| Abstract: | The Dayizishan scoria cone and Jinlongdingzi scoria cone in the Longgang volcanic swarm, northeastern China are comprised of basaltic fallout tephra that derived from sub - Plinian eruptions. The airborn tephra formed a scoria cone and tephra sheets in geomorphological character. The fallout tephra deposits consist of basaltic scoria, bomb, ultramafic xenolith and lithic fragments. The tephra deposits in the tephra sheets developed plane parallel bedding and graded bedding. The size parameters of tephra changed with distance away from source and the lapse of time regularly.The Dalongwan tuff ring and Longquanlongwan tuff ring in Longgang volcanic swarm are comprised of base surge deposits, formed by phreatomagmatic explosions. The base surge deposits are composed of basaltic lapilli, pisolites and tuff.The sedimentary structure, for instance, dunelike structure, chute and pool structure, U - shaped channel and cross bedding, massive beds and sandwave beds etc. are recognized. |
