Devonian syringostromatid stromatoporoids from the Broken River region, North Queensland
Abstract
Six species of syringostromatid stromatoporoids are described from the biostratigraphically well-constrained carbonate successions of the Broken River region, North Queensland; the various occurrences range from earliest Devonian (early Lochkovian) to Mid-Devonian (late Eifelian). Included are three new Lochkovian species, Atopostroma stearni from the uppermost part of the Jack Formation and the Martins Well Limestone Member of the succeeding Shield Creek Formation, A. protentum and Habrostroma alternum also from the Martins Well Limestone Member. Transitional forms between the species of Atopostroma and Habrostroma are recorded from the Martins Well fauna. In addition Atopostroma distans (Ripper, 1937) is found in the Lomandra Limestone (late Emsian), and is present in reworked pebbles of the Dip Creek and the Chinaman Creek limestones of possible late Emsian-Eifelian. Sparse records of Columnostroma sp. in the Mid-Devonian (late Eifelian) Dosey Limestone, and reworked clasts of Parallelopora sp. in the Chinaman Creek Limestone, also occur. Characteristic structural elements of syringostromatid fauna are described including pachysteles, pachystromes and microlaminae, and microreticulate (acosmoreticular and clinoreticular) microstructures in the best preserved specimens. Also aspects of the evolutionary development of the fauna and the nature of the preservation of certain structural elements are discussed.
