Date of Award
Doctor of Philosophy (PhD)
Gifford H. Miller
Charles E. Stearns
The Mediterranean has been a natural laboratory for shoreline studies for nearly a century. From the prodigious number of previous research programs, several groups of raised shoreline deposits have been identified that are related to early, middle, and late Pleistocene marine transgressions. Inter- and intra-regional correlations are complicated by localized tectonic uplift and inadequate chronometry. This investigation was initiated to attack some of the outstanding dating problems by using the extent of isoleucine epimerization in fossil shells contained in shoreline deposits as an independent assessment of age.
The regional study includes 78 sites in Crete, Italy, Sicily, Sardinia, Corsica, Tunisia, Spain, Hallorca, Morocco and the Canary Islands. Alle/Ile ratios have been determined in 762 shell samp~es of 23 genera, although the main contributions are based on ratios from the genera Glycymeris, Arca, Astralium and Patella. Six aminogroups (samples of equal age but having variable temperature histories) have been defined over the region and are labeled A, C, E, F, G and K with increasing age. Eight U-series dates on the corals Cladocora caespitosa and Astroides sp. obtained in this study, and several other previously determined radiometric dates have provided absolute age calibration for some of the aminogroups.
Aminogroup A is defined from deposits representing the Holocene beach-dune complex mainly from coastal deposits in Mallorca. Aminogroup C includes most previously identified Neotyrrhenian deposits and is correlated to a late isotopic stage S (Sa or Sc or both) rapid and brief marine transgression. Aminogroup E, the Eutyrrhenian, is positively correlated to isotopic stage Se by seven coral dates averaging 126 ± 4ka (kilo anni). Strombus bubonius and other "Senegalese fauna" are intimately associated with the aminogroup E transgression and the Eutyrrhenian. Little independent evidence exists to imply an earlier or later than stage Se presence of these exotic taxa. Future studies will attempt to resolve some of these exceptional cases. Aminogroups F and Gare of mid Pleistocene age (cf. Paleotyrrhenian) but ambiguous U- series dates can only tentatively tie these aminogroups to isotopic stages 7 and 9 or 9 and 11. Amino acid epimerization kinetics indicate that aminogroup G is less than 500ka old. iv Aminogroup K represents multiple early Pleistocene deposits of Sicilian and Calabrian age.
This study demonstrates the potential of amino acid geochronology for dating and correlation of disjunct marine deposits distrubuted over a large area. Future studies will concentrate on obtaining additional absolute age calibration during the interval between 200 and 400ka. Further efforts will also focus on correlation of the coastal record with deep sea cores.
Hearty, Paul J., "Age and Aminostratigraphy of Quaternary Coastal Deposits in the Mediterranean Basin" (1987). Geological Sciences Graduate Theses & Dissertations. 136.