Memory arrays and methods used in forming a memory array comprising strings of memory cells

A method used in forming a memory array comprising strings of memory cells, comprising:

• forming a stack comprising vertically-alternating first tiers and second tiers, the first tiers comprising first sacrificial material;
• forming horizontally-elongated trenches into the stack to form laterally-spaced memory-block regions;
• forming second sacrificial material in the trenches;
• forming bridges above the stack and the second sacrificial material, the bridges extending across the trenches laterally-between and longitudinally-spaced-along immediately-laterally-adjacent of the memory-block regions;
• isotropically etching away the second sacrificial material selectively relative to the bridges and the second tiers;
• isotropically etching away and replacing the first sacrificial material that is in the first tiers with conducting material of individual conductive lines;
• and
• forming intervening material in the trenches directly under and longitudinally-between the bridges between the immediately-laterally-adjacent memory-block regions.