Changes in fluvial spatial dynamics in various geomorphological systems as triggered by climatic changes (natural, human or both)

General theme: Changes in fluvial spatial dynamics in various geomorphological systems in response to controlling variables Study theme: Controls on fluvial incision in the lower Danube river during the Quaternary (between east of Olt river and Black Sea coast) Controls on fluvial incision of lower Danube riverFluvial incision can be controlled by several variables or processes and can result in development of a staircase of fluvial terraces (e.g. strath- and fill-types). A first factor controlling fluvial incision can be lowering of river base levels due to changes in the Black Sea level. An eustatic sea-level fall will cause the stream bed to steepen relative to the adjacent reaches, revealing a topographic knickpoint (Burbank and Andreson, 2001). The river will erode across this threshold until will attain a new equilibrium profile, a steady effective discharge associated neither with aggradation nor degradation. Multiple sea-level drops cause upstream migration of the knickpoint due to bedrock erosion (upstream retreat), leaving behind abandoned floodplains, which become terrace levels. The Danube river outlet is represented by its delta that directly connects with the Black Sea. If sea-level changes would affect the fluvial incision, this would lower the river outlet in its lower reaches (Maddy, 1997; Maddy et al., 2000; Vandenberghe et al., 2011). If the Black Sea level fluctuations would cause lowering of the Danube base-level associated with upstream migration of the knickpoint and development of fluvial terraces, likewise, it should happen for its major tributaries (e.g. Olt, Arge, Ialomia, Siret, Prut), where fluvial terraces with similar ages should be present. .

A sea-level rise will cause the river to deposit along its course, with fluvial deposits becoming younger upstream, away from the sea shore . Lowering of the sea-level can generally attributed to sea-level fluctuations caused by the glacial-interglacial cycles.

Danube fluvial incision depends on the rock substratum in which this river is cutting its course. This substratum is represented by the Upper Miocene-Quaternary sedimentary deposits of the Dacic basin and older Palaeogene and Mesozoic deposits of the Moesian platform. Evolution of the Dacic basin is closely linked with the western Black Sea basin. The Dacian and Black Sea basins were disconnected during the Early-Middle Pontian (Munteanu et al., 2012). A Middle Pontian sea-level fall, equivalent to the Messinian Salinity Crisis (Krijgsman et al., 1999), was differently recorded by these basins due to a barrier located along the Scythian gateway (Dobrogea bulge). The sea-level drop reached 1.7-1.3 km in the Black Sea (Munteanu et al., 2012), and 100 and 200 m in the northern part (Stoica et al., 2013) and southern part (Leever et al., 2010) of the Dacic basin, respectively. The two basins were connected during the Upper Pontian-Dacian (Munteanu et al., 2012), when shallow water was present in the Dacian basin, and shelf and deep marine existed in the Black Sea. The Late Pliocene-Quaternary endemic evolution took place in the Black Sea (Winguth et al., 2000; Aksu et al., 2002; Hiscott et al., 2007; Lericolais et al., 2010), where a sea-level fall enhanced transport of large volumes of sediments towards the deeper part of the basin. An increase in the sedimentary input was recorded in the Danube discharge area during the Quaternary, coeval with inferred moments of complete basin fill (or complete basin drain) in the Focani area (Dinu et al., 2005; Gillet et al., 2007). The Black Sea level dropped ~150 m during the early Middle Pleistocene (Winguth et al., 2000), when the Dacic basin was entirely filled with sediments. The duration of the water level cycles, identified in the north-western Black Sea for the last 900 ky (Middle Pleistocene to Holocene), varies between 50 and 130 ky (Winghuth et al., 2000), which are 6th and 5th order cycles in the sense of Fulthorpe (1991) and Carter et al. (1991) and can be correlated with the eccentricity and obliquity cycles of Milankovitch (1941). The drainage network presently debouching in the western Black Sea did not reach this area during the Pliocene based on the large-scale delatic sedimentation taking place in the Dacic basin (Jipa and Olariu, 2009).

