Much of the pay gap is explained by motherhood, in that working mothers earn much less on average than working fathers, and the average gap is less between childless working men and women. Because people are more likely to be parents as they get older, this has an effect on the relationship between pay, gender and age. You can see some UK numbers on page 8 here: women's median pay is 95% of men's for 22-29 year olds but 76% for 50-59 year olds. A harder question is how much of this involves a choice (with many mothers often choosing more flexible work which happens to be lower paid).
In the UK, women are less likely to work than men at each age group, but unemployment rates (i.e. those looking for work who cannot find it) are similar at each age group up to about 50. After 50, women are dramatically less likely to be looking for work than men of the same age. Part of this may be due to lower formal retirement ages, though there may also be women who want to stop work at the same time as their (on average) older husbands. Some UK numbers can be found on tab 2(2) here showing unemployment rates of 8.2% for men and 7.3% for 25-34 year olds, compared with 5.8% for men and 3.4% for women for 50-65 year olds. Not working looks likely to be voluntary for many older women.