Meadow Brook Through Valley

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The Meadow Brook Through Valley is an east-northeast oriented valley used by the SEPTA West Trenton line between Jenkintown and Bethayres and links the south oriented Tacony Creek valley at Jenkintown with the deeper south oriented Pennypack Creek valley at Bethayres. Today south oriented Baederwood Creek flows into the the through valley’s west-southwest end and then turns to flow for approximately one-half mile in a west-southwest direction to join Tacony Creek at an elevation slightly greater than 200 feet. Between the west-southwest oriented Baederwood Creek segment and the SEPTA Noble station elevations rise to approximately 220 feet. No surface drainage is visible on the one mile long urbanized through valley floor between the SEPTA Noble station and the SEPTA Rydal station although today the through valley floor slopes gradually in an east-northeast direction to near the Rydal station where surface drainage becomes visible in the form of east-northeast oriented Meadow Brook, which flows for approximately two miles to join Pennypack Creek (which crosses the SEPTA West Trenton line just a short distance west of the SEPTA Bethayres station) at an elevation of about 140 feet.

The through valley continues in an east-northeast direction from Pennypack Creek to Neshaminy Creek and possibly further and is used by the SEPTA West Trenton line from the Bethayres station to at least the Neshaminy Falls station. The straightness of this through valley suggests it may have been eroded along a linear geologic feature such as a fault line (the Pennsylvania Geologic Survey web applications map shows a linear boundary between two metamorphic rock units, although the two rock units should be equally erosion resistant and form erosion resistant ridges on either side of the through valley).

The through valley floor between Tacony Creek and Pennypack Creek is about one-fourth mile wide and at least 100 feet deep when compared with immediately adjacent hills on either side (the valley width is greater than one-half mile at the 300-foot elevation level). About one mile to the north of the Meadow Brook Through Valley is the west-southwest to east-northeast Edge Hill Ridge, which has elevations exceeding 400 feet and has the same orientation as the Meadow Brook Through Valley. The Edge Hill Ridge orientation is probably determined by underlying bedrock units and suggests the Meadow Brook Through Valley orientation may be related to the Edge Hill Ridge orientation and may also be related to the underlying geology, although the through valley was eroded by significant volumes of water flowing from one end of the valley to the other.

Based on present day elevations there is a temptation to suggest water flowed from the Tacony Creek drainage basin to the Peenypack Creek drainage basin. However such an interpretation requires that east-northeast flow would have joined south oriented Pennypack Creek as a barbed tributary. Valley orientations suggest west-southwest oriented flow moving from east of the present day Pennypack Creek drainage basin to the Tacony Creek drainage basin was responsible for eroding the Meadow Brook Through Valley. If so, at the time water was eroding the Meadow Brook Through Valley and flowing to what was a newly eroded south oriented Tacony Creek valley the through valley floor elevation at Bethayres would have been greater than 220 feet. Headward erosion of the much deeper south oriented Pennypack Creek valley then captured the west-southwest oriented flow and beheaded the Meadow Brook Through Valley. Water on the east-northeast end of the beheaded Meadow Brook Through Valley then reversed flow direction to create present day east-northeast oriented Meadow Brook Creek.

At the time west-southwest flow ended the valley floor probably sloped gently in a west-southwest direction. The question then might be asked, how was a west-southwest oriented valley floor eroded to create an east-northeast slope from Noble to Bethayres and a west-southwest slope from west of Noble to Jenkintown? While it is possible these slopes developed over long periods of time with water moving to the deeper Pennypack Creek valley having an advantage over water moving to the less deep Tacony Creek valley such a hypothesis seems unlikely because it does not explain how the deep Pennypack Creek valley eroded further to the north. A much more likely explanation is following the Pennypack Creek valley capture there was a period of time when large volumes of west-southwest or southwest oriented water still moved across regions to the north of the actively eroding Pennypack Creek valley head (and north of the beheaded Meadow Brook Through Valley). Some of this yet to be captured flow was apparently able to spill over into the newly beheaded Meadow Brook Through Valley and supplied the water volumes required to erode the present day Baederwood Creek and Meadow Brook Creek valleys. The south oriented Baederwood Creek headwaters and a south oriented Meadow Brook tributary flowing from the present day Penn State University Ogontz Campus in a south direction to enter the Meadow Brook Through Valley provide evidence supporting this interpretation. In addition numerous other landforms described in this Philadelphia area landform catalog suggest massive southwest oriented floods crossed the region at the time most present day landforms were eroded.

Figure 1: Meadow Brook Through Valley.

Figure 1: .Location 1 (near map center) is in the Meadow Brook Through Valley near the SEPTA Rydal station. Location 2 (near map west edge) is near the through valley west-southwest end just north of the SEPTA Jenkintown station. Location 3 (near map east edge) is at the through valley east-northeast end where Meadow Brook joins south oriented Pennypack Creek and is just west of the SEPTA Bethayres station (not seen). United States Geological Survey map digitally presented using National Geographic TOPO software. 

 

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