From 2.1 patch notes:
Timeworn Leather Map: Level 40 mature trees, lush vegetation patches, mineral deposits, rocky outcrops, and fishing holes.
Timeworn Goatskin Map: Level 45 mature trees, lush vegetation patches, mineral deposits, rocky outcrops, and fishing holes.
Timeworn Toadskin Map: Level 50 mature trees, lush vegetation patches, mineral deposits, rocky outcrops, and fishing holes (South Umbral Isles and Rathefrost only)
Timeworn Boarskin Map: Level 50 mature trees, lush vegetation patches, mineral deposits, rocky outcrops, and fishing holes (Reaver Hide and the Tangle only)
Timeworn Peisteskin Map: Level 50 mature trees, lush vegetation patches, mineral deposits, rocky outcrops, and fishing holes (Lake Tahtotl, Parata's Peace, and the North Shards only).

Peisteskin maps are "recommended" to have a full party, but can be done with as little as 2-3 people safely.

Notable items from each tier:
Leather: Ahriman Tears, Lotus Leaf
Goatskin: Blue Fox Hide, Exquisite Buttons
Toadskin: Cutting Oil, Morbol Saliva, Tiny Bulb (minion)
Boarskin: Mariner Cotton Cloth, Wind-up Tonberry (minion)
Peisteskin: Chinchilla Hide, Frosted Glass Lens, Dress Material, Bluebird (minion)