Volcanology of Saba and St. Eustatius, Northern Lesser Antilles

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    . ,   

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Volcanology of Saba and St. Eustatius, Northern Lesser Antilles

M. John Roobol and Alan L. Smith       , ,  

     

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Digital versions of the maps in this volume and other supporting materials are presented on the website of the Royal Netherlands Academy of Arts and Sciences, see www.knaw.nl/edita/antilles

Royal Netherlands Academy of Arts and Sciences P.O. Box ,  GC Amsterdam, the Netherlands T +--   F +--   E [email protected] www.knaw.nl  --- The paper in this publication meets the requirements of « iso-norm  () for permanence ©  Royal Netherlands Academy of Arts and Sciences No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher.

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Contents

List of Plates Abstract Acknowledgments

XI XII XVIII

 Island Arcs of the eastern Caribbean The composite arc of the Lesser Antilles 3 The Active Arc 3 The Extinct Arc of the Limestone Caribbees 5 The Aves Ridge 6 Venezuela and Grenada basins Submarine banks of the northern Lesser Antilles Anegada Passage 8 Kallinago Depression 9 Seismically active faults 9 Faults revealed by seismic reflection profiles 10 Lineaments 11 Drilling and seismic reflection studies on the Saba Bank 11 Mesozoic rocks of St. Croix and La Desirade islands 13 Mesozoic rocks dredged from submarine scarps on banks in the northeastern Caribbean 13 Discussion 14

1 2

7 7

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Contents

          Introduction Development of pyroclastic studies in the Lesser Antilles Classification of pyroclastic deposits of the Lesser Antilles Pelean-style eruptions 23 St. Vincent-style eruptions 25 Plinian-style eruptions 25 Asama-style eruptions 26 Phreatic- / phreatomagmatic-style eruptions 27 Volcaniclastic deposits lacking primary pyroclastic structures 28  Introduction Morphology and bathymmetry of Saba Geology of Saba The horseshoe-shaped crater / sector collapse structure of Saba 35 The older volcanic division of Saba 40 The younger volcanic division of Saba 43 Geochronology of Saba Pyroclastic stratigraphy of Saba Grain size characteristics 48 The most recent eruption of Saba Structural evolution of Saba     

17 17 20 22

31 31 31 34

44 47 51 57 59

Introduction 59 Petrography of the volcanic rocks and their inclusions 61 Basalt 62 Basaltic andesite 62 Andesite 65 Dacite 65 Partially resorbed bipyramidal quartz in the volcanic rocks of Saba 65

Contents

Hypabyssal inclusions 66 An inclusion of a hypabyssal lamprophyre 66 Exotic crustal inclusions 69 Geochemistry of Saba Introduction 72 Geochemistry of volcanic rocks from Saba 73 Geochemistry of inclusions 85 Mineralogy of inclusions 88 Isotopic compositions Petrogenesis . 

VII

72

90 92 99

Introduction 99 Morphology and bathymmetry of St. Eustatius 99 Geology of St. Eustatius 101 Geochronology of St. Eustatius 103 Geology of the Northern Centers 107 Submarine pyroclastic stratigraphy of the White Wall-Sugar 108 Loaf ridges 119 Pyroclastic stratigraphy of the Quill Introduction 119 Stratigraphic Division 1: Base Surge Division (