data_Fragments {ggtern}

Grantham and Valbel Rock Fragment Data

Description

ABSTRACT: Chemical weathering influences the detrital composition of sand-size sediment derived from source areas subject to different amounts of precipitation in the Coweeta Basin, North Carolina. Of the grain types studied, rock fragments are most sensitive to chemical degradation; therefore, their abundance is the best indicator of cumulative weathering effects. Destruction of sand-size rock fragments by chemical weathering is a function of both the intensity and duration of chemical weathering experienced by grains in regoliths of the source area. In the Coweeta Basin, the intensity of chemical weathering is directly related to the climate via effective precipitation in individual subbasins, whereas the duration of chemical weathering is inversely related to the relief ratio of the watershe . Therefore, soils in watersheds with low-relief ratios and high discharge per unit area experience the most extensive chemical weathering, and sediments derived from these watersheds contain the lowest percentage of rock fragments. The effects of climate alone cannot explain the systematic variation of rock fragment abundance in sediments from the Coweeta Basin. The compositional imprint left on these sediments by chemical weathering is a function of both climate and topographic slope in the sediment source area.

Usage

data(Fragments)

Format

1row per point, Each point contains data on the following:

1. Watershed: By id: 2, 10, 34, 41, 13, 27, 32 or 37,

2. Position: By name: Tallulah or Coweeta,

3. CCWI: The Cumulative Chemical Weathering Index: numeric

4. Precipitation: Average Annual Precipitation, numeric

5. Discharge: Annual Average Discharge, numeric

6. Relief: Relief Ratio, numeric

7. GrainSize: Coarse Medium or Fine,

8. Sample: Field Sampling, A, B or C

9. Points: The number of points measured for each sample

10. Qm: Multicrystalline Quarts Amount, percentage

11. Qp: Polycrystalline Quarts Amount, percentage

12. Rf: Rock Fragments Amount, percentage

13. M: Mica Amount, percentage

Author(s)

Jeremy Hummon Grantham and Michael Anthony Velbel

References

Grantham, Jeremy Hummon, and Michael Anthony Velbel. "The influence of climate and topography on rock-fragment abundance in modern fluvial sands of the southern Blue Ridge Mountains, North Carolina." Journal of Sedimentary Research 58.2 (1988).

Examples

data(Fragments)
ggtern(Fragments,aes(Qm+Qp,Rf,M,colour=Sample)) +
  geom_density_tern(h=2,aes(fill=..level..),
  expand=0.75,alpha=0.5,bins=5) + 
  geom_point(aes(shape=Position,size=Relief)) + 
  theme_bw(base_size=8) + 
  theme_showarrows() + 
  custom_percent('%') + 
  labs(title = "Grantham and Valbel Rock Fragment Data",
       x = "Q_{m+p}", xarrow = "Quartz (Multi + Poly)",
       y = "R_f",     yarrow = "Rock Fragments",
       z = "M",       zarrow = "Mica") + 
  theme_latex() + 
  facet_wrap(~Sample,nrow=2)