Jurassic microfossils of DSDP Hole 79-547B

The first marine incursion of the incipient North Atlantic Ocean is recorded in the uppermost Triassic to Lower Jurassic sequence of DSDP Site 547 off central Morocco. A lithologic change from continental red beds below to slope breccias and hemipelagic carbonates above indicates that a carbonate ramp was probably established by Sinemurian time along the Moroccan continental margin and that subsidence in the adjacent basin was rapid in the early phases of continental rift. Foraminifers recovered from the Liassic (Sinemurian-Pliensbachian) basinal deposits are diverse and well preserved. The faunas are compositionally similar to contemporaneous neritic assemblages of Europe and the Grand Banks of Newfoundland. The Middle Jurassic in Hole 547B is characterized by regressive deposits that are poor in foraminifers. The major Late Jurassic "Atlantic" transgression is again represented by basinal deposits consisting of limestone breccias and pelagic carbonates. Foraminifers recovered from this interval are transitional between Late Jurassic assemblages reported from deep-sea deposits in the North Atlantic and typical Late Jurassic neritic assemblages of Europe. The Late Jurassic assemblages of Hole 547B are primarily dominated by nodosariids and spirillinids with moderate abundances of simple arenaceous forms. Nonreticulate epistominids occur very rarely in the Upper Jurassic of Hole 547B. It is tentatively suggested that these represent upper bathyal assemblages.

Planktonic foraminifera of ODP Hole 107-654A

The late Miocene sediments of the Tyrrhenian ODP Site 654 encompass a deepening sequence which begins with glauconite shallow water sands followed by a rapid transition to deep water sediments and culminates with dolomitic mudstones associated with Messinian evaporites. The sequence compares well with the so-called 'Sahelian cycle' and with post-orogenic cycles recognized in peninsular Italy and Sicily. The studied interval, consisting of 55 m thick nannofossil oozes, belongs to the Globorotalia suterae subzone and lower part of the Globorotalia conomiozea Zone, indicating late Tortonian and early Messinian age, respectively. Biomagnetostratigraphic correlation assigns the Tortonian/ Messinian boundary an age of 6.44-6.45 Ma. In addition, six main events have been recognized, based on the range of keeled globorotaliids and coiling direction changes of keeled and unkeeled globorotaliids, which have been correlated to the geomagnetic time-scale. Comparison with North Atlantic sites and land sections of the Guadalquivir basin and northern Morocco provides good correlations with the events documented in these areas. In particular, Event IV, which predates the FO of Globorotalia conomiozea, may be used to recognize the Tortonian/Messinian boundary in extra-Mediterranean areas where G. conomiozea is missing. Variations in the distribution of different species of Globigerinoides are related to changes in the surficial marine environment. Although no clear trends can be recognized on the oxygen and carbon isotope records of Globigerinoides obliquus, the parallelism between the occurrence of low salinity species (G. sacculifer) and peaks of low 5180 values, as well as that of normal salinity species (G. obliquus) and peaks of high d18O values, suggests strong local changes of environmental conditions. The high amplitude of the fluctuations of d18O values suggests important variations in the salinity of the Tyrrhenian Sea, related to a rapidly changing water budget. The major feature of the carbon isotope record is a large decrease between 7.0 and 6.95 Ma, which therefore predates the 6.2 Ma global 'carbon shift'.