A second control can be Pleistocene climatic changes, which in Romania are indicated by the U-shaped glacial valleys with basal moraines preserved in the mountains and by the loess sequences largely occurring in the flat areas of the Moesian platform. Glacial valleys occur on the northern slope of the South Carpathians and the northern part of the East Carpathians above 1700 m above sea level (a.s.l.) (Mndrescu et al., 2010; Necea et al., 2013), with glacial moraines preserved above 1200-1400 m a.s.l. (Urdea, 2004; Urdea and Reuther, 2009). The onset of glaciation in Romania can be placed in the upper Middle Pleistocene and affected mainly the South and East Carpathians as dated by 10Be exposure of glacial moraines in the South Carpathians (Late Pleistocene; Reuther et al., 2007) and by U-series of Scrioara ice cave from the Apuseni Mountains (350 kyr, upper Middle Pleistocene; Onac, 2001). The SE Carpathians, lowland plains (generally Romanian and Moldavian), and areas within the Transylvanian and Braov basins were possibly in a non-glacial setting, under a still cold climate associated with upper Middle to Late Pleistocene loess deposition. Deposition ages resulted from luminescence dating in the Braov intramontane and Focani foredeep basins (Late Pleistocene and upper Middle Pleistocene, respectively; Necea et al., 2013) and in the Danube plain (Blescu et al., 2003, 2010), and from palaeomagnetism studies also in the Danube plain (Panaiotu et al., 2001). The Lower Danube reach was in a non-glacial setting, which implies that glacial terraces are not present in this area and that the climatic changes may be partly responsible for fluvial incision.A third factor can be uplift trigged by local tectonics. Lowering of the river base-level can also be caused by the tectonic uplift, which leads to topographic growth and consequent fluvial incision. The Lower Danube area on the Romanian territory is cut by the NW-SE-trending major Intramoesian and Peceneaga-Camena faults occurring to the west and east, respectively. These faults had a transtensional dextral movement during the (Late Miocene) Late Pliocene-Quaternary (Trpoanc et al., 2003). Young ENE-WSW-trending sinistral strike-slip faults were reported on a larger extent of the Moesian platform, which could be considered as conjugates of the Intramoesian and Peceneaga-Camena faults (Rbgia and Trpoanc, 1999; Rbgia et al., 2000; Trpoanc et al., 2003). ENE-WSW-striking normal faults separated by transfer zones are mainly found between the Peceneaga-Camena shear zone and the Ostrov-Sinoe fault to the south, while older faults were reactivated as either sinistral or normal faults displaying uplifted northern blocks (Trpoanc et al., 2003).

In the Lower Danube reach on the Bulgarian territory, the Pliocene-Quaternary dextral transtension with a NNW-SSE to NNE-SSW direction inherited and expanded the existing graben structures (Bergerat et al., 2010), associated with NNE-SSW- and WNW-ENE-trending normal faults. This transtension can be linked with the right-lateral eastward movement of the North Anatolian fault zone . The Lower Danube course might have been influenced by the major strike-slip faults, causing the river to change its course from W-E to S-N and ultimately again to W-E. The Quaternary and older downward movements along the Intramoesian and Peceneaga-Camena faults might have caused the roughly uniform tilting of the southern foreland (Trpoanc et al., 2003). This might have induced burial of existing fluvial terrace, which were subsequently covered by recent sediments. Older terrace levels of the Danube river are found buried at several tens of meters as evidenced by data from hydrological wells (Enciu et al, 2015). Methodological approach:

Factors controlling fluvial incision can be derived from studying distribution of fluvial terraces, terrace type, pattern of fluvial incision and its relationship with main structural elements. These will serve ultimately to reconstruct the palaeoclimatic conditions. Terrace distribution can be obtained from extracting terrace contours from published geological and geomorphological maps combined with data from public literature. Terrace contours can be then plotted against satellite imageries with different resolutions (e.g. 90 m for SRTM DEM, 30 m for Landsat ETM+, 10 m for ALSO Pulsar, 0.5-1 m for WV3) for better defining the terrace edges. Fieldwork will help to verify and correct terrace extent and terrace type (e.g. strath vs. fill). Terrace distribution within the Lower Danube area and its major tributaries across the Moesian platform (e.g. Olt, Arge, Ialomia, Siret, Prut rivers) will give insights on terrace formation order (old to young direction), migration of knickpoint(s) (upstream vs. downstream) and its relationship relative to lithology, structural elements and river intersections. Terrace type (strath- or fill type) will results from field observations. Terrace distribution and type can also result from studying hydrological (and hydrocarbon) wells to establish terrace presence and burial, especially to the east in the lower reaches of the Danube river. Pattern of fluvial incision will result from quantifying the amount of vertical fluvial incision and terrace formation age resulting from dating of terrace erosional surfaces. The amount of fluvial incision will be extracted from SRTM DEM and field measurements, whereas terrace age will result from infrared stimulated luminescence (IRSL) dating of loess and/or fine fluvial deposits covering terrace erosional surfaces.

