Marine Notches Research Articles

Late Holocene coastal tectonics at Falasarna, western Crete: a sedimentary study

Abstract The late Holocene sedimentary record of Falasarna Harbour, western Crete, includes detailed evidence of tsunamis and serves as an independent dataset to evaluate the magnitude and timing of coastal tectonic movements in an area affected by contrasting tectonic regimes. Analysis of a foraminiferal assemblage makes it possible to identify suites of tsunami-deposited sediments within normal sedimentary sequences. The palaeo-environmental record is then complemented with a sequence of raised fossil marine notches. The transitional boundary between marine and terrestrial sedimentation indicates tectonic uplift at c. ad 63–75 ± 90 radiocarbon years bp , which is in conflict with previously published interpretations. No sedimentary evidence can be found for a tsunami believed to be associated with a large uplift event during ad 365.

Quaternary uplifted coral reef terraces on Alor Island, East Indonesia

A flight of six major coral reef terraces, up to 700 m in altitude, occurs along the eastern and northern sides of Kabola Peninsula, Alor Island, Indonesia. Some radiometric dates have been obtained from unrecrystallized coral samples collected in growth position by three different methods (14C, 230Th/234U, ESR). This enabled the identification of the terraces corresponding to the Holocene and to oxygen-isotope stages 5c, 5e and 7. According to the present elevation of the dated terraces, a 1.0–1.2 mm/y mean rate of uplift can be discerned. Extrapolation of this trend to the whole sequence of terraces reveals a good correlation between the development of major terraces and interglacial or interstadial stages corresponding to astronomically calibrated oxygen isotope records, up to stage 13. The relatively rapid uplift rate in this region minimized the possibility of polycyclic sea-level stands at the same levels and contributed to the good preservation of some morphological reef features. Two superimposed marine notches are visible near the present shoreline, with retreat points at about 5.0 m and 8.6 m respectively above the present MLWST level. They can be interpreted as corresponding to a glacial interstadial (the upper notch) and to the Holocene sea-level peak (the lower one). As Holocene emergence has been less than what could be expected from a 1 mm/y rate of uplift, a major coseismic vertical displacement may occur in the future.

Seleucia Pieria: an ancient harbour submitted to two successive uplifts

Historical sources ascribe the foundation of Seleucia (Seleukeia) Pieria to Seleucos I Nikator, shortly before the foundation of Antioch in the late 4th century BC. The Seleucia Pieria site seems however to have been inhabited earlier, perhaps from around 700 BC, possibly by a Greek population under an Assyrian ruler. The city became of considerable military importance during the wars between the Ptolemies and the Seleucids; it was occupied by the Romans in the 1st century BC, but had practically disappeared in the 6th century AD. Geomorphological surveys in the area have revealed the existence of elevated marine notches and rims bioconstructed by vermetids, oysters and calcareous algae, which occasionally erode or intersect the archaeological sites, showing that two rapid land uplift movements, probably of seismic origin, took place during the late Holocene. The first movement, which occurred about 2500 ± 100 years bp, was the strongest one and caused a local vertical displacement of about 1.7 m, which may have severely affected the earlier Greek settlement. Though several earthquakes are reported to have occurred in the area during the following ten centuries, none of them seem to have been strong enough to cause significant vertical displacements. The second movement occurred around 1400 years bp, probably in May 526 AD, when a great earthquake followed by tsunami waves is known to have caused devastating damage in Antioch and Seleucia. According to geomorphological data supported by several radiocarbon dates, the earthquake was accompanied by a 0.7 to 0 8 m upheaval. This seismotectonic event also caused a rapid silting of the Seleucia Pieria closed harbour basin and entrances, thus preventing its further use.

Le gisement Paléolithique inférieur de Ménez-Drégan 1 (Plouhinec, Finistère)

Ménez-Drégan I (Brittany, France) fits in the « Colombanian » regional group, defined in the South-Armorican area. It is a very important site for the study of the Lower Palaeolithic of North-Western France. The prehistoric settlements were sheltered in an old marine notch, where two pebble layers have been deposited. The first palaeolithic layer is at the top of the first fossil beach. At the top and above the second beach, five other humic layers with many stone tools, are stratified. The whole is covered by a periglacial head and a pleistocene dune. Remains of fire-places have been founded. The abundant industry is characterized by heavy pebble-tools (sandstones, quartzites, microgranite...) and by lighter tools made from flint flakes. Choppers are very more numerous than chopping-tools. Other usual tools are mainly notches and denticulates. This dwelling position (in an old marine notch), on a pebble beach, is very characteristic of the Colombanian. It seems that the human settlements took place at the end of an ancient interglacial stage. No concluding evidence for more precise dating is acceptable, but the hypothesis of an occupation at the end of the isotopic stages 9 or 11 is possible and must be verified.

