Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

Tectonic setting of basic volcanic rocks determined using trace element analyses

Assembly, configuration, and break-up history of Rodinia: A synthesis

Geochemical fingerprinting of oceanic basalts with applications to ophiolite classification and the search for Archean oceanic crust

[1] The Solonker suture records the termination of the central Asian Orogenic Belt (CAOB). However, tectonic development of the Solonker suture is poorly understood. We report new field data for the Ondor Sum melange in the Ulan valley, and present a new evaluation of the orogenic belt extending from the southern Mongolia cratonic boundary to the north China craton within the context of a new geological framework and tectonic model, which incorporates relevant data from the literature. The southern accretionary zone between the north China craton and the Solonker suture is characterized by the Mid-Ordovician-Early Silurian Ulan island arc-Ondor Sum subduction-accretion complex and the Bainaimiao arc. This zone was consolidated by the Carboniferous-Permian when it evolved into an Andean-type magmatic margin above a south dipping subduction zone. The northern accretionary zone north of the Solonker suture extends southward from a Devonian to Carboniferous active continental margin, through the Hegenshan ophiolite-arc accretionary complex to the Late Carboniferous Baolidao arc associated with some accreted Precambrian blocks. This northern zone had consolidated by the Permian when it developed into an Andean-type magmatic margin above a north dipping subduction zone. Final subduction of the central Asian ocean caused the two opposing active continental margins to collide, leading to formation of the Solonker suture in the end-Permian. Predominant northward subduction during final formation of the suture gave rise in the upper northern plate to a large-scale, postcollisional, south directed thrust and fold belt in the Triassic-Jurassic. In summary, the CAOB underwent three final stages of tectonic development: early Japanese-type accretion, Andean-type magmatism, and Himalayan-type collision.

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Accretion leading to collision and the Permian Solonker suture, Inner Mongolia, China: Termination of the central Asian orogenic belt

A hypothesis for a late Precambrian fit of western North America with the Australia-Antarctic shield region permits the extension of many features through Antarctica and into other parts of Gondwana. Specifically, the Grenville orogen may extend around the coast of East Antarctica into India and Australia. The Wopmay orogen of northwest Canada may extend through eastern Australia into Antarctica and thence beneath the ice to connect with the Yavapai-Mazatzal orogens of the southwestern United States. The ophiolitic belt of the latter may extend into East Antarctica. Counterparts of the Precambrian-Paleozoic sedimentary rocks along the U.S. Cordilleran miogeocline may be present in the Transantarctic Mountains. Orogenic belt boundaries provide useful piercing points for Precambrian continental reconstructions. The model implies that Gondwana and Laurentia rifted away from each other on one margin and collided some 300 m.y. later on their opposite margins to form the Appalachians.

Southwest U.S.-East Antarctic (SWEAT) connection: A hypothesis

Many Alpine ophiolite complexes characteristically display a pseudostratiform sequence of ultramafics, gabbro, diabase, pillow lava and deep-sea sediments. These masses resemble the known rock suite from the ocean floor. They are either fragments of old oceanic crust and mantle caught up in deformed belts, or results of diapiric emplacement of partly molten mantle material on or near the sea bottom. Such complexes are widespread in the Tethyan mountain system and have been recognized also from the circumPacific region. The Troodos Massif, Cyprus, consists of a pseudostratiform mass of harzburgite, dunite, pyroxenite, gabbro, quartz diorite, diabase and pillow lava arranged in a dome-like manner. The diabase forms a remarkable dyke swarm, trending mostly north-south in which 100 km of extension is indicated over 100 km of exposure. Such a feature suggests formation by sea-floor spreading. Layering of pyroxenite, harzburgite and dunite generally is perpendicular to subhorizontal rock unit contacts. The harzburgite and dunite are tectonites and probably represent uppermost mantle. Pyroxenite, gabbro, quartz diorite and diabase may represent the products of partial fusion of mantle material or of fractional crystallization of such partial fusion products. Chemical compositions of mafic intrusive and extrusive rocks do not fit well with oceanic tholeiite compositions, but resemble greenstones and associated rocks recently reported from the oceans. The massif probably formed about an old Tethyan ridge. Some pillow lavas may be crust added after the main spreading episode. A fault zone active during emplacement of the lower units of the complex may represent a fossil transform fault. Complex chilled margins in the dyke swarms and mutually contradictory cross-cutting relations between dykes and plutonic mafic rock suggest formation of ocean crust by multiple intrusion of small portions of liquid. Uneven top surface of the dyke swarm and some conjugate dyke systems suggest independently varying rates of magma supply and extension. Other Tethyan ophiolites, particularly in Greece and Italy, exhibit internal structure parallel to, rather than perpendicular to, major rock units, and some show much less diversity in mafic rock type. If these masses are fragments of ocean floor and mantle, such differences in internal structure may be due to differences in spreading processes—perhaps differences in spreading rate.

