Cretaceous planktonic foraminifera and calpionellids from the Gulf of Mexico
Drilling on Leg 77 resulted in eight single-bit holes at five sites extending across the Yucatan Channel in the southeastern Gulf of Mexico. Sites 535, 539 (aborted hole of 7.5 m depth), and 540 were grouped as basin sites, whereas location on up-faulted blocks at Sites 536, 537, and 538 led to thei...
| Main Authors: | , |
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| Format: | Dataset |
| Language: | English |
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PANGAEA
1984
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| Subjects: | |
| Online Access: | https://doi.pangaea.de/10.1594/PANGAEA.816803 https://doi.org/10.1594/PANGAEA.816803 |
| Summary: | Drilling on Leg 77 resulted in eight single-bit holes at five sites extending across the Yucatan Channel in the southeastern Gulf of Mexico. Sites 535, 539 (aborted hole of 7.5 m depth), and 540 were grouped as basin sites, whereas location on up-faulted blocks at Sites 536, 537, and 538 led to their grouping as basement sites. The sedimentary record encountered across the Channel is short, intermittent, and laterally erratic, reflecting both the general instability of sedimentation and the depositional contrast between basin and basement sites. The combined record for the Cenozoic is incomplete, and that for most of the Upper Cretaceous is missing. The Lower Cretaceous record is relatively long at basin sites, including apparent Berriasian at Site 535, but the record is still discontinuous and the biostratigraphic data are sparse, frequently contradictory, and complicated by displacement and reworking. The Lower Cretaceous record is again short and erratic at the basement Sites 536, 537, and 538, where displaced shelf grainstones, with very poor recovery, and variably minor interbedded lime mudstones and marls lie on continental basement. Cenozoic cores are mostly pelagic calcareous oozes, except at Site 535, where more than 150 m of upper Pleistocene distal fan and deltaic mudstones were drilled. The Cenozoic successions are thin, fragmentary, and variable laterally, except for the Oligocene, which is well developed in basin Hole 540 and basement Hole 538A. Planktonic foraminifers are typically abundant and well preserved, but reworking is persistent. No Cenozoic except Pleistocene was encountered at basin Site 535. The Cretaceous/Tertiary boundary was recovered in Hole 536, where a complete foraminiferal zonal sequence of the lowermost Paleocene overlies ill-defined Maestrichtian without perceptible lithic change. The Maestrichtian through Turanian interval is represented by only a few meters at Sites 540, 536, 537, and 538, and ranges from upper Maestrichtian to Santonian. Nannofossil-foraminiferal chalk is ... |
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