Probing the deep critical zone beneath the Luquillo Experimental Forest, Puerto Rico
Article first published online: 30 APR 2013
Copyright © 2013 John Wiley & Sons, Ltd.
Earth Surface Processes and Landforms
How to Cite
Buss, H. L., Brantley, S. L., Scatena, F. N., Bazilievskaya, E. A., Blum, A., Schulz, M., Jiménez, R., White, A. F., Rother, G. and Cole, D. (2013), Probing the deep critical zone beneath the Luquillo Experimental Forest, Puerto Rico. Earth Surf. Process. Landforms. doi: 10.1002/esp.3409
- Article first published online: 30 APR 2013
- Accepted manuscript online: 25 FEB 2013 01:35AM EST
- Manuscript Accepted: 31 JAN 2013
- Manuscript Revised: 22 JAN 2013
- Manuscript Received: 20 FEB 2012
- US Geological Survey's Global Change Program, the National Research Program (NRP), and the Water Energy and Biogeochemical Budgets Program (WEBB) as well as from the NSF-Luquillo Critical Zone Observatory. Grant Number: NSF EAR-0722476
- National Science Foundation. Grant Number: DMR-0944772
- OBES. Grant Number: DE-FG02-05ER15675
- critical zone;
Recent work has suggested that weathering processes occurring in the subsurface produce the majority of silicate weathering products discharged to the world's oceans, thereby exerting a primary control on global temperature via the well-known positive feedback between silicate weathering and CO2. In addition, chemical and physical weathering processes deep within the critical zone create aquifers and control groundwater chemistry, watershed geometry and regolith formation rates. Despite this, most weathering studies are restricted to the shallow critical zone (e.g. soils, outcrops). Here we investigate the chemical weathering, fracturing and geomorphology of the deep critical zone in the Bisley watershed in the Luquillo Critical Zone Observatory, Puerto Rico, from two boreholes drilled to 37.2 and 27.0 m depth, from which continuous core samples were taken. Corestones exposed aboveground were also sampled. Weathered rinds developed on exposed corestones and along fracture surfaces on subsurface rocks slough off of exposed corestones once rinds attain a thickness up to ~1 cm, preventing the corestones from rounding due to diffusion limitation. Such corestones at the land surface are assumed to be what remains after exhumation of similar, fractured bedrock pieces that were observed in the drilled cores between thick layers of regolith. Some of these subsurface corestones are massive and others are highly fractured, whereas aboveground corestones are generally massive with little to no apparent fracturing. Subsurface corestones are larger and less fractured in the borehole drilled on a road where it crosses a ridge compared with the borehole drilled where the road crosses the stream channel. Both borehole profiles indicate that the weathering zone extends to well below the stream channel in this upland catchment; hence weathering depth is not controlled by the stream level within the catchment and not all of the water in the watershed is discharged to the stream. Copyright © 2013 John Wiley & Sons, Ltd.