Coated grains have always attracted attention, at first of naturalists, and later of geologists, and the interest in these peculiar bodies was re lated both to their intriguing form and their significance in facies inter pretation and sedimentology and to their relevance to accumulations of hydrocarbons and other mineral deposits. This resulted in numerous publications on this subject, and the intention of this volume is to sum marize the present state of knowledge on coated grains. The idea of the book was to unite some general papers with papers reporting case studies of both recent and ancient coated grains. The organization of the book follows this intention. The papers presented in this volume have been invited by the editor; the theme of the book merits a few words of personal history. The development of studies of coated grains during the last two decades has not only resulted in a great increase in knowledge of recent and ancient environments of coated grain formation, but also numerous important and controversial questions of classification, environmental significance, mineralogical composition etc. of ancient coated grains have arisen. To answer these questions, in 1978 I started the study of many ancient and recent occurrences of coated grains at the Institut fUr Geologie, Ruhr-UniversiUH Bochum, following the invitation of Hans Fiichtbauer and sponsored by the Alexander von Humboldt-Stiftung.

I Approaches

I.1 Classification of Coated Grains
I.2 Classification of Coated Grains: Discussion
I.3 Origin of Coated Grains: Trace Element Constraints
I.4 Carbon and Oxygen Isotope Composition of Recent and Ancient Coated Grains
I.5 Neritic Macroid Genesis, an Ecological Approach
I.6 Accretionary Lapilli in Volcanic Ash Falls: Physical Factors Governing Their Formation
II Ooids
II.1 Calcareous Ooids: A Synopsis
II.2 Ferriferous Ooids
II.3 Cortical Fabrics in Calcite and Aragonite Ooids
II.4 Relict Sand Bodies and Bedforms of the Northern Bahamas: Evidence of Extensive Early Holocene Sand Transport
II.5 The Joulters Ooid Shoal, Great Bahama Bank
II.6 Holocene Lacustrine Ooids from Pyramid Lake, Nevada
II.7 Subrecent High-Sr Aragonitic Ooids from Hot Springs Near Tekke Ilica (Turkey)
II.8 Coated Grains Along the Dead Sea Shore
II.9 Structural and Geochemical Features of Jurassic Oolitic Limestones in the Veneto Region (NE Italy)
II.10 Sedimentary Characteristics of Oolitic Carbonates from the Jialing-Jiang Formation [Lower Triassic (T12J1)], South Sichuan Basin, China
II.11 Ooid Zonation as Indication for Environmental Conditions in a Givetian-Frasnian Carbonate Shelf-Slope Transition
II.12 Ooids and Oolites of the Proterophytic Boomplaas Formation, Transvaal Supergroup, Griqualand West, South Africa
III Rhodoids
III.1 Description and Classification of Rhodoliths (Rhodoids, Rhodolites)
III.2 The Occurrence and Ecology of Recent Rhodoliths - A Review
III.3 Rhodoids in Temperate Carbonates from the Cenozoic of New Zealand
III.4 Early Permian Coated Grains from a Lagoonal Environment, Laborcita Formation, Sacramento Mountains, Southcentral New Mexico, U.S.A.
IV Oncoids
IV.1 Oncoids: Comment to Recent Developments
IV.2 Cyanoliths (Cyanoids): Oncoids Formed by Calcified Cyanophytes
IV.3 Algal Micro-Reefs - Coated Grains from Freshwater Environments
IV.4 Brackish-Water Oncoids Composed of Blue-Green and Red Algae from a Pleistocene Terrace Near Corinth, Greece
IV.5 Environmental Significance of Freshwater Oncoids, Eocene Guarga Formation, Southern Pyrenees, Spain
IV.6 Depositional Environment, Diagenesis and Reservoir Properties of Oncolitic Packstones, Macaé Formation (Albian-Cenomanian), Campos Basin, Offshore Rio de Janeiro, Brazil
IV.7 Albian Pelagic Phosphate-Rich Macrooncoids from the Tatra Mts (Poland)
IV.8 Oncoids and Stromatolites in the Rosso Ammonitico Sequences (Middle-Upper Jurassic) of the Venetian Alps, Italy
IV.9 Pelagic Oncoids and Ooids in the Middle-Upper Jurassic of Eastern Sardinia
IV.10 Depositional Environments of Some Upper Jurassic Oncoids
IV.11 Carnian Oncolites of the Northern Calcareous Alps and the Drau Range (Austria)
IV.12 Girvanella Oncoids From Middle to Upper Triassic Allochthonous Boulders of the Dolomite Alps, Northern Italy
IV.13 Triassic Oncoids from Central Balkanides (Bulgaria)
IV.14 The Genesis of Algal Nodule Limestones from the Upper Carboniferous (San Emiliano Formation) of N.W. Spain
IV.15 Morphogenesis of Oncoids in the Lower Carboniferous Llanelly Formation of South Wales
V Vadoids
V.1 Vadoids
V.2 Recent Travertine Pisoliths (Pisoids) from Southeastern Idaho, U.S.A.
V.3 Pisoids in the Caliche Profiles of Tarragona (N.E. Spain)
V.4 Pisoliths (Pisoids) in Quaternary Travertines of Tivoli, Italy
V.5 Quaternary Pisoids of Lau, Fiji
V.6 Pisoids and Pisolite Facies (Permian), Guadalupe Mountains, New Mexico and West Texas
V.7 Vadose Pisolites of the Tongying Formation (Upper Sinian System) in Southwest China
V.8 A Proterozoic Calcrete in the Amos Formation, McArthur Group, Northern Territory, Australia
VI Contrasted Occurrences
VI.1 Coated Grains from the Great Barrier Reef
VI.2 Coated Grains Fades in the Lower Cretaceous of the Outer Dinarides (Yugoslavia)
VI.3 Coated Grains in Contrasted Environmental Situations: Norian and Lower Liassic of Northern Apennines
VI.4 Coated Grains fro