not been there. It's those damnable poachers from a 
local rock club again! 

Got any claymores on you Josh?????????

I sickens me to think of what they are stealing and the fact that I just 
cannot spend the time on site like I used to, so these SOB's will get away 
with it.

So far, the returns have been lower than expected and usual, dino poachers 
not withstanding, but some items of interest for this trip include:

1) 1 Bernaissartia type "button" tooth. A rare find indeed and one of only 
about 1/2 dozen or so that I have or have seen.

 *** Note. This was once referred to as Ptychodont tooth on my now very 
outdated web page and based on erroneous information. Most people that have 
seen this specimen tend to go with Bernaissartia. So I will.

2) 1 Nodosaur tooth crown: _Priconodon_crassus_.
3) 1 Fragment of turtle scute cf. 'Glyptops caeladus'
4) 1 very fragmentary and worn tooth crown, indet.
5) 1 fragmentary croc tooth (conical type) cf. 'Goniopholis affinis'
6) 6  Cones of a taxodiaceous conifer
7) A number of nondescript bone fragments.

Not too shabby but I have done better. Hope next week's trip is more 
productive.

Thomas R. Lipka
Paleontological/Geological Studies
Tompaleo@aol.com