Elisabeth Fourtanier

ADDENDUM TO “CATALOGUE OF THE DIATOM GENERA”

This addendum to “Catalogue of the diatom genera” (Fourtanier & Kociolek, Diatom Research, 14, 1–190, 1999) includes nomenclatural information for 93 generic names, most of which were published in the last 6 years. The data for each name include authorship, place of publication with pages on which the protologue appears, date of publication, generitype, nomenclatural status and systematic position of the genus.

Stratigraphic Implications of Latest Middle Miocene to Earliest Late Miocene Diatoms in the Navidad Formation at Lo Abarca, Central Chile (33° 30'S)

Neogene marine strata crop out at various localities along the Chilean coastline (see Encinas et al., 2008 and references therein). The best studied of these successions occurs in the Navidad area, between San Antonio and Punta Topocalma (33°30’34°30’S) (figure 1). Named and described by Darwin (1846) as the Navidad Formation, the geology and paleontology of this unit was subsequently studied by many other authors (e.g., Philippi, 1887; Brüggen, 1950; García, 1968; Tavera, 1979) and has been considered the stratigraphic reference for the marine Neogene of Chile (e.g., Cecioni, 1980; De Vries and Frassinetti, 2003). However, its age, stratigraphy and depositional environment were a matter of debate for several decades (e.g., Brüggen, 1950; García, 1968; Tavera, 1979; Encinas et al., 2006). Recent foraminiferal and sedimentologic studies indicate a late Miocene to early Pliocene age and a deep-marine setting for this unit (Finger et al., 2007; Encinas et al., 2008). Yet, the older latest Oligocene to middle Miocene age proposed for the molluscan fauna of this unit (De Vries and Frassinetti, 2003) still constitutes an unresolved problem (see below). North of the Navidad area, between Valparaíso and San Antonio (33°00’?33°30’S), Neogene successions have been traditionally referred to as the “capas de Lo Abarca” (Covacevich and Frassinetti, 1990) (figure 1). These strata have been considered equivalent to the Navidad Formation by some authors (Brüggen, 1950; Fuenzalida and Varela 1964; Encinas et al., 2006) and as a different unit by others (Martínez-Pardo and Parada, 1968; Covacevich and Frassinetti 1990). The main argument for distinguishing the successions is based on their different molluscan faunas (Covacevich and Frassinetti, 1990). Nevertheless, Encinas et al. (2006) considered both successions as corrrelative and included the Lo Abarca strata in the Navidad Formation because their diatoms and foraminifera indicate similar ages and both units show similar facies. Essential to the age constraint of the Lo Abarca succession and its correlation with the Navidad Formation is the diatom assemblage found at Lo Abarca section that we document in this note.

Oligocene Age of the Classic Belén Fruit and Seed Assemblage of North Coastal Peru based on Diatom Biostratigraphy

The Belén flora, in north coastal Peru, is the most diverse fruit and seed assemblage yet known from the Paleogene of South America. Little original paleobotanical work has been performed on this assemblage since the pioneering treatments published by E. W. Berry in the 1920s, and the precise age has not been determined. Nevertheless, the flora has been regarded as a focal point in understanding the vegetational, orogenic, and climatic history of northern South America, and in recent literature it has been assumed to be early Eocene. In order to tighten this age assignment, which has varied from early Eocene to early Oligocene in the opinions of different authors, we revisited the Belén site, measured the stratigraphic section, and processed the fruit- and seed-containing sediment for age-diagnostic microfossils. Although pollen and foraminifera were not recovered, the sediment is rich in diatoms. The diatom assemblage includes Lisitzinia ornata and Rocella vigilans, among others, indicating a latest early Oligocene age (∼30–28.5 Ma) for these deeper marine sediments, which we infer to have been subsequently reworked into the Belén environment. We also reevaluate the botanical identifications, which are based on the original museum specimens supplemented by more recently collected specimens. The Belén flora provides a window into extinct forests in South America that were present before the rising of the Andes in western Peru.

MORPHOLOGICAL STUDIES OF AULACODISCUS SPECIES FROM THE “RUSSIAN COLLECTION” OF THE CALIFORNIA ACADEMY OF SCIENCES

Our investigation focused on the morphology of Aulacodiscus species from the Russian sediment samples curated at the California Academy of Sciences, mostly from the localities of Kamishev, Carlovo, Ananino and Singelievsky. Our observations suggest that useful characters potentially defining infrageneric taxa include valve relief, shape and position of the external tubes of the rimoportulae, shape of the internal expression of the rimoportulae, shape and orientation of the internal rimoportula slit, structure of the areolae and vela and presence or absence of bullulae in the wall.