Donna Meyerhoff Hull

Turbidites from giant Hawaiian landslides: Results from Ocean Drilling Program Site 842

Pliocene to Pleistocene volcanic sand turbidites recovered 320 km west of the island of Hawaii at Ocean Drilling Program Site 842 contain fragments off fresh, weakly vesicular glass and tests of Pleistocene and Eocene radiolarians. This sand is probably related to turbidity currents generated from debris avalanches produced by giant landslides on the flanks of the Hawaiian Islands. On their way to Site 842, the currents flowed over the ∼m-bigh Ha-waiian Arch, indicating that the turbidity currents were at least 325 m thick. Similar sand has been reported 930 km south of the islands. Thus, Hawaiian giant landslides play a significant role in central Pacific deep-sea sedimentary processes.

Surge Tectonics: A New Hypothesis of Global Geodynamics

Preface. 1: Why a New Hypothesis? 1. Introduction. 2. Former and Current Concepts of Earth Dynamics. 3. Conclusion. 2: Unraveling Earth History: Tectonic Data Sets. 1. Data Availability. 2. New Data Acquisition. 3. Data Sets Unexplained in Current Tectonic Models: Foundation for a New Hypothesis. 4. Conclusion. 3: Surge Tectonics. 1. Introduction. 2. Velocity Structure of the Earths Outer Shells. 3. Contraction. 4. Contraction as an Explanation of Earth Dynamics. 5. Review of Surge and Related Concepts in Earth-Dynamic Theory. 6. Geotectonic Cycle of Surge Tectonics. 7. Pascals Law - the Core of Tectogenesis. 8. Evidence for the Existence of Surge Channels. 9. Geometry of Surge Channels. 10. Demonstration of Tangential Flow in Surge Channels. 11. Mechanisms for Eastward Surge. 12. Classification of Surge Channels. 13. K Structures. 14. Criteria for the Identification of Surge Channels. 4: Examples of Surge Channels. 1. Ocean-Basin Surge Channels. 2. Surge Channels of Continental Margins. 3. Continental Surge Channels. 4. Surge Channels in Zones of Transtension-Transpression. 5: The Tectonic Evolution of Southeast Asia - A Regional Application of the Surge-Tectonics Hypothesis. 1. Surge Tectonic Framework. 2. Surge-Tectonic History. 6: Magma Floods, Flood Basalts, and Surge Tectonics. 1. Introduction. 2. Descriptions of Selected Continental Flood-Basalt Provinces. 3. The Useof Geochemistry in Identifying Flood Basalts. 4. Geochemical Comparisons among Basalts Erupted in Different Tectonic Settings. 5. Duration of Individual Basalt Floods. 6. Flood-Basalt Provinces and Frequency in Geologic Time. 7. Non-Basalt Flood Volcanism in Flood-Basalt Provinces. 8. Flood Basalts or Magma Floods? 9. Surge-Tectonics Origin of Magma Floods. 7: Conclusions. Appendix. Bibliography. Index.

Upper Paleocene-Lower Eocene Radiolarian Biostratigraphy of the San Francisco de Paula Section, Western Cuba: Regional and Global Comparisons

