Abstract
The Albion Formation, which is located in the southeastern region of the Yucatan Peninsula, is identified as the outer portion of the continuous ejecta blanket of the Chicxulub crater. Three locations where Albion Formation is preserved are 1) the Quintana Roo to Ramonal region along the eastern border of Mexico, 2) the Albion region of northwestern Belize and 3) the Armenia region of central Belize. They are situated 330˜350 km, 370 km and 470 km from the Chicxulub crater respectively. In this paper, I review the recent works on the Albion Formation and discuss the ejecta from the Chixulub crater based on my own field work.
The Albion Formation, which is preserved on the uppermost Cretaceous shallow dolomite sequence, forms two sequences: spheroid and diamictite beds. The spheroid bed consists of dolomite and clay spheroids and smectite clay fragments, within a fine carbonate matrix. The dolomite spheroid is formed by dolomite fragments surrounded by fine calcite crystal, which are melted to the host rock. The clay spheroid and clay fragments are identified as an altered impact glass. Sedimentary structures indicate a high flow regime with a paleocurrent NNW to SSE trend, indicating the flow coming from the Chicxulub crater. The diamictite bed is characterized by accreted boulder-size dolomite blocks and a coarse-grained calcareous matrix containing altered glass, striated, polished cobbles, and shocked quartz. The boulder-size dolomite blocks are formed by accreted calcite crystal layers, which are identified as fall deposits within a highly concentrated vapor cloud of carbonate formed after passing of the ejecta blanket.
These stratigraphic characteristics of the Albion Formation indicate that the formation is formed by impact-related ballistic sedimentation from the Chicxulub crater. The ejecta bed and accreted block sequences provide the key evidence in recognizing the flow conditions and ejecta transport mechanism at peripheral sites from the giant impact crater.
