ESTABLISHMENT OF A HIGH-RESOLUTION STRATIGRAPHY WITH THE HELP OF DENDROCHRONOLOGY-AN EXAMPLE FROM THE MARINE HOLOCENE SEQUENCE IN THE ANCIENT THEODOSIAN HARBOR (ISTANBUL, TURKEY)

Salvage excavations in the Theodosian harbor (Yenikapi-Istanbul) have uncovered various Byzantine period docks constructed from wooden posts. The sequence of these docks in different construction phases at Yenikapi provided a unique opportunity to combine dendrochronological and geological methodologies to obtain a precisely dated high-resolution stratigraphy. The basic idea of this new approach is based on the analysis of the deformation patterns created when the posts were rammed into the soft sediments. Dendrochronology offers the potential to date the posts which made the deformations to within one calendar year of felling, though dating precision and accuracy depends on the condition of the wood sample. Using the dataset of the Aegean Dendrochronology Project (ADP), posts rammed in at different intervals of the sedimentary sequence were assigned dates.

In the area of the Theodosian harbor, the top of the stratigraphic sequence consists of soil and artificial fill, and then progresses down through a series of fluvial deposits and marine sediments to a dark gray to black clay of Holocene age underlain by Late Miocene deposits. The wooden posts penetrate seven distinguishable subunits of the marine Holocene sediments. Within these, groups of posts rammed in during different periods could be differentiated.

Studies conducted at three different docks resulted in groups of posts in five periods. The first period at the upper part of Unit 4 of the marine sequence is associated with posts cut in 528 AD. The second period, with typical deformation patterns also at upper parts of Unit 4 is dated by posts cut in 583 and 594 AD. The third period, which was just after the deposition of Unit 5, dates within 8-10 years of 639 AD. The fourth period could be dated only roughly to between 690 and 770 AD. The last period produced a possible dendrochronological placement of after 778 AD, most likely connected with Unit 7.

This new approach can provide high-resolution information about the sedimentation history in coastal terrains. Furthermore, specific anthropogenic events can be dated more precisely.