Sea-Level Research: A Manual for the Collection and Evaluation of Data

IGCP Projects 61 and 200. Sea-level changes in the Holecene. Sea-Level indicators: Elevation and age relationships: raised marine deposits and landforms in glaciated areas. Sea-level markers in coastal barrier sands: examples form the North Sea coast. Marine molluscs as indicators of former sea-level stands. Beachrock as sea-level indicator. Ooids as sea-level indicator. Corals and reefs as indicators of paleo-sea levels, with special reference to the Great Barrier Reef. Coralline algae as indicators of sea-level. Vermetid gastropods as sea-level indicators. The diagenetic products of marine carbonates as sea-level indicators. Marine notches. Submerged forests as sea-level indicators. Analysis of botanical macro-remains. Foraminafera as sea-level indicators. Diatoms as indicators of sea-level change. Shell middens as a source for additional information on Holocene shoreline and sea-level reconstruction: examples from the coast of Brazil. Age: Radiocarbon dating. Dendrochronological dating. Altitude: Determination of altitude. Compaction and consolidation.

Late Holocene sea level indicators from twelve atolls in the central and eastern Tuamotus (Pacific Ocean)

New sea-level data for the late Holocene period are reported from twelve atolls of the Tuamotu archipelago: Faaite, Hikueru, Marokau, Hao, Amanu, Tatakoto, Pukarua, Nukutavake, Vairaatea, Tureia, Nukutipipi, and Hereheretue. The data come from coral conglomerate outcrops, coral colonies in growth position, in situ reef framework and marine notches; they give consistent results, and their ages are controlled by 29 radiocarbon datings. The Holocene MSL remained 0.8±0.2 m higher than at present, from before 4000 years BP until at least 1500 years BP, then dropped gradually to the present level. This pattern is very similar to that reported from the northwest Tuamotus, suggesting the absence of measurable differential vertical movements over a distance greater than 1300 km during the late Holocene. Effects of the 1983 cyclones on reef morphology are reported from some atolls and radiocarbon dates of some storm-generated reef blocks are given.

琉球列島南部における完新世の海岸地形および海水準

1. Marine terraces, marine notches, beachrock, in situ coral reef and emerged shellbeds are used as indicators of Holocene sea-levels in Kohama, Kuro and Hateruma Islands, the South Ryukyus. A sea-level slightly higher than the present one, about 1 m AMSL is found from ca. 3, 300 to 800yBP in Kohama and Hateruma Islands and about 1.5m AMSL at about 4, 200yBP in Kuro Island (Table 2). It is, however, difficult to distinguish local differences in these three islands, owing to the limited number of observations and some uncertainty in the value of some coastal features as indicators of former sea-level. Late Holocene emergence is very small. 2. Shorelines which records the culmination of Postglacial (Jomon) transgression at about 6, 000yBP have been found along many parts of the Japanese coastline. Such evidences of shorelines, however, have not been observed in these three islands. The buried notch in Kuro Island, covered by beachrock at ca. 4, 200yBP, may correspond to this early transgression. 3. The relative sea-level drop causing the emergence of marine features in several Ryukyu islands is a recent phenomenon. Slight emergence dated at ca. 800 to 600yBP occurs not only on Hateruma Island, but also on Yoron Island (DELIBRIAS and PIRAzz0LI, 1983), on central Okinawa Island (KAWANA and PIRAZZOLI, 1983) and on Tarama Island (PIRAZZOLI et al., 1984). 4. Deposits found on the southeast coast of Hateruma Island, can be interpreted as the result of a tsunami, which accompanied the great earthquake of 1771.

琉球列島,宮古島の後期完新世海面変動

The present sea level in Miyako Island is the highest recorded during the Holocene, determined by systematic investigation of marine notches and beachrocks occurring along the coast. The elevations of the retreat points of the notches are consistent with the present tidal range and exposure. All beachrocks which are known to be due solely to tidal conditions are situated at an intertidal or almost intertidal zone. Near-intertidal beachrocks have been dated 425±70 and 1520±60 y. B. P. (Loc. 13), and 2120± 75 y. B. P. (Loc. 31), showing a relative stability of sea level during at least the past 2100 years. This situation clearly differs from the Late Holocene emergence prevailing in most of the major axial islands in the Ryukyu Frontal Arc. Such a difference can be ascribed to recent crustal movements.