Sedimentary record of coseismic subsidence in Hersek coastal lagoon (Izmit Bay, Turkey) and the late Holocene activity of the North Anatolian Fault

Abstract

[1] The late Holocene activity of a restraining bend of the northern strand of the North Anatolian Fault in Izmit Bay was investigated by a sedimentological, geochemical, and paleoecological analysis of sediment cores from Hersek coastal lagoon, NW Turkey. The sediment cores show a succession of sedimentary sequences composed of three units separated by gradual transitions. The first unit is composed of a thin layer of shell debris-rich sediment in abrupt contact with the underlying organic-rich deposits. This unit is overlain by a thick foraminifera-rich mud deposit, and the sequences are capped by an organic-rich mud unit. These sequences are interpreted as silting up, shallowing upward deposits, typical of a lagoon becoming isolated from the sea. We suggest that they represent the sedimentary signature of coseismic subsidence, which was caused by reverse slip at the Hersek bend, and tsunamis in Izmit Bay. Our radiocarbon-dated paleoseismological record indicates (1) the atypical collapse of the hanging wall during the 740 earthquake and (2) subsidence of the footwall during the 987, 1509, and 1719 earthquakes. This study contributes to the understanding of the dynamics of restraining bends, and it highlights the potential of coastal sediments for reconstructing past earthquakes and tsunamis in regions dominated by strike-slip deformations.

Submarine Earthquake History of the Çınarcık Segment of the North Anatolian Fault in the Marmara Sea, Turkey

“…earthquake was associated with a large tsunami (Altınok et al, 2011). It has been generally located in the Çınarcık basin (Ambraseys, 2002;Guidoboni and Comastri, 2005), but some authors suggested an epicenter location in the Izmit Gulf or Central basin (McHugh et al, 2006;Bertrand et al, 2011;Çağatay et al, 2012). Historical information for older ages is limited, but Ambraseys (2002) located the 407 C.E.…”

Sedimentary records of past earthquakes in Boraboy Lake during the last ca 600 years (North Anatolian Fault, Turkey)

“…3 seismic shaking, surface faulting during earthquakes may also affect sedimentation, especially in shallow water environments (e.g., Mirecki, 1996;Leroy et al, 2009;Vologina et al, 2010;Bertrand et al, 2011). For example, tectonic subsidence in shallow basins may result in deepening of the lake and inundation of surrounding land, which may leave traces in the sedimentary sequence.…”

Recent high-energy marine events in the sediments of Lagoa de Óbidos and Martinhal (Portugal): recognition, age and likely causes

“…Similarly, during the late Maunder Minimum (AD 1675-1715), a period with reduced precipitation in southern Portugal can be deduced from the historical record, but with a rise entering the 18th century (Alcoforado et al, 2000). The Dalton Minimum was roughly between AD 1795 and AD 1825 (Kirov and Georgieva, 2002;Vaquero et al, 2006) and corresponds to a reduced number of floods in the Atlantic Tagus basin (Central Iberia; Benito et al, 2003).…”

“…Over the past 25 yr, an increasing number of investigations have dealt with the interpretation of the lithological signature of extreme marine invasions, mainly focusing on palaeotsunamis, but also on the comparison with large storms and their sedimentological signatures (e.g., Kortekaas and Dawson, 2007;Kunz et al, 2010;Bertrand et al, 2011). Due to specific depositional conditions, the sediment sequences in coastal lagoons are among the best geological settings to detect units deposited by abrupt marine invasions because the low energy of lagoons is suitable for the preservation and detection of sudden energy increases in their sedimentary record.…”