Thesis (Ph. D.)--Columbia University, 1975. / Includes bibliographical references (leaves 243-251).

Extensive fossil collections from the upper part of the Sandilands and the lowermost Ghost Creek Formations allowed a detailed taxonomic study of the latest Hettangian to earliest Phensbachian ammonoid fauna of the Queen Charlotte Islands. 61 taxa, allocated to 27 genera, are described. Sunrisites senihlevis, Plesechioceras yakounense, Tetraspidoceras pacificum and Tetraspidoceras recognitum are introduced as new species. The vertical distribution of ammonites, documented in measured sections, serves as a basis to distinguish six successive assemblage zones: the Canadensis Zone, "Coromceras" Zone, Arnouldi Zone, Varians Zone, Harbledownense Zone, and Recognitum Zone. Of these only the Canadensis Zone was established earlier, the remaining five are defined here for the first time. This zonation permits high-resolution correlation of the sections. The total thickness of uppermost Hettangian to lowermost Pliensbachian strata in sections on Kunga Island is estimated at 385 m. A comparison of selected zones in different sections shows a subtle thickness increase to the south. The contact of the Sandilands Formation and the overlying Ghost Creek Formation is diachronous, younging gradually to the south. The faunal succession in the Queen Charlotte Islands agrees well with that of the Taseko Lakes area and Nevada, promising regional applicability of the proposed zones. Intercontinental correlation with the northwest European standard zonation is possible at diffrent levels. The Hettangian/Sinemurian boundary is contained within the Canadensis Zone. It is best approximated by the first appearance of Badouxia columbiae and Metophioceras spp. The position of the Recognitum Zone at the Sinemurian/Pliensbachian boundary remains problematic; most evidence on hand points to its Pliensbachian affinities. The ammonite fauna consists of taxa with pandemic, Tethyan, Athabascan, East Pacific, and Pacific distribution. Provincialism was not prominent but existed during the Sinemurian time. The high proportion of Tethyan forms is in accord with the theory suggesting a more southerly original paleolatitude for Wrangellia. The distribution of Tethyan forms can be explained by the early opening of the Hispanic Corridor, proven to be in existence by the Pliensbachian. Alternatively, the pantropic distribution model cannot be ruled out, although the faunal record from the eastern Tethys is inadequate to prove it. Thestrong representation of Athabascan and East Pacific elements renders long-distance longitudinal tectonic dislocation of Wrangellia unlikely. The paleoecology and taphonomy of ammonites, associated macrofauna, and trace fossils is used for paleoenvironmental reconstruction. The general lack of bioturbation, predominance of thin-shelled, presumably pseudo-planktonic bivalves, and the intact preservation of fish and a crinoid specimen indicate prevailing oxygen deficient bottom conditions. Trace fossils provide evidence for periodic improvements of bottom oxygenation. Different modes of ammonite preservation are controlled by shell morphology as well as the varying sedimentation rate and diagenetic regime. The latter reflects changes in redox conditions in the upper sediment layers. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Radiolarian biostratigraphy is used to construct an informal zonation for sediments of upper Pliensbachian to lower Bajocian age from the Maude and Yakoun Formations, Queen Charlotte Islands, B.C. Paleoenvironmental studies assess depositional environment and the effects of changing facies relationships on the fauna. Seven distinctive assemblages are recognized comprising 167 species of spumellarian and nassellarian Radiolaria. The first well established middle Toarcian radiolarian assemblages are documented and both these and upper Toarcian assemblages are highly diverse and contain many new and unusual forms. Five genera and 89 new species are described many of which have restricted biostratigraphic ranges. A chlorophyte algal cyst appearing in all lowest Bajocian samples may, with further study, prove to be a significant marker for the lower Bajocian in the Queen Charlotte Islands. Although Toarcian Radiolaria have been little studied, the assemblages compare with others from North America, the Mediterranean and Japan, and are distinctly Tethyan in aspect. This is consistent with the position of Wrangellia, which paleomagnetic and ammonite biogeographic evidence indicates was in the northern hemisphere within 30° of the equator during the Early to Middle Jurassic. Studies of the abundance of spumellarians vs. nassellarians indicate thatnassellarians predominate, are abundant and diverse in deeper-water deposits (middle Toarcian and lower Bajocian shales) whereas spume Marians, particularly those with multi-layered or spongy tests, dominate in shallow-water deposits (upper middle Toarcian to Aalenian sandstones). Shallow-water nassellarians are much less diverse but a few species (all multicyrtids with thickened tests) are very abundant. Depth appears to be the major factor controlling radiolarian distribution patterns in this relatively shallow-water setting. Studies of eustatic sea-level changes throughout the Jurassic have indicated that major phases of sea-level rise occurred in the early to mid Toarcian and in the early Bajocian with a major phase of sea-level lowering in the late Toarcian to Aalenian; detailed study of the radiolarian faunal succession in the Queen Charlotte Islands appears to confirm this major worldwide trend. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

