+------------------------------+---------------------------+-------+ | WESTERN AND MIDDLE | | DATE | | EUROPE | NORTHERN EUROPE | B. C. | +------------------------------+---------------------------+-------+ | 4. Typical Neolithic. | Typical Neolithic. | 6000- | | | Beech and fir forests. | 2500 | | 3. Daun Stage. | Litorina Epoch. | | | | Oak forests. | | | | Northern climatic | | | | optimum. | 8000 | | Campignian | Shell-heaps. | | | 2. Gschnitz Stage. | Ancylus Epoch. Birch and | | | | pine forests. | 10,000| | Azilian-Tardenoisian. | Magelmose. | | | 1. Bühl Stage. | Yoldia Epoch. | | | | Swedish-Finnish Moraines | 16,000| | Magdalenian (later) | Tundra. Dryas Flora. | | +------------------------------+---------------------------+-------+ The growth and succession of the forests of Denmark, accompanying changes in conditions of soil and climate, have been clearly traced by Steenstrup.[29] The scene of his investigations was a moraine country broken by low ranges of hills in the island of Zealand, north of Copenhagen. The hills are often strewn with erratic blocks of rock brought by glaciers, with here and there small lakes, ponds, or peat-bogs often giving place to meadow or forest. Some of these depressions are filled with a poor variety of peat, dug for fuel, and the sides are often abrupt, steep, and deep. These sides furnish a calendar by showing the different layers which have been formed by successive generations of tree-growth falling into the bog. Thus, in the upper layers we find remains of trees which still flourish in Denmark, while the deepest strata contain the remains of reindeer. The thickness of these layers is between five and seven metres. Their formation, according to Steenstrup, occupied 10,000 to 12,000 years.(1) The following layers are found in these "calendars," beginning at the surface: 1. Surface layer. Remains of the beech, which furnishes the chief beauty of the forests of Denmark to-day. 2. Oak. The beginning of this layer was contemporary with the Litorina depression.