In response to a growing need to define the Paleocene/Eocene boundary and record the events which immediately preceded and followed it within a 5 my span, the San Francisco de Paula section of western Cuba was evaluated for its potential as a boundary stratotype. Radiolarians, reported in previous studies by Cuban geologists as a major component of the faunal assemblages in this section, have been recollected and reanalyzed to determine their stratigraphic utility for recognition of the Paleocene/Eocene boundary in Cuba. On the basis of this and other recent microfossil studies of the San Francisco de Paula section, it is now known that the Paleocene/Eocene boundary in this succession is within an unconformity. Its placement herein is based on the highest occurrence of the planktonic foraminifera Morozovella velascoensis (Fernandez-Rodrguez et al. 1999, this volume). Radiolarians are present throughout the San Francisco de Paula succession with the exception of a barren interval in the middle of the section and two thin barren intervals near the top and the base. The most diverse radiolarian assemblages are from the shaley mudstones, which contain poorly preserved radiolarians that range from abundant to very rare. Other lithologies contain sparse, poorly preserved assemblages that appear strongly affected by dissolution. Thirty-five lowest and highest occurrences are noted within the section; however, because of poor preservation, several of these datums are higher or lower than expected when compared with the known global ranges of these species. The radiolarians from this study of the San Francisco de Paula section can be assigned to the stratigraphic interval from the upper Paleocene Bekoma campechensis to the lower Eocene Buryella clinata Zones. Species typical of the B. campechensis Zone include Bekoma campechensis, B. demissa, Bekoma spp., Buryella pentadica, B. tetradica, B. foremanae and Lamptonium pennatum. Faunas of the Bekoma bidartensis Zone contain Buryella tetradica, Giraffospyris lata, Phormocyrtis turgida, Podocyrtis (Podocyrtis) papalis, Pterocodon tenellus, Theocorys phyzella, Theocotyle nigriniae, Theocotylissa alpha, T auctor and Thyrsocyrtis (Thyrsocyrtis) hirsuta. The radiolarian assemblage representing the lower part of the Buryella clinata Zone is similar to that of the Bekoma bidartensis Zone, and also includes the marker species Buryella clinata. Assignment of the upper part of the San Francisco de Paula section to the Buryella clinata Zone is tentative, because of poor preservation. In the San Francisco de Paula section, the precise location of the Paleocene/Eocene boundary cannot be determined on the basis of radiolarians. However, taken together, radiolarian and calcareous nannofossil evidence indicate that the Paleocene/Eocene boundary is within an unconformity between samples SFP-22 and SFP-21 at the highest local occurrence of Morozovella velascoensis, equivalent o the top of planktonic foraminiferal Zone P5. In addition to tabulating the stratigraphic ranges of radiolarian species in western Cuba, this study presents a preliminary correlation between the lower Paleogene standard radiolarian low latitude zonation and other zonal schemes presented for the Caribbean region and mid to high latitudes. Although the San Francisco de Paula section does possess some of the characteristics desirable in a stratotype for the Paleocene/Eocene boundary, its usefulness in terms of biostratigraphy is limited. INTRODUCTION Programme Project #308 was initiated to study Paleocene/EoThe Paleocene/Eocene boundary interval is an interesting pecene boundary sections worldwide, including potential sections riod in Earth history, characterized by warm high latitudes previously documented in western Cuba (e.g., Bronnimann and (Stott and Kennett 1990; Kennett and Stott 1991) and changes Rigassi 1963). in oceanic circulation associated with deep water production at low latitudes (Miller et al. 1987; Kennett and Stott 1991; In contrast to calcareous microfossil groups for which a considThomas 1990a, 1990b, 1993). Consequently, definition of the erable amount of lower Paleogene biostratigraphic information Paleocene/Eocene boundary takes on increasing significance as is available from land-based sequences in the Caribbean region it becomes necessary to place these climatic and as well as from Deep Sea Drilling Project (DSDP)/Ocean paleoceanographic events in their correct chronological succesDrilling Program (ODP) cores, most biostratigraphic informasion. To meet this need. International Geological Correlation tion on Cenozoic radiolarians in the Caribbean region is from micropaleontology, volume 45, supplement 2, pp. 57-82, text-figures 1-3, plates 1-2, table 1, 1999 57 A. Sanfilippo and D.M. Hull: Upper Paleocene Lower Eocene radiolarian biostratigraphy of the San Francisco de Paula Section, western Cuba deep-sea drilling cores alone. Radiolarians from Cretaceous and lower Paleogene formations in western