Hello,
Sandstone pipes that are very similar, in some cases almost identical to those in the Carbonifeous of Arkansas, occur in Tertiary sandstone of Studland, Dorset, England. You may or may not know about these, but I mention them as they might be of interest.
See Website http://www.southampton.ac.uk/~imw/Studland-Tertiary.htm
or Google: Studland geology sandstone pipes
and browse through the webpage (note that there are other Studland webpages, but this is the Studland-Tertiary page.
The pipes at Studland have long been known and have been described by Arkell back in the 1940s. . They occur beneath a lignitic, almost coaly bed, with abundant plant material. Below high tide sea-level the pipes consist of pyrite, but above sea -level when oxidised, the limonite or goethite cements the sandstone.
I am afraid that I am not familiar wth the Arkansas details and do not know whether the pipes there are associated with pyrite and plant debris beds.
Office of the State Geologist Blog 
Hello,
Sandstone pipes that are very similar, in some cases almost identical to those in the Carbonifeous of Arkansas, occur in Tertiary sandstone of Studland, Dorset, England. You may or may not know about these, but I mention them as they might be of interest.
See Website
http://www.southampton.ac.uk/~imw/Studland-Tertiary.htm
or Google: Studland geology sandstone pipes
and browse through the webpage (note that there are other Studland webpages, but this is the Studland-Tertiary page.
The pipes at Studland have long been known and have been described by Arkell back in the 1940s. . They occur beneath a lignitic, almost coaly bed, with abundant plant material. Below high tide sea-level the pipes consist of pyrite, but above sea -level when oxidised, the limonite or goethite cements the sandstone.
I am afraid that I am not familiar wth the Arkansas details and do not know whether the pipes there are associated with pyrite and plant debris beds.
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