The
samples have been chosen to help us characterize the effect of varnish on the
spectra of underlying rock substrates.
Thus, we have primarily collected samples of varnished rocks from desert
pavements and other varnished rocks.
The spectra are directional hemispherical reflectance obtained with an unpurged Bruker Equinox55 FTIR spectrometer. Spectral resolution is 1 cm-1, although the sampling rate is considerably greater. The spectral range is from 7500cm-1 to 400cm-1 (~ 1.33 microns – 25 microns). We find the spectra are most useful from ~ 2 to 5 microns, and from ~ 7. 5 to 14 microns. Low instrument signal-to-noise and telluric band obscure the spectra in the following regions:
<1.8 microns (low SNR)
~ 2.7 to 3 microns (water)
~ 4.25 microns (CO2)
~ 5 to 7. 5 microns (water)
> 18 microns.
A diffuse gold standard is used to obtained background measurements for each rock. Often 2 to 3 spectra are obtained from a single rock. Each spectrum is an average of 69 spectra (1 min of instrument operation). Thus a new background is generally obtained ~ every 5 minutes.
Data
Format
The data is two column ascii, comma separated, with no header. [Wavelength, reflectance] in ascending wavelength.
Nomenclature
Currently, the naming corresponds to the location. For instance, under the Mecca Hills directory, a spectrum named: ‘D1S1R10 c.DPT’ corresponds the ‘cut’ face on ‘rock10’ that was collected on ‘Day 1’ from ‘Site 1’. Spectra of varnished rocks end with ‘…..dv.DPT’ (for the ‘dark varnish’ on top of the rock, and end with ‘….. ov.DPT’ for the ‘orange varnish’ on the underside of the rocks. Information on the lithology of the rock substrate is not yet available.
Locations:
Mecca Hills: rocks and some soils have been obtained from desert pavements at Mecca Hills, Ca. Only the rocks are listed. Samples were collected in February, 2004 (sites 1 – 3) and in July, 2004 (Stop 2). Spectra were obtained during the summer, 2004. The spectra are of varnished topside (sometimes very light or negligible varnish), a freshly broken face or cut, and of the orange varnish on the underside of rock.
Site 1. 33o43.395N, 116o07.312W. from desert pavement on a fan ~ 60Ka.
Site 2: 33o44.395N, 116o06.839W.
Site 3: 33o39.475N, 115o58.831W
Stop 2: 33o40.128N, 115o58.224W
Miscellaneous: Rocks 61 –63 are igneous, silica rich, varnished but of unknown origin (not Mecca Hills. Provided originally by Dr. Randy Perry). 52 and 54 are basaltic substrate? with a nonvarnish orange stain.
Pahoehoe: Hawaii pahoehoe, ranging from pristine blue pahoehoe with submicron hematite sheen to older weathered vesiculated rocks. Obviously none are varnished. #64 is weathered vesicular, #98,99 are blue, glassy.
Miscellaneous Varnished: #105- varnished quartzite, #106 – varnished vesicular basalt, # 107 – varnished tuff? Andesite? Basalt?
River Rocks: these were collected at a wash outside of the East Gate of the Jet Propulsion Laboratory. Unvarnished but dusty (#103 and #104 are very dusty) quartz(#102), granite (#103) and schist?(#104).
Road Cut: these are basalts, unvarnished, but somewhat weathered, collected along a road cut in the highway 82 that passes through the flood basalt covering the Yakima, Wa. region. No varnish.
MFR. These are spectra of powered samples of pahoehoe and dolomite, some of which have been exposed to sulfuric acid vapor while in a vial purged with nitrogen. No apparent spectral affect. Not in support of the terrain work, no varnish.
Organics: various organic materials including green vegetation, human arm (still attached to living body), motor oil, etc.
Sands: wet qtz. beach sands from San Onofre, Ca. beach.
Other: a grab bag of spectra
Varnished Sandstone: provided by Dr. Randy Perry from an unknown location near Death Valley, Ca.