Late Neogene time scale for ODP Leg 138 sites

The sediments recovered during Leg 138 provide a remarkable opportunity to improve the geological time scale of the late Neogene. We have developed new time scales in the following steps. First, we constructed age models on the basis of shipboard magnetostratigraphy and biostratigraphy, using the time scale of Berggren, Kent, and Flynn (1985). Second, we refined these age models using shipboard GRAPE density measurements to provide more accurate correlation points. Third, we calibrated a time scale for the past 6 m.y. by matching the high-frequency GRAPE density variations to the orbital insolation record of Berger and Loutre (1991); we also took into account d18O records, where they were available. Fourth, we generated a new seafloor anomaly time scale using our astronomical calibration of C3A.n (t) at 5.875 Ma and an age of 9.639 Ma for C5n.1n (t) that is based on a new radiometric calibration (Baksi, 1992). Fifth, we recalibrated the records older than 6 Ma to this new scale. Finally, we reconsidered the 6- to 10-Ma interval and found that this could also be partially tuned astronomically.

Relationship between definitive datum levels and magnetic polarity and revised geomagnetic polarity time-scale at DSDP Hole 72-516F

This paper contains magnetobiostratigraphic correlation charts for each of the four sites occupied during DSDP Leg 72. Microfossil zonal boundaries and magnetic polarity determinations for Sites 515 through 518 are summarized in Figures 1 through 4, respectively. Our discussion focuses on the correlations derived for the Paleogene and late Cretaceous (Coniacian-Maestrichtian) of Site 516, because of the value of this site as a stratigraphic reference section for the South Atlantic.

(Table 2) Age controls used to derive a time scale for DSDP Site 73-522

The stratotype section for the base of the Miocene is at a reversed (below) to normal (above) magnetic transition that is claimed to represent magnetic chron C6Cn.2n (o). Deep Sea Drilling Project (DSDP) Site 522 is the only location we are aware of that unambiguously records the three normal events of C6Cn. We have quantitatively determined the range of the short-lived nannofossil Sphenolithus delphix and the lower limit of S. disbelemnos in DSDP Holes 522 and 522A in order to calibrate their precise relationship to the magnetostratigraphy and to confirm the completeness of the record at this site. Astronomical tuning of Ocean Drilling Program (ODP) Sites 926, 928, and 929 shows that S. disbelemnos appears at 22.67 Ma and that the entire range of S. delphix is from about 22.98 Ma to 23.24 Ma. Using these ages, linear interpolation in DSDP Site 522 suggests that the age of C6Cn.2n (o) and of the Oligocene-Miocene boundary is 22.92+/-0.04 Ma. Our value, conservatively expressed as 22.9+/-0.1 Ma, is 0.9 m.y. younger than the currently accepted age of the Oligocene-Miocene boundary and of C6Cn.2n (o), which was assigned an age of 23.8 Ma, based on an estimate of 23.8+/-1 Ma for the Oligocene-Miocene boundary. The bulk-sediment carbon isotope data from DSDP Site 522 is correlated to the record from benthic foraminifera at ODP Site 929 to refine the calibration of magnetic reversals from C6Cn.1n (o) to C7n.2n (o) at DSDP Site 522 on the astronomical time scale.

Electrical Power Fluctuations in a Network of DC/AC inverters in a Large PV Plant: relationship between correlation, distance and time scale

This paper analyzes the correlation between the fluctuations of the electrical power generated by the ensemble of 70 DC/AC inverters from a 45.6 MW PV plant. The use of real electrical power time series from a large collection of photovoltaic inverters of a same plant is an impor- tant contribution in the context of models built upon simplified assumptions to overcome the absence of such data. This data set is divided into three different fluctuation categories with a clustering proce- dure which performs correctly with the clearness index and the wavelet variances. Afterwards, the time dependent correlation between the electrical power time series of the inverters is esti- mated with the wavelet transform. The wavelet correlation depends on the distance between the inverters, the wavelet time scales and the daily fluctuation level. Correlation values for time scales below one minute are low without dependence on the daily fluctuation level. For time scales above 20 minutes, positive high correlation values are obtained, and the decay rate with the distance depends on the daily fluctuation level. At intermediate time scales the correlation depends strongly on the daily fluctuation level. The proposed methods have been implemented using free software. Source code is available as supplementary material.