Croatia 2023

 The drowned landscapes off Croatia

I visited Croatia a number of years ago after diving on some of the submerged Roman sites in Greece and seeing the Temple of Serapis in Naples (https://upload.wikimedia.org/wikipedia/commons/9/9e/Charles_Lyell_-_Pillars_of_Pozzuoli.jpg) . The temple is geologically infamous as the front piece to Charles Lyell’s seminal work The Principals of Geology where he notes the mark of marine boring organisms at some height up the columns thus indicating that they were once submerged.  He correctly interprets this as representing tectonic movements that have caused both a submergence and subsequent re-emergence of the temple since its construction in the late first to early second century AD. Contemplating the potential for drowned landscape reconstructions around the Mediterranean and Adriatic seas I briefly looked for papers describing sea level changes.  These were almost entirely absent from the academic literature.  Fast-forward to 2023 and I am here on the invite of Dr Simon Fitch (Bradford University) as part of his Future Leaders project. The idea is to map paleo-landscape surfaces in the many rias (drowned river valleys) along the Adriatic eastern shore. 

Split, Croatia

The project in Croatia is partnered with Dr Vedran Barbarić at the Faculty of Humanities and Social Sciences, University of Split and the first trial survey was undertaken on board the Pram, expertly skippered by the enthusiastic and knowledgeable captain Jerko Macura . For the acquisition we had chosen to use an Innomar Quattro parametric sonar (https://www.innomar.com/products/multi-transducer/quattro-sbp).  This hull-mounted sonar is configurable as either a line of four transducers emitting separate signals for high-resolution 3D type survey or as a block of four transducers working together for greater power and thus sea floor penetration.  The unit was side-mounted together with a Novatel IMU GNSS unit to provide heave corrections.  

Innomar Quatro with Novatel dual antenna motion reference unit

Over the course of 5 days we surveyed a number of small bays, outlets to the main large bays, channel crossings and both large and small deltas.

The weather cooperated for the most part until the Bora winds (a sever katabatic northerly wind from the shore) stopped play on our last day. The survey exceeded our expectations with penetration to greater than 15m sub-bottom in water depths up to 70m deep.  The seismic reflectors and character demonstrated sequences that could be interpreted as eroded bedrock, basin sediment infill, channel cuts, deltaic progression with periods of both regression and transgression. 

Channel entrance to the old harbour of Split

The potential for mapping multiple palaeo-landscapes and associated environments is huge. We now need a program to accomplish this that has ground truth from coring and careful modelling.  The project has only just begun so here is looking forward to returning and working with a great team.