The breccia I've seen on the surface in central Texas, including at CWAN, is usually one of three types:
1) Cemented collapse of a old cave that is now exposed at the surface. These are scattered randomly throughout the Texas karst. 2) Breccia along a fault, where chunks of rock broke off as the rock mass on either side moved against the other side, and then the chunks were later cemented together. A nice example of such breccia is along the Haby Crossing Fault behind the volunteer office at Government Canyon State Natural Area. 3) Colluvial breccia, where gravity pulled down part of hillside or cliff and was later cemented together, is much less common and more widely scattered in Texas. None of these breccias match the broad, extensive, deposits Bruce describes for the Yucatan. I don't recall seeing those when I was there and would want to see them in the field before speculating on their origin. George From: Cave Without a Name [mailto:[email protected]] Sent: Wednesday, January 27, 2010 9:53 AM To: [email protected] Cc: [email protected] Subject: Re: [Texascavers] breccia That same sort of breccia is on the CWAN property. I doubt that it's the KT boundry but it is a mystery. If any of you geologists want a sample I'll show you where it is. I'm pretty sure it's in the upper part of the Lower Glenrose formation. Mike Burrell Manager Cave Without a Name ----- Original Message ----- From: [email protected] To: [email protected] Sent: Wednesday, January 27, 2010 8:42 AM Subject: [Texascavers] breccia Mystery rocks? Alien footprints? Pardon me, but it looks like plain old breccia to me. See: http://geology.about.com/od/rocks/ig/sedrockindex/rocpicbreccia.htm Louise No question about it being breccia, I just want to know how it happened. How could such a cake mix slurry of broken chunks get embedded in conventional limestone then get spread in a thin flat layer across a wide area? The relative hardness could well be an unrelated issue. Sleazel _____ No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.427 / Virus Database: 271.1.1/2642 - Release Date: 01/24/10 07:33:00
