[BR-Crater] Auld Lang Syne group

[Scot Wilcoxon]

I'm curious about the Late Triassic/Jurassic Auld Lang Syne (ALS) group 
because in the Black Rock area it seems to be the most recent layer 
before the Cretaceous, and many layers above it are missing.

One report believes this may be due to erosion; if an impact took place 
obviously the layer was not exposed at the time of impact, or the 
exposed area was removed, or the exposed area is no longer recognizable 
as ALS.  The simplest explanation is that the ALS was not exposed to 
impact, so impact disturbances should be in layers above the ALS.

ALS has been found NE and E of Black Rock desert.

There is a 14-page USGS document describing ALS whose no-plugin version 
is presently broken.  I sent a message to the webmaster.

I've seen mention of Auld Lang Syne as being sedimentary in origin with 
no mention of melting (such as due to impact).  The Osobb Formation has 
been mentioned as being part of the ALS, and that is called equivalent 
to the Grass Valley Formation.  Dickins' book says that Silberling and 
Wallace (1969) interpret it as a deltaic system.  "a voluminous influx 
of siliclastic sediment",.. "Palaeocurrent indicators and a westward 
increas in mud-to-sand ratio indicate that distributaries transported 
sand from delta plains in the east to delta fronts and prodeltas in the 
west."

I've also seen it described as being thin (2 km) and very thick (25,000 
feet/7.6 km).