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Figure 1. Location map of northeastern Puerto Rico and the three rivers studied. These watersheds all drain the Luquillo Experimental Forest (LEF). Cross-valley core sections are denoted by tick marks and channel cross sections are denoted by filled circles. Note different scales used on the inset maps

Figure 1. Location map of northeastern Puerto Rico and the three rivers stu...

Published: 01 December 2000
Figure 1. Location map of northeastern Puerto Rico and the three rivers studied. These watersheds all drain the Luquillo Experimental Forest (LEF). Cross-valley core sections are denoted by tick marks and channel cross sections are denoted by filled circles. Note different scales used on the inset
Image
A, B: San Lorenzo batholith rocks (SLB; Rogers et al., 1979) underlie the Rio Guayanés (RG) watershed (Puerto Rico). Quartz diorite and granodiorite predominate (72% of drainage area), followed by metavolcanics (8%) and diorite (2%). Quaternary alluvium covers the remainder (18%). Stream elevation does not change significantly until a narrow gorge, where the stream drops to a low-relief alluvial plain. Samples collected in a small tributary branch are shown as negative distance. C: Mud increases downstream. D: Relative proportions of secondary minerals (kaolinite and halloysite) increase downstream, while primary minerals (quartz, K-feldspar, plagioclase, and hornblende) generally decrease down transect. E, F: Ca (E) and Na (F) concentrations observed in mud (right panel) are significantly higher than those observed in saprolite, but values are similar to those observed in rindlets from Luquillo Experimental Forest (LEF), northeast Puerto Rico (left panel).

A, B: San Lorenzo batholith rocks (SLB; Rogers et al., 1979 ) underlie the...

Published: 12 July 2018
in rindlets from Luquillo Experimental Forest (LEF), northeast Puerto Rico (left panel).
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Chemical weathering indices. A: Rio Guayanés (RG, Puerto Rico) sediment is much less weathered than saprolite, comparable to values observed in rindlets within Luquillo Experimental Forest (LEF; Turner et al., 2003) when plotted on A-CN-K space (Nesbitt and Young, 1984). B: RG and LEF geochemical M-F-W (mafic-felsic-weathered) plots (Ohta and Arai, 2007) deconvolve source rock lithology and weathering signals in sediments and soils. RG muds again overlap with LEF rindlets and plot as significantly less weathered than saprolite samples. C: Previously observed linear relationship between climate and chemical index of alteration (CIA) values of granitoid soil and estuarine sediment. All data are from humid and subhumid climates with varying mean temperatures, except Antarctica (ANT—Antarctica; CMR—Cameroon; GA—Georgia, USA; IRL—Ireland; MYS—Malaysia; PR—Puerto Rico; SWE—Sweden). D: CIA values from ancient and modern weathering profiles and fluvial sediment from tropical and subtropical climates. See the Data Repository (text footnote 1) for data references.

Chemical weathering indices. A: Rio Guayanés (RG, Puerto Rico) sediment is ...

Published: 12 July 2018
Figure 2. Chemical weathering indices. A: Rio Guayanés (RG, Puerto Rico) sediment is much less weathered than saprolite, comparable to values observed in rindlets within Luquillo Experimental Forest (LEF; Turner et al., 2003 ) when plotted on A-CN-K space ( Nesbitt and Young, 1984 ). B: RG
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Plot showing reaction fronts for three minerals, j, denoted as τj versus depth, as observed in regolith cores sampled from the Rio Blanco quartz diorite in the Luquillo Experimental Forest, Puerto Rico (after Buss et al. 2008). Oxidation of ferrous biotite occurs deepest in the profile (reaction front labeled as ferrous biotite), followed by plagioclase dissolution (reaction front not shown here for clarity), hornblende dissolution (reaction front labeled as hornblende), and ferric biotite conversion to kaolinite (labeled ferric biotite). The plagioclase τ-depth data is not shown here because it overlies the ferrous biotite data at the scale of this plot, although it is shifted slightly upward. The completely developed reaction fronts for plagioclase, hornblende and ferrous biotite all lie largely within the rindlet zone. The completely developed reaction front for ferric biotite lies largely in the saprolite. In contrast, quartz, not plotted here, is characterized as a partially developed reaction profile because quartz is observed to dissolve in the upper regolith but remains in the profile even to the land surface. This plot is a schematic version based on data from several cores taken from several locations as described previously (Murphy et al. 1998; White et al. 1998; Turner et al. 2003; Buss et al. 2008). As such, the actual depth values may vary for different cores. The ferric biotite may be a profile-controlling mineral in this system (see text).

