What process can account for a normal xy male producing a sperm carrying two y chromosomes?

The answer is aneuploidy. This is the result of a malfunction in the process of meiosis that produces gametes, in the male.  The is caused by a failure in non-disjunction hence an extra Y chromosome occurs in one of the formed gamete cells during anaphase II.

i think the miocene epoch spans the time from 23 million to 12 million years ago.

1. loamy sand is about 80% sand with 10% clay and defined mostly by sand particles with some clay to provide structure and fertility. the sand particles are easily visible and the soil holds structure but breaks apart easily.

2. scott sand can improve his soil quality by incorporating more silt and organic matter into the soil. peat moss and organic matter can also be incorporated.