PT  - JOURNAL ARTICLE
AU  - DAGLEY, P.
AU  - MUSSETT, A. E.
AU  - SKELHORN, R. R.
TI  - Polarity, stratigraphy and duration of the Tertiary igneous activity of Mull, Scotland
AID  - 10.1144/gsjgs.144.6.0985
DP  - 1987 Nov 01
TA  - Journal of the Geological Society
PG  - 985--996
VI  - 144
IP  - 6
4099  - http://jgs.lyellcollection.org/content/144/6/985.short
4100  - http://jgs.lyellcollection.org/content/144/6/985.full
SO  - Journal of the Geological Society1987 Nov 01; 144
AB  - Previous work left unresolved whether the Tertiary igneous activity had spanned a magnetic polarity succession R-N-R-N-R or, if overprinting had occurred, only R-N-R. New work is reported that demonstrates that thermal overprinting has occurred in a narrow zone, c. 600 m wide, bordering the outermost major intrusions of Centre 2. Criteria for the recognition of overprinting are examined.The polarity sequence is now believed to be R-N-R. In conjunction with radiometric dates which show that activity occurred from c. 60 Ma to c. 57 Ma, our data show that the sequence corresponds to chrons 26r-26-25r of the polarity time-scale of Harland et al. 1982 or 25r, 25 and 24r of Breggren et al. 1985. Upper and lower limits to the duration of the activity are, respectively, 4.67 Ma and 0.67 Ma, or 4.07 Ma and 0.60 Ma: a duration of about 3.5 Ma is thought probable.The magnetic evidence supports the view that the Loch Scridain sills correspond to the Early Acid and Intermediate Cone Sheets of Centre 1.