Plot showing reaction fronts for three minerals, j , denoted as τ j ver...

Published: 01 January 2009
Figure 6. Plot showing reaction fronts for three minerals, j , denoted as τ j versus depth, as observed in regolith cores sampled from the Rio Blanco quartz diorite in the Luquillo Experimental Forest, Puerto Rico (after Buss et al. 2008 ). Oxidation of ferrous biotite occurs deepest
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Completely developed profiles for the three steady-state regolith case studies: A) τNa plotted versus depth for one core into the Rio Blanco quartz diorite, Luquillo Experimental Forest, Puerto Rico (Buss et al. 2008); B) Na (albite) concentration versus depth for Panola GA (White et al. 2001); C) Na (albite) concentration versus depth for Davis Run, VA (White et al. 2001). The reaction front thickness for Na decreases from Davis Run granite (~10 m) to Panola granite (~6 m) to Puerto Rico quartz diorite (~40 cm) as the ratio of transport to dissolution rate decreases. A first-order control on this ratio is the physical state of the weathering material: at Davis Run, weathering of Na-feldspar is occurring in saprolite where advective transport dominates, while Na release from Panola occurs within the reacting low-porosity bedrock where diffusion dominates. In Puerto Rico, fracturing due to spheroidal weathering has been observed to create onionskin-like rindlets around weathering bedrock, accelerating the transport of reactants into the weathering bedrock (Fletcher et al. 2006). Curve fits to the data are also shown for the sigmoidal (B, D, Eqn. 30) and exponential models (C, E, Eqn. 35). The loss of Na in the Rio Blanco quartz diorite occurs in the 30–40 cm thick rindlet zone that defines the reaction front for Na plagioclase at the bedrock-saprolite transition. In Panola, the bedrock-saprolite transition lies just deeper than 5 m. For Davis Run, the bedrock-saprolite transition is more than a meter wide and lies below 20 m.

Completely developed profiles for the three steady-state regolith case stud...

Published: 01 January 2009
Figure 11. Completely developed profiles for the three steady-state regolith case studies: A) τ Na plotted versus depth for one core into the Rio Blanco quartz diorite, Luquillo Experimental Forest, Puerto Rico ( Buss et al. 2008 ); B) Na (albite) concentration versus depth for Panola GA
Journal Article

Anomalously low chemical weathering in fluvial sediment of a tropical watershed (Puerto Rico)

Young Ji Joo, Megan E. Elwood Madden, Gerilyn S. Soreghan
Journal: Geology
Published: 12 July 2018
Geology (2018) 46 (8): 691–694.
DOI: https://doi.org/10.1130/G40315.1
... in rindlets from Luquillo Experimental Forest (LEF), northeast Puerto Rico (left panel). ...
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Journal Article

δ 30 Si systematics in a granitic saprolite, Puerto Rico

Karen Ziegler, Oliver A. Chadwick, Art F. White, Mark A. Brzezinski
Journal: Geology
Published: 01 October 2005
Geology (2005) 33 (10): 817–820.
DOI: https://doi.org/10.1130/G21707.1
... corresponding shift in bulk-solid δ 30 Si composition. References Brown , E.T. , Stallard , R.F. , Larsen , M.C. , Raisbeck , G.M. , and Yiou , F. , 1995 , Denundation rates determined from the accumulation of in situ produced 10 Be in the Luquillo Experimental Forest, Puerto...
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Journal Article

Use of a new 10 Be and 26 Al inventory method to date marine terraces, Santa Cruz, California, USA: Comment and Reply: COMMENT

E.T. Brown, D.L. Bourlès
Journal: Geology
Published: 01 December 2002
Geology (2002) 30 (12): 1147–1148.
DOI: https://doi.org/10.1130/0091-7613(2002)030<1147:UOANBA>2.0.CO;2
... . Brown , E.T. , Stallard , R.F. , Larsen , M.C. , Raisbeck , G.M. , and Yiou , F. , 1995 , Denudation rates determined from the accumulation of in situ-produced 10 Be in the Luquillo Experimental Forest, Puerto Rico : Earth and Planetary Science Letters , v. 129 p. 193 – 202...
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Journal Article

How accurate are rivers as gauges of chemical denudation of the Earth surface?

