Esacanaba Trough

Central Hill Area


Of the eight lithologic units identified in the reference hole (see Site 1037B below), only Units 2, 3, and 8 can be identified with any degree of certainty at Site 1038. Using grain size and magnetic susceptibility data, a correlation can be made between the upper 100 m of cores in Holes 1038A, 1038B, 1038G, 1038I, and the reference hole (Hole 1037B); below 100 mbsf stratigraphic correlation become more tenuous. In Hole 1038I, there is a strong correlation between MST signature and other physical property measurements in the upper 80 m of the hole. MST data proved to be a valuable tool in establishing correlations between cores recovered from Site 1038 and the reference hole at Site 1037, but some correlations are tenuous and require confirmation from shorebased analyses.

Near surface sands lack lateral continuity, suggesting that they may have been locally derived, perhaps by slumping off the steep fault scarps that surround the basin. Unit 3, defined in the reference hole, is characterized by thicker, more sand-rich turbidites separated by relatively thinner mudstone intervals, and can be correlated with sands recovered at Site 1038. The top of this interval is identified in all holes that penetrated to a depth in excess of 80 mbsf. This unit is interpreted to be correlative to the top of the regionally developed transparent seismic layer. Despite the fact that there is 40 m of relief between Holes 1038B and 1038I, the top of Unit 3 occurs within 6.1 m in all the holes, which implies that the topographic expression of Central Hill is very young.

Due to poor recovery Units 4, 5, and 6 are not easily identified at Site 1038. Correlation of the lower section of sediment drilled at Hole 1038I with Unit 6 in the reference hole based on similarities in the physical properties requires rapid thickening of strata above Unit 6 to account for changes in sediment thickness between these two sites, which are separated by about 5 km. If the top of Unit 8 in Hole 1038I is instead accepted as the first occurrence of stacked siltstone turbidites with no obvious hemipelagic intervals, then the sediment thicknesses are more readily correlated, but the sandy intervals derived from the Klamath Mountains, initially identified in DSDP Hole 35 and assigned to Unit 8 at Site 1038, appear to have not been recovered.

To 169 Central Hill Biostratigraphy, Petrology, and Geochemistry

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