Journal des dames et des modes

1820/06/15 (N33,A24).

Journal des dames et des modes

1822/12/20 (N70,A26).

Journal des dames et des modes

1822/03/15 (N15,A26).

Journal des dames et des modes

1822/08/25 (N47,A26).

Journal des dames et des modes

1819/12/20 (N70,A23).

Journal des dames et des modes

1822/05/31 (N30,A26).

Journal des dames et des modes

1821/09/20 (N52,A25).

Journal des dames et des modes

1819/12/15 (N69,A23).

Journal des dames et des modes

1821/02/28 (N12,A25).

Journal des dames et des modes

1819/05/20 (N28,A23).

Journal des dames et des modes

1821/09/15 (N51,A25).

1st datings of ammonite-bearing Bajocian suites from Caucasus (Georgia) - K-Ar ages of volcanic hornblendes

Volcanic flows and tuffs interbedded with ammonite-bearing sediments directly correlatable with the stratotype section of the Bajocian stage have been dated for the first time within the Caucasus area. Three samples, each from a different section, allowed separation of well-preserved brown hornblende; these are considered reliable geochronometers in a region where subsequent volcanic activity occurred. The dated separates are V139: a volcanic layer probably near the base, V142 another layer near the top of the Lower Bajocian substage; V141 a boulder from a latest Bajocian volcanic conglomerate. From bottom to top, apparent ages at 173.5 +/- 2.6, 164.8 +/- 2.5 and 167.1 +/- 1.9 Ma (analytical uncertainty, 95% confidence level) respectively, can be calculated. The consistency of the results is obtained if the dated boulder is interpreted as derived from an underlying layer, The Bajocian-Bathonian boundary is much younger than commonly accepted and younger than 164 Ma.

Journal des dames et des modes

1820/06/10 (N32,A24).

Journal des dames et des modes

1821/11/30 (N66,A25).

Journal des dames et des modes

1821/02/25 (N11,A25).