Julien Bouchez, Jérôme Gaillardet
Journal: Geology
Published: 01 February 2014
Geology (2014) 42 (2): 171–174.
DOI: https://doi.org/10.1130/G34934.1
... weathering of quartz diorite bedrock in the Rio Icacos basin, Luquillo Experimental Forest, Puerto Rico : Chemical Geology , v. 202 , p. 313 – 341 . West J.A. Galy A. Bickle M.J. , 2005 , Tectonic and climatic controls on silicate weathering : Earth and Planetary Science Letters , v...
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Journal Article

Effects of land-use change on channel morphology in northeastern Puerto Rico

Jeffrey J. Clark, Peter R. Wilcock
Journal: GSA Bulletin
Published: 01 December 2000
GSA Bulletin (2000) 112 (12): 1763–1777.
DOI: https://doi.org/10.1130/0016-7606(2000)112<1763:EOLUCO>2.0.CO;2
...Figure 1. Location map of northeastern Puerto Rico and the three rivers studied. These watersheds all drain the Luquillo Experimental Forest (LEF). Cross-valley core sections are denoted by tick marks and channel cross sections are denoted by filled circles. Note different scales used on the inset...
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Journal Article

Physical and Chemical Controls on the Critical Zone

Suzanne Prestrud Anderson, Friedhelm von Blanckenburg, Arthur F. White
Journal: Elements
Published: 01 October 2007
Elements (2007) 3 (5): 315–319.
DOI: https://doi.org/10.2113/gselements.3.5.315
... effects play out? Differing system behaviors are reported in the literature. In the warm, wet, steep terrain of Luquillo Experimental Forest, Puerto Rico, complete weathering of plagioclase occurs at the bedrock-saprolite interface, while more resistant minerals survive farther up into the CZ ( White...
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Journal Article

Anisovolumetric weathering in granitic saprolite controlled by climate and erosion rate

Clifford S. Riebe, Russell P. Callahan, Sarah B.-M. Granke, Bradley J. Carr, Jorden L. Hayes, Marlie S. Schell, Leonard S. Sklar
Journal: Geology
Published: 12 January 2021
Geology (2021) 49 (5): 551–555.
DOI: https://doi.org/10.1130/G48191.1
... rates determined from the accumulation of in situ–produced Be-10 in the Luquillo Experimental Forest, Puerto Rico : Earth and Planetary Science Letters , v. 129 , p. 193 – 202 , https://doi.org/10.1016/0012-821X(94)00249-X . Callahan , R.P. , , 2019 , Arrested development: Erosional...
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Journal Article

Strong tectonic and weak climatic control of long-term chemical weathering rates

Clifford S. Riebe, James W. Kirchner, Darryl E. Granger, Robert C. Finkel
Journal: Geology
Published: 01 June 2001
Geology (2001) 29 (6): 511–514.
DOI: https://doi.org/10.1130/0091-7613(2001)029<0511:STAWCC>2.0.CO;2
... Be in the Luquillo Experimental Forest, Puerto Rico : Earth and Planetary Science Letters , v. 129 p. 193 – 202 . Earle , C.J. , 1993 , Asynchronous droughts in California streamflow as reconstructed from tree rings : Quaternary Research , v. 39 p. 290 – 299 . Heimsath , A.M. , Dietrich...
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Journal Article

How Porosity Increases During Incipient Weathering of Crystalline Silicate Rocks

Alexis Navarre-Sitchler, Susan L. Brantley, Gernot Rother
Published: 01 January 2015
Reviews in Mineralogy and Geochemistry (2015) 80 (1): 331–354.
DOI: https://doi.org/10.2138/rmg.2015.80.10
... of shales these plots can be linear over ten orders of magnitude ( Jin et al. 2013 ). A study of samples of quartz diorite from the Luquillo Critical Zone Observatory in the Luquillo Experimental Forest provides the most detailed published information on porosity development during initial weathering...
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Increase of human over natural erosion rates in tropical highlands constrained by cosmogenic nuclides

