A pelagic or hemipelagic sediment (an arl), typically found interbedded with purer oozes in beds up to 1.5 m thick, with a composition intermediate between a non-biogenic sediment and a calcareous or siliceous ooze. It is 30% clay and 70% microfossils, at least 15% of its volume being calcareous microfossils. Compare marl; smarl.