On the nature of border and map sheet faults (and their close relative, the grid line fault)
Authors: Que Aye, Que See
Address: Right Planet, Wrong Projection
Border and map sheet faults can be defined as really, really old structures. Border faults are known to occur along national, state and provincial boundaries, whereas map sheet faults are known to occur where one or more map sheets juxtapose each other. Both of these newly defined structural discontinuities are commonly found in regions where more than one geological map exists.
However, recent studies have revealed what is possibly a close relation to the border and map sheet fault – the grid line fault. This relative is known to occur within individual map sheets, with termination of structures and major discontinuities being prevalent along the grid lines.
Border and map sheet faults are unique in that they result in stratigraphic offsets so huge that some geological units disappear off of the face of the planet. It had frustrated the authors for years to find inconsistent rock types occurring along political borders and map sheet boundaries which had been dated eons apart even when all the mapping and geochronology had been done by the same geological survey. As any freshman undergraduate earth science student can clearly tell the difference between a granite and an ultramafic rock, the authors ruled out the possibility of human error and chose to seek alternative explanations for the phenomenon.
Explanations investigated included:
- Geological survey maps being inaccurate – this was ruled out because everyone knows that adjacent map sheets produced by the same survey are checked for consistency before being publicly published!
- Political problems – excluded because we all live in a happy land of cooperation and data sharing!
- Digitizing issues – obviously not the cause, because everyone verifies the digital maps against the original hard copies to make sure there are no typos in the database!
- Geological surveys not using remote sensing or geophysical data for validation – of course they have! Because they said so! What? You can’t get the geophysical data to check for yourself because it’s classified under national security? What happened to that happy land of data sharing? HAPPY LAND!
As all of the explanations investigated were ruled out as the cause, we can only postulate that border and map sheet faults are the result of some as yet undetermined global geological event.
Grid line faults present more of a problem though, as they’re all on the same map sheet. Could these structures have had some uncanny ability to predict what projection the printed maps would be generated in? Spooky. Investigations into how these structures knew to generate discontinuities based on the parameters of the Lat/Long WGS84 standard back in the Precambrian are ongoing. Fossilized remains of a TARDIS are not unanticipated.