Plotting river courses versus main structural lineaments and structures will serve to assess if and how rivers responded to recent tectonic movements. River courses can be automatically extracted from SRTM DEM or Landsat imageries, whereas structural lineaments and structures can be complied from published geological maps and literature combined with interpretation from satellite imagery.

Comparing terrace extent with reconstructed glaciated areas will give insights if there is any link and control by the glaciers. Glacier distribution (including glacial lakes) is currently done by geographers at Suceava Univ. (Department of R. Rdoane).

Reconstruction of palaeoclimatic conditions (warm/cold periods, glacial/interglacial periods) and their correlation with the Romanian and European loess chronologies serve to establish the link between formation and abandonment of fluvial incision and terraces and deposition of loess-palaeosol sequences. Key profiles with large exposures of sequences formed above the Upper Miocene to Lower Quaternary strata. Several locations can be found through the Romanian plain. References

Aksu, A.E., Hiscott, R.N., Yasar, D., Isler, F.I., Marsh, S., 2002. Seismic stratigraphy of Late Quaternary deposits from the Southwestern Black Sea Shelf: evidence for non-catastrophic variations in sea-level during the last ~10000 Yr. Mar. Geol., 190, 61-94.Blescu, S., Lamothe, M., Mercier, N., Huot, S., Blteanu, D., Billard, A., Hus, J., 2003. Luminescence chronology of Pleistocene loess deposits from Romania: testing methods of age correction for anomalous fading in alkali feldspars. Quat. Sci. Rev. 22, 967-973.

Blescu, S., Lamothe, M., Panaiotu, C., Panaiotu, C., 2010. La chronologie IRSL des squences lssiques de lest de la Roumanie. Quaternaire 21 (2), 115-126.

Bergerat, F., Vangelov, D., Dimov, D., 2010. Brittle deformation, palaeostress field reconstruction and tectonic evolution of the Eastern Balkanides (Bulgaria) during the Mesozoic and Cenozoic times. In Sosson, M., Kaymakci, N., Stephenson, R. A., Bergerat, F. and Starostenko, V. (Eds.), Sedimentary Basin Tectonics from the Black Sea and aucasus to the Arabian Platform. The Geological Society of London, Special Publications 340, 77-111. DOI: 10.1144/SP340.6 0305-8719/10.Burbank, D.W., Anderson, R.S., 2001. Tectonic geomorphology. Blackwell Science, Massachusetts, USA, pp. 274.

Dinu, C., Wong, H.K., ambrea, D., Matenco, L. ,2005. Stratigraphic and structural characteristics of the Romanian Black Sea Shelf. Tectonophysics 410, 417-435.Enciu, P., Blteanu, D., Dumitric, C., 2015. Contributions to the knowledge of Quaternary formations in the southwest Romanian Plain. Quaternary International 357, 58-69.

Fulthorpe, C.S., Carter, R.M., 1991. Continental shelf progradation by sediment-drift accretion. Geological Society of America Bulletin 103, 300-309. Gillet, H., Lericolais, G., Rehault, J.-P., 2007. Messinian event in the Black Sea: Evidence of a Messinian erosional surface. Marine Geology 244 (1-4), 142-165.

Hiscott, R.N., Aksu, A.E., Mudie, P.J., Marret, F., Abrajano, T., Kaminski, M.A., Evans, J., C, Akiroglu, A.I., Yasarr, D., 2007. A gradual drowning of the Southwestern Black Sea Shelf: evidence for a progressive rather than abrupt holocene reconnection with the Eastern Mediterranean Sea through the Marmara Sea Gateway. Quatern. Int. 167-168, 19-34.Krijgsman, W., Hilgen, F.J., Raffi, I., Sierro, F.J., Wilson, D.S., 1999. Chronology, causes and progression of the Messinian salinity crisis. Nature 400, 652-655.

Jipa, D.C., Olariu, C., 2009. Dacian Basin: Depositional Architecture and Sedimentary History of a Paratethys Sea. National Institute of Marine Geology and Geo-ecology, Bucharest.Lericolais, G., Bulois, C., Ggillet, H., Guichard, F., 2009. High frequency sea level fluctuations recorded in the Black Sea since the Lgm. Global Planet. Change 66, 65-75.Lericolais, G., Guichard, F., Morigi, C., Minereau, A., Popescu, I., Radan, S., 2010. A post younger Dryas Black Sea regression identified from sequence stratigraphy correlated to core analysis and dating. Quatern. Int. 225 (2), 199-209.Maddy, D., 1997. Uplift-driven valley incision and river terrace formation in southern England. Journal of Quaternary Research 12 (6), 539-545.

