ABSTRACT

Cretaceous and Tertiary rocks were dredged along the Florida Escarpment at five areas south of 27 °05N in late 1982 during cruise LY-82A of USNS LYNCH. The escarpment was sampled from near the base (as deep as 3300 meters) to near the top (as shallow as 1500 meters) of the slope. The majority of samples recovered are middle Cretaceous peritidal and lagoonal limestones and dolomites deposited under restricted, low-energy conditions. Presumed middle Cretaceous dolomites deposited in hypersaline bank-interior environments were taken primarily from the walls of canyons incised from 10 to 50 kilometers into the escarpment, and also from the escarpment proper at several dredge stations. Limestone lithologies are generally bioturbated miliolid and mollusk wackestone/packstone (lagoonal) and fenestral and algallaminated mudstone/wackestone (peritidal). Some dolomites retain primary sedimentary structures (e.g., mottling and algallamination), while others appear structureless, perhaps due to recrystallization. Few of the middle Cretaceous samples were deposited under high-energy conditions. Those that are high-energy deposits are bioclastic rudstones and coral boundstones. Late Cretaceous and Tertiary deep-water limestones and chalks unconformably overlie and drape the older shallow-water carbonates. The limestones are Late Cretaceous in age, while the chalks range from the Late Cretaceous through the Pleistocene. The limited occurrence of high-energy facies rocks indicates that the escarpment has been eroded bankward over its entire length south of 27 °05N, and not just at canyon reentrants. The younger deep-water rocks reflect the drowning of the middle Cretaceous platform in Late Cretaceous time. The facies change from limestone to dolomite is attributed to higher salinities in the bank interior during the middle Cretaceous.