Cuba have been reported by Flores Albin (1983) and Flores Albin and Femaindez-Rodriguez (1985), and a small amount of additional information on Cenozoic radiolarians from Cuba, Barbados and Trinidad is summarized in Riedel and Sanfilippo (1971), and Sanfilippo and Riedel (1976). Maurrasse (1973, 1976, 1979) reported mainly on the paleoecologic and paleobiogeographic implications of radiolarian facies in Caribbean mid-Paleogene deep-sea sediments. DSDP Leg 4 collected useful Caribbean middle Eocene sequences with radiolarians at Site 29 (Riedel and Sanfilippo 1970). Leg 10 in the Gulf of Mexico sampled a similar sequence (Foreman 1973; Sanfilippo and Riedel 1973) and Leg 15 provided Caribbean equivalents of the sediment sequences in the Gulf of Mexico (Riedel and Sanfilippo 1973) which permitted correlation with calcareous microfossils. Subsequent DSDP/ODP Legs (76-78, 96, 100-102 and 110) in the Caribbean region recovered only younger than middle Eocene radiolarian-bearing sediments. Although more numerous Paleocene and lower Eocene samples have been obtained from different parts of the world ocean, the recovery is still intermittent and radiolarian preservation commonly not adequate for detailed biostratigraphic work (Sanfilippo and Nigrini 1998a). For these reasons it was anticipated that the discovery of a new land-based locality, south of the village of San Francisco de Paula in western Cuba (text-figure 1), would contain a suitable Paleocene/Eocene boundary section that would resolve at least some of the stratigraphic problems around the boundary and at the same time allow correlation between the calcareous and siliceous microfossil groups with the results from paleomagnetic and isotope investigations (M.-P. Aubry, person. communs., 1996, 1997; Femaindez-Rodriguez t al. 1999, this volume). LOCATION AND LITHOSTRATIGRAPHY The San Francisco de Paula section is located in western Cuba near the city of Habana (text-figure 1). It is 56m thick and consists of the Apolo Formation (Paleocene and lowermost Eocene) and the lower part of the overlying Capdevila Formation (also known locally as the Alcava Formation; lower Eocene, for further explanation see FemaJndez-Rodriguez et al. 1999, this volume). The lower 40m of the section (text-figure 2), which includes the Paleocene/Eocene boundary interval, is composed of marly mudstones and soft shales which are weathered and, in places, largely covered by vegetation. The base of the section is more massively bedded with coarser-grained rocks and conglomeratic limestones. Forty-three meters above the base of the San Francisco de Paula section, the rock sequence is marked by a distinctive lithologic boundary. The rocks above this boundary are much coarser-grained and are well indurated with distinctive graded bedding, suggesting storm or turbidite deposition. White marly clasts appear in linear bands just above the lithologic boundary. Fossils present in the San Francisco de Paula succession include planktonic and benthic foraminifera, large foraminifera, radiolarians, calcareous nannofossils, ostracodes, bryozoans, calcareous algae and mollusk fragments (Flores Albin and Fernandez-Rodriguez 1985; Fernmandez-Rodrfguez et al. 1999, this volume). Unfortunately, all fossil groups show varying degrees of preservation, and none occur continuously throughout the sequence. Fernmandez-Rodrfguez et al. (1999, this volume), in their analysis of the planktonic foraminifera, suggest the presence of four unconformities in the sequence. Recognition of these unconformities is based in part on abrupt changes in abundance, diversity, and preservation of the foraminiferal faunas. They relate these unconformities to the 58 to 54 Ma time span of active local tectonics which has been noted by other authors (Bralower and Ituralde-Vinent 1997; Lewis and Draper 1990). METHODS AND MATERIALS Initial discovery and collection of material from the San Francisco de Paula section was made by E. Flores Albin, G. Femrnandez-Rodriguez and other Cuban colleagues shortly after this section was cut along a new road. Consequently, the original samples are relatively unweathered. The Cuban geologists measured the section, collected samples, described lithofacies, and analyzed the material principally for foraminifera and radiolarians (Flores Albin, Appendix 1; Femrnandez-Rodriguez et al. 1999, this volume). In 1993, a group of scientists from the U.S., including A. Sanfilippo and D. Hull, joined the Cuban geologists to revisit the San Francisco de Paula section as well as other potential Paleocene/Eocene boundary sections in western Cuba on behalf of IGCP Project #308. The section was re-measured, described, and 54 samples were collected for studies of planktonic and benthonic foraminifera, radiolarians, and calcareous nannofossils; portions of these same samples were also set aside for carbon/oxygen isotope determinations. The selection of procedures used to measure and sample the section during the 199

