Introduction
This paper will provide a detailed report about the field trip to Newport, Ohio, including data presentation and interpretation. This essay is organized into three parts; and the first one provides background information about the location and outcrop, the second describes the characteristics of the two types of stratigraphic sequences, and the third presents an explanation of the collected data. The purpose of this field trip was to examine the outcrop of the Conemaugh Group Cyclothemes.
The data presented in this paper will match the description of the environments provided below. Background information that gives context to this field trip and the particular area examined will be provided below. The location in which the data collection took place is one mile west of Newport. More specifically, the outcrop that was studied is on the north side of State Route 7 near the Ohio River, Township 1 North, Range 6 West location. The stratigraphy is characterized by the geological age to which this outcrop belongs, which is the Pennsylvanian period. The name of the group to which the sediments belong is Conemaugh Group Cyclothems. Typically, two thin limestone layers are found in this group – marine limestones and deltaic shale. Two types of sediments were seen during the observation – shale and limestones. The first one is a fine-grained sedimentary, while the second one is a skeletal fragment of marine organisms. Conemaugh group includes the following environments – meandering river floodplains and delta sequences (Collins and Smith, 1977). The websites presented at the end of this essay were used to collect data about the meandering river point bar and progradational delta.
Thus, two environments typical for this formation are meandering river point bar and progradational delta, which are the types of stratigraphic sequences. The first one can be defined as one channel as opposed to braided rivers that can have several. The process of a meandering stream is a point bar deposition. Thus the pattern is a fining upward sequence, which is caused by progradation. The result of this process is fine sand and mud that develops in the area, as well as mudrocks, coal, and roots. The progradational delta is a combination of coastal and fluvial environments that are formed in places of connection between a river and sea, lake, or ocean. It is a coarsening upward sequence caused by progradation, which forms silt and sand.
Data
Reporting the data that was observed during the field trip is presented below. The list contains information about the layers and their characteristics, such as
In general, the outcrop in this area is part of both marine and non-marine sediments, while the first layer is the lowermost layer. The characteristics of two types of stratigraphic sequences meandering river point bar and progradational delta, can be observed within this data, which will be interpreted in the following section of the paper.
- Red, coral, plant fossils, sandstone cross-bedding.
- Black, coal, fossils, sandstone cross-bedding.
- Black, coal, black carbonate, sandstone cross-bedding.
- Grey, limestone, sandstone cross-bedding.
- Grey, fine sandstone, no fossils, sandstone cross-bedding.
- Grey, dark shale, fine sandstone, marine environment.
- Black, shale, no fossils, sandstone cross-bedding.
- Light grey, shale, silty shale, no fossils, sandstone cross-bedding.
- Grey, limestone, sandstone cross-bedding.
- Black, shale, lime shale, marine fossils, sandstone cross-bedding.
- Light grey, silty, shale, no fossils, sandstone cross-bedding.
- Black, sandstone cross-bedding, no fossils, marine environment.
Data Interpretation
The repetition of strata or rock types was observed during this field trip; more specifically, sandstone and shale were found in several layers. The stratigraphic sequence model most similar to the observed one is the meandering river sequence. Segments 1, 2, and three, as well as 5, are part of the regression, while layers 4,6, and 7 are part of transgression. The observation provides an understanding of the fact that the observed sequence is consistent with the point bar meandering river environments.
Prograding delta sequence characteristics that contrast with this data are the formation of thick deposits that are prevalent to this type. Additionally, in most cases, deposits from this sequence are shallow marine or fluvial, while the sediments are fine. Within the prograding deltas, the succession of deposits from silty to sandy can be observed. Progradational Delta Stratigraphic Sequences are also referred to as basinward building. The process of progradation is dependant on both the supply of sediment and the depth of water in the river. Large-scale sedimentary structures can typically be found in these areas. Additionally, channel sands, mouth bar sands, prodelta muds, and marine shelf deposits can be examined in Progradational Deltas, which contrasts with the findings of this field trip.
The meandering river point bar is developed through epsilon cross-stratification (ECS). Three initial deposits can be found in such environments – fluvial sandy, low-energy fluvial and microbially-influenced, and mesotidally influenced point bar facies. In general, clays with mud cracks, root traces can be found in such environments. Additionally, cross-bed send are standard for meandering river point bar, which is consistent with data presented in the previous section of this paper. Thus, the stratigraphic units analyzed in this paper are – meandering river point bar and progradational delta. This channel winds throughout the floodplain and places sedimental on the inside of the river’s curve. In general, due to the nature of this process, fine-grain materials can usually be found in these river systems.
Cyclothem can be defined as cycles of sediments characterized by the repetition of marine and non-marine elements. These complex structures indicate the cyclicity of deposition in a specific area. In some cases, coal can be found as part of this sequence, which is demonstrated in this analysis. It is caused by the regression and transgression process in the marine basin. In conclusion, the collected data indicates at least two full types of cyclothem cycles, including limestone and shale and limestone and fine sands. It is due to the fact that throughout time the process of formation of different types of rocks in the area altered.
More specifically, the basin was filled with sediments from the Appalachian Mountains. The glaciation of the South Pole raised the sea level, which affected the flat coastal river plain. The transgression caused the deposit of marine limestone, shale, and sandstone, while the transgression resulted in floodplain shales, peat, and terrestrial sands depositing into the swamp. The climate in the observed area during the Carboniferous period was warm and humid. Additionally, in this timeframe, the formation of glaciers occurred in the poles, which affected the climate. Thus, the cyclicity observed was caused by the change of weather conditions in the region.
Work Cited
Collins, H.R., and Smith, B.E., 1977, Geology and Mineral Resources of Washington County, Ohio: Ohio Department of Natural Resources Division of Geological Survey, Bulletin 66, 134 p.