limestone, chert, or limestone? [2013225_fieldtrip]

Limestone, Chert, or Limestone?

ByThomas Liner

The Mystery Rock

Zero Mountain Outcrop #1

Zero Mountain Outcrop #2

Hammer Time [HT]

Beav-O-Rama [BR]

Northern Section [NBR]

• Interbedded Chert & Limestone

• Tripolitic chert prominent in the form of one large bed

Middle Section [MBR]

• Interbeded Limestone & Chert

• Penecontemporaneous Chert & Tripolitic Chert

Southern Section [SBR]

• Massive Limestone

• Chert becomes less prominent

• ~100 yds South of [MBR]

Southern Face

• Inter-bedded things!

• Interbedded Chert and Crinoid beds.

• Crinoid beds exhibit upward thinning

• Transgressions or Turbidity Flows?

Graded Crinoid Bed

• Thins Upward

• TOP= Fine-Grained Bryzoan Packstone

• BOTTOM= Coarse Crinoidal Grainstone

What does it mean?• "The Boone Formation appears to be cyclic in some

areas throughout most of its lower interval."

• "They may represent turbidity flows in which shallower water sediment is periodically brought into the deeper water setting."

• "These cycles may also be related to fluctuations in early Mississippian shoreline where the orientation changed frequently in areas."

• Source: Proceedings Arkansas Academy of Science, Vol. XXXX, 1986

Western Face [BRW]

Conglomerate?