Unit:
Κατεύθυνση Περιβάλλοντα Ιζηματογένεσης, Οικοσυστήματα και ΓεωβιοπόροιLibrary of the School of Science
Supervisors info:
Μαρία Τριανταφύλλου, Καθηγήτρια, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Τομέας Ιστορικής Γεωλογίας και Παλαιοντολογίας
Κατερίνα Κούλη, Αναπληρώτρια Καθηγήτρια, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Τομέας Ιστορικής Γεωλογίας και Παλαιοντολογίας
Μαργαρίτα Δήμιζα, Αναπληρώτρια Καθηγήτρια, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Τομέας Ιστορικής Γεωλογίας και Παλαιοντολογίας
Original Title:
Paleoenvironmental evolution of Pliocene sapropelic layers in the South Aegean Sea, NE Mediterranean
Translated title:
Paleoenvironmental evolution of Pliocene sapropelic layers in the South Aegean Sea, NE Mediterranean
Summary:
One of the most challenging features of the long-term Cenozoic climatic evolution, with some analog potential for present/ future global climate change, is the last sustained warm and high-atmospheric CO2 interval in Earth's history, which started after the end of the Messinian Salinity Crisis (5.971–5.332 Ma) in the Mediterranean Sea. The Messinian/ Pliocene boundary commonly includes a transitional organic-rich interval, followed by early Pliocene marine deposits. The early Pliocene is the most recent period in Earth history when the average global temperature (2.70–4.05 °C or 3–9 °C according to climatic models) and multi-proxy (e.g. Uk’37) paleothermometers and sea-level (5–70m) were higher than today. Moreover, the atmospheric carbon dioxide concentrations (pCO2) were close to or slightly above modern values, between 330 and 400 ppm. The study of benthic foraminiferal assemblages is of high importance, as benthic foraminifera can be used as indicators for reconstructing environments of the past. The availability of more complete DSDP sedimentary successions containing well - preserved benthic assemblages of the Early Pliocene Cretan Basin, which were studied in order to determine the past environmental conditions, to observe the different foraminiferal assemblages and identify the existence of Early Pliocene potential sapropelic layers and the comparison of the conditions in which Early Pliocene potential sapropelic layers were deposited with the conditions that characterized the deposition of sapropel S1 during Holocene in the Aegean Sea and wether we can observe similar trends.
The study of the benthic foraminiferal assemblages of the Early Pliocene Cretan Basin indicates that the area was characterized by open marine conditions with periods of high organic flux and low oxygen rates. The benthic foraminiferal fauna of the area consists of normal-sized specimens with an increasing abundance of lower epibathyal fauna (i.e. Bolivina spp., B. costata, U. pregrina) and periodic occurences of some epiphytic taxa (i.e. C. lobatulus, Neoconorbina sp., C. refulgens) that are the product of in-basin transfer. Five potential sapropelic layers were observed through the micropaleontological study in the interval 4 – 437cm core depth. The potential sapropelic layers showcase low values of Benthic Foraminiferal Oxygen Index and Redeposition Index, indicating low oxic conditions with high values of infaunal species Bolivina spp., B. costata and U. pregrina. Additionally, 3 distinct Low Oxic events occurred in the interval 485 – 755cm core depth. During these low oxic events, BFOI values continue to indicate low oxic conditions, however there is major increase of oxic indicator species C. pseudoungerianus and S. reticulata that point to a better oxygenation of the sea floor.
The results that are acquired from this study can offer insight to the deposition trends of the Early Pliocene depositions that share similar characteristics with sapropelic layers and indicate that their formation conditions are similar to those of sapropel S1 (10.2–6.4 ka BP) during Holocene in the Aegean Sea. The Early Pliocene benthic foraminiferal assembladges are heavily impacted by organic flux and dissolved oxygen fluctuations and as a result are dominated by infaunal taxa that can tolerate low oxygen levels in the potential sapropelic layers and with higher abundances of oxic indicator species in the Low Oxic events, as in the case of sapropel S1, which is characterized by severe dysoxic conditions, interrupted with episodes of better oxygenation of bottom waters in the Aegean Sea.
Main subject category:
Science
Keywords:
Paleoenvironment, benthic foraminifera, Pliocene, sapropels, Aegean Sea