Tilak Hewawasam, Friedhelm von Blanckenburg, Mirjam Schaller, Peter Kubik
Journal: Geology
Published: 01 July 2003
Geology (2003) 31 (7): 597–600.
DOI: https://doi.org/10.1130/0091-7613(2003)031<0597:IOHONE>2.0.CO;2
.... 170 p. 95 - 111 . Brown , E.T. , Stallard , R.F. , Larsen , M.C. , Raisbeck , G.M. , and Yiou , F. , 1995 , Denudation rates determined from the accumulation of in situ–produced 10 Be in the Luquillo Experimental Forest, Puerto Rico : Earth and Planetary Science Letters...
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Journal Article

East African weathering dynamics controlled by vegetation-climate feedbacks

Sarah J. Ivory, Michael M. McGlue, Geoffrey S. Ellis, Adam Boehlke, Anne-Marie Lézine, Annie Vincens, Andrew S. Cohen
Journal: Geology
Published: 26 July 2017
Geology (2017) 45 (9): 823–826.
DOI: https://doi.org/10.1130/G38938.1
... on weathering has been highlighted in experimental watershed studies ( Dunne, 1979 ; Drever, 1994 ; Berner and Cochran, 1998 ). For example, interactions between biotic and abiotic systems have been studied at the Luquillo Critical Zone Observatory (Puerto Rico) (e.g., White et al., 1998 ). However...
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Journal Article

Mountain erosion over 10 yr, 10 k.y., and 10 m.y. time scales

James W. Kirchner, Robert C. Finkel, Clifford S. Riebe, Darryl E. Granger, James L. Clayton, John G. King, Walter F. Megahan
Journal: Geology
Published: 01 July 2001
Geology (2001) 29 (7): 591–594.
DOI: https://doi.org/10.1130/0091-7613(2001)029<0591:MEOYKY>2.0.CO;2
... in the Luquillo Experimental Forest, Puerto Rico : Earth and Planetary Science Letters , v. 129 p. 193 – 202 . Brown , E.T. , Bourles , D.L. , Colin , F. , Raisbeck , G.M. , Yiou , F. , and Desgarceaux , S. , 1995b , Evidence for muon-induced production of 10Be in near- surface...
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Journal Article

Critical Zone Research and Observatories: Current Status and Future Perspectives

Li Guo, Henry Lin
Published: 01 September 2016
Vadose Zone Journal (2016) 15 (9): vzj2016.06.0050.
DOI: https://doi.org/10.2136/vzj2016.06.0050
... research topic in CZ science. For example, at the Luquillo CZO, Stone et al. (2015) found differences in the dominant bacterial community structure with depth for two contrasting parent materials and two forest types within the upper 1.4 m of soil profiles. That study indicated that in tropical forests...
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Journal Article

Restoring dense vegetation can slow mountain erosion to near natural benchmark levels

Veerle Vanacker, Friedhelm von Blanckenburg, Gerard Govers, Armando Molina, Jean Poesen, Jozef Deckers, Peter Kubik
Journal: Geology
Published: 01 April 2007
Geology (2007) 35 (4): 303–306.
DOI: https://doi.org/10.1130/G23109A.1
... , R.F. , Larsen , M.C. , Raisbeck , G.M. , and Yiou , F. , 1995 , Denudation rates determined from the accumulation of in situ-produced 10 Be in the Luquillo Experimental Forest, Puerto Rico : Earth and Planetary Science Letters , v. 129 pp. 193 - 202 doi: 10.1016/0012-821X(94...
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Journal Article

Approaches to Modeling Weathered Regolith

Susan L. Brantley, Art F. White
Published: 01 January 2009
Reviews in Mineralogy and Geochemistry (2009) 70 (1): 435–484.
DOI: https://doi.org/10.2138/rmg.2009.70.10
...Figure 6. Plot showing reaction fronts for three minerals, j , denoted as τ j versus depth, as observed in regolith cores sampled from the Rio Blanco quartz diorite in the Luquillo Experimental Forest, Puerto Rico (after Buss et al. 2008 ). Oxidation of ferrous biotite occurs deepest...
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