View menu

Geographic (command G):
Makes all relevant windows (all graphics windows except J/J0 plot) plot data using geographic (in situ) coordinates.

Stratigraphic (command T):
Makes all relevant windows (all graphics windows except J/J0 plot) plot data using stratigraphic (tilt-corrected) coordinates.
Make all relevant windows (all graphics windows except J/J0 plot, Least Squares Equal Area, and Least Squares Strat Plot) plot data using sample core coordinates (disabled if not available). The coordinates used for the two Least Squares plots becomes italicized in the menu.
N-S Orthographic:
Makes a "Zijderveld" plot using an orthographic or "true Zijderfeld" projection. In this projection the horizontal axis is East for both inclination and declination data. This is the most common orthographic vector plot in use.

E-W Orthographic:
Makes a "Zijderveld" plot using an orthographic or "true Zijderfeld" projection. In this projection the horizontal axis is North for both inclination and declination data, which produces an unorthodox view that takes some mental adjustment. Useful when vectors lie in a steep, N-S plane.
Makes Zijderveld plot use a so-called hyperbolic projection. The inclination data is plotted with the total horizontal intensity as the horizontal axis; so called because a line passing near (but not through) the origin will resemble a hyperbola in this projection. Very useful when the declinations tend to be near due north or south.
Total J:
This is the initial type of J/J0 plot as described under J/J0 plot, above. This is also the standard type of J/J0 plot in use.
Component J...:
An unorthodox method of viewing the change in intensity of components of megnetization over a range of demagnetization steps. This brings up a dialog box where the desired component(s) can be designated:

For instance, here we have designated a geographic direction that might be the modern dipole field at our locality as direction one, a second direction in tilt-corrected coordinates as direction 2, and we have not designated a direction 3. This will produce three panes in the J/J0 window: one for each of the two designated directions and a third called "Perp." which is the unit cross product of the two designated directions. Identifications of the directions is in the upper right part of the window. Because these are all vectors, both the J/J0 and derivative plots can be positive or negative. The base of the derivative rectangles indicates the zero in each pane. If only one direction is chosen, then the "Perp." direction is actually a scalar quantity representing the intensity in the plane perpendicular to the chosen direction.

What happens here is that we can represent any magnetization vector v as a sum of three independent vectors: v=a1*e1+a2*e2+a3*e3. Note that the three vectors need only be independent (they must span 3-space) and do not have to be orthogonal. Thus this technique will correctly separate an overprint from a characteristic direction even if the two are much less than 90°ree; apart.

For example, the following sample's Zijderveld plot looks like:

and produces a normal J/J0 plot looking like:

which reveals two components, here rather cleanly separated. If we estimate the two directions, say by doing least-squares fits (and possibly coming up with mean directions for the locality), we can make a component J/J0 plot that will look like this:

(the bottom ticks are at 100°ree; increments). This plot seems to substantiate the identification of the two components, but note the blip of the first component in the 400-425°ree; range; also note the erratic behavior of the orthogonal component, indicating an absence of a consistent magnetization along this axis.

Variable Scales:
As illustrated above, the vertical scales on each panel are scaled separately. Only can be chosen if the "Component J/J0..." option was chosen.
Constant Scales:
All panes in the Component J/J0.. plot have the same scale. For example, the example above then looks like:

This tends to downplay spurious magnetizations, though weak characteristic directions might also become invisible.

View by sample:
When checked, all group plots will display each sample as an individual point. See the Samples, Sites, and Localities section below for more detail.

View by site:
When checked, all group plots will display each site as an individual point. Directions displayed are Fisher means from samples within a site. Identifying points will produce the id of the first sample in the site, the number of measurements actually used, and the alpha-95 of the mean (note that N is usually so low for these sites that the alpha-95 rarely has great significance beyond a guide to the scatter of the points). See the Samples, Sites, and Localities section below for more detail. Grayed out if sites have not been defined for this locality (see "Define Sites..." in the File menu).

Include Sites...:
Brings up a dialog for specifying the maximum alpha-95 a site can have and be displayed and a checkbox to permit the rejection of single sample sites (which cannot have an estimated alpha-95). See the Samples, Sites, and Localities section below.

Active only when Site or Least Squares Equal Area window frontmost:

Locality Means...:
Active only if there is an open Means file. Brings up a dialog box similar to that for choosing Least Squares Fits for the site and least- squares equal area plots; this dialog lets you choose means from the Means file for plotting in the locality or least-squares equal area window. Control over the color and shape of each mean on the plot is controlled from the "Means Colors..." dialog in the Edit menu. This dialog also lets you change the means selected.
Plot poles to planes:
When checked, plane and circle fits will be plotted as points at the pole to the plane.
Plot planes as planes:
When checked, plane and circle fits are drawn on the equal area plot as great circles over both upper and lower hemisphere.
Plot planes as arcs:
When checked, only the part of the plane or circle fit between the most distant point from the first measurement used in the fit and the antipode from the first point are shown. This helps to illustrate the results from the "Use Arc Constraints" option for the Fisher mean when combining line and plane data as the arcs shown are the same as those used in the McFadden and McElhinny (1988) formulation (see the discussion in the Statistics section).
Active only when Least Squares Strat Plot window frontmost:

Plot poles to planes:
When checked, plane and circle fits are plotted at the position of the pole to the plane and are marked with a box (instead of the circle used for line fits).
Plot planes at endpoints:
When checked, plane and circle fits are plotted at the most extreme point along the portion of the great circle fit (s; see the discussion in the .LSQ file format section). An arrow in the declination and inclination/paleolatitude panes indicates the direction demagnetization is proceeding; this arrow is absent when viewing by site or in the VGP latitude pane. When viewing by site, the site mean of the extreme points is plotted, but arrows are not and squares are used to denote the use of circle/plane fits. CAUTION: Note that the circle plotted is NOT at the position of the last point used in the original fit, but at the projection onto the great circle of the point used that is farthest from the starting end. In some circumstances (especially a plane fit not tied to the origin) this can produce a misleading indication of the possible polarity of the sample.
Plot planes as arcs:
Very similar to plotting planes at endpoints except that the arrow is replaced by a horizontal line extending over the possible values of declination and inclination or paleolatitude between phis and phie (see .LSQ file format section). This corresponds to converting the arcs from a least-squares equal area plot of plane and circle fits (when viewed as arcs) into declination and inclination variations. Note caution above applies to this plot. Arcs are not plotted when viewing by site (though points are means of phis) or in VGP latitude pane.

Next section

Table of Contents

Last section

Please send mail if you encounter any problems or have suggestions.

C. H. Jones | CIRES | Dept. of Geological Sciences | Univ. of Colorado at Boulder

Last modified at

1642 visits from Tue, Apr 21 1998 17:07 to Apr/ 6/02 23:12