could the ice age have been caused by salt in the sediments?

Answer 1

No. It can be assumed that salt in sediments is constant (or nearly so), whereas glaciation is a rare event in the Earth's history. If salt caused global cooling then it should be a common event. Also, salt raises the melting point of ice, making it harder to have glaciation. This is why municipalities put salt on iced-over roadways; to melt the ice. Those are two good reasons why your premise is wrong.

Answer 2

Well, I am trying to think how and not coming up with any good mechanisms. It would be helpful if you had given us the way it is supposed to have done this.

I can imagine ways that salt variations in sediments could indicate (be an indirect or direct result of) ice age conditions but I can't remember reading anything along those lines as being indicated from studies. Your question is also a little unclear because most people think of table salt NaCl when talking about salt but when geologists talk about salts and salinity we typically mean dissolved solids and precipitates from solution, which can include a lot of different minerals.

Anyway, I suppose it is possible (I've been convinced of seemingly stranger things) but really, I doubt it.

Answer 3

No. Water has a finite capacity for dissolving salt. As a result, any excess salt in the water won't melt ice, it will just leave the water in some way, usually by precipitating as an evaporite. Since the concentration of salt in the ocean is relatively constant through the years, it has no effect (gain or loss) on the amount of sea ice at the poles.