Maddy, D., Bridgland, D.R., Green, C.P., 2000. Crustal uplift in southern England: evidence from the river terrace records. Geomorphology 33, 167-181.

Mndrescu, M., Evans, I.S., Cox, N.J., 2010. Climatic implications of cirque distribution in the Romanian Carpathians: palaeowind directions during glacial periods. J. Quatern. Sci. 25,875-888. Munteanu, I., Matenco, L., Dinu, C., Cloetingh, S., 2012. Effects of large sea-level variations in connected basins: the Dacian-Black Sea systemof the Eastern Paratethys. Basin Research 24 (5), 583-597. Necea, D., Fielitz, W., Kaderiet, A., Andriessen, P.A.M., Dinu, C., 2013. Middle Pleistocene to Holocene fluvial terrace development and uplift-driven valley incision in the SE Carpathians, Romania. Tectonophysics 602, 332-354. Onac, B., 2001. Mineralogical studies and Uranium-series dating of speleothems from Scrioara Glacier Cave (Bihor Mountains, Romania). Theoretical and Applied Karstology 13-14, 33-38.

Panaiotu, C.G., Panaiotu, C.E., Grama, A., Necula, C., 2001. Paleoclimatic Record from a Loess-Palaeosol Profile in Southeastern Romania. Phys. Chem. Earth (A) 26, 893-898.

Rbgia, T., Trpoanc, M, 1999. Tectonic evolution of the Romanian part of the Moesian platform: Trpoanc et al., Architecture of the Focani depression X-17, An integrated model, in Dobrogea: The Interface Between the Carpathians and the Trans-European Suture Zone, Europrobe TESZ/PANCARDI/GeoRift, Abstract Vol., edited by L. Matenco, D. Ioane, and A. Seghedi, Rom. J. Tect. Reg. Geol., 77, Suppl. 1, 58, 1999.

Rbgia, T., Trpoanc, M., Dinu C., Smith, R., 2000. Neotectonics of the Moesian platform: Seismic implications, in SEG/EAGE/RSG Bucharest International Geophysics Conference and Exhibition, Conference Volume, edited by R. G. Dimitriu and D. Ioane, Rom. Geophys., 7, Suppl. 1, 284-285, 2000.

Reuther, A.U., Urdea, P., Geiger, C., Ivy-Ochs, S., Niller, H.P., Kubik, P.W., Heine, K., 2007. Late Pleistocene glacial chronology of the Pietrele valley, Retezat Mountains, Southern Carpathians constrained by 10Be exposure ages and pedological investigations. Quaternary International 164-165, 151-169.

Stoica, M., Lazr, I., Krijgsman, W., Vasiliev, I., Jipa, D., Floroiu, A., 2012. Paleoenvironmental evolution of the East Carpathian foredeep during the late Miocene-early Pliocene (Dacian Basin; Romania). Global and Planetary Change, In Press, Corrected Proof.

Trpoanc, M., Bertotti, B., Matenco, L., Dinu, C., Cloetingh, S., 2003. Architecture of the Focani Depression: a 13 km deep basin in the Carpathians bend zone (Romania). Tectonics 22 (6), 1074.

Urdea, P., 2004. The Pleistocene glaciation of the Romanian Carpathians. In: Ehlers, J., Gibbard, P.L. (Eds.), Quaternary Glaciations-Extent and Chronology, Part 1 Europe, Elsevier B.V., The Netherlands, 301-308.

Urdea, P., Reuther, A.U., 2009. Some new data concerning the Quaternary glaciation in the Romanian Carpathians. Geographica Pannonica 13 (2), 41-52.

Vandenberghe, J., Wang, X., Lu, H., 2011. Differential impact of small-scaled tectonic movements on fluvial morphology and sedimentology (the Huang Shui catchment, NE Tibet Plateau). Geomorphology 134, 171-185.

Winguth, C., Wong, H.K., Panin, N., Dinu, C., Georgescu, P., Ungureanu, G., Krugliakov, V.V., Podshuveit, V., 2000. Upper Quaternary water level history and sedimentation in the northwestern Black Sea. Marine Geology 167 (1-2), 127-146.