Probing the deep critical zone beneath the Luquillo Experimental Forest, Puerto Rico

H. L. Buss*, S. L. Brantley, F. N. Scatena, E. A. Bazilievskaya, A. Blum, M. Schulz, R. Jimenez, A. F. White, G. Rother, D. Cole

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

43 Citations (Scopus)
357 Downloads (Pure)

Abstract

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 similar 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.

Original languageEnglish
Pages (from-to)1170-1186
Number of pages17
JournalEarth Surface Processes and Landforms
Volume38
Issue number10
Early online date17 Jul 2013
DOIs
Publication statusPublished - Aug 2013

Keywords

  • critical zone
  • drilling
  • corestones
  • regolith
  • weathering
  • WEATHERING RIND FORMATION
  • ANGLE NEUTRON-SCATTERING
  • URANIUM-SERIES ISOTOPES
  • LONG-TERM
  • RATES
  • MOUNTAINS
  • SOIL
  • CHEMISTRY
  • EVOLUTION
  • ROCKS

Projects

WEBB: USGS Water Energy and Biogeochemical Budgets

Buss, H. L., Scholl, M., White, A. F. & Shanley, J.

1/10/91 → …

Project: Research

File

LCZO: Luquillo Critical Zone Observatory

Buss, H. L., Brantley, S. L., Scatena, F. N., Silver, W., Plante, A., Willenbring, J., McDowell, W., Shanley, J., White, A. F., Scholl, M., Johnson, A., Jerolmack, D., Horton, B., Chapela Lara, M. & Moore, O. W.

1/10/1030/09/13

Project: Research

Cite this

Buss, H. L., Brantley, S. L., Scatena, F. N., Bazilievskaya, E. A., Blum, A., Schulz, M., Jimenez, R., White, A. F., Rother, G., & Cole, D. (2013). Probing the deep critical zone beneath the Luquillo Experimental Forest, Puerto Rico. Earth Surface Processes and Landforms, 38(10), 1170-1186. https://doi.org/10.1002/esp.3409