The upper Paleocene-lower Eocene San Francisco de Paula section: Biostratigraphic synthesis

The San Francisco de Paula section is one of the few that permit direct correlations between siliceous and calcareous microfossil zonal schemes near the Paleocene/Eocene boundary. We discuss these correlations, delineate unconformities in the section and discuss the location of the Paleocene/Eocene boundary.

Magma Floods, Flood Basalts, and Surge Tectonics

Tyrrell (1937) brought into the literature the term “flood basalts,” to give substance to a concept that he felt would improve the understanding of the effusion and flow of basaltic lavas. Tyrell was dissatisfied with the term “plateau basalt,” which had been current for more than a half century because it “… merely refers to an accidental and inessential feature resulting from levelling-up, erosion or Eaith movement.” Tyrrell was aware, however, that his predecessor by more than a half century, Sir Archibald Geikie, understood fully the dynamics and the framework of “plateau basalt” (Geikie, 1887), for he noted: “Sir A. Geikie actually mentions the word ‘flooded’ …” However, Tyrrell then commented “…I hold that ‘flood basalt’ is a much more fitting designation for this colossal type of basalt accumulation….”

Examples of Surge Channels

In this chapter, we present actual examples of the major types of surge channels, following the outline of Table 3.2 and Figure 3.39. We also discuss the criteria for recognizing the different types of surge channels, listed on Table 3.3.

The Tectonic Evolution of Southeast Asia—A Regional Application of the Surge-Tectonics Hypothesis

In this chapter, we give a surge-tectonic interpretation of the geological evolution of southeastern Asia. This part of the book should be treated as interpretative and not as an attempt at a definitive statement on the tectonic history of southeastern Asia (Fig. 5.1). We also present a series of paleotectonic surge-channel maps to illustrate our interpretation. These maps (Figs. 5.2, 5.3, 5.6, 5.8–5.12 and 5.17–5.18) portray the major stable areas (massifs and platforms) and paleogeothermal phenomena (surge channels) of southeastern Asia from the beginning of Sinian time (850 Ma) through the present. Insofar as possible, we identified both former and still active surge channels on the basis of the criteria for the identification of surge channels that were listed in Chapter 3. The literature sources used for these maps are listed in the bibliography: an asterisk appears before each source used.

Unraveling Earth History: Tectonic Data Sets

In this chapter, we discuss types of data sets available for discerning Earth tectonics todays that we feel have not been adequately explained by current tectonic hypotheses.

Why a New Hypothesis

Before 1962, the year in which H.H. Hess revived and revised Arthur Holmes’s (1931) concept of seafloor spreading (which also was proposed by Ampferer [1941]), the geology and geophysics departments of the world taught several geodynamics hypotheses. These hypotheses stimulated lively discussions and resulted in the publication of a highly diversified spectrum of ideas. After Hess’s version of seafloor spreading was published, diversity in geodynamics thinking began to wane, and outside of Asia and Eastern Europe, had all but vanished by the end of 1963. Most of these earlier and now contrary concepts are no longer taught or are presented briefly as old, outdated ideas in light of the new hypothesis of plate tectonics. This fact should generate concern among all scientists, for historically the rigorous testing of ideas effectively ceases in intellectual environments dominated by a single concept. Furthermore, it is the belief of these authors that as intensive geotectonic research has vastly increased the database for Earth-dynamic studies, plate tectonics has not adequately and completely explained the geology of many regions of the world.