Graduation date: 1997

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1982. / "November 1981." Vita. / Includes bibliographical references. / Radiolarians which settle through the oceanic water column were recovered from three stations (western Tropical Atlantic-Station E, central Tropical Pacific-P1 and Panama Basin-PB) using PARFLUX sediment traps in moored arrays at several depths. The taxonomic diversities of the radiolarian assemblages in the sediment traps were very high. A total of 420 taxa, including 23 newly identified taxa, were found at the three stations; of these, 208 taxa were found at station E. The polycystine radiolarians generally reach the sea floor with little change in abundance or species composition, although slight skeletal dissolution occurs throughout their descent. The phaeodarian radiolarians, on the other hand, are largely dissolved within the water column; only a few species reach the sea-floor and these dissolve rapidly at the sediment-water interface. Most radiolarian skeletons sink as individuals through deep water columns without being incorporated into large biogenic aggregates. Because significant numbers of nassellarian and phaeodarian species are deep-water dwelling forms the diversity index of radiolarians increases with increasing depth in the mesopelagic zone. The vertical flux of the total radiolarians arriving at the trap depths (in x 103 individuals/m2/day) ranged from 16-24 (E), 0.6-17 (Pl), and 29-53 (PB). Of these on the average 25 % and 69 % of the total radiolarian flux is transported by Spumellaria and Nassellaria, respectively, while 5 % is carried by Phaeodaria. The measured SiO2 content of the skeletons averaged 91, 98 and 71 % of measured weight for Spumellaria, Nassellaria and Phaeodaria, respectively. The supply of radiolarian silica (mg SiO 2 /m 2/day) to each trap depth ranged from 2.5-4.0 (E), 0.9-3.2 (P ), and 5.7-10.4 (PB). The Radiolaria appear to be a significantly large portion of the SiO2 flux in >63 pm size fraction and thus play an important role in the silica cycle. When the radiolarian fluxes at the three Stations are compared with Holocene radiolarian accumulation rates in the same areas it became apparent that several percent or less of the fluxes are preserved in the sediments in all cases and the rest is dissolved on the sea-floor. Estimated excess Si which is derived from SiO2 dissolution on the sea-floor is fairly small relative to advective Si in the western North Atlantic and thus it appears to be insignificant to show any deviation in a simple mixing curve of deep water masses. Weight, length, width, projected area and volume of 58 radiolarian taxa were measured. The density contrast of radiolarians, relative to seawater, generally falls between 0.01 and 0.5 g/cm33. The sinking speed of 55 radiolarian taxa, measured in the laboratory at 3*C, ranged from 13 to 416 m/day. Despite the wide variety of morphology between the species, sinking speeds were best correlated with weight/shell among all the possible combinations of the examined variables. The estimated residence times of these taxa in the 5 km pelagic water column ranged from 2 weeks to 14 months. Large phaeodarians reached the water-sediment interface relatively quickly and ultimately dissolved on the sea floor. Small-sized taxa dissolved en route during sinking. The standing stock of 26 examined abundant taxa is on the order of 1 to 100 shells/m3 . Total radiolarian standing stock ranges from about 450 shells/m3 at Stations P1 and E to 1200 shells/m 3 at Station PB. The rate of production of total Radiolaria is calculated to be 77 to 225 shells/m 3 /day. The turnover time for these species ranges from several days to one month depending on the species and the assumption of the depth interval used for the estimation. / by Kozo Takahashi. / Ph.D.