Impact Stratigraphy

by Montanari, Alessandro; Koeberl, Christian

• ISBN13: 9783540663683
• ISBN10: 3540663681
• Format: Paperback
• Copyright: 2000-05-01
• Publisher: Springer Verlag

Summary

This book provides a general introduction to impact stratigraphy, with emphasis on the recognition of distal impact ejecta in the field, by focusing on the impactoclastic layers of the Umbria-Marche sequence in Central Italy, with an almost perfect stratigraphic record over the last 200 Million years. A general introduction to impact cratering and a discussion of distal ejecta and impact layers around the world is followed by a detailed description of the record of the impact of extraterrestrial bodies in sediments of the Umbria-Marche Apennines. The volume is of interest to a diverse audience in the geological and planetary sciences, ranging from (upper) undergraduate to research level. This book can also be used by students and researchers as a field guide to some of the most important Italian impact layers.

Table of Contents

Introduction: Impact Cratering as a Geological Process	1	(56)
Historical Background	1	(6)
General Characteristics of Impact Craters	7	(3)
Recognition of Impact Structures	10	(4)
Formation of Impact Craters	14	(2)
Shock Waves and the Stages of Crater Formation	16	(5)
Shock Metamorphic Effects	21	(18)
General	21	(4)
Shater Cones	25	(2)
Mosaicism	27	(1)
Planar Microstructures	27	(6)
Bulk Optical and other Properties	33	(1)
Diaplectic Glass	34	(1)
High-Pressure Polymorphs	34	(2)
Mineral and Rock Melts	36	(3)
Classification of Impactites	39	(3)
Meteoritic Components in Impactities	42	(9)
Meteoritic Components and Siderophile Element Analyses	43	(4)
Problems with Meteoritic Component Identification	47	(2)
Osmium Isotopes in Impact Studies	49	(1)
Chromium Isotope Systematics	50	(1)
Dating of Impact Structures	51	(6)
Distal Ejecta and Tektites	57	(44)
Characteristics of Proximal and Distal Ejecta	57	(3)
Distal Ejecta as Stratigraphic Markers	60	(3)
Importance of the K/T boundary	63	(1)
Tektites and Microtektites	64	(29)
Geographical Distribution: Strewn Fields and Age	68	(1)
Definition and Classification of tektites	69	(2)
Petrology and Geochemistry of Tektites	71	(8)
Source Rocks of Tektites	79	(1)
Source Craters of Tektites	80	(1)
North American Strewn Field	80	(5)
Central European Strewn Field	85	(1)
Ivory Coast Strewn Field	86	(2)
Australasian Strewn Field	88	(1)
Tektite Formation: Facts and Open Questions	89	(4)
Other Impact Glasses: Relation to Source Craters	93	(8)
Libyan Desert Glass	95	(6)
Important distal Ejecta Layers and Their Source Craters	101	(56)
General	101	(1)
The K/T Boundary and Chicxulub	101	(29)
Evidence for Impact at the K/T boundary	104	(1)
PGE Enrichments	104	(1)
PGE Abundance Patterns; K/T boundary Meteorite?	105	(1)
Meeoritic Os- and Cr-isotopic Signature	106	(1)
Soot and Organic Chemistry	107	(2)
Evidence of shock metamorphism	109	(2)
Impact glass	111	(1)
Impact-derived diamonds	112	(1)
Occurrence of spinel	113	(1)
Chicxulub Impact Structure: Relation to the K/T Event	114	(9)
Chicxulub and the K/T Mass Extinction	123	(7)
Late Eocene Impact Layers	130	(6)
Chesapeake Bay	132	(1)
Popigai	133	(3)
Manson Impact Structure and Ejecta Layer	136	(2)
Acraman Impact Structure and Ejecta Layer	138	(1)
Morokweng and the Jurassic--Cretaceous Boundary	139	(3)
Other Confirmed and Possible Ejecta Layers	142	(10)
South African and Australian Archean Spherule Layers	142	(6)
Late Devonian Impact Layer and Alamo Breccia	148	(2)
Permian--Triassic Boundary	150	(1)
Triassic--Jurassic Boundary	151	(1)
Outlook	152	(5)
The Umbria--Marche Sequence	157	(10)
Tectonic Setting	157	(5)
Stratigraphic Framework of the U--M Carbonate Sequence	162	(5)
Triassic--Lower Cretaceous	162	(1)
Upper Cretaceous--Oligocene	163	(3)
Miocene	166	(1)
Impact Stratigraphy in the U--M Sequence	167	(112)
Searching for Impact Signatures in the Stratigraphic Record	167	(5)
The Tr/J Record	172	(1)
The Pliensbachian--Toarcian Boundary at Valdorbia	173	(4)
The J/K Record	177	(4)
The Upper Aptian Event	181	(3)
The Cenomanian--Turonian Boundary	184	(6)
The Terminal Cretaceous Record	190	(60)
The Maastrichtian	192	(5)
Defiition of the K/T Boundary in the U--M Basin	197	(4)
Sedimntary Setting and K/T Boundary ``facies''	201	(2)
Impact and Catastrophe Signatures in the U--M K/T Clay	203	(12)
High-resolution Impact Stratigraphy of the K/T Event	215	(7)
Representative K/T Boundary Outcrops in the U--M Basin	222	(28)
The Paleogene Impact Record	250	(24)
The Paleocene--Eocene Boundary	250	(4)
The Terminal Eocene Events	254	(4)
The Global Stratotype Section and Point for the E/O Boundary at Massignano	258	(4)
Impact signatures at Massignano	262	(6)
High-resolution Impact stratigraphy at Massignano	268	(6)
The U--M Miocene Record	274	(5)
Documentation and Laboratory Techniques	279	(22)
Documentaion and Sampling in he Field	279	(3)
Sample Preparation	282	(4)
Bulk Samples	282	(1)
Isolation of Grains and Inclusions	283	(3)
Laboratory Techniques	286	(15)
Standard Bulk and Microprobe Analysis Methods	286	(3)
Iridium Determinations	289	(2)
Platinum Group Element Determinations	291	(1)
Osmium Isotope Measurements	292	(3)
Methods for Shocked Quartz Measurements	295	(6)
References	301	(52)
Index	353