Department of Physical Geography and Quaternary Geology Paleoenvironment and shore displacement since 3200 BC in the central part of the Långhundraleden Trail, SE Uppland Christos Katrantsiotis Master’s thesis NKA 70 Physical Geography and Quaternary Geology, 45 2013 Credits Preface This Master’s thesis is Christos Katrantsiotis degree project in Physical Geography and Quaternary Geology at the Department of Physical Geography and Quaternary Geology, Stockholm University. The Master’s thesis comprises 45 credits (one and a half term of full- time studies). Supervisor has been Jan Risberg at the Department of Physical Geography and Quaternary Geology, Stockholm University. Examiner has been Stefan Wastegård at the Department of Physical Geography and Quaternary Geology, Stockholm University. The author is responsible for the contents of this thesis. Stockholm, 4 March 2013 Lars-Ove Westerberg Director of studies Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail Abstract In this study, litho-, bio- and chronostratigraphic investigations combined with RTK GPS leveling have been carried out to reconstruct the paleoenvironment in the central part of the Långhundraleden Trail. The area displays four shallow lake basins of varying morphologies. The basins are now covered with peat as a result of infilling and overgrowth. The emergence of the saddle-point, i.e. the highest point of the underlying minerogenic surface, was estimated to have occurred c. BC/AD. The isolation events of two basins, at c.12.4 and c.12.3 m a.s.l. west and east of the saddle-point, were dated to c.AD 20 and c.AD 30, respectively. By combining these isolation data with six previously investigated basins a shore displacement curve for the central part of the Långhundraleden Trail and the surrounding area, i.e. east of the Ekoln basin was constructed. The curve indicates an average regressive shore displacement rate of c.6.2 mm/yr since c. 3200 BC. Around 1500 BC, this trend was interrupted by a short period of retarded regression, correlated with the L4 event. The isolation ages of the basins in the Långhundraleden Trail appears relatively young when compared to an average shore displacement rate of 5.6 mm/year in the northern part of L. Mälaren, west of the Ekoln basin. As the area is dominated by a fissure- valley landscape, this discrepancy could be attributed to small-scale irregular tectonic movements, which caused faster uplift rate, i.e. 6.2 mm/year, east of the Ekoln basin. 1 Christos Katrantsiotis 2 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail Table of Contents 1) Introduction ................................................................................................................................................... 5 2) Background .................................................................................................................................................... 7 2.1) Uppland county ..................................................................................................................................... 7 2.1.1) Geological settings ...................................................................................................................... 7 2.1.2) The Weichselian glaciation, deglaciation and sediment regimes ............................................... 8 2.1.3) Shore displacement ................................................................................................................... 10 2.1.4) Isostatic variability .................................................................................................................... 12 3) The Långhundraleden Trail ........................................................................................................................... 14 3.1) Location and general description .......................................................................................................... 14 3.2) Geological description ........................................................................................................................... 15 3.3) Landscape development ....................................................................................................................... 15 4) Description of the study site ......................................................................................................................... 18 5) Methods........................................................................................................................................................ 20 5.1) Field work .............................................................................................................................................. 20 5.1.1) Stratigraphical coring and sampling ............................................................................................ 20 5.1.2) Leveling ....................................................................................................................................... 20 5.2) Laboratory method ............................................................................................................................... 21 5.2.1) Loss on ignition ........................................................................................................................... 21 5.2.2) Diatom analysis ........................................................................................................................... 21 5.2.3) Radiocarbon dating ..................................................................................................................... 22 6) Results and interpretation ............................................................................................................................ 23 6.1) Lithostratigraphy ................................................................................................................................... 23 6.2) Leveling and morphology ...................................................................................................................... 32 6.3) Description of sampling sites for laboratory analyses ......................................................................... 34 6.3.1) Basin A......................................................................................................................................... 35 6.3.1.1) Age-depth model ........................................................................................................... 36 6.3.1.2) Loss on ignition .............................................................................................................. 38 6.3.1.3) Diatom analysis .............................................................................................................. 38 6.3.2) Basin B ......................................................................................................................................... 44 6.3.2.1) Age-depth model ........................................................................................................... 46 6.3.2.2) Loss on ignition .............................................................................................................. 49 6.3.2.3) Diatom analysis .............................................................................................................. 49 6.4) Evolution of the area .............................................................................................................................. 55 7) Discussion ..................................................................................................................................................... 58 7.1) Location of sampling sites ..................................................................................................................... 58 7.2) Determining isolation threshold elevation ........................................................................................... 59 7.3) Geographical settings ............................................................................................................................ 59 7.4) Defining the isolation event .................................................................................................................. 59 7.5) Diatom species distribution .................................................................................................................. 61 7.6) Diatom dissolution and preservation .................................................................................................... 64 7.7) Radiocarbon ages .................................................................................................................................. 65 7.8) Age difference between chironomids and plant macrofossils .............................................................. 65 7.9) Shore displacement ............................................................................................................................... 66 7.9.1) Description of sites ..................................................................................................................... 66 7.9.2) Description of the shore displacement curve ............................................................................. 70 7.10) Isostatic variability ............................................................................................................................... 75 8) Conclusions ..................................................................................................................................................