چينه نگاري سكانسي واحدهاي شيلي و كوارتزيت بالايي سازند لالون در ناحيه تويه - دروار (جنوب باختري دامغان )

Sequence stratigraphy of the shaly and Top quartzite units of the Lalun Formation in Tuyeh-Darvar area (southwest of Damghan)

The Shaly and Top Quartzite units of the Lalun Formation (Upper Lower Cambrian) have been studied in Tuyeh-Darvar area (48 kilometers southwest of Damghan) to determine their facies, sedimentary environments and sequence stratigraphy. These units arc unconformably underlain by the sandstone unit of the Lalun Formation. They arc unconformably overlain, with a paleosol horizon, by rocks of the Mila Formation. The Shaly and Top Quartzite units consist of carbonate, siliciclastic (mainly marine) and storm facies groups. These were deposited in a storm dominated mixed clastic-carbonate ramp/estuary of the northwest passive margin of Gondwana, following the first late Early Cambrian mass extinction. Two sequences with both type I and type 2 sequence boundaries are recognized within the Shaly and Top Quartzite units.