The Troodos Massif, Cyprus and other Ophiolites as Oceanic Crust: Evaluation and Implications

Ever since their recognition, ophiolites have been a source of controversy, although all workers have agreed upon their importance. A number of conflicting schools of thought have become unified in the interpretation of ophiolite complexes as fragments of oceanic crust and mantle formed at spreading centers. An expanded version of the Penrose ophiolite definition is proposed, herein called the ophiolite association, taking into account rocks which bear upon the origin and significance of ophiolite complexes. An ideal ophiolite association includes the following units from bottom to top: (1) a crystalline basement and shallow water sedimentary sequence, (2) a tectonic unit of thrust slices of continental margin and rise and abyssal sediments and/or melange, (3) a metamorphic unit, as much as a few hundred meters thick, generally with higher-grade rocks over lower-grade ones, (4) ultramafic tectonite unit composed dominantly of multiply deformed peridotite, dunite, and minor chromitite, (5) a cumulate complex, ultramafic at the base grading to mafic or intermediate at the top, (6) a noncumulus unit of varitextured gabbro and minor trondhjemite (7) a sheeted dike complex, (8) an extrusive section of massive and pillowed flows and intercalated sediments, (9) an abyssal or bathyal sediment sequence which may include radiolarian chert, red pelagic limestone, metalliferous sediments, breccias, and/or pyroclastic deposits, and (10) postemplacement deposits of laterite, reef limestone, or shallow marine or subaerial sediments. This expanded ophiolite association allows greater precision in inferring original origin and emplacement. Some ophiolite complexes, particularly in the Tethys (herein designated Tethyan type), exhibit units 1, 2, 3, and 4, whereas others, particularly in the Cordilleran belt (herein termed Cordilleran type), lack units 1, 2, 3, and, in places, 4. The emplacement of the former probably occurred during collision of a passive margin with a subduction zone or incipient subduction zone. Emplacement of the Cordilleran type generally is not clear-cut. The nature of the spreading center which produced a given ophiolite is indicated more clearly by the presence or absence of units 5–9 than by chemistry or mineralogy. Some ophiolite complexes lack complete sections and may have formed along transform faults. Others contain volcanic pyroclastic deposits instead of pelagic sedimentary sequence and probably formed within or near an arc. Several ophiolite complexes may have originated by conversion of a transform fault into a subduction zone. Such conversion may result from normal plate evolution or from major plate reorganization. Major times of ophiolite emplacements appear to correspond with global plate reorganizations.

origin and emplacement of ophiolites

A GROWING body of evidence and theory supports the idea that processes of plate tectonics have been operating for the past 3 × 109 years1. The hypothesis of ocean-driven plates implies that certain mountain systems represent the remains of former large ocean basins. An important corollary of this notion is that the history of continental assembly and fragmentation can be inferred from the geological record of the various mountain systems. We show here how the diversity of marine fauna and fluctuations in sea level can be related to patterns of continental fragmentation and reassembly. It seems that changes in the diversity of fauna predicted from these patterns can account for a great deal of the variation in the diversification and extinction of marine biota that has long puzzled palaeontologists. The timing of major transgressions and regressions predicted from these patterns also agrees well with the observed record.

