GLOSSARY – B

GLOSSARY – B

by: Charles O’Dale

BALDWIN’S CURVE

Baldwin’s curve relating crater depth to diameter, showing how well the Pingualuit, Holleford, Brent and Deep Bay meteorite craters all fit the curve (after C. S. Beals, M. J. S. Innes, and J. A. Rottenberg, The search for fossil meteorite craters–I, Current Science 29: 206).

BALLEN STRUCTURE
Microscopic shock-deformation feature in quartz. Oval quartz with rims of tiny vugs filled with amorphous material.

BALLISTIC EROSION AND SEDIMENTATION
(Oberbeck 1975) Emplacement of ballistically transported impact ejecta, and ejecta-surface interaction.

BASALT
A dark coloured igneous rock. commonly extrusive, composed primarily of calcic plagioclase and pyroxene; the fine-grained equivalent of gabbro.

BEDROCK
The solid rock that underlies gravel, soil, or other surficial material.

BIOTITE
See mica.

BOLIDE
Exploding fireball.
[see – METEORITE]

BRECCIA – from Italian indicating both loose gravel and stone made by cemented gravel
A clastic sedimentary rock composed of angular clasts in a consolidated matrix. Breccias can be produced in several geologic processes: tectonic breccia, volcanic breccia (eruption breccia, vent breccia), sedimentary breccia (e.g., rock fall breccia), collapse breccia (e.g., in karst areas). Breccias may be distinguished depending on the origin of the clasts, monomictic (monogenetic, monolithologic) and polymictic (polygenetic, polylithologic).

[see – BRECCIA]
[see – SHOCK METAMORPHISM]

BRECCIA DYKE
Dyke formed in the (par)autochthonous basement or in displaced megablocks of impact craters consisting of impact breccia (polymict breccias such as impact melt rock, suevite, lithic breccia or more rarely monomict breccia).

BUNTE BRECCIA
(Bunte Breccie or Bunte Brekzie or Bunte Bresche, Loc. Ries impact crater, Germany) Local term for polymict lithic breccia forming the continuous ejecta blanket at the Ries impact crater, Germany; first detailed description as “Kalkbreccie” by C. W. von Gümbel in 1870.