Lake Ohrid (Macedonia / Albania) is probably the oldest lake in Europe (2-5 Ma), and is considered an important sedimentary archive to study the evolution of a graben system over several million years. Multichannel seismic profiles were acquired in 2007 and 2008 showing that the lake can be divided into two main parts, the slope areas and a large, deep central basin.
The basin is bordered by the major eastern and western graben fault, additional faults were identifi ed in the northern part of the lake. These faults are active, as we can trace them from the basement up to the lake floor. Clinoforms mainly found in the southern part of the lake indicate that the Lake has undergone major lake level fluctuations. The central basin shows widespread areas with thick, undisturbed sedimentary successions. No indications for a dry lake are found in this part of the lake, hence, offering the possibility to recover long, continuous archives
for the entire lifetime of Lake Ohrid in the frame of the proposed SCOPSCO(Scientific Collaboration On Past Speciation Conditions in Lake Ohrid)-ICDP(International Continental Drilling Program) campaign. Five primary drilling locations have been chosen as ICDP sites.
One 680 m long record in the central part will
provide substantial information on age and origin of the lake, as well as a complete record of environmental history (incl. e.g. tephra deposition, evolutionary changes and their relation to geological events). Furthermore, four additional drill sites closer to the shore of the lake will provide information on major changes of the hydrological
regime, the age of ancient foresets, lake level changes, the tectonic activity, and mass movements. The drilling proposal is approved by ICDP and will be realized in summer 2011 or 2012.
Abstract. Ancient Lake Ohrid is a steep sided, oligotrophic, karst lake of likely Pliocene age and often referred to as a hotspot of endemic biodiversity. This study aims on tracing significant lake level fluctuations at Lake Ohrid using high-resolution acoustic data in combination with lithological, geochemical, and chronological information from two sediment cores recovered from sub-aquatic terrace levels at ca. 32 and 55 m. According to our data, significant lake level fluctuations with prominent lowstands of ca. 60 and 35 m below the present water level occurred during MIS 6 and MIS 5, respectively. The effect of these lowstands on biodiversity in most coastal parts of the lake is negligible, due to only small changes in lake surface area, coastline, and habitat. In contrast, biodiversity in shallower areas was more severely affected due to disconnection of today sub-lacustrine springs from the main water body. Multichannel seismic data from deeper parts of the lake clearly imaged several clinoform structures stacked on top of each other. These stacked clinoforms indicate significantly lower lake levels prior to MIS 6 and a stepwise rise of water level with intermittent stillstands since its existence as water filled body, which might have caused enhanced expansion of endemic species within Lake Ohrid.
Abstract. Ancient Lake Ohrid is a steep-sided, oligotrophic, karst lake that was tectonically formed most likely within the Pliocene and often referred to as a hotspot of endemic biodiversity. This study aims on tracing significant lake level fluctuations at Lake Ohrid using high-resolution acoustic data in combination with lithological, geochemical, and chronological information from two sediment cores recovered from sub-aquatic terrace levels at ca. 32 and 60 m water depth. According to our data, significant lake level fluctuations with prominent lowstands of ca. 60 and 35 m below the present water level occurred during Marine Isotope Stage (MIS) 6 and MIS 5, respectively. The effect of these lowstands on biodiversity in most coastal parts of the lake is negligible, due to only small changes in lake surface area, coastline, and habitat. In contrast, biodiversity in shallower areas was more severely affected due to disconnection of today sub-lacustrine springs from the main water body. Multichannel seismic data from deeper parts of the lake clearly image several clinoform structures stacked on top of each other. These stacked clinoforms indicate significantly lower lake levels prior to MIS 6 and a stepwise rise of water level with intermittent stillstands since its existence as water-filled body, which might have caused enhanced expansion of endemic species within Lake Ohrid.