Plate-tectonic Regulation of Faunal Diversity and Sea Level: a Model

Every few years the people who work on ophiolites and the people who work on oceanic crust decide that it is time to get together and compare notes. The ophiolite people are primarily but not exclusively traditional “land” geologists who combine geologic mapping with structural, petrologic, and geochemical studies; the ocean crust people are primarily (but not exclusively) marine geologists and geophysicists who drill and dive on the real thing. There is some overlap of people who do both, but since most do either one or the other, these get-togethers are a critical reality check for everyone. GSA Special Paper 349 “Ophiolites and Oceanic Crust: New Insights from Field Studies and the Ocean Drilling Program,” presents results from a Penrose Conference on this topic convened by the editors in 1999 in northern California. In Penrose tradition, the meeting combined keynote speakers, short oral presentations, and poster sessions with extended discussion sessions, moderated and summarized, on the full gamut of topics central to this comparison. The Special Paper presents a good representation of the topics and areas that were central to these discussions, and in many ways captures the true spirit of that meeting. There are 39 chapters organized into six sections. The first section, Ophiolites, ocean crust, and global tectonics, looks at the big picture with several papers that reinforce the paradigm of ophiolites as onland oceanic crust formed at mid-oceanic spreading centers. This conclusion is argued most forcefully in the lead paper by Moores et al., who suggest a model in which the chemical signature of an ophiolite is contingent on the prior history of the asthenosphere it was derived from, and in the paper by Sturm et al., who show that arc-like geochemical signatures can leak into subducting crust along slab windows. Rampone and Piccardo show that, in the Apennines, basalts and peridotites represent distinct mantle reservoirs of different ages that formed during the rifting of continental crust, while Fryer et al. examine the significance of serpentine mud-volcanoes in the Mariana forearc, a classic area that may represent our best analogue for where most ophiolites form. Subsequent sections include Oceanic lower crust and upper mantle; Structure and physical properties of upper oceanic crust; Hydrothermal processes; Pacific rim ophiolites; and Ophiolites of the Iapetus, Rheic-Pleionic, Neotethyan, and Indian oceans. The first three of these sections focus on processes of ocean crust formation and evolution, based on detailed studies of oceanic crust, ophiolites, or both. There are several review papers that summarize current knowledge—my favorites are those that look at hydrothermal processes (papers by Humphris and Tivey, Kelly and Früh-Green, Manning et al., Alt and Teagle, and Gillis and Bannerjee), largely because that is an area where much has been learned over the last decade. There is also an excellent review of the Hole 735B gabbros by Robinson et al., which represents our best view to date of in situ lower oceanic crust. Bedard et al. review their concept of the lower oceanic crust as a reactive filter, driven by the process of syntexis (assimilation and reaction of new primitive magmas with previously intruded cumulates). The last two sections contain a range of papers that describe new ophiolites in exotic locales (e.g., Iran, the Urals, Timor), present new data on some old ophiolite friends (e.g., Bay of Islands, western Greece, Maquarie Island), or present new views of ophiolites whose origin and significance have been debated for years (e.g., Oman, Caledonides, and five papers on ophiolites in California). Space prohibits a complete discussion of all the papers included in these sections, but all present the latest (and in some cases, only) data on their respective locales. Should you buy this book? If you work on ophiolites or oceanic crust, you probably already have (I bought mine long before being asked to do this review). If you work in peripheral areas and need to know what’s going on in oceanic crust or ophiolites these days, you will also want to read it. Some of the individual papers are also a great resource for students who are interested in more limited aspects covered here, such as magmatic or hydrothermal processes. I do not agree with the conclusions of some of the papers, and readers who are unfamiliar with the gang warfare of ophiolite studies need to be aware that many people who think that ophiolites make good analogues for ocean crust also conclude that most ophiolites do not represent oceanic crust formed at mid-ocean ridge spreading centers. This consensus is not immediately apparent, and readers should be aware that significant controversy still exists and is not resolved here. . . but this did not stop me from buying my copy early.

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Eldridge M. Moores

Papers

Southwest U.S.-East Antarctic (SWEAT) connection: A hypothesis

The Troodos Massif, Cyprus and other Ophiolites as Oceanic Crust: Evaluation and Implications

origin and emplacement of ophiolites

Plate-tectonic Regulation of Faunal Diversity and Sea Level: a Model

Ophiolites and Oceanic Crust: New Insights from Field Studies and